On Heavier Chalcogen (Se and Te) Interfacial Chemistry and Charge Transfer in Monolayer-Protected Metal Nanoparticles

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Metal nanoparticles are metal particles of very small (nanometer scale) dimensions. They possess novel chemical and physical properties that are very different from those of large particles or bulk metals. Dr. YuYe Tong of Georgetown University and Dr. Thomas Allison at the National Institute of Standards and Technology conduct research to gain a better understanding of the structural parameters that govern the properties of metal nanoparticles. The long-term goal is to harness the novel properties of nanoparticles for practical applications (such as electronic or optical devices, biomedical diagnosis, and drug delivery). This project provides interdisciplinary research opportunities to students, training them in the use of the state-of-the-art instruments for studying nanoparticles. Through Georgetown University's partnership with the Cesar Chavez Public Charter Schools in Southeast Washington DC, which have very high population of students of underrepresented groups or from low-income families, Dr. Tong participates in a project to help develop new chemistry curricula for local charter schools. This project serves as a springboard to attract more women and underrepresented students to STEM fields.Dr. Tong and Dr. Allison explore the use of heavier chalcogen (Se and Te) as alternative anchoring elements to the prevailingly used sulfur for attaching organic molecular wires to metal surfaces. Using a combination of experimental techniques and Density Functional Theory (DFT) computations, they aim to gain a better mechanistic understanding of the metal-chalcogenolate interfacial chemistry and its ramifications on charge transfer/transport in single monolayer-protected nanoparticle (MPN) and MPN assemblies. Specifically, this research entails: 1) the synthesis of different sizes (1 to 5 nm) of nanoparticles of different metal elements (Au, Ag, Cu, Pt, and Pd), which are protected with ligands of different organic backbones (alkyl and aryl), alkyl chain lengths (C6, C8, and C12), and anchoring chalcogen elements (Se and Te); 2) the characterization of the afore-synthesized MPNs by in situ electrochemical (EC) spectroscopic (NMR/IR/Raman) techniques and ex situ X-ray photoemission spectroscopy; and 3) comparative mechanistic investigations of charge transfer through a single MPN and MPN assemblies using EC scanning tunneling microscopy and traditional EC measurements.