Continuous aerosol photopolymerization to coat de-agglomerated nanoparticles

A novel continuous aerosol photopolymerization technique to coat nanoparticles that have been previously deagglomerated is presented. After de-agglomeration in a jet-impactor assisted fluidized bed, monomer vapors are condensed onto the surface of aerosolized nanoparticles via heterogeneous condensation. Photopolymerization is initiated through exposure to UV light. To demonstrate the process, titanium dioxide (TiO2) and methyl methacrylate (MMA) were selected as nanoparticle and organic monomer, respectively. We demonstrated this light-based technique, operated at ambient pressure and room temperature, is able to graft a PMMA-like film with a thickness of 1.5 nm on the surface of nanoparticles, confirmed by TEM and FTIR. XPS analysis confirmed formation of covalent bonds with the TiO2 surface, indicating a surface-initiated photopolymerization. Particle size measurements in suspension illustrated the efficiency of the de-agglomeration and subsequent coating process, as coated particles remained smaller than bare particles. UV-Vis absorbance spectra show that the coating facilitates dispersion in non-polar solvents. Finally, long-term stability experiment confirmed the suspension stability is enhanced not only because of the reduction of agglomerate sizes, but also as a result of the carbon coating that improves the interfacial interactions among particles, and between particles and solvent. This technique can be easily combined with any continuous inorganic nanoparticle generation process as a solvent-free post-synthesis approach to impart a functional coating.