Synthesis and characterization of nanorods, nanowires and nanocomposites

Abstract

The nanocomposites consisting of CdS nanoparticles and PVK have been prepared through chemical hybridization. PVK was initially sulfonated in order to make it chemically compatible with the inorganic component in a hybrid system. The sulfonation occurred on the carbazole moiety in PVK and the sulfonation degree could be varied. The electronic structure of sulfonated PVK incurs little changes, but photoluminescence efficiency decrease significantly after sulfonation. The CdS-PVK nanocomposites have been synthesized through the loading of cadmium ions into the sulfonated PVK and subsequent sulfidation of cadmium ions. The truly two-component nanocomposites consist of PVK and CdS nanoparticles with diameters in the range of ~3-20 nm. The physical properties of the nanocomposites have been characterized. The spectral response of photocurrent measurement has demonstrated significant enhancement in the photoconductivity of the nanocomposites film. The photoinduced charge generation and charge separation in the nanocomposites, which could be correlated to the photoconductivity, has been studied by steady-state and time-resolved photoluminescence as well as photoconductivity measurements.

The oriented PbS crystalline nanorods in polymer film have also been prepared and characterized. The functionalized surfactant Pb(AOT)₂ was used as the precursor. Possible growth mechanism of the rod-shaped PbS nanocrystals have been briefly discussed.

A simple method has been found for preparing isolated monoclinic Cu₂S nanowires with good alignment on copper substrates. The diameters of these nanowires can be varied by varying the growth conditions such as the reagent composition and surrounding temperatures. The growth behavior of the Cu₂S nanowires has been investigated and the growth direction has been determined to be along the c-axis of the monoclinic Cu₂S. A primary growth mechanism of the nanowires was proposed. The optical, electrical, and thermal properties, as well as the temperature and pressure-induced phase transition of the nanowires have been studied. The conversion from the monoclinic Cu₂S nanowires to copper oxide and metallic copper wires by thermal oxidation and hydrogen plasma reduction has also been investigated.

Date of Award	2001
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology