School of Materials Science & Nanotechnology,Jadavpur University
Metal and Metal Oxide Particles in Nanometer Length Scale
Tarasankar Pal
Department of Chemistry, Indian Institute of Technology, Kharagpur-721302, India
Nanostructured materials possess at least one length scale on the order of a billionth of a meter. They have sparked steadily growing interest not only for their fundamental scientific significance but also for the many technological applications that derive from their peculiar and fascinating properties, superior to the corresponding bulk counterparts by tailoring the magnetic, optical and electronic stuctures. Synthesis of well-defined monodispersed nanoparticles with controllable size, shape and structure at the nanolevel is the present goal for innumerable applications. Herein, we have explored a green chemistry approach, photoactivation technique and surfactant mediated wet chemical method for syntheses of varied metallic and oxide nanostructured materials.
A facile approach has been furnished to fabricate mono- & bi-metallic nanoshell-coated funtionalized polystyrene beads, based on the three-dimensional entrapment of the metallic nanoparticles by electrostatic attraction between polystyrene beads and the oppositely charged complex precursor ions, followed by wet chemical reduction. In a facile photochemical reduction route in situ deposition of exclusively α-MnO2 nanorods onto the surface of polystyrene beads has been achieved through immobilization of metal precursor ions exploiting the electrostatic field force of the charged resin beads, under visible light illumination in alkaline condition.1 Again, under surfactant mediated appraoach shape-controlled (nanospheres to nanorods) synthesis of exclusively single crystalline β-MnO2 nanoparticles have been achieved through air oxidation of MnCl2 in variable micellar templates under alkaline condition at room temperature. Finally, MnO2 organosol have been synthesized for the first time in toluene employing a two-phase (water-toluene) extraction of MnO4- ions followed by its reduction with tetrabutyl ammonium borohydride in the presence a phase transfer reagent, tetraoctylammonium bromide. Leaving aside the characterization of the as-synthesized nanaomaterials by different physical methods (XRD, XPS, FTIR, SEM, TEM, EDX etc.) successful photo-
induced hydrolysis of nitriles & ‘C-C’ bond formation in phenolic precursor compunds, selective reduction of aromatic nitro compounds 2,3 for industrially important amino aromatics have been reported. A two-step procedure has also been developed for the synthesis of ultra thin bimetallic nanoshells again on functionalized polystyrene beads through immobilization of ions via ion-exchange and subsequent reduction. Following this procedure we have synthesized [R(Au0)(Pd0)]+Cl-, [R(Ag0)(Cu0)]-H+ and [R(Pd0)(Pt0)]+Cl- particles.4 The silver-copper bimetallic shell coated new composite materials were employed as an efficient solid substrate for surface enhanced Raman scattering (SERS) application for detection of important biomolecules down to the single molecular level.5 We have also demonstrated the interaction between the nanoscale silver particles with various DNA bases (adenine, guanine, cytosine and thymine), which are used as a molecular linker because of their biological significance and the extent of silver-nitrogen interaction was quantified through normalized SERS signal intensity.6
References:
1 Jana S, Praharaj S, Panigrahi S, Basu S, Pande S, Chang C-H and Pal T Org. Lett. 2007, 9, 2191.
2 Panigrahi S, Basu S, Praharaj S, Pande S, Jana S, Pal A, Ghosh S K and Pal T J. Phys. Chem. C 2007, 111 4596.
3 Jana S, Pande S, Panigrahi S, Praharaj S, Basu S, Pal A and Pal T Langmuir 2006, 22 709.
4 Praharaj S, Nath S, Panigrahi S, Ghosh S K, Basu S, Pande S, Jana S and Pal T Inorg. Chem. 2006, 45 1439.
5 S. Pande, A. Pal, S. Panigrahi, S. Praharaj, S. Basu, S. Jana, T. Tsukuda and T. Pal, J. Phys. Chem. C 2007, 111, 10806
6 Basu S, Panigrahi S, Praharaj S, Ghosh S K, Pande S, Jana S and Pal T New J. Chem. 2006, 30 1333.
Corresponding author: tpal@chem.iitkgp.ernet.in / tarasankar.pal@gmail.com
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