Synthesis, Characterization And Structure Control Of Ordered Mesoporous Silica Nanoparticles

Ordered mesoporous silica materials are characterized by uniform and tunable pore size, high surface area and large pore volume. In particular, nano-sized ordered mesoporous silica particles have drawn interest from several fields, including biorelated areas, because silica is benign, possesses chemical stability and can be integrated with other materials. Structural aspects, such as pore connectivity, geometry and pore size are known to govern materials performance. Extensive efforts have been devoted to synthesize mesoporous silica particles with different structures, functionalities and sizes. In contrast, only a small number of studies so far have concentrated on the formation mechanism of these particles. This is hence the focus of the present dissertation. The first part reports on the synthesis and characterization of ordered mesoporous silica nanoparticles with and without embedded magnetic nanoparticles. The formation mechanism of silica nanocomposites is investigated by capturing particle formation at different time points during the synthesis. A combination of transmission electron microscopy (TEM) and small angle x-ray scattering (SAXS) is used to characterize the structure evolution of resulting materials. Incorporating organic moieties into the silica matrix provides additional functionalities to ordered mesoporous silica nanoparticles. However, it often leads to disordered pore structure or pore blockage. The second part demonstrates the preparation of aminated and ordered mesoporous silica nanoparticles using a cocondensation method. Increasing the amount of aminosilane in the synthesis feed causes a structural transition of organically modified particles from hexagonal to cubic. Pore size of ordered mesoporous silica and aminated ordered mesoporous silica nanoparticles can be tailored by the addition of a swelling agent during the synthesis. The structural transformation from hexagonal to cubic is also observed in the latter case, albeit at different amino silane concentrations. The final part reports on the internalization of nanoparticles into cells. Fluorescent aminated mesoporous silica nanoparticles are first prepared and then coated with poly(ethylene glycol) to improve particle stability and lower protein adsorption. Dye-labeled aminated mesoporous silica nanoparticles are spontaneously internalized by cells