Brasiliense Vitor, Berto Pascal, Aubertin Pierre, Maisonhaute Emmanuel, Combellas Catherine, Tessier Gilles, Courty Alexa, Kanoufi Frédéric
Sorbonne Paris Cité, Université Paris Diderot, Interfaces, Traitements, Organisation et Dynamique des Systèmes, CNRS-UMR 7086, 15 rue J. A. Baif , F-75013 Paris , France.
Sorbonne Paris Cité, Université Paris Descartes, Neurophotonics Laboratory, CNRS-UMR 8250, 45 rue des Saints-Pères , F-75006 Paris , France.
ACS Nano. 2018 Nov 27;12(11):10833-10842. doi: 10.1021/acsnano.8b03140. Epub 2018 Oct 22.
When narrowly distributed silver nanoparticles (NPs) are functionalized by dodecanethiol, they acquire the ability to self-organize in organic solvents into 3D supercrystals (SCs). The NP surface chemistry is shown to introduce a light-driven thermomigration effect, thermophoresis. Using a laser beam to heat the NPs and generate steep thermal gradients, the migration effect is triggered dynamically, leading to tailored structures with high density of plasmonic hot spots. This work describes how to manipulate the hot spots and monitor the effect by holography, thus providing a complete characterization of the migration process on a single object basis. Extensive single object tracking strategies are employed to measure the SCs trajectories, evaluate their size, drift velocity magnitude and direction, allowing the identification of the physical chemical origins of the migration. The phenomenon is shown to happen as a result of the combination of thermophoresis (at short length scales) and convection (long-range), and does not require a metallic substrate. This constitutes a fully optical method to dynamically generate plasmonic platforms in situ and on demand, without requiring substrate nanostructuration and with minimal interference on the chemistry of the system. The importance of the proof-of-concept herein described stems from the numerous potential applications, spanning over a variety of fields such as microfluidics and biosensing.
当窄分布的银纳米颗粒（NPs）用十二烷硫醇功能化时，它们获得了在有机溶剂中自组装成三维超晶体（SCs）的能力。研究表明，NP表面化学引入了光驱动的热迁移效应，即热泳现象。利用激光束加热NP并产生陡峭的热梯度，动态触发迁移效应，从而形成具有高密度等离子体热点的定制结构。这项工作描述了如何通过全息术操纵热点并监测其效果，从而在单个物体的基础上对迁移过程进行完整表征。采用广泛的单物体跟踪策略来测量SCs的轨迹，评估其大小、漂移速度的大小和方向，从而确定迁移的物理化学起源。结果表明，这种现象是热泳（在短长度尺度上）和对流（长距离）共同作用的结果，并且不需要金属基底。这构成了一种完全光学的方法，可原位按需动态生成等离子体平台，无需基底纳米结构化，且对系统化学的干扰最小。本文所述概念验证的重要性源于其在微流体和生物传感等多个领域的众多潜在应用。
