Department of Chemistry
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Item Metal and Metal Oxide Nanostructure on Resin Support(Wiley, 2011-07-11) Basu, MrinmoyeeItem A Green Chemistry Approach for the Synthesis of Flower-like Ag-Doped MnO2 Nanostructures Probed by Surface-Enhanced Raman Spectroscopy(ACS, 2009) Basu, MrinmoyeeNovel hierarchical flower-like nanostructures of Ag-doped MnO2 have been obtained by facile wet chemical and photochemical routes. UV−visible absorption spectroscopy measurement reveals that doping of Ag nanoparticles in MnO2 nanostructures leads to a red shift of the absorption edge and reduces the optical band gap energy from 2.68 to 2.51 eV while compared with undoped MnO2. Raman study reveals that the band broadens and shifts toward higher wavenumbers as the MnO6 octahedron is contorted by Ag doping and thus the loss of translational symmetry activates otherwise Raman-forbidden oxygen vibrations. Finally, SERS activity upsurges from Ag-doped MnO2 with Rhodamine 6G and 2-aminothiophenol as probe molecules.Item High-Yield Synthesis of 1D Rh Nanostructures from Surfactant Mediated Reductive Pathway and their Shape Transformation(ACS, 2010-09-13) Basu, MrinmoyeePrecise control over the size and shape of nanoparticles from solution-phase synthetic approach is currently a major objective in nanoscience. Metal nanorods and nanowires have attracted much attention because of their outstanding catalytic, magnetic, optical, and electrical properties. We have reported here the microwave (MW) assisted gram quantity synthesis of 1D nanostructures composed of Rh(0) and Rh(I). Thus, the rod-like assembly evolves through Rh(I)−Rh(I) interaction as the building blocker for the 1D nanostructure by using cetyltrimethylammonium bromide (CTAB) as a reducing agent as well as soft template. Reduction of Rh(III) to Rh(0)/Rh(I) occurred on the glass surface as a result of decomposition of CTAB upon MW heating without any other reducing agent. Uniform heating and the presence of CTAB, a face selective adsorption additive, helped the formation of 1D Rh nanostructures. Here, CTAB upon decomposition produced ammonia which in turn acted as a reducing agent ((a) Bal, R.; Tada, M.; Iwasawa, Y. Chem. Commun.2005, 3433. (b) Huang, Y.; Wang, W.; Liang, H.; Xu, H. Cryst. Growth Des.2009, 9, 858), and the undecomposed CTAB stabilized the nanostructure moiety. Hydrothermal condition produced only spherical Rh(0) nanoparticles, and boiling condition prompted anisotropic growth of the Rh(0)/Rh(I) nanoparticles with ill-defined morphology. The presence of impurity such as NH4Cl or CsCl produced distinct 1D nanorods or nanowires in microwave heating condition. Interestingly, the syntheses of different morphology of Rh nanomaterials have been obtained by keeping the Rh(III) ion precursor to CTAB molar ratio unaltered. It has been observed that the pH has a remarkable influence on the alteration of aspect ratio and sharpening of the edges of Rh nanorods. The evolved nanostructures in different stages were characterized ex situ by different physical methods. How and why thermodynamically rather unstable Rh nanorods and nanowires changed their shapes in a chosen redox environment is reported. Interesting shape transformation has also been shown in a selective redox environment for nanorods and nanowires to octahedral and spherical particles, respectively. Isolated intermediates, identified by FESEM and TEM measurements, supported and guarantee the rod-to-octahedral shape transformation. Cyclic voltammetric measurement shows that as-prepared nanorods can be used as a potential candidate for oxygen evolution.Item NEXT Evolution of Hierarchical Hexagonal Stacked Plates of CuS from Liquid−Liquid Interface and its Photocatalytic Application for Oxidative Degradation of Different Dyes under Indoor Lighting(ACS, 2010) Basu, MrinmoyeeBlue solution of copper(II) acetylacetonate complex, [Cu(acac)2] in dichloromethane (DCM) and an aqueous alkaline solution of thioacetamide (TAA) constitute a biphasic system. The system in a screw cap test tube under a modified hydrothermal (MHT) reaction condition produces a greenish black solid at the liquid−liquid interface. It has been characterized that the solid mass is an assembly of hexagonal copper sulfide (CuS) nanoplates representing a hierarchical structure. The as-synthesized CuS nanoplates are well characterized by several physical techniques. An ethanolic dispersion of CuS presents a high band gap energy (2.2 eV) which assists visible light photocatalytic mineralization of different dye molecules. Thus a cleanup measure of dye contaminated water body even under indoor light comes true.Item 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, MrinmoyeeA 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.Item NEXT Nickel Cobaltite Nanostructures with Enhanced Supercapacitance Activity(ACS, 2014) Basu, MrinmoyeeHerein, we report a strategy for controlled synthesis of functional nanomaterials desired for energy conversion and power storage applications. NiCo2O4 nanostructures with square sheets, hexagonal sheets, and spherical form have been synthesized using a solvothermal route by tuning of reaction conditions as well as selection of hydrolyzing agents. The synthesized nanostructures exhibited significant shape dependent electrochemical behavior with improved supercapacitance as well as good electrocatalytic properties toward oxygen evolution reaction. Among all the three morphologies, the square sheets, assembled from nanoparticles ∼5 nm diameter, exhibited higher specific capacitance with good stability. Due to high surface area (∼100 m2/g) and the mesoporous nature of the square sheets, NiCo2O4 reveals better pseudocapacitance.Item Nickel Cobaltite Nanostructures with Enhanced Supercapacitance Activity(ACS, 2014-07-08) Basu, MrinmoyeeHerein, we report a strategy for controlled synthesis of functional nanomaterials desired for energy conversion and power storage applications. NiCo2O4 nanostructures with square sheets, hexagonal sheets, and spherical form have been synthesized using a solvothermal route by tuning of reaction conditions as well as selection of hydrolyzing agents. The synthesized nanostructures exhibited significant shape dependent electrochemical behavior with improved supercapacitance as well as good electrocatalytic properties toward oxygen evolution reaction. Among all the three morphologies, the square sheets, assembled from nanoparticles ∼5 nm diameter, exhibited higher specific capacitance with good stability. Due to high surface area (∼100 m2/g) and the mesoporous nature of the square sheets, NiCo2O4 reveals better pseudocapacitance.