Dye aggregation identified by vibrational coupling using 2D IR spectroscopy

TitleDye aggregation identified by vibrational coupling using 2D IR spectroscopy
Publication TypeJournal Article
Year of Publication2015
AuthorsOudenhoven TA, Joo Y, Laaser JE, Gopalan P, Zanni M T.
Secondary TitleThe Journal of Chemical Physics
Date Published05/2015
PublisherThe Journal of Chemical Physics

We report that a model dye, Re(CO)3(bypy)CO2H, aggregates into clusters on TiO2nanoparticles regardless of our preparation conditions. Using two-dimensional infrared (2D IR) spectroscopy, we have identified characteristic frequencies of monomers, dimers, and trimers. A comparison of 2D IR spectra in solution versus those deposited on TiO2 shows that the propensity to dimerize in solution leads to higher dimer formation on TiO2, but that dimers are formed even if there are only monomers in solution. Aggregates cannot be washed off with standard protocols and are present even at submonolayer coverages. We observe cross peaks between aggregates of different sizes, primarily dimers and trimers, indicating that clusters consist of microdomains in close proximity. 2D IR spectroscopy is used to draw these conclusions from measurements of vibrational couplings, but if molecules are close enough to be vibrationally coupled, then they are also likely to be electronically coupled, which could altercharge transfer.

Short TitleJ. Chem. Phys.