Thiol adsorption on metal oxides: an approach for selective deposition on zinc oxide nanoparticles

We have previously discovered a novel, facile approach to encapsulate ZnO nanorods within thiol complexes. This approach results in a thiol uptake of 30-40% and a 400-500 nm thick thiol-Zn-thiol complex encapsulation layer surrounding ZnO nanorods. By controlling experimental parameters, it is possible to control the thiol deposition, enabling less uptake, which results in a surface monolayer instead of encapsulation. Through this approach, thiol modification of other metal oxide materials, namely TiO2, Al2O3, and MgO, has been attempted. FTIR analysis indicates that thiol adsorption occurs only on ZnO; chemisorption of thiols on other nanoparticles is not evident. Ultrahigh vacuum single crystal adsorption studies demonstrate that ZnO(0001) is also more susceptible to thiol monolayer formation, as evidenced by lack of methanethiol adsorption on TiO2(110) and MgO(0001). These results indicate that the facile thiol modification approach opens a new avenue for surface modification of multi-component metal oxide materials by enabling selective thiol modification of ZnO. This work has potential applicability for creating multiple ligand-functionalized materials, which could be useful for the design of novel multiplexing sensors and photovoltaics.