Department of Chemistry

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IIT Jodhpur

Hafnium dioxide (HfO2) nanoaggregates are synthesized by sol-gel and hydrothermal routes followed by hydrogen annealing at different time durations. The proposed study aims to explore the effect of hydrogen annealing time on the properties of HfO2 and also envisage the catalytic soot oxidation using HfO2 nanoaggregates. It is observed that annealing under a hydrogen atmosphere brought about substantial changes in certain attributes such as chemical and textural properties with marginal changes in some other properties like optical activity and band gap. The pristine HfO2 without hydrogen annealing showed a lower ignition temperature, whereas hydrogen annealed HfO2 for 2 h showed the best catalytic performance characterized by the soot combustion temperature (T50) in contrast to samples prepared at longer duration because of the higher surface adsorbed oxygen species in its widely distributed pores. © 2018 American Chemical Society.

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ACS Sustainable Chemistry and Engineering

Solution Processed Hafnia Nanoaggregates: Influence of Surface Oxygen on Catalytic Soot Oxidation

Fluorine chemistry has gained tremendous attention in the area of electrochemical energy devices such as lithium ion batteries, fuel cells and solar cells. With the advent of novel fluorinating systems, it is interesting to study the effect of fluorine on the electrochemical characteristics of such energy devices. In this study, an organo-fluorine compound, SelectfluorTM (F-TEDA) is used as a co-electrolyte with organic electrolyte, tetrabutyl ammonium tetrafluoroborate (TBABF4) to facilitate the formation of electrostatic double layer. F-TEDA is a commercially available N−F fluorinating agent existing as ion-pair resembling conventional electrolytes. The ionic conductivity of 0.5 M F-TEDA/TBABF4 is found to be 5.10 mS/cm that increases on introduction of ppm level of water indicating its sensitivity towards water. Symmetric Swagelok-type cells in two electrode geometry are fabricated using carbon cloth as electrodes and F-TEDA/TBABF4 as electrolyte. F-TEDA/TBABF4 in inert condition (Device C) exhibits superior supercapacitive behaviour in terms of high rate capability and capacitance retention. The devices are assembled in ambient and inert conditions to examine the influence of moisture on supercapacitor performance. Interestingly, device based on F-TEDA assembled in ambient condition despite of decrease in voltage window exhibits a remarkable increase in specific capacitance by 102 % with respect to control electrolyte. © 2018 Wiley-VCH Verlag GmbH &amp; Co. KGaA, Weinheim

ChemElectroChem

An Organo-Fluorine Compound Mixed Electrolyte for Ultrafast Electric Double Layer Supercapacitors

We analyse Ping-Pong protocol from the point of view of a game. The analysis helps us in understanding the different strategies of a sender and an eavesdropper to gain the maximum payoff in the game. The study presented here characterizes strategies that lead to different Nash equilibriums. We further demonstrate the condition for Pareto optimality depending on the parameters used in the game. Moreover, we also analysed LM05 protocol and compared it with PP protocol from the point of view of a generic two-way QKD game with or without entanglement. Our results provide a deeper understanding of general two-way QKD protocols in terms of the security and payoffs of different stakeholders in the protocol. © 2017 Elsevier B.V.

Fulltext

Physica A: Statistical Mechanics and its Applications

Game-theoretic perspective of Ping-Pong protocol

Different aluminum and calcium based particles, montmorillonite (MMT), zeolites (NaY), bayerite (BAY) and hydroxyapatite (CaHAp), were compared and evaluated for water defluorination. The effect of parameters such as temperature of the medium, concentration (mass of adsorbent), reaction time and pH on the defluorination capacity were studied for the particles with best performance. MMT and CaHAp adsorbents showed increased fluoride rejections in batch experiments (≈45 and 100%). The defluorination capacity of MMT is influenced by the concentration and pH, while for CaHAp is independent of the evaluated parameters within the measured range. Further, polymer composite membranes based on poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) and the adsorbents with higher defluorination capacity were prepared by thermally induced phase separation in order to produce active filters for fluoride removal from water. The composite membranes presented a homogeneous porous structure with degrees of porosity ranging between ≈20 and 76% and average pore size in the micron range. The permeability of the composite membranes ranged between 12,500 and 10,000 L/h·m2·bar. A maximum fluoride rejection of 68% was obtained after 6 filtrations for the CaHAp/P(VDF-HFP) composite membranes. Thus, the composite membranes of P(VDF-HFP) with MMT and CaHAp show suitable performance for defluorination in water purification systems. © 2018 Elsevier B.V.

Separation and Purification Technology

Highly efficient removal of fluoride from aqueous media through polymer composite membranes

Futuristic healthcare technology including glucose sensors demands wearable components that ought to be transparent and flexible. Nickel nanostructures have proven to be highly efficient as electrocatalysts for glucose sensors. In this study, we explore single-source precursors of nickel alkylthiolate, Ni(SR)2, complexes as active electrode materials and coat them on a transparent gold (Au) mesh network to fabricate a transparent and highly efficient glucose sensor. The metal thiolate complex is electrooxidized in the alkaline medium by repeated cyclic voltammetry measurements to give rise to Ni redox-active centers with sharp anodic and cathodic peaks. Among different chain length metal alkylthiolates, nickel butanethiolate with the shortest carbon chain (C4) is found to be the most efficient in retaining sharp oxidation at low potential value and high current density. The electrochemical property of nickel butanethiolate toward glucose oxidation is examined on different electrode surfaces such as Au thin film, Au mesh, and fluorine-doped tin oxide (FTO). Interestingly, glucose oxidation takes place most efficiently on a Au mesh network compared to Au film and FTO substrates. The Ni(SC4H9)2/Au mesh exhibited two linear ranges of detection from 0.5-2 and 2-11 mM with a sensitivity value of 675.97 μA mM-1 cm-2 and a limit of detection of 2.2 μM along with excellent selectivity and reproducibility. The present study demonstrates that nickel butanethiolate on a Au mesh acts as a promising functional and transparent electrode material with the possibility of large-scale production for practical glucose detection. Copyright © 2018 American Chemical Society.

ACS Applied Nano Materials

Metal wire networks functionalized with nickel alkanethiolate for transparent and enzymeless glucose sensors

Emeraldine salt of polyaniline-coated copper substrate was used as a cathode to study hydrogen evolution reaction in 1M H2SO4. Hydrogen evolution reaction in acidic medium followed Grotthus mechanism, where proton hops randomly on the surface of polyaniline. With Randles-Sevcik equation, the average value of diffusion coefficient for H+ on polyaniline was calculated to be 2.66 times higher than that in the literature data. This higher value explicitly supported the rapid diffusion of H+ on polyaniline surface from the bulk electrolyte solution. With the help of a phenomenological thermodynamic approach demonstrated elsewhere, the solvent-modified work function of polyaniline-coated copper in acidic medium was calculated. The plot of exchange current density versus solvent-modified work function of different metals and polyaniline-coated copper indicated that at lower work function polyaniline-coated copper showed higher exchange current density and the rate of hydrogen evolution was much higher on polyaniline-coated copper than on copper. This was further confirmed by gas chromatography, and 13C and 1H nuclear magnetic resonance studies supported the mechanism proposed. From linear sweep voltammetry analysis, it was observed that the total capacity of hydrogen stored on polyaniline-coated copper was approximately 1.85 times higher than that on copper. Copyright © 2017 John Wiley & Sons, Ltd.

International Journal of Energy Research

Storage and evolution of hydrogen in acidic medium by polyaniline

An efficient domino Michael-Michael reaction of ω- and δ-nitro α,β-unsaturated esters with alkylidenepyrazolones has been accomplished using DABCO as the organocatalyst under mild reaction conditions. Under the present organocatalytic method, a wide range of carbocyclic spiro-pyrazolones with three tertiary stereogenic centers and a quaternary stereocenter has been prepared in high yields and excellent diastereoselectivities. An ester and nitro groups present in the spiro-pyrazolones have been utilized for further structural transformations. © 2018

Tetrahedron

A facile and highly diastereoselective synthesis of carbocyclic spiro-pyrazolones via DABCO catalyzed Michael-Michael domino reaction

Self assemblies of (N2O4) salen-type bi-compartmental ligand (H2L°Me) [N,N′-Bis(3-methoxysalicylidenimino)-1,3-diaminopropane] afforded two series of complexes, a trinuclear nitrate [Cd3(L°Me)2(NO3)2] (1) and a dinuclear (η1-N3) [Zn2(L°Me)(η1-N3)2(CH3OH)2] (2). Elemental analysis, UV-visible and Fourier transform Infrared spectroscopic methods were employed successfully to characterize the complexes. Single-crystal X-ray studies reveal that complex 1 consists of planar trinuclear Cd(II)3 core coordinated by two fully deprotonated dianionic ligands [L1]2− and nitrato (NO3 −) bridging but complex 2 is a centrosymmetric hexacoordinated Zn(II) double end-on azide (η1-N3) with methanol as co-ligands. Both complexes satisfied a common 4-membered M(II)2(μ2-O)2 basic structural core. Fluorescence properties in DMSO solvent reveal that complexes enhance appreciably the fluorescence behavior over free salen-type ligand (H2L°Me). Complexes are optimized using Density functional theory calculated at B3LYP/TZVP level of theory to obtain insights into optimized structure, Frontier molecular orbital, Electrostatic potential maps, charge analyses gives an insight into the electronic structure and charge/potential distribution in the molecule etc. which substantiate the experimentally observed supramolecular interactions. Existing different non-covalent supramolecular interactions have been explained by means of Hirshfeld surface and 2D fingerprint plot analysis. Further theoretical explanations for the observed experimental electronic spectra of both complexes were explained by using Time-dependent density functional theory level of calculations. © 2018 Wiley-VCH Verlag GmbH &amp; Co. KGaA, Weinheim

Department of Computer Science & Engineering

ChemistrySelect

Nitrato, Pseudohalo-Linked Zn(II)/Cd(II) Schiff-Base Complexes with 1,3-Diimine Spacer Group: Syntheses, Crystal Structures, DFT, TD-DFT and Fluorescence Studies

This paper is a study of ZnO doped TiO2 in various percentages ranging from 0% (undoped) up to 10%. The effect of doping was observed via the change in morphological, optical, electrical and physical properties of ZnO-TiO2 nanospheres. Hydrothermally grown nanospheres are used for removing contaminants photo-catalytically from waste water and also as photoanodes in dye-sensitized solar cells (DSSCs) with graphene as counter electrode. Of the many approaches that have been explored for purification of contaminated water, this work presents designing of an environmental friendly solution, based on easily available filter paper membrane and incorporating it with the synthesized catalyst for photodegradation of the harmful toxic substances. These reusable membranes assist in the photodegradation process by creating room for better light-catalyst-dye interaction via large surface sites. The spherically structured heterojunction of ZnO-TiO2 generates excitons that oxidize methyl orange (MO) and reduce harmful Cr(VI) to non-toxic Cr(III) with high efficacy. Additionally, the agile nanostructures were employed as efficient photoanode material by fabricating dye sensitized solar cells with graphene as counter electrode. © 2018 Wiley-VCH Verlag GmbH &amp; Co. KGaA, Weinheim

Engineered ZnO-TiO2 Nanospheres for High Performing Membrane Assimilated Photocatalytic Water Remediation and Energy Harvesting

We analyse the role of degree of entanglement for Vaidman's game in a setting where the players share a set of partially entangled three-qubit states. Our results show that the entangled states combined with quantum strategies may not be always helpful in winning a game as opposed to the classical strategies. We further find the conditions under which quantum strategies are always helpful in achieving higher winning probability in the game in comparison to classical strategies. Moreover, we show that a special class of W states can always be used to win the game using quantum strategies irrespective of the degree of entanglement between the three qubits. Our analysis also helps us in comparing the Vaidman's game with the secret sharing protocol. Furthermore, we propose a new Vaidman-type game where the rule maker itself is entangled with the other two players and acts as a facilitator to share a secret key with the two players. © 2017 IEEE.