Kinetics and mechanism of oxidation of substituted benzyl alcohols by polymer supported chromic acid

The reactions between substituted benzyl alcohols were found to proceed through ester formation. The ester thus formed decomposes in a slow step to produce chromium(IV). Since our oxidant was supported on a polymeric material the intermediate chromium(IV) will further oxidize another molecule of alcohol generating a free radical in a fast step. The free radical subsequently reacts with another oxidant site in the polymeric reagent in a fast step leading to the formation of chromium(V). The intermediate chromium(V) in the last step reacts with alcohol to produce an aldehyde. The activation parameters were also determined and the mechanism is predicted.     

RP-HPTLC densitometric determination and validation of vanillin and related phenolic compounds in accelerated solvent extract of Vanilla planifolia*

A simple, fast and sensitive RP-HPTLC method is developed for simultaneous quantitative determination of vanillin and related phenolic compounds in ethanolic extracts of Vanilla planifolia pods. In addition to this, the applicability of accelerated solvent extraction (ASE) as an alternative to microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE) and Soxhlet extraction was also explored for the rapid extraction of phenolic compounds in vanilla pods. Good separation was achieved on aluminium plates precoated with silica gel RP-18 F(254S) in the mobile phase of methanol/water/isopropanol/acetic acid (30:65:2:3, by volume). The method showed good linearity, high precision and good recovery of compounds of interest. ASE showed good extraction efficiency in less time as compared to other techniques for all the phenolic compounds. The present method would be useful for analytical research and for routine analysis of vanilla extracts for their quality control.     

Hierarchical Nanoflower Arrays of Co9S8-Ni3S2 on Nickel Foam: A Highly Efficient Binder-Free Electrocatalyst for Overall Water Splitting

Hydrogen production is vital for meeting future energy demands and managing environmental sustainability. Electrolysis of water is considered as the suitable method for H₂ generation in a carbon-free pathway. Herein, the synthesis of highly efficient Co₉S₈-Ni₃S₂ based hierarchical nanoflower arrays on nickel foam (NF) is explored through the one-pot hydrothermal method (Co₉S₈-Ni₃S₂/NF) for overall water splitting applications. The nanoflower arrays are self-supported on the NF without any binder, possessing the required porosity and structural characteristics. The obtained Co₉S₈-Ni₃S₂/NF displays high hydrogen evolution reaction (HER), as well as oxygen evolution reaction (OER), activities in 1 m KOH solution. The overpotentials exhibited by this system at 25 mA cm⁻² are nearly 277 and 102 mV for HER and OER, respectively, in 1 m KOH solution. Subsequently, the overall water splitting was performed in 1 m KOH solution by employing Co₉S₈-Ni₃S₂/NF as both the anode and cathode, where the system required only 1.49, 1.60, and 1.69 V to deliver the current densities of 10, 25, and 50 mA cm⁻², respectively. Comparison of the activity of Co₉S₈-Ni₃S₂/NF with the state-of-the-art Pt/C and RuO₂ coated on NF displays an enhanced performance for Co₉S₈-Ni₃S₂/NF both in the half-cell as well as in the full cell, emphasizing the significance of the present work. The post analysis of the material after water electrolysis confirms that the surface Co(OH)₂ formed during the course of the reaction serves as the favorable active sites. Overall, the activity modulation achieved in the present case is attributed to the presence of the open-pore morphology of the as formed nanoflowers of Co₉S₈-Ni₃S₂ on NF and the simultaneous presence of the surface Co(OH)₂ along with the highly conducting Co₉S₈-Ni₃S₂ core, which facilitates the adsorption of the reactants and subsequently its conversion into the gaseous products during water electrolysis.     

Radiological and hydrological implications of dissolved radon in alluvial aquifers of western India

Journal of Radioanalytical and Nuclear Chemistry - A study was undertaken to measure the dissolved radon (222Rn) concentration in parts of western India (Southwest Punjab) in order to evaluate its...     

Enhanced ionic conductivity in La3+ and Sr2+ co-doped ceria: carbonate nanocomposite

Ionics - A series of ceria-based nanocomposites consisting of Ce0.85La0.125Sr0.025O1.9125 (LSCO) and binary carbonate mixture Li2CO3–Na2CO3 (LNCO) have been prepared as functional...     

Distribution of uranium in groundwaters of Bathinda and Mansa districts of Punjab,India: inferences from an isotope hydrochemical study

This paper presents the isotope hydrochemical results of groundwaters from southwest Punjab for assessing the uranium contamination and evaluating the factors leading to elevated uranium concentration. A total of 35 samples covering shallow and deep zones were collected for hydrochemistry and isotopes. Uranium concentration ranges between 2.3 and 357 µg L^?1 and 66% of the samples are contaminated. Both shallow and deep zones show U contamination but high incidences are noticed in shallow zone. Hydrochemical correlations infer geological sources rather than anthropogenic sources responsible for U contamination. Isotopically there is no clear distinction between high and low U groundwater.     

The renaissance in redox flow batteries

Although redox flow batteries were invented as early as 1954, no system development took place until NASA demonstrated an Fe/Cr redox flow battery system in 1970s. In hibernation for several years, redox flow battery systems have begun to catch the attention of policy makers globally. The resurrection of redox flow batteries rests heavily on their techno-economic feasibility as large-scale energy storage systems for emerging grid network that are being developed by climate change mitigation industries, namely, wind and solar. This article reviews various redox flow battery technologies with a cost and market prognosis.     

Enantioselective Organo‐Photocatalysis Mediated by Atropisomeric Thiourea Derivatives

Can photocatalysis be performed without electron or energy transfer? To address this, organo‐photocatalysts that are based on atropisomeric thioureas and display lower excited‐state energies than the reactive substrates have been developed. These photocatalysts were found to be efficient in promoting the [2+2] photocycloaddition of 4‐alkenyl‐substituted coumarins, which led to the corresponding products with high enantioselectivity (77–96 % ee) at low catalyst loading (1–10 mol %). The photocatalytic cycle proceeds by energy sharing via the formation of both static and dynamic complexes (exciplex formation), which is aided by hydrogen bonding.     

Solid‐state NMR Study of the YadA Membrane‐Anchor Domain in the Bacterial Outer Membrane

MAS‐NMR was used to study the structure and dynamics at ambient temperatures of the membrane‐anchor domain of YadA (YadA‐M) in a pellet of the outer membrane of E. coli in which it was expressed. YadA is an adhesin from the pathogen Yersinia enterocolitica that is involved in interactions with the host cell, and it is a model protein for studying the autotransport process. Existing assignments were sucessfully transferred to a large part of the YadA‐M protein in the E. coli lipid environment by using ¹³C‐¹³C DARR and PDSD spectra at different mixing times. The chemical shifts in most regions of YadA‐M are unchanged relative to those in microcrystalline YadA‐M preparations from which a structure has previously been solved, including the ASSA region that is proposed to be involved in transition‐state hairpin formation for transport of the soluble domain. Comparisons of the dynamics between the microcrystalline and membrane‐embedded samples indicate greater flexibility of the ASSA region in the outer‐membrane preparation at physiological temperatures. This study will pave the way towards MAS‐NMR structure determination of membrane proteins, and a better understanding of functionally important dynamic residues in native membrane environments.