In this project supported by the Chemical Structure, Dynamics and Mechanisms Program of the Chemistry Division, Professor Michael Mirkin and his research team at the City University of New York, Queens College will utilize nanoelectrode and nanopipet technologies developed in the Mirkin laboratory to explore the dynamics of charge transfers in thin layer cells and at the interface of two immiscible liquids. These studies are focused on interfacial charge transfer in situations where the system dimensions are smaller than or comparable to the thickness of the electrical double layer?a largely unexplored area of dynamics at interfaces. The research project will also involve the development of nanoelectrode based methods for the characterization of reactive oxygen and nitrogen species generated within living cells. The aforementioned projects will be done in collaboration with US and international scientists (Prof. Shigeru Amemiya at the University of Pittsburgh and Prof. Christian Amatore at the Ecole Normale Superieure, France).
The proposed research is directly relevant to various areas of science and engineering beyond the field of chemistry?from nanoscience and molecular electronics to alternative energy systems and life sciences. The studies of reactive oxygen and nitrogen species in activated macrophages can lead to advances in immunology and contribute to the prevention/treatment of metabolic diseases related to oxidative stress. The graduate students and postdoctoral fellows involved in this project will get multidisciplinary research experience in interfacial electrochemistry, bioanalytical chemistry and nanoscience. They will benefit from extensive national and international collaborations. The results of this research will be broadly disseminated through publications and professional presentations. The requested funds with enable the PI to contribute to ongoing CUNY efforts to recruit underrepresented minority STEM students and participate in its diversity initiatives.
New methodology has been developed to significantly expand the applications of nanometer-sized electrodes and nanopipette-based probes to solving physico-chemical problems and analytical sensing. The combination of nanoelectrochemistry and atomic force microscopy (AFM) imaging enabled controlled nanofabrication of platinized sensors for reactive oxygen and nitrogen species (ROS and RNS). The prepared nanoprobes were used to detect ROS and RNS inside macrophages, which are essential for the performance of the immune system. These experiments supported the hypothesis of the ROS/RNS leakage from phagolysosomes and showed that a macrophage can avoid oxidative damage by rapidly reducing concentration levels of reactive species in its cytoplasm. First measurements of ion-transfer kinetics at the water/ionic liquid interface significantly improved our understanding of these reactions, which are important for separations, sensing and other industrial applications. The experiments employing a new nanoelectrochemical technique—steady-state common ion voltammetry—revealed that these reactions are significantly slower than analogous processes occurring at the water/organic solvent interface. This difference was attributed to higher viscosity of ionic liquids, which can result in lower diffusivities in the interfacial mixed solvent layer. The possibilities of imaging surface reactivity and detecting charged products and intermediates of heterogeneous reactions by the new electron transfer/ion transfer mode of scanning electrochemical microscopy have been demonstrated. This technique offers important advantages, including easy separation of surface topography and reactivity features, sensitive probing of low signal sources, such as living cells, enzymes, or catalyst particles, and very high (≤10 nm) attainable spatial resolution. This project provided opportunities for multidisciplinary research to three graduate students and four postdoctoral fellows. They were trained in electrochemistry, bioanalytical chemistry and nanoscience. These students gave oral and poster presentations at national and international meetings and participated in preparation of research papers. They also visited the laboratories of the collaborators at École Normale Supérieure (France) and Drexel University, and performed joint experiments with their groups. Two students obtained PhD degrees and started postdoctoral studies, and one obtained an M.S. degree. A visiting student from China has been doing research in the PI's laboratory closely related to this project. Two postdoctoral fellows obtained academic positions.
