Selectively immobilizing silica nanoparticles encapsulated in functional polymer brushes via RAFT polymerization onto prepared silicon surfaces

In this study a scheme for the selective immobilization of silica nanoparticles on silicon surfaces was developed. The particular methodology explored takes advantage of the broad diversity of chemical moieties afforded by the introduction of polymer brushes grafted from the nanoparticle surface. The functional groups in the polymer brush function as half of a chemical linker, while small molecules bound to the silicon surface via self assembled monolayers serve as the complimentary portion of the linkage system. Several monomers were synthesized for use in ATRP or RAFT polymerizations from the surface of the silica nanoparticles. The resulting polymer encapsulated nanoparticles were immobilized on prepared silicon surfaces and the surface densities of the various immobilized nanoparticles were compared using atomic force microscopy. Nanoparticles encapsulated using ATRP were found to result in significantly lower nanoparticle surface densities than those prepared using RAFT polymerizations. Additionally, methodologies for nanoparticle immobilization were compared, with the most effective technique being the evaporative deposition of the nanoparticles from a dilute suspension. The final portion of the study demonstrated how the immobilization system could be used to create more complex nanoarchitectures via layer by layer assembly techniques.