Plasmonic Nanoparticle Networks for Light and Heat Concentration

TL;DR

This paper demonstrates how self-assembled plasmonic nanoparticle networks can efficiently concentrate light and heat, with controllable optical field distribution and potential applications in hyperthermia, supported by experimental imaging and theoretical modeling.

Contribution

It introduces a unified theoretical framework and experimental validation for light and heat concentration in plasmonic nanoparticle networks, enabling precise control of their optical and thermal properties.

Findings

Optical fields can be modulated by incident polarization.

Heat is evenly spread over the network, suitable for hyperthermia.

Theoretical simulations match experimental imaging results.

Abstract

Self-assembled Plasmonic Nanoparticle Networks (PNN) composed of chains of 12-nm diameter crystalline gold nanoparticles exhibit a longitudinally coupled plasmon mode cen- tered at 700 nm. We have exploited this longitudinal absorption band to efficiently confine light fields and concentrate heat sources in the close vicinity of these plasmonic chain net- works. The mapping of the two phenomena on the same superstructures was performed by combining two-photon luminescence (TPL) and fluorescence polarization anisotropy (FPA) imaging techniques. Besides the light and heat concentration, we show experimentally that the planar spatial distribution of optical field intensity can be simply modulated by controlling the linear polarization of the incident optical excitation. On the contrary, the heat production, which is obtained here by exciting the structures within the optically transparent window of biological tissues, is evenly spread over the entire PNN. This contrasts with the usual case of localized heating in continuous nanowires, thus opening opportunities for these networks in light-induced hyperthermia applications. Furthermore, we propose a unified theoretical framework to account for both the non-linear optical and thermal near-fields around PNN. The associated numerical simulations, based on a Green s function formalism, are in excellent agreement with the experimental images. This formalism therefore provides a versatile tool for the accurate engineering of optical and thermodynamical properties of complex plasmonic colloidal architectures.