Point of Anchor: Impacts on Interfacial Charge Transfer of Semiconductor Nanoparticles

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Professor Shaowei Chen of the University of California-Santa Cruz is supported by the Macromolecular, Supramolecular, and Nanochemistry Program of the Division of Chemistry to develop new chemical bonding patterns to stabilize semiconductor nanoparticles with an organic protective layer. Semiconductor nanoparticles are a unique family of functional materials that have found diverse practical applications. A semiconductor has an electrical conductivity between that of a conductor, such as metallic copper, and an insulator, such as glass. Semiconductors are used in laser diodes, solar cells, electronic circuits, etc. This research projects seeks to judicially select the chemical linkage to the surface of the semiconductor nanoparticles so as to tune their optical and electronic properties and enhance their use in optoelectronic devices, sensors and other practical applications. In particular, the focus of this project is to enhance the photocatalytic activity of the nanoparticles in the use of light energy for efficient chemical conversions to specific products. Graduate students are trained in advanced multidisciplinary research methods. In addition, research activities are closely integrated with several educational and outreach programs to motivate minority, women, disadvantaged undergraduate students and qualified high-school students from the local area. The research experience prepares these students for future careers in STEM areas. Semiconductor nanoparticles represent a unique class of functional nanomaterials that have found diverse applications, such as catalysis, optoelectronics, (bio)imaging, and (bio)diagnosis. Analogous to their metallic counterparts, semiconductor nanoparticles are generally functionalized with select organic capping ligands, ranging from small molecules to metal complexes and to polymeric matrices. In earlier studies, the semiconductor nanoparticle-ligand interactions mostly involved nonconjugated linkages, which significantly impeded the electronic coupling between the nanoparticle core and functional moieties of the capping ligands, so that a large amount of energy was needed to induce charge transfer across the interface. Such a barrier can be efficiently diminished with a conjugated core-ligand interfacial linkage. Thus, the central goal of the present research project is three-fold: to develop new interfacial chemistry for the surface functionalization of semiconductor nanoparticles, to examine the impacts of interfacial bonding interactions (conjugated vs. nonconjugated) on the nanoparticle optical and electronic properties, and to exploit these unique materials properties to enhance the materials applications in photocatalysis. Through a deliberate combination of theoretical and experimental studies, this research may enrich the toolbox of semiconductor nanoparticle surface functionalization, an important fundamental framework for enhanced applications.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.