Autoreduction of Metallic Species on the Surface of Silica Nanoparticles by Surface Functionalization
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1207-N10-60
Autoreduction of Metallic Species on the Surface of Silica Nanoparticles by Surface Functionalization Jorice Samuel1; Olivier Raccurt1; Wai Li Ling2,3, Olivier Poncelet1 1
CEA Grenoble, Department of Nano-Material (DRT/LITEN/DTNM/LCSN), 17 rue des Martyrs, 38054
Grenoble Cedex 9, France 2
CEA LETI-Minatec, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France
3
Institut de Biologie Structurale Jean-Pierre Ebel, CEA-CNRS-UJF, 38027 Grenoble, France
ABSTRACT Silica nanoparticles with metallic nanoclusters are of great interest in many applications from bio imaging to optical devices. Due to the phenomena of surface plasmon resonance, metallic nanoparticles offer specific absorption properties, which depend primarily on the morphology of the nanoparticles. Some techniques have already been well published to encapsulate metallic nanoparticles inside a silica shell. Research interests are now focused on the synthesis of silica nanoparticles covered by either metallic nanoparticles or metallic shells. Two main techniques are described in the literature to bind metallic nanoparticles onto silica nanoparticles. The first consists on the mixing of a metallic colloidal sol with another sol which contains silica nanoparticles having surface functional groups that react with the metal nanoparticles. The second technique is based on the use of a reducing agent to reduce the metallic ions introduced into a suspension of silica nanoparticles. In this paper, we suggest a novel technique based on the dual surface functionalization of silica nanoparticles with amino and thiol functional groups. The metallic ions are reduced by the amino groups to form metallic nanoparticles, which are then chelated by the thiol groups also located on the surface of the silica nanoparticles. The silica nanoparticles are synthesized by a reverse micro-emulsion sol-gel process, which provides mono-dispersed silica nanospheres of ~50 nm in diameter. The surface functionalization of the silica nanospheres is performed by sol-gel reactions within the microemulsion using two silane-coupling agents having either thiol or diamino functional groups. The functionalized silica shell increases the chemical reactivity of the surface of the nanoparticles but the capability of the modified surface to reduce metallic ions depends on the nature of the functional groups. Three surface functionalizations are presented in this study depending on the cou;pling agent involved: (i) diamino groups, (ii) thiol groups, and (iii) the combination of diamino and thiol groups. We show that metallic nanoparticles are generated on the silica surface in the third case, when both diamino and thiol groups are present. INTRODUCTION Silica nanoparticles with metallic nanoclusters are of great interest in many applications from bio imaging to optical devices. Metallic nanoparticles provide specific absorption properties through the phenomenon of surface plasmon resonance, which depends on both the size and the morphology of the nanoparticles [1]. The encapsulation of metal
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