The Perfect Imperfections in Electrocatalysts.

Modern day electrochemical devices find applications in a wide range of industrial sectors, from consumer electronics, renewable energy management to pollution control by electric vehicles and reduction of greenhouse gas. There has been a surge of diverse electrochemical systems which are to be scaled up from the lab-scale to industry sectors. To achieve the targets, the electrocatalysts are continuously upgraded to meet the required device efficiency at a low cost, increased lifetime and performance. An atomic scale understanding is however important for meeting the objectives. Transitioning from the bulk to the nanoscale regime of the electrocatalysts, the existence of defects and interfaces is almost inevitable, significantly impacting (augmenting) the material properties and the catalytic performance. The intrinsic defects alter the electronic structure of the nanostructured catalysts, thereby boosting the performance of metal-ion batteries, metal-air batteries, supercapacitors, fuel cells, water electrolyzers etc. This account presents our findings on the methods to introduce measured imperfections in the nanomaterials and the impact of these atomic-scale irregularities on the activity for three major reactions, oxygen evolution reaction (OER), oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). Grain boundary (GB) modulation of the (ABO3 )n type perovskite oxide by noble metal doping is a propitious route to enhance the OER/ORR bifunctionality for zinc-air battery (ZAB). The perovskite oxides can be tuned by calcination at different temperatures to alter the oxygen vacancy, GB fraction and overall reactivity. The oxygen defects, unsaturated coordination environment and GBs can turn a relatively less active nanostructure into an efficient redox active catalyst by imbibing plenty of electrochemically active sites. Obviously, the crystalline GB interface is a prerequisite for effective electron flow, which is also applicable for the crystalline surface oxide shell on metal alloy core of the nanoparticles (NPs). The oxygen vacancy of two-dimensional (2D) perovskite oxide can be made reversible by the A-site termination of the nanosheets, facilitating the reversible entry and exit of a secondary phase during the redox processes. In several instances, the secondary phases have been observed to introduce the right proportion of structural defects and orbital occupancies for adsorption and desorption of reaction intermediates. Also, heterogeneous interfaces can be created by wrapping the perovskite oxide with negatively charged surface by layered double hydroxide (LDH) can promote the OER process. In another approach, ion intercalation at the 2D heterointerfaces steers the interlayer spacing that can influence the mass diffusion. Similar to anion vacancy, controlled formation of the cation vacancies can be achieved by exsolving the B-site cations of perovskite oxides to surface anchored catalytically active metal/alloy NPs. In case of the alloy electrocatalysts, incomplete solid solution by two or more mutually immiscible metals results in heterogeneous alloys having differently exposed facets with complementary functionalities. From the future perspective, new categories of defect structures including the 2D empty spaces or voids leading to undercoordinated sites, the multiple interfaces in heterogeneous alloys, antisite defects between anions and cations, and the defect induced inverse charge transfer should bring new dimensionalities to this riveting area of research.

GC-MS based lemon grass metabolite analysis involved in the synthesis of silver nanoparticles and evaluation of photo-catalytic degradation of methylene blue.

Silver nanoparticles (AgNPs) is of great importance to scientific community due to their plethora of applications. Several plant extracts have been reported for synthesis of AgNPs. In this study, lemon grass was used as a reducing and capping agent to prepare AgNPs. The formation of AgNPs was confirmed by using UV-Vis spectra as AgNPs show a characteristic peak around 400 nm. Effect of pH, temperature and lemon grass extract to silver nitrate ratio was optimized using response surface methodology (RSM). Characterization of AgNPs was done using X-Ray Diffraction (XRD), Energy Dispersive X-Ray spectroscopy (EDX), Trasmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS). Gas Chromatography-Mass spectrometry (GC-MS), Energy Dispersive X-Ray spectroscopy and Fourier Transform-Infrared (FT-IR) spectroscopic analysis showed involvement of metabolites of lemon grass in the formation of AgNPs. Photo-catalytic activity of synthesized AgNPs was evaluated through degradation of organic pollutant methylene blue dye.

Assessing bone mineral changes in response to vitamin D supplementation using natural variability in stable isotopes of Calcium in Urine.

Osteoporosis is a chronic disease of public health importance, particularly in low and middle income countries. Measuring the bone mineral balance (BMB) in a non-invasive manner, and its response to different interventions, is critical to the definition of optimal strategies for its prevention and management. In this study, we demonstrate the usefulness of natural variability in calcium isotopes (δ44/40Ca) of urine and the derived BMB estimates as a biomarker of bone health and its responsiveness to interventions. Vitamin D3 is commonly used as a supplement for the prevention and treatment of osteoporosis, along with calcium supplements. We studied the effect of a short term vitamin D3 supplementation on changes in urine δ44/40Ca and the derived BMB. δ44/40Ca before and after the vitamin D3 supplementation yielded a statistically significant change (p = 0.050) with a positive δ44/40Ca enrichment. The mean derived BMB was net positive (0.04 ± 0.05) in comparison to a net negative value for the control group (-0.03 ± 0.01). These results indicate the potential usefulness of urinary natural δ44/40Ca and the derived BMB, which, along with bone mineral density could be used as a sensitive marker for precision in the prevention and treatment of osteoporosis.