Dongare Pratiksha D, Zhao Yage, Renard David, Yang Jian, Neumann Oara, Metz Jordin, Yuan Lin, Alabastri Alessandro, Nordlander Peter, Halas Naomi J
ACS Nano. 2021 May 25;15(5):8761-8769. doi: 10.1021/acsnano.1c01046. Epub 2021 Apr 26.
Plasmonic nanoantennas focus light below the diffraction limit, creating strong field enhancements, typically within a nanoscale junction. Placing a nanostructure within the junction can greatly enhance the nanostructure's innate optical absorption, resulting in intense photothermal heating that could ultimately compromise both the nanostructure and the nanoantenna. Here, we demonstrate a three-dimensional "antenna-reactor" geometry that results in large nanoscale thermal gradients, inducing large local temperature increases in the confined nanostructure reactor while minimizing the temperature increase of the surrounding antenna. The nanostructure is supported on an insulating substrate within the antenna gap, while the antenna maintains direct contact with an underlying thermal conductor. Elevated local temperatures are quantified, and high local temperature gradients that thermally reshape only the internal reactor element within each antenna-reactor structure are observed. We also show that high local temperature increases of nominally 200 °C are achievable within antenna-reactors patterned into large extended arrays. This simple strategy can facilitate standoff optical generation of high-temperature hotspots, which may be useful in applications such as small-volume, high-throughput chemical processes, where reaction efficiencies depend exponentially on local temperature.
等离子体纳米天线能将光聚焦到衍射极限以下，在纳米级结内产生强场增强。在结内放置纳米结构可极大增强其固有光吸收，导致强烈的光热加热，这最终可能损害纳米结构和纳米天线。在此，我们展示了一种三维“天线-反应器”几何结构，其会产生大的纳米级热梯度，在受限的纳米结构反应器中引起大幅局部温度升高，同时使周围天线的温度升高最小化。纳米结构支撑在天线间隙内的绝缘基板上，而天线与下方的热导体直接接触。对升高的局部温度进行了量化，并观察到仅热重塑每个天线-反应器结构内的内部反应器元件的高局部温度梯度。我们还表明，在图案化为大型扩展阵列的天线-反应器内可实现高达200°C的局部高温升高。这种简单策略可促进远距离光学产生高温热点，这在诸如小体积、高通量化学过程等应用中可能有用，在这些应用中反应效率与局部温度呈指数关系。
