Reduced Graphene Oxide Supported Silicotungstic Acid for Efficient Conversion of Thiols to Disulfides by Hydrogen Peroxide

Reduced graphene oxide (RGO) supported silicotungstic acid (STA) as a redox catalyst (STA-RGO) for efficient conversion of thiols to disulfide was prepared with an impregnation method. The catalyst was characterized by XRD, FTIR, UV–vis, TEM techniques, and zeta potential measurements. The uniform distribution of the STA on RGO was indicated by broadening of the XRD peaks of RGO. The Keggin unit of STA on the prepared catalyst was found to remain intact as noticed by FTIR. The increase in negative zeta potential and shifts in the characteristic UV–vis absorption bands of STA-RGO as compared with pure STA and RGO indicate the interaction between the two. The prepared catalyst was found to facilitate the oxidation of various thiols to their corresponding disulfides in the presence of hydrogen peroxide as an oxidant at room temperature. A probable mechanism involving sufenic acid as an intermediate is proposed

Surface plasmon resonance based colorimetric probe for vitamin B1 detection: Applications to bio-fluid analysis

This study reports simple analytical approach for thiamine (Vitamin B1) detection based on induced aggregation and alternation in colorimetric properties of gold nanoparticles (AuNPs), which was synthesized through citrate reduction approach. Furthermore, the citrate capped AuNPs are characterized by various analysing tools. The addition of thiamine persuades the aggregation of citrate-AuNPs and further leading to red to blue colour transition with decrease in absorbance intensity. The proposed method achieves good linearity with a correlation coefficient of 0.9843. By using our proposed strategy, thiamine was detected by unassisted vision as well as absorption spectroscopy. Under the most favorable condition method achieves good linear relationship between concentration range 0.01–0.8 μg mL−1 with limit of detection of 0.0067 μg mL−1. Under the premium condition, the method offers excellent selectivity towards thiamine detection in presence of different interfering species. Further practical applicability of the method was checked by using blood serum and urine sample via standard addition method. The obtained recoveries were acceptable in the range of 98.70–102.97% for added thiamine concentration. Thus, the proposed method may emerge as a target specific and highly sensitive tool towards thiamine detection

Enhanced Photoelectrochemical Solar Water Splitting Using a Platinum-Decorated CIGS/CdS/ZnO Photocathode

A Cu­(InGa)­Se₂ film was modified with CdS/ZnO for application to solar water splitting. Platinum was electrodeposited on the ZnO layer as a hydrogen evolution catalyst. The effects of the electroplating time and acidity level of the electrolyte on the photocurrent density were studied. The highest photocurrent density of −32.5 mA/cm² under 1.5 AM illumination was achieved with an electroplating time of 30 min at a pH of 9. This photocurrent density is higher than those reported in previous studies. The markedly high performance of the CIGS/CdS/ZnO photocathode was rationalized in terms of its type II cascade structure that facilitated efficient charge separation at the interface junction

Nanotextured Pillars of Electrosprayed Bismuth Vanadate for Efficient Photoelectrochemical Water Splitting

We demonstrate, for the first time, electrostatically sprayed bismuth vanadate (BiVO₄) thin films for photoelectrochemical water splitting. Characterization of these films by X-ray diffraction, Raman scattering, and high-resolution scanning electron microscopy analyses revealed the formation of nanotextured pillar-like structures of highly photoactive monoclinic scheelite BiVO₄. Electrosprayed BiVO₄ nanostructured films yielded a photocurrent density of 1.30 and 1.95 mA/cm² for water and sulfite oxidation, respectively, under 100 mW/cm² illumination. The optimal film thickness was 3 μm, with an optimal postannealing temperature of 550 °C. The enhanced photocurrent is facilitated by formation of pillar-like structures in the deposit. We show through modeling that these structures result from the electrically-driven motion of submicron particles in the direction parallel to the substrate, as they approach the substrate, along with Brownian diffusion. At the same time, opposing thermophoretic forces slow their approach to the surface. The model of these processes proposed here is in good agreement with the experimental observations

Platinum-decorated Cu(InGa)Se2/CdS photocathodes: Optimization of Pt electrodeposition time and pH level

Photoelectrochemical (PEC) water splitting was performed using co-evaporated Cu(In, Ga) Se-2 (CIGS, p-type) films as the photocathode. Pt was electrodeposited on CIGS and CIGS/CdS films. The effect of the electrodeposition time was investigated to determine the optimal deposition conditions. The CIGS film was covered with a 60-nm-thick CdS layer (n-type) using a chemical-bath deposition technique, which created a p-n junction. The effect of the Pt electroplating time was again investigated for the CIGS/CdS films; thus, the effect of CdS addition could be quantitatively investigated. The effect of the pH of 0.5 M Na2SO4 electrolyte was also investigated. The optimal water-splitting performance occurred at -24.16 mA/cm(2) at -0.7 V vs. Ag/AgCl with a Pt electrodeposition time of 20 min and pH 9. The CIGS/ CdS films were characterized by X-ray diffraction, scanning electron microscopy, and focused-ion beam transmission electron microscopy.clos

Observation of Gravitational Waves from the Coalescence of a 2.5−4.5 M⊙2.5-4.5~M_\odot Compact Object and a Neutron Star

International audienceWe report the observation of a coalescing compact binary with component masses $2.5-4.5~M_\odot$ and $1.2-2.0~M_\odot$ (all measurements quoted at the 90% credible level). The gravitational-wave signal GW230529_181500 was observed during the fourth observing run of the LIGO-Virgo-KAGRA detector network on 2023 May 29 by the LIGO Livingston Observatory. The primary component of the source has a mass less than $5~M_\odot$ at 99% credibility. We cannot definitively determine from gravitational-wave data alone whether either component of the source is a neutron star or a black hole. However, given existing estimates of the maximum neutron star mass, we find the most probable interpretation of the source to be the coalescence of a neutron star with a black hole that has a mass between the most massive neutron stars and the least massive black holes observed in the Galaxy. We estimate a merger rate density of $55^{+127}_{-47}~\text{Gpc}^{-3}\,\text{yr}^{-1}$ for compact binary coalescences with properties similar to the source of GW230529_181500; assuming that the source is a neutron star-black hole merger, GW230529_181500-like sources constitute about 60% of the total merger rate inferred for neutron star-black hole coalescences. The discovery of this system implies an increase in the expected rate of neutron star-black hole mergers with electromagnetic counterparts and provides further evidence for compact objects existing within the purported lower mass gap