Dr. Jun-Hyun Kim

Research Interests & Areas

Hollow Polymer Nanoparticles for Drug-Delivery Vehicles. We are interested in constructing hollow polymer nanoparticles (hPNPs) for use as selective/specific drug-delivery carriers that can have high drug-loading capacity, easy surface modification, and excellent stability. These polymeric materials can be reliably prepared by using a conventional radical polymerization to grow a shell of polymer around monodipserse sacrificial inorganic silica nanoparticles having tunable sizes. This approach can allow for the synthesis and development of uniform core-shell nanoparticles with tunable shell thicknesses from the nanometer to micron size. After cross-linking the resulting polymer shell via amide and/or ester bond, the removal of the silica cores with diluted fluoride can allow for the formation of stable shell cross-linked hPNPs. The crosslinking process can allow for the formation of hydrolytically degradable and biodegradable amide/ester bonds leading to the effective release of the encapsulated drugs in vivo. Thus, our hPNPs possess an additional feature for controlled release properties. These structures can then be highly loaded with small-molecule therapeutic agents within the hollow core to yield drug-delivery vehicles. In addition, surface functionalization of hPNPs with specific/selective targeting groups would enable them to be used as drug-delivery vehicles that can possess effective release properties at disease site. Our research, based on a combination of nanoscale materials and polymer chemistry, offers a unique means for the reliable preparation of complex polymer-based nanostructures that will form the next generation of multipurpose drug-delivery systems. Photochemical synthesis of nanoscale metal particles for catalytic applications. The main goal of this research is to prepare various metal nanoparticles (gold, silver, copper, palladium, and their alloys) possessing tunable absorption properties, and to examine their photothermal heating efficiency and catalytic activity in chemical reactions upon irradiation of a solar simulated light. Conventional spherical metal nanoparticles possess a strong but narrow absorption peak in the visible light area. Simply modified metal nanoparticles, however, can have a strong and wide absorption band across the visible to near infrared region, which largely covers the intense solar radiation spectrum on the Earth. As metal nanoparticles have a unique ability to absorb light energy and convert it into heat, the irradiation of these anisotropic metal nanoparticles with solar light can photothermally increase the temperature of the reaction media and the surface of the nanoparticles. Since most catalytic reactions take place on the surface of catalysts (e.g., a metal substance) and often require a moderate reaction temperature, employing these optically-active metal nanoparticles can enhance the reaction yields and reduce the reaction time without any electrical thermal input. Considering recent environmental concerns and the soaring demand for renewable energy this study is especially relevant. A thorough investigation of the structure-dependent absorption properties and the photothermal heating efficiency of metal nanomaterials and their catalytic activity in chemical reactions (including reduction, hydrogenation, homocoupling, Suzuki, and Ullman reactions) under a solar-simulated light allows for the development of highly effective, practical, and cost-efficient catalytic systems. Light-induced sysnthesis of gold nanoparticles Metal nanoparticle catalysis upon exposure to sunlight