Noble metal nanoparticles (NPs) represent nanoscale, optically addressable heat sources whose temperature gradients give rise to thermophoretic forces that can act back on the NPs. Herein we investigate 20 nm Ag NPs bound via molecular tethers to a 20 nm thin Au film as nanoplasmonic actuators that generate a local temperature gradient and simultaneously act as optical sensors of forces that induce their displacement from their equilibrium position. Forces of sufficient magnitude to affect the NP–film distance modulate the interferometric scattering (iSCAT) signal of the individual NPs and become detectable due to the distance-dependent damping of the NP scattering in the vicinity of the metal film. With total incident power densities within a range between 1.40 and 4.80 kW cm^–2, the experiments reveal a continuous decay in the NP iSCAT signal, consistent with a decrease in the NP–film separation due to an attractive thermophoretic force.

中文翻译：

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通过具有干涉散射读数的纳米等离子体致动器传感热泳力


贵金属纳米颗粒 （NP） 代表纳米级、光学可寻址的热源，其温度梯度产生可以反作用在 NP 上的热泳力。在本文中，我们研究了通过分子系绳结合到 20 nm 薄 Au 薄膜上的 20 nm Ag NP 作为纳米等离子体致动器，产生局部温度梯度，同时充当力的光学传感器，使其从平衡位置发生位移。影响 NP 薄膜距离的足够大小的力会调制单个 NP 的干涉散射 （iSCAT） 信号，并且由于 NP 散射在金属薄膜附近的距离依赖性阻尼而变得可检测到。当总入射功率密度在 1.40 和 4.80 kW cm^–2 之间时，实验揭示了 NP iSCAT 信号的持续衰减，这与由于有吸引力的热泳力而导致的 NP 薄膜分离的减少一致。