(651c) Infrared Active Photocatalysis Through Morphological Control of Semiconductor Nanoparticles/Metal Tip Heterostructures

Semiconductor nanocrystals in strong quantum confinement regime exhibit interesting size-dependent bandgap. The bandgap tunability offers a new opportunity for bandgap engineering; for example, exciton dynamics can be tailored by designing dimensions of heterostructure semiconductor nanocrystals. We synthesized PbSe/CdSe/CdS core/shell/shell nanocrystals with varying morphology, e.g., pyramid and tetrapod. These nanocrystals show varying electron-hole exchange interactions and radiative recombination lifetimes depending on their dimensions. For instance, compared to PbSe nanocrystals, PbSe/CdSe/CdS heterostructure nanocrystals show nearly 2 orders of magnitude longer radiative recombination lifetime. Using this semiconductor light absorber may help increase quantum efficiency in case an exciton has to be dissociated into an electron and a hole. By growing metal tips at the corners of the structures, we prepared semiconductor/metal nanojunction and used the nanomaterials as photocatalysts for reduction of various dyes. Interestingly, the morphology change leads to the difference in the tip growth pattern, and we demonstrate infrared active photocatalysis using the colloidal heteronanostructures.