Seung Hyun Kim

Hot Carrier-Driven Catalytic Reactions on Pt–CdSe–Pt Nanodumbbells and Pt/GaN under Light Irradiation

Hybrid nanocatalysts consisting of metal nanoparticle-semiconductor junctions offer an interesting platform to study the role of metal-oxide interfaces and hot electron flows in heterogeneous catalysis. Here, we report that hot carriers generated upon photon absorption significantly impact the catalytic activity of CO oxidation. We found that Pt-CdSe-Pt nanodumbbells exhibit a higher turnover frequency by a factor of 2 during irradiation by light with energy higher than the bandgap of CdSe, while the turnover rate on bare Pt nanoparticles did not depend on light irradiation. We found that Pt nanoparticles deposited on a GaN substrate under light irradiation exhibit changes in catalytic activity of CO oxidation that depends on the type of doping of the GaN. We suppose that hot electrons are generated upon the absorption of photons by the semiconducting nanorods or substrates, whereafter the hot electrons are injected into the Pt nanoparticles, resulting in the change in catalytic activity. The results imply that hot carrier flows generated during light irradiation significantly influence the catalytic activity of CO oxidation, leading to potential applications as a hot electron-based catalytic actuator.

Monte Carlo Simulation of Polymers Confined Between Two Surfaces in the Presence of Diluent

Structure and surface properties of polymers confied between two surfaces are studied in the presence of diluent by using an off-lattice Monte Carlo method. When the diluent-chain interaction is weak, the density of diluent beads near the surface increases sharply with increasing the diluent-surface interaction while the chain bead density near the surface decreases gradually. The total bead density near the surface increases with increasing the diluent-surface interaction until it exceeds the total bulk density. This is mainly due to a large increase in the diluent bead density near the surface. Because of the increase of diluent at the surface, chains near the surface change their conformation, i.e., long tails become abundant while short trains and loops are relatively depleted. On the other hand, when the diluent-chain interaction becomes strong, the total bead density near the surface increases slightly, but it exceeds the total bulk density only when the diluent-surface interaction is strong enough, because the diluents approaching the surface induce chain beads to move to the surface due to strong interaction between the chain and diluent.

Sequential transformation of the crystalline rod domain from a flat ribbon to segmented columnar to micellar structure

Abstract