Synthesis and Characterization of Core−Shell FePt@Ti-Containing Silica Spherical Nanocomposite as a Catalyst Carrier for Liquid-Phase Reactions

Abstract

Colloidal FePt nanoparticles stabilized by oleic acid and oleylamine were modified through a ligand exchange with (3-mercaptpropyl)-trimethoxysilane. The particles were subsequently treated using the so-gel route with tetraethyl orthosilicate and tetrapropylorthotitanate. A new nanocomposite (FePt@Ti-SiO2) was characterized by means of X-ray diffraction, IR, transmission electron microscopy, superconducting quantum interface device, and X-ray absorption fine structure measurements. The face-centered cubic FePt NPs with a mean diameter of ca. 6 nm were encapsulated in the Ti-SiO2 thick shell, which exhibited superparamagnetic behavior at 300 K with zero remanence and coercivity. The Ti-oxide moiety was proven to exist in the isolated and tetrahedral form. The FePt@Ti-SiO2 served as an efficient nanocatalyst for the liquid-phase selective epoxidation using hydrogen peroxide (H2O2). Recovery from the reaction mixture was readily attained by applying an external permanent magnet, and the spent catalyst could be recycled without any appreciable loss in activity.