Arvind H. Jadhav

An efficient and heterogeneous recyclable silicotungstic acid with modified acid sites as a catalyst for conversion of fructose and sucrose into 5-hydroxymethylfurfural in superheated water

Acidity modified silver exchanged silicotungstic acid (AgSTA) catalyst was prepared and characterized by X-ray diffraction, FT-IR spectroscopy, Raman spectroscopy, FT-IR pyridine adsorption, SEM imaging, EDX mapping, and antimicrobial activity was also tested. The catalytic activity was evaluated for the dehydration of fructose and sucrose in superheated water. As a result, 98% conversion of fructose with 85.7% HMF yield and 87.4% HMF selectivity in 120 min reaction time at 120 °C reaction temperature using 10 wt.% of AgSTA catalyst was achieved. While, 92% sucrose conversion with 62.5% of HMF yield was obtained from sucrose at uniform condition in 160 min. The effect of reaction parameters, such as reaction temperature, time, catalyst dosage, and effect acidity on HMF yield was also investigated. The AgSTA catalyst was separated from the reaction mixture by filtration process at end of the reaction and reused eight times without loss of catalytic activity.

Hierarchical Mesoporous 3D Flower-like CuCo2O4/NF for High-Performance Electrochemical Energy Storage.

Ternary spinel CuCo2O4 nanostructure clenches great potential as high-performance electrode material for next-generation energy storage systems because of its higher electrical conductivity and electrochemical activity. Carbon free and binder free 3D flower-like CuCo2O4 structure are grown on nickel foam (NF) via a facile hydrothermal synthesis method followed by annealing. The obtained CuCo2O4/NF is directly used as electrode for lithium ion batteries (LIBs) and supercapacitors (SCs) application. The electrochemical study of 3D flower-like CuCo2O4 as an electrode for LIB and SC shows highly mesoporous unique architecture plays important role in achieving high capacity/capacitance with superior cycle life. The high surface area and mesoporous nature not only offer sufficient reaction sites, but also can accelerate the liquid electrolyte to penetrate electrode and the ions to reach the reacting sites. In outcome, it exhibits highest capacity of 1160 mA h g−1 after 200 cycles when used as an anode for LIB and specific capacitance of 1002 F g−1 after 3000 cycles. The superior electrochemical of synthesized material is attributed to direct contact of electrode active material with good intrinsic electrical conductivity to the underneath conductive NF substrate builds up an express path for fast ion and electron transfer.

Esterification of carboxylic acids with alkyl halides using imidazolium based dicationic ionic liquids containing bis-trifluoromethane sulfonimide anions at room temperature

Task-specific room temperature ionic liquids (RTILs) composed of symmetrical N-methylimidazolium rings linked with a short oligo (ethylene glycol) chain (cationic part) and bis-trifluoromethane sulfonimide (NTf2, anionic part) were successfully synthesized, and their physicochemical properties were determined by various modern analytical techniques. The catalytic activity of the synthesized RTILs was evaluated in the esterification reaction of acids with alkyl halides in solvent-free conditions at room temperature. From the screening test, all the synthesized RTILs showed a high yield with significant selectivity for respective esters in a very short reaction time. Especially, 0.1 equimolar of RTIL-1 ([tetraEG(mim)2][NTf2]2) was found to be, the most efficient and reusable catalyst for this reaction. As a result, 100% conversion and up to a 94% yield of the respective ester product was obtained in a 30 min reaction time. This might be due to their synergetic effect of Lewis acidity, wide liquid range, and high miscibility compared to the other homogeneous and heterogeneous catalysts. Beside this, RTIL was easily separated from the reaction mixture and reused several times without any significant loss of catalytic activity and structural property. The present dicationic ionic liquids (ILs) under a solvent-free catalytic system were found to be kinetically fast, naturally benign, and achieved good yields for esterification of carboxylic acids with alkyl halides.

Green solvent ionic liquids: structural directing pioneers for microwave-assisted synthesis of controlled MgO nanostructures

Magnesium oxide (MgO) is one of the auspicious metal oxides which attracts much attention because of its superior performance in scientific applications. Controlled facial arrangement of MgO nanostructures with tailored properties is highly important in nanotechnology and nanoscience. Here, various MgO nanostructures were obtained via one-pot microwave (MW)-assisted synthesis in various structural directing ionic liquids (ILs). These selected ILs are based on monocationic and dicationic moieties which consist of N-methyl imidazolium and 3-methyl pyridinium cations with various halide anions. Different designer solvents with respect to their counter anions produced various nanostructures, varying from nanoflakes, interconnected nanoparticles, hexagonal nanoparticles, irregular nanoparticles and nanocapsules. In this method, green solvent ILs not only act as solvent but also act as structural directing agents. In addition, a plausible mechanism of nanomaterial formation under MW irradiation in the presence of ILs was also determined. Formation of hydrogen bonding with favorable π–π interactions by simply tailoring the IL structures by means of MW conditions is the key factor for the development of different morphology. To define the catalytic activity of the prepared nanostructures, a Claisen condensation reaction was performed. The results showed that all the nanostructures have efficient catalytic activity due to their tailored structure, basicity, and surface area. Particularly, a catalytic amount of hexagonal morphology MgO obtained from dicationic [C4(mIm)2Cl2] IL showed 100% conversion and a remarkable 95% selective yield of the respective product. The proposed approach for nanomaterial preparation does not require an additional template and harsh reaction conditions which establishes this as a simple method to reduce the cost of production using environmentally benign solvents.

Solvent free synthesis of 1,5-benzodiazepine derivatives over the heterogeneous silver salt of silicotungstic acid under ambient conditions

1,5-Benzodiazepine derivatives were synthesized using prepared silver substituted silicotungstic acid (AgSTA) salt as a heterogeneous catalyst under solvent free conditions at room temperature. The solid AgSTA catalyst was synthesized and characterized by X-ray diffraction, FTIR spectroscopy, Raman spectroscopy, FTIR pyridine adsorption, SEM imaging, EDX mapping, and antimicrobial activity was also tested. The AgSTA catalyst showed tremendous catalytic activity in the synthesis of 1,5-benzodiazepine derivatives under solvent free conditions. As a result, 100% conversion of reactants and up to 88.0% yield of 1,5-benzodiazepine in 40 min reaction time were achieved using 10 wt% of AgSTA catalyst. The solid AgSTA catalyst was separated from the reaction mixture by a simple filtration process at the end of the reaction and reused for five cycles without significant loss of catalytic activity and selectivity. The present environmentally benign, solvent free catalytic system is found to be a very convenient, fast, high yielding, and clean method for the synthesis of 1,5-benzodiazepine derivatives.

A silica nanoparticle supported fluorescence “turn-on” fluoride ion sensing system with tunable structure and sensitivity

Amino-silane modified silica nanoparticles (SNP-APTMS and SNP-TMSPEDA) doped with silyl-ether protected fluorescein isothiocyanate (FITC-OSMDBT) were synthesized via a sol–gel method in a simple three-step reaction to give fluoride ion probes SNP-TMSPEDA-FITC-OSMDBT (sensor A) and SNP-APTMS-FITC-OSMDBT (sensor B). The sensors were characterized using FT-IR, EDX, TGA, and fluorescence spectroscopy. It was observed that, at fluoride ion and FITC-OSMDBT mole equivalent titration ratio of x : x, the emission spectra of both sensors were similar when x = 1.0; however, at x = 3.0, 6.0, and 9.0, sensor B displayed 3 fold the emission intensity of sensor A. This phenomenon was attributed to non-radiative emission energy transfer mechanisms, which were controlled by the FITC-OSMDBT loading. The steric hindrance difference present on N-[3-(trimethoxysilyl) propyl] ethylenediamine (TMSPEDA) and (3-aminopropyl)trimethoxysilane (APTMS) ensured that different amounts of FITC-OSMDBT were loaded on each sensor. At x = 3.0, 6.0, and 9.0, the emission intensity increased linearly with [F−] in DMSO; thus, from the working curve of sensor A, the fluoride ion detection range of sensor B could be calculated and vice versa. The structure of the sensing system being proposed is simple, sensitive to F−, and may prove useful with respect to the development of fluoride anion sensors with structures which can be easily modified to produce sensors with varying detection ranges.

Preparation and Application of Supramolecular Assembled β-cyclodextrin/polyacrylonitrile Composite Nanofibers as a Highly Efficient Adsorbent for Dye Removal

β-cyclodextrin (β-CD) incorporated polyacrylonitrile (PAN) composite nanofibers were successfully prepared by using electrospinning technique and used as a novel adsorbent for the elimination of dyes from aqueous solution. The formations of bead-free and uniform nanofibers were obtained using various compositions of homogeneous solution of β-CD and PAN in N,N-dimethylformamide (DMF). The morphology and structure of nanofibers were determined and characterized by SEM, XRD, TGA, and FTIR analysis. The adsorption performance of prepared nanofibers was examined by using methylene blue (MB) and methyl violet (MV) as adsorbate. Results showed that β-CD/PAN nanofibers were achieved equilibrium point within 2h with 96.21 % and 94.37 % adsorption of MV and MB, respectively at ambient condition. In addition, adsorption capacity of nanofibers was studied under different experimental conditions and their effects on adsorption capacity such as temperature, pH, and contact time. The regeneration of β-CD/PAN nanofibers were carried out using methanol and re used five times as an adsorbent, Results indicates that regenerated adsorbent was adsorb 89.0% and 85.22 % of MV and MB, respectively in 5th cycle.