Recent advance in the synthesis and properties of group IV nanoparticles

There are four individual but related chapters included in this thesis. The first chapter is a project to optimize a novel solution synthesis route for Si nanoclusters (2--5 nm) terminated with different alkyls and characterize its unusual optical properties (visible blue light emission, 330--500 nm) which may be due to the size factor (quantum confinement). This chapter was published in J. Am. Chem. Soc. 1999, 121 (22), 5191--5195. The investigation for the unusual optical properties of silicon nanoparticles is a collaboration with Dr. Howard Lee's group, Lawrence Livermore National, Lab, using ultrafast laser to study the life time of PL (blue and red), quantum efficiency, quantum yield and nonlinear optical properties. This project has been finished and a publication will be sending off recently.;Next generation nanoparticles will be more complex core-shell, surface functionalized materials. The second research project of this thesis is to synthesize the first examples of surface capped and functionalized germanium/silicon core-shell nanoparticles. The Rr (radius of shell/radius of core) value of core-shell nanoparticles is calculated from the reconstructed phase image that is obtained from hologram. The unusual optical properties enhanced by inorganic outer surface, (quantum confinement enhancement) in Ge/Si-R and Ge/SiO2 core/shell nanoparticles is the first examples that have been reported. A paper based on this chapter was submitted to Chem. Mater. and is under review currently.;The third chapter of this thesis is the synthesis and characterization of Sn/R, Sn/Si-R, and Sn/SnO2 core/shell nanoparticles (R = n-C4H9). The Sn/SiO2 nanoparticles is a potential candidate to be used in rechargeable battery or gas sensor. It still maintains the paramagnetic property at 10 0K measured by SQUID from zero to one Tesla. The sizes (95%) range from 7--13 nm (in diameter). The X-ray powder diffraction agrees with literature data of beta tin (JCPDS 4-673). The solid state 119Sn NMR spectrum is consistent with XRD data, providing further support for a tetragonal geometry for the core of Sn/SiO2. This chapter is sent to Chem. Mater, as a full paper, and is under review recently.;The last chapter of this thesis is a study on how the annealing. temperature affects size and therefore the photoluminescence (PL) of alkyl terminated silicon nanoclusters. Many models have been proposed to explain the mechanism of this unusual PL in the visible light region. These models can be categorized into two main groups. One is the quantum confinement model and the other is a surface state related model. In this chapter, some experimental data are provided that supports the quantum confinement model. A paper based on this chapter will be submitted to Chem. Mater.