Intrinsic optical properties of Ag-doped poly-(vinyl alcohol) nanocomposites: an analysis of the film thickness effect o
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Intrinsic optical properties of Ag‑doped poly‑(vinyl alcohol) nanocomposites: an analysis of the film thickness effect on the plasmonic resonance parameters Corentin Guyot1 · Michel Voué1 Received: 13 July 2020 / Accepted: 4 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The optical properties of silver nanoparticles originating from the collective oscillations of their conduction electrons (LSPR) play a major role in the development of nanotechnology-based optical devices, from optical sensors to bactericide materials via non-linear optical devices. In this study, nanocomposites polymer films embedding silver nanoparticles were prepared by thermal annealing of poly-(vinyl alcohol) films doped by silver nitrate using a “one-pot synthesis” method. In this upscalable solution-based process, the nanoparticles are directly grown in the polymer matrix, yielding a plasmonic nanocomposite with a high density of nano-objects. Low (2.5% w:w) and high (25% w:w) doping concentration of silver were considered as well as their effect on the optical properties of thin (30 nm) and thick (300 nm and more) films. The topography and the optical properties (refractive index n and extinction coefficient k) of such films were studied by atomic force microscopy and spectroscopic ellipsometry. Unexpectedly, for a given doping level, the parameters of the surface plasmon resonance (amplitude, position and width) were shown to be thickness-dependent. A multivariate statistical analysis technique was used to identify the differences in the optical behavior of thick and thin films. Keywords Plasmonic nanocomposites · Spectroscopic ellipsometry · Silver nanoparticles · Multivariate analysis · Polymer films · Nanoparticles growth · Support vector machine
1 Introduction Plasmonic nanocomposites (PNCs) belong to an emerging class of materials whose optical properties take advantage of the surface plasmon resonance of the metal nanoparticles (NPs) embedded in a dielectric matrix. They are highly customizable by tuning the nanostructures shape and size as well as the mechanical behavior (stiffness, flexibility, Young’s modulus) and physical properties (glass transition) of the matrix [1]. PNCs have numerous applications such as optical sensors, non-linear optical devices [2–5], biosensors or bactericide materials [6–10]. The study of their
* Michel Voué [email protected] Corentin Guyot [email protected] 1
Research Institute for Materials Science and Engineering, Physics of Materials and Optics, University of Mons, Mons, Belgium
optical properties is an active research field and is driven by the interest for the Localized Surface Plasmon Resonance (LSPR). Well-known in its effect since e.g. the optical aspect of the Lycurcus cup (4th CE) or of the mosaics of Saint Sabina (5th CE) [11], the LSPR appears when free electrons of the metal are excited by the electromagnetic field associated to the propagation of light [12, 13]. The most popular way to prepare these PNCs is the “bottom-up” ap
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