Photoluminescence lifetime based nickel ion detection by glutathione capped CdTe/CdS core-shell quantum dots

Abstract

Here we have demonstrated a methodology for detecting nickel ions in aqueous medium using photoluminescence (PL) lifetime of the probe made of glutathione capped CdTe/CdS core-shell quantum dots. The ratio of (τavg)probe/(τavg)probe+Ni2+ has been developed as an analytical signal for detecting Ni2+ ions. The plot of (τavg)probe/(τavg)probe+Ni2+ versus concentration of Ni2+ revealed a linear positive slope and the sensitivity was 0.61 L/mg, which is in good agreement with that determined from conventional Stern-Volmer plot (i.e., 0.64 L/mg). The limit of Ni2+ detection was 23 μg/L. The temperature dependent steady state PL quenching, time-resolved PL decay and photocatalytic dye degradation in absence and in presence of Ni2+ suggested that the PL quenching by Ni2+ is due to pure collision based dynamic quenching with favourable electron transfer process. On the other hand, the present method was not applicable for Cu2+ detection as the ratio of (τavg)probe/(τavg)probe+Cu2+ was non-responsive over the given range of Cu2+ concentration. The PL quenching by Cu2+ comprised of a combination of dynamic quenching and due to interaction of Cu2+ with the probe. It has been concluded that ratio of (τavg)probe/(τavg)probe+analyte can be a promising analytical signal for detecting metal ions, particularly for those exhibiting dynamic PL quenching.