Controlled size and high stability SiO₂@ZnO QD’s with high green emission obtained by a simple colloidal route

Abstract

In this work the synthesis of visible ZnO quantum dots (QDs) functionalized/stabilized with oleic acid and core-shelled with SiO2 is presented. A colloidal route was followed to synthesize ZnO QDs with 5 nm average size. Several characterizations were done to identify and assure the core, the stabilization, grain size and QDs emission characteristics. Techniques like FT-IR, XRD, TEM, SEM, UV-Vis, PL and an UV lamp were used to test composition, structural, morphological and emission of the as obtained quantum dots. After the structural and morphological characterization of the particles, they were functionalized with (3-aminopropyl) trimethoxysilane (APTMS). It was observed that the size and morphology are unchanged but the stability depends directly on the APTMS oversaturation which is due to the formation of a thick SiO2 layer. From the PL characterization results it was noticed that the strong green emission is related to the APTMS content and directly related to the shell formation, this emission decreases as the core-shell thickness increases.