Mn-doped CsPbCl perovskite quantum dots: A dual-function probe for copper detection and temperature sensing.

The low photoluminescence quantum yield (PLQY) of CsPbCl perovskite quantum dots (PQDs) poses a significant challenge to their application as ion detection probes. To address this issue, we enhanced the PLQY of CsPbCl PQDs through Mn doping. These enhanced PQDs were then employed as probes for the highly sensitive detection of Cu ions and temperature. CsPbCl:Mn PQDs with varying Mn/Pb ratios were synthesized via hot injection. The Mn doping introduced an emission band near 600 nm, with intensity increasing alongside doping concentration. At an Mn/Pb ratio of 2.0, the PLQY was enhanced nearly tenfold, from 5.46 % for undoped CsPbCl to 52.48 % for CsPbCl:Mn. CsPbCl:Mn PQDs with the highest PLQY were employed as luminescent probes, utilizing the fluorescence intensity ratio (FIR) technique for copper detection and temperature sensing. The experimental results demonstrated a linear relationship between the FIR and Cu concentration over the range of 22.12 nM-1600 nM, with 22.12 nM being the calculated limit of detection. Analysis of the emission spectra and fluorescence lifetimes at varying Cu concentrations revealed that electron transfer from CsPbCl to Cu induced fluorescence quenching. CsPbCl:Mn exhibits a high relative sensitivity of 15.89 % K at 298 K, along with excellent reversibility. These findings highlight the potential application of CsPbCl:Mn PQDs in both temperature sensing and the analysis of wear metals in engine lubricating oils.