Effect of Core-Shell SiO2@Ag Nanoparticles with Raspberry-like Morphology on the Excited States of Photosensitizers.

JOAQUÍN E. MARTINEZ PORCEL; VALERIA B. ARCE; DANIEL MARTIRE; MARÍA BELÉN RIVAS AIELLO; DESIRE DI SILVIO; L. YATE; SERGIO E. MOYA

Congreso; Encuentro de Física y Química de superficies 2018; 2018

Effectof Core-Shell SiO2@Ag Nanoparticles with Raspberry-like Morphologyon the Excited States of Photosensitizers  J.E. Martínez Porcel,1,2 M.B. RivasAiello,1 V.B. Arce,3 D. Di Silvio,2 L.Yate,2 S.E. Moya,2 D.O. Mártire21 Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas(INIFTA), Universidad Nacional de La Plata, La Plata, Argentina.‎2 Centre forCooperative Research in Biomaterials, CICbiomaGUNE Unidad Biosuperficies, SanSebastian, Spain.3 Centro de Investigaciones Ópticas (CIOp), (CONICET La Plata - CIC -UNLP), Gonnet, Argentina.‎varce@ciop.unlp.edu.ar Wehere prepare and characterize core-shell silica silver nanoparticles withraspberry-like morphology (SiO2@AgNPs) for studying their effect onthe triplet states of organic photosensitizers. This nanomaterial was chosenfor two main reasons: (a) The surface of the nanoparticles presents exposedsilanol groups, which can potentially act as sites for the adsorption oforganic molecules. (b) It offers the possibility of performing comparativeexperiments with the silica nanoparticles without silver shell (SiO2NP)in order to corroborate whether the observed effects of SiO2@AgNP onthe photophysics of the photosensitizers are due to the metal and not only toimmobilization of the dyes on the silica surface.Forthe synthesis of SiO2@AgNPs from SiO2NPs a new strategywas developed. This new method involves in the two first steps the homogeneousdeposition of silver nuclei on colloidal silica spheres reported by the groupof Liz-Marzán1. Then, for the growth of Ag nanoparticles from seedsthe photochemical method reported by the group of Scaiano2 wasapplied. This procedure consists in the photogeneration of ketyl radicals,produced by photolysis of the substituted benzoin Irgacure-2959 (I-2959), whichare able to reduce Ag+ ions to metallic silver. Wehere investigate the interaction of SiO2@AgNPs with the excitedstates of two photosensitizers with photodynamic action: the anionic form ofRose Bengal and the neutral Riboflavin molecule (Rf). Under similar conditionstransient absorption spectroscopy experiments showed that the triplet excitedstate of Riboflavin is not observed, whereas no effect of the nanoparticles onthe triplet excited state of Rose Bengal was detected. These data wereinterpreted in terms of a charge transfer process from the excited state of thecomplex form between Rf and the nanoparticles to the silver nanoparticles. Asimilar reaction seems not to be possible in the case of Rose Bengal. Referencias1.       Kobayashi, Y.;Salgueiriño-Maceira, V.; Liz-Marzán, L. M. ?Deposition of Silver Nanoparticleson Silica Spheres by Pretreatment Steps in Electroless Plating? Chem. Mater., Vol. 13, No. 5, 1630 ?1633, 2001.2.       McGilvray, K. L.;Fasciani, C.; Bueno-Alejo, C. J.; Schwartz-Narbonne, R.; Scaiano, J. C.?Photochemical Strategies for the Seed-Mediated Growth of Gold and Gold−SilverNanoparticles? Langmuir, Vol. 28, No.46, 16148−16155, 2012..