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Nanoparticles and their ordered arrays have many important applications in fields such as electronic, optical, memory storage devices and sensors. Herein, a simple method was used for fabricating three-dimensional ordered gold nanoparticle arrays with template technique. Gold films were deposited onto anodic aluminum oxide by using electron beam evaporation. After thermal annealing, interestingly, order arrays of gold nanoparticles were obtained by a thermodynamically driven self-assembled process. The spectrum taken by UV-Vis spectrophotometer demonstrates clear surface plasmon resonance at around 500 nm, which appears blue-shift compared with usual gold nanoparticles.

We reported a facile synthesis route for size controlled preparation of gold nanoparticles (Au NPs) by controlling concentration of the reducing agent and temperature. Nearly monodisperse Au NPs with mean diameters of 2-6 nm are acquired via the reduction of HAuCl4by NaBH4in the presence of tri-n-octyl amine and dodecanethiol in solvent of toluene. Results indicate that concentration of the reducing agent and temperature are key factors to tune the particle size and uniformity in the synthesis of Au NPs. The as-synthesized Au NPs show size dependent surface plasmonic properties between 510 and 525 nm, while Au NPs with size smaller than 3 nm do not clearly show the property.

The Au/SiO2nanocomposite was produced using surface active agent P123, and its optical absorption spectra was measured by spectrophotometer. It was found that the intensity of absorption peak was strengthened and underwent a red-shift as the neutralization reaction time extended. The variation of optical extinction property of one gold particle (GP) with different size had been investigated by Mie theory. It was found that the extinction property of the single spherical GP possessed an obvious size effect. The extinction property of Au/SiO2nanocomposite had been analyzed by Maxwell-Garnett (MG) theory. It showed that the extinction peak underwent a red-shift and the extinction intensity was strengthened when the size of gold nanoparticles (GNs) increased. The theoretical and the experimental results show that the extinction property of Au/SiO2nanocomposite changes because the scattering effect of GNs are strengthened when their sizes increased by controlling the neutralization reaction time.