Chemical reactions that involve the transfer of an electron from a metal to a molecule adsorbed to its surface are some of the most important in chemistry, as they form the basis for applications ranging from catalysis to sensing. The study of these electrochemical reactions is challenging, however. Catalytic reactions for example can involve the transfer of multiple electrons, and reaction efficiency can be highly dependent on the local arrangement of metal atoms near the molecular adsorbate. Traditional electrochemistry techniques sample the entire metal electrode, which can contain a vast number of nanoscale metallic features, making it difficult to draw clear connections between the local metal structure and the chemical activity. In this project funded by the Chemical Structure Dynamics and Mechanism (CSDM-A) program of the Chemistry Division, Professor Michael Mirkin of the City University of New York, Queens College is advancing nanoelectrochemical methods and using them to study catalytic reactions taking place on the surfaces of metallic nanoparticles and nanorods. Unlike traditional electrochemistry techniques, the scanning electrochemical microscopy (SECM) method used by Professor Mirkin and his students can monitor a region of the surface that is only 10 nm across, or about the equivalent of 30 gold atoms. This high spatial resolution enables the team to characterize not just individual particles, but different sections of the same particle. Their results could have broad implications for fields ranging from the development of ultrasensitive detectors, to catalysis for energy conversion and storage. The project is also providing training opportunities for graduate and undergraduate students, who are getting multidisciplinary research experience in interfacial electrochemistry, bioanalytical chemistry and nanoscience.
Nanoelectrochemical techniques, such as steady-state voltammetry, SECM, and nanoparticle collisions, are combined with high-resolution tunneling electron microscopy and finite-element simulations to study the fundamental processes that impact the detection of electrochemical events on nanometer length scales. The project is investigating electrochemical processes in microscopic carbon cavities, long-distance transfer of electrons between metal nanoparticles and electrodes, and spatial variations in surface reactivity around catalytically active metallic nanorods. The interactions between single nanoparticles and nanoelectrodes are investigated by two approaches. In the first, the SECM nanotip is brought to within the tunneling distance of a single nanoparticle, and the tunneling current is detected, while the second approach monitors electron tunneling as nanoparticles collide with the electrode. The main objective is to develop the experimental and theoretical framework for mechanistic studies and visualization of complex nanoelectrochemical systems.
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.
