The goal of the project is to use this property to induce localized thermal decomposition of organometallic molecules around the nanoparticles when they are exposed to high-energy ultrafast lasers.
Using a modified chemical vapor deposition technique, an optically clear polymer is infused with organometallic molecules and exposed to high temperatures, resulting in the thermal decomposition of the organometallics and the subsequent growth of nanoparticles within the polymer. The resulting system is a nanocomposite with a statistically random distribution of discrete and stable nanoparticles with uniform size and shape. The optical properties of the nanocomposite depend upon the material of the nanoparticles, as well as their size, shape, and concentration within the polymer matrix. These nanoparticles exhibit highly absorptive optical cross sections. The goal of the project is to use this property to induce localized thermal decomposition of organometallic molecules around the nanoparticles when they are exposed to high-energy ultrafast lasers. Using optical masks and laser processing, combined with multiple organometallic infusions, it is possible to pattern nanocomposites in order to control the location, composition, size, and distribution of the nanoparticles within the polymer matrix, resulting in tailored electrical, optical, and photocatalytic properties. Currently, we have been able to red shift the SPR of Ag nanoparticles by 20nm in the ultrafast laser irradiated regions. This behavior is in agreement with optical models that predict a similar red shift due to a core-shell nanoparticle geometry, specifically a 14nm diameter Ag core and a 3nm WO3 shell, which was also confirmed by TEM examinations.
This research focuses on fundamental issues connected to the synthesis and processing of polymer matrix nanocomposites (PMNCs). The methods being investigated allow for the scalable production of materials with specific engineered properties related to photochromic, photocatalytic or photosynthetic behaviors. In the case of photochromic PMNCs, related processing methods could lead to coatings for windows that would have a broad impact on the national energy budget. Optically-based processing also permits controlled patterning of PMNCs allowing for creation of functional, hierarchical microstructures. This project also includes educational outreach efforts through the Johns Hopkins University Center for Educational Outreach which provides laboratory experiences for high school students from underrepresented groups.