Search

• RF sputtering of high quality WSe 2 thin films. • Improved structural, optical, and electrical properties by selenization. • A shift in flat band potential from 0.78 V to 0.89 V. • Photoresponsivity of 1.2 μA/W and photo detectivity of 9.5 × 105 jones. • Improved photocurrent and photoelectrochemical performance. Tungsten diselenide (WSe 2) is one of the promising two-dimensional materials among transition metal dichalcogenide (TMDCs) for its application in solar hydrogen production and optoelectronics devices. In this paper, we report the synthesis of WSe 2 thin films using RF-magnetron sputtering followed by post-selenizationin in purview of their use for photoelectrochemical (PEC) water splitting and photodetection applications. Characterization of selenized WSe 2 film shows improved structural, optical, and electrical properties compared to as-deposited WSe 2 film. The PEC evaluation shows that the selenized WSe 2 photocathode has improved photocurrent density, stability, and charge transfer properties compared to the as-deposited film. Furthermore, the selenized WSe 2 thin film photodetector demonstrated excellent performance, including better responsivity of 1.2 μA/W and detectivity of 9.5 × 105 Jones with enhanced response time under one sun illumination. These results highlight a simple fabrication approach for producing scalable and high-quality WSe 2 thin films for next-generation optoelectronics devices. The post-selenization step can effectively heal defects and optimize optoelectronic properties. [Display omitted] [ABSTRACT FROM AUTHOR]

One step electrodeposition method has been used to realize highly porous ZnO pin hole (ZP) and ZnO rosette sheets (ZS) nanostructure based photo-anodes for efficient photoelectrochemical (PEC) splitting of water. Electrodeposited ZP and ZS based photo-anodes exhibit enhanced photocurrent density of 0.62 mA/cm2 and 0.76 mA/cm2 respectively (at a bias of 0.75 V). Further on hydrothermal amination (A), these electrodeposited ZP and ZS (A-ZP and A-ZS) nanostructure based photo-anodes had shown enhanced photocurrent density of 1.02 mA/cm2 and 1.27 mA/cm2, respectively. Surface morphology, evolution and elemental study were done using FESEM and EDX. Raman spectra of aminated photo-anodes have peaks at ∼270 cm−1 and ∼511 cm−1 related to stretching vibration mode between Zn N and Zn O. The peaks at wave number ∼558 cm−1 and ∼571 cm−1 is due to formation of Zn C bonds and because of complex defects respectively. ZnO exhibits low PEC activity, but on nano-structuring in the form of ZP and ZS improves its light absorption capacity. Hydrothermal amination red shifts (∼25 nm) the absorption band at ∼ 425 nm. The N and C act as electron reservoirs in A-ZP and A-ZS photo-anodes and efficiently separate the photo-generated electron/hole pairs and restrain charge recombination to generate photo-reactive sites. Electrochemical impedance spectroscopy (EIS) revealed that A-ZP and A-ZS had low charge transfer resistance compared to their bare counterparts. This lead to considerably improved PEC performance. An unprecedented increase in IPCE values in A-ZP and A-ZS can be assigned to the decrease in band gap and thereby significant enhancement in photocurrent density. These result in to proper charge segregation and improved charge transportation. The maximum value of IPCE is 9.6% for A-ZS sample and it is also clear that ZP and ZS nanostructured film have higher IPCE values at ∼400 nm than traditional ZnO thin film. A-ZP and A-ZS based photo-anodes have exhibited enhanced PEC performance as evident from IPCE measurements and thus can be a prospective candidate for PEC and optoelectronic applications. • Influence of amination on zinc oxide nanostructures is discussed in detail. • N and C act as electron reservoirs in A-ZP and A-ZS based photoanodes. • A-ZP and A-ZS exhibited photocurrent density of 1.02 mAcm−2 and 1.27 mAcm2. • Aminated zinc oxide nanosheets exhibited an IPCE ∼9.6%. [ABSTRACT FROM AUTHOR]

In photoelectrochemical (PEC) water splitting, visible light active semiconductors exhibit high conversion efficiency as they are more responsive. Herein, we have realized novel Bi 2 S 3 –In(OH) x S y nanoarchitectures for efficient PEC water splitting. We have electrodeposited bismuth vanadate (BiVO 4) thin films, and In and S were incorporated via hydrothermal treatment, leading to the formation of novel Bi 2 S 3 –In(OH) x S y nanoarchitectures. Bi 2 S 3 –In(OH) x S y plane view field emission scanning electron microscope shows a novel patty-packed structure covered with some urchin-like structures, implying a strong surface effect. Electron Impedance spectroscopy (EIS) was employed for impedance measurements. Flat band potential and carrier concentration were determined from Mott-Schottky (MS) plots. The realized novel Bi 2 S 3 –In(OH) x S y nanoarchitecture-based photoanodes exhibited a remarkable photocurrent density of 7.77 mA/cm2 at a bias voltage of 1.2 V/RHE under 1.5 AM illumination (1000 W/m2). The heterojunction nanoarchitectures have a reduction in the surface states of the nanocrystal, low lattice misfit, and quick charge transfer, which leads to effective PEC activity. The ABPE for the novel Bi 2 S 3 –In(OH) x S y nanoarchitecture-based photoanodes is 4.5% at 0.6 V vs. RHE in an electrolyte solution containing 0.1 M Na 2 SO 4. The results are encouraging and suggest that the Bi 2 S 3 –In(OH) x S y nanoarchitectures-based photoanodes can be a prospective material for efficient solar-to-hydrogen generation devices. [Display omitted] • Photoelectrochemical water splitting by Bi 2 S 3 –In(OH) x S y nanoarchitectures. • New class of visible light-responsive metal hydroxide. • Remarkable photocurrent density. • Recued surface states, low lattice misfit, and quick charge transfer. • Prospective material for efficient solar-to-hydrogen generation devices. [ABSTRACT FROM AUTHOR]

Summary: Border cells in the Drosophila ovary originate within an epithelium, detach from it, invade neighboring nurse cells, and migrate as a coherent cluster. This migration has served as a useful genetic model for understanding epithelial cell motility. The prevailing model of growth factor-mediated chemotaxis in general, and of border cells in particular, posits that receptor activation promotes cellular protrusion at the leading edge. Here we report the time-lapse video imaging of border cell migration, allowing us to test this model. Reducing the activities of the guidance receptors EGFR and PVR did not result in the expected inhibition of protrusion, but instead resulted in protrusion in all directions. In contrast, reduction in Notch activity resulted in failure of the cells to detach from the epithelium without affecting direction sensing. These observations provide new insight into the cellular dynamics and molecular mechanisms of cell migration in vivo. [Copyright &y& Elsevier]

Morphological forms of ZnO nanostructures play a vital role in deciding properties such as high internal surface area, efficient light scattering and harvesting, lowest charge transfer resistance, etc. which are important for photoelectrochemical (PEC) performance. Herein successful deposition of well oriented ZnO nanorods thin films over fluorine doped tin oxide (FTO) coated glass substrate is achieved by using simple, soft solution and scalable method known as successive ionic layer adsorption and reaction (SILAR). For the first time a compact ZnO layer over large area is deposited in one step synthesis approach, without any assistance of seed layer, by using hydrazine hydrate as a source of hydroxyl ions. The plausible growth mechanism of the morphological variation (alignment and orientation) happening with increasing SILAR cycles and its consequence on PEC performance are discussed in detail. All ZnO thin films show wurtzite crystal structure, however variations in their texture coefficients were found with SILAR cycles, which turns out to be a major aspect for PEC application. Anodic shift was observed in flat band potential values with increment in number of SILAR cycles. The ZnO thin films deposited for 120 cycles showed preferential orientation along (0002) plane and showed better PEC performance with photocurrent of 0.19 mA/cm2 (1 V) and maximum photo conversion efficiency of 0.084% at 0.45 V. On the other hand, film deposited for 60 (photocurrent of 0.11 mA/cm2 (1 V); efficiency of 0.055%) and 180 cycles (photocurrent of 0.15 mA/cm2 (1 V); efficiency of 0.063%) demonstrated inferior PEC performance. The texture coefficient and hence the photo conversion efficiency of ZnO nanorods vary with SILAR cycles. For 120 SILAR cycles higher texture coefficient and better photo conversion efficiency was found. Image 1 • SILAR depostion of ZnO thin films by using hydrazine hydrate. • Seed layer free well-orientated ZnO nanorods by using SILAR method. • Texture coefficient decides PEC performance of ZnO nanorods. [ABSTRACT FROM AUTHOR]

Hydrogen production via photoelectrochemical water splitting is a promising route to convert solar energy into chemical fuel, reducing energy crises and boosting environmental health. Here, we report the fabrication of ternary ZnO/CuO/Au heterostructures by electrodeposition and chemical bath deposition methods. The heterojunction formed can enhance the optical absorption, and photogenerated electrons and holes can efficiently separate due to the built-in electric field, which reduces recombination losses. Au plasmons incorporated in ZnO/CuO heterojunction enhance the optical absorption and promote fast free charge carrier transport at the interface through the surface plasmon resonance (SPR) effect. The ZnO/CuO/Au photoanode exhibits a photocurrent density of 1.08 mA/cm2 at 1.6 V Vs RHE, two times higher than pristine ZnO. The ZnO/CuO/Au photoanode exhibits the lowest charge transfer resistance of 600 Ω from electrochemical impedance spectra(EIS). The Bode plot revealed that the most extended lifetime of 8.69 μs is observed for ZnO/CuO/Au photoanode, which is larger than pristine ZnO. The synthesized thin films showed good stability and reusability for the photooxidation of water. • Fabrication of ternary ZnO/CuO/Au heterostructures by electrodeposition and chemical bath deposition methods. • Enhancement of optical absorption and reduction in recombination losses due to heterojunction. • Au plasmons incorporated in ZnO/CuO heterojunction enhances the optical absorption. • Au plasmons promote fast charge carrier transport at interface via surface plasmon resonance (SPR) effect. • ZnO/CuO/Au photoanode exhibits photocurrent density ∼ 1.08 mA/cm2, higher than pristine ZnO. [ABSTRACT FROM AUTHOR]

In this paper, we synthesized lead-free cesium bismuth iodide (Cs 3 Bi 2 I 9) perovskite films by solution process using one-step spin-coating technique. Formation of Cs 3 Bi 2 I 9 perovskite was confirmed by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy analysis. The XRD analysis showed that all Cs 3 Bi 2 I 9 perovskite films were polycrystalline in nature, with hexagonal crystal structure and preferred-orientation along (006) direction. The environmental stability of Cs 3 Bi 2 I 9 perovskite was confirmed by XRD analysis and UV–visible spectroscopy. Multiple XRD and UV–Vis spectra taken after long time spans revealed the stable nature of Cs 3 Bi 2 I 9 perovskite films. The UV–visible spectroscopy and photoluminescence analysis showed that the perovskite films absorbed strongly in the visible region and had an optical band gap of ~2.1 eV. Surface morphology of Cs 3 Bi 2 I 9 perovskite over the entire substrate surface was investigated using scanning electron microscopy. Thermo-gravimetric analysis showed that Cs 3 Bi 2 I 9 perovskite was thermally stable up to ∼ 420 °C. Finally, solar cells fabricated using Cs 3 Bi 2 I 9 perovskite material showed maximum power conversion efficiency (PCE) of 0.17%, with short circuit current density of 1.43 mA/cm2, open circuit voltage of 0.37 V and fill factor of 32%. Applying compositional engineering and optimizing the device structure should further improve the PCE. These results are a significant step toward fabrication of Cs 3 Bi 2 I 9 perovskite-based solar cells. • Synthesis of lead-free Cs 3 Bi 2 I 9 perovskite films by spin coating. • Films have hexagonal crystal structure with (006) preferred orientation. • Cs 3 Bi 2 I 9 perovskite is thermally stable up to ~420 °C. • Maximum power conversion efficiency is 0.17%. • A significant step toward fabricating Cs 3 Bi 2 I 9 perovskite based solar cells. [ABSTRACT FROM AUTHOR]