Research

My research interest is in the electrochemical characterization of chemical process or materials in mesoscopic dimension (dimension varies from 10 to 1000nm). A wide variety of phenomena are studied including charge-transfer reactions at the solid/liquid, liquid/liquid interfaces, intracellular and extracellular bioelectrochemistry, and cell imaging. The goal of our research is the development of electrochemical sensing strategies with ultrahigh sensitivity and very few sample solutions, and application of these nanosensors for today’s clinical diagnosis and bioelectrochemistry research.

My approach to these topics involves the using of Scanning Electrochemical Microscopy (SECM) and nanoprobes. SECM combines the capabilities of microelectrode electrochemistry with those of Scanning Probe Microscopies, such as STM.  SECM can provide spatially resolved information about local chemical properties of various surfaces. A nanoprobe can be a nano-glass pipet or a nano-metal electrode (Pt, Au etc). Nano metal electrodes could be fabricated into different kinds of shapes to satisfy different kinds of needs. For example, the nanoelectrode in figure1a is robust, thus, it could be used in the study of reaction at liquid/solid interface. Figure 1b shows a nanoelectrode with a very small RG, thus, it is appropriate to be used in surface rastering. Figure 1c shows a needle like nanoelectrode, thus, it could be used to penetrate the biological cell and study local electrochemical reaction. Before use, a nanoelectrode must be polished under video-microscopic control.  Polishing is essential for making reproducible, quantitative measurements on the nanoscale. A polished and relatively large disk-nanoelectrode (metal core radius, 300 nm; RG=6) can be visualized by optical microscopy, figure 1d.

Basically, my research can be divided into two interdependent projects.

In the first projects, I try to understand three kinds of phenomena; (1) Kinetics of charge transfer at liquid/solid interfaces or interfaces between two soft materials (IBTSM). Studying this phenomenon will provide us more knowledge about molecular reorganization and improve the understanding of their response properties. (2) Electrochemical behaviors of few or single molecule, properties of electrochemical catalysis of single enzyme or single particles. The understanding of this phenomenon is helpful in the development of electrochemical sensing strategies with ultrahigh sensitivity. (3) Electrochemical reactions in very small volume (less than 1femtoliters). Compare to electrochemical reactions in a bulk solution, new phenomena may appear, and this will help me with the understanding of how volume affects reactions.

The second projects is motivated by the finding that biological membranes contain lipid mesoscopic-domains or “rafts”, and this kind of region may be involved in processes such as cellular signaling and protein trafficking. We try to use a high resolution image obtained by using SECM with a nanosensor probe to interpret this phenomenon. Another concern of my research is to “see” reactions happening in the living cell, we use a nanopipette to deliver biomolecules through the tip of the pipette, which triggers a cascade of cell signaling events, then, the nanoprobe of the SECM will be inserted into the cell to sense these events. This will allow the study of complex signaling networks with high spatial and temporal resolution.

  

Figure1 Tips used in nanoelectrochemistry studies