Cluster formation of nanoparticles in an optical trap studied by fluorescence correlation spectroscopy

Chie Hosokawa*, Hiroyuki Yoshikawa, Hiroshi Masuhara

*Corresponding author for this work

Research output: Contribution to journalArticle

55 Scopus citations

Abstract

We report in situ observation of cluster growth of nanoparticles confined in an optical trapping potential by means of fluorescence correlation spectroscopy. When an optical trapping force caused by a highly focused laser beam acts on nanoparticle suspensions, the number of nanoparticles increases and an assembly can be formed at the focal spot. The decay times of fluorescence autocorrelation curves were investigated as a function of the irradiation time of the laser beam and the laser power. In the initial stage of the optical assembling, the decay time increases with the irradiation time of the laser beam. On the other hand, in the later stage, a decrease of the decay time was observed. This behavior is explained successfully by using two models of Brownian motion under weak and strong optical trapping. It was revealed that trapping and clustering of nanoparticles proceed simultaneously and clusters confined in the focal spot make larger aggregates spontaneously.

Original languageEnglish
Article number021408
JournalPhysical Review E - Statistical, Nonlinear, and Soft Matter Physics
Volume72
Issue number2
DOIs
StatePublished - 1 Aug 2005

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