<p>Shiv Nadar University is a comprehensive, multidisciplinary, research-focused, and student-centric University offering a full range of academic programs at the undergraduate, postgraduate and doctoral level. With state-of-the-art infrastructure, the University comprises of academic wings, sophisticated labs, international standard sports facilities, amphitheaters, auditorium, conference rooms and smart classrooms. The University&rsquo;s goal is to become internationally recognized for the quality of its research and creative endeavors and their applicability to improving quality of life, generating new insights and expanding the boundaries of human knowledge creativity. Committed to excellence in teaching, research and service, the University aims to serve the higher education needs of India and the world beyond.</p>

Shiv Nadar University

(SoNS) School of Natural Sciences

A detailed electrochemical investigation of a series of iron complexes (biuret-modified tetraamido iron macrocycles FeIII-bTAML), including the first electrochemical generation of FeV(O), and demonstration of their efficacy as homogeneous catalysts for electrochemical water oxidation (WO) in aqueous medium are reported. Spectroelectrochemical and mass spectral studies indicated FeV(O) as the active oxidant, formed due to two redox transitions, which were assigned as FeIV(O)/FeIII(OH2) and FeV(O)/FeIV(O). The spectral properties of both of these high-valent iron oxo species perfectly match those of their chemically synthesised versions, which were thoroughly characterised by several spectroscopic techniques. The O−O bond-formation step occurs by nucleophilic attack of H2O on FeV(O). A kinetic isotope effect of 3.2 indicates an atom–proton transfer (APT) mechanism. The reaction of chemically synthesised FeV(O) in CH3CN and water was directly probed by electrochemistry and was found to be first-order in water. The pKa value of the buffer base plays a critical role in the rate-determining step by increasing the reaction rate several-fold. The electronic effect on redox potential, WO rates, and onset overpotential was studied by employing a series of iron complexes. The catalytic activity was enhanced by the presence of electron-withdrawing groups on the bTAML framework. Changing the substituents from OMe to NO2 resulted in an eightfold increase in reaction rate, while the overpotential increased threefold. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

World University root node

Chemistry

Chemistry - A European Journal

Electrochemical Formation of FeV(O) and Mechanism of Its Reaction with Water During O−O Bond Formation

Evolution of a self-organized molecular packing at the microscopic scale in a bulk heterojunction active layer is critical for improving the performance of organic solar cells. We demonstrate that the molecular-shape-induced effects improve the morphology of the ternary thin films as PC61BM molecules were added to the host binary blend, PTB7-Th:PC71BM. Compared to the binary PTB7-Th:PC71BM devices, the ternary devices with 20\% PC61BM content (relative to PC71BM) exhibited an enhanced efficiency, from 6.4\% to 8.5\%. In particular, we find that the spherical PC61BM molecules with better precipitation kinetics than ellipsoidal PC71BM alter the morphology of ternary thin film and modulate interfaces to expedite charge transport and collection by reducing various recombination losses. (Figure Presented). © 2017 American Chemical Society.

Physics

Journal of Physical Chemistry C

Molecular-Shape-Induced Efficiency Enhancement in PC61BM and PC71BM Based Ternary Blend Organic Solar Cells

Temperature-dependent photoluminescence (PL) of titanium oxide (TiO2) shows an evolution of blue emission when exposed to 50 keV Ar+ ions. The origin of observed PL has been examined by X-ray absorption near-edge spectroscopy (XANES) at Ti-K,L and O-K edges, revealing the reduction of ligand field splitting owing to the formation of oxygen vacancies (OVs) by destroying TiO6 octahedral symmetry. Detailed PL and XANES analyses suggest that the fluence (ions/cm2) dependent increase in OVs not only boosts the conduction electrons but also increases the density of holes in localized self-trapped exciton (STE) states near the valence band. Based on these observations, we propose a model in which doped conduction electrons are recombining radiatively with the holes in STE states for blue light emission. © 2017 American Chemical Society.

Impact of Self-Trapped Excitons on Blue Photoluminescence in TiO2 Nanorods on Chemically Etched Si Pyramids

Graphene oxide (GO) is a promising and remarkable nanomaterial that exhibits antimicrobial activity due to its specific surface-interface interactions. In the present work, for the first time, we have reported the antibacterial activity of GO-coated surfaces prepared by two different methods (Hummers' and improved, i.e., GOH and GOI) against bacterial biofilm formation. The bacterial toxicity of the deposited GO-coated surfaces was investigated for both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) models of bacteria. The mechanism of inhibition is different on the coated surface than that in suspension, as determined by measurement of the percentage inhibition of biofilm formation, Ellman's assay, and colony forming unit (CFU) studies. The difference in the nature, degree of oxidative functionalities, and size of the synthesized GO nanoparticles mitigates biofilm formation. To better understand the antimicrobial mechanism of GO when coated on surfaces, we were able to demonstrate that beside reactive oxygen species-mediated oxidative stress, the physical properties of the GO-coated substrate effectively inactivate bacterial cell proliferation, which forms biofilms. Light and atomic force microscopy (AFM) images display a higher inhibition in the proliferation of planktonic cells in Gram-negative bacteria as compared to that in Gram-positive bacteria. The existence of a smooth surface with fewer porous domains in GOI inhibits biofilm formation, as demonstrated by optical microscopy and AFM images. The oxidative stress was found to be lower in the coated surface as compared to that in the suspensions as the latter enables exposure of both a large fraction of the active edges and functionalities of the GO sheets. In suspension, GOH is selective against S. aureus whereas GOI showed inhibition toward E. coli. This study provides new insights to better understand the bactericidal activity of GO-coated surfaces and contributes to the design of graphene-based antimicrobial surface coatings, which will be valuable in biomedical applications. © 2017 American Chemical Society.

Life Sciences

Fulltext

ACS Omega

Graphene Oxide-Coated Surface: Inhibition of Bacterial Biofilm Formation due to Specific Surface-Interface Interactions

Journal of Vector Borne Diseases

Epidemiological and demographic characteristics of dengue at a tertiary care centre in Gujarat

The application of a NiO y /NiO x bilayer in resistive switching (RS) devices with x &gt; y was studied for its ability to achieve reliable multilevel cell (MLC) characteristics. A sharp change in resistance brought about by sweeping the voltage, along with an improved on/off ratio (&gt;103) and endurance (104) were achieved in the bilayer structure as compared to the single NiO x layer devices. Moreover, it was found that nonvolatile and stable resistance levels, especially the multiple low-resistance states of Cu/NiO y /NiO x /Pt memory devices, could be controlled by varying the compliance current. All the multilevel resistance states of the Cu/NiO y /NiO x /Pt bilayer devices were stable for up to 500 consecutive dc switching cycles, as compared to the Cu/NiO x /Pt single layer devices. The temperature-dependent variation of the high and low resistance states of both the bilayer and single layer devices was further investigated to elucidate the charge conduction mechanism. Finally, based on a detailed analysis of the experimental results, comparisons of the possible models for RS in bilayer and single layer memory devices have also been discussed. © 2016 IOP Publishing Ltd.

Nanotechnology

Multilevel programming in Cu/NiO y /NiO x /Pt unipolar resistive switching devices

In this study, a non-faradaic electrochemical impedance spectroscopy has been employed for estimation of caffeine concentration in beverages. Impedance spectra were recorded by using a two electrode system without adding any redox reagents in the measured solutions. Electrochemical impedance data of caffeine solutions in pure water and beverages were measured and an appropriate equivalent electrical circuit model is developed to help in this investigative analysis. The interaction of caffeine molecules with the electrodes was primarily correlated to the formation of electrical double-layer at modified interface. Overall system impedance (|Z|), inverse of solution resistance (1/RS) and constant phase element of the system were further investigated from the equivalent electrical circuit and plotted as a function of pure caffeine concentration. Finally, the results obtained from spiked diluted cola beverages were compared with the pure caffeine sample. © 2016 The Authors.

International Journal of Electrochemical Science

Equivalent circuit models and analysis of electrochemical impedance spectra of caffeine solutions and beverages

Titanium dioxide (TiO2) has rich physical properties with potential implications for both fundamental physics and new applications. To date, the main focus of applied research is to tune its optical properties, which is usually done via doping and/or nanoengineering. However, understanding the role of d electrons in materials and possible functionalization of d-electron properties are still major challenges. Herewith, within a combination of an innovative experimental technique, high-energy optical conductivity, and state-of-the-art ab initio electronic structure calculations, we report an emerging, novel resonant exciton in the deep ultraviolet region of the optical response. The resonant exciton evolves upon low-concentration Ta substitution in anatase TiO2 films. It is surprisingly robust and related to strong electron-electron and electron-hole interactions. The d- and f-orbital localization, due to Ta substitution, plays an unexpected role, activating strong electronic correlations and dominating the optical response under photoexcitation. Our results shed light on a new optical phenomenon in anatase TiO2 films and on the possibility of tuning electronic properties by Ta substitution. © 2016 American Physical Society.

Physical Review B

Emerging giant resonant exciton induced by Ta substitution in anatase TiO2: A tunable correlation effect

Post-deposition annealing mediated evolution of self-decorated Au nanoparticles (NPs) on chemically etched Si pyramids is presented. A distinct transformation of Si surfaces from hydrophilic to hydrophobic is initially found after chemical texturing, showing an increase in contact angle (CA) from 58°to 98°(±1°). Further improvement of hydrophobicity with CA up to ∼118°has been established after annealing a 10 nm thick Au-coated Si pyramids at 400°C that led to the formation of Au NPs on Si facets along with self-ordering at the pyramid edges. Detailed x-ray diffraction studies suggest the evolution of crystalline Au NPs on strained Si facets. Microstructural studies, however, indicate no mixing of Au and Si atoms at the Au/Si interfaces, instead of forming Au nanocrystals at 400°C. The improved hydrophobicity of Si pyramids, even with Au NPs can be explained in the light of a decrease in solid fractional surface area according to Wenzel's model. Moreover, a sharp drop in specular reflectance from Si pyramids in the range of 300-800 nm, especially in the ultraviolet region up to ∼0.4\% is recorded in the presence of Au NPs by ultraviolet-visible spectroscopy, reflecting the possible use in photovoltaic devices with improved antireflection property. © 2016 AIP Publishing LLC.

Journal of Applied Physics

Self-decorated Au nanoparticles on antireflective Si pyramids with improved hydrophobicity

To facilitate the development of new polymeric materials, we report the development of new heuristic models to predict the dielectric constant, band gap, dielectric loss tangent, and glass transition temperatures for organic polymers. A new set of features called infinite chain descriptors (ICDs) was designed and developed especially to characterize organic polymers, utilizing methods with minimal dependence on predefined fragment libraries. Machine learning models were built for the aforementioned properties incorporating best practices in the field such as objective feature selection, cross-validation and external test sets. All models produced in this study showed good performance in prediction. A web tool has been developed and has been made available that supports the input of novel structures. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2082–2091. © 2016 Wiley Periodicals, Inc.