Date Awarded

Spring 2017

Document Type


Degree Name

Master of Science (M.Sc.)




Kristin L Wustholz

Committee Member

Nathan Kidwell

Committee Member

Elizabeth Harbron


The impact of rhodamine aggregates on the photophysical properties of rhodamine dyes adsorbed to TiO2 were investigated using diffuse reflectance spectroscopy, steady-state fluorescence, and time-correlated single photon counting (TCSPC). Photocatalyzed de-alkylation of rhodamine dyes containing tertiary amine groups (5-ROX, R101, and RB) was observed on TiO2, which resulted in a ~50 nm hypsochromic shift. Therefore, concentration dependent diffuse reflectance spectra of R560/TiO2 samples, which contained primary amines, demonstrated the formation of H- and J-aggregates at the expense of the monomers. The formation of J-aggregates resulted in FRET between monomers and J-aggregates which yielded a bathochromic shifted fluorescence spectra as a function of increased dye concentration. Additionally, the J-aggregates were believed to be less fluorescent than the corresponding monomer, which, in addition to the presence of non-fluorescent H-aggregates, led to the quenched fluorescence. Time dependent fluorescent measurements established that electron injection to TiO2 from R560 occurred from both the monomer and J-aggregates, as lifetimes of each species on TiO2 were quenched relative to lifetimes on ZrO2.



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