This document summarizes research on selectively dispersing and separating single-walled carbon nanotubes (SWNTs) using the biomolecule flavin mononucleotide (FMN) and various surfactants. The research shows that FMN forms helical assemblies around SWNTs that can be selectively replaced by surfactants such as sodium dodecyl sulfate or sodium cholate in a chirality-dependent manner. This allows for the enrichment of specific SWNT structures, with (8,6) SWNTs showing the strongest binding to FMN.
Air- and water-stable halide perovskite nanocrystals protected with nearly-mo...Pawan Kumar
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.
Highly Crystalline Surface Supported Metal Organic Thin Film Materials Based ...CrimsonpublishersPRSP
Highly Crystalline Surface Supported Metal Organic Thin Film Materials Based Heterojunctions for Triplet-Triplet Annihilation Upconversion by Shargeel Ahmad* in Peer Review Journal of Solar & Photoenergy Systems
Presentation presented at the Wroclaw meeting in the FICES COST program on september 10th, 2009.
Descibes results obtained by seeding supercontinuum generation.
TUNABLE BROADBAND ALL-DIELECTRIC PERFECT ABSORBER BASED ON PHASE CHANGE MATERIALoptljjournal
This work reported a polarization-independent, all-dielectric perfect absorber based on phase-change material. Broadband (in the wavelength range of 400-1000 nm) absorption of higher than 90% has been realized in our designed absorber. Moreover, absorption bandwidth and absorptivity can be tuned via structural parameters (such as the period, height and radius of nanopillars, the thicknesses of TiO2 and bottom GeTe films) and phase-change process. The underlying physical mechanism of the absorber is analyzed in detail. The proposed all-dielectric perfect absorber has potential applications in solar energy harvesting.
Perovskite material characterization and photovoltaic performance of planar s...Shaimum Shahriar
XRD, SEM, AFM, UV-Vis, PL, TRPL, XPS characterization of perovskite material, the 3D structure, and photovoltaic performance of planar perovskite solar cells.
Air- and water-stable halide perovskite nanocrystals protected with nearly-mo...Pawan Kumar
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.
Highly Crystalline Surface Supported Metal Organic Thin Film Materials Based ...CrimsonpublishersPRSP
Highly Crystalline Surface Supported Metal Organic Thin Film Materials Based Heterojunctions for Triplet-Triplet Annihilation Upconversion by Shargeel Ahmad* in Peer Review Journal of Solar & Photoenergy Systems
Presentation presented at the Wroclaw meeting in the FICES COST program on september 10th, 2009.
Descibes results obtained by seeding supercontinuum generation.
TUNABLE BROADBAND ALL-DIELECTRIC PERFECT ABSORBER BASED ON PHASE CHANGE MATERIALoptljjournal
This work reported a polarization-independent, all-dielectric perfect absorber based on phase-change material. Broadband (in the wavelength range of 400-1000 nm) absorption of higher than 90% has been realized in our designed absorber. Moreover, absorption bandwidth and absorptivity can be tuned via structural parameters (such as the period, height and radius of nanopillars, the thicknesses of TiO2 and bottom GeTe films) and phase-change process. The underlying physical mechanism of the absorber is analyzed in detail. The proposed all-dielectric perfect absorber has potential applications in solar energy harvesting.
Perovskite material characterization and photovoltaic performance of planar s...Shaimum Shahriar
XRD, SEM, AFM, UV-Vis, PL, TRPL, XPS characterization of perovskite material, the 3D structure, and photovoltaic performance of planar perovskite solar cells.
Study of highly broadening Photonic band gaps extension in one-dimensional Me...IOSR Journals
In this paper, we show theoretically that the reflectance spectra of one dimensional multilayer metal-organic periodic structure (1D MOPS) can be enhanced due to the addition of the organic constituents. We have used simple transfer matrix method to calculate the absorption, transmittance and reflectance of the 1D MOPS systems. The organic component like N,N’-bis-(1-naphthyl)-N,N’diphenyl-1; 1biphenyl-4; 4diamine (NPB) absorbs the light in ultra-violet, visible and infrared electromagnetic region and the structure with Ag-metal also having the tendency to absorb the light by the plasmaonic action and their refractive can be calculated from Drude equation. The reflectance spectra of multilayer 1D MOPS containing a variable number periodic of Ag/N,N’-bis-(1-naphthyl)-N,N’diphenyl-1; 1biphenyl-4; 4diamine (NPB) structure are calculated taking optical constant of NPB and Ag. The optical band gap and reflectance spectra of 1D MOPS of the considered structure is obtained in the visible and near infrared regions either with the variation of the metal layer thickness or thickness of the organic layer. From the results under investigation through TMM, tunability in the optical band gap was observed either change in thickness of the other layer 1/ or 2 or the angle of the incident. Due to optical absorption of the light in the different region of electromagnetic spectrum due to either N,N’-bis-(1-naphthyl)-N,N’diphenyl-1; 1biphenyl-4; 4diamine (NPB) or silver metal, the optical band gap of 1DMOPS shows the shift of band edges of λL and λR from ultra-violet to visible and the infrared with change the optical constant.
Plenary lecture given by Prof. Kenneth Gonsalves (ITT Mandi, India) on September 12, 2017 in Gramado (Brazil) during the XVI B-MRS Meeting. Acknowledgment: ITT Mandi.
36 Measurement of Σ beam asymmetry in π0 photoproduction off the neutron in t...Cristian Randieri PhD
Measurement of Σ beam asymmetry in π0 photoproduction off the neutron in the second and third resonances region - The European Physical Journal A, Hadrons and Nuclei, November 2009, Vol. 42, N. 2, pp. 151-157, ISSN: 1434-6001, doi: 10.1140/epja/i2009-10870-x
di R. Di Salvo, A. Fantini, G. Mandaglio, F. Mammoliti, O. Bartalini, V. Bellini, J. P. Bocquet, L. Casano, A. D’angelo, J. P. Didelez, D. Franco, G. Gervino, F. Ghio, G. Giardina, B. Girolami, A. Giusa, M. Guidal, E. Hourany, R. Kunne, A. Lapik, P. Levi Sandri, A. Lleres, M. Manganaro, D. Moricciani, A. N. Mushkarenkov, V. Nedorezov, C. Randieri, D. Rebreyend, N. Rudnev, G. Russo, C. Schaerf, M. L. Sperduto, M. C. Sutera, A. Turinge, V. Vegna, A. Fix, S. S. Kamalov, L. Tiator (2009)
Abstract
The Σ beam asymmetry in the photoproduction of neutral pions from quasi-free nucleons in a deuteron target was measured for the first time between 0.60 and 1.50GeV, with the GRAAL polarized and tagged photon beam. The asymmetry values from the quasi-free proton were found equal to the ones extracted from a pure proton target. The asymmetries from quasi-free proton and quasi-free neutron were found equal up to 0.82GeV and substantially different at higher energies. The results are compared with recent partial-wave analyses.
Deconvolution of mineral absorption bands an improved approachBiswajit Manna
Although visible and near-infrared reflectance spectra contain absorption bands that are
characteristico f the compositiona nd structureo f the absorbings pecies,d econvolvinga complex
spectrumis nontrivial. An improveda pproachto spectrald econvolutionis presentedh ere that
accuratelyre presentasb sorptiobna ndsa s discretem athematicadli stributionasn d resolvesc omposite
absorptionf eaturesi nto individuala bsorptionbsa nds. The frequentlyu sed Gaussianm odel of
absorptiobnan diss firste valuateadn ds howtno be inapproprifaotre t heF e2 +e lectronitcr ansition
absorptionisn pyroxenes pectra. Subsequentlay ,m odifiedG aussianm odeli s derivedu singa power
law relationshiopf energyt o averageb ondl ength. This modifiedG aussianm odel successfulldye picts
the characteristi0c. 9-}xrna bsorptionfe aturei n orthopyroxensep ectrau singa singled istribution.T he
modified Gaussianm odel is also shownt o provide an objectivea nd consistent ool for deconvolving
individual absorptionb andsi n the more complexo rthopyroxenec, linopyroxenep, yroxenem ixtures,
ando livines pectraT. hea bilityo f thisn ewm odifieGd aussiamno detlo describthe eF e2 + electronic
transition absorptionb ands in both pyroxenea nd olivine spectras tronglys uggeststh at it be the
method of choice for analyzing all electronic transition bands
Study of highly broadening Photonic band gaps extension in one-dimensional Me...IOSR Journals
In this paper, we show theoretically that the reflectance spectra of one dimensional multilayer metal-organic periodic structure (1D MOPS) can be enhanced due to the addition of the organic constituents. We have used simple transfer matrix method to calculate the absorption, transmittance and reflectance of the 1D MOPS systems. The organic component like N,N’-bis-(1-naphthyl)-N,N’diphenyl-1; 1biphenyl-4; 4diamine (NPB) absorbs the light in ultra-violet, visible and infrared electromagnetic region and the structure with Ag-metal also having the tendency to absorb the light by the plasmaonic action and their refractive can be calculated from Drude equation. The reflectance spectra of multilayer 1D MOPS containing a variable number periodic of Ag/N,N’-bis-(1-naphthyl)-N,N’diphenyl-1; 1biphenyl-4; 4diamine (NPB) structure are calculated taking optical constant of NPB and Ag. The optical band gap and reflectance spectra of 1D MOPS of the considered structure is obtained in the visible and near infrared regions either with the variation of the metal layer thickness or thickness of the organic layer. From the results under investigation through TMM, tunability in the optical band gap was observed either change in thickness of the other layer 1/ or 2 or the angle of the incident. Due to optical absorption of the light in the different region of electromagnetic spectrum due to either N,N’-bis-(1-naphthyl)-N,N’diphenyl-1; 1biphenyl-4; 4diamine (NPB) or silver metal, the optical band gap of 1DMOPS shows the shift of band edges of λL and λR from ultra-violet to visible and the infrared with change the optical constant.
Plenary lecture given by Prof. Kenneth Gonsalves (ITT Mandi, India) on September 12, 2017 in Gramado (Brazil) during the XVI B-MRS Meeting. Acknowledgment: ITT Mandi.
36 Measurement of Σ beam asymmetry in π0 photoproduction off the neutron in t...Cristian Randieri PhD
Measurement of Σ beam asymmetry in π0 photoproduction off the neutron in the second and third resonances region - The European Physical Journal A, Hadrons and Nuclei, November 2009, Vol. 42, N. 2, pp. 151-157, ISSN: 1434-6001, doi: 10.1140/epja/i2009-10870-x
di R. Di Salvo, A. Fantini, G. Mandaglio, F. Mammoliti, O. Bartalini, V. Bellini, J. P. Bocquet, L. Casano, A. D’angelo, J. P. Didelez, D. Franco, G. Gervino, F. Ghio, G. Giardina, B. Girolami, A. Giusa, M. Guidal, E. Hourany, R. Kunne, A. Lapik, P. Levi Sandri, A. Lleres, M. Manganaro, D. Moricciani, A. N. Mushkarenkov, V. Nedorezov, C. Randieri, D. Rebreyend, N. Rudnev, G. Russo, C. Schaerf, M. L. Sperduto, M. C. Sutera, A. Turinge, V. Vegna, A. Fix, S. S. Kamalov, L. Tiator (2009)
Abstract
The Σ beam asymmetry in the photoproduction of neutral pions from quasi-free nucleons in a deuteron target was measured for the first time between 0.60 and 1.50GeV, with the GRAAL polarized and tagged photon beam. The asymmetry values from the quasi-free proton were found equal to the ones extracted from a pure proton target. The asymmetries from quasi-free proton and quasi-free neutron were found equal up to 0.82GeV and substantially different at higher energies. The results are compared with recent partial-wave analyses.
Deconvolution of mineral absorption bands an improved approachBiswajit Manna
Although visible and near-infrared reflectance spectra contain absorption bands that are
characteristico f the compositiona nd structureo f the absorbings pecies,d econvolvinga complex
spectrumis nontrivial. An improveda pproachto spectrald econvolutionis presentedh ere that
accuratelyre presentasb sorptiobna ndsa s discretem athematicadli stributionasn d resolvesc omposite
absorptionf eaturesi nto individuala bsorptionbsa nds. The frequentlyu sed Gaussianm odel of
absorptiobnan diss firste valuateadn ds howtno be inapproprifaotre t heF e2 +e lectronitcr ansition
absorptionisn pyroxenes pectra. Subsequentlay ,m odifiedG aussianm odeli s derivedu singa power
law relationshiopf energyt o averageb ondl ength. This modifiedG aussianm odel successfulldye picts
the characteristi0c. 9-}xrna bsorptionfe aturei n orthopyroxensep ectrau singa singled istribution.T he
modified Gaussianm odel is also shownt o provide an objectivea nd consistent ool for deconvolving
individual absorptionb andsi n the more complexo rthopyroxenec, linopyroxenep, yroxenem ixtures,
ando livines pectraT. hea bilityo f thisn ewm odifieGd aussiamno detlo describthe eF e2 + electronic
transition absorptionb ands in both pyroxenea nd olivine spectras tronglys uggeststh at it be the
method of choice for analyzing all electronic transition bands
C3N5: A Low Bandgap Semiconductor Containing an Azo-linked Carbon Nitride Fra...Pawan Kumar
Modification of carbon nitride based polymeric 2D materials for tailoring their optical, electronic and chemical properties for various applications has gained significant interest. The present report demonstrates the synthesis of a novel modified carbon nitride framework with a remarkable 3:5 C:N stoichiometry (C3N5) and an electronic bandgap of 1.76 eV, by thermal deammoniation of the melem hydrazine precursor. Characterization revealed that in the C3N5 polymer, two s-heptazine units are bridged together with azo linkage, which constitutes an entirely new and different bonding fashion from g-C3N4 where three heptazine units are linked together with tertiary nitrogen. Extended conjugation due to overlap of azo nitrogens and increased electron density on heptazine nucleus due to the aromatic π network of heptazine units lead to an upward shift of the valence band maximum resulting in bandgap reduction down to 1.76 eV. XRD, He-ion imaging, HR-TEM, EELS, PL, fluorescence lifetime imaging, Raman, FTIR, TGA, KPFM, XPS, NMR and EPR clearly show that the properties of C3N5 are distinct from pristine carbon nitride (g-C3N4). When used as an electron transport layer (ETL) in MAPbBr3 based halide perovskite solar cells, C3N5 outperformed g-C3N4, in particular generating an open circuit photovoltage as high as 1.3 V, while C3N5 blended with MAxFA1–xPb(I0.85Br0.15)3 perovskite active layer achieved a photoconversion efficiency (PCE) up to 16.7%. C3N5 was also shown to be an effective visible light sensitizer for TiO2 photoanodes in photoelectrochemical water splitting. Because of its electron-rich character, the C3N5 material displayed instantaneous adsorption of methylene blue from aqueous solution reaching complete equilibrium within 10 min, which is significantly faster than pristine g-C3N4 and other carbon based materials. C3N5 coupled with plasmonic silver nanocubes promotes plasmon-exciton coinduced surface catalytic reactions reaching completion at much low laser intensity (1.0 mW) than g-C3N4, which showed sluggish performance even at high laser power (10.0 mW). The relatively narrow bandgap and 2D structure of C3N5 make it an interesting air-stable and temperature-resistant semiconductor for optoelectronic applications while its electron-rich character and intra sheet cavity make it an attractive supramolecular adsorbent for environmental applications.
Consistently High Voc Values in p-i-n Type Perovskite Solar Cells Using Ni3+-...Pawan Kumar
Leading edge p-i-n type halide perovskite solar cells (PSCs) severely underperform n-i-p PSCs. p-i-n type PSCs that use PEDOT:PSS hole transport layers (HTLs) struggle to generate open-circuit photovoltage values higher than 1 V. NiO HTLs have shown greater promise in achieving high Voc values albeit inconsistently. In this report, a NiO nanomesh with Ni3+ defect grown by the hydrothermal method was used to obtain PSCs with Voc values that consistently exceeded 1.10 V (champion Voc = 1.14 V). A champion device photoconversion efficiency of 17.75% was observed. Density functional theory modeling was used to understand the interfacial properties of the NiO/perovskite interface. The PCE of PSCs constructed using the Ni3+-doped NiO nanomesh HTL was ∼34% higher than that of conventional compact NiO-based perovskite solar cells. A suite of characterization techniques such as transmission electron microscopy, field emission scanning electron microscopy, intensity-modulated photocurrent spectroscopy, intensity-modulated photovoltage spectroscopy, time-resolved photoluminescence, steady-state photoluminescence, and Kelvin probe force microscopy provided evidence of better film quality, enhanced charge transfer, and suppressed charge recombination in PSCs based on hydrothermally grown NiO nanostructures.
Facile Synthesis and Characterization of Pyrolusite, β-MnO2, Nano Crystal wit...Editor IJCATR
MnO2 nanoparticles have been synthesized by a simple combustion method using MnSO4.4H2O. The crystalline phase, morphology, optical property and magnetic property of the as prepared nanoparticle were characterized using XRD, FT-IR, FT-Raman, SEM, UV-Vis, PL and VSM respectively. Structural studies by XRD indicate that the synthesized material as tetragonal rutile crystal structure. FT-IR and FT-Raman analysis revealed the stretching vibrations of metal ions in tetrahedral co-ordination confirming the crystal structure. The PL and UV analysis having an emission band at 390 nm, showed a prominent blue peak at 453 nm as well as a green emission lines at 553 nm with band gap energy of 3.2eV. Magnetic measurements indicate that the Néel temperature of the β-MnO2 structures is 92.5K for Hc = 100 Oe which showed antiferromagnetic behaviour.
Facile Synthesis and Characterization of Pyrolusite, β- MnO2, Nano Crystal wi...Editor IJCATR
MnO2 nanoparticles have been synthesized by a simple combustion method using MnSO4.4H2O. The crystalline phase,
morphology, optical property and magnetic property of the as prepared nanoparticle were characterized using XRD, FT-IR, FTRaman,
SEM, UV-Vis, PL and VSM respectively. Structural studies by XRD indicate that the synthesized material as tetragonal rutile
crystal structure. FT-IR and FT-Raman analysis revealed the stretching vibrations of metal ions in tetrahedral co-ordination confirming
the crystal structure. The PL and UV analysis having an emission band at 390 nm, showed a prominent blue peak at 453 nm as well as
a green emission lines at 553 nm with band gap energy of 3.2eV. Magnetic measurements indicate that the Néel temperature of the β-
MnO2 structures is 92.5K for Hc = 100 Oe which showed antiferromagnetic behaviour
Carbohydrate Research 405 (2015) 55–65Contents lists availab.docxwendolynhalbert
Carbohydrate Research 405 (2015) 55–65
Contents lists available at ScienceDirect
Carbohydrate Research
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c a r r e s
Electrochemical synthesis of nanostructured gold film for the study
of carbohydrate–lectin interactions using localized surface plasmon
resonance spectroscopy
http://dx.doi.org/10.1016/j.carres.2014.08.019
0008-6215/� 2014 Elsevier Ltd. All rights reserved.
⇑ Corresponding author. Tel.: +1 (314) 516 5346; fax: +1 (314) 516 5342.
E-mail address: [email protected] (K.J. Stine).
Jay K. Bhattarai a,b, Abeera Sharma a,b, Kohki Fujikawa a, Alexei V. Demchenko a, Keith J. Stine a,b,⇑
a Department of Chemistry and Biochemistry, University of Missouri—St. Louis, One University Boulevard, St. Louis, MO 63121, United States
b Center for Nanoscience, University of Missouri—St. Louis, One University Boulevard, St. Louis, MO 63121, United States
a r t i c l e i n f o a b s t r a c t
Article history:
Received 30 April 2014
Received in revised form 15 July 2014
Accepted 30 August 2014
Available online 16 September 2014
Keywords:
Lectin
Mannose
Monolayer
Plasmon
Gold
Localized surface plasmon resonance (LSPR) spectroscopy is a label-free chemical and biological molec-
ular sensing technique whose sensitivity depends upon development of nanostructured transducers.
Herein, we report an electrodeposition method for fabricating nanostructured gold films (NGFs) that
can be used as transducers in LSPR spectroscopy. The NGF was prepared by electrodepositing gold from
potassium dicyanoaurate solution onto a flat gold surface using two sequential controlled potential steps.
Imaging by scanning electron microscopy reveals a morphology consisting of randomly configured block-
like nanostructures. The bulk refractive index sensitivity of the prepared NGF is 100 ± 2 nm RIU�1 and the
initial peak in the reflectance spectrum is at 518 ± 1 nm under N2(g). The figure of merit is 1.7. In addition,
we have studied the interaction between carbohydrate (mannose) and lectin (Concanavalin A) on the
NGF surface using LSPR spectroscopy by measuring the interaction of 8-mercaptooctyl-a-D-mannopyran-
oside (aMan-C8-SH) with Concanavalin A by first immobilizing aMan-C8-SH in mixed SAMs with 3,6-
dioxa-8-mercaptooctanol (TEG-SH) on the NGF surface. The interaction of Con A with the mixed SAMs
is confirmed using electrochemical impedance spectroscopy. Finally, the NGF surface was regenerated
to its original sensitivity by removing the SAM and the bound biomolecules. The results from these exper-
iments contribute toward the development of inexpensive LSPR based sensors that could be useful for
studying glycan–protein interactions and other bioanalytical purposes.
� 2014 Elsevier Ltd. All rights reserved.
1. Introduction
Localized surface plasmon resonance (LSPR) spectroscopy based
on the development of noble metal nanostructures with tunable
and responsive plasmonic behavior has become of b ...
Synthesis and Characterisation of Copper Oxide nanoparticlesIOSR Journals
Cupric oxide (CuO) nanoparticles were prepared by the chemical route by calcinations at a higher temperature from 300oC to 400 oC. For the comparison transmission electron microscopy (TEM) and x-ray diffraction (XRD) measurements were made through JCPDS. There is good agreement between data produced by spectroscopy and the microscopic measurements.
Optical Control of Selectivity of High Rate CO2 Photoreduction Via Interband-...Pawan Kumar
Photonic crystals consisting of TiO2 nanotube arrays (PMTiNTs) with periodically modulated diameters were fabricated using a precise charge-controlled pulsed anodization technique. The PMTiNTs were decorated with gold nanoparticles (Au NPs) to form plasmonic photonic crystal photocatalysts (Au-PMTiNTs). A systematic study of CO2 photoreduction performance on as-prepared samples was conducted using different wavelengths and illumination sequences. A remarkable selectivity of the mechanism of CO2 photoreduction could be engineered by merely varying the spectral composition of the illumination sequence. Under AM1.5 G simulated sunlight (pathway#1), the Au-PMTiNTs produced methane (302 µmol h-1) from CO2 with high selectivity (89.3%). When also illuminated by a UV-poor white lamp (pathway#2), the Au-PMTiNTs produced formaldehyde (420 µmol h-1) and carbon monoxide (323 µmol h-1) with almost no methane evolved. We confirmed the photoreduction results by 13C isotope labeling experiments using GC-MS. These results point to optical control of the selectivity of high-rate CO2 photoreduction through selection of one of two different mechanistic pathways. Pathway#1 implicates electron-hole pairs generated through interband transitions in TiO2 and Au as the primary active species responsible for reducing CO2 to methane. Pathway#2 involves excitation of both TiO2 and surface plasmons in Au. Hot electrons produced by plasmon damping and photogenerated holes in TiO2 proceed to reduce CO2 to HCHO and CO through a plasmonic Z-scheme.
Noble Metal Free, Visible Light Driven Photocatalysis Using TiO2 Nanotube Arr...Pawan Kumar
Bulk g‐C3N4 is an earth‐abundant, easily synthesizable, and exceptionally stable photocatalyst with an electronic bandgap of 2.7 eV. Herein, the concepts of P‐doping and size quantization are combined to synthesize highly fluorescent P‐doped carbon nitride quantum dots (CNPQDs) with a bandgap of 2.1 eV. CNPQDs are hosted on anatase‐phase and rutile‐phase TiO2 nanotube array scaffolds, and examined as photoanodes for sunlight‐driven water‐splitting and as photocatalysts for surface catalytic reactions. Square‐shaped rutile phase TiO2 nanotube arrays (STNAs) decorated with CNPQDs (CNPQD‐STNA) generate 2.54 mA cm−2 photocurrent under AM1.5 G simulated sunlight. A champion hydrogen evolution rate of 22 µmol h−1 corresponds to a Faradaic efficiency of 93.2%. In conjunction with Ag nanoparticles (NPs), the CNPQD‐STNA hybrid is also found to be an excellent plexcitonic photocatalyst for the visible light‐driven transformation of 4‐nitrobenzenethiol (4‐NBT) to dimercaptoazobenzene (DMAB), producing reaction completion at a laser power of 1 mW (532 nm) while Ag NP/TNA and Ag NP/STNA photocatalysts cannot complete this transformation even at 10 mW laser power. The results point the way forward for photochemically robust, noble metal free, visible light harvesting photoacatalysts based on nanostructured heterojunctions of graphenic frameworks with TiO2.
Effect of Sn Doping on Structural and Electrical Properties of ZnO Thin Films...journal ijrtem
Abstract: Un-doped and tin (Sn) doped ZnO films were deposited on heated glass substrates by chemical spray pyrolysis method
(CSP). The effect of Sn concentration on the structural, surface morphological and electrical properties of the SnO2 films was
investigated. XRD analyses showed that the obtained films are polycrystalline in nature with hexagonal structure with preferred
orientation of (101). Doping with tin (Sn) causes increase in the grain size. Atomic force microscopy images showed that the root
mean square of the average surface roughness's varied from (1.48 to 3.58) as dopant concentration increased from 0 to 5 wt.%. The
electrical properties of the Sn ZnO films were strongly influenced by doping concentration. The electrical resistance of the films was
sharply decreased as dopant concentration increased.
Keywords: (ZnO) thin films, Sn Doping, Structural and electrical Properties
EFFECT OF ULTRAVIOLET RADIATION ON STRUCTURAL PROPERTIES OF NANOWIRESijoejournal
Copper nanowires were prepared through electrochemical template synthesis using Nucleopore polycarbonate membranes having nominal pore sizes of 800nm and 15nm diameter. The 800nm and 15nm nanowires thus grown were viewed under SEM and TEM respectively, while their FCC crystallographic structure was confirmed through X-ray and electron diffraction patterns. The X-ray diffraction peaks indicated strong texturing for (200). The texturing was found to reduce significantly upon exposure to ultraviolet radiation.
EFFECT OF ULTRAVIOLET RADIATION ON STRUCTURAL PROPERTIES OF NANOWIRES
ity-defense062309
1. Nano materials Optoelectronics Laboratory
IMS
Chirality dependent replacement of Flavin
Mononucleotide onto Carbon Nanotubes
using various Surfactants
Ity Sharma
June 23, 2009
Department of Chemistry,
University of Connecticut
4. Physico-Chemical
Large Surface Area (~1600 m2
/g)
Amenable to electrochemical doping
Thermal conductivity twice as good as
diamond (2000 W/m/K)
Good thermal stability (750°C in air,)
Electrical
Metallic or Semiconducting (1-D)
met-SWNTs are ballistic conductors
(109
A/cm2
)
Mechanical
Strongest known fiber (Young’s modulus, ~1
TPa)
Highly flexible, Buckle-prone
Large aspect ratio (~103
)
SWNTSWNT Unique PropertiesUnique Properties
Nanoelectronics, Nanosized Conductors
•Field emission displays
•Electromagnetic Shielding
•Atomic Force Microscope (AFM) tips
• Nanometric test tubes
•Advanced Composites
•Actuators
•Specialty Sensors
•Hydrogen storage
•Cancer therapy
5. Aggregation Dispersion
Separation
Diameter Chiraity
van der Waals binding energy of 500 eV per micrometer
of tube-tube contact
An individual fullerene nanotube in a cylindrical SDS
micelle
Handedness
Challenges
Length
Hersam, M. C., Nature Nanotechnology, 3, 387 (2008).
6. Cross sectional model of
A) Individual carbon nanotube in a cylinderical
SDS micelle
B) A seven –tube bundle coated by a layer of SDS
Emission spectrum (red) of individual fullerene
nanotubes suspended in SDS micelles in D2O, overlaid
with the absorption spectrum (blue) of the sample in
this region of first van Hove band gap transitions.
M. O’Connell et al., Science 297, 593 (2002).
Dispersion of SWNTs using SDS (Sodium dodecyl sulfate)
A
7. Fluorescence has been observed directly across the band gap of semiconducting carbon nanotubes
good spectroscopic route for finding the detailed composition of bulk nanotube samples
Schematic density of electronic states for a
single nanotube structure.
Contour plot of fluorescence intensity versus excitation
and emission wavelengths for a sample of SWNTs
suspended in SDS and deuterium oxide.
Photoluminescence : Important tool for nanotube
characterization
S.M. Bachilo et al Science 298 (2002) 2361.
M. O’Connell et al., Science 297, 593 (2002).
8. poly(9,9-dioctylfluorenyl-2,7-diyl),
(PFO)
Binding model of a (10,0) DNA wrapped
carbon nanotube*
Molecular mechanics simulations of the
polymer, PFO wrapping mechanism#
.
*Zheng, M. et al. DNA-assisted dispersion and separation
of carbon nanotubes. Nature Mater. 2, 338–342 (2003)
Selective enrichment of carbon nanotubes using non
covalent polymer wrapping
#
Nish, A., Hwang, J.-Y., Doig, J. & Nicholas, R. J., Highly
selective dispersion of single-walled carbon nanotubes
using aromatic polymers. Nature Nanotech. 2, 640–646
(2007)
polymeric nature of DNA and
PFO hinders post-separation
surfactant removal
9. The long d-ribityl
phosphate side groups
of FMN provide aqueous
solubilization.
1:4:4 (HiPCO:FMN:D2O)
SWNT dispersed with FMN and centrifuged at 15 kg for 2hrs.
Selection of carbon nanotubes with specific chiralities using helical
assemblies of flavin mononucleotide (FMN)*
Flavin
mononucleotide
(FMN)
Top view of isoalloxazine
moieties wrapped in an
8, 1 helical pattern.
This helical wrapping is stabilized by
cooperative hydrogen bonding
between adjacent flavin moieties
charge transfer interactions
between FMN and graphene side wall.
*
S.-Y. Ju, J. Doll, I. Sharma, F. Papadimitrakopoulos, Nature Nanotech. 3, 356
(2008).
H-bonded
ribbon
10. Photoluminescence Excitation Spectra (PLE) of HiPco-SWNTS
a PLE map of HiPco
SWNT dispersed with
SDBS centrifuged at
200kg
b SWNT dispersed
with FMN and
centrifuged at 15 kg
c After the addition
of 7.4mM of SDBS to
b
d Plot of ES
11 and ES
22
transitions for FMN
and SDBS dispersed
SWNTs.
11. The sigmoidal profiles were fit using Hill equation
Ka=Relative affinity of FMN-SWNT to SDBS
γ =Breadth of sigmoidal curve , indicating how fast SDBS
replaces FMN helix
2.81
1.51
1.33
a–d, PLE maps of FMN-dispersed nanotubes upon
addition of 0 (a), 2.3 (b), 4.3 (c) and 7.4mM (d) SDBS.
a–c, SBDS-derived PL intensity as a function
of SDBS concentration. Red curves are based
on Hill equation fitting
Elucidation of the selective affinity of the FMN helix on
different chirality nanotubes using SDBS
12. a, PLE map of the (8,6) nanotube in the salt-out
supernatant.
b, UV-vis-NIR spectra of the corresponding salt-
out supernatant (black solid line), compared with
the initial FMN-dispersed HiPco sample (red solid
line).
(i) selective SDBS replacement of FMN on all but (8,6)-SWNTs, and
(ii) addition of NaCl to salt out all SDBS-dispersed nanotubes
Enrichment of the (8,6) nanotube
13. Absorbance spectrum showing ES
11 semiconducting region of
FMN dispersed carbon nanotubes titrated with SC
concentrations 0 to 12mM
Sodium cholate, SC
Chirality dependent FMN replacement onto single
walled carbon nanoubes using Sodium Cholate*
#
Schematic depicting the arrangement of sodium cholate around
a (6,5) SWNT.
Purple, red, gray, blue, and white atoms represent Na, O, C (as
part of sodium cholate), C (as part of nanotube), and H.
*Ity Sharma, Sang-Yong Ju and Fotios Papadimitrakopoulos, MRS, 2008, Boston,
Session JJ15: Poster Session: Nanowires and Nanotubes: Electrical, Optical and Thermal properties
#Michael S. Arnold et al, ACS Nano, 2008, 2 (11), pp 2291–2300
14. a PLE map of HiPco SWNT dispersed with SC
centrifuged at 13 kg
b SWNT dispersed with FMN and centrifuged at 15 kg
c After the addition of 4.8mM of SC
d Plot of ES
11 and ES
22 transitions for FMN (red circle)
and SC (blue square) dispersed SWNTs.
Chirality dependent FMN replacement onto single walled
carbon nanoubes using Sodium Cholate
15. Chirality, family and modality dependence of FMN induced
E11
S
red shift for all PLE observed carbon nanotubes
16. 16
(n , m) Diamete
r nm
Chiral
angle
E11
S
E22
S
Ka
SC
γ SC
(8,3) 0.782 15.30 962 667 1.20 25.23
(7,6) 0.895 27.46 1128 650 1.31 28.07
(9,4) 0.916 17.48 1116 725 1.25 21.18
(8,6) 0.966 25.28 1183 720 2.83 10.42
(9,5) 0.976 20.63 1256 673 1.59 20.45
Table showing relative affinity (Ka) of FMN-SWNT wrapping
against SC concentration and fitted Hill equation
SC-PL inensity profiles for(8,6), (9,4) and (8,4)
as a function of SC concentration
PLE map of (8,6) SWNT showing FMN replacement by SC
titration
Elucidation of the selective affinity of the FMN helix on
different chirality nanotubes using SC
17. 17
Small diameter carbon nanotubes there is preference for near
zig zag carbon nanotubes binding with FMN
Large diameter nanotubes near arm chair are more favorable
Plot between binding constant Vs Diameter of SWNT
Interpolated lines follow distinct
color coded family (2n+m =
constant)and modality [(n-m)/3=1
or 2] patterns
18. 18
Conclusion
Flavin mononucleotide demonstrates the strongest binding constant with
(8,6) single walled carbon nanotube in terms of sodium cholate replacement as
in the case of SDBS replacement.
Red shift observed for the first and second optical transition energies
between SC-HiPco and FMN-dispersed single walled carbon nanotubes
resembles that of SDBS.
There is a gradual blue shift on addition of sodium cholate to FMN dispersed
carbon nanotubes as in the case of SDBS.
The tight conformation of sodium cholate provides higher Ka (binding
constant) and γ values. This gives the platform for better enrichment of (n,m)
carbon nanotubes in the sample.