Atomic Layer Deposition (ALD) processing will be carried out to modify the surface chemistry of ultrafine particles at large scale and to investigate the utility of the modified particles for UVA/UVB transmittance and self assembly. In one aspect of the research, multilayered and nanolaminated ceramic films will be placed on the surface of individual primary submicron and nanosized inorganic particles using a fluidized bed process. The research effort includes an understanding of the fluidization behavior of the submicron and nanosized particles that are affected by interparticle forces and that fluidize as dynamic aggregates, and the subsequent ability to nanocoat individual primary particles fluidizing as light aggregates. This is a first attempt to place nanothick multilayers on fluidized particles by ALD. A sunscreen UVA/UVB system (ZnO/TiO2) has been selected to provide for a well characterized application with definitive methods for testing the composite powder behavior in non-aqueous formulations (sunscreen lotions). In another aspect of the research, inorganic nanofilms will be placed on the surface of nanospherical particles by ALD to control their surface charge (anionic and cationic). Solutions containing equal concentration of oppositely charged nanospheres will be investigated for ionic self-assembly into nanospherical "salts". The investigation will be extended to bilayered coatings on nanosized substrate particles where the inner layer imparts optical functionality on the nanoparticles and the outer layer imparts charge functionality for ionic self assembly. In this manner, the self assembly of photonic crystalline arrays with controlled diffraction patterns will be investigated. The overall goal of the project is to demonstrate multi-layered films on ultrafine particles by ALD and the utility of such surface modified particles in formulations and nanofabricated arrays.
This novel research provides for the large scale control of nanoparticle surface chemistry to facilitate the use of functionalized nanoparticles in formulations and for fabricating novel components. The nanoparticle surface coating method to be investigated is enabling and widely applicable to many systems. This research provides for a unique educational experience for two Ph.D. students and approximately 20 undergraduates over the three year program. A local industrial partner, ALD Nanosolutions, has agreed to work with the students (e.g., through capstone design projects) to better understand both the scientific and applied aspects of the research and to facilitate technology transfer.
