Synthesis and characterization of nanomaterials: Nanotubes, nanowires, and nanobelts.

摘要

The goal of this dissertation is to identify the science that can be acquired about nanomaterials using Raman spectroscopy. A systematic study was undertaken using three types of nanomaterials: (i) carbon nanotubes, (ii) ZnO nanowires, and (iii) nanobelts of ZnO and SnO2.; Raman spectroscopy is an indispensable tool in carbon science since it provides unique spectral fingerprint for sp2, sp3 and spx (2 x 3) bonded carbons. I begin with the synthesis of boron doped single walled carbon nanotubes (SWNT) and focus on the effects of the boron incorporation in the nanotube lattice on the phonon structure and thermoelectric power. Since an unzipped carbon nanotube resembles a planar graphene sheet, a detailed comparison of phonon structure is made with boron doped graphite.; Next, I focus on the wide band gap semiconducting oxides like ZnO and SnO2. The former serves as an ideal system for studying the effects of reduced dimensionality on the vibration and electronic properties since bulk ZnO can be coaxed into the nanowire and nanobelt forms. This study fords that Raman spectroscopy can sensitively identify oxygen deficiencies in these nanostructured semiconducting oxides. Further, I present a simple model which estimates at what sample dimensions quantum confinement effects can be expected to be seen in the vibrational or electronic properties. Experimental Raman and photoluminescence data described here, as well as those published recently in the literature, corroborate well with the estimated sample dimensions predicted by the simple model.