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At least 1,801 records · Page 100
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Fabrication and characterization of n-type aluminum-boron co-doped ZnO on p-type silicon (n-AZB/p-Si) heterojunction diodes

Graphical abstract: - Highlights: • n-AZB/p-Si heterojunction diodes were formed. • n-AZB/p-Si diode annealed at 700 °C showed best rectifying behavior. • Zn{sub 2}SiO{sub 4} was formed at 800 °C. • n and ϕ{sub b} were estimated to be 1.63 and 0.4 eV, respectively, at 700 °C. • Tailoring of BG was attributed to annealing induced stresses in the films. - Abstract: In this paper, the growth of n-type aluminum boron co-doped ZnO (n-AZB) on a p-type silicon (p-Si) substrate by sol–gel method using spin coating technique is reported. The n-AZB/p-Si heterojunctions were annealed at different temperatures ranging from 400 to 800 °C. The crystallite size of the AZB nanostructures was found to vary from 28 to 38 nm with the variation in annealing temperature. The band gap of the AZB decreased from 3.29 to 3.27 eV, with increasing annealing temperature from 400 to 700 °C and increased to 3.30 eV at 800 °C probably due to the formation of Zn{sub 2}SiO{sub 4} at the interface. The band gap variation is explained in terms of annealing induced stress in the AZB. The n-AZB/p-Si heterojunction exhibited diode behavior. The best rectifying behavior was exhibited at 700 °C.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Solvent-controlled preparation and photocatalytic properties of nanostructured TiO{sub 2} thin films with different morphologies

Graphical abstract: Low-temperature growth of nanostructured TiO{sub 2} thin films was presented by a solvent-controlled method. Nanoparticle structured films in anatase phase have been successfully fabricated with some adjustment. The effects of the solvent were investigated and the formation mechanism was proposed. - Highlights: • Nanostructured TiO{sub 2} thin films with different morphologies were obtained at low temperature. • The effects of the solvent on the morphologies of the products were investigated. • The effects of the solvent on the phtocatalytic activity were investigated. - Abstract: A low-temperature growth method of nanostructured TiO{sub 2} thin films with different morphologies was reported. Rod-like, grass-like and nanosheet structured films have been successfully fabricated just by adjusting the ratio of different solvents. The effects of the solvent on the morphologies of the TiO{sub 2} nanostructures were investigated. The formation mechanism of different morphologies was proposed based on the experiment results. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). The photocatalytic activity of as-prepared samples for the degradation of methylene blue (MB) in water was evaluated under UV illumination. Results showed that the solvents exhibited important effect on the morphologies and photocatalytic activity of as-prepared nanostructured titania films.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Directly patternable SnO{sub 2} thin films incorporating Pt nanoparticles

Highlights: • Direct-patterning of SnO{sub 2} films incorporated with Pt nanoparticles. • Pt incorporated SnO{sub 2} thin films by using photochemical solution deposition. • Reduction catalytic behavior of Pt nanoparticles. • Progress reduction of SnO{sub 2} with increasing amount of Pt nanoparticles. • Enhanced electrical conductivity of SnO{sub 2} films with Pt nanoparticles incorporation. - Abstract: Direct-patterning of SnO{sub 2} films incorporating Pt nanoparticles was performed by using a photochemical solution deposition without a photoresist or dry etching. Incorporating Pt nanoparticles into these films had a slight effect on their crystallinity and almost no effect on their transmittance. The inclusion of Pt nanoparticles enhanced the electrical conductivity of the SnO{sub 2} thin films compared to their pristine forms. The chemical bonding state of the films was analyzed by X-ray photoelectron spectroscopy to investigate the effect of the Pt nanoparticles on the carrier concentration in the film. It was concluded that the reduction of SnO{sub 2} thin films by Pt nanoparticles progressed as a result of the presence of the Pt nanoparticles, causing an oxygen deficiency to develop in SnO{sub 2} and thereby influencing the carrier concentration of the film.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Photocatalytic activity of titania coatings synthesised by a combined laser/sol–gel technique

Highlights: • Sol–gel method was used to prepare titania coatings. • Titania thin films were coated on substrate surface by dip coating. • Fibre laser was employed to irradiate the titania coated surfaces. • Photocatalytic efficiency of titania coatings was significantly improved after laser processing. - Abstract: Titania coatings were prepared using sol–gel method and then applied on the substrate surface by dip coating. Fibre laser (λ = 1064 nm) in continuous wave mode was used to irradiate the titania coated surfaces at different specific energies. The ATR-FTIR, XRD, SEM, EDS and contact angle measurement were employed to analyse surface morphology, phase composition and crystalline structure of laser-irradiated titania coatings, whilst the photocatalytic activity was evaluated by measuring the decomposition of methylene blue (MB) after exposure to the visible light for various illumination times. Results showed that the laser-irradiated titania coatings demonstrate significant different composition and microstructure in comparison with the as-coated from the same sol–gel titania. Photocatalytic efficiency of titania coatings was significantly improved after laser processing. The photocatalytic activity of laser-irradiated titania coatings was higher than that of the as-coated titania. The titania coating processed at laser specific energy of 6.5 J/mm{sup 2} exhibited the highest photocatalytic activity among all titania samples.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Structural and vibrational investigations of Nb-doped TiO{sub 2} thin films

Highlights: • We studied the evolutions of structure for TiO{sub 2} thin film as changes with Nb doping and temperatures. • Up to 800 °C, the grain size of Nb{sub 0.1}Ti{sub 0.9}O{sub 2} is smaller than for pure TiO{sub 2} because doped Nb hinders the growth of the TiO{sub 2} grains. • There was no formation of the rutile phase at high temperature. • Nb doped TiO{sub 2} films have high electron densities at 400–700 °C. • Nb dope extends the absorbance spectra of TiO{sub 2} which leads to the band gap reduce. - Abstract: Acid-catalyzed sol–gel and spin-coating methods were used to prepare Nb-doped TiO{sub 2} thin film. In this work, we studied the effect of niobium doping on the structure, surface, and absorption properties of TiO{sub 2} by energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray reflectometry (XRR), X-ray photoelectron spectroscopy (XPS), Raman, and UV–vis absorption spectroscopy at various annealing temperatures. EDX spectra show that the Nb:Ti atomic ratios of the niobium-doped titania films are in good agreement with the nominal values (5 and 10%). XPS results suggest that charge compensation is achieved by the formation of Ti vacancies. Specific niobium phases are not observed, thus confirming that niobium is well incorporated into the titania crystal lattice. Thin films are amorphous at room temperature and the formation of anatase phase appeared at an annealing temperature close to 400 °C. The rutile phase was not observed even at 900 °C (XRD and Raman spectroscopy). Grain sizes and electron densities increased when the temperature was raised. Nb-doped films have higher electron densities and lower grain sizes due to niobium doping. Grain size inhibition can be explained by lattice stress induced by the incorporation of larger Nb{sup 5+} ions into the lattice. The band gap energy of indirect transition of the TiO{sub 2} thin films was calculated to be about 3.03 eV. After niobium doping, it decreased to 2.40 eV.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Ultrasonic spray pyrolysis growth of ZnO and ZnO:Al nanostructured films: Application to photocatalysis

Highlights: • Al–ZnO thin films and nanostructures were obtained by ultrasonic spray pyrolysis. • The texture and morphology of the samples depend on the deposition parameters. • The photocatalytic degradation of stearic acid was studied upon UV-A irradiation. - Abstract: Pure and Al-doped ZnO (Al = 1, 3, 5%) nanostructured thin films were grown at 400 °C on glass substrates by ultrasonic spray pyrolysis, a simple, environmental-friendly and inexpensive method, using aqueous solutions as precursors. The structural and morphological characteristics of the samples depend drastically on deposition parameters; ZnO nanostructured films, nanopetals and nanorods were systematically obtained by simply varying the precursor solution and/or the spraying time. Transmittance measurements have shown that all samples are transparent in the visible wavelength region. Finally, the photocatalytic properties of the samples were investigated against the degradation of stearic acid under UV-A light illumination (365 nm); both pure and Al-doped ZnO nanostructured thin films show good photocatalytic activity regarding the degradation of stearic acid, due to their good crystallinity and large surface area.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Thin films of copper antimony sulfide: A photovoltaic absorber material

Highlights: • CuSbS{sub 2} thin films were prepared by heating Sb{sub 2}S{sub 3}/Cu layers. • Analyzed the structure, composition, optical, and electrical properties. • PV structures: glass/SnO{sub 2}:F/n-CdS/p-CuSbS{sub 2}/C/Ag were formed at different conditions. • The PV parameters (J{sub sc}, V{sub oc}, and FF) were evaluated from the J–V characteristics. • J{sub sc}: 0.52–3.20 mA/cm{sup 2}, V{sub oc}:187–323 mV, FF: 0.27–0.48 were obtained. - Abstract: In this work, we report preparation and characterization of CuSbS{sub 2} thin films by heating glass/Sb{sub 2}S{sub 3}/Cu layers and their use as absorber material in photovoltaic structures: glass/SnO{sub 2}:F/n-CdS/p-CuSbS{sub 2}/C/Ag. The Sb{sub 2}S{sub 3} thin films of 600 nm were prepared by chemical bath deposition on which copper thin films of 50 nm were thermally evaporated, and the glass/Sb{sub 2}S{sub 3}/Cu multilayers were heated in vacuum at different temperatures. X-ray diffraction analysis showed the formation of orthorhombic CuSbS{sub 2} after heating the precursor layers. Studies on identification and chemical state of the elements were done using X-ray photoelectron spectroscopy. The optical band gap of the CuSbS{sub 2} thin films was 1.55 eV and the thin films were photoconductive. The photovoltaic parameters of the devices using CuSbS{sub 2} as absorber and CdS as window layer were evaluated from the J–V curves, yielding J{sub sc}, V{sub oc}, and FF values in the range of 0.52–3.20 mA/cm{sup 2}, 187–323 mV, and 0.27–0.48, respectively, under illumination of AM1.5 radiation.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Nano-crystalline thin and nano-particulate thick TiO{sub 2} layer: Cost effective sequential deposition and study on dye sensitized solar cell characteristics

Highlights: • Thin TiO{sub 2} layer is deposited on conducting substrate using sol–gel based dip coating. • TiO{sub 2} nano-particles are synthesized using hydrothermal route. • Thick TiO{sub 2} particulate layer is deposited on prepared thin layer. • Dye sensitized solar cells are made using thin and thick layer based photo-anode. • Introduction of thin layer in particulate photo-anode improves the cell efficiency. - Abstract: A compact thin TiO{sub 2} passivation layer is introduced between the mesoporous TiO{sub 2} nano-particulate layer and the conducting glass substrate to prepare photo-anode for dye-sensitized solar cell (DSSC). In order to understand the effect of passivation layer, other two DSSCs are also developed separately using TiO{sub 2} nano-particulate and compact thin film based photo-anodes. Nano-particles are prepared using hydrothermal synthesis route and the compact passivation layer is prepared by simply dip coating the precursor sol prepared through wet chemical route. The TiO{sub 2} compact layer and the nano-particles are characterised in terms of their micro-structural features and phase formation behavior. It is found that introduction of a compact TiO{sub 2} layer in between the mesoporous TiO{sub 2} nano-particulate layer and the conducting substrate improves the solar to electric conversion efficiency of the fabricated cell. The dense thin passivation layer is supposed to enhance the photo-excited electron transfer and prevent the recombination of photo-excited electrons.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

A facile strategy to fabricate plasmonic Cu modified TiO{sub 2} nano-flower films for photocatalytic reduction of CO{sub 2} to methanol

Graphical abstract: Photoreduction of CO{sub 2} to CH{sub 3}OH over plasmonic Cu/TiO{sub 2} film. - Highlights: • Cu nanoparticles modified TiO{sub 2} nano-flower film was prepared by a facile strategy. • Cu nanoparticles can enhance the light absorption and the Raman scattering of TiO{sub 2}. • Cu nanoparticles can effectively restrain the recombination of the charge carriers. • A synergistic mechanism is proposed for photocatalytic reduction of CO{sub 2} on Cu/TiO{sub 2} film. - Abstract: Cu nanoparticles (NPs) deposited TiO{sub 2} nano-flower films were fabricated using a combination of a hydrothermal method and a microwave-assisted reduction process. The investigations indicated that Cu NPs and TiO{sub 2} film both exhibit visible light harvesting properties based on localized surface plasmon resonance (LSPR) of Cu NPs and unique nanostructures of TiO{sub 2} film. Fluorescence quenching was observed because the recombination of charge carriers was effectively suppressed by Cu NPs deposition. The experimental results indicate that Cu/TiO{sub 2} films exhibit better activity for the photocatalytic reduction of CO{sub 2} due to the charge transfer property and LSPR effect of Cu NPs. The CH{sub 3}OH production rate reached 1.8 μmol cm{sup −2} h{sup −1} (energy efficiency was 0.8%) over 0.5 Cu/TiO{sub 2} film under UV and visible light irradiation, which was 6.0 times higher than that observed over pure TiO{sub 2} film. In addition, a tentative photocatalytic mechanism is proposed to understand the experimental results over the Cu modified TiO{sub 2} nano-flower films.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

SnO{sub 2} films: In-situ template-sacrificial growth and photovoltaic property based on SnO{sub 2}/poly(3-hexyl-thiophene) for hybrid solar cell

Highlights: • SnO{sub 2} nanocrystals/thin films were fabricated on ITO glass substrate from preformed SnS thin film as sacrificial template. • The SnO{sub 2} film and SnO{sub 2}/P3HT was characterized by several techniques. • The new hybrid solar cell device was based on the hybrid thin film of SnO{sub 2} NCs and P3HT composites. - Abstract: we described a facile in-situ wet chemical method to prepare SnO{sub 2} thin film on ITO glass substrate from preformed SnS thin film as sacrificial template. The chemical conversion process of SnS to SnO{sub 2} was studied. The SnO{sub 2} film and SnO{sub 2}/P3HT was characterized by several techniques, such as powder X-ray diffract meter (XRD), Raman spectrometer, scanning electron microscope (SEM), atomic force microscope (AFM) and UV–vis spectrophotometer in detail. The new SnO{sub 2}/P3HT hybrid solar cell device showed an open-circuit voltage of 0.185 V, a short-circuit current density of 0.366 mA/cm{sup 2} and a fill factor of 0.247, corresponding to a power conversion efficiency of 0.0167%.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Characterization of ZnO thin films grown on different p-Si substrate elaborated by solgel spin-coating method

Highlights: • High quality ZnO thin films grown on different p-Si substrates were successful obtained by sol–gel process. • PL measurement revealed that ZnO thin film grown on porous Si has the better optical quality. • I–V characteristics for all heterojunctions exhibit successful diode formation. • The diode ZnO/PSi shows a better photovoltaic effect under illumination with a maximum {sub Voc} of 0.2 V. - Abstract: In this study, ZnO thin films are deposited by sol–gel technique on p-type crystalline silicon (Si) with [100] orientation, etched silicon and porous silicon. The structural analyses showed that the obtained thin films were polycrystalline with a hexagonal wurtzite structure and preferentially oriented along the c-axis direction. Morphological study revealed the presence of rounded and facetted grains irregularly distributed on the surface of all samples. PL spectra at room temperature revealed that ZnO thin film grown on porous Si has a strong UV emission with low defects in the visible region comparing with ZnO grown on plat Si and etched Si surface. The heterojunction parameters were evaluated from the (I–V) under dark and illumination at room temperature. The ideality factor, barrier height and series resistance of heterojunction grown on different p-Si substrates are determined by using different methods. Best electrical properties are obtained for ZnO layer deposited on porous silicon.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Structural and electrical properties of Nb doped TiO{sub 2} films prepared by the sol–gel layer-by-layer technique

Highlights: • TiO{sub 2}:Nb (1.2 at.%) multilayer films were deposited by sol–gel method on glass and Si. • 5 and 10 layers TiO{sub 2}:Nb films crystallize only in the anatase phase. • E{sub g} values are within 3.24–3.32 eV showing a decrease with increasing the layer number. • The specific resistivity, effective donor and sheet energy densities were obtained. • Nb donor compensation by acceptor levels in TiO{sub 2}:Nb film was suggested. - Abstract: Thin films of 5 and 10-layered sol–gel TiO{sub 2} were doped with 1.2 at.% Nb and their structural, optical and electrical properties were investigated. The films crystallized only in anatase phase, as evidenced by X-ray diffraction and selected area electron diffraction analyses. High resolution transmission electron microscopy revealed nanosized crystallites with amorphous boundaries. Current-voltage measurements on metal-TiO{sub 2}–Si structures showed the formation of n{sup +}–n heterojunction at the TiO{sub 2}–Si interface with a rectification ratio of 10{sup 4}. The effective donor density varies between 10{sup 16} and 10{sup 17} cm{sup −3}, depending on film thickness. The sheet energy densities under forward and reverse bias are in the order of 10{sup 12} and 10{sup 10} cm{sup −2} eV{sup −1}, respectively. These values and the high specific resistivity (10{sup 4} Ω cm) support the existence of compensating acceptor levels in these films. It was established that the conduction mechanism is based on space charge limited current via deep levels with different energy positions in the band gap.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Ni nanoparticles embedded into cross-linked NiO nanoflakes as enhanced cathode for alkaline batteries

Highlights: • Ni/NiO arrays prepared by hydrothermal synthesis and electrodeposition methods. • Ni/NiO nanoflake arrays show high capacity for alkaline batteries. • Introducing Ni to the NiO nanoflake is favorable for fast electron transfer. - Abstract: Construction of metal/metal oxide composite arrays is highly important for developing advanced electrochemical energy devices. In this work, we report a facile electrodeposition method to embed Ni network into hydrothermal NiO nanoflake arrays. Ni nanoparticles of 10–25 nm are intimately integrated with NiO nanoflakes of 20–30 nm forming cross-linked Ni/NiO composite arrays. The electrochemical potentials of Ni/NiO composite arrays are explored as cathode of alkaline batteries by means of galvanostatic charge/discharge tests and cyclic voltammograms (CV) in KOH solution. Compared with the unmodified NiO nanoflake arrays, the Ni/NiO composite arrays show much better electrochemical properties with higher capacity (100 mAh g{sup −1} vs. 75 mAh g{sup −1} at 2 A g{sup −1}), enhanced cycling life (capacity retention: 96% vs. 82%) after 3800 cycles and improved high-rate capability. The introduction of Ni nanoparticles not only improves the electrical conductivity, but also acts as anchors to fasten the active nanoflakes to achieve long-term cycles.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Structural, optical and femtosecond third-order nonlinear optical properties of LiNbO{sub 3} thin films

Highlights: • Fs third order NLO properties of LiNbO{sub 3} thin films were investigated. • Al:ZnO was used as a buffer layer to control the growth of LiNbO{sub 3}. • The magnitude of the χ{sup (3)} of all films was ∼10{sup −11} e.s.u. • χ{sup (3)} obtained here is much higher that of single crystal Z-cut LiNbO{sub 3}. - Abstract: LiNbO{sub 3} thin films were deposited by means of Al:ZnO as intermediate layer using pulsed laser deposition and their structural, linear and nonlinear optical (NLO) properties were investigated. The films were found to be polycrystalline, (110) orientation for Al:ZnO/fused silica and (300) orientation for Al:ZnO/quartz substrates. The films demonstrated a transparency of >80% in the visible and near-infrared region. The NLO studies were performed with the Z-scan technique using ∼150 fs, 80 MHz pulses at 800 nm. The studies revealed that the polycrystalline LiNbO{sub 3}films and (300) LiNbO{sub 3}films demonstrated reverse saturable absorption while a transition to saturable absorption was observed in the case of (110) LiNbO{sub 3}. The presence of two-photon absorption is attributed to the indirect transition via intermediate defect levels which is related to the structural asymmetry. The large nonlinearity in refractive index could be a result of the strain induced ferroelectric polarization. The magnitude of the third order optical nonlinearity of all films was ∼10{sup −11} e.s.u. which is orders of magnitude higher than the value obtained for single crystal Z-cut LiNbO{sub 3}.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Synthesis of V2O5/C core/shell arrays on graphene foam for electrochemical energy storage

Highlights: • Construct graphene foam supported V{sub 2}O{sub 5}/C c arrays. • Graphene foam + {sub 2}O{sub 5}/C arrays show large capacity and good cycles. • C layer is favorable for fast ion/electron transfer. - Abstract: V{sub 2}O{sub 5}-based materials are regarded as promising cathode materials for lithium-ion batteries (LIBs) because of their larger theoretical capacities than commercial cathode materials. Herein we develop a united solvothermal-chemical vapor deposition method for construction of bind-free V{sub 2}O{sub 5}/C core/shell arrays on the graphene foams positive electrodes of LIBs. Active V{sub 2}O{sub 5} nanoflakes with thicknesses of 10–15 nm are wrapped by ultrathin carbon layer of 2–4 nm forming core/shell arrays on the GF skeleton. The unique core/shell architecture can provide short ion/electron diffusion paths and substantial protection shell for the active materials, thus leading to accelerated electrochemical kinetics and enhanced cycling stability. A noticeable initial capacity of 290 mAh g{sup −1} at 1C in the voltage range of 2.0–4.0 V and 217 mAh g{sup −1} at 6C after 1000 cycles could be obtained for the GF + V{sub 2}O{sub 5}/C electrode, much better than its GF + V{sub 2}O{sub 5} counterpart.

25 ENERGY STORAGE↗
DOE OSTI2018

Morphology of phase-separated VO2 films deposited on TiO2-(001) substrate

Highlights: • Phase separation in VO{sub 2} films at room temperature was studied by TEM. • Tetragonal phase with a zig-zag interface was observed in the neighborhood of the VO{sub 2}/TiO{sub 2} boundary. • The peculiar interface could be explained by the crystallographic relationship between the monoclinic and tetragonal phases. - Abstract: The basic morphology of phase-separated VO{sub 2} films, in which the tetragonal (metallic) phase coexists with the monoclinic (insulating) phase, was studied using transmission electron microscopy. While the phase transformation temperature in an unstrained crystal is approximately 340 K, it was observed that at 298 K, elastic strain (caused by lattice mismatch with the TiO{sub 2}-(001) substrate) stabilized the tetragonal phase near the VO{sub 2}/TiO{sub 2} boundary. The observed zig-zag-shaped interface of the tetragonal phase was explained by the crystallographic orientation relationship between the tetragonal and monoclinic phases. The observations provide valuable information for future applications of VO{sub 2} films.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Investigation on improved performance of Erbium doped TiO2 nanowire based UV detector

Highlights: • PL study showed the removal of oxygen defects of TiO{sub 2} material after Er doping. • Superior photosensitivity was obtained for Er:TiO{sub 2} NW based detector. • Detectivity and NEP were calculated for both undoped and doped detectors. • Photoswitching was observed for Er:TiO{sub 2} NW detector at 350 nm of wavelength. - Abstract: Undoped TiO{sub 2} and Erbium doped TiO{sub 2} nanowires (Er:TiO{sub 2} NWs) were synthesized on respective thin films using e-beam cum glancing angle deposition technique onto n-type silicon substrates. The length of the NWs was ∼182 nm as calculated from field emission gun scanning electron microscopy images. Transmission electron microscopy showed an average NW length of 173 nm. Polycrystalline nature of both samples was obtained from the selected area electron diffraction analysis as well as from the X-ray diffraction (XRD) analysis. Energy dispersive X-ray spectroscopy and variation in the grain size (calculated from XRD) confirmed the doping of Erbium in case of Er:TiO{sub 2} NWs. Increased absorption, as well as enhanced bandgap, was observed for Er:TiO{sub 2} NWs compared to the undoped TiO{sub 2} NWs. Superior device performance in terms of detectivity, sensitivity and photoswitching was obtained for Er:TiO{sub 2} NWs as compared to the undoped TiO{sub 2} NWs in the UV region.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Synthesis of titania wrapped cadmium sulfide nanorods for photocatalytic hydrogen generation

Highlights: • TiO{sub 2}@CdS nanorods with core/shell morphology prepared by simple hydrothermal method. • TiO{sub 2} shell thickness optimized for enhanced photocatalytic activity. • Initial concentration of sacrificial agent and solution pH were optimized for H{sub 2} generation. • Optimized photocatalyst C{sub 3}T{sub 3} displayed stable and continuous H{sub 2} evolution for 20 h. • Optimised catalyst showed 12-folds efficient H{sub 2} production under UV–vis vs visible light. - Abstract: Herein we report a simplified synthetic approach for a semiconductor photocatalyst (CdS) wrapped with a nanoscale thin-layer of semiconducting material (TiO{sub 2}) to overcome the instability issues, besides the improved catalytic efficiency. Images of HR-TEM and elemental mapping evidenced the presence of CdS that covered by ultra thin-layer of TiO{sub 2} as shell. The UV–vis diffuse reflectance spectra showed red-shift in absorption edge in visible region. The photocatalytic water splitting towards hydrogen production using Na{sub 2}S/Na{sub 2}SO{sub 4} as sacrificial agent was evaluated under UV–vis and visible light irradiation. The essential variables such as thickness of TiO{sub 2} shell, amount of sacrificial agent and solution pH were fine tuned to achieve hydrogen generation of 5791 mL h{sup −1} g{sup −1} of catalyst. The higher efficiency is ascribed to core/shell morphology of CdS/TiO{sub 2} system that channelled the excitons to the surface for the red-ox reactions rather than recombination. The catalytic stability result ascertained that the photo-corrosion is greatly suppressed.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

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