Analytical Sciences

Abstract − Analytical Sciences, 22(5), 781 (2006).

Quantitative Detection and Fixation of Single and Multiple Gold Nanoparticles on a Microfluidic Chip by Thermal Lens Microscope
Kazuma MAWATARI,* Manabu TOKESHI,** and Takehiko KITAMORI*,**,***
*Microchemistry Group, Kanagawa Academy of Science and Technology (KAST), KSP East 307, 3-2-1 Sakado, Takatsu, Kawasaki, Kanagawa 213-0012, Japan
**Institute of Microchemical Technology (IMT), KSP East 207, 3-2-1 Sakado, Takatsu, Kawasaki, Kanagawa 213-0012, Japan
***Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan
A detection and fixation method of single and multiple gold nanoparticles on the wall of a microfluidic channel is demonstrated. A thermal lens microscope (TLM) with continuous-wave excitation (wavelength, 532 nm) and probe (wavelength, 670 nm) laser beams was used to realize the sensitive detection of heat generated by light absorption of individual gold nanoparticles (50 nm in diameter); fixation of the individual nanoparticles was realized simultaneously. The fixation mechanism was investigated and attributed to an absorption-based optical force. In addition to single nanoparticle detection, multiple-nanoparticle detection and fixation was demonstrated. An acceleration of fixation was observed when the number of fixed particles was increased. TLM is expected to be a powerful tool for both the quantitative detection and precise fixation of individual nanoparticles.