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2018-11-05 - Colloque/Présentation - communication orale - Anglais - page(s)

Guyot Corentin , Olivier Deparis, Voué Michel , "Light backscattering of gold nanoparticles at high concentration in a polymer matrix" in Metallic Nano-Objects, Lyon, France, 2018

  • Codes CREF : Matériaux optiques (DI1256), Physique (DI1200), Optique (DI1250)
  • Unités de recherche UMONS : Physique des matériaux et Optique (S878)
  • Instituts UMONS : Institut de Recherche en Science et Ingénierie des Matériaux (Matériaux)
  • Centres UMONS : Physique des matériaux (CRPM)

Abstract(s) :

(Anglais) One-pot synthesis of polymer films embedding noble metal nanoparticles has many applications due to its relative simplicity. In this study, nanocomposites made of polymer films embedding gold nanoparticles (GNPs) were prepared by thermal annealing of poly-(vinyl) alcohol films containing HAuCl4. One can use GNPs in spectral selective coatings to block solar infrared radiation, in random lasers, in non-linear optical applications and more recently as saturable absorbers in passive Q-switch systems [1]. Such devices are usually prepared according to a two-steps procedure [2]: synthesis of NPs in a liquid medium and dispersion in the polymer solution before deposition. Using such a method does not lead to high volume fractions of NPs in the final film. One-pot synthesis can overcome this drawback but the high GNPs concentration lead to light back-scattering, a crucial issue for fiber optics integration. To the best of our knowledge, nobody has so far paid attention to this phenomenon in correlation with the modifications of the optical properties of the nanocomposites induced by the in situ growth of the nanoparticles. The optical scattering of the nanocomposite films was analyzed by the bi-directional reflection distribution function (BRDF). Annealing of the samples at 135°C during 90 min increases the roughness of the film and the light scattering at the surface. The BRDF shows that annealing samples induces an important back-reflection of the incident light. In parallel with the increase of the scattering, the locally resolved Ψ and Δ ellipsometric angles are also strongly modified by the annealing process and a diffraction pattern corresponding to local modifications of the optical properties gradually appears. They are suspected to be the manifestation of light intensity diffraction patterns. This change is due to the growth of the GNPs which locally change the optical response of the film. The reflectivity of the samples was measured before, during and after the annealing process. It shows the progressive thinning of the polymer film as well as the decreasing reflectivity around 550 nm due to the energy absorption by the growing of the GNPs. References: [1] D. Wu, J. Peng, Z. Cai, J. Weng, Z. Luo, N. Chen and H. Xu, Opt. Express 23, 24071 (2015) [2] Z. Kang, X. Guo, Z. Jia, Y. Xu, L. Liu, D. Zhao, G. Qin and W. Qin, Opt. Mater. Express, 3, 1986 (2013) * Corresponding author : corentin.guyot@umons.ac.be