Synthesis of silicon nanoparticles: Size, surface, and functionalization

Chapter 1 gives an overview of nanostructures evaluation. The characteristics of nanomaterials, especially the electronic, optical and magnetic properties, significantly differ from those of bulk materials. When nanoparticles (solid particles in the 1--1000 nm range) exhibit a size quantization effect in at least one dimension, the particles are also called quantum dot (QD). Nanostructures, or nanoscale materials, are prospective building blocks for the design of modern materials and miniaturization of current devices. It is expected that the semiconductor nanocrystals, will become very important to biology and biochemistry because of their attractive luminescent properties: broad excitation - narrow emission photophysics, size-tunable emission, longer fluorescence lifetime, and negligible photobleaching.; Silicon hasn't been playing an important role in optoelectronics in the past until efficient light emission from the bulk material was found 10 years ago. In our group, a novel reduction synthesis of Si nanoparticles with a chemically accessible surface at room temperature and ambient pressure has been reported. However, these nanoparticles have unsatisfactory stability and eventually decompose.; In Chapter 2, we reported a silanization method to stabilize silicon nanoparticles (NPs). Energy-selected emission is observed, consistent with the distribution of sizes obtained by this route. The NPs are photochemically stable in non-polar organic solvents. No apparent degradation was observed when this colloid was exposed to air/water under ambient conditions for years.; It is found that variation of initial reactant ratios leads to change in resulting particle diameter, as determined by TEM studies. This was reported in Chapter 3, with detailed studies on size-dependent optical effects of the nanoparticles and Quantum yield (QY).; In Chapter 4, the feasibility of using silanization as a general tool to functionalize the surface of silicon nanoparticles (NPs) has been investigated in detail. Alkyl-containing, bromo-containing, or ester-containing Si nanoparticles have been produced and characterized. Changes of termination groups brought various functionalities to the nanoparticles, without loss of the photophysics of the original nanoparticles.; In last chapter, the silanized-Si NPs were suspended both in organic solvent systems and aqueous systems for fluorescence microscopy studies. Bright visible fluorescences of various colors have been observed from size-distributed Si NPs under different excitations.