Department Of Chemistry
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Item Recent advances in the C(1)-functionalization of tetrahydroisoquinolines via multicomponent reactions(Springer, 2020) Kaur, P; Kumar, R.(Figure presented.) 1,2,3,4-Tetrahydroisoquinoline is an important structural motif of various natural products and therapeutic lead compounds. In recent years, considerable research interest has been witnessed toward synthesis of its C(1)-substituted derivatives, since they can act as precursors for various alkaloids displaying multifarious biological activities. This minireview offers short and non-exhaustive epitome of various multicomponent reactions for the C(1)-functionalization of 1,2,3,4-tetrahydroisoquinolines. In particular, reactions involving isomerization of iminium intermediate (exo/endo isomerization) are highlighted for the period of 2013-2019. - 2020, Springer Science+Business Media, LLC, part of Springer Nature.Item Fabrication of mesoporous titanium dioxide using azadirachta indica leaves extract towards visible-light-driven photocatalytic dye degradation(Elsevier, 2020) Dash, L; Biswas, R; Ghosh, R; Kaur, V; Banerjee, B; Sen, T; Patil, R.A; Ma, Y.-R; Haldar, K.K.An environmental benign, straightforward and financially savvy technique has been developed to fabricate mesoporous titanium dioxide (TiO2) nanostructure utilizing Azadirachta indica leaves extract. The aqueous extract of Azadirachta indica leaves act as a template which upon calcination at high temperature generated mesoporous TiO2. The structure of the mesoporous TiO2 was confirmed by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and isothermal gas adsorption-desorption (BET). It has been found that the crystallinity and pore diameter of mesoporous titanium dioxide (TiO2) depends on the amount of Azadirachta indica leaves extract, resulting in enhanced crystallinity with an increasing amount of Azadirachta indica leaves extract. The pore diameter was found somewhere in the range from 16.67 to 46.19 nm, and the BET surface area varies from 8.55–157.35 m2/g.. Finally, we have explored as-synthesized mesoporous TiO2 for visible-light-driven photocatalytic degradation of rhodamine 6 G (R6 G) dye. It is noteworthy that the photocatalytic degradation rate of R6 G in presence of as-synthesized mesoporous TiO2 depends only on the amount of plant extract used and not on temperature and other factors. This is presumably due to the increased optical band gap of TiO2. - 2020 Elsevier B.V.Item Copper hydride clusters in energy storage and conversion(Royal Society of Chemistry, 2019) Dhayal, R.S; Van Zyl ,W.E; Liu, C.W.Hydrogen is seen as an increasingly important clean and sustainable energy source going into the future. There are a host of materials being investigated for the storage of hydrogen. In this frontier, we provide an overview of hydride clusters derived from Earth-abundant copper being used for the storage and conversion of hydrides into hydrogen, and the reaction of CO2 with hydride sources to produce the formic acid/formate pairing, which are considered excellent hydrogen carriers. We summarize the main synthesis methods to stabilize high-nuclearity hydride clusters with phosphine, N-heterocyclic carbene, and in particular phosphor-1,1-dithiolate ligands. Unprecedented structures and hydride geometries have been revealed through both X-ray and neutron single crystal analyses. We point to the release of hydrogen in such hydride clusters through solar irradiation, thermolysis and acid treatments. Finally, we show the facile formation of rhombic nanoparticle copper morphologies derived from accurately determined high-nuclearity clusters and suggest that this could provide a mechanism that links molecular structures with bulk microstructures of materials. © 2019 The Royal Society of Chemistry.Item Structural, kinetic and thermodynamic characterizations of SDS-induced molten globule state of a highly negatively charged cytochrome c(Oxford University Press, 2019) Jain, R; Sharma, D; Kumar, Rakesh; Kumar, RajeshThis study presents the structural, kinetic and thermodynamic characterizations of previously unknown submicellar concentrations of SDS-induced molten globule (MGSDS) state of a highly negatively charged basedenatured ferricytochrome c (U B -state) at pH ∼12.8 (±0.2). The far-UV CD, near-UV CD, ANS-fluorescence data of UB-state in the presence of different concentrations of SDS indicate that the submicellar concentrations of SDS (≤0.4mM) transform the UBstate to MG SDS -state. The MG SDS -state has nativelike α-helical secondary structure but lacks tertiary structure. The free energy change (ΔG° D) for U B → MG SDS transition determined by far-UV CD (∼2.7 kcal mol -1 ) is slightly higher than those determined by fluorescence (∼2.0 kcal mol -1 ) at 25°C. At very low SDS and NaCl concentrations, the MG SDS -state undergoes cold denaturation. As SDS concentration is increased, the thermal denaturation temperature increases and the cold denaturation temperature decrease. Kinetic experiments involving the measurement of the CO-association rate to the base-denatured ferrocytochrome c at pH ≈12.8 (±0.2), 25°C indicate that the submicellar concentrations of SDS restrict the internal dynamics of base-denatured protein. © The Author(s) 2018. Published by Oxford University Press on behalf of the Japanese Biochemical Society. All rights reserved.Item Au/CdSe hybrid nanoflowers: a high photocurrent generating photoelectrochemical cells(Springer, 2019) Haldar, Krishan Kant; Biswas, R; Patra, A; Halder, K.K; Sen, T.Photoelectrochemical cell composed of solution-processed nanoflower heterostructure of Au core and eight CdSe petals was investigated for enhanced photocurrent generation. The electrode of CdSe nanorods displayed photocurrent density of 2.1 mA/cm 2 whereas the Au core CdSe nanoflower exhibited 4.6 mA/cm 2 corresponding to a 119% increase during photoelectrochemical cell performance. Both electrodes showed prompt response to the on/off cycles of light, the photocurrent gain (I Photon /I dark ) in CdSe nanorods is 124.7, while the value is 223.3 for Au/CdSe nanoflower, calculated from the growth-decay curves. Photoresponse time was dramatically improved for Au/CdSe nanoflower samples due to increasing in 66% incident photon-to-current emission. Electron lifetime of 21.63 and 48.71 ns was observed for the electrode of CdSe nanorods and Au/CdSe nanoflowers respectively. The prolonged electron lifetime in the case of the electrode of Au/CdSe nanoflowers was responsible for improving charge separation and as a consequence, higher photocurrent generation. © 2018, Springer Nature Switzerland AG.Item Zn(II) Di-isobutyldithiocarbamate Complex Enabled Efficient Synthesis of Au/ZnS Nanocomposite Core-shell in One Pot(Wiley, 2019) Biswas, R; Singh, H; Banerjee, B; Haldar, Krishan KantHere, we demonstrate a one pot synthesis of gold/zinc sulphide (Au/ZnS) core-shell type composite nanostructure via thermal decomposition of single molecular precursor Zn(II)di-isobutyldithiocarbamate complex. In these Au/ZnS core-shell type hybrid nanostructures where ZnS quantum dots are assembled onto Au nanoparticles surface were prepared via a facile and reproducible approach under mild conditions. The crystalline nature and interface of these Au/ZnS core-shell type composite nanostructures were confirmed by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), High-resolution transmission electron microscopy (HRTEM) and inverted TEM images. Here Zn(II)di-isobutyldithiocarbamate complex acts as ZnS source as well as reducing and stabilizing agent for Au 0 at their nanoscale range by coating in the reaction medium. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, WeinheimItem Noble copper-silver-gold trimetallic nanobowls: An efficient catalyst(Academic Press, 2019) Haldar, Krishna Kanta; Tanwar, S; Biswas, R; Sen, T; Lahtinen, J.We demonstrated the design of tiny bowls of copper-silver-gold (Cu-Ag-Au) alloy type noble trimetallic nanocrystals with a unique shape. All the structural characterizations confirm the presence of copper (Cu), silver (Ag), and gold (Au) in the trimetallic nanobowls. Finally, we examined the catalytic efficiency of trimetallic Cu-Ag-Au nanobowls for reduction of 4-nitrophenol to 4-aminophenol and found that these nanobowls were 14, 23 and 43-fold more active than each of the constituent metals, Au, Cu and Ag, respectively. © 2019 Elsevier Inc.Item Single-molecule force-unfolding of titin I27 reveals a correlation between the size of the surrounding anions and its mechanical stability(Royal Societty of chemistry, 2018) Muddassir, Mohd; Manna, Bharat; Singh, Priyanka; Singh, Surjeet; Kumar,Rajesh; Ghosh, Amit; Sharma, DeepakEach cellular protein is surrounded by a biochemical milieu that affects its stability and the associated function. The role of this surrounding milieu in the proteins’ mechanical stability remains largely unexplored. Herein, we report an as yet unknown correlation between the size of the surrounding anions and the mechanical stability of a protein. Using single-molecule force spectroscopy of the 27th domain (I27) of human cardiac muscle protein titin, we show that the average unfolding force of the protein decreases with increase in the ionic radii of the surrounding anions in the order Cl− > Br− > NO3− > I− > SO42− ≈ ClO4−, indicating an inverse correlation between anion size and the mechanical stability of I27. The destabilizing effect was attributed to the combined effect of increase in the unfolding rate constant and unfolding distance upon incubation with the anion. These findings reveal that anion size can significantly affect the mechanical resistance of proteins and thus could be a convenient and promising tool for regulating the mechanical stability of proteins.Item In situ reductive regeneration of zerovalent iron nanoparticles immobilized on cellulose for atom efficient Cr(vi) adsorption(Royal Society of Chemistry, 2015) Sharma, Archana Kumari; Kumar, Rabindra; Mittal, Sunil; Hussain, Shamima; Arora, Meenu; Sharma, R.C.; Babu, J. NagendraZerovalent iron nanoparticles (nZVI) (11.8 - 0.2% w/w) immobilized on microcrystalline cellulose (C-nZVI) were synthesized and studied for Cr(vi) sorption. The material showed good atom economy for Cr(vi) adsorption (562.8 mg g-1 of nZVI). Oxidation of cellulose to cellulose dialdehyde leads to in situ regeneration of nZVI which is responsible for the atom efficient Cr(vi) sorption by C-nZVI.Item Sorptive removal of arsenite [As(III)] and arsenate [As(V)] by fuller's earth immobilized nanoscale zero-valent iron nanoparticles (F-nZVI): Effect of Fe 0 loading on adsorption activity(Elsevier Ltd, 2016) Yadav R.; Sharma A.K.; Babu J.N.Fuller's earth immobilized nanoscale zerovalent iron (F-nZVI 1-8) were synthesized by borohydride reduction method. The iron loading of fuller's earth immobilized nZVI was varied from 5 to 50% (w/w) in these F-nZVI 1-8. The F-nZVI 1-8 were characterized by FE-SEM-EDX, FTIR, BET, XRD and TGA. The FE-SEM analysis showed an increase in agglomeration of nZVI on the immobilized material with increase in the loading of Fe 0 . F-nZVI 1-8 were studied for adsorptive removal of As(III) and As(V) from aqueous solution, with an emphasis on the effect of Fe 0 loading of adsorbent on arsenic remediation. Iron loading has a significant role in adsorption of As(III) and As(V) on F-nZVI, with increase in adsorption with optimum iron loading of 20% (w/w) on fuller's earth (F-nZVI-4). However, increase in loading above 20%, resulted in no significant increase in As(III) and As(V) adsorption. The adsorption results fitted well with Langmuir and Freundlich isotherm models and the maximum adsorption capacity of F-nZVI-4 for As(III) and As(V) were observed to be 50.08 and 91.42 mg/g, respectively. The adsorption isotherm and kinetic studies indicate a rapid removal of As(III) and As(V) from the aqueous solution in the presence of F-nZVI 1-8, with an substantially high rate of removal for arsenic with F-nZVI-4.