Photocatalytic Mechanism Control and Study of Carrier Dynamics in CdS@C3N5 Core–Shell Nanowires
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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.
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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.
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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.
Nanostructured composite materials for CO2 activation
This document discusses nanostructured composite materials for CO2 activation, specifically for the photocatalytic reduction of CO2 to valuable products. It provides background on the increasing energy crisis and climate change caused by fossil fuel use. It then summarizes the basic principles and challenges of using semiconductor photocatalysts for CO2 reduction, including appropriate band gap positions and preventing electron-hole recombination. The document discusses various approaches to overcoming these challenges, such as forming heterojunction composites and using co-catalysts to facilitate charge separation and transfer.
Flexible and Ultrasoft Inorganic 1D Semiconductor and Heterostructure Systems...
Low dimensionality and high flexibility are key demands for flexible electronic semiconductor devices. SnIP, the first atomic-scale double helical semiconductor combines structural anisotropy and robustness with exceptional electronic properties. The benefit of the double helix, combined with a diverse structure on the nanoscale, ranging from strong covalent bonding to weak van der Waals interactions, and the large structure and property anisotropy offer substantial potential for applications in energy conversion and water splitting. It represents the next logical step in downscaling the inorganic semiconductors from classical 3D systems, via 2D semiconductors like MXenes or transition metal dichalcogenides, to the first downsizeable, polymer-like atomic-scale 1D semiconductor SnIP. SnIP shows intriguing mechanical properties featuring a bulk modulus three times lower than any IV, III-V, or II-VI semiconductor. In situ bending tests substantiate that pure SnIP fibers can be bent without an effect on their bonding properties. Organic and inorganic hybrids are prepared illustrating that SnIP is a candidate to fabricate flexible 1D composites for energy conversion and water splitting applications. SnIP@C3N4 hybrid forms an unusual soft material core–shell topology with graphenic carbon nitride wrapping around SnIP. A 1D van der Waals heterostructure is formed capable of performing effective water splitting.
Photo-induced reduction of CO2 using a magnetically separable Ru-CoPc@TiO2@Si...
An efficient photo-induced reduction of CO2 using magnetically separable Ru-CoPc@TiO2@SiO2@Fe3O4
as a heterogeneous catalyst in which CoPc and Ru(bpy)2phene complexes were attached to a solid
support via covalent attachment under visible light is described. The as-synthesized catalyst was characterized
by a series of techniques including FTIR, UV-Vis, XRD, SEM, TEM, etc. and subsequently tested for
the photocatalytic reduction of carbon dioxide using triethylamine as a sacrificial donor and water as a
reaction medium. The developed photocatalyst exhibited a significantly higher catalytic activity to give a
methanol yield of 2570.78 μmol per g cat after 48 h.
nl504051x
This document summarizes research on tuning the bandgap of silicon quantum dots (SiQDs) through surface functionalization with conjugated organic ligands. Computational modeling predicted that attaching triphenylamine-based ligands to the SiQD surface via conjugated vinyl linkages would result in a type-II energy level alignment and red-shift the photoluminescence by 259 nm (0.24 eV). Experimental results showed a 70 nm red-shift in photoluminescence of SiQDs functionalized with the designed triphenylamine ligand compared to decyl-capped controls, supporting the computational predictions. Characterization with FT-IR and XPS confirmed successful surface functionalization while minimizing oxidation. This research demonstrates an effective
Air- and water-stable halide perovskite nanocrystals protected with nearly-mo...
Halide perovskites are exciting candidates for broad-spectrum photocatalysts but have the problem of ambient stability. Protective shells of oxides and polymers around halide perovskite nano- and micro-crystals provide a measure of chemical and photochemical resilience but the photocatalytic performance of perovskites is compromised due to low electron mobility in amorphous oxide or polymer shells and rapid charge carrier recombination on the surface. Herein an in situ surface passivation and stabilization of CsPbBr3 nanocrystals was achieved using monolayered graphenic carbon nitride (CNM). Extensive characterization of carbon nitride protected CsPbBr3 nanocrystals (CNMBr) indicated spherical CsPbBr3 nanoparticles encased in a few nm thick g-C3N4 sheets facilitating better charge separation via percolation/tunneling of charges on conductive 2D nanosheets. The CNMBr core-shell nanocrystals demonstrated enhanced photoelectrochemical water splitting performance and photocurrent reaching up to 1.55 mA cm−2. The CNMBr catalyst was successfully deployed for CO2 photoreduction giving carbon monoxide and methane as the reaction products.
C3N5: A Low Bandgap Semiconductor Containing an Azo-linked Carbon Nitride Fra...
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.
Flexible and Ultrasoft Inorganic 1D Semiconductor and Heterostructure Systems...
Low dimensionality and high flexibility are key demands for flexible electronic semiconductor devices. SnIP, the first atomic‐scale double helical semiconductor combines structural anisotropy and robustness with exceptional electronic properties. The benefit of the double helix, combined with a diverse structure on the nanoscale, ranging from strong covalent bonding to weak van der Waals interactions, and the large structure and property anisotropy offer substantial potential for applications in energy conversion and water splitting. It represents the next logical step in downscaling the inorganic semiconductors from classical 3D systems, via 2D semiconductors like MXenes or transition metal dichalcogenides, to the first downsizeable, polymer‐like atomic‐scale 1D semiconductor SnIP. SnIP shows intriguing mechanical properties featuring a bulk modulus three times lower than any IV, III‐V, or II‐VI semiconductor. In situ bending tests substantiate that pure SnIP fibers can be bent without an effect on their bonding properties. Organic and inorganic hybrids are prepared illustrating that SnIP is a candidate to fabricate flexible 1D composites for energy conversion and water splitting applications. SnIP@C3N4 hybrid forms an unusual soft material core–shell topology with graphenic carbon nitride wrapping around SnIP. A 1D van der Waals heterostructure is formed capable of performing effective water splitting.
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Heterostructured nanocomposite tin phthalocyanine@mesoporous ceria (SnPc@CeO2...
Heterostructured tin phthalocyanine supported to mesoporous ceria was synthesized and used a
photocatalyst for CO2 reduction under visible light. The photoreduction CO2 activities of the
heterostructures were investigated in the presence of triethylamine as sacrificial agent. The developed
photocatalyst exhibited high catalytic activity for photoreduction of CO2 and after 24 hours of visible
light irradiation 2342 mmol g1 cat of methanol (fMeOH ¼ 0.0223 or 2.23%) and 840 mmol g1 cat of CO
(fCO ¼ 0.0026 or 0.26%) were obtained as the major reaction products. The methanol formation rate
(RMeOH) and CO formation rate (RCO) was found to be 97.5 mmol h1 g1 cat and 35.0 mmol h1 g1 cat
respectively. While under the identical experimental conditions mesoporous ceria (meso-CeO2) gave
only 316 mmol g1 cat of methanol (fMeOH ¼ 0.003 or 0.30%) and 126 mmol g1 cat CO (fCO ¼ 0.0004
or 0.04%) with product formation rate RMeOH ¼ 13.2 mmol h1 g1 cat and RCO ¼ 5.3 mmol h1 g1 cat.
Furthermore, the recovered catalyst showed consistent catalytic activity for at least five runs without any
significant loss in product yields
C3N5: A Low Bandgap Semiconductor Containing an Azo-Linked Carbon Nitride Fra...
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
C3N5: A Low Bandgap Semiconductor Containing an Azo-Linked Carbon Nitride Fra...
This document describes the synthesis and characterization of a novel carbon nitride framework called C3N5. C3N5 has a 3:5 carbon to nitrogen stoichiometry and is synthesized by thermal deammoniation of melem hydrazine. Characterization reveals that in the C3N5 polymer, two s-heptazine units are bridged together with an azo linkage. This azo linkage extends the π-conjugated network and lowers the electronic bandgap to 1.76 eV compared to 2.7 eV for g-C3N4. Due to its lower bandgap and electron-rich character, C3N5 shows improved performance for applications in solar cells, photocatalysis
Proton‐functionalized graphitic carbon nitride for efficient metal‐free disin...
This document summarizes a study on using proton-functionalized graphitic carbon nitride (P-CN) as a metal-free photocatalyst for disinfecting Escherichia coli (E. coli) bacteria under low-power light irradiation. P-CN demonstrated 100% disinfection of E. coli within 4 hours under 23W light bulb irradiation. Testing with scavengers showed that hydroxyl radicals (·OH) played a major role in the disinfection process, while superoxide (·O2-) played a minimal role. P-CN exhibited higher disinfection efficiency compared to unmodified graphitic carbon nitride, due to the introduction of protons enhancing conductivity and charge transfer in P-CN. This
Opv radiation
The document discusses the origin of radiation-induced degradation in polymer solar cells. It finds that charge accumulation at the interface is the primary reason for degradation, affected by the donor-acceptor mixing ratio in the bulk heterojunction. In situ measurements of polymer solar cell performance and recombination lifetimes under X-ray radiation show that devices with high acceptor concentrations experience a significant decrease in open-circuit voltage and fill factor due to radiation, while devices with low acceptor concentrations are more resistant to these changes. The findings provide a quantitative understanding and physical model of the degradation mechanism.
2021 influence of basic carbon additives on the electrochemical performance ...
This study investigates the effect of carbon surface basicity on the electrochemical performance and dynamic charge acceptance of lead-carbon batteries. Five activated carbons with different pH values ranging from 9.5 to 11.1 were prepared by ammonia and hydrogen gas treatments. Cyclic voltammetry showed that the hydrogen evolution reaction activity increased with higher carbon surface basicity. Testing of lead-carbon electrodes found a correlation between carbon pH and dynamic charge acceptance, with higher pH carbons showing improved charge currents and final dynamic charge acceptance. The carbon content also affected charge currents during simulated microcycles, demonstrating that surface chemistry and amount of carbon additive both influence the electrochemical properties and performance of lead-carbon batteries.
Boosting Photocatalytic Activity Using Carbon Nitride Based 2D/2D van der Waa...
The surging demand for energy and staggering pollutants in the environment have geared the scientific community to explore sustainable pathways that are economically feasible and environmentally compelling. In this context, harnessing solar energy using semiconductor materials to generate charge pairs to drive photoredox reactions has been envisioned as a futuristic approach. Numerous inorganic crystals with promising nanoregime properties investigated in the past decade have yet to demonstrate practical application due to limited photon absorption and sluggish charge separation kinetics. Two-dimensional semiconductors with tunable optical and electronic properties and quasi-resistance-free lateral charge transfer mechanisms have shown great promise in photocatalysis. Polymeric graphitic carbon nitride (g-C3N4) is among the most promising candidates due to fine-tuned band edges and the feasibility of optimizing the optical properties via materials genomics. Constructing a two-dimensional (2D)/2D van der Waals (vdW) heterojunction by allies of 2D carbon nitride sheets and other 2D semiconductors has demonstrated enhanced charge separation with improved visible photon absorption, and the performance is not restricted by the lattice matching of constituting materials. With the advent of new 2D semiconductors over the recent past, the 2D/2D heterojunction assemblies are gaining momentum to design high performance photocatalysts for numerous applications. This review aims to highlight recent advancements and key understanding in carbon nitride based 2D/2D heterojunctions and their applications in photocatalysis, including small molecules activation, conversion, and degradations. We conclude with a forward-looking perspective discussing the key challenges and opportunity areas for future research.
Photo-assisted oxidation of thiols to disulfides using cobalt ‘‘Nanorust’’ un...
Heterogeneous ‘‘Nanorust’’ containing cobalt oxide has been developed for the visible light assisted
oxidation of thiols to disulfides using molecular oxygen as an oxidant under alkaline free conditions and
therefore more environmentally friendly. Pyrolysis of heterogenized tetrasulfonated cobalt(II) phthalocyanine
(CoPcS) supported on mesoporous ceria (CeO2) transforms it into a novel heterogeneous ‘‘Nanorust’’
containing CoOx-C,N@CeO2 which exhibited higher catalytic activity than the homogeneous CoPcS as well
as the ceria immobilized CoPcS catalyst. Importantly, these catalysts could easily be recovered and recycled
for several runs, which makes the process greener and cost-effective.
Energy level tuning of cd se colloidal quantum dots in ternary 0d 2d-2d cdse ...
This document summarizes the energy level tuning of CdSe colloidal quantum dots (QDs) in a ternary 0D-2D-2D CdSe QD/B-rGO/O-gC3N4 photocatalyst system for enhanced hydrogen generation. Specifically, it discusses how the use of different thiol capping ligands on CdSe QDs results in shifts in the QD energy levels and band gaps. These ligand-specific CdSe QDs then exhibit trends in photocatalytic performance consistent with their respective measured energy and gap levels. Furthermore, it describes how an optimized CdSe QD is incorporated into a ternary composite with B-rGO and O-g
UndergradThesis
This document summarizes research on using boron-doped carbon nanotubes (B-CNTs) as a catalyst for oxygen dissociation in proton exchange membrane fuel cells (PEMFCs). Density functional theory (DFT) calculations were performed to model oxygen adsorption and dissociation on a (5,5) single-walled carbon nanotube (SWCNT) with one hexagon replaced by B3C3 (B3SWCNT). The nudged elastic band (NEB) method was used to calculate minimum energy reaction paths and activation barriers. The results show an average activation barrier of 1.01 eV for oxygen dissociation on the B3SWCNT, with the most favorable path having a barrier
One pot synthesis of chain-like palladium nanocubes and their enhanced electr...
One pot synthesis of chain-like palladium nanocubes and their enhanced electrocatalytic activity for fuel-cell applications
ncomms13869
N-doped graphene quantum dots (NGQDs) catalyze the efficient electrochemical reduction of carbon dioxide into multi-carbon hydrocarbons and oxygenates such as ethylene, ethanol, and n-propanol. The NGQDs achieve high total faradaic efficiencies of up to 90% for carbon dioxide reduction, with selectivities for ethylene and ethanol conversions reaching 45%. Control experiments confirm the NGQDs are responsible for catalyzing the reaction. Compared to undoped graphene quantum dots, the NGQDs have higher activity and selectivity for producing valuable fuel and chemical products from carbon dioxide due to the presence of pyridinic nitrogen defects introduced during synthesis.
Nanophotonic enhancement and improved electron extraction in perovskite solar...
While vertically oriented metal oxide nanowires have been intensely researched for use as electron transport layers (ETLs) in halide perovskite solar cells (HPSCs), horizontal nanowires (oriented roughly parallel to the substrate) have received much less attention despite their higher photonic strength due to overlapping electric and magnetic dipolar Mie resonance modes. Herein, we demonstrate the fabrication of an assembly of horizontally aligned TiO2 nanorods (HATNRs) on FTO substrates via a facile hydrothermal route. The HATNRs are employed as the ETL to achieve 15.03% power conversion efficiency (PCE) in HPSCs which is higher than the PCE of compact TiO2 based devices (10.12%) by a factor of nearly 1.5. A mixed halide, mixed cation organometal perovskite FA0.83MA0.17Pb(Br0.17I0.83)3 with optimized composition is used as the active layer. The excellent refractive index matching between the …
Nanophotonic enhancement and improved electron extraction in perovskite solar...
While vertically oriented metal oxide nanowires have been intensely researched for use as electron transport layers (ETLs) in halide perovskite solar cells (HPSCs), horizontal nanowires (oriented roughly parallel to the substrate) have received much less attention despite their higher photonic strength due to overlapping electric and magnetic dipolar Mie resonance modes. Herein, we demonstrate the fabrication of an assembly of horizontally aligned TiO2 nanorods (HATNRs) on FTO substrates via a facile hydrothermal route. The HATNRs are employed as the ETL to achieve 15.03% power conversion efficiency (PCE) in HPSCs which is higher than the PCE of compact TiO2 based devices (10.12%) by a factor of nearly 1.5. A mixed halide, mixed cation organometal perovskite FA0.83MA0.17Pb(Br0.17I0.83)3 with optimized composition is used as the active layer. The excellent refractive index matching between the perovskite and TiO2, coupled with strong Mie scattering in the nanorod geometry results in broadband near-zero backscattering and high forward scattering, upon coating of HATNRs with perovskite. The maximum suppression of backscattering is found at ∼600 nm. The HATNRs ETL also improves the extraction of electrons from the perovskite layer and results in superior blocking of carrier recombination at the perovskite layer/FTO interface.
TiO2-HfN Radial Nano-Heterojunction: A Hot Carrier Photoanode for Sunlight-Dr...
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.
Nanostructured composite materials for CO2 activation
This document discusses nanostructured composite materials for CO2 activation, specifically for the photocatalytic reduction of CO2 to valuable products. It provides background on the increasing energy crisis and climate change caused by fossil fuel use. It then summarizes the basic principles and challenges of using semiconductor photocatalysts for CO2 reduction, including appropriate band gap positions and preventing electron-hole recombination. The document discusses various approaches to overcoming these challenges, such as forming heterojunction composites and using co-catalysts to facilitate charge separation and transfer.
Flexible and Ultrasoft Inorganic 1D Semiconductor and Heterostructure Systems...
Low dimensionality and high flexibility are key demands for flexible electronic semiconductor devices. SnIP, the first atomic-scale double helical semiconductor combines structural anisotropy and robustness with exceptional electronic properties. The benefit of the double helix, combined with a diverse structure on the nanoscale, ranging from strong covalent bonding to weak van der Waals interactions, and the large structure and property anisotropy offer substantial potential for applications in energy conversion and water splitting. It represents the next logical step in downscaling the inorganic semiconductors from classical 3D systems, via 2D semiconductors like MXenes or transition metal dichalcogenides, to the first downsizeable, polymer-like atomic-scale 1D semiconductor SnIP. SnIP shows intriguing mechanical properties featuring a bulk modulus three times lower than any IV, III-V, or II-VI semiconductor. In situ bending tests substantiate that pure SnIP fibers can be bent without an effect on their bonding properties. Organic and inorganic hybrids are prepared illustrating that SnIP is a candidate to fabricate flexible 1D composites for energy conversion and water splitting applications. SnIP@C3N4 hybrid forms an unusual soft material core–shell topology with graphenic carbon nitride wrapping around SnIP. A 1D van der Waals heterostructure is formed capable of performing effective water splitting.
Photo-induced reduction of CO2 using a magnetically separable Ru-CoPc@TiO2@Si...
An efficient photo-induced reduction of CO2 using magnetically separable Ru-CoPc@TiO2@SiO2@Fe3O4
as a heterogeneous catalyst in which CoPc and Ru(bpy)2phene complexes were attached to a solid
support via covalent attachment under visible light is described. The as-synthesized catalyst was characterized
by a series of techniques including FTIR, UV-Vis, XRD, SEM, TEM, etc. and subsequently tested for
the photocatalytic reduction of carbon dioxide using triethylamine as a sacrificial donor and water as a
reaction medium. The developed photocatalyst exhibited a significantly higher catalytic activity to give a
methanol yield of 2570.78 μmol per g cat after 48 h.
nl504051x
This document summarizes research on tuning the bandgap of silicon quantum dots (SiQDs) through surface functionalization with conjugated organic ligands. Computational modeling predicted that attaching triphenylamine-based ligands to the SiQD surface via conjugated vinyl linkages would result in a type-II energy level alignment and red-shift the photoluminescence by 259 nm (0.24 eV). Experimental results showed a 70 nm red-shift in photoluminescence of SiQDs functionalized with the designed triphenylamine ligand compared to decyl-capped controls, supporting the computational predictions. Characterization with FT-IR and XPS confirmed successful surface functionalization while minimizing oxidation. This research demonstrates an effective
What's hot (19)
Heterostructured nanocomposite tin phthalocyanine@mesoporous ceria (SnPc@CeO2...
Heterostructured nanocomposite tin phthalocyanine@mesoporous ceria (SnPc@CeO2...
C3N5: A Low Bandgap Semiconductor Containing an Azo-Linked Carbon Nitride Fra...
C3N5: A Low Bandgap Semiconductor Containing an Azo-Linked Carbon Nitride Fra...
C3N5: A Low Bandgap Semiconductor Containing an Azo-Linked Carbon Nitride Fra...
C3N5: A Low Bandgap Semiconductor Containing an Azo-Linked Carbon Nitride Fra...
Proton‐functionalized graphitic carbon nitride for efficient metal‐free disin...
Proton‐functionalized graphitic carbon nitride for efficient metal‐free disin...
2021 influence of basic carbon additives on the electrochemical performance ...
2021 influence of basic carbon additives on the electrochemical performance ...
Boosting Photocatalytic Activity Using Carbon Nitride Based 2D/2D van der Waa...
Boosting Photocatalytic Activity Using Carbon Nitride Based 2D/2D van der Waa...
Photo-assisted oxidation of thiols to disulfides using cobalt ‘‘Nanorust’’ un...
Photo-assisted oxidation of thiols to disulfides using cobalt ‘‘Nanorust’’ un...
Energy level tuning of cd se colloidal quantum dots in ternary 0d 2d-2d cdse ...
Energy level tuning of cd se colloidal quantum dots in ternary 0d 2d-2d cdse ...
One pot synthesis of chain-like palladium nanocubes and their enhanced electr...
One pot synthesis of chain-like palladium nanocubes and their enhanced electr...
Nanophotonic enhancement and improved electron extraction in perovskite solar...
Nanophotonic enhancement and improved electron extraction in perovskite solar...
Nanophotonic enhancement and improved electron extraction in perovskite solar...
Nanophotonic enhancement and improved electron extraction in perovskite solar...
TiO2-HfN Radial Nano-Heterojunction: A Hot Carrier Photoanode for Sunlight-Dr...
TiO2-HfN Radial Nano-Heterojunction: A Hot Carrier Photoanode for Sunlight-Dr...
Nanostructured composite materials for CO2 activation
Nanostructured composite materials for CO2 activation
Flexible and Ultrasoft Inorganic 1D Semiconductor and Heterostructure Systems...
Flexible and Ultrasoft Inorganic 1D Semiconductor and Heterostructure Systems...
Photo-induced reduction of CO2 using a magnetically separable Ru-CoPc@TiO2@Si...
Photo-induced reduction of CO2 using a magnetically separable Ru-CoPc@TiO2@Si...
Similar to Photocatalytic Mechanism Control and Study of Carrier Dynamics in CdS@C3N5 Core–Shell Nanowires
Air- and water-stable halide perovskite nanocrystals protected with nearly-mo...
Halide perovskites are exciting candidates for broad-spectrum photocatalysts but have the problem of ambient stability. Protective shells of oxides and polymers around halide perovskite nano- and micro-crystals provide a measure of chemical and photochemical resilience but the photocatalytic performance of perovskites is compromised due to low electron mobility in amorphous oxide or polymer shells and rapid charge carrier recombination on the surface. Herein an in situ surface passivation and stabilization of CsPbBr3 nanocrystals was achieved using monolayered graphenic carbon nitride (CNM). Extensive characterization of carbon nitride protected CsPbBr3 nanocrystals (CNMBr) indicated spherical CsPbBr3 nanoparticles encased in a few nm thick g-C3N4 sheets facilitating better charge separation via percolation/tunneling of charges on conductive 2D nanosheets. The CNMBr core-shell nanocrystals demonstrated enhanced photoelectrochemical water splitting performance and photocurrent reaching up to 1.55 mA cm−2. The CNMBr catalyst was successfully deployed for CO2 photoreduction giving carbon monoxide and methane as the reaction products.
C3N5: A Low Bandgap Semiconductor Containing an Azo-linked Carbon Nitride Fra...
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.
Flexible and Ultrasoft Inorganic 1D Semiconductor and Heterostructure Systems...
Low dimensionality and high flexibility are key demands for flexible electronic semiconductor devices. SnIP, the first atomic‐scale double helical semiconductor combines structural anisotropy and robustness with exceptional electronic properties. The benefit of the double helix, combined with a diverse structure on the nanoscale, ranging from strong covalent bonding to weak van der Waals interactions, and the large structure and property anisotropy offer substantial potential for applications in energy conversion and water splitting. It represents the next logical step in downscaling the inorganic semiconductors from classical 3D systems, via 2D semiconductors like MXenes or transition metal dichalcogenides, to the first downsizeable, polymer‐like atomic‐scale 1D semiconductor SnIP. SnIP shows intriguing mechanical properties featuring a bulk modulus three times lower than any IV, III‐V, or II‐VI semiconductor. In situ bending tests substantiate that pure SnIP fibers can be bent without an effect on their bonding properties. Organic and inorganic hybrids are prepared illustrating that SnIP is a candidate to fabricate flexible 1D composites for energy conversion and water splitting applications. SnIP@C3N4 hybrid forms an unusual soft material core–shell topology with graphenic carbon nitride wrapping around SnIP. A 1D van der Waals heterostructure is formed capable of performing effective water splitting.
Metal-Free Sulfonate-Sulfate-Functionalized Carbon Nitride for Direct Convers...
Metal-free heteroatom-doped carbonaceous materials such as carbon nitride (CN) with secondary/tertiary nitrogen-rich catalytic centers as well as chemical and thermal resilience can potentially serve as catalysts for many organic reactions. However, because of the stable alternate Csp2–Nsp2 configuration of N-linked heptazine units (C6N7), the chemical modification of CN via doping and functionalization has been a critical challenge. Herein, we report an exceptional 9.2% sulfur content in CN with sulfonate/sulfate functional groups (CNS) via a one-step in situ synthesis approach. When used as a catalyst for the dehydration/hydration of glucose, CNS catalysts demonstrate a relatively high yield and selectivity toward levulinic acid, LLA, (≈48% yield with 57% selectivity) production. CNS’s high activity of direct conversion of glucose to LLA can be attributed to the synergistic catalytic effects of multiple sulfur functionalities, better dispersibility, and microstructural porosity. The synthesized CNS catalysts offer an energy efficient direct LLA production route to bypass the multistep process of sugar to LLA conversion.
Synthesis and Characterization of CuS/PVA Nanocomposite via Chemical method
Nanocomposite of copper sulfide (CuS /PVA) have been synthesized according to chemical
precipitation method at temperature 65ºC by simple reaction between copper acetate (Cu (ac)) and thiourea
(H2NCSNH2) at pH=9. Polyvinyl Alcohol (PVA), used as capping agent, was found to play a key role in the
confinement process.
The characterization of the product was done by UV-VIS spectroscopy, atomic force microscopy
(AFM) and x-ray diffraction (XRD). The X-ray diffraction showed the covellite phase of copper sulphides with
hexagonal crystal structure. The sizes of the sample as prepared were calculated by Debye-Scherrer formula
according to XRD spectra. A UV-VIS optical spectroscopy study was carried out to determine the band gap of
the nanocomposite CuS to be about 3.3 eV
Origami conductivity and structural stability
This document discusses molecular dynamics simulations of the ionic conductivity and structural stability of DNA origami under an electric field. The key findings are: (1) DNA origami expands under an applied electric field; (2) Ionic conductivity increases with higher Mg2+ concentration as it allows the DNA structure to open up more; and (3) Conductivity increases non-linearly with applied voltage. Simulations provide insight into how DNA origami may function as a bio-inspired nanopore device.
Unusual Electronic Properties of Cellulose Nanocrystals Conjugated to Cobalt ...
Octacarboxylated cobalt phthalocyanine (CoPc) was covalently conjugated to cellulose nanocrystals (CNCs) by employing an esterification protocol. Solid-state NMR, X-ray photoelectron spectroscopy (XPS), Raman, and infrared spectra were used to verify and study the nature of covalent attachment responsible for the immobilization of CoPc on the CNC surface. The covalent attachment was investigated from a theoretical simulation perspective using dispersion-corrected density functional theory (DFT) calculations, which verified the stable bond formation between CNC and CoPc. CoPc is an organic semiconductor with a high exciton binding energy, and CNCs are known to be insulating. Yet, Kelvin probe force microscopy (KPFM) indicated charge carrier generation and long-lived charge separation in the CNC–CoPc conjugate compared to pristine CoPc under visible light illumination. Such behavior is more typical of a semiconductor nanocomposite. The CNC–CoPc conjugate exhibited superior performance in the visible-light-driven surface photocatalytic reduction of 4-nitrobenzenethiol (4-NBT) to p,p′-dimercaptoazobenzene (DMAB) and photodegradation of rhodamine B.
A highly magnetized twin-jet base pinpoints a supermassive black hole
Supermassive black holes (SMBH) are essential for the production of jets in radio-loud active galactic nuclei (AGN). Theoretical
models based on (Blandford & Znajek 1977, MNRAS, 179, 433) extract the rotational energy from a Kerr black hole, which could
be the case for NGC1052, to launch these jets. This requires magnetic fields on the order of 103 G to 104 G. We imaged the vicinity
of the SMBH of the AGN NGC1052 with the Global Millimetre VLBI Array and found a bright and compact central feature that is
smaller than 1.9 light days (100 Schwarzschild radii) in radius. Interpreting this as a blend of the unresolved jet bases, we derive the
magnetic field at 1 Schwarzschild radius to lie between 200 G and 8:3 104 G consistent with Blandford & Znajek models.
Spherical array of annular ring microstrip antennas
The paper discusses the analytical study of spherical arrays of annular ring microstrip antenna (ARMSA) elements excited by electric dipole. A new empirical relation for calculating the nonunifrom current amplitude distributions of these elements has been obtained. The relation contains the information about the current amplitude factor ()Δ of the antenna elements of the spherical array. The narrow beamwidth and low side lobe levels can be obtain by choosing appropriate the current amplitude factor. It is found that for current amplitude factor ()5.0=Δ the radiation pattern have narrow beamwidth and low side lobe levels compared with uniform current distribution array. Circular polarization is realized by this study depends on the spherical array geometry. By using appropriate phase of each antenna elements in spherical arrays, radiation pattern is steered without change of gain and beamwidth.
Isolated Iridium Sites on Potassium-Doped Carbon-nitride wrapped Tellurium Na...
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.
Wereszczynski Molecular Dynamics
Molecular dynamics simulations allow researchers to model biomolecular mechanisms across wide ranges of time and length scales. The simulations integrate Newton's laws of motion over discrete timesteps to generate molecular trajectories. Force fields are used to define potential energies and forces in the system. While all-atom representation and applicability to diverse systems are advantages, the simulations are computationally expensive and limited in system size. The document provides examples of using molecular dynamics and small angle X-ray scattering to study protein folding, gene regulation, and protein structural ensembles.
Computation of electromagnetic fields scattered from dielectric objects of un...
Computation of electromagnetic fields scattered from dielectric objects of un...Alexander Litvinenko
Computational tools for characterizing electromagnetic scattering from objects with uncertain shapes are needed in various applications ranging from remote sensing at microwave frequencies to Raman spectroscopy at optical frequencies. Often, such computational tools use the Monte Carlo (MC) method to sample a parametric space describing geometric uncertainties. For each sample, which corresponds to a realization of the geometry, a deterministic electromagnetic solver computes the scattered fields. However, for an accurate statistical characterization the number of MC samples has to be large. In this work, to address this challenge, the continuation multilevel Monte Carlo (\CMLMC) method is used together with a surface integral equation solver.
The \CMLMC method optimally balances statistical errors due to sampling of
the parametric space, and numerical errors due to the discretization of the geometry using a hierarchy of discretizations, from coarse to fine.
The number of realizations of finer discretizations can be kept low, with most samples
computed on coarser discretizations to minimize computational cost.
Consequently, the total execution time is significantly reduced, in comparison to the standard MC scheme.ACS Boston 2015 poster final
1) The document reports on a study of the optical properties of binary CdSe and ternary alloyed CdSxSe1-x nanocrystals synthesized via a one-step hot injection colloidal approach.
2) Spectroscopic characterization of the nanocrystals showed prominent excitonic features in absorption spectra and single, narrow photoluminescence peaks devoid of surface state emissions. X-ray diffraction patterns confirmed a hexagonal wurtzite crystal structure.
3) At the single particle level, the ternary CdSxSe1-x nanocrystals exhibited higher 'on' time fractions and greater photostability than binary CdSe nanocrystals
jkps.66.323
This document summarizes a study measuring the transverse beam emittance at the Energy Selection System (ESS) of the KIRAMS-430 superconducting cyclotron. The researchers used a quadrupole variation method, where they varied the magnetic strength of a quadrupole magnet and measured the resulting beam size at a beam profile monitor. They analyzed the measurements using both linear matrix formalism and particle tracking simulations. The results from both analysis methods were consistent with emittances calculated from Monte Carlo simulations within the measurement uncertainties. The study demonstrated the feasibility of using the quadrupole variation method to characterize the beam quality at the ESS ion beamline.
Noble Metal Free, Visible Light Driven Photocatalysis Using TiO2 Nanotube Arr...
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.
Nanophotonic enhancement and improved electron extraction in perovskite solar...
While vertically oriented metal oxide nanowires have been intensely researched for use as electron transport layers (ETLs) in halide perovskite solar cells (HPSCs), horizontal nanowires (oriented roughly parallel to the substrate) have received much less attention despite their higher photonic strength due to overlapping electric and magnetic dipolar Mie resonance modes. Herein, we demonstrate the fabrication of an assembly of horizontally aligned TiO2 nanorods (HATNRs) on FTO substrates via a facile hydrothermal route. The HATNRs are employed as the ETL to achieve 15.03% power conversion efficiency (PCE) in HPSCs which is higher than the PCE of compact TiO2 based devices (10.12%) by a factor of nearly 1.5. A mixed halide, mixed cation organometal perovskite FA0.83MA0.17Pb(Br0.17I0.83)3 with optimized composition is used as the active layer. The excellent refractive index matching between the perovskite and TiO2, coupled with strong Mie scattering in the nanorod geometry results in broadband near-zero backscattering and high forward scattering, upon coating of HATNRs with perovskite. The maximum suppression of backscattering is found at ∼600 nm. The HATNRs ETL also improves the extraction of electrons from the perovskite layer and results in superior blocking of carrier recombination at the perovskite layer/FTO interface.
389418
The document describes the design and testing of a circular microstrip patch array antenna for C-band altimeter systems. It discusses using an array of four circular microstrip elements with equal size and spacing to achieve a gain of 12 dB. The antenna was simulated using HFSS and Microwave Office software. Comparison of simulated and measured results showed good agreement, achieving the design goals.
michele_romeo_phd_final_exam_presentation
This document describes a PhD research project focused on developing computational strategies using density functional theory (DFT) to simulate angle-resolved near-edge X-ray absorption fine structure (NEXAFS) spectra for molecules adsorbed on surfaces. The project will tune DFT methods to model NEXAFS spectra of molecules on surfaces, which can provide information about molecular orientation and interactions at interfaces. Systems to be studied include ethylene on silicon, pyridine on silicon, molecular oxygen on silver, and others. The approach involves DFT calculations of adsorbate structures, extracting clusters to model with finite methods, and simulating spectra and polarization dependence.
Determining a structure with electron crystallography - Overview of the paper...
The route to a solved structure (in this case Pb13Mn9O25) on the basis of precession electron diffraction, combined with HAADF-STEM, HRTEM, EELS and EDX is shown.
Summary of the paper "Solving the Structure of Li Ion Battery Materials with Precession
Electron Diffraction: Application to Li2CoPO4F"
Raman imaging -Anjali Devi J S
Raman imaging is application of Raman sprectroscopy for medical diagnostics and bioimaging. It emerges as a promising noninvasive imaging technique in biomedical research.
Similar to Photocatalytic Mechanism Control and Study of Carrier Dynamics in CdS@C3N5 Core–Shell Nanowires (20)
Air- and water-stable halide perovskite nanocrystals protected with nearly-mo...
Air- and water-stable halide perovskite nanocrystals protected with nearly-mo...
C3N5: A Low Bandgap Semiconductor Containing an Azo-linked Carbon Nitride Fra...
C3N5: A Low Bandgap Semiconductor Containing an Azo-linked Carbon Nitride Fra...
Flexible and Ultrasoft Inorganic 1D Semiconductor and Heterostructure Systems...
Flexible and Ultrasoft Inorganic 1D Semiconductor and Heterostructure Systems...
Metal-Free Sulfonate-Sulfate-Functionalized Carbon Nitride for Direct Convers...
Metal-Free Sulfonate-Sulfate-Functionalized Carbon Nitride for Direct Convers...
Synthesis and Characterization of CuS/PVA Nanocomposite via Chemical method
Synthesis and Characterization of CuS/PVA Nanocomposite via Chemical method
Unusual Electronic Properties of Cellulose Nanocrystals Conjugated to Cobalt ...
Unusual Electronic Properties of Cellulose Nanocrystals Conjugated to Cobalt ...
A highly magnetized twin-jet base pinpoints a supermassive black hole
A highly magnetized twin-jet base pinpoints a supermassive black hole
Spherical array of annular ring microstrip antennas
Spherical array of annular ring microstrip antennas
Isolated Iridium Sites on Potassium-Doped Carbon-nitride wrapped Tellurium Na...
Isolated Iridium Sites on Potassium-Doped Carbon-nitride wrapped Tellurium Na...
Computation of electromagnetic fields scattered from dielectric objects of un...
Computation of electromagnetic fields scattered from dielectric objects of un...
Noble Metal Free, Visible Light Driven Photocatalysis Using TiO2 Nanotube Arr...
Noble Metal Free, Visible Light Driven Photocatalysis Using TiO2 Nanotube Arr...
Nanophotonic enhancement and improved electron extraction in perovskite solar...
Nanophotonic enhancement and improved electron extraction in perovskite solar...
Determining a structure with electron crystallography - Overview of the paper...
Determining a structure with electron crystallography - Overview of the paper...
More from Pawan Kumar
Isolated Iridium Sites on Potassium-Doped Carbon-nitride wrapped Tellurium Na...
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...
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 ...
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 ...
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 ...
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...
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...
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...
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...
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...
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...
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...
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.
Pyrazino[2,3-g]quinoxaline core-based organic liquid crystalline semiconducto...
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 catalysis
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...
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...
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...
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...
This document summarizes a study that investigated copper single atom catalysts supported on two-dimensional carbon nitride materials for enhancing the electrochemical reduction of carbon dioxide to methane. Specifically, copper ions were incorporated into the nanoporous structures of poly(heptazine imide) and poly(triazine imide) using a room temperature ion exchange process. This allowed for high loading densities of isolated copper sites. The proximity of copper atoms within the nanopores was found to enable cooperative catalysis that boosted the selectivity and efficiency of the multi-electron conversion of CO2 to CH4. Density functional theory calculations helped explain how the copper-copper distance and coordination environment modulated the binding of reaction intermediates. Optimized copper loading in the
Bioinspired multimetal electrocatalyst for selective methane oxidation
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.
Radial Nano-Heterojunctions Consisting of CdS Nanorods Wrapped by 2D CN:PDI P...
Solar energy harvesting using semiconductor photocatalysis offers an enticing solution to two of the biggest societal challenges, energy scarcity and environmental pollution. After decades of effort, no photocatalyst exists which can simultaneously meet the demand for excellent absorption, high quantum efficiency and photochemical resilience/durability. While CdS is an excellent photocatalyst for hydrogen evolution, pollutant degradation and organic synthesis, photocorrosion of CdS leads to the deactivation of the catalyst. Surface passivation of CdS with 2D graphitic carbon nitrides (CN) such as g-C3N4 and C3N5 has been shown to mitigate the photocorrosion problem but the poor oxidizing power of photogenerated holes in CN limits the utility of this approach for photooxidation reactions. We report the synthesis of exfoliated 2D nanosheets of a modified carbon nitride constituted of tris-s-triazine (C6N7) linked pyromellitic dianhydride polydiimide (CN:PDI) with a deep oxidative highest occupied molecular orbital (HOMO) position, which ensures sufficient oxidizing power for photogenerated holes in CN. The heterojunction formed by the wrapping of mono-/few layered CN:PDI on CdS nanorods (CdS/CN:PDI) was determined to be an excellent photocatalyst for oxidation reactions including photoelectrochemical water splitting, dye decolorization and the photocatalytic conversion of benzyl alcohol to benzaldehyde. Extensive structural characterization using HR-TEM, Raman, XPS, etc., confirmed wrapping of few-layered CN:PDI on CdS nanorods. The increased photoactivity in CdS/CN:PDI catalyst was ascribed to facile electron transfer from CdS to CN:PDI in comparison to CdS/g-C3N4, leading to an increased electron density on the surface of the photocatalyst to drive chemical reactions.
More from Pawan Kumar (20)
Isolated Iridium Sites on Potassium-Doped Carbon-nitride wrapped Tellurium Na...
Isolated Iridium Sites on Potassium-Doped Carbon-nitride wrapped Tellurium Na...
Isolated Iridium Sites on Potassium-Doped Carbon-nitride wrapped Tellurium Na...
Isolated Iridium Sites on Potassium-Doped Carbon-nitride wrapped Tellurium Na...
Solar-Driven Cellulose Photorefining into Arabinose over Oxygen-Doped Carbon ...
Solar-Driven Cellulose Photorefining into Arabinose over Oxygen-Doped Carbon ...
Solar-Driven Cellulose Photorefining into Arabinose over Oxygen-Doped Carbon ...
Solar-Driven Cellulose Photorefining into Arabinose over Oxygen-Doped Carbon ...
Solar-Driven Cellulose Photorefining into Arabinose over Oxygen-Doped Carbon ...
Solar-Driven Cellulose Photorefining into Arabinose over Oxygen-Doped Carbon ...
Partial Thermal Condensation Mediated Synthesis of High-Density Nickel Single...
Partial Thermal Condensation Mediated Synthesis of High-Density Nickel Single...
Partial Thermal Condensation Mediated Synthesis of High-Density Nickel Single...
Partial Thermal Condensation Mediated Synthesis of High-Density Nickel Single...
Selective Cellobiose Photoreforming for Simultaneous Gluconic Acid and Syngas...
Selective Cellobiose Photoreforming for Simultaneous Gluconic Acid and Syngas...
Selective Cellobiose Photoreforming for Simultaneous Gluconic Acid and Syngas...
Selective Cellobiose Photoreforming for Simultaneous Gluconic Acid and Syngas...
Selective Cellobiose Photoreforming for Simultaneous Gluconic Acid and Syngas...
Selective Cellobiose Photoreforming for Simultaneous Gluconic Acid and Syngas...
Partial Thermal Condensation Mediated Synthesis of High-Density Nickel Single...
Partial Thermal Condensation Mediated Synthesis of High-Density Nickel Single...
Recent advancements in tuning the electronic structures of transitional metal...
Recent advancements in tuning the electronic structures of transitional metal...
Pyrazino[2,3-g]quinoxaline core-based organic liquid crystalline semiconducto...
Pyrazino[2,3-g]quinoxaline core-based organic liquid crystalline semiconducto...
Multifunctional carbon nitride nanoarchitectures for catalysis
Multifunctional carbon nitride nanoarchitectures for catalysis
Production of Renewable Fuels by the Photocatalytic Reduction of CO2 using Ma...
Production of Renewable Fuels by the Photocatalytic Reduction of CO2 using Ma...
Nanoengineered Au-Carbon Nitride Interfaces Enhance PhotoCatalytic Pure Water...
Nanoengineered Au-Carbon Nitride Interfaces Enhance PhotoCatalytic Pure Water...
Nanoengineered Au-Carbon Nitride Interfaces Enhance Photo-Catalytic Pure Wate...
Nanoengineered Au-Carbon Nitride Interfaces Enhance Photo-Catalytic Pure Wate...
Cooperative Copper Single Atom Catalyst in Two-dimensional Carbon Nitride for...
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Bioinspired multimetal electrocatalyst for selective methane oxidation
Bioinspired multimetal electrocatalyst for selective methane oxidation
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Authoring a personal GPT for your research and practice: How we created the Q...
Thematic analysis in qualitative research is a time-consuming and systematic task, typically done using teams. Team members must ground their activities on common understandings of the major concepts underlying the thematic analysis, and define criteria for its development. However, conceptual misunderstandings, equivocations, and lack of adherence to criteria are challenges to the quality and speed of this process. Given the distributed and uncertain nature of this process, we wondered if the tasks in thematic analysis could be supported by readily available artificial intelligence chatbots. Our early efforts point to potential benefits: not just saving time in the coding process but better adherence to criteria and grounding, by increasing triangulation between humans and artificial intelligence. This tutorial will provide a description and demonstration of the process we followed, as two academic researchers, to develop a custom ChatGPT to assist with qualitative coding in the thematic data analysis process of immersive learning accounts in a survey of the academic literature: QUAL-E Immersive Learning Thematic Analysis Helper. In the hands-on time, participants will try out QUAL-E and develop their ideas for their own qualitative coding ChatGPT. Participants that have the paid ChatGPT Plus subscription can create a draft of their assistants. The organizers will provide course materials and slide deck that participants will be able to utilize to continue development of their custom GPT. The paid subscription to ChatGPT Plus is not required to participate in this workshop, just for trying out personal GPTs during it.
Gadgets for management of stored product pests_Dr.UPR.pdf
Insectsplayamajorroleinthedeteriorationoffoodgrainscausingbothquantitativeandqualitativelosses
Wellprovedthatnogranariescanbefilledwithgrainswithoutinsectsastheharvestedproducecontainegg(or)larvae(or)pupae(or)adultinsectinthembecauseoffieldcarryoverinfestationwhichcannotbeavoidedindevelopingcountrieslikeIndia
Simpletechnologiesfortimelydetectionofinsectsinthestoredproduceandtherebyplantimelycontrolmeasures
Sexuality - Issues, Attitude and Behaviour - Applied Social Psychology - Psyc...
A proprietary approach developed by bringing together the best of learning theories from Psychology, design principles from the world of visualization, and pedagogical methods from over a decade of training experience, that enables you to: Learn better, faster!
Applied Science: Thermodynamics, Laws & Methodology.pdf
When I was asked to give a companion lecture in support of ‘The Philosophy of Science’ (https://shorturl.at/4pUXz) I decided not to walk through the detail of the many methodologies in order of use. Instead, I chose to employ a long standing, and ongoing, scientific development as an exemplar. And so, I chose the ever evolving story of Thermodynamics as a scientific investigation at its best.
Conducted over a period of >200 years, Thermodynamics R&D, and application, benefitted from the highest levels of professionalism, collaboration, and technical thoroughness. New layers of application, methodology, and practice were made possible by the progressive advance of technology. In turn, this has seen measurement and modelling accuracy continually improved at a micro and macro level.
Perhaps most importantly, Thermodynamics rapidly became a primary tool in the advance of applied science/engineering/technology, spanning micro-tech, to aerospace and cosmology. I can think of no better a story to illustrate the breadth of scientific methodologies and applications at their best.
Micronuclei test.M.sc.zoology.fisheries.
Current Ms word generated power point presentation covers major details about the micronuclei test. It's significance and assays to conduct it. It is used to detect the micronuclei formation inside the cells of nearly every multicellular organism. It's formation takes place during chromosomal sepration at metaphase.
Immersive Learning That Works: Research Grounding and Paths Forward
We will metaverse into the essence of immersive learning, into its three dimensions and conceptual models. This approach encompasses elements from teaching methodologies to social involvement, through organizational concerns and technologies. Challenging the perception of learning as knowledge transfer, we introduce a 'Uses, Practices & Strategies' model operationalized by the 'Immersive Learning Brain' and ‘Immersion Cube’ frameworks. This approach offers a comprehensive guide through the intricacies of immersive educational experiences and spotlighting research frontiers, along the immersion dimensions of system, narrative, and agency. Our discourse extends to stakeholders beyond the academic sphere, addressing the interests of technologists, instructional designers, and policymakers. We span various contexts, from formal education to organizational transformation to the new horizon of an AI-pervasive society. This keynote aims to unite the iLRN community in a collaborative journey towards a future where immersive learning research and practice coalesce, paving the way for innovative educational research and practice landscapes.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
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Targeting Hsp90 and its pathogen Orthologs with Tethered Inhibitors as a Diagnostic and Therapeutic Strategy for cancer and infectious diseases with Dr. Timothy Haystead.The binding of cosmological structures by massless topological defects
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
ESR spectroscopy in liquid food and beverages.pptx
With increasing population, people need to rely on packaged food stuffs. Packaging of food materials requires the preservation of food. There are various methods for the treatment of food to preserve them and irradiation treatment of food is one of them. It is the most common and the most harmless method for the food preservation as it does not alter the necessary micronutrients of food materials. Although irradiated food doesn’t cause any harm to the human health but still the quality assessment of food is required to provide consumers with necessary information about the food. ESR spectroscopy is the most sophisticated way to investigate the quality of the food and the free radicals induced during the processing of the food. ESR spin trapping technique is useful for the detection of highly unstable radicals in the food. The antioxidant capability of liquid food and beverages in mainly performed by spin trapping technique.
Compexometric titration/Chelatorphy titration/chelating titration
Classification
Metal ion ion indicators
Masking and demasking reagents
Estimation of Magnisium sulphate
Calcium gluconate
Complexometric Titration/ chelatometry titration/chelating titration, introduction, Types-
1.Direct Titration
2.Back Titration
3.Replacement Titration
4.Indirect Titration
Masking agent, Demasking agents
formation of complex
comparition between masking and demasking agents,
Indicators/Metal ion indicators/ Metallochromic indicators/pM indicators,
Visual Technique,PM indicators (metallochromic), Indicators of pH, Redox Indicators
Instrumental Techniques-Photometry
Potentiometry
Miscellaneous methods.
Complex titration with EDTA.
Direct Seeded Rice - Climate Smart Agriculture
Direct Seeded Rice - Climate Smart AgricultureInternational Food Policy Research Institute- South Asia Office
PPT on Direct Seeded Rice presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
Mending Clothing to Support Sustainable Fashion_CIMaR 2024.pdf
Ozturkcan, S., Berndt, A., & Angelakis, A. (2024). Mending clothing to support sustainable fashion. Presented at the 31st Annual Conference by the Consortium for International Marketing Research (CIMaR), 10-13 Jun 2024, University of Gävle, Sweden.
快速办理(UAM毕业证书)马德里自治大学毕业证学位证一模一样
学校原件一模一样【微信：741003700 】《(UAM毕业证书)马德里自治大学毕业证学位证》【微信：741003700 】学位证，留信认证（真实可查，永久存档）原件一模一样纸张工艺/offer、雅思、外壳等材料/诚信可靠,可直接看成品样本，帮您解决无法毕业带来的各种难题！外壳，原版制作，诚信可靠，可直接看成品样本。行业标杆！精益求精，诚心合作，真诚制作！多年品质 ,按需精细制作，24小时接单,全套进口原装设备。十五年致力于帮助留学生解决难题，包您满意。
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8.Isolation of pure cultures and preservation of cultures.pdf
Isolation of pure culture, its various method.
The debris of the ‘last major merger’ is dynamically young
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Randomised Optimisation Algorithms in DAPHNE
Slides from talk:
Aleš Zamuda: Randomised Optimisation Algorithms in DAPHNE .
Austrian-Slovenian HPC Meeting 2024 – ASHPC24, Seeblickhotel Grundlsee in Austria, 10–13 June 2024
https://ashpc.eu/
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aziz sancar nobel prize winner: from mardin to nobel
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Authoring a personal GPT for your research and practice: How we created the Q...
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Gadgets for management of stored product pests_Dr.UPR.pdf
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The binding of cosmological structures by massless topological defects
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ESR spectroscopy in liquid food and beverages.pptx
ESR spectroscopy in liquid food and beverages.pptx
Compexometric titration/Chelatorphy titration/chelating titration
Compexometric titration/Chelatorphy titration/chelating titration
Mending Clothing to Support Sustainable Fashion_CIMaR 2024.pdf
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8.Isolation of pure cultures and preservation of cultures.pdf
8.Isolation of pure cultures and preservation of cultures.pdf
GBSN - Biochemistry (Unit 6) Chemistry of Proteins
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The debris of the ‘last major merger’ is dynamically young
The debris of the ‘last major merger’ is dynamically young
Photocatalytic Mechanism Control and Study of Carrier Dynamics in CdS@C3N5 Core–Shell Nanowires
- 1. Photocatalytic Mechanism Control and Study of Carrier Dynamics in CdS@C3N5 Core–Shell Nanowires Kazi M. Alam, Charles E. Jensen, Pawan Kumar, Riley W. Hooper, Guy M. Bernard, Aakash Patidar, Ajay P. Manuel , Naaman Amer, Anders Palmgren, David N. Purschke, Narendra Chaulagain, John Garcia, Phillip S. Kirwin, Lian C.T. Shoute, Kai Cui, Sergey Gusarov, Alexander E. Kobryn, Vladimir K. Michaelis, Frank A. Hegmann, and Karthik Shankar* ACS Appl. Mater. Interfaces 2021, 13, 40, 47418–47439 https://doi.org/10.1021/acsami.1c08550
- 2. Figure 1. FESEM images of (a) pristine CdS nanowires (NWs), (b) CdS-MHP core–shell NWs formed by electrostatic wrapping of C3N5 around CdS NWs, and (c) CdS-MHPINS NWs formed by in situ growth of CdS/C3N5 heterostructures. The photographs of the materials are shown in the corresponding insets. HRTEM images showing (d, e) CdS crystal planes and a thin layer of surrounding C3N5 nanosheets in CdS-MHP and (f, g) CdS crystal planes and a thin layer of C3N5 nanosheets in CdS-MHPINS samples. EELS spectra of (h) CdS, (i) CdS-MHP, and (j) CdS-MHPINS showing energy loss peaks associated with constituent elements.
- 3. Figure 2. (a, c) X-ray diffractograms and DRS absorption spectra of pristine C3N5 bulk, pristine C3N5 nanosheet, pristine CdS nanowire, and heterojunctions of CdS with C3N5 nanosheets, respectively. (b, d) Raman spectra and steady-state photoluminescence spectra of pristine CdS nanowire and heterojunctions of CdS with C3N5 nanosheets, respectively.
- 4. Figure 3. FDTD electromagnetic simulation results for bare and C3N5 wrapped (2 nm thick) CdS nanowire of 200 nm length and 100 nm diameter. (a) Optical spectra (absorption, scattering, and extinction). (b–d) Electric field intensity profiles over xy, xz, and yz planes, respectively, for the bare CdS nanowire. (e–g) Electric field intensity profiles over xy, xz, and yz planes, respectively, for the C3N5 wrapped CdS nanowire. The electric field polarization direction is along the z axis in each and is indicated by yellow arrows. The nanowire is oriented vertically on an FTO substrate. The horizontal rectangle visible in the plots (c, d, f, and g) is the substrate.
- 5. Figure 4. (a) XPS elemental survey scan of CdS (black), C3N5 bulk (wine), C3N5 NS (cyan), CdS-MHP (red), and CdS-MHPINS (blue). HR- XPS spectra of (b) CdS, CdS-MHP, and CdS-MHPINS in the Cd 3d region; (c) CdS, CdS-MHP, and CdS-MHPINS in the S 2p region; (d) C3N5 bulk, C3N5 NS, CdS-MHP, and CdS-MHPINS in the C 1s region, (e) C3N5 bulk, C3N5 NS, CdS-MHP, and CdS-MHPINS in the N 1s region; and (f) CdS, CdS-MHP, and CdS-MHPINS in the O 1s region.
- 6. Figure 5. (a) 113Cd magic-angle spinning (MAS) Bloch decay NMR spectra of pristine CdS (top), CdS-MHP (middle), and CdS-MHPINS (bottom). (b) 113Cd cross-polarization magic-angle spinning (CPMAS) NMR spectra of pristine CdS (top), CdS-MHP (middle), and CdS- MHPINS (bottom). (c) 13C CPMAS NMR spectra of pristine C3N5 (top), CdS-MHP (middle), and CdS-MHPINS (bottom).
- 7. Figure 6. (a) −ΔE/Eref for CdS (black), CdS-MHP (red), and CdS-MHPINS (blue). The dark gray curves indicate biexponential fits to the data. Dashed vertical lines indicate times at which photoconductivity spectra were measured. The green line corresponds to tpp = 14 ps, while the magenta line indicates tpp = 154 ps after the onset of −ΔE/Eref. The fluence is 400 μJ/cm2 for all measurements, with a center wavelength of 410 nm and 100 fs duration. (b) Real (square) and imaginary (circle) photoconductivity spectra for the bare CdS nanowire sample taken at tpp = 14 ps (filled) and tpp = 154 ps (hollow). Real (solid line) and imaginary (dashed line) parts of the Drude–Smith model are shown as lines. (c) Same as (b), but for CdS-MHP. (d) Same as (b), but for CdS-MHPINS.
- 8. Figure 7. Photocatalytic test by RhB degradation experiment for pristine CdS, CdS-MHP, and CdS-MHPINS samples. (a) RhB degradation efficiency in the absence of any scavenger. (b) Comparative efficiencies for three photocatalysts in the absence of any scavenger and in the presence of electron and hole scavengers. Proposed photocatalytic mechanisms for (c) pristine CdS and (d) CdS-C3N5 composites.
- 9. Figure 8. Photocatalytic degradation experiments under AM1.5 G 1 sun simulated sunlight using 4-nitrophenol. (a) UV–vis absorption spectrum of bare 4-nitrophenol. Gradual evolution of UV–vis absorption spectra in the dark and under illumination for (b) pristine CdS, (c) CdS-MHP, and (d) CdS-MHPINS samples.
- 10. Figure 9. Side view of DFT optimized structures showing spatial distributions of molecular orbitals (HOMO–LUMO plots) for heterojunctions composed of two different CdS planes and single-layer C3N5. (a) Configuration I for CdS (100) plane and single-layer C3N5, (b) configuration II for CdS (100) plane and single-layer C3N5, (c) configuration I for CdS (110) plane and single-layer C3N5, and (d) configuration II for CdS (110) plane and single-layer C3N5. Cyan and magenta colors are for HOMO and LUMO surfaces, respectively. Cd, S, C, and N atoms are in red, yellow, gray, and blue colors, respectively.
- 11. Figure 10. Projected density of states (PDOS) of selected atoms for two different pristine CdS planes and their heterojunctions with single-layer C3N5. (a) Pristine CdS (100) plane, (b) configuration I for CdS (100) plane and single-layer C3N5, (c) configuration II for CdS (100) plane and single-layer C3N5, (d) pristine CdS (110) plane, (e) configuration I for CdS (110) plane and single-layer C3N5, and (f) configuration II for CdS (110) plane and single-layer C3N5. Cd, S, C, and N atoms are in wine, yellow, gray, and blue colors, respectively.