Flow-Induced Transport via Optical Heating of a Single Gold Nanoparticle
Flow-Induced Transport via Optical Heating of a Single Gold Nanoparticle
复制标题
DOI：
10.1021/acs.jpcc.8b11575
复制
发表时间：
2019-02-21
影响因子：
3.7
通讯作者：
Hashimoto, Shuichi
中科院分区：
文献类型：
--
作者：
Chikazawa, Jun-ichi;Uwada, Takayuki;Hashimoto, Shuichi
光热捕获在诸如选择、引导和定位亚微米物体的操作中越来越受欢迎，因为几mW的激光功率远低于光学捕获所需的功率。光热捕获利用热梯度诱导的泳动，但驱动力的基本物理尚未完全理解。在这项研究中，我们进行了光热捕获的500 nm直径的胶体二氧化硅通过连续激光照射的一个单一的金纳米粒子从底部在一个封闭的腔室。在光照下，示踪剂颗粒被吸引到金纳米颗粒上并被捕获。值得注意的是，迁移颗粒的方向总是热的金纳米颗粒，而不管放置在腔室的两个相对侧、上基板的底表面（天花板）上或下基板的顶表面（地板）上的金纳米颗粒的配置如何。之前基于从底部到顶部并在室内循环的热对流的解释仅适用于地板配置，无法解释我们对天花板的观察。相反，温度引起的马兰戈尼效应在水/过热水界面可能发挥作用。该研究促进了对光热捕获驱动机制的更好理解。此外，作为单颗粒平台的应用，我们展示了光热相分离诱导的温敏聚合物的微滴形成和非温敏聚合物在纳米颗粒上的涂层。
Optothermal trapping has gained increasing popularity in manipulation such as selecting, guiding, and positioning submicron objects because of a few mW laser power much lower than that required for optical trapping. Optothermal trapping uses thermal-gradient-induced phoretic motions, but the underlying physics of driving force has not been fully understood. In this study, we performed optothermal trapping of 500 nm-diameter colloidal silica via a continuous laser illumination of a single gold nanoparticle from the bottom in a closed chamber. Under illumination, the tracer particles were attracted to the gold nanoparticle and trapped. Notably, the direction of migrating particles was always to hot gold nanoparticles regardless of the configuration of gold nanoparticles placed at two opposite sides of the chamber, on the bottom surface of an upper substrate (ceiling) or on the top surface of a lower substrate (floor). The previous interpretation based on thermal convective flow from the bottom to the top and circulating inside the chamber was only applicable to floor configuration and failed to explain our observation for the ceiling. Instead, temperature-induced Marangoni effect at the water/superheated water interface is likely to play a role. This study promoted a better understanding of the driving mechanism in optothermal trapping. Moreover, as an application of the single-particle platform, we showed the photothermal phase separation-induced microdroplet formation of thermoresponsive polymers and the coating of non-thermoresponsive polymers on nanoparticles.