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In recent years, carbon materials are widely investigated because of they are enormously sensitive to H 2 at room temperature conditions. In the present work, the inexpensive candle carbon soot (CCS) is used to detect 0.5% concentration of H 2 gas at room temperature. A simple flame of candle is used to synthesize the layers of carbon soot at room temperature conditions. It is observed that, the acid treatment of CCS drastically improved their structural and sensing properties as compared to as-synthesized CCS. The effect of acid functionalization on the CCS structure were investigated by X-ray diffraction (XRD) and Raman spectroscopy. To the best of our knowledge, detection of low concentrations of H 2 gas is reported here for the first time using economical CCS at room temperature. Synthesis of CCS film (a) a glass substrate is held in the flame of a candle (b) a thick CCS layer (c) SEM image of CCS layer. Image 1 • Fabrication of cost effective H 2 gas sensor at room temperature. • Well controlled functionalization of candle carbon soot at room temperature. • Role of functional groups on the structural property of candle carbon soot. • Importance of functionalization for carbon soot based H 2 gas sensor. [ABSTRACT FROM AUTHOR]

This work reports the fabrication of zirconia thin films by e-beam deposition, followed by thermal annealing in air at different temperatures to optimize the cubic phase without using any dopants or chemical stabiliser. The X-ray diffraction (XRD) and Raman spectra of zirconia films annealed at 500 °C reveal the formation of stable cubic phase with a crystallite size of 10.7 ± 0.8 nm at room temperature. Optical transparency of the zirconia film annealed at 500 °C is high, approaching 80% in the visible range. Increasing annealing temperature improves crystallinity, hydrophilicity and reduces nonradiative associated defects. The mechanical properties of zirconia films examined using static and dynamic nanoindentation demonstrate that hardness increases from 7.60 ± 0.26 GPa to 11.08 ± 0.90 GPa and elastic modulus increases from 170.74 ± 4.98 GPa to 210.13 ± 5.56 GPa when annealing temperature increases. The post-annealing temperature influences provide a method for tuning the optical, wetting and mechanical characteristics of zirconia thin film. [ABSTRACT FROM AUTHOR]

The deposition of reduced graphene oxide over layer on the SnS thin films had been shown to be an effective tool to improve its photoelectrochemical response. Pure phase SnS thin films were prepared using simple and inexpensive thermal evaporation method on ITO glass substrate followed by the deposition of reduced graphene oxide (rGO) layer by drop cast method. Samples were characterized using X-ray diffraction, Raman, scanning electron microscopy, UV–Visible absorption spectroscopy and their photoelectrochemical activity has been investigated. The results show the formation of pure phase SnS having orthorhombic crystal structure with optical band gap of 2.0 eV, rGO layer enhances the absorption in visible region. Maximum photocurrent density exhibited by SnS/0.1 wt% rGO was observed to be 1.1 mA/cm2 as compared to pristine SnS (0.3 mA/cm2) at 0.95V Ag/AgCl with enhanced photostability up to 1 h. Graphene oxide over layer acts as protecting layer for SnS in the electrolyte and plays a promising role in enhancing the charge carriers separation at the interface on account of being an electron reservoir to accept the photoexcited electrons. This work highlights the role of rGO and SnS interface on the photoelectrochemical water splitting. • Phase pure SnS thin films were prepared by using a simple and cost effective thermal evaporation method. • Variation of rGO concentration played a significant role in PEC response. • Improved charge separation & enhanced PEC response was achieved in SnS/rGO samples in acidic medium. • SnS/0.1 wt % rGO sample exhibited the best PEC response in acidic medium. [ABSTRACT FROM AUTHOR]

The photoelectrochemical performance of a BiVO 4 photoanode is limited by its poor charge transport properties, despite other useful optical absorption properties. Modifying the surface charge transport properties by forming heterojunction of BiVO 4 with other metal oxides layers having ultralow thickness is a promising route, as it may facilitate charge separation/transport without affecting other properties of BiVO 4. In this study, the structural, optical and PEC properties of heterojunction of BiVO 4 having ultrathin overlayers of Fe 2 O 3 , MoO 3 and ZnO has been investigated. The electrochemical impedance (via electrochemical impedance spectra in PEC cell) and surface photovoltage (using KPFM) measurements indicates improved charge transport owing to staggered band alignment and favourable band bending in case of BiVO 4 /MoO 3 heterojunction as compared to pristine BiVO 4 , BiVO 4 /Fe 2 O 3 and BiVO 4 /ZnO heterojunctions. Enhanced photocurrent density in BiVO 4 /MoO 3 of ~0.22 mA/cm2 at 1.23 V RHE which is 6 times as compared to pristine BiVO 4 layers has been observed. The results of the present study show that by forming heterojunction with a suitable semiconductor material can be used to enhance the PEC response by modifying the surface charge transfer characteristics and there is a large possibility of using other semiconductor materials for further investigations and improvement. Image 1 • Heterojunction of BiVO 4 with Fe 2 O 3 , MoO 3 and ZnO prepared via RF sputtering technique. • BiVO 4 /MoO 3 sample shows improved photovoltage and reduced charge transfer resistance. • Staggered band alignment in BiVO 4 /MoO 3 sample shows efficient carrier separation. • Maximum J light = 0.22 mA/cm2 is observed in BiVO 4 /MoO 3 heterostructure. [ABSTRACT FROM AUTHOR]

The electronic and optical properties of Cu 2 ZnGeS 4 are calculated by means of the full potential linearized augmented plane wave method (FP-LAPW) using the generalized gradient approximation (GGA) and the modified Becke–Johnson (mBJ) as exchange correlation functionals. The band structures, total and partial densities of states as well as optical properties are presented and discussed in the context of the available experimental data and theoretical calculations. Our calculations show that the conduction bands minima (CBM) is composed of contributions mainly from Ge–p states while the valence bands maxima (VBM) is dominated by Cu–d states. We find that Cu 2 ZnGeS 4 possesses a direct energy band gap situated at the center (Γ point) of the Brillouin Zone (BZ). The calculated energy gaps of 0.50 eV (GGA) and 1.21 eV (mBJ) are much smaller than the experimental value of around 2.2 eV. We have shown anisotropic behavior of the compound using optical constants and birefringence plots and found that the Δn(0) in GGA and mBJ is about 0.06 and 0.08, respectively when applied scissors correction. We find that applying the scissors correction leads to better agreement with the experiment. [ABSTRACT FROM AUTHOR]