Hosokawa Chie, Yoshikawa Hiroyuki, Masuhara Hiroshi
Department of Applied Physics and Handai Frontier Research Center, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
Phys Rev E Stat Nonlin Soft Matter Phys. 2005 Aug;72(2 Pt 1):021408. doi: 10.1103/PhysRevE.72.021408. Epub 2005 Aug 29.
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.
我们通过荧光相关光谱法报告了对限制在光学捕获势中的纳米颗粒团簇生长的原位观察。当由高度聚焦的激光束引起的光学捕获力作用于纳米颗粒悬浮液时，纳米颗粒的数量增加，并且可以在焦点处形成聚集体。研究了荧光自相关曲线的衰减时间与激光束照射时间和激光功率的函数关系。在光学组装的初始阶段，衰减时间随激光束照射时间增加。另一方面，在后期，观察到衰减时间减少。通过使用弱光学捕获和强光学捕获下的两种布朗运动模型成功解释了这种行为。结果表明，纳米颗粒的捕获和聚集同时进行，限制在焦点处的团簇会自发形成更大的聚集体。
