Low-Dimension Nanomaterials
     We are working on the synthesis and characterization of low-dimensional nanomaterials such as nanoparticles, nanowires, nanotubes and thin films. We strive to synthesize such nanomaterials with controllable size, shape and structure by sol-gel, hydrothermal processing and other wet chemical processing, as well as chemical vapor deposition. For example, we control the crystal growth through molecular recognition. We are investigating the size-dependent properties of nanomaterials. We attempt to utilize the nanomaterials to build solar devices, fuel cells and sensors.

Nano-array Patterns and Nano-architectures
     Large-area-ordered two dimensional (2D) or 3D nanopatterns have extensive applications in photonic devices, biosensors, catalysts and high-density magnetic recording devices. Future sucess of 2D/3D nanopatterns depends on the availability of cost-effective, scale-up patterning methods. Commomly used patterning techniques such as photolithography, electron beam lithography, and focused ion beam (FIB) lithography have limitation in fabrication of 2D/3D nanostructures. It is very difficult for the photolithography method to generate the features less than 100 nm. The e-beam and FIB techniques are limited by their low throughput in creating large-area nanoscale patterns. We strive to develop a facile approach for cost-effective, high throughput fabrication of large-area nanoscale patterns. For example, we are developing large-area nano-array patterns by nanosphere lithography.

Chemical Sensors and Biosensors
     Chemical sensors and biosensors attract increasing attention. It remains a challenge to improve the performance of sensors in terms of selectivity, sensitivity, response time, and reliability. We strive to utilize nanotechnology and nanomaterials to fabricate high-performance chemical sensors and biosensors. One of our goals is to make nanostructured sensors to detect trace chemical species or even single biological molecules. We attempt to achieve small size, easy integration into devices, and low cost. Our current work is focused on electrochemical sensors and surface plasmon resonance (SPR)-enhanced fluorescent sensors and SPR-enhanced Raman sensors, which are used to detect anticancer drugs, proteins, pathogens and heavy metals.
     Understanding the inherent sensing mechanism and the chemical and physical process involved in sensing is the prerequisite for design of sensors. It is necessary to perform in parallel the classical electrochemical, the catalytic and surface analytical studies on sensors. In particular, we are performing an in-situ study on single molecular events, local electric and ionic transport in sensors on the nanoascale under the sensing environment. We are exploring the correlation of the sensing properties with the crystal structure, the chemical structure and the electronic structure of materials. We are also studying the interaction of chemical species with the surface of sensing materials.

Photocatalysts and Photoelectrochemical Cells
     Photocatalysis generally involves three processes: (i) generation of electrons and holes by photoexcitation; (ii) migration of the photogenerated charge carriers to the surface and subsequent reduction/oxidization of the adsorbed reactants directly by electrons/holes or by reactive oxygen species (ROS); and (iii) recombination of the photogenerated electron-hole pairs. Desired photocatalysts are expected to promote Process (i) and (ii) in the meanwhile to suppress Process (iii). We attempt to gain fundamental understanding of the effects of the chemical composition, electronic structure, crystal structure and morphology of nanocrystals on the three processes in photocatalysis. We are developing new materials and/or optimize the shape and surface structure of nanocrystals to improve the efficiency of photocatalysis and photoelectrochemical processes.

We are developing photocatalysts and photoelectrochemical cells for solar energy utilization and environmental remediation. Currently, the primary energy source is supplied by fossil fuels. It is essential to increase the energy conversion/utilization efficiency and to reduce the pollutant emission of power generation. Photocatalysts and photoelectrochemical cells are emerging as a potential CO2 capture technologies. Photocatalytic conversion of CO2 not only removes CO2 from effluent gases but it also converts CO2 into marketable commodity such as methane, methanol, and formaldehyde. In addition, photoelectrochemical cells are used to produce H2 from coal. By harnessing solar energy, the H2 generation process is less energy-consuming than the conventional methods. Also, H2 generation by photoelectrochemical cells will significantly reduce the release of pollutants to the ecological system.      We are exploring to mitigate or remove the environmental pollutants such as heavy metals, small molecule toxins and pathogens by utilizing photocatalysts and photoelectrochemical cells.

Solid Oxide Fuel Cells
     Conventional solid oxide fuel cells (SOFCs) use yttria-stabilized zirconia (YSZ) electrolyte. However, its conductivity characteristics require an operating temperature of over 900°C. Reduction of the operating temperature of SOFCs to <800°C is one of the main goals of current SOFC research programs. The challenge is that the electrochemical reaction becomes considerably slower as temperature is reduced. Due to the high activation energy of the oxygen reduction reaction, whose polarization resistance increases rapidly with decreasing temperature, the cathode requires particular attention when the operating temperature is reduced. The cathode performance depends on the electronic/ionic conductivity of the electrode, gas transport through electrode porosity, and the electrocatalytic activity at the three-phase boundary (TPB) areas among the gas, the electrolyte and the cathodes. We strive to improve the cathode performance by developing new materials and/or optimization of electrode architecture/microstructure.
     In addition, we are investigating the effects of trace impurities on the performance of SOFC anodes that are operated in coal-derived syngas. We are identifying the elements that have the most detrimental effects. We seek to establish the fundamental mechanism of the interaction of impurities with the anode by electrochemical studies and microstructural analysis. The knowledge obtained will lead to maximization of the power density of SOFC and improvement of the reliability of SOFC anode operated in the syngas environment. This work is part of the DOE-funded project of “Direct Utilization of Coal Syngas in High Temperature Fuel Cells” that is implemented by an interdisciplinary research team of WVU.