Browsing by Author "Kumar Singh, Devesh"

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    C2-Symmetric Bissulfoximine-Based Metal Complexes: Synthesis, Characterization and Their Electrocatalytic Activity in Oxygen Reduction Reaction
    (John Wiley and Sons Ltd, 2022) Junaid, Qazi Mohammad; Kumar Singh, Devesh; Ganesan, Vellaichamy; Sabiah, Shahulhameed
    Sulfoximine-based metal complexes have gained much interest in recent years owing to their promising properties in synthetic organic chemistry. These sulfoximines have been recently introduced in the field of organometallics. However, the coordination properties of pincer sulfoximine ligands and their metal complexes have not been reported. Here, a C2-symmetric bissulfoximine-based pincer ligand ((pyridine-2,6-diylbis(methylene))bis(azaneylylidene))bis(diphenyl-?6-sulfanone), namely S-P ligand and its metal [M(SP)2]2+ {M=Fe (SC-1), Co (SC-2), Ni (SC-3), Cu (SC-4)} complexes, were synthesized. The complexes were characterized by different spectroscopic techniques like UV-Vis, IR, NMR, ESI-MS, and single-crystal XRD. Complexes SC-1 and SC-3 exhibited octahedral geometry irrespective of the metal center. The complexes were systematically explored for electrocatalytic oxygen reduction reaction (ORR) by immobilizing them on a glassy carbon electrode using Nafion. These complexes showed selective two-electron catalytic reduction of O2 to H2O2 in which complex SC-2 showed the highest selectivity (?90%) and complex SC-4 showed the highest onset potential (0.75 V). � 2022 Wiley-VCH GmbH.
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    Enhanced Four-Electron Selective Oxygen Reduction Reaction at Carbon-Nanotube-Supported Sulfonic-Acid-Functionalized Copper Phthalocyanine
    (John Wiley and Sons Inc, 2023) Yadav, Mamta; Kumar Singh, Devesh; Kumar Yadav, Dharmendra; Kumar Sonkar, Piyush; Gupta, Rupali; Ganesan, Vellaichamy
    In the present work, the oxygen reduction reaction (ORR) is explored in an acidic medium with two different catalytic supports (multi-walled carbon nanotubes (MWCNTs) and nitrogen-doped multi-walled carbon nanotubes (NMWCNTs)) and two different catalysts (copper phthalocyanine (CuPc) and sulfonic acid functionalized CuPc (CuPc-SO3?)). The composite, NMWCNTs-CuPc-SO3? exhibits high ORR activity (assessed based on the onset potential (0.57 V vs. reversible hydrogen electrode) and Tafel slope) in comparison to the other composites. Rotating ring disc electrode (RRDE) studies demonstrate a highly selective four-electron ORR (less than 2.5 % H2O2 formation) at the NMWCNTs-CuPc-SO3?. The synergistic effect of the catalyst support (NMWCNTs) and sulfonic acid functionalization of the catalyst (in CuPc-SO3?) increase the efficiency and selectivity of the ORR at the NMWCNTs-CuPc-SO3?. The catalyst activity of NMWCNTs-CuPc-SO3? has been compared with many reported materials and found to be better than several catalysts. NMWCNTs-CuPc-SO3? shows high tolerance for methanol and very small deviation in the onset potential (10 mV) between the linear sweep voltammetry responses recorded before and after 3000 cyclic voltammetry cycles, demonstrating exceptional durability. The high durability is attributed to the stabilization of CuPc-SO3? by the additional coordination with nitrogen (Cu-Nx) present on the surface of NMWCNTs. � 2023 Wiley-VCH GmbH.
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    Nafion-multi-walled Carbon Nanotubes Supported Tris(bipyridyl)iron(II) for Nicotine Detection
    (John Wiley and Sons Inc, 2023) Tiwari, Ananya; Yadav, Mamta; Kumar Singh, Devesh; Ganesan, Vellaichamy
    This work reports an electrochemical sensing framework for nicotine determination based on glassy carbon electrode (GC) immobilized with Fe(bpy)32+ (where bpy is 2,2�-bipyridyl) supported by Nafion and multi-walled carbon nanotubes (Nf-MWCNTs). Fe(bpy)32+ immobilized Nf-MWCNTs modified GC (GC/Nf-MWCNTs/Fe(bpy)32+) manifests stable redox peaks, characteristics of Fe(bpy)32+. The GC/Nf-MWCNTs/Fe(bpy)32+ exhibits effective electrochemical oxidation of nicotine, diminishing the overpotential relative to GC/Nf-MWCNTs. The limit of detection is 0.1 ?M (experimentally observed) with two different linear calibration ranges between 0.1 to 600 ?M and 600 to 3000 ?M. Electrocatalytic responses observed at GC/Nf-MWCNTs/Fe(bpy)32+ indicate superior performance for nicotine determination with acceptable selectivity, stability, and reproducibility. Additionally, the nicotine present in real samples such as beedi and tobacco are also analyzed with satisfactory recovery percentages. � 2022 Wiley-VCH GmbH.