Study on the kinetic properties of phosphor in deoxycholate aggregates by phosphorescent quenching methodology

Owing to the unique molecular structure and aggregate behaviors in aqueous solution, dihydroxy bile salts can provide phosphorescent probe with a special microenvironment in which the room temperature phosphorescence of probe can be detected in the presence of dissolved oxygen. It, however, is not very clear how the bile salts work in inducing this kind of oxygen-independent phosphorescence. The present work tries to offer with possible more insights by investigating the particular kinetic behaviors of 3-bromoquinoline (3-BrQ) as probe in sodium deoxycholate (NaDC) aggregate based on phosphorescent quenching methodology. The critical aggregate concentration of NaDC is estimated as about 0.5 mM based on the enhancement of probe phosphorescence. As the functions of quencher Cu2+ and NO2-, the rate constants of various photophysical processes for 3-BrQ are obtained in NaDC solution and full aqueous solution, respectively. In NaDC solution, the quenching rate constant kmqCu2+ equals to 1.77 × 107 M−1 s−1kmqNO2- 1.62 × 106 M−1 s−1. The exit rate k− and entrance rate k+ are determined to be 16–46 s−1 and 106 M−1 s−1 levels, respectively. The quenching rate constant kqO2 of dissolved oxygen is estimated as 4.15 × 104 M−1 s−1 in air-saturated NaDC solution at 1 atm.