Detecting plasmonic heating via liquid crystals thermometry

Plasmonic nanoparticles (NPs) when pumped sufficiently with resonant radiation have the unique capability to concentrate an incredible amount of heat at the nanoscale, thanks to a phenomenon called localized plasmonic... [ view full abstract ]

Plasmonic nanoparticles (NPs) when pumped sufficiently with resonant radiation have the unique capability to concentrate an incredible amount of heat at the nanoscale, thanks to a phenomenon called localized plasmonic resonance (LPR) [1, 2]. Thermotropic liquid crystals (LCs) are an excellent candidate medium as they are extremely responsive to external perturbations such as electric fields, optical fields and temperature [3, 4]. LCs have been exploited as active media for controlling the LPR frequency or for detecting photo-induced temperature variations in several plasmonic architectures. The work here [5] shows the possibility of combining a large area (1 inch²) of randomly distributed gold NPs (GNPs) immobilized on a glass substrate and covered with a cholesteric LC (CLC) as an active overlayer for controlling simultaneously both the photonic and plasmonic properties of the hybrid system. Upon exposure to resonant radiation, local heating of the NPs induces changes to the optical properties of the CLC in terms of selective reflection. As a consequence, the refractive index change of the CLC induces a blue shift of the LPR frequency of about 20nm. The system demonstrates that suitable optical radiation be utilized to affect both the plasmonic and photonic properties of the system.

References

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5.           De Sio, L., et al., Dynamic optical properties of gold nanoparticles/cholesteric liquid crystal arrays. MRS Communications, 2018: p. 1-6.