Research in the Watson group involves the functionalization of inorganic surfaces with molecules and nanoparticles. Our goal is to synthesize materials that undergo efficient photoinduced electron transfer reactions across interfaces. Such materials may have applications in photocatalysis and solar energy conversion. REU students working in our laboratory will focus on materials synthesis, surface chemistry, photoelectrochemistry, and/or spectroscopy. Two possible research projects are outlined below.
Project 1: Photoinduced interfacial electron transfer between nanoparticles.
Semiconductor nanoparticles, or “quantum dots,” may be attractive alternatives to molecular chromophores for light-harvesting applications. We have developed methods for the controlled attachment of quantum dots to wide-bandgap semiconductor nanoparticles via molecular linkers.1,2 Using spectroscopic techniques, we are investigating the influence of structural and compositional factors on the kinetics and efficiency of photoinduced electron transfer within these tethered assemblies. For example, we recently demonstrated that the electron transfer yield varies dramatically with the distance between nanoparticles.3 Ongoing research is probing the influence of the properties of donor and acceptor materials, molecular linkage, and surrounding medium on the interfacial electron transfer reactivity.
Project 2: Sensitization of wide-bandgap semiconductors with chalcogenorhodamine dyes.
In collaboration with Profs. Detty and Autschbach at UB, we are investigating the adsorption of novel organic dyes to metal oxide surfaces. We have demonstrated that the orientation of dyes relative to surfaces, and the nature and extent of their aggregation on surfaces, can be tuned systematically by varying their structure.4 Controlled aggregation leads to broadened absorption spectra and improved interfacial electron transfer yields. Ongoing research is directed towards further increasing the light-harvesting efficiency of dye-functionalized semiconductor films and characterizing the influence of aggregation on the kinetics and efficiency of electron transfer reactions.
References:
(1) Dibbell, R. S.; Soja, G. R.; Hoth, R. M.; Watson, D. F. "Photocatalytic Patterning of Monolayers for the Site-Selective Deposition of Quantum Dots onto TiO2 Surfaces." Langmuir 2007, 23, 3432-3439.
(2) Mann, J. R.; Watson, D. F. "Adsorption of CdSe Nanoparticles to Thiolated TiO2 Surfaces: Influence of Intralayer Disulfide Formation on CdSe Surface Coverage." Langmuir 2007, 23, 10924-10928.
(3) Dibbell, R. S.; Watson, D. F. "Distance-Dependent Electron Transfer in Tethered Assemblies of CdS Quantum Dots and TiO2 Nanoparticles." J. Phys. Chem. C 2009, 113, 3139-1349.
(4) Mann, J. R.; Gannon, M. K.; Fitzgibbons, T. C.; Detty, M. R.; Watson, D. F. "Optimizing the Photocurrent Efficiency of Dye-Sensitized Solar Cells through the Controlled Aggregation of Chalcogenoxanthylium Dyes on Nanocrystalline Titania Films." J. Phys. Chem. C 2008, 112, 13057-13061.