Plasmon optics and thermal dissipation in nanocomposite thin films
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Plasmon optics and thermal dissipation in nanocomposite thin films Jeremy R. Dunklin,1 Gregory T. Forcherio,2 Keith R. Berry Jr.,1 and D.K. Roper1,2,* 1 Department of Chemical Engineering, University of Arkansas, Fayetteville, AR 72701 2 MicroElectronics-Photonics Graduate Program, University of Arkansas, Fayetteville, AR 72701 ABSTRACT Optical properties and thermal relaxation dynamics of resonantly excited plasmons are important in applications for optoelectronics, biomedicine, energy, and catalysis. Geometric optics of polydimethylsiloxane (PDMS) thin films containing uniformly or asymmetrically distributed polydisperse reduced AuNPs or uniformly distributed monodisperse solutionsynthesized AuNPs were recently evaluated using a compact linear algebraic sum. Algebraic calculation of geometric transmission, reflection, and attenuation for AuNP-PDMS films provides a simple, workable alternative to effective medium approximations, computationally expensive methods, and fitting of experimental data. This approach allows for the summative optical responses of a sequence of 2D elements comprising a 3D assembly to be analyzed. Thin PDMS films containing 3-7 micron layers of reduced AuNPs were fabricated with a novel diffusive-reduction synthesis technique. Rapid diffusive reduction of AuNPs into asymmetric PDMS thin films provided superior photothermal response relative to thicker films with AuNPs reduced throughout, with a photon-to-heat conversion of up to 3000°C/watt which represents 3230-fold increase over previous AuNP-functionalized systems. Later work showed that introduction of AuNPs into PDMS enhanced thermoplasmonic dissipation coincident with internal reflection of incident resonant irradiation. Measured thermal emission and dynamics of AuNP-PDMS thin films exceeded emission and dynamics attributable by finite element analysis to Mie absorption, Fourier heat conduction, Rayleigh convection, and Stefan-Boltzmann radiation. Refractive-index matching experiments and measured temperature profiles indicated AuNP-containing thin films internally reflected light and dissipated power transverse to the film surface. Enhanced thermoplasmonic dissipation from metal-polymer nanocomposite thin films could affect opto- and bio-electronic implementation of these systems. INTRODUCTION Resonant irradiation of gold nanoparticles (AuNPs) allows localized control of optical and thermal energy. AuNP size and arrangement determine their respective optical and thermal properties. Flexible, transparent polydimethylsiloxane (PDMS) containing AuNPs exhibited high optical absorption and thermal dissipation suitable for optoelectronic and biomedical applications [1–3]. Algebraic calculation of geometric transmission, reflection, and attenuation for AuNP-PDMS films provides a simple alternative to computational methods, and allows the summative optical responses of a sequence of 2D elements comprising a 3D assembly to be analyzed. This work shows AuNP-PDMS extinction is enhanced relative to Mie theory and BeerLambert expectations when AuN
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