As you well know, the surface of a material is the first point of contact, be it gases, liquids, or electrical contacts. Consequently, my group is interested in the complex interactions that take place at the surface of nanomaterials. These interactions can affect electrical conductivity, which in turn is the basis of many chemical sensors. We study these effects either electrically (sensors) or by X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). In fact, electrical measurements and spectroscopy analysis are complementary. Case in point, Au-GaN nanowire sensors. Our initial testing of Au-GaN nanowire sensors indicated that water and CO interact very differently with the surface of the sensor, as well with each other if co-adsorbed. Through the use of UPS to study water and CO adsorption on Au-GaN nanowires we have been able to understand the differences between their interactions with the surface of the sensor, as well as with one another. In my humble opinion, the study of the surfaces of nanomaterials is bringing about a renaissance in the field of surface science.
The custom build XPS/UPS system in my laboratory. It has an electron gun to mitigate charging. Samples can be cooled to 15K, or heated to the point of melting.