Soft chemical approaches to inorganic nanostructures

Abstract

Chemical approaches have emerged as the preferred means to synthesize nano-structures of various inorganic materials due to superior control over size, shape, and surfacefunctionality. This article provides an overview of the contributions made in the authors’ lab-oratory toward the synthesis of nanocrystals, nanowires, nanotubes, nanowalls, and othernanostructures of several inorganic materials. Thus, thiolized monodisperse metal nano-crystals have been obtained by a ligand exchange process and the stability of their 2D as-semblies studied. Nanocrystals of pure CoO and ReO3have been synthesized, for the firsttime, employing a one-pot solvothermal technique. The solvothermal method has also beenused to obtain organic soluble nanocrystals of semiconducting materials such as CdS, CdSe,and GaN. Inorganic nanowires and nanotubes have been prepared by several soft chemicalroutes, including surfactant-assisted synthesis and hydrogel templating. A simple reactionbetween elemental Se and Te with NaBH4in water has been utilized to obtain nanowires ofSe and Te. We also describe the nebulized spray pyrolysis (NSP) technique to synthesize car-bon nanotubes and nanowires of metals and III-V nitride semiconductors with improvedyields. An important new technique for preparing nanocrystalline films of materials is by thereaction of the metal precursors in the organic layer at the interface of two immiscible liq-uids, with appropriate reagents. Nanocrystalline films of metals, alloys, and semiconductorsand ultra-thin single-crystalline films of metal chalcogenides and oxides have been obtainedby this technique. Apart from these, we discuss single precursor routes to iron sulfide, GeSe2,and III-V nitride nanostructures as well as the first synthesis of GaS and GaSe nanowalls andnanotubes obtained through exfoliation by laser irradiation and thermal treatment.