Bimodal size distribution of gold nanoparticles in aqueous solution during pulsed laser irradiation
- PDF / 835,602 Bytes
- 5 Pages / 595 x 842 pts (A4) Page_size
- 60 Downloads / 195 Views
MM2.7.1
Bimodal size distribution of gold nanoparticles in aqueous solution during pulsed laser irradiation Susumu Inasawa, Masakazu Sugiyama1 and Yukio Yamaguchi Department of Chemical System Engineering, School of Engineering, The University of Tokyo Hongo 7-3-1, Bunkyo-ku, Tokyo, 113-8656, Japan Department of Electronic Engineering, School of Engineering, The University of Tokyo
1
Hongo 7-3-1, Bunkyo-ku, Tokyo, 113-8656, Japan
ABSTRACT Size distribution of gold nanoparticles in aqueous solution during pulsed laser irradiation (Nd:YAG laser, wavelength of 355 nm, pulse width 30 ps) is observed by transmission electron microscope (TEM). Interestingly, we observed that a single peak distribution of gold nanoparticles sizes (initially centered around 25 nm) is gradually turned into a two-peaks one upon laser radiation. Initial particles reduced their sizes and smaller particles were formed, resulting in the bimodal size distribution. In these bimodal size distributions, two peaks are observed, one is at 6 nm, and another is at 24 nm.
INTRODUCTION It is well known that nano-sized particles show unique properties because of their high ratio of surface area over volume, quantum size effect and so on. Especially, nano-sized gold nanoparticles shows distinct absorption due to the surface plasmon resonance in UV-Vis region, and much attention has been paid for the study on the interaction between light and nanoparticles such as optical properties of gold nanoparticles [1,2]. Ultra-fast energy relaxation dynamics in gold nanoparticles has been also investigated by using femtosecond laser irradiation [3-6], because those relaxation dynamics can be monitored by the change of absorption spectra of them. Using such ultra-fast laser, the production of gold nanoparticles in some matrix has also been studied [7]. In addition to these fundamental studies, laser induced size reduction of gold, silver nanoparticles were reported [8,9,10,11]. Two kinetic processes are proposed for the phenomena, one is the vaporization of particles induced by the photothermal energy [7] and another is coulomb explosion of particles caused by the electron ejection out of particles [8]. Both could explain the size reduction phenomenon itself, but neither of them would give us sufficient explanation for the formation kinetics of smaller particles after the size reduction. Furthermore, the question about which kinetics is appropriate for laser induced size reduction phenomena still
MM2.7.2
remains to be solved. In the present study, we investigate the formation process of small particles after the size reduction phenomena and how particles reduce their sizes during pulsed laser irradiation. We observed that initial mono-modal size distribution of gold nanoparticles turned into bimodal one with two peaks, one is at 6 nm and another is at 24 nm.
EXPERIMENTAL DETAILS We used 3rd harmonic Nd:YAG laser (EKSPLA, PL2143B) (wavelength of 355 nm, pulse width 30 ps) in our experiment. Pulsed laser light were irradiated to the quartz cuvette (optical path 1
Data Loading...
