UV-Active Functionalized Silica Nanoparticles

Immobilization of active molecules by attachment onto solid surfaces is a well-established practice in many processes and applications. Silica micro- and nano-particles are attractive candidates as support for active molecules as result of a combination of desirable properties. The present study deals with grafting of functional UV active molecules onto silica surfaces via hydrosilylation reactions using multivalent organosilicon spacers.

Different types of organosilicon precursors based on dimethylsiloxysilanes containing multiple SiH groups were used as spacers between vinyl-modified silica surface and the benzotriazole UV-absorber (UVA). First, the surface of silica was modified with vinyltrimetoxsisilane coupling agent. Subsequently, the UVA molecules were attached to the silica-vinyl by a two-step procedure involving hydrosilylation reaction. UV active molecules has been successfully attached onto vinyl-modified silica surface using different types of multivalent organosilicon precursors, which were used as spacers between vinyl-modified silica surface and the UV-absorber. The successful grafting was confirmed by FTIR, TGA and UV-Vis characterization.

More than fivefold increase in UVA loading was found for the MH30 multifunctional spacer, which contains approximately 75 SiH groups per molecule, when compared to a four-functional spacer. Furthermore, a branched, bulky six functional spacer outperforms the linear spacer of the same functionality. UV activity of functionalized silica was study by UV-VIS spectroscopy, confirming that the immobilization of UVA onto silica surface has not altered its UV absorbance properties.