Investigation of the Fluorescence Quenching of 1-Aminoanthracene by Dissolved Oxygen in Cyclohexane

This study provides a detailed investigation of the fluorescence quenching mechanisms of the fluorophore, 1-aminoanthracene, by dissolved oxygen in cyclohexane. Dynamic/collisional quenching dominates in the system studied, but there is also a small component of static quenching. Stern-Volmer plots revealed that the dynamic quenching constant is 0.445 +/- 0.014 mM(-1) and represents similar to 95% of total quenching in the system. The static quenching rate constant is 0.024 +/- 0.001 mM(-1), and mechanisms by complex formation and sphere of action static quenching were examined. Compensation of steady-state fluorescence data for solvent loss during the gradual deoxygenation period of the experiment was found to be important in order to conduct a thorough evaluation of the different quenching mechanisms of the system. The enhancement factors, (F-o/F) and (tau(o)/tau), for 1-aminoanthracene were determined to be 2.20 +/- 0.01 and 2.08 +/- 0.01, respectively, and the diffusion-controlled bimolecular rate constant was found to be 2.1 x 10 (10) +/- 0.2 x 10 (10) M-1 s(-1). The work involved the development of a novel instrumental setup that simultaneously measures several important spectroscopic parameters (steady-state fluorescence intensity, absorbance, fluorescence lifetime, and dissolved oxygen concentration) for the careful study of oxygen quenching mechanisms of 1-aminoanthracene in a cyclohexane solution.