Metal oxide thin films grafted on silica gel surfaces: Recent advances on the analytical application of these materials

In the highly dispersed MxOy monolayer film on a porous SiO2 surface, denot ed as SiO2/MxOy, the Si-O-M covalent bond formed on the SiO2 surface restri cts the mobility of the attached oxide resulting in coordinatively unsatura ted metal oxides (LAS) in addition to the Bronsted acid sites (BAS). The BA S arise from the MOH and SiOH groups, the latter due to the unreacted silan ol groups. As the attached oxides are strongly immobilized on the surface, they are also thermally very stable. The amphoteric character of most of th e attached oxides allows the immobilization of various chemical species, ac id or bases, resulting in a wide application of these surface modified mate rials. In this work many of the recent applications of these MxOy coated si lica surfaces are described, such as selective adsorbents, in preconcentrat ion processes, as new packing material for use in HPLC, support for immobil ization of enzymes, amperometric electrodes, sensors and biosensors.