Abstract
We experimentally demonstrate that the plasmonic heat delivered by a single layer of homogeneously distributed gold nanoparticles (AuNPs), immobilized on a glass substrate, can be optically tuned by taking advantage of the properties of an organic layer based on azobenzene and nematic liquid crystal (NLC) molecules. The effect, which exploits the dependence of the NLC refractive index value on the molecular director orientation, is realized using the polarization-dependent, light-induced molecular reorientation of a thin film of photo-aligning material that the NLC is in contact with. The reversibility of the optically induced molecular director reorientation of the NLC enables an active modulation of the plasmonic photo-induced heat.
Highlights
PAAD-27 can be used to align liquid crystals; for this reason, we have studied the behavior of a sample of AuNPs + PAAD-27 modified by adding a nematic liquid crystal (NLC, see Materials and Methods section) to investigate how a variation of the optical properties of the new medium surrounding the AuNPs, determines variations of the thermal efficiency of the whole system that are not related to a change in the value of the thermal conductivity k H of some of its components
We proved that: (a) by exploiting a photo-aligning material (PAAD-27) alone it is possible to modify the photo-thermal efficiency of a monolayer of gold nanoparticles (AuNPs); (b) the photo-aligning material, as driven by a polarized UV light, can be exploited to reorient the director of NLC molecules used as host medium of an AuNPs monolayer; this director reorientation induces a modification of the effective refractive index of the NLC as seen by the AuNPs; in turn, this variation affects the photothermal response of the monolayer of AuNPs
The presence of the PAAD-27 leads to a modulation of the photo thermal response whose photo-thermal range extension can be maximized using the PAAD27 as photoaligning layer for NLC
Summary
Thermoplasmonics deals with the heat produced by metallic nanoparticles (NPs) when a radiation with suitable (resonant) wavelength impinges on them [1,2]. When the electrons of the conduction band of a metallic NP oscillate coherently with the electric field of the incident radiation, an increase of the absorption in the corresponding frequency range occurs (ω p ) that leads to a rapid rise in the temperature of the NP, followed by a heat dissipation into surrounding media [3,4]. The temperature increase (∆T) of a single spherical NP can be expressed as ∆T = Q/(4πk H R NP ), where R NP is the NP radius, k H is the thermal conductivity of the host medium, and Q is the heat power density. For a metallic NP with spherical or rod-like shape, σabs can be calculated using the Mie or
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
