The document describes the experimental methods used to synthesize and characterize hybrid fibrous red P@TiO2 and black P@TiO2 nanotube membrane materials for photoelectrocatalytic water splitting. TiO2 nanotube membranes were fabricated by anodization and then phosphorus allotropes were deposited via chemical vapor deposition. Characterization techniques included powder XRD, SEM/EDS, STEM/EDS, Raman spectroscopy, XPS, UPS, UV-Vis spectroscopy, KPFM, and gas chromatography to confirm the formation and properties of the hybrid materials. Structural analysis by XRD and Raman spectroscopy validated the incorporation of crystalline red and black phosphorus phases within the TiO2 nanotube membranes.
Vapor growth of binary and ternary phosphorus-based semiconductors into TiO2 ...Pawan Kumar
We report successful synthesis of low band gap inorganic polyphosphide and TiO2 heterostructures with the aid of short-way transport reactions. Binary and ternary polyphosphides (NaP7, SnIP, and (CuI)3P12) were successfully reacted and deposited into electrochemically fabricated TiO2 nanotubes. Employing vapor phase reaction deposition, the cavities of 100 μm long TiO2 nanotubes were infiltrated; approximately 50% of the nanotube arrays were estimated to be infiltrated in the case of NaP7. Intensive characterization of the hybrid materials with techniques including SEM, FIB, HR-TEM, Raman spectroscopy, XRD, and XPS proved the successful vapor phase deposition and synthesis of the substances on and inside the nanotubes. The polyphosphide@TiO2 hybrids exhibited superior water splitting performance compared to pristine materials and were found to be more active at higher wavelengths. SnIP@TiO2 emerged to be the most active among the polyphosphide@TiO2 materials. The improved photocatalytic performance might be due to Fermi level re-alignment and a lower charge transfer resistance which facilitated better charge separation from inorganic phosphides to TiO2.
Mixed-Valence Single-Atom Catalyst Derived from Functionalized GraphenePawan Kumar
Single-atom catalysts (SACs) aim at bridging the gap between homogeneous and heterogeneous catalysis. The challenge is the development of materials with ligands enabling coordination of metal atoms in different valence states, and preventing leaching or nanoparticle formation. Graphene functionalized with nitrile groups (cyanographene) is herein employed for the robust coordination of Cu(II) ions, which are partially reduced to Cu(I) due to graphene-induced charge transfer. Inspired by nature's selection of Cu(I) in enzymes for oxygen activation, this 2D mixed-valence SAC performs flawlessly in two O2-mediated reactions: the oxidative coupling of amines and the oxidation of benzylic CH bonds toward high-value pharmaceutical synthons. High conversions (up to 98%), selectivities (up to 99%), and recyclability are attained with very low metal loadings in the reaction. The synergistic effect of Cu(II) and Cu(I) is the essential part in the reaction mechanism. The developed strategy opens the door to a broad portfolio of other SACs via their coordination to various functional groups of graphene, as demonstrated by successful entrapment of FeIII/FeII single atoms to carboxy-graphene.
Visible light assisted photocatalytic reduction of CO2 using a graphene oxide...Pawan Kumar
A new heteroleptic ruthenium complex containing 2-thiophenyl benzimidazole ligands was synthesized using a microwave technique and was immobilized to graphene oxide via covalent attachment. The synthesized catalyst was used for the photoreduction of carbon dioxide under visible light irradiation without using a sacrificial agent, which gave 2050 μmol g−1 cat methanol after 24 h of irradiation
C3N5: A Low Bandgap Semiconductor Containing an Azo-linked Carbon Nitride Fra...Pawan Kumar
Modification of carbon nitride based polymeric 2D materials for tailoring their optical, electronic and chemical properties for various applications has gained significant interest. The present report demonstrates the synthesis of a novel modified carbon nitride framework with a remarkable 3:5 C:N stoichiometry (C3N5) and an electronic bandgap of 1.76 eV, by thermal deammoniation of the melem hydrazine precursor. Characterization revealed that in the C3N5 polymer, two s-heptazine units are bridged together with azo linkage, which constitutes an entirely new and different bonding fashion from g-C3N4 where three heptazine units are linked together with tertiary nitrogen. Extended conjugation due to overlap of azo nitrogens and increased electron density on heptazine nucleus due to the aromatic π network of heptazine units lead to an upward shift of the valence band maximum resulting in bandgap reduction down to 1.76 eV. XRD, He-ion imaging, HR-TEM, EELS, PL, fluorescence lifetime imaging, Raman, FTIR, TGA, KPFM, XPS, NMR and EPR clearly show that the properties of C3N5 are distinct from pristine carbon nitride (g-C3N4). When used as an electron transport layer (ETL) in MAPbBr3 based halide perovskite solar cells, C3N5 outperformed g-C3N4, in particular generating an open circuit photovoltage as high as 1.3 V, while C3N5 blended with MAxFA1–xPb(I0.85Br0.15)3 perovskite active layer achieved a photoconversion efficiency (PCE) up to 16.7%. C3N5 was also shown to be an effective visible light sensitizer for TiO2 photoanodes in photoelectrochemical water splitting. Because of its electron-rich character, the C3N5 material displayed instantaneous adsorption of methylene blue from aqueous solution reaching complete equilibrium within 10 min, which is significantly faster than pristine g-C3N4 and other carbon based materials. C3N5 coupled with plasmonic silver nanocubes promotes plasmon-exciton coinduced surface catalytic reactions reaching completion at much low laser intensity (1.0 mW) than g-C3N4, which showed sluggish performance even at high laser power (10.0 mW). The relatively narrow bandgap and 2D structure of C3N5 make it an interesting air-stable and temperature-resistant semiconductor for optoelectronic applications while its electron-rich character and intra sheet cavity make it an attractive supramolecular adsorbent for environmental applications.
Asymmetric Multipole Plasmon-Mediated Catalysis Shifts the Product Selectivit...Pawan Kumar
Cu/TiO2 is a well-known photocatalyst for the photocatalytic transformation of CO2 into methane. The formation of C2+ products such as ethane and ethanol rather than methane is more interesting due to their higher energy density and economic value, but the formation of C–C bonds is currently a major challenge in CO2 photoreduction. In this context, we report the dominant formation of a C2 product, namely, ethane, from the gas-phase photoreduction of CO2 using TiO2 nanotube arrays (TNTAs) decorated with large-sized (80–200 nm) Ag and Cu nanoparticles without the use of a sacrificial agent or hole scavenger. Isotope-labeled mass spectrometry was used to verify the origin and identity of the reaction products. Under 2 h AM1.5G 1-sun illumination, the total rate of hydrocarbon production (methane + ethane) was highest for AgCu-TNTA with a total CxH2x+2 rate of 23.88 μmol g–1 h–1. Under identical conditions, the CxH2x+2 production rates for Ag-TNTA and Cu-TNTA were 6.54 and 1.39 μmol g–1 h–1, respectively. The ethane selectivity was the highest for AgCu-TNTA with 60.7%, while the ethane selectivity was found to be 15.9 and 10% for the Ag-TNTA and Cu-TNTA, respectively. Adjacent adsorption sites in our photocatalyst develop an asymmetric charge distribution due to quadrupole resonances in large metal nanoparticles and multipole resonances in Ag–Cu heterodimers. Such an asymmetric charge distribution decreases adsorbate–adsorbate repulsion and facilitates C–C coupling of reaction intermediates, which otherwise occurs poorly in TNTAs decorated with small metal nanoparticles.
Noble Metal Free, Visible Light Driven Photocatalysis Using TiO2 Nanotube Arr...Pawan Kumar
Bulk g-C3N4 is an earth-abundant, easily synthesizable, and exceptionally stable photocatalyst with an electronic bandgap of 2.7 eV. Herein, the concepts of P-doping and size quantization are combined to synthesize highly fluorescent P-doped carbon nitride quantum dots (CNPQDs) with a bandgap of 2.1 eV. CNPQDs are hosted on anatase-phase and rutile-phase TiO2 nanotube array scaffolds, and examined as photoanodes for sunlight-driven water-splitting and as photocatalysts for surface catalytic reactions. Square-shaped rutile phase TiO2 nanotube arrays (STNAs) decorated with CNPQDs (CNPQD-STNA) generate 2.54 mA cm−2 photocurrent under AM1.5 G simulated sunlight. A champion hydrogen evolution rate of 22 µmol h−1 corresponds to a Faradaic efficiency of 93.2%. In conjunction with Ag nanoparticles (NPs), the CNPQD-STNA hybrid is also found to be an excellent plexcitonic photocatalyst for the visible light-driven transformation of 4-nitrobenzenethiol (4-NBT) to dimercaptoazobenzene (DMAB), producing reaction completion at a laser power of 1 mW (532 nm) while Ag NP/TNA and Ag NP/STNA photocatalysts cannot complete this transformation even at 10 mW laser power. The results point the way forward for photochemically robust, noble metal free, visible light harvesting photoacatalysts based on nanostructured heterojunctions of graphenic frameworks with TiO2.
Harvesting Hot Holes in Plasmon-Coupled Ultrathin Photoanodes for High-Perfor...Pawan Kumar
The harvesting of hot carriers produced by plasmon decay to generate electricity or drive a chemical reaction enables the reduction of the thermalization losses associated with supra-band gap photons in semiconductor photoelectrochemical (PEC) cells. Through the broadband harvesting of light, hot-carrier PEC devices also produce a sensitizing effect in heterojunctions with wide-band gap metal oxide semiconductors possessing good photostability and catalytic activity but poor absorption of visible wavelength photons. There are several reports of hot electrons in Au injected over the Schottky barrier into crystalline TiO2 and subsequently utilized to drive a chemical reaction but very few reports of hot hole harvesting. In this work, we demonstrate the efficient harvesting of hot holes in Au nanoparticles (Au NPs) covered with a thin layer of amorphous TiO2 (a-TiO2). Under AM1.5G 1 sun illumination, photoanodes consisting of a single layer of ∼50 nm diameter Au NPs coated with a 10 nm shell of a-TiO2 (Au@a-TiO2) generated 2.5 mA cm–2 of photocurrent in 1 M KOH under 0.6 V external bias, rising to 3.7 mA cm–2 in the presence of a hole scavenger (methanol). The quantum yield for hot-carrier-mediated photocurrent generation was estimated to be close to unity for high-energy photons (λ < 420 nm). Au@a-TiO2 photoelectrodes produced a small positive photocurrent of 0.1 mA cm–2 even at a bias of −0.6 V indicating extraction of hot holes even at a strong negative bias. These results together with density functional theory modeling and scanning Kelvin probe force microscope data indicate fast injection of hot holes from Au NPs into a-TiO2 and light harvesting performed near-exclusively by Au NPs. For comparison, Au NPs coated with a 10 nm shell of Al2O3 (Au@Al2O3) generated 0.02 mA cm–2 of photocurrent in 1 M KOH under 0.6 V external bias. These results underscore the critical role played by a-TiO2 in the extraction of holes in Au@a-TiO2 photoanodes, which is not replicated by an ordinary dielectric shell. It is also demonstrated here that an ultrathin photoanode (<100 nm in maximum thickness) can efficiently drive sunlight-driven water splitting.
Consistently High Voc Values in p-i-n Type Perovskite Solar Cells Using Ni3+-...Pawan Kumar
Leading edge p-i-n type halide perovskite solar cells (PSCs) severely underperform n-i-p PSCs. p-i-n type PSCs that use PEDOT:PSS hole transport layers (HTLs) struggle to generate open-circuit photovoltage values higher than 1 V. NiO HTLs have shown greater promise in achieving high Voc values albeit inconsistently. In this report, a NiO nanomesh with Ni3+ defect grown by the hydrothermal method was used to obtain PSCs with Voc values that consistently exceeded 1.10 V (champion Voc = 1.14 V). A champion device photoconversion efficiency of 17.75% was observed. Density functional theory modeling was used to understand the interfacial properties of the NiO/perovskite interface. The PCE of PSCs constructed using the Ni3+-doped NiO nanomesh HTL was ∼34% higher than that of conventional compact NiO-based perovskite solar cells. A suite of characterization techniques such as transmission electron microscopy, field emission scanning electron microscopy, intensity-modulated photocurrent spectroscopy, intensity-modulated photovoltage spectroscopy, time-resolved photoluminescence, steady-state photoluminescence, and Kelvin probe force microscopy provided evidence of better film quality, enhanced charge transfer, and suppressed charge recombination in PSCs based on hydrothermally grown NiO nanostructures.
Vapor growth of binary and ternary phosphorus-based semiconductors into TiO2 ...Pawan Kumar
We report successful synthesis of low band gap inorganic polyphosphide and TiO2 heterostructures with the aid of short-way transport reactions. Binary and ternary polyphosphides (NaP7, SnIP, and (CuI)3P12) were successfully reacted and deposited into electrochemically fabricated TiO2 nanotubes. Employing vapor phase reaction deposition, the cavities of 100 μm long TiO2 nanotubes were infiltrated; approximately 50% of the nanotube arrays were estimated to be infiltrated in the case of NaP7. Intensive characterization of the hybrid materials with techniques including SEM, FIB, HR-TEM, Raman spectroscopy, XRD, and XPS proved the successful vapor phase deposition and synthesis of the substances on and inside the nanotubes. The polyphosphide@TiO2 hybrids exhibited superior water splitting performance compared to pristine materials and were found to be more active at higher wavelengths. SnIP@TiO2 emerged to be the most active among the polyphosphide@TiO2 materials. The improved photocatalytic performance might be due to Fermi level re-alignment and a lower charge transfer resistance which facilitated better charge separation from inorganic phosphides to TiO2.
Mixed-Valence Single-Atom Catalyst Derived from Functionalized GraphenePawan Kumar
Single-atom catalysts (SACs) aim at bridging the gap between homogeneous and heterogeneous catalysis. The challenge is the development of materials with ligands enabling coordination of metal atoms in different valence states, and preventing leaching or nanoparticle formation. Graphene functionalized with nitrile groups (cyanographene) is herein employed for the robust coordination of Cu(II) ions, which are partially reduced to Cu(I) due to graphene-induced charge transfer. Inspired by nature's selection of Cu(I) in enzymes for oxygen activation, this 2D mixed-valence SAC performs flawlessly in two O2-mediated reactions: the oxidative coupling of amines and the oxidation of benzylic CH bonds toward high-value pharmaceutical synthons. High conversions (up to 98%), selectivities (up to 99%), and recyclability are attained with very low metal loadings in the reaction. The synergistic effect of Cu(II) and Cu(I) is the essential part in the reaction mechanism. The developed strategy opens the door to a broad portfolio of other SACs via their coordination to various functional groups of graphene, as demonstrated by successful entrapment of FeIII/FeII single atoms to carboxy-graphene.
Visible light assisted photocatalytic reduction of CO2 using a graphene oxide...Pawan Kumar
A new heteroleptic ruthenium complex containing 2-thiophenyl benzimidazole ligands was synthesized using a microwave technique and was immobilized to graphene oxide via covalent attachment. The synthesized catalyst was used for the photoreduction of carbon dioxide under visible light irradiation without using a sacrificial agent, which gave 2050 μmol g−1 cat methanol after 24 h of irradiation
C3N5: A Low Bandgap Semiconductor Containing an Azo-linked Carbon Nitride Fra...Pawan Kumar
Modification of carbon nitride based polymeric 2D materials for tailoring their optical, electronic and chemical properties for various applications has gained significant interest. The present report demonstrates the synthesis of a novel modified carbon nitride framework with a remarkable 3:5 C:N stoichiometry (C3N5) and an electronic bandgap of 1.76 eV, by thermal deammoniation of the melem hydrazine precursor. Characterization revealed that in the C3N5 polymer, two s-heptazine units are bridged together with azo linkage, which constitutes an entirely new and different bonding fashion from g-C3N4 where three heptazine units are linked together with tertiary nitrogen. Extended conjugation due to overlap of azo nitrogens and increased electron density on heptazine nucleus due to the aromatic π network of heptazine units lead to an upward shift of the valence band maximum resulting in bandgap reduction down to 1.76 eV. XRD, He-ion imaging, HR-TEM, EELS, PL, fluorescence lifetime imaging, Raman, FTIR, TGA, KPFM, XPS, NMR and EPR clearly show that the properties of C3N5 are distinct from pristine carbon nitride (g-C3N4). When used as an electron transport layer (ETL) in MAPbBr3 based halide perovskite solar cells, C3N5 outperformed g-C3N4, in particular generating an open circuit photovoltage as high as 1.3 V, while C3N5 blended with MAxFA1–xPb(I0.85Br0.15)3 perovskite active layer achieved a photoconversion efficiency (PCE) up to 16.7%. C3N5 was also shown to be an effective visible light sensitizer for TiO2 photoanodes in photoelectrochemical water splitting. Because of its electron-rich character, the C3N5 material displayed instantaneous adsorption of methylene blue from aqueous solution reaching complete equilibrium within 10 min, which is significantly faster than pristine g-C3N4 and other carbon based materials. C3N5 coupled with plasmonic silver nanocubes promotes plasmon-exciton coinduced surface catalytic reactions reaching completion at much low laser intensity (1.0 mW) than g-C3N4, which showed sluggish performance even at high laser power (10.0 mW). The relatively narrow bandgap and 2D structure of C3N5 make it an interesting air-stable and temperature-resistant semiconductor for optoelectronic applications while its electron-rich character and intra sheet cavity make it an attractive supramolecular adsorbent for environmental applications.
Asymmetric Multipole Plasmon-Mediated Catalysis Shifts the Product Selectivit...Pawan Kumar
Cu/TiO2 is a well-known photocatalyst for the photocatalytic transformation of CO2 into methane. The formation of C2+ products such as ethane and ethanol rather than methane is more interesting due to their higher energy density and economic value, but the formation of C–C bonds is currently a major challenge in CO2 photoreduction. In this context, we report the dominant formation of a C2 product, namely, ethane, from the gas-phase photoreduction of CO2 using TiO2 nanotube arrays (TNTAs) decorated with large-sized (80–200 nm) Ag and Cu nanoparticles without the use of a sacrificial agent or hole scavenger. Isotope-labeled mass spectrometry was used to verify the origin and identity of the reaction products. Under 2 h AM1.5G 1-sun illumination, the total rate of hydrocarbon production (methane + ethane) was highest for AgCu-TNTA with a total CxH2x+2 rate of 23.88 μmol g–1 h–1. Under identical conditions, the CxH2x+2 production rates for Ag-TNTA and Cu-TNTA were 6.54 and 1.39 μmol g–1 h–1, respectively. The ethane selectivity was the highest for AgCu-TNTA with 60.7%, while the ethane selectivity was found to be 15.9 and 10% for the Ag-TNTA and Cu-TNTA, respectively. Adjacent adsorption sites in our photocatalyst develop an asymmetric charge distribution due to quadrupole resonances in large metal nanoparticles and multipole resonances in Ag–Cu heterodimers. Such an asymmetric charge distribution decreases adsorbate–adsorbate repulsion and facilitates C–C coupling of reaction intermediates, which otherwise occurs poorly in TNTAs decorated with small metal nanoparticles.
Noble Metal Free, Visible Light Driven Photocatalysis Using TiO2 Nanotube Arr...Pawan Kumar
Bulk g-C3N4 is an earth-abundant, easily synthesizable, and exceptionally stable photocatalyst with an electronic bandgap of 2.7 eV. Herein, the concepts of P-doping and size quantization are combined to synthesize highly fluorescent P-doped carbon nitride quantum dots (CNPQDs) with a bandgap of 2.1 eV. CNPQDs are hosted on anatase-phase and rutile-phase TiO2 nanotube array scaffolds, and examined as photoanodes for sunlight-driven water-splitting and as photocatalysts for surface catalytic reactions. Square-shaped rutile phase TiO2 nanotube arrays (STNAs) decorated with CNPQDs (CNPQD-STNA) generate 2.54 mA cm−2 photocurrent under AM1.5 G simulated sunlight. A champion hydrogen evolution rate of 22 µmol h−1 corresponds to a Faradaic efficiency of 93.2%. In conjunction with Ag nanoparticles (NPs), the CNPQD-STNA hybrid is also found to be an excellent plexcitonic photocatalyst for the visible light-driven transformation of 4-nitrobenzenethiol (4-NBT) to dimercaptoazobenzene (DMAB), producing reaction completion at a laser power of 1 mW (532 nm) while Ag NP/TNA and Ag NP/STNA photocatalysts cannot complete this transformation even at 10 mW laser power. The results point the way forward for photochemically robust, noble metal free, visible light harvesting photoacatalysts based on nanostructured heterojunctions of graphenic frameworks with TiO2.
Harvesting Hot Holes in Plasmon-Coupled Ultrathin Photoanodes for High-Perfor...Pawan Kumar
The harvesting of hot carriers produced by plasmon decay to generate electricity or drive a chemical reaction enables the reduction of the thermalization losses associated with supra-band gap photons in semiconductor photoelectrochemical (PEC) cells. Through the broadband harvesting of light, hot-carrier PEC devices also produce a sensitizing effect in heterojunctions with wide-band gap metal oxide semiconductors possessing good photostability and catalytic activity but poor absorption of visible wavelength photons. There are several reports of hot electrons in Au injected over the Schottky barrier into crystalline TiO2 and subsequently utilized to drive a chemical reaction but very few reports of hot hole harvesting. In this work, we demonstrate the efficient harvesting of hot holes in Au nanoparticles (Au NPs) covered with a thin layer of amorphous TiO2 (a-TiO2). Under AM1.5G 1 sun illumination, photoanodes consisting of a single layer of ∼50 nm diameter Au NPs coated with a 10 nm shell of a-TiO2 (Au@a-TiO2) generated 2.5 mA cm–2 of photocurrent in 1 M KOH under 0.6 V external bias, rising to 3.7 mA cm–2 in the presence of a hole scavenger (methanol). The quantum yield for hot-carrier-mediated photocurrent generation was estimated to be close to unity for high-energy photons (λ < 420 nm). Au@a-TiO2 photoelectrodes produced a small positive photocurrent of 0.1 mA cm–2 even at a bias of −0.6 V indicating extraction of hot holes even at a strong negative bias. These results together with density functional theory modeling and scanning Kelvin probe force microscope data indicate fast injection of hot holes from Au NPs into a-TiO2 and light harvesting performed near-exclusively by Au NPs. For comparison, Au NPs coated with a 10 nm shell of Al2O3 (Au@Al2O3) generated 0.02 mA cm–2 of photocurrent in 1 M KOH under 0.6 V external bias. These results underscore the critical role played by a-TiO2 in the extraction of holes in Au@a-TiO2 photoanodes, which is not replicated by an ordinary dielectric shell. It is also demonstrated here that an ultrathin photoanode (<100 nm in maximum thickness) can efficiently drive sunlight-driven water splitting.
Consistently High Voc Values in p-i-n Type Perovskite Solar Cells Using Ni3+-...Pawan Kumar
Leading edge p-i-n type halide perovskite solar cells (PSCs) severely underperform n-i-p PSCs. p-i-n type PSCs that use PEDOT:PSS hole transport layers (HTLs) struggle to generate open-circuit photovoltage values higher than 1 V. NiO HTLs have shown greater promise in achieving high Voc values albeit inconsistently. In this report, a NiO nanomesh with Ni3+ defect grown by the hydrothermal method was used to obtain PSCs with Voc values that consistently exceeded 1.10 V (champion Voc = 1.14 V). A champion device photoconversion efficiency of 17.75% was observed. Density functional theory modeling was used to understand the interfacial properties of the NiO/perovskite interface. The PCE of PSCs constructed using the Ni3+-doped NiO nanomesh HTL was ∼34% higher than that of conventional compact NiO-based perovskite solar cells. A suite of characterization techniques such as transmission electron microscopy, field emission scanning electron microscopy, intensity-modulated photocurrent spectroscopy, intensity-modulated photovoltage spectroscopy, time-resolved photoluminescence, steady-state photoluminescence, and Kelvin probe force microscopy provided evidence of better film quality, enhanced charge transfer, and suppressed charge recombination in PSCs based on hydrothermally grown NiO nanostructures.
Photocatalytic Mechanism Control and Study of Carrier Dynamics in CdS@C3N5 Co...Pawan Kumar
We present a potential solution to the problem of extraction of photogenerated holes from CdS nanocrystals and nanowires. The nanosheet form of C3N5 is a low-band-gap (Eg = 2.03 eV), azo-linked graphenic carbon nitride framework formed by the polymerization of melem hydrazine (MHP). C3N5 nanosheets were either wrapped around CdS nanorods (NRs) following the synthesis of pristine chalcogenide or intercalated among them by an in situ synthesis protocol to form two kinds of heterostructures, CdS-MHP and CdS-MHPINS, respectively. CdS-MHP improved the photocatalytic degradation rate of 4-nitrophenol by nearly an order of magnitude in comparison to bare CdS NRs. CdS-MHP also enhanced the sunlight-driven photocatalytic activity of bare CdS NWs for the decolorization of rhodamine B (RhB) by a remarkable 300% through the improved extraction and utilization of photogenerated holes due to surface passivation. More interestingly, CdS-MHP provided reaction pathway control over RhB degradation. In the absence of scavengers, CdS-MHP degraded RhB through the N-deethylation pathway. When either hole scavenger or electron scavenger was added to the RhB solution, the photocatalytic activity of CdS-MHP remained mostly unchanged, while the degradation mechanism shifted to the chromophore cleavage (cycloreversion) pathway. We investigated the optoelectronic properties of CdS-C3N5 heterojunctions using density functional theory (DFT) simulations, finite difference time domain (FDTD) simulations, time-resolved terahertz spectroscopy (TRTS), and photoconductivity measurements. TRTS indicated high carrier mobilities >450 cm2 V–1 s–1 and carrier relaxation times >60 ps for CdS-MHP, while CdS-MHPINS exhibited much lower mobilities <150 cm2 V–1 s–1 and short carrier relaxation times <20 ps. Hysteresis in the photoconductive J–V characteristics of CdS NWs disappeared in CdS-MHP, confirming surface passivation. Dispersion-corrected DFT simulations indicated a delocalized HOMO and a LUMO localized on C3N5 in CdS-MHP. C3N5, with its extended π-conjugation and low band gap, can function as a shuttle to extract carriers and excitons in nanostructured heterojunctions, and enhance performance in optoelectronic devices. Our results demonstrate how carrier dynamics in core–shell heterostructures can be manipulated to achieve control over the reaction mechanism in photocatalysis.
TiO2-HfN Radial Nano-Heterojunction: A Hot Carrier Photoanode for Sunlight-Dr...Pawan Kumar
The lack of active, stable, earth-abundant, and visible-light absorbing materials to replace
plasmonic noble metals is a critical obstacle for researchers in developing highly efficient and costeffective photocatalytic systems. Herein, a core–shell nanotube catalyst was fabricated consisting of
atomic layer deposited HfN shell and anodic TiO2 support layer with full-visible regime photoactivity
for photoelectrochemical water splitting. The HfN active layer has two unique characteristics: (1) a
large bandgap between optical and acoustic phonon modes (2) and no electronic bandgap, which
allows a large population of long life-time hot carriers, which are used to enhance the photoelectrochemical performance. The photocurrent density (≈2.5 mA·cm−2 at 1 V vs. Ag/AgCl) obtained in
this study under AM 1.5G 1 Sun illumination is unprecedented, as it is superior to most existing
plasmonic noble metal-decorated catalysts and surprisingly indicates a photocurrent response that
extends to 730 nm. The result demonstrates the far-reaching application potential of replacing active
HER/HOR noble metals such as Au, Ag, Pt, Pd, etc. with low-cost plasmonic ceramics.
Synthesis of flower-like magnetite nanoassembly: Application in the efficient...Pawan Kumar
A facile approach for the synthesis of magnetite microspheres with flower-like morphology is reported that proceeds via the reduction of iron (III) oxide under hydrogen atmosphere. The ensuing magnetic catalyst is well characterized by XRD, FE-SEM, TEM, N2 adsorption-desorption isotherm and Mössbauer spectroscopy and explored for a simple yetbut efficient transfer hydrogenation reduction of a variety of nitroarenes to respective anilines in good to excellent yields (up to 98%) employing hydrazine hydrate. . The catalyst could be easily separated at the end of reaction using an external magnet and can be recycled up to 10 times without any loss in catalytic activity.
This work studied the effect of applying pulse current
(ton=off=1s) on the electrodeposition of silver nanoparticles on
carbon sphere surface as a substrate. The electrolyte is made of 0.1
M KNO3, 0.1 M KCN and 0.01M AgNO3. The pH value has been
adjusted in the alkaline region of 9.1 with the help of K(NO3)
addition. Experiments were carried out at room temperature for
periods up to 12 minutes. The cell is fitted with a mechanical stirrer
to keep the electrolyte in a dynamic state. Product(s) was
characterized with the help of SEM and EDX and field emission.
Results obtained show that silver nanoparticles has successfully
electrodeposited under pulse current conditions with a particle size
of 100–400 nm after 2 minutes. Deposition takes place on certain
accessible sites of the carbon surface of the substrate forming a
monolayer of scattered silver nanoparticles. Formation of macro
particles with larger diameter and multilayer in thickness takes
place with continuous deposition of silver nanoparticles on the
formerly deposited silver. Pulse current helps management of the
monolayer deposition as compared to the steady DC application
with respect to particle diameter and number of layers.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
A ruthenium trinuclear polyazine complex was synthesized and subsequently immobilized through
complexation to a graphene oxide support containing phenanthroline ligands (GO-phen). The developed
photocatalyst was used for the photocatalytic reduction of CO2 to methanol, using a 20 watt white cold
LED flood light, in a dimethyl formamide–water mixture containing triethylamine as a reductive
quencher. After 48 h illumination, the yield of methanol was found to be 3977.57 5.60 mmol gcat
1.
The developed photocatalyst exhibited a higher photocatalytic activity than graphene oxide, which
provided a yield of 2201.40 8.76 mmol gcat
1. After the reaction, the catalyst was easily recovered and
reused for four subsequent runs without a significant loss of catalytic activity and no leaching of the
metal/ligand was detected during the reaction.
Growth and Characterization of Barium doped Potassium Hydrogen Phthalate Sing...IJERA Editor
The Non Linear Optical materials have acquired new significance with the advent of a large number of devices
utilizing solid state Laser sources. Potassium Hydrogen Phthalate one of the Non Linear Optical material having
superior non linear optical properties has been exploited for variety of application. In the present work, KHP
single crystals were grown by slow evaporation technique with Barium metal ion as a dopant. The grown
crystals were subjected to powder XRD analysis and the result shows that the Ba2+ ions does not alter the crystal
structure, but it enter into the crystal lattice of pure KHP. The optical transparency of the grown crystal was
studied by UV-Visible spectroscopy, the molecular structure was confirmed by FTIR analysis and its thermal
stability by TG/DTA analysis. The improved SHG efficiency of barium doped Potassium Hydrogen Phthalate
crystal could enhance the nonlinearity behaviour. In addition to this, the electrical parameter such as dielectric
constant was studied in detail.
Application of mixed colloidal magnetic fluid of single domain Fe3O4 and NiFe...IJERA Editor
Ferrofluids are stable suspensions of colloidal ferrimagnetic particles in suitable non – magnetic carrier liquids. They have attracted a lot of attention from scientists and engineers due to their many interesting properties and applications in various branches of engineering. The present work reports the performance of colloidal fluid of single domain nanoparticles of NiFe2O4 and Fe3O4. The thermal properties and its dynamics on magnetization as well as its effect on thermal conductivity on the colloidal fluid are studied here. Advantages of the increased thermal conductivity and optimization of magnetization of mixed colloidal fluid is used to extract the heat from voice coil. Nanoparticles of 21 nm of Fe3O4 and 12 nm of NiFe2O4 are used for mixed colloidal fluid. The suspension of particles is achieved by coating the nanoparticles with mono-corboxylic group on both the types of particles. The higher size (21 nm of Fe3O4 and 12 nm of NiFe2O4) particles are taken for synthesizing colloidal fluid, to have magnetic property of mixed colloidal liquid at elevated temperature of voice coil of speaker (Higher sized particles gives better magnetization). Oil is used as a carrier. Mixed magnetic colloidal fluid is used as a medium for damping so that noise is reduced at higher temperature of voice coil
Characterization of different dopants in TiO2 Structure by Pulsed Laser Dep...sarmad
Characterization of different dopants in TiO2 Structure by Pulsed Laser Deposition
A thesis submitted By: Khaled Z.Yahya
Supervised by: Prof.Dr. Adawiya J.Haider Prof.Dr. Raad M.S.Al-Haddad
IOSR Journal of Applied Physics (IOSR-JAP) is an open access international journal that provides rapid publication (within a month) of articles in all areas of physics and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in applied physics. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Synthesis & Characterization of Fluorescent Silver Nanoparticles stabilized b...IJERA Editor
Synthesis of silver nanoparticles (Ag-NPs) was achieved by a simple green procedure using Tinospora Cordifolia leaf extract as stabilizer/reducing agents. Ag-NPs in the size range of 2–19 nm is obtained by the treatment of aqueous silver ions with leaf extracts of Tinospora Cordifolia. This eco-friendly approach is simple, amenable for large scale commercial production and technical applications. Further, photoluminiscence studies of these Ag-NPs were recorded & suggested that the present particles were suitable for fluorescence emitting probes. These red emitting Ag-NPs exhibited distinct fluorescence properties (both emission and stokeshift).
Annealing and Microstructural Characterization of Tin-Oxide Based Thick Film ...Anis Rahman
Abstract. The sheet resistance of tin oxide based thick-film resistors exhibits two regions of temperature dependence,
described by hopping (23°C-200°C) and diffusion mechanisms (200°C-350°C), respectively.
Annealing these samples causes the sheet resistance to increase in both regions. In the post-annealed samples,
the hopping conduction range is extended by 50°C (23°C-250°C) while the hopping parameter, To, is decreased by
more than 50%. The activation energy of diffusion (0.60 eV) is the same for both pre- and post annealed samples, but
the magnitude of resistance in the diffusion controlled region is increased significantly as a result of annealing. These
changes are explained in terms of a net decrease in the concentration of tin ions in the glass matrix. From a careful
microstructural study it was found that a conduction path composed of tin-oxide grains or their clusters in contact
with each other does not exist in the present system. HREM micrographs showed the presence of nanocrystalline
tin-oxide particles in the glass phase separating the tin-oxide grain clusters. Estimated average separation between
the nanocrystals in 4 nm, consistent with a variable-range hopping conduction via the dissolved tin ions in the glass
matrix.
Transparent and Conducting TiO2 : Nb Thin Films Prepared by Spray Pyrolysis T...arj_online
To date, only sputtering and pulsed laser deposition (PLD) techniques have been employed
successfully to fabricate highly conducting and transparent TiO2:Nb (TNO) films. In this article, we demonstrate
that transparent and conducting
TiO2
: Nb
films can be made by the spray pyrolysis technique. The films were
deposited on Corning 7059 glass substrates at 500
15˚C using an alcoholic precursor solution consisting of
titanium (iv) isopropoxide and
NbCl5
. The influence of increasing
Nb
concentration on the electrical, optical
and structural properties was investigated. The minimum resistivity, 3.36
-3 10
Ω cm, for
Ti1-xNbxO2
film (x
= 0.15) was obtained after 1 hour post deposition annealing in hydrogen atmosphere at 500˚C. The x-ray
diffraction of hydrogen annealed films showed a polycrystalline anatase (004)-oriented phase without any second
phases. The optical band gap for undoped and doped films lay in the range 3.38 – 3.47 eV. Using dispersion
analysis, optical constants were determined from spectro-photometric measurements for films on glass.
Photocatalytic Mechanism Control and Study of Carrier Dynamics in CdS@C3N5 Co...Pawan Kumar
We present a potential solution to the problem of extraction of photogenerated holes from CdS nanocrystals and nanowires. The nanosheet form of C3N5 is a low-band-gap (Eg = 2.03 eV), azo-linked graphenic carbon nitride framework formed by the polymerization of melem hydrazine (MHP). C3N5 nanosheets were either wrapped around CdS nanorods (NRs) following the synthesis of pristine chalcogenide or intercalated among them by an in situ synthesis protocol to form two kinds of heterostructures, CdS-MHP and CdS-MHPINS, respectively. CdS-MHP improved the photocatalytic degradation rate of 4-nitrophenol by nearly an order of magnitude in comparison to bare CdS NRs. CdS-MHP also enhanced the sunlight-driven photocatalytic activity of bare CdS NWs for the decolorization of rhodamine B (RhB) by a remarkable 300% through the improved extraction and utilization of photogenerated holes due to surface passivation. More interestingly, CdS-MHP provided reaction pathway control over RhB degradation. In the absence of scavengers, CdS-MHP degraded RhB through the N-deethylation pathway. When either hole scavenger or electron scavenger was added to the RhB solution, the photocatalytic activity of CdS-MHP remained mostly unchanged, while the degradation mechanism shifted to the chromophore cleavage (cycloreversion) pathway. We investigated the optoelectronic properties of CdS-C3N5 heterojunctions using density functional theory (DFT) simulations, finite difference time domain (FDTD) simulations, time-resolved terahertz spectroscopy (TRTS), and photoconductivity measurements. TRTS indicated high carrier mobilities >450 cm2 V–1 s–1 and carrier relaxation times >60 ps for CdS-MHP, while CdS-MHPINS exhibited much lower mobilities <150 cm2 V–1 s–1 and short carrier relaxation times <20 ps. Hysteresis in the photoconductive J–V characteristics of CdS NWs disappeared in CdS-MHP, confirming surface passivation. Dispersion-corrected DFT simulations indicated a delocalized HOMO and a LUMO localized on C3N5 in CdS-MHP. C3N5, with its extended π-conjugation and low band gap, can function as a shuttle to extract carriers and excitons in nanostructured heterojunctions, and enhance performance in optoelectronic devices. Our results demonstrate how carrier dynamics in core–shell heterostructures can be manipulated to achieve control over the reaction mechanism in photocatalysis.
TiO2-HfN Radial Nano-Heterojunction: A Hot Carrier Photoanode for Sunlight-Dr...Pawan Kumar
The lack of active, stable, earth-abundant, and visible-light absorbing materials to replace
plasmonic noble metals is a critical obstacle for researchers in developing highly efficient and costeffective photocatalytic systems. Herein, a core–shell nanotube catalyst was fabricated consisting of
atomic layer deposited HfN shell and anodic TiO2 support layer with full-visible regime photoactivity
for photoelectrochemical water splitting. The HfN active layer has two unique characteristics: (1) a
large bandgap between optical and acoustic phonon modes (2) and no electronic bandgap, which
allows a large population of long life-time hot carriers, which are used to enhance the photoelectrochemical performance. The photocurrent density (≈2.5 mA·cm−2 at 1 V vs. Ag/AgCl) obtained in
this study under AM 1.5G 1 Sun illumination is unprecedented, as it is superior to most existing
plasmonic noble metal-decorated catalysts and surprisingly indicates a photocurrent response that
extends to 730 nm. The result demonstrates the far-reaching application potential of replacing active
HER/HOR noble metals such as Au, Ag, Pt, Pd, etc. with low-cost plasmonic ceramics.
Synthesis of flower-like magnetite nanoassembly: Application in the efficient...Pawan Kumar
A facile approach for the synthesis of magnetite microspheres with flower-like morphology is reported that proceeds via the reduction of iron (III) oxide under hydrogen atmosphere. The ensuing magnetic catalyst is well characterized by XRD, FE-SEM, TEM, N2 adsorption-desorption isotherm and Mössbauer spectroscopy and explored for a simple yetbut efficient transfer hydrogenation reduction of a variety of nitroarenes to respective anilines in good to excellent yields (up to 98%) employing hydrazine hydrate. . The catalyst could be easily separated at the end of reaction using an external magnet and can be recycled up to 10 times without any loss in catalytic activity.
This work studied the effect of applying pulse current
(ton=off=1s) on the electrodeposition of silver nanoparticles on
carbon sphere surface as a substrate. The electrolyte is made of 0.1
M KNO3, 0.1 M KCN and 0.01M AgNO3. The pH value has been
adjusted in the alkaline region of 9.1 with the help of K(NO3)
addition. Experiments were carried out at room temperature for
periods up to 12 minutes. The cell is fitted with a mechanical stirrer
to keep the electrolyte in a dynamic state. Product(s) was
characterized with the help of SEM and EDX and field emission.
Results obtained show that silver nanoparticles has successfully
electrodeposited under pulse current conditions with a particle size
of 100–400 nm after 2 minutes. Deposition takes place on certain
accessible sites of the carbon surface of the substrate forming a
monolayer of scattered silver nanoparticles. Formation of macro
particles with larger diameter and multilayer in thickness takes
place with continuous deposition of silver nanoparticles on the
formerly deposited silver. Pulse current helps management of the
monolayer deposition as compared to the steady DC application
with respect to particle diameter and number of layers.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
A ruthenium trinuclear polyazine complex was synthesized and subsequently immobilized through
complexation to a graphene oxide support containing phenanthroline ligands (GO-phen). The developed
photocatalyst was used for the photocatalytic reduction of CO2 to methanol, using a 20 watt white cold
LED flood light, in a dimethyl formamide–water mixture containing triethylamine as a reductive
quencher. After 48 h illumination, the yield of methanol was found to be 3977.57 5.60 mmol gcat
1.
The developed photocatalyst exhibited a higher photocatalytic activity than graphene oxide, which
provided a yield of 2201.40 8.76 mmol gcat
1. After the reaction, the catalyst was easily recovered and
reused for four subsequent runs without a significant loss of catalytic activity and no leaching of the
metal/ligand was detected during the reaction.
Growth and Characterization of Barium doped Potassium Hydrogen Phthalate Sing...IJERA Editor
The Non Linear Optical materials have acquired new significance with the advent of a large number of devices
utilizing solid state Laser sources. Potassium Hydrogen Phthalate one of the Non Linear Optical material having
superior non linear optical properties has been exploited for variety of application. In the present work, KHP
single crystals were grown by slow evaporation technique with Barium metal ion as a dopant. The grown
crystals were subjected to powder XRD analysis and the result shows that the Ba2+ ions does not alter the crystal
structure, but it enter into the crystal lattice of pure KHP. The optical transparency of the grown crystal was
studied by UV-Visible spectroscopy, the molecular structure was confirmed by FTIR analysis and its thermal
stability by TG/DTA analysis. The improved SHG efficiency of barium doped Potassium Hydrogen Phthalate
crystal could enhance the nonlinearity behaviour. In addition to this, the electrical parameter such as dielectric
constant was studied in detail.
Application of mixed colloidal magnetic fluid of single domain Fe3O4 and NiFe...IJERA Editor
Ferrofluids are stable suspensions of colloidal ferrimagnetic particles in suitable non – magnetic carrier liquids. They have attracted a lot of attention from scientists and engineers due to their many interesting properties and applications in various branches of engineering. The present work reports the performance of colloidal fluid of single domain nanoparticles of NiFe2O4 and Fe3O4. The thermal properties and its dynamics on magnetization as well as its effect on thermal conductivity on the colloidal fluid are studied here. Advantages of the increased thermal conductivity and optimization of magnetization of mixed colloidal fluid is used to extract the heat from voice coil. Nanoparticles of 21 nm of Fe3O4 and 12 nm of NiFe2O4 are used for mixed colloidal fluid. The suspension of particles is achieved by coating the nanoparticles with mono-corboxylic group on both the types of particles. The higher size (21 nm of Fe3O4 and 12 nm of NiFe2O4) particles are taken for synthesizing colloidal fluid, to have magnetic property of mixed colloidal liquid at elevated temperature of voice coil of speaker (Higher sized particles gives better magnetization). Oil is used as a carrier. Mixed magnetic colloidal fluid is used as a medium for damping so that noise is reduced at higher temperature of voice coil
Characterization of different dopants in TiO2 Structure by Pulsed Laser Dep...sarmad
Characterization of different dopants in TiO2 Structure by Pulsed Laser Deposition
A thesis submitted By: Khaled Z.Yahya
Supervised by: Prof.Dr. Adawiya J.Haider Prof.Dr. Raad M.S.Al-Haddad
IOSR Journal of Applied Physics (IOSR-JAP) is an open access international journal that provides rapid publication (within a month) of articles in all areas of physics and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in applied physics. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Synthesis & Characterization of Fluorescent Silver Nanoparticles stabilized b...IJERA Editor
Synthesis of silver nanoparticles (Ag-NPs) was achieved by a simple green procedure using Tinospora Cordifolia leaf extract as stabilizer/reducing agents. Ag-NPs in the size range of 2–19 nm is obtained by the treatment of aqueous silver ions with leaf extracts of Tinospora Cordifolia. This eco-friendly approach is simple, amenable for large scale commercial production and technical applications. Further, photoluminiscence studies of these Ag-NPs were recorded & suggested that the present particles were suitable for fluorescence emitting probes. These red emitting Ag-NPs exhibited distinct fluorescence properties (both emission and stokeshift).
Annealing and Microstructural Characterization of Tin-Oxide Based Thick Film ...Anis Rahman
Abstract. The sheet resistance of tin oxide based thick-film resistors exhibits two regions of temperature dependence,
described by hopping (23°C-200°C) and diffusion mechanisms (200°C-350°C), respectively.
Annealing these samples causes the sheet resistance to increase in both regions. In the post-annealed samples,
the hopping conduction range is extended by 50°C (23°C-250°C) while the hopping parameter, To, is decreased by
more than 50%. The activation energy of diffusion (0.60 eV) is the same for both pre- and post annealed samples, but
the magnitude of resistance in the diffusion controlled region is increased significantly as a result of annealing. These
changes are explained in terms of a net decrease in the concentration of tin ions in the glass matrix. From a careful
microstructural study it was found that a conduction path composed of tin-oxide grains or their clusters in contact
with each other does not exist in the present system. HREM micrographs showed the presence of nanocrystalline
tin-oxide particles in the glass phase separating the tin-oxide grain clusters. Estimated average separation between
the nanocrystals in 4 nm, consistent with a variable-range hopping conduction via the dissolved tin ions in the glass
matrix.
Transparent and Conducting TiO2 : Nb Thin Films Prepared by Spray Pyrolysis T...arj_online
To date, only sputtering and pulsed laser deposition (PLD) techniques have been employed
successfully to fabricate highly conducting and transparent TiO2:Nb (TNO) films. In this article, we demonstrate
that transparent and conducting
TiO2
: Nb
films can be made by the spray pyrolysis technique. The films were
deposited on Corning 7059 glass substrates at 500
15˚C using an alcoholic precursor solution consisting of
titanium (iv) isopropoxide and
NbCl5
. The influence of increasing
Nb
concentration on the electrical, optical
and structural properties was investigated. The minimum resistivity, 3.36
-3 10
Ω cm, for
Ti1-xNbxO2
film (x
= 0.15) was obtained after 1 hour post deposition annealing in hydrogen atmosphere at 500˚C. The x-ray
diffraction of hydrogen annealed films showed a polycrystalline anatase (004)-oriented phase without any second
phases. The optical band gap for undoped and doped films lay in the range 3.38 – 3.47 eV. Using dispersion
analysis, optical constants were determined from spectro-photometric measurements for films on glass.
Photoelectrochemical characterization of titania photoanodes fabricated using...Arkansas State University
Design and fabrication of new electrodes for photo-electrolysis using a material that is photo-active, stable, corrosion resistant, and cost effective.
Maiyalagan,Electro oxidation of methanol on ti o2 nanotube supported platinum...kutty79
TiO2 nanotubes have been synthesized using anodic alumina membrane as template. Highly dispersed
platinum nanoparticles have been supported on the TiO2 nanotube. The supported system
has been characterized by electron microscopy and electrochemical analysis. SEM image shows
that the nanotubes are well aligned and the TEM image shows that the Pt particles are uniformly
distributed over the TiO2 nanotube support. A homogeneous structure in the composite nanomaterials
is indicated by XRD analysis. The electrocatalytic activity ofthe platinum catalyst supported on
TiO2 nanotubes for methanol oxidation is found to be better than that of the standard commercial
E-TEK catalyst.
Studies on in-Doped Zno Transparent Conducting thin FilmsIJRESJOURNAL
ABSTRACT: In this manuscript we have investigated the influences of indium dopants on zinc oxide (ZnO) thin films regarding physico-chemical properties for application in modern conducting devices. As a starting material, Indium (III) chloride, and Zn(CH3COO)2⋅2H2O were used. The complex TSDC spectrum was obtained by submitting the sample to a constant electrical field Ep = 10M V/m during 2 min at a varing polarization temperature of Tmax = 1500C. A minimal sheet resistance with electrical resistivity as low in the range of 10-3 Ω·cm was found for this thin film.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
High-performance dye-sensitized solar cell using dimensionally controlled tit...Devika Laishram
The subject of the current study is a concoct of anatase and rutile mixed phase titania synthesized at 40 C and
10 C. At these sub-zero temperatures, highly crystalline, phase-oriented nanostructured titania were formed.
At 40 C, nanocrystals of TiO2 consist of the anatase phase while nanorods dominated by the rutile phase form
at 10 C. These samples are remarkable photoanode materials with excellent photon scattering ability in dyesensitized solar cells (DSSCs). On performance optimization of DSSCs, a composition of 0.5 wt% TiO2 (prepared
at 40 C) and P25 improved the photon harvesting by providing a large number of sites for interaction, resulting
in a high photocurrent of 18.46 mA cm2 and 8.6% photoconversion efficiency.
Isolated Iridium Sites on Potassium-Doped Carbon-nitride wrapped Tellurium Na...Pawan Kumar
Many industrial processes such transesterification of fatty acid for biodiesel production, soap manufacturing and biosynthesis of ethanol generate glycerol as a major by-product that can be used to produce commodity chemicals. Photocatalytic transformation of glycerol is an enticing approach that can exclude the need of harsh oxidants and extraneous thermal energy. However, the product yield and selectivity remain poor due to low absorption and unsymmetrical site distribution on the catalyst surface. Herein, tellurium (Te) nanorods/nanosheets (TeNRs/NSs) wrapped potassium-doped carbon nitride (KCN) van der Waal (vdW) heterojunction (TeKCN) is designed to enhance charge separation and visible-NIR absorption. The iridium (Ir) single atom sites decoration on the TeKCN core-shell structure (TeKCNIr) promotes selective oxidation of glycerol to glyceraldehyde with a conversion of 45.6% and selectivity of 61.6% under AM1.5G irradiation. The catalytic selectivity can reach up to 88% under 450 nm monochromatic light. X-ray absorption spectroscopy (XAS) demonstrates the presence of undercoordinated IrN2O2 sites which improved catalytic selectivity for glycol oxidation. Band energies and computational calculations reveal faile charge transfer in the TeKCNIr heterostructure. EPR and scavenger tests discern that superoxide (O2•−) and hydroxyl (•OH) radicals are prime components driving glycerol oxidation.
Isolated Iridium Sites on Potassium-Doped Carbon-nitride wrapped Tellurium Na...Pawan Kumar
Many industrial processes such transesterification of fatty acid for biodiesel production, soap manufacturing and biosynthesis of ethanol generate glycerol as a major by-product that can be used to produce commodity chemicals. Photocatalytic transformation of glycerol is an enticing approach that can exclude the need of harsh oxidants and extraneous thermal energy. However, the product yield and selectivity remain poor due to low absorption and unsymmetrical site distribution on the catalyst surface. Herein, tellurium (Te) nanorods/nanosheets (TeNRs/NSs) wrapped potassium-doped carbon nitride (KCN) van der Waal (vdW) heterojunction (TeKCN) is designed to enhance charge separation and visible-NIR absorption. The iridium (Ir) single atom sites decoration on the TeKCN core-shell structure (TeKCNIr) promotes selective oxidation of glycerol to glyceraldehyde with a conversion of 45.6% and selectivity of 61.6% under AM1.5G irradiation. The catalytic selectivity can reach up to 88% under 450 nm monochromatic light. X-ray absorption spectroscopy (XAS) demonstrates the presence of undercoordinated IrN2O2 sites which improved catalytic selectivity for glycol oxidation. Band energies and computational calculations reveal faile charge transfer in the TeKCNIr heterostructure. EPR and scavenger tests discern that superoxide (O2•−) and hydroxyl (•OH) radicals are prime components driving glycerol oxidation.
Isolated Iridium Sites on Potassium-Doped Carbon-nitride wrapped Tellurium Na...Pawan Kumar
Many industrial processes such transesterification of fatty acid for biodiesel production, soap manufacturing and biosynthesis of ethanol generate glycerol as a major by-product that can be used to produce commodity chemicals. Photocatalytic transformation of glycerol is an enticing approach that can exclude the need of harsh oxidants and extraneous thermal energy. However, the product yield and selectivity remain poor due to low absorption and unsymmetrical site distribution on the catalyst surface. Herein, tellurium (Te) nanorods/nanosheets (TeNRs/NSs) wrapped potassium-doped carbon nitride (KCN) van der Waal (vdW) heterojunction (TeKCN) is designed to enhance charge separation and visible-NIR absorption. The iridium (Ir) single atom sites decoration on the TeKCN core-shell structure (TeKCNIr) promotes selective oxidation of glycerol to glyceraldehyde with a conversion of 45.6% and selectivity of 61.6% under AM1.5G irradiation. The catalytic selectivity can reach up to 88% under 450 nm monochromatic light. X-ray absorption spectroscopy (XAS) demonstrates the presence of undercoordinated IrN2O2 sites which improved catalytic selectivity for glycol oxidation. Band energies and computational calculations reveal faile charge transfer in the TeKCNIr heterostructure. EPR and scavenger tests discern that superoxide (O2•−) and hydroxyl (•OH) radicals are prime components driving glycerol oxidation.
Solar-Driven Cellulose Photorefining into Arabinose over Oxygen-Doped Carbon ...Pawan Kumar
Biomass photorefining is a promising strategy to address the energy crisis and transition toward carbon carbon-neutral society. Here, we demonstrate the feasibility of direct cellulose photorefining into arabinose by a rationally designed oxygen-doped polymeric carbon nitride, which generates favorable oxidative species (e.g., O2–, •OH) for selective oxidative reactions at neutral conditions. In addition, we also illustrate the mechanism of the photocatalytic cellulose to arabinose conversion by density functional theory calculations. The oxygen insertion derived from oxidative radicals at the C1 position of glucose within cellulose leads to oxidative cleavage of β-1,4 glycosidic linkages, resulting in the subsequent gluconic acid formation. The following decarboxylation process of gluconic acid via C1–C2 α-scissions, triggered by surface oxygen-doped active sites, generates arabinose and formic acid, respectively. This work not only offers a mechanistic understanding of cellulose photorefining to arabinose but also sets up an example for illuminating the path toward direct cellulose photorefining into value-added bioproducts under mild conditions.
Solar-Driven Cellulose Photorefining into Arabinose over Oxygen-Doped Carbon ...Pawan Kumar
Biomass photorefining is a promising strategy to address the energy crisis and transition toward carbon carbon-neutral society. Here, we demonstrate the feasibility of direct cellulose photorefining into arabinose by a rationally designed oxygen-doped polymeric carbon nitride, which generates favorable oxidative species (e.g., O2–, •OH) for selective oxidative reactions at neutral conditions. In addition, we also illustrate the mechanism of the photocatalytic cellulose to arabinose conversion by density functional theory calculations. The oxygen insertion derived from oxidative radicals at the C1 position of glucose within cellulose leads to oxidative cleavage of β-1,4 glycosidic linkages, resulting in the subsequent gluconic acid formation. The following decarboxylation process of gluconic acid via C1–C2 α-scissions, triggered by surface oxygen-doped active sites, generates arabinose and formic acid, respectively. This work not only offers a mechanistic understanding of cellulose photorefining to arabinose but also sets up an example for illuminating the path toward direct cellulose photorefining into value-added bioproducts under mild conditions.
Solar-Driven Cellulose Photorefining into Arabinose over Oxygen-Doped Carbon ...Pawan Kumar
Biomass photorefining is a promising strategy to address the energy crisis and transition toward carbon carbon-neutral society. Here, we demonstrate the feasibility of direct cellulose photorefining into arabinose by a rationally designed oxygen-doped polymeric carbon nitride, which generates favorable oxidative species (e.g., O2–, •OH) for selective oxidative reactions at neutral conditions. In addition, we also illustrate the mechanism of the photocatalytic cellulose to arabinose conversion by density functional theory calculations. The oxygen insertion derived from oxidative radicals at the C1 position of glucose within cellulose leads to oxidative cleavage of β-1,4 glycosidic linkages, resulting in the subsequent gluconic acid formation. The following decarboxylation process of gluconic acid via C1–C2 α-scissions, triggered by surface oxygen-doped active sites, generates arabinose and formic acid, respectively. This work not only offers a mechanistic understanding of cellulose photorefining to arabinose but also sets up an example for illuminating the path toward direct cellulose photorefining into value-added bioproducts under mild conditions.
Partial Thermal Condensation Mediated Synthesis of High-Density Nickel Single...Pawan Kumar
Direct selective transformation of greenhouse methane (CH4) to liquid oxygenates (methanol) can substitute energy-intensive two-step (reforming/Fischer–Tropsch) synthesis while creating environmental benefits. The development of inexpensive, selective, and robust catalysts that enable room temperature conversion will decide the future of this technology. Single-atom catalysts (SACs) with isolated active centers embedded in support have displayed significant promises in catalysis to drive challenging reactions. Herein, high-density Ni single atoms are developed and stabilized on carbon nitride (NiCN) via thermal condensation of preorganized Ni-coordinated melem units. The physicochemical characterization of NiCN with various analytical techniques including HAADF-STEM and X-ray absorption fine structure (XAFS) validate the successful formation of Ni single atoms coordinated to the heptazine-constituted CN network. The presence of uniform catalytic sites improved visible absorption and carrier separation in densely populated NiCN SAC resulting in 100% selective photoconversion of (CH4) to methanol using H2O2 as an oxidant. The superior catalytic activity can be attributed to the generation of high oxidation (NiIII═O) sites and selective C─H bond cleavage to generate •CH3 radicals on Ni centers, which can combine with •OH radicals to generate CH3OH.
Partial Thermal Condensation Mediated Synthesis of High-Density Nickel Single...Pawan Kumar
Direct selective transformation of greenhouse methane (CH4) to liquid oxygenates (methanol) can substitute energy-intensive two-step (reforming/Fischer–Tropsch) synthesis while creating environmental benefits. The development of inexpensive, selective, and robust catalysts that enable room temperature conversion will decide the future of this technology. Single-atom catalysts (SACs) with isolated active centers embedded in support have displayed significant promises in catalysis to drive challenging reactions. Herein, high-density Ni single atoms are developed and stabilized on carbon nitride (NiCN) via thermal condensation of preorganized Ni-coordinated melem units. The physicochemical characterization of NiCN with various analytical techniques including HAADF-STEM and X-ray absorption fine structure (XAFS) validate the successful formation of Ni single atoms coordinated to the heptazine-constituted CN network. The presence of uniform catalytic sites improved visible absorption and carrier separation in densely populated NiCN SAC resulting in 100% selective photoconversion of (CH4) to methanol using H2O2 as an oxidant. The superior catalytic activity can be attributed to the generation of high oxidation (NiIII═O) sites and selective C─H bond cleavage to generate •CH3 radicals on Ni centers, which can combine with •OH radicals to generate CH3OH.
Selective Cellobiose Photoreforming for Simultaneous Gluconic Acid and Syngas...Pawan Kumar
Here, we demonstrate the selective cellobiose (building block of cellulose) photoreforming for gluconic acid and syngas co-production in acidic conditions by rationally designing a bifunctional polymeric carbon nitride (CN) with potassium/sulfur co-dopant. This heteroatomic doped CN photocatalyst possesses enhanced visible light absorption, higher charge separation efficiency than pristine CN. Under acidic conditions, cellobiose is not only more efficiently hydrolyzed into glucose but also promotes the syngas and gluconic acid production. Density functional theory (DFT) calculations reveal the favorable generation of •O2− during the photocatalytic reaction, which is essential for gluconic acid production. Consequently, the fine-designed photocatalyst presents excellent cellobiose conversion (>80%) and gluconic acid selectivity (>70%) together with the co-production of syngas (~56 μmol g-1 h-1) under light illumination. The current work demonstrates the feasibility of biomass photoreforming with value-added chemicals and syngas co-production under mild condition.
Selective Cellobiose Photoreforming for Simultaneous Gluconic Acid and Syngas...Pawan Kumar
Here, we demonstrate the selective cellobiose (building block of cellulose) photoreforming for gluconic acid and syngas co-production in acidic conditions by rationally designing a bifunctional polymeric carbon nitride (CN) with potassium/sulfur co-dopant. This heteroatomic doped CN photocatalyst possesses enhanced visible light absorption, higher charge separation efficiency than pristine CN. Under acidic conditions, cellobiose is not only more efficiently hydrolyzed into glucose but also promotes the syngas and gluconic acid production. Density functional theory (DFT) calculations reveal the favorable generation of •O2− during the photocatalytic reaction, which is essential for gluconic acid production. Consequently, the fine-designed photocatalyst presents excellent cellobiose conversion (>80%) and gluconic acid selectivity (>70%) together with the co-production of syngas (~56 μmol g-1 h-1) under light illumination. The current work demonstrates the feasibility of biomass photoreforming with value-added chemicals and syngas co-production under mild condition.
Selective Cellobiose Photoreforming for Simultaneous Gluconic Acid and Syngas...Pawan Kumar
Here, we demonstrate the selective cellobiose (building block of cellulose) photoreforming for gluconic acid and syngas co-production in acidic conditions by rationally designing a bifunctional polymeric carbon nitride (CN) with potassium/sulfur co-dopant. This heteroatomic doped CN photocatalyst possesses enhanced visible light absorption, higher charge separation efficiency than pristine CN. Under acidic conditions, cellobiose is not only more efficiently hydrolyzed into glucose but also promotes the syngas and gluconic acid production. Density functional theory (DFT) calculations reveal the favorable generation of •O2− during the photocatalytic reaction, which is essential for gluconic acid production. Consequently, the fine-designed photocatalyst presents excellent cellobiose conversion (>80%) and gluconic acid selectivity (>70%) together with the co-production of syngas (~56 μmol g-1 h-1) under light illumination. The current work demonstrates the feasibility of biomass photoreforming with value-added chemicals and syngas co-production under mild condition.
Partial Thermal Condensation Mediated Synthesis of High-Density Nickel Single...Pawan Kumar
Direct selective transformation of greenhouse methane (CH4) to liquid oxygenates (methanol) can substitute energy-intensive two-step (reforming/Fischer–Tropsch) synthesis while creating environmental benefits. The development of inexpensive, selective, and robust catalysts that enable room temperature conversion will decide the future of this technology. Single-atom catalysts (SACs) with isolated active centers embedded in support have displayed significant promises in catalysis to drive challenging reactions. Herein, high-density Ni single atoms are developed and stabilized on carbon nitride (NiCN) via thermal condensation of preorganized Ni-coordinated melem units. The physicochemical characterization of NiCN with various analytical techniques including HAADF-STEM and X-ray absorption fine structure (XAFS) validate the successful formation of Ni single atoms coordinated to the heptazine-constituted CN network. The presence of uniform catalytic sites improved visible absorption and carrier separation in densely populated NiCN SAC resulting in 100% selective photoconversion of (CH4) to methanol using H2O2 as an oxidant. The superior catalytic activity can be attributed to the generation of high oxidation (NiIII═O) sites and selective C─H bond cleavage to generate •CH3 radicals on Ni centers, which can combine with •OH radicals to generate CH3OH.
Recent advancements in tuning the electronic structures of transitional metal...Pawan Kumar
The smooth transition from finite non-renewables to renewable energy conversion technologies will require efficient electrocatalysts which can harness intermittent energies to store in the form of chemical bonds. The oxygen evolution reaction (OER) impedes the widespread usage of water electrolyzers to convert H2O into H2 and persists as a bottleneck, including other energy conversion devices with sluggish four H+/e− kinetics. In this context, designing highly active and stable catalysts capable of driving a lower overpotential in the OER to produce continuous hydrogen (H2) is a primary demanded. This chapter discussed the mechanism of the OER in conventional adsorbate oxygen and lattice oxygen participation in transition metal oxides (TMOs). Further, the influences of surface engineering, doping, and defects in the TMOs and understanding the electronic structure to screen electrodes towards the structure–activity relationship are highlighted. Specifically, the adsorption strength of O 2p is understood in detail as its binding ability over the surface of TMOs can be correlated directly to the OER activity. The iterative development of TMOs in terms of understanding electronic structural attributes is essential for the commercial deployment of energy conversion technologies. The comprehensive outlook of this chapter investigates thoroughly how TMOs can be used as significant materials for the OER in the near future.
Hole transport materials (HTMs) have a significant impact on the effectiveness of organic electronic devices; therefore, we present a molecular architecture of pyrazino[2,3-g]quinoxaline (PQ10)-based room-temperature organic liquid crystalline semiconductor (OLCS) as an alternative HTM. The PQ10 compound exhibits three different rectangular columnar (Colr) phases offering an impressive hole mobility of 8.8 × 10−3 cm2V−1s−1 which is found to be dexterous than most of existing polymeric hole transport materials. The charge transport mechanism is governed by the hole polarons hopping through H-aggregates of the PQ10 molecules and the hole mobility remains nearly constant throughout the mesophase range, but it decreases with increasing applied electric field. The current-voltage characteristics of the PQ10 have also been investigated in all three Colr phases and explained via the Poole-Frenkel conduction mechanism. The dielectric spectroscopy has been eventually carried out to understand the nature of dielectric permittivity and conductivity as a function of temperature and a correlation is established between the molecular architecture of the Colr phases and aforementioned physical properties. Solar cell simulation has been additionally performed to demonstrate that the PQ10 material can be a better choice as HTM for organic electronics and photovoltaic applications.
Multifunctional carbon nitride nanoarchitectures for catalysisPawan Kumar
Catalysis is at the heart of modern-day chemical and pharmaceutical industries, and there is an urgent demand to develop metal-free, high surface area, and efficient catalysts in a scalable, reproducible and economic manner. Amongst the ever-expanding two-dimensional materials family, carbon nitride (CN) has emerged as the most researched material for catalytic applications due to its unique molecular structure with tunable visible range band gap, surface defects, basic sites, and nitrogen functionalities. These properties also endow it with anchoring capability with a large number of catalytically active sites and provide opportunities for doping, hybridization, sensitization, etc. To make considerable progress in the use of CN as a highly effective catalyst for various applications, it is critical to have an in-depth understanding of its synthesis, structure and surface sites. The present review provides an overview of the recent advances in synthetic approaches of CN, its physicochemical properties, and band gap engineering, with a focus on its exclusive usage in a variety of catalytic reactions, including hydrogen evolution reactions, overall water splitting, water oxidation, CO2 reduction, nitrogen reduction reactions, pollutant degradation, and organocatalysis. While the structural design and band gap engineering of catalysts are elaborated, the surface chemistry is dealt with in detail to demonstrate efficient catalytic performances. Burning challenges in catalytic design and future outlook are elucidated.
Production of Renewable Fuels by the Photocatalytic Reduction of CO2 using Ma...Pawan Kumar
The photo-reductive performance of natural ilmenite was boosted and the production of renewable fuels from the reduction of CO2 was enhanced by doping the natural mineral with magnesium. The doping was achieved by high energy ball milling in the presence of MgO and Mg(NO3)2. The photo-reduction of CO2 in aqueous solution led to the evolution of H2, CH4, C2H4, and C2H6, and the insertion of Mg in the structure of ilmenite enabled increases of up to 1245% in the fuel production yield, reaching total production of 210.9 µmol h-1 gcat-1. Displacements of the conduction band to more negative potentials were evidenced for the samples doped with magnesium. Indirect effects such as increases in the valence band maximum, and the introduction of intermediate energy levels were also evidenced through the measurement of the crystallite size and the determination of the band structure of the materials. Mott-Schottky analyses of the samples showed the n-type nature of the semiconductor materials and enabled the estimation of the density of charge carriers, which strongly influenced the photocatalytic performance. The strong potential of the application of natural ilmenite in gas phase artificial photosynthesis was proved by the evaluation of CO2 reduction in gas conditions, which allowed the enhancement in the selectivity and significantly increased the production of CH4 as compared to aqueous solution, reaching an important yield of CH4 of 16.1 µmol h-1 gcat-1.
Nanoengineered Au-Carbon Nitride Interfaces Enhance PhotoCatalytic Pure Water...Pawan Kumar
Photocatalytic pure water splitting using solar energy is one of the promising routes to produce sustainable green hydrogen (H2). Tuning the interfacial active site density at catalytic heterojunctions and better light management are imperative to steer the structure-activity correlations to enhance the photo-efficiency of nanocomposite photocatalysts. Herein, we report the decoration of nitrogen defects-rich carbon nitride CN(T) with metallic Au nanostructures of different morphologies and sizes to investigate their influence on the photocatalytic hydrogen evolution reactions (HER). The CN(T)-7-NP nano-heterostructure comprises Au nanoparticles (NPs) of ~7 nm and thiourea-derived defective CN exhibits an excellent H2 production rate of 76.8 µmol g–1 h–1 from pure water under simulated AM 1.5 solar irradiation. In contrast to large-size Au nanorods, the high activity of CN(T)-7-NP was attributed to their strong localized surface plasmon resonance (LSPR) mediated visible absorption and interfacial charge separation. The surface ligands used to control Au nanostructures morphology were found to play a major role in the stabilization of NPs and improve interfacial charge transport between Au NPs and CN(T). First-principles calculations revealed that defects in CN and Au-CN interfacial sites in these nanocomposites facilitate the separation of e-/h+ pairs after light excitation and provide lower energy barrier pathways for H2 production by photocatalytic water splitting.
Nanoengineered Au-Carbon Nitride Interfaces Enhance Photo-Catalytic Pure Wate...Pawan Kumar
Photocatalytic pure water splitting using solar energy is one of the promising routes to produce sustainable green hydrogen (H2). Tuning the interfacial active site density at catalytic heterojunctions and better light management are imperative to steer the structure-activity correlations to enhance the photo-efficiency of nanocomposite photocatalysts. Herein, we report the decoration of nitrogen defects-rich carbon nitride CN(T) with metallic Au nanostructures of different morphologies and sizes to investigate their influence on the photocatalytic hydrogen evolution reactions (HER). The CN(T)-7-NP nano-heterostructure comprises Au nanoparticles (NPs) of ~7 nm and thiourea-derived defective CN exhibits an excellent H2 production rate of 76.8 µmol g–1 h–1 from pure water under simulated AM 1.5 solar irradiation. In contrast to large-size Au nanorods, the high activity of CN(T)-7-NP was attributed to their strong localized surface plasmon resonance (LSPR) mediated visible absorption and interfacial charge separation. The surface ligands used to control Au nanostructures morphology were found to play a major role in the stabilization of NPs and improve interfacial charge transport between Au NPs and CN(T). First-principles calculations revealed that defects in CN and Au-CN interfacial sites in these nanocomposites facilitate the separation of e-/h+ pairs after light excitation and provide lower energy barrier pathways for H2 production by photocatalytic water splitting.
Cooperative Copper Single Atom Catalyst in Two-dimensional Carbon Nitride for...Pawan Kumar
Renewable electricity powered carbon dioxide (CO2) reduction (eCO2R) to high-value fuels like methane (CH4) holds the potential to close the carbon cycle at meaningful scales. However, this kinetically staggered 8-electron multistep reduction still suffers from inadequate catalytic efficiency and current density. Atomic Cu-structures can boost eCO2R-to-CH4 selectivity due to enhanced intermediate binding energies (BEs) resulting from favorably shifted d-band centers. Herein, we exploit two-dimensional carbon nitride (CN) matrices, viz. Na-polyheptazine (PHI) and Li-polytriazine imides (PTI), to host Cu-N2 type single atom sites with high density (∼1.5 at%), via a facile metal ion exchange process. Optimized Cu loading in nanocrystalline Cu-PTI maximizes eCO2R-to-CH4 performance with Faradaic efficiency (FECH4) of ≈68% and a high partial current density of 348 mA cm−2 at a low potential of -0.84 V versus RHE, surpassing the state-of-the-art catalysts. Multi-Cu substituted N-appended nanopores in the CN frameworks yield thermodynamically stable quasi-dual/triple sites with large interatomic distances dictated by the pore dimensions. First-principles calculations elucidate the relative Cu-CN cooperative effects between the two matrices and how the Cu-Cu distance and local environment dictate the adsorbate BEs, density of states, and CO2-to-CH4 energy profile landscape. The 9N pores in Cu-PTI yield cooperative Cu-Cu sites that synergistically enhance the kinetics of the rate-limiting steps in the eCO2R-to-CH4 pathway.
Bioinspired multimetal electrocatalyst for selective methane oxidationPawan Kumar
Selective partial electrooxidation of methane (CH4) to liquid oxygenates has been a long-sought goal. However, the high activation energy of C–H bonds and competing oxygen evolution reaction limit product selectivity and reaction rates. Inspired by iron (IV)-oxo containing metalloenzymes’ functionality to activate the C–H bond, here we report on the design of a copper-iron-nickel catalyst for selective oxidation of CH4 to formate via a peroxide-assisted pathway. Each catalyst serves a specific role which is confirmed via electrochemical, in situ, and theoretical studies. A combination of electrochemical and in situ spectroelectrochemical studies revealed that H2O2 oxidation on nickel led to the formation of active oxygen species which trigger the formation of iron (IV) at low voltages. Density functional theory analysis helped reveal the role of iron (IV)-oxo species in reducing the activation energy barrier for CH4 deprotonation and the critical role of copper to suppress overoxidation. Our multimetal catalyst exhibits a formate faradaic efficiency of 42% at an applied potential of 0.9 V versus a reversible hydrogen electrode.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
The increased availability of biomedical data, particularly in the public domain, offers the opportunity to better understand human health and to develop effective therapeutics for a wide range of unmet medical needs. However, data scientists remain stymied by the fact that data remain hard to find and to productively reuse because data and their metadata i) are wholly inaccessible, ii) are in non-standard or incompatible representations, iii) do not conform to community standards, and iv) have unclear or highly restricted terms and conditions that preclude legitimate reuse. These limitations require a rethink on data can be made machine and AI-ready - the key motivation behind the FAIR Guiding Principles. Concurrently, while recent efforts have explored the use of deep learning to fuse disparate data into predictive models for a wide range of biomedical applications, these models often fail even when the correct answer is already known, and fail to explain individual predictions in terms that data scientists can appreciate. These limitations suggest that new methods to produce practical artificial intelligence are still needed.
In this talk, I will discuss our work in (1) building an integrative knowledge infrastructure to prepare FAIR and "AI-ready" data and services along with (2) neurosymbolic AI methods to improve the quality of predictions and to generate plausible explanations. Attention is given to standards, platforms, and methods to wrangle knowledge into simple, but effective semantic and latent representations, and to make these available into standards-compliant and discoverable interfaces that can be used in model building, validation, and explanation. Our work, and those of others in the field, creates a baseline for building trustworthy and easy to deploy AI models in biomedicine.
Bio
Dr. Michel Dumontier is the Distinguished Professor of Data Science at Maastricht University, founder and executive director of the Institute of Data Science, and co-founder of the FAIR (Findable, Accessible, Interoperable and Reusable) data principles. His research explores socio-technological approaches for responsible discovery science, which includes collaborative multi-modal knowledge graphs, privacy-preserving distributed data mining, and AI methods for drug discovery and personalized medicine. His work is supported through the Dutch National Research Agenda, the Netherlands Organisation for Scientific Research, Horizon Europe, the European Open Science Cloud, the US National Institutes of Health, and a Marie-Curie Innovative Training Network. He is the editor-in-chief for the journal Data Science and is internationally recognized for his contributions in bioinformatics, biomedical informatics, and semantic technologies including ontologies and linked data.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
Thanks...!
Body fluids_tonicity_dehydration_hypovolemia_hypervolemia.pptx
Vapor Deposition of Semiconducting Phosphorus Allotropes into TiO2 Nanotube Arrays for Photoelectrocatalytic Water Splitting
1. S-1
Supporting Information
Vapor Deposition of Semiconducting Phosphorus
Allotropes into TiO2 Nanotube Arrays for
Photoectrocatalytic Water Splitting
Ebru Üzer, a
Pawan Kumar,b†
Ryan Kisslinger,b†
Piyush Kar,b
Ujwal Kumar Thakur,b
Sheng
Zeng,b
Karthik Shankar, b,
* and Tom Nilges a,
*
Department of Chemistry, Technical University of Munich, Lichtenbergstrasse 4, 85748
Garching, Germany; E-mail: tom.nilges@lrz.tum.de
Department of Electrical and Computer Engineering, 9211-116 Street NW, Edmonton,
Alberta, Canada T6G 1H9; E-mail: kshankar@ualberta.ca.
†Contributed equally
2. S-2
1 EXPERIMENTAL DETAILS
1.1 Synthesis of TiO2 nanotube membranes
The anodization method was used to fabricate TiO2 nanotube membranes.1
Titanium foil 0.5 cm
wide and 2 cm long was used as the cathode, and titanium foil 1 cm wide and 4 cm long was
used as the anode; both titanium pieces had thicknesses of 0.89 mm. The electrolyte was
comprised of ethylene glycol with the addition of 3 Vol.-% deionized water and 0.03 wt%
NH4F. The electrolyte was well-mixed before anodization. The cathode and anode were spaced
2 cm apart in a 100 mL beaker filled with electrolyte; this beaker was submerged in an ice-
water bath for cooling. A constant voltage of 60 V was applied for 3 days. Afterwards, samples
were removed and submerged in methanol for cleaning, and a razor was used to scratch off the
anodized 0.89 mm thick sides of the titanium piece to enable delamination of the membranes.
The membranes were left to dry, which caused delamination of the membrane to occur. The
inner pores of the nanotubes were then exposed by reactive ion etching, followed by a cleaning
step for each side of the membrane. An SF6 etch using a pressure of 20 mTorr and a forward
power of 250 W was utilized, followed immediately by an O2 clean using a pressure of 150
mTorr and a forward power of 225 W. The side of the membrane that was exposed directly to
electrolyte was subjected to the SF6 etch for 200 s followed by the O2 clean for 10 min; the
membrane was then flipped, and the side of the membrane that formed the barrier layer of
TiO2/Ti foil was subjected to the SF6 etch for 300 s followed by the O2 etch for 10 min.
1.2 Synthesis of hybrid fibrous P@TiO2 nanotube membranes
Chemical vapor deposition of fibrous red P on TiO2 nanotube membranes was attained
according to literature procedures.2
Red phosphorus (300 mg, ultrahigh grade, 99.999+%,
Chempur) and purified CuI (15 mg) were transferred into a silica-glass tube (0.8 cm inner
diameter, 8 cm length). TiO2 nanotube membranes were subsequently added. The ampoule was
sealed under vacuum (p < 10–3
mbar) and placed horizontally in a Nabertherm muffle furnace
(L3/11/330) by locating the precursors in the hot zone of the furnace and the TiO2 nanotube
membranes to the colder zone. The furnace was heated to 773 K within 8 h, with a holding
period of 48 h, cooled down to 673 K within 24 h and held at this temperature for 11 d. Room
temperature was reached within 24 h.
Purification of CuI was carried out by solving CuI (98+%, Chempur) in concentrated HI
(57 %, Riedel de Häen) and a following precipitation in water. The precipitate was purified by
washing twice with water and ethanol and dried under vacuum.
1.3 Synthesis of black P@TiO2 nanotube membranes
The preparation of black P@TiO2 nanotube membranes can be carried out through in situ
growth from amorphous red phosphorus following a short way transport reaction following the
literature procedures.3
The precursors Sn (20 mg, 99.999%, Chempur) and SnI4 (189.6 mg,
synthesized according to literature procedures)4
were added as mineralization additives. Red
phosphorus (500 mg, Chempur, 99.999+%) were placed together with Sn and SnI4 in a silica-
glass tube (0.8 cm inner diameter, 8 cm length, 0.25 cm wall thickness) and TiO2 nanotube
membranes in short distance. The ampoule was sealed under vacuum (p < 10−3
mbar) and then
3. S-3
put horizontally, with the precursors located at the hot end and the TiO2 nanotube membranes
located towards the colder zone of the Nabertherm muffle furnace (L3/11/330). The furnace
was heated to 923 K and then cooled down within 7.5 h to 773 K.
1.4 Photo-/electrochemical characterization
To determine the electrochemical properties of the samples a CHI660E series electrochemical
workstation equipped with a three-electrode configuration was used. A FTO glass deposited
sample was assigned as working electrode (photoanode) while Pt and Ag/AgCl electrodes were
used as counter (cathode) and reference electrode respectively. To fabricate the photoanode a
20 nm thick layer of TiO2 compact layer was deposited on FTO by following our previous
recipe after three times dilution of titanium di-isopropoxide solution.5
The thin TiO2 layer serves
as blocking layer by preventing direct contact between solvent and FTO. After that the
materials, dispersed in very dilute solution of titanium di-isopropoxide, were drop-casted on
TiO2 followed by heating up to 150 °C for 1 h which allows robust binding of the materials on
the surface of FTO/TiO2. To measure the photo-electrochemical performance 0.1 M KOH was
used as electrolyte. Three electrodes were immersed in KOH electrolyte and
photoelectrochemical performance was investigated by sweeping the applied voltage from –
1.0 V to +0.8 V vs Ag/AgCl at 10 mV/s scan rate. A solar simulator (Newport, Oriel instrument
USA, model 67005, solar simulator) equivalent to AM1.5 G spectrum having a power density
of 100 mW m–2
at the sample surfaces was used for photo-irradiation. The photo-response of
the materials at higher wavelength and respective efficiencies (IPCE and APCE%) were
determined using monochromatic 425 nm (54.15 mW cm–2
), 420, 505, 580 and 620 nm
wavelength LED having a power density of 21.00 mW cm-2
on the electrode surface. For the
measurements of evolved hydrogen on the Pt counter electrode a photoelectrochemical water
splitting H-cell was used. The samples from the Pt electrode containing arm was withdrawn
after 2 h interval using a gas tight syringe and injected in a GC (gas chromatographer). See
Figure S16 for an image of the experimental setup. To confirm oxygen evolution occured due
to photoelectrochemical water splitting, the gaseous sample from the photoanode was analyzed
using GC-PDD (gas chromatographer pulsed discharge detector) before photoirradiation (after
purging with N2 for 30 min) and after photoirradiation for 1 h. Flat band potential and charge
carrier concentration of the materials were determined from Mott-Schottky analysis obtained
from impedance-potential measurements using 0.5 M Na2SO4 solution in –1.0 to +1.0 V range
at 1 K frequency. Nyquist plotting to draw equivalent circuit and to determine the value of
charge transfer resistance, space charge capacitance, carrier lifetime etc. was obtained using
electrochemical impedance spectroscopy (EIS) under dark and 1 sun irradiation on the applied
potential of –0.5 V vs Ag/AgCl in 0.1 M KOH, with an AC amplitude of 0.005 V at frequency
value 1 Hz to 100 kHz.
Chemicals and reagents. Anhydrous Na2SO4 (99.0%), KOH (99.0%), titanium(IV)-
isopropoxide (99.99%), were purchased from Sigma Aldrich and used as received. Fluorine
doped tin oxide (FTO) glass (transmittance 80-82%) was purchased from Hartford Tec Glass
Company. The surface of FTO was degreased by ultrasonication in water, methanol and acetone
for 10 min each. HPLC grade solvents were used throughout studies.
Structural and physicochemical characterization
4. S-4
X-ray powder diffraction. X-ray powder data were applied on a Stoe Stadi P diffractometer
(Cu-K1 radiation, = 1.5406 Å, Ge-monochromator) fitted with a Mythen 1 K detector (Fa.
Dectris) and calibrated externally using (a = 5.43088 Å). Phase analysis and indexing was
carried out with the program package of Stoe Winxpow 2011.6
Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDS).
Scanning Electron Microscopy imaging on TiO2 nanotubes and according nanofibers were
performed via JEOL [SEM 5900LV, Si (Li) detector]. The composition of the hybrid
compounds was determined semi-quantitatively by EDS measurements (Energy Dispersive X-
ray Spectroscopy, Röntec). The samples were applied with an acceleration voltage of 15 kV.
The measured composition is in good agreement with the composition achieved from structure
refinement.
Scanning Transmission Electron Microscope (STEM) and Energy Dispersive X-ray
spectroscopy (EDS). STEM-EDS analysis data were collected on a JEOL JEM-ARM200cF
STEM, along with a cold Field-Emission Gun (cFEG) and a probe Cs corrector. EDS scans
were applied with a Silicon Drift (SDD) EDS detector at an acceleration voltage of 200 kV.
Raman spectroscopy. The hybrid semiconductor@TiO2 nanotube arrays were investigated by
Raman spectroscopy at 300 K using a Renishaw inVia RE04 Raman Microscope fitted with a
Nd:YAG and diode laser ( = 532 nm; 785 nm) and a CCD detector. The applied laser power
was 250 mW, recording a total number of 500 scans. Scans along a razor cut cross section of
the membranes were conducted by moving the focused Raman beam from the outside to the
center of the membrane via a x-y stage. One Raman spectrum was recorded for each individual
step.
Scheme S1. Left: Raman microscope focus on a cross section of a membrane used for Raman spectroscopic
investigations. Right: Consecutive Raman spectra were recorded along the cross section.
X-ray Photoelectron spectroscopy (XPS) and Ultraviolet photoelectron spectroscopy
(UPS). To determine the surface chemical nature and binding energy of elements XPS was
performed on all samples using Axis-Ultra, Kratos Analytical instrument equipped with
monochromatic Al-K source (15 kV, 50 W) with an incident X-ray energy of 1486.7 eV
operating under ultra-high vacuum (UHV ∼10–8
Torr). To assign the binding energy of the
5. S-5
elements the binding energy of C1s of adventitious hydrocarbon (BE 284.8 eV) was used as
standard (carbon correction). The acquired raw data in the form of .vms files was
deconvoluted in various peak components using CasaXPS and extracted .csv files were
plotted in origin 8.5. The electronic band structure of all materials was determined using
ultraviolet photoelectron spectroscopy (UPS) using a 21.21 eV He I line of a He discharge
lamp to collect work function and valence band spectra.
Diffuse reflectance UV-Vis spectroscopy (DR UV-Vis). The absorption spectra of all
materials in UV-Vis region was recorded on a Perkin Elmer Lambda-1050 UV–Vis-NIR
spectrophotometer working in diffuse reflectance mode equipped with an integrating sphere
accessory.
Kelvin Probe Force Microscopy (KPFM). The nature of charge carrier transport to probe the
successful formation of heterojunction between infiltrated phosphorous and TiO2 nanotubes,
surface potential (SP) of bare and hybrid materials were determined using peak force KPFM on
a Dimension Fast Scan Atomic Force microscope (Bruker Nanoscience Division, Santa
Barbara, CA, USA). To perform KPFM measurements, samples were deposited on FTO and a
Pt coated SiNSCM-PIT cantilever of 2.5 4.4 N/m stiffness was used. Samples containing FTO
were grounded with the AFM chuck using a conductive copper tape. The surface potential of
the samples was measured at 100 nm x 75 nm lift height at 12 kHz lockin bandwidth and a scan
speed of 0.51 Hz. To investigate charge carrier dynamics under light irradiation conditions
samples were irradiated with 450 and 635 nm LEDs and dark and light conditions were
maintained for 5 min, to achieve equilibrium condition. The measurements were performed at
zero tip bias and Pt tip was calibrated by measuring the contact potential difference (CPD) of
highly oriented pirolytic graphite (HOPG) and the Pt tip using following expression.
EF (tip) = 4.6 eV (Work function of HOPG) + VCPD (HOPG and Pt tip)
Gas chromatography (GC). The identification and quantification of reaction product was
done by gas chromatography using custom made Shimadzu GC equipped with Porapak Q
column and Mol Sieve column, and a pulsed discharge detector (PDD). Conditions: He carrier
flow rate: 0.5 mL min−1
, detector temperature: 160 °C, oven temp: started from 60 °C and raised
up to 160 °C to expel water vapor. A standard calibration gas mixture (Praxair gas, Canada)
was used for the quantification of hydrogen.
6. S-6
2 STRUCTURAL CHARACTERIZATION
2.1 Fibrous red P@TiO2 nanotube hybrids
Figure S1. Powder X-ray diffraction substantiates the formation of crystalline fibrous red phosphorus onto the
membrane. A calculated diffractogram based on the structure data of fibrous red phosphorus2
is drawn with
negative intensities. Slight variations in intensity are due to texture effects.
In Figure S2 Raman modes were detected 5 m in distance to the membrane surface. The
formation of fibrous red Phosphorus was confirmed at this depth. Significant shifts are found
for the 158 cm-1
Eg mode, which is located at 145 cm-1
in the hybrid material. The whole
spectrum of anatase is slightly shifted towards higher wavenumbers, which can be due to doping
or defect formation in TiO2.
Figure S2. Raman spectroscopy on fibrous red P@TiO2 membranes a) Raman spectra of a fresh TiO2 membrane
(anatase, grey), fibrous red P@TiO2 membrane cross section measured approx. 5 m in distance to the surface
(black), fibrous red P (red), recorded at the surface and reference spectrum of fibrous red P (dark red). Raman-
microscope picture of the fibrous red P@TiO2 membrane where the Raman spectrum was recorded at the top. b)
Raman spectra of a fresh TiO2 membrane (anatase, grey), fibrous red P@TiO2 membrane cross section measured
approx. 15 m in distance to the surface (black), fibrous red P(red), recorded at the surface and reference spectrum
of fibrous red P (dark red). Raman-microscope images of fibrous red P@TiO2 membranes, recorded during the
measurement show the laser path along the cross section.
7. S-7
2.2 Black P@TiO2 nanotube hybrids
Figure S3. Powder X-ray diffraction confirms formation of crystalline black phosphorus onto the membrane. A
calculated diffractogram based on the structure data of black phosphorus3
is drawn with negative intensities. Slight
variations in intensity are due to texture effects.
2.3 EDS analysis
Table S1. Elemental analysis of deposited crystals found on both sides of the membranes and different spots along
the razor cut cross section of fibrous red P@TiO2 membranes via EDS-measurements. Elemental composition in
at% deriving from P and Ti were found whereas Cu and I (originated from the mineralizer used during synthesis)
could not be detected. Atomic percent of Ti is representing Ti in TiO2.
EDS P (at%) Ti (at%) Cu (at%) I (at%)
Fibrous red P@TiO2 cross
section 1
75.7(6) 24.3(4) — —
Fibrous red P@TiO2 cross
section 2
37.5(4) 62.5(6) — —
Table S2. Elemental analysis of deposited crystals found on both sides of the membranes and different spots along
the razor cut cross section of black P@TiO2 membranes via EDS-measurements. Elemental composition in at%
deriving from P and Ti were found whereas Sn and I (originated from the mineralizer used during synthesis) was
present in small amounts. Atomic percent of Ti is representing Ti in TiO2.
EDS P (at%) Ti (at%) Sn (at%) I (at%)
Black P@TiO2 cross
section 1
26.8(3) 72.0(6) 1.1(1) —
Black P@TiO2 cross
section 2
75.4(6) 19.7(3) 3.5(2) 1.3(2)
8. S-8
2.4 UV-Vis analysis
Figure S4. DRS UV-Vis spectra of a) TiO2, fibrous red P, and fibrous red P@TiO2. b) TiO2, black P, and black
P@TiO2. Tauc plot for c) TiO2, fibrous red P, and fibrous red P@TiO2. d) black P, TiO2, and black P@TiO2.
Color: TiO2 (black), black P, fibrous red P (red), black P@TiO2 and fibrous red P@TiO2 (blue).
2.5 XPS analysis of phosphorus allotrope@TiO2 membranes
The nature of the chemical species present in the materials and their binding energies were
determined using high resolution X-ray photoelectron spectroscopy (HR-XPS). Survey scan for
elemental analysis gave peaks corresponding to all the elements in TiO2 (Ti2p, O1s), black P
(P2p), black P@TiO2 (P2p, Ti2p, O1s), fibrous red P (P2p) and fibrous red P@TiO2 (P2p, Ti2p,
O1s) (Figure S5a and b). The deconvoluted core-level HR-XPS spectra of TiO2 gave two peak
components centred at BE 459.7 and 465.3 eV, originating from Ti2p3/2 and Ti2p1/2
components of Ti4+
present in anatase phase TiO2 (Figure S5a).7-9
The position of Ti2p3/2 and
Ti2p1/2 components does not change after vapor phase growth of black P and fibrous red P on
and inside TiO2 nanotube membranes which implies, the oxidation state of Ti in TiO2 lattice
remains equal (4+) during deposition conditions (Figure S5a and b). Further, the absence of any
9. S-9
shoulder peak in Ti2p region overrules any possibility of phosphorus doping in TiO2 lattice.
HR-XPS spectra of TiO2 in O1s region was deconvoluted in two peaks components located at
530.9 and 532.2 eV, assigned to Ti4+
coordinated oxygen atoms present in TiO2 crystal lattice
and surface adsorbed non-lattice oxygen (adventitious and –OH oxygens).10-11
After vapor phase
deposition of black P on TiO2 the O1s peak get shifted toward higher binding energies and new
peaks were situated at 532.6 and 533.8 eV. The shifting of O1s peak was attributed due to
transformation of certain fraction of black P into P-O (bridging and dangling oxygen bonding)
and coordination of P atoms in black P with Ti4+
present on the surface of TiO2 which change
coordination environment of lattice bounded oxygen on the surface of TiO2 (Figure S5c).12-13
Previous studies demonstrated that three P atoms in black P can coordinate tetragonally with
surface metals centre which provides more stable configuration due to satisfaction of
tetravalency of undercoordinated Ti4+
present on the surface of TiO2.14-16
It should be noted that
XPS gives information of only surface chemical composition up to 5-10 nm and bulk chemical
composition of TiO2 was preserved as confirmed by XRD analysis and Raman spectra. For the
fibrous red P@TiO2 the XPS peak position in O1s region was found at relatively higher BE
532.0 and 533.5 eV again due to lattice O atoms bonded with P coordinated Ti and adventitious
oxygen (Figure S5d). HR-XPS scan of black P in P2p region gave two peaks located at 130.9
and 134.5 eV corroborated to contribution from P2p of P atom in the sheets and oxidized P
(PxOy) respectively (Figure S5e).17
After deposition of black P on the TiO2 nanotube membranes
the intensity of P 2p peak component at 130.4 eV was diminished which demonstrate higher
degree of oxidation of P in black P@TiO2.12
Further, pristine fibrous red P show only one peak
at BE 134.9 in P2p region due to P atoms in fibrous P and absence of any peak corresponding
to P-O suggest better stability of fibrous red P than black P (Figure S5f), possibly caused by the
structural preference of black P reacting with air. The peak position and intensity of P2p peak
remains the same in fibrous red P@TiO2 revealing the unaffected chemical nature of fibrous
red P deposited on TiO2 (Figure S5f). Additionally, HR-XPS of pristine black P and black
P@TiO2 show I3d (I3d5/2 BE 619.6 and I3d3/2 BE 631.7) and Sn3d (Sn3d3/2 BE 488.1 and
Sn3d1/2 BE 496.6) peaks which was originated from SnI4, used as transporting materials for
vapor deposition (Figure S6).
10. S-10
Figure S5. Core level HR-XPS spectra of TiO2 and black P@TiO2 a) in Ti2p region, b) in Ti2p region, c) O1s
region and HR-XPS spectra of TiO2 fibrous red P and fibrous red P@TiO2 d) in O1s region, e) in P 2p region, f)
in P 2p region.
11. S-11
Figure S6. XPS elemental survey scan of a) black P, TiO2, black P@TiO2, b) fibrous red P, TiO2, fibrous red
P@TiO2, and HR-XPS spectra of black P and black P@TiO2 c) in Sn3d region and d) in I3d region showing
presence of Sn and I as mass transporting agents. Color: black P (black), TiO2 (red), black P@TiO2 (blue), fibrous
red P (olive), fibrous red P@TiO2 (magenta).
2.6 Calculation of Efficiencies:
To discern materials/interface performance of materials, diagnostic efficiencies of materials
were calculated.
Applied Bias Photon-to-current Efficiency (ABPE%)
Since external bias is applied in photoelectrochemical measurements, the electrical energy must
be subtracted during efficiency calculation. Applied Bias Photon-to-current Efficiency
(ABPE%), which demonstrate photo-conversion efficiency under applied bias conditions and
provides information of materials system/interface performance, was determined by plotting a
graph between ABPE% at different applied voltage on a reversible hydrogen electrode (RHE)
scale. To ABPE% was calculated by using following expression:
𝐴𝐵𝑃𝐸 (%) = [𝐽 (𝑚𝐴 𝑐𝑚−2) ·
1.23−𝑉𝑏
𝑃(𝑚𝑊 𝑐𝑚−2)
] · 100 (1)
Where, J is the current density, Vb is applied voltage at RHE scale and P is power density of the
incident light.
12. S-12
The applied voltage on Ag/AgCl scale was converted to RHE scale by using following
expression:
𝑅𝐻𝐸 = 𝑉𝐴𝑔/𝐴𝑔𝐶𝑙 + 0.059 𝑝𝐻 + 𝑉𝐴𝑔/𝐴𝑔𝐶𝑙
0
(2)
Where 𝑉𝐴𝑔/𝐴𝑔𝐶𝑙
0
= 0.197 V.
The optimum ABPE% for TiO2, black P, black P@TiO2, fibrous red P and fibrous red P@TiO2
was calculated to be 0.07, 0.03, 0.03, 0.07 and 0.20 respectively (Figure 8d).
Incident photon-to-current efficiency (IPCE%)
Incident photon-to-current efficiency (IPCE) also referred as external quantum efficiency
(EQE) measured at fixed incident wavelengths to evaluate performance of a photoelectrode for
water splitting (Figure S7d). The IPCE is defined as the number of photogenerated charge
carriers per incident photon flux as a function of wavelength contributing to the photocurrent.
The IPCE% of materials were calculated at an applied bias of +0.6 V vs Ag/AgCl (1.23 V vs
RHE, thermodynamic water splitting potential) using 420, 505, 580, 620 nm wavelength LEDs
having 21.00 mW cm-2
power density at the surface of samples. IPCE% was calculated using
the following expression.
𝐼𝑃𝐶𝐸 (%) = [
1240.𝐽 (𝑚𝐴 𝑐𝑚−2)
λ (nm).P (𝑚𝑊 𝑐𝑚−2).
] · 100 (3)
Where, J is photocurrent density, λ is wavelength of incident light in nm and P is the power
density of incident light.
The IPCE action spectra of samples is given in Figure S7d. The calculated value of IPCE% at
420, 505, 580 and 620 nm for TiO2 (0.20, 0.16, 0.11, 0.08), black P@TiO2 (0.66, 0.39, 0.16 and
0.11) and fibrous red P@TiO2 (1.30, 0.43, 0.23 and 0.02) respectively.
Absorbed photon-to-current efficiency (APCE%)
Absorbed photon-to-current efficiency (APCE) is also referred as internal quantum efficiency
(IQE) (Figure S7d). Since IPCE measurements demonstrate incident photons conversion
efficiency and loss of photon being unabsorbed by the materials is not considered during
calculation. A parameter of efficiency which takes unabsorbed photons into account should be
used. So, APCE which defines the photocurrent collected per incident photon absorbed seem
to be a suitable parameter to designate performance of devices. The APCE% can be calculated
by following formulas:
APCE% = (IPCE/LHE) x 100 (4)
Where, LHE is light harvesting efficiency or absorptance which is numbers of electron hole
pairs produced per incident photon flux. Considering each absorbed photon produces equal
numbers of electron hole pairs, the value of LHE or absorptance can be calculated by Beer’s
law using following expression.
LHE or absorptance = (1-10-A
)
So
𝐴𝑃𝐶𝐸 (%) = [
1240.𝐽 (𝑚𝐴 𝑐𝑚−2)
λ (nm).P (𝑚𝑊 𝑐𝑚−2).(1−10−A)
] · 100 (5)
13. S-13
Where, J is photocurrent density, λ is wavelength of incident light in nm, P is the power density
of incident light, LHE is light harvesting efficiency and A is absorbance at measured
wavelength.
The calculated value of APCE% at 420, 505, 580 and 620 nm for TiO2 (0.28, 0.23, 0.16, 0.11),
black P@TiO2 (1.04, 0.67, 0.26 and 0.20) and fibrous red P@TiO2 (1.65, 0.57, 0.32 and 0.03)
respectively (Figure S7d).
Figure S7 Photocurrent density vs applied voltage plot for a) TiO2, b) black P@TiO2, b) fibrous red P@TiO2 under
dark (black), 420 (blue), 505 (green), 580 (yellow), 620 (red) nm wavelength LEDs (21.00 mW cm-2
) and d) IPCE
and APCE% TiO2 (black), black P@TiO2 (blue), fibrous red P@TiO2 (red).
Faradaic Efficiency (FE%)
Faradaic Efficiency (FE%) was determined to verify the generated photocurrent. It is originated
due to photoelectrochemical water splitting and not due the side reactions or photo-corrosion
of the electrodes. Faradaic Efficiency can be defined as ratio of observed hydrogen in
experimental condition divided by the theoretically evolved H2 calculated from photocurrent
density.
𝐹𝑎𝑟𝑎𝑑𝑎𝑖𝑐 𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 (%) = [
𝐸𝑥𝑝𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙 𝑔𝑎𝑠 𝑒𝑣𝑜𝑙𝑢𝑡𝑖𝑜𝑛 (𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑑 𝐻2)
𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝐻2 𝑔𝑎𝑠 𝑒𝑣𝑜𝑙𝑢𝑡𝑖𝑜𝑛 (𝑏𝑎𝑠𝑒𝑑 𝑜𝑛 𝑝ℎ𝑜𝑡𝑜𝑐𝑢𝑟𝑟𝑒𝑛𝑡)
] · 100 (6)
𝐹𝑎𝑟𝑎𝑑𝑎𝑖𝑐 𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 (%) = [
𝐻2 𝑒𝑣𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑑 (𝑚𝑜𝑙)
𝐽 (𝐴 𝑐𝑚−2).𝐴 (𝑐𝑚2).𝑇 (𝑠𝑒𝑐)
2.𝑒 (𝐶).𝑁𝐴 (𝑚𝑜𝑙−1)
] · 100 (7)
14. S-14
Where, J is the photocurrent density (A cm-2
), A is the irradiation area of the photoelectrode
(cm2
), T is time of measurement (seconds), e is the charge of an electron (1.602 x 10-19
C) and
NA is the Avogadro number (6.02 x 1023
mol-1
), the amount of hydrogen generated during PEC
is expressed in moles.
For the measurements of evolved hydrogen, a three electrode H-cell was used and produced
hydrogen at Pt cathode was analyzed by gas chromatography using a PDD detector (Figure S8).
The experimental rate of hydrogen evolution per cm2
was found to be 1.37, 3.38 and 8.15 for
TiO2, black P@TiO2 and fibrous red P@TiO2, respectively. Further, calculated Faradaic
efficiency for TiO2, black P@TiO2 and fibrous red P@TiO2 was calculated to be 33.41, 90.61
and 72.83 respectively (Figure S9, Table S3). The obtained faradaic efficiencies demonstrate
populated side reaction and photo-corrosion of TiO2 electrode while black P@TiO2 shows
excellent FE% which demonstrates true origin of photocurrent from water splitting reaction.
Furthermore, to validate origin of photocurrent due to water splitting at anode not because of
self oxidation of photoanode materials, oxygen concentration on black P@TiO2 photoanode
was also determined before reaction and after reaction. The gaseous sample was analyzed using
GC-PDD equipped with Porapak Q column and Mol Sieve column. After 1 h the GC
chromatogram of product clearly demonstrate significantly increased oxygen peak
area/concentration. The increase peak area of oxygen collected at the photoanode suggest the
origin of photocurrent/hydrogen at counter electrode from water splitting (Figure S10 a and b).
Figure S8. GC chromatogram of photoelectrochemically evolved H2 collected at the Pt counter electrode.
15. S-15
Figure S9. Graph of amount of H2 evolved during PEC measurements (AM1.5 G) and corresponding Faradaic
efficiencies.
Table S3. Experimentally observed amount of H2 and theoretically calculated H2 in PEC measurements and
corresponding Faradaic efficiencies.
Sample H2 evolved (µmol
h-1
cm-2
)
Theoretical H2
(µmol h-1
cm-2
)
Faradaic Efficiency (%)
TiO2 1.37 4.10 33.41
black P@TiO2 3.38 3.73 90.61
fib. red P@TiO2 8.15 11.193 72.83
16. S-16
Figure S10. GC chromatogram of gaseous sample collected at black P@TiO2 photoanode (a) before photoreaction
after purging N2 for 30 min and (b) after 1 h photoreaction under AM1.5 G irradiation.
2.7 Electrochemical characterization of phosphorus allotrope@TiO2 membranes
Charge transfer resistance (RC) at the semiconductor electrolyte interface (SEI), charge
transport resistance (RT) and space-charge capacitance (CSC) were determined using
electrochemical impedance spectroscopy (EIS) under AM1.5 G irradiation as well as under
dark conditions (Figure S12a). EIS was performed at room temperature in a sodium sulfate
electrolyte at pH 7 and at a potential of -0.4 V vs Ag/AgCl in a frequency range of 10 Hz and
105 Hz. EIS Nyquist plots, obtained under AM1.5 G illumination condition, for blank TiO2,
fibrous red P, fibrous red P@TiO2, black P and black P@TiO2 are shown Figure S12 and under
dark conditions in Figure S13. Generally larger diameters of the Nyquist plots obtained under
dark conditions confirm a higher charge transfer resistance in dark. From Nyquist plotting under
irradiation an equivalent circuit diagram shown in Figure S12c could be obtained. As mentioned
in the equivalent circuit, RS, RC, RT, CSC and CH are electrolyte resistance, charge transfer
resistance, charge transport resistance, space charge capacitance, and electrochemical double-
layer capacitance, respectively. The equivalent circuit also comprises of a constant phase
element, Q, with coefficient n. Resistive circuit elements, RS, RC, are RT are independent of
frequency and have the same magnitude as the resistances itself. The frequency-dependent
impedances due to capacitances (𝒁_𝑪𝐒𝐂 and 𝒁_𝑪𝐇) and the constant phase element (𝒁_𝑸) are
given by eqt. (8) to (10).
17. S-17
𝒁𝑪𝐒𝐂
=
1
𝒊 · (2𝝅𝒇) · 𝑪𝐒𝐂
(8)
𝒁_𝑪𝐇 =
1
𝒊·(2𝝅𝒇)·𝑪𝐇
(9)
𝒁_𝑸1 =
1
𝑖 ∙ (2𝜋𝑓) ∙ 𝐶𝑆𝐶
(10)
𝒁 = 𝑹𝐒 + 𝑹𝐂 + 𝑹𝐂𝐓 + 𝒁_𝑪 𝐒𝐂 + 𝒁_𝑪𝐇 + 𝒁𝑸 (11)
𝝉 = 𝑹𝐂 · 𝑪𝐒𝐂 (12)
In eqt. (8) to (11), 𝑖 = √−1, 𝒁 is the total impedance of the system. The magnitude of 𝒁 is the
sum of impedance of all circuit elements and given by eqt. (11). The values of the circuit
elements are obtained by fitting 𝒁 with experimentally obtained Nyquist plots, and are listed in
Table S4. RC (i.e. 200 Ω) of blank TiO2 is much higher than those for fibrous red P, fibrous red
P@TiO2, black P, black P@TiO2. Also notable is that the smallest RC is of fibrous red P. Alike
RC, RT of the blank TiO2 is also the highest among the sample studied, with black P being an
exception. Recombination lifetime (𝝉, calculated using eqt. (12)) values are generally similar,
with blank TiO2 exhibiting the longest recombination lifetime (i.e. 2.8 µs) and fibrous red
P@TiO2 exhibiting the shortest lifetime (i.e. 1.7 µs). The lower recombination lifetimes of the
semiconductor blends are expected because of interfacial defects, which may be caused by
recombination effects.
1
𝑪𝐬𝐜
2
=
𝟐
𝒆𝜺0𝜺𝒓𝑵𝑫
{(𝑽 − 𝑽𝑭𝑩) −
𝒌𝑻
𝒆
} (13)
𝑁𝑑 =
2
𝒆𝜺0𝜺𝒓
{
𝑑𝑉
𝑑𝐶𝑆𝐶
2 } (14)
Carrier concentration (ND) and flat band potential (VFB) values were calculated using Mott–
Schottky analysis as described by eqt. (13) and eqt. (14), wherein 𝜺𝐫 is the semiconductor
dielectric constant; 𝜺𝐫 of fibrous red P and black P are expected to be 8.5;18
and blank TiO2 as
30,19
and dielectric constant of the blends of black P and TiO2 (black P@TiO2) as well as fibrous
red P and TiO2 (fibrous red P/TiO2) are expected to be an intermediate value of 15. 𝜺0 is the
vacuum permittivity (8.854 ×10−12
F m−1
); k is the Boltzmann constant (1.381 ×10−23
J K−1
); T
18. S-18
is the temperature in (298 K); e is the electron charge (1.602 ×10−19
C); and V is the applied
potential. ND of the samples were obtained using eqt. (12), where slopes of the Mott-Schottky
plots (Figure S12b) were factored into. Positive slopes indicate n-type conductivity and
electrons as the majority carrier. The n-type slope in Mott-Schottky measurements for fibrous
red P and black P was attributed to the contribution in charge transport from underlying compact
TiO2 used during measurements; note that pristine fibrous red P and black P graphs are less
steep compared to pristine TiO2. We note p-type behaviour from UPS measurements, which is
considered to the actual behaviour of the fibrous red P and black P. The values of ND are
indicated within the plot. 𝑽𝐅𝐁 was determined from the intersection of the slope of the Mott-
Schottky’s plot with the horizontal axis, which denotes potential with respect to Ag/AgCl. 𝑽𝐅𝐁
values for TiO2, fibrous red P, black P, fibrous red P@TiO2 and black P@TiO2 was calculated
to be to be -0.70, -0.37, -0.56, -0.54 and -0.66 V vs Ag/AgCl respectively (Figure S12b).
Interestingly, ND of blank TiO2 is the least among the samples while its 𝑽𝐅𝐁 is the most negative
as well. In photocatalysis, the band potential is usually expressed at the scale of vacuum energy
level (Evacuum). So, we have first converted the value of flat band potential from Ag/AgCl scale
to RHE (reversible hydrogen electrode) followed by conversion to vacuum level by following
equation:
𝐸(𝑅𝐻𝐸) = 𝐸𝐴𝑔/𝐴𝑔𝐶𝑙 + 0.059 𝑝𝐻 + 𝐸𝐴𝑔/𝐴𝑔𝐶𝑙
(15)
𝐸𝑣𝑎𝑐𝑢𝑢𝑚 = −(𝐸(𝑅𝐻𝐸) + 4.5)
(16)
Where, Eo
Ag/AgCl = 0.199 V at 25 °C, EAg/AgCl is working potential and Evacuum (eV) is the potential
at vacuum scale. From the eqt. (15) and (16) the position of flat band potential of TiO2, fibrous
red P, black P, fibrous red P@TiO2 and black P@TiO2 was estimated to be -4.00, -4.33, -4.14,
-4.16 and -4.04 eV respectively.
Figure S11. Photocurrent density vs applied voltage plot at 425 nm wavelength for a) black P b) fibrous red P.
19. S-19
Figure S12. a) Experimental and fitted EIS Nyquist plots of blank TiO2, fibrous red P, fibrous red P@TiO2, black
P and black P@TiO2 under AM1.5 G irradiation b) Mott Schottky plots of fibrous red P, fibrous red P@TiO2,
black P, black P@TiO2 and blank TiO2. VFB and ND are mentioned within the plot. c) Equivalent circuit of EIS
data. Color: TiO2 (black), fibrous red P (red), fibrous red P@TiO2 (brown), black P (blue) and black P@TiO2 (light
green).
Figure S13. Nyquist plots of fibrous red P, fibrous red P@TiO2, black P, black P@TiO2 and blank TiO2 under
dark conditions.
20. S-20
Table S4. Values of RS, RC, RT, CSC, CH, Q and n, obtained by fitting the Nyquist plots to the equivalent circuit.
Sample RS
(Ω
)
CSC
(F)
RT
(Ω
)
CH
(F)
RC
(Ω
)
Q
(F.s-1 + n
)
n τ
(µs)
TiO2 9 1.00x10-7
28 2.20x10-5
200 6.00x10-5
0.57 2.8
fibrous red P 5 1.20x10-8
18 1.90x10-5
1 1.55x10-4
0.55 2.2
fib. red
P@TiO2
12 8.10x10-8
21 1.70x10-5
70 1.30x10-4
0.57 1.7
black P 5 3.10x10-8
40 1.25x10-5
50 3.65x10-5
0.52 1.3
black P@TiO2 7 1.10x10-7
22 1.60x10-5
15 2.15x10-4
0.51 2.4
21. S-21
2.8 Kelvin Probe Force Microscopy (KPFM) Measurement
To understand the mechanism of charge carrier transport and verify successful heterojunction
formation between phosphorous materials (black P and fibrous red P) and TiO2 nanostructures,
change in surface potential (SP) was determined using Kelvin Probe Force Microscopy (KPFM)
under dark and irradiation conditions (Figure S14). The surface topographical AFM image of
TiO2, black P, black P@TiO2, fibrous red P and fibrous red P@TiO2 samples exhibit rough
surface features (Figure S14 a-e). The surface potential map of samples under dark condition,
450 and 635 nm irradiation are given in Figure S13a-e. The surface potential (SP) map of bare
TiO2 displayed nonuniform charge distribution due to the uneven morphology of TiO2
nanotubes, while, SP distribution of pristine black P and fibrous red P and hybrids were
comparatively uniform. The hybrid materials (black P@TiO2 and fibrous red P@TiO2)
displayed intermediate SP distribution. Under dark condition, the SP map image of bare TiO2
samples show bright contrast in comparison to pristine black P and fibrous red P which
demonstrates electron rich surface of n-type TiO2 nanotubes. However, SP map of hybrid
materials show slightly increased contrast in comparison to pristine materials due to reduced
surface charge, suggesting a transfer of electronic charge from the surface of TiO2 due to the
formation of heterojunction. Further, after illumination with 450 nm laser, the contrast of red
regions was further increased for all samples which was corroborated due to the transfer of
photogenerated electrons on the surface phosphorous to TiO2’s surface. The hybrid materials
(particularly black P@TiO2) displayed the highest change in SP which clearly verifies
heterojunction formation between the materials leading to improved charge carrier generation
under illuminated condition. Further, under 635 nm illumination similar pattern was followed
suggesting improved charge carrier creation and separation in hybrid P@TiO2 heterojunction
even at a higher wavelength.
The measured surface potential distribution or contact potential difference (CPD) for TiO2,
black P, black P@TiO2, fib. red P and fib. red P@TiO2 under dark condition was found to be
+36, +86, +39, +16 and +14 mV, respectively (Figure S14f-j). A slight negative shift of SP
distribution of hybrid samples in comparison to pristine phosphorous reveals a decrease in the
work function (WF) value. The observed decrease in WF suggest uplifting of Fermi level of
phosphorous in hybrid due to Fermi level alignment leading to the formation of heterojunction.
As expected after irradiation with 450 and 635 nm laser, the CPD of TiO2, black P, black
P@TiO2, fibrous red P and fibrous red P@TiO2 show a slight negative shift due to the
accumulation of photogenerated negative charge on the sample’s surface. Bare TiO2 and fibrous
red P displayed extremely small SP shift under 450 and 635 nm illumination which demonstrate
poorly generated charge in TiO2 and faster recombination rate in fibrous red P respectively.
While, black P show relatively higher shift under illumination conditions which might be due
to longer lifetime of generated charge on 2D phosphorous structure. A similar pattern was
followed for fibrous P@TiO2 and black P@TiO2 heterojunction which demonstrate visible
responsive nature of hybrid materials (Figure S14).
22. S-22
Figure S14. Topographical AFM images and surface potential map of a) TiO2 nanotubes, b) black P, c) fibrous
red P, d) black P@TiO2, e) fibrous red P@TiO2 under dark, 450 and 635 nm illumination conditions and e) surface
potential distribution of bare TiO2 nanotubes, black P, fibrous red P, black P@TiO2, fibrous red P@TiO2, samples
deposited on FTO under dark (black), 450 nm (red) and 635 nm (green) illumination condition.
23. S-23
Figure S15. XPS valence band spectra of TiO2. The point of intersection display position of valence band maxima
(VBmax) below Fermi level.
Figure S16. Photograph of photoelectrochemical water splitting cell irradiated under 505 nm LED.
24. S-24
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