The Optical Properties and Particle Size Influence Mechanism of Au Nanoparticles processed by the Diverse Filtration and Centrifugalization Methods
Jia-Ren Lee1, Bo-Wen Shiau1*, Wei-Cheng Ding1
1Department of Physics, National Kaohsiung Normal University, Kaohsiung, Taiwan
* presenting author:蕭博文,
This paper studies the optical properties and particle size influence mechanism of prepared Au nanoparticles by centrifugalization and filtration technique. The Au nanoparticles are produced by the sonoelectrochemical method: the ultrasonication and constant current electrolysis are implemented simultaneously. The Au nanoparticle solution is separated into precipitated solution by specific rotational speed; then the precipitated solution is mixed with the deionized water and further centrifuged by the same speed and procedure for three times. The CTAB content is gradually reduced by each centrifugation. Then the structure of Au nanoparticles in the solution is changed and induced the different spectral features. The absorption spectra of the solutions stood for dissimilar period are measured after each centrifugation. When the standing time is lengthened, the absorption spectra of Au nanoparticle after the first and second centrifugation are almost invariant. Nevertheless, the absorption intensity at 535 nm is gradually decreased when the standing time of solution after the third centrifugation is increased; meanwhile, the gradual red-shift and the enhanced intensity of absorption peak about 650 nm are observed. The absent CTAB induced recombination of Au nanoparticles lead to the growth and decline of spectral features. After 4 hour standing time, the nano-Au and other shielding particles gradually gather into the large grains and fall to the solution bottom hence the absorbance of whole spectrum is reduced. Two types of filtration methods are used in our experiments: the solution with added filter paper is filtered by stir or ultrasonic concussion respectively. The more reduced absorption intensity and the more blue-shifted peak of filtered solution processed by ultrasonic vibration are observed than that by stir in the same filtration time. The results demonstrate that the filtration with ultrasonication can effectively filter a lot of larger particles and extract smaller Au nanoparticles in the results.

Keywords: Au nanoprticle, centrifugalization method, filtration, sonoelectrochemical method