Photoinduced hyperthermia is a cancer therapy technique that induces death to cancerous cells via heat generated by plasmonic nanoparticles. While previous studies have shown that some nanoparticles can be effective at killing cancer cells under certain conditions, there is still a necessity (or the need) to improve its heating efficiency. In this work, we perform a detailed thermoplasmonic study comparing the most effective nanoparticle geometries up to now with a dougnhut-shaped nanoparticle, demonstrating that the latter exhibits an outstanding tuneable photothermal response in realistic illumination conditions, i.e., partially polarized light. Furthermore, we show that nanoparticle heating in microfluidic environments, i.e. nanoparticles suffering arbitrary rotations, strongly depends on the particle orientation with respect to the illumination source, a circumstance often neglected in photothermal applications. We conclude that heating of nanodoughnuts depends weakly on orientation and light depolarization, being therefore ideal candidates for photothermal therapy applications. Finally, we present a nanodoughnut designing guide, covering a wide range of toroid designs, which can help on its experimental implementation.

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Optical biosensing is currently an intensively active research area, with an increasing demand of highly selective, sensitivity-enhanced and low-cost devices where different plasmonic approaches have been developed. In this work we propose a tunable optimized grating-based gold metasurface that can act both as a high sensitivity sensor device (up to 1500 nm/RIU) and as an unidirectional plasmon source. The theory behind surface plasmon polariton generation is recalled to thoroughly understand the influence that every parameter of the grating source has on the performance of the proposed device. The results and conclusions discussed here offer a key step toward the design of biosensors based on excitation of surface plasmons polaritons by grating-based structures or in the process of creating new nanophotonic circuit devices.