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arXiv · 1604.03585

Localization of Temperature Using Plasmonic Hot Spots in Metal Nanostructures: The Nano-Optical Antenna Approach and Fano Effect

Larousse Khosravi Khorashad·Lucas V. Besteiro·Zhiming Wang·Jason Valentine·Alexander O. Govorov
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Abstract

It is challenging to strongly localize temperature in small volumes because heat transfer is a diffusive process. Here we show how to overcome this limitation using electrodynamic hot spots and interference effects in the regime of continuous-wave (CW) excitation. We introduce a set of figures of merit for the localization of temperature and for the efficiency of the plasmonic photo-thermal effect. Our calculations show that the temperature localization in a trimer nanoparticle assembly is a complex function of the geometry and sizes. Large nanoparticles in the trimer play the role of the nano-optical antenna whereas the small nanoparticle in the plasmonic hot spot acts as a nano-heater. Under the peculiar conditions, the temperature increase inside a nanoparticle trimer can be localized in a hot spot region at the small heater nanoparticle and, in this way, a thermal hot spot can be realized. However, the overall power efficiency of temperature generation in this trimer is much smaller than that of a single nanoparticle. We can overcome the latter disadvantage by using a trimer with a nanorod. In the trimer assembly composed of a nanorod and two spherical nanoparticles, we observe a strong plasmonic Fano effect that leads to the concertation of optical energy dissipation in the small heater nanorod. Therefore, the power-absorption efficiency of temperature generation in the nanorod-based assembly greatly increases due to the strong plasmonic Fano effect. The Fano heater incorporating a small nanorod in the hot spot has obviously the best performance compared to both single nanocrystals and a nanoparticle trimer. The principles of heat localization described here can be potentially used for thermal photo-catalysis, energy conversion and bio-related applications.

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Larousse Khosravi Khorashad, Lucas V. Besteiro, Zhiming Wang, Jason Valentine, Alexander O. Govorov. 2016-04-12. Localization of Temperature Using Plasmonic Hot Spots in Metal Nanostructures: The Nano-Optical Antenna Approach and Fano Effect. https://doi.org/10.1021/acs.jpcc.6b03644

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