Manipulation of Intraparticle Charge Delocalization by Conjugated Metal-Ligand Interfacial Bonds

University Of California-Santa Cruz, Santa Cruz CA

Investigators

Abstract

Nanoscaled particles, having dimensions on the order of a billionth of a meter, show many technologically important properties, and are therefore actively under research. Dr. Shaowei Chen of the University of California Santa Cruz (UCSC) studies transition metal nanoparticles that are stabilized with an organic capping layer (the ligand), making the capped nanoparticles dispersible in common solvents and useful in many applications. Dr. Chen's research shows that the chemical bonds between the metal nanoparticle cores and the organic ligands can be exploited as a new, effective way of manipulating nanoparticle properties. In this project, Dr. Chen and his students are interested in examining the fundamental chemical nature of the nanoparticle-ligand interfacial bonds and examining the impacts of nanoparticle core metals and core size on the formation of the bonds. Results from these studies are critical to the establishment of a correlation between the nanoparticle structures and properties that will enable the nanoparticles to be used in optical devices, sensors and other advanced applications. As charge transfer is a fundamental process in a wide range of important applications where nanoparticle materials are unique building blocks, it is envisioned that research on nanoparticles may have impacts on the electronics and energy industries, health care, and homeland security. Dr. Chen involves high school, undergraduate and graduate students in his research and actively participates in various outreach programs such as the UCSC ACCESS, UC LEADS, (the University of California Leadership Excellence through Advanced Degrees), the Summer Internship Program (SIP) and California State Summer School for Mathematics (COSMOS) programs. In this research program, Dr. Shaowei Chen of the University of California Santa Cruz (UCSC) is supported by the Macromolecular, Supramolecular and Nanochemistry (MSN) Program to study the impacts of metal-ligand interfacial bonding interactions on the nanoparticle chemical and physical properties. Dr. Chen has developed new surface adsorption chemistries in which metal-carbon, -oxygen, or -nitrogen covalent bonds readily form to result in the passivation and functionalization of transition-metal nanoparticles consisting of ruthenium, platinum and copper and combinations of core/shell, and core/shell/shell architectures. The reduced interfacial resistance resulting from the functionalization facilitates interparticle charge transfer, in sharp contrast to nanoparticles functionalized with the more commonly used mercapto derivatives. In particular, the formation of conjugated metal-ligand interfacial bonds leads to effective intraparticle charge delocalization between particle-bound functional moieties, and the emergence of optical and electronic properties that are analogous to those of their dimeric counterparts. Dr. Chen's research advances the understanding of the fundamental chemical nature of the interfacial bonds and examines the impact of nanoparticle core metals and core size on the formation of conjugated metal-ligand interfacial bonds. Results from these studies are critical in the establishment of an unambiguous correlation between the nanoparticle structures and properties. Dr. Chen involves high school, undergraduate and graduate students in his research and actively participates in various outreach programs such as the UCSC ACCESS, UC LEADS, (the University of California Leadership Excellence through Advanced Degrees), the Summer Internship Program (SIP) and California State Summer School for Mathematics (COSMOS) programs.