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Author: search.filters.author.Basu, MrinmoyeeSubject: search.filters.subject.Redox reactions

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    Redox Transmetalation of Prickly Nickel Nanowires for Morphology Controlled Hierarchical Synthesis of Nickel/Gold Nanostructures for Enhanced Catalytic Activity and SERS Responsive Functional Material
    (ACS, 2010-12-30) Basu, Mrinmoyee
    A nonpolar surfactant assisted mild wet chemistry approach has been presented for controlled fabrication of ferromagnetic ultralong (several micrometers in length) prickly nickel nanowires in gram scale with the assistance of hydrazine hydrate as the reducing agent and nickel chloride as the metal ion precursor. Nanowire structures analogous to the natural plant Euphorbia milii resulted due to the magnetic dipole driven self-assembly, and their alignment was oriented desirably with an external magnetic field. Systematic microscopic characterizations identified the nanowire to be pure fcc-Ni (i.e., face-centered cubic Ni) without any signature of contamination, though X-ray photoelectron spectroscopy (XPS) and magnetization measurements refer to the existence of an ultrathin nickel oxide (NiO) layer over the nanostructures. The as-synthesized nanowires were used as a single-source precursor for the evolution of nanometric black NiO when calcined. Again, the Ni nanowires act as a sacrificial template that addresses deposition of metallic gold over the nanowire with variable structural hierarchy through their quantitative oxidative dissolution. Then, the composite material serves as a heterogeneous catalyst for reduction of 4-nitrophenol, and a probable reaction mechanism has been suggested. Additionally, the materials were proved to furnish a full-proof enhanced field effect for prolific surface-enhanced Raman scattering (SERS) activity. In a nutshell, the strategy provides a new horizon to design need-based functional material with much practical implication.
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    Methylene Blue–Cu2O Reaction Made Easy in Acidic Medium
    (ACS, 2012) Basu, Mrinmoyee
    Truncated Cu2O cubes with well-defined morphology have been successfully synthesized using a stable Cu(II)–EDTA precursor and glucose as the reducing agent in alkaline conditions under 5 min of microwave irradiation. The truncated cubic Cu2O particles as a solid powder were characterized by different physical methods. Curiously enough, upon the addition of Cu2O particles, the blue-colored methylene blue (MB) in aqueous acidic (pH ≈ 1.0) solution successively bleaches to colorless leuco-MB (LMB). The redox reaction generates a colorless solution which easily reverts back to blue in air. The reaction has been quantitatively monitored by UV–vis spectrophotometry. The reversible color change, i.e., oscillation between a blue MB solution and colorless LMB solution happens to be a periodic phenomenon for more than 50 cycles and is reproducibly demonstrated as a simple “clock reaction”. Acidic (pH ≈ 3.0) conditions favor zeroth-order kinetics for the underlying redox phenomena. Dilute H2SO4 has been proven to be the best choice to provide a passive reaction medium, and the undisturbed reaction mixture showed oscillatory behavior even after one month.