Effects of β-mercaptoethanol on quantum dot emission evaluated from photoluminescence decays

β-mercaptoethanol (BME) has been used as an "anti-blinking" reagent with quantum dots (QDs), but its exact effects on the luminescence behavior of different QD materials have not been quantified. In this study, the luminescence lifetime decays of aqueous solutions of CdTe QDs solubilized with mercaptopropionic acid (MPA) are measured by time-correlated single photon counting (TCSPC) in the presence of varying concentrations of BME. The decays are fit to a model of radiative recombination and trapping that yields the respective time constants as well as the coefficient of intermittency (blinking). It is found that low concentrations of BME in its thiol form (neutral pH) lead to decreases in average lifetime but increased or constant quantum yields, indicating a higher fraction of radiative QDs than without BME. Correspondingly, the blinking coefficients are greatly reduced in the presence of BME at neutral pH. Higher concentrations of BME reduce emission by creating hole traps, a process that requires several hours after BME addition to manifest. Lifetimes are also reduced by the thiolate form of BME (basic pH) but to a lesser degree than at neutral pH. Strikingly, the blinking coefficients are almost entirely unchanged with BME addition at basic pH. In deoxygenated solutions, quantum yields are decreased rather than increased with BME, confirming that the enhancement results from BMEs antioxidant effects. These results provide a quantitative approach to studying blinking and trapping dynamics using time-resolved decays.