A pH-Triggered Synthesis of Blue-Emitting Au Nanoclusters and Their Luminescence Enhancement in a Metallohydrogel: Selective Detection of Pb2+ through Luminescence Quenching

The synthesis and stabilization of blue-emitting nanoclusters (Au, Cu or Ag) are very challenging. We have developed a facile, acid-induced protocol to synthesize blue-emitting Au NCs (B-NCs) in aqueous medium at room temperature from green-emitting ones (G-NCs). The rapid quenching of the blue emission was successfully arrested, and in fact enhanced, by the incorporation of the NCs in a bile acid derived metallohydrogel, demonstrating the special effect of the gel medium. The NCs in both solution and gel were characterized in detail using microscopic and photophysical techniques, including a detailed analysis of the excited state relaxation pathway. We have demonstrated that this NC can be switched back to G-NCs reversibly upon the reaction with a base. We have also shown that the B-NC can be efficiently applied towards detection of Pb2+. This simple approach towards B-NC synthesis and its stabilization can contribute to application of this material in LEDs, bioimaging, and energy transfer