Excited state properties of 9-amino acridine surface adsorbed onto αZr-phosphate particles.

In this report the photo-physical properties of 9-amino acridine (9AA) associated with αZr-phosphate particles (αZrP) is examined. In ethanol solution 9AA exhibits absorption maxima at 425 nm, 402 nm and 383 nm as well as emission bands centered at 455 nm and 483 nm (using 423 nm excitation). The corresponding emission decay is monophasic with a lifetime of 16.5 ns. When αZrP is sonicated in the presence of an ethanol solution of 1 mM 9AA the resulting material exhibits a broad absorption band centered at ∼400 nm with shoulders at ∼425 nm and ∼385 nm and emission bands at 462 nm and 485nm (using 423 nm excitation). Interestingly, the emission decay is biphasic with lifetimes of 1.6 ns and 9.8 ns constituting 57% and 43% of the total emission intensity, respectively. The absence of any shifts in the low angle XRD data suggests that 9AA associates via adsorption onto the exterior surfaces of the αZrP particles. Overall, these results are consistent with different modes of 9AA association to αZrP reflecting different degrees of H-bonding which significantly influences the extent of non-radiative decay from the lowest excited singlet state of 9AA.