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

Abstract 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 Pb^2+. This simple approach towards B‐NC synthesis and its stabilization can contribute to application of this material in LEDs, bioimaging, and energy transfer.