Jiang Quanbo, Rogez Benoît, Claude Jean-Benoît, Baffou Guillaume, Wenger Jérôme
Aix Marseille Université, CNRS, Centrale Marseille, Institut Fresnel, 13013 Marseille, France.
Nano Lett. 2020 Dec 9;20(12):8811-8817. doi: 10.1021/acs.nanolett.0c03638. Epub 2020 Nov 25.
Plasmonic nanotweezers use intense electric field gradients to generate optical forces able to trap nano-objects in liquids. However, part of the incident light is absorbed into the metal, and a supplementary thermophoretic force acting on the nano-object arises from the resulting temperature gradient. Plasmonic nanotweezers thus face the challenge of disentangling the intricate contributions of the optical and thermophoretic forces. Here, we show that commonly added surfactants can unexpectedly impact the trap performance by acting on the thermophilic or thermophobic response of the nano-object. Using different surfactants in double nanohole plasmonic trapping experiments, we measure and compare the contributions of the thermophoretic and the optical forces, evidencing a trap stiffness 20× higher using sodium dodecyl sulfate (SDS) as compared to Triton X-100. This work uncovers an important mechanism in plasmonic nanotweezers and provides guidelines to control and optimize the trap performance for different plasmonic designs.
表面等离子体激元纳米镊子利用强电场梯度来产生能够在液体中捕获纳米物体的光力。然而，部分入射光会被金属吸收，由此产生的温度梯度会在纳米物体上产生额外的热泳力。因此，表面等离子体激元纳米镊子面临着区分光力和热泳力复杂贡献的挑战。在此，我们表明，通常添加的表面活性剂可通过作用于纳米物体的嗜热或畏热反应，意外地影响捕获性能。在双纳米孔表面等离子体激元捕获实验中使用不同的表面活性剂，我们测量并比较了热泳力和光力的贡献，结果表明，与Triton X-100相比，使用十二烷基硫酸钠（SDS）时捕获刚度高20倍。这项工作揭示了表面等离子体激元纳米镊子中的一个重要机制，并为控制和优化不同表面等离子体激元设计的捕获性能提供了指导。
