Solvent/ligand free synthesis of Mn-doped CsPbCl3 perovskites with enhanced fluorescence for color sensor of bromide ions

For the detection of anions from wastewater, the perovskite materials synthesized should have suitable stability and be as hydrophilic as possible, and it's not appropriate to introduce organic ligands. Mechanochemical reaction can avoid the use of organic solvents and provide improved stability for the perovskite materials due to their large particle size and compact structure, but their fluorescence is often too weak. To solve this problem, the Mn2+ doping effect was introduced into the CsPbCl3 crystals, and their synthesis doping strategies driven by mechanical grinding were systematic studied. The optimal Mn2+-doped CsPbCl3 (CsPbCl3:Mn) product was obtained by optimizing the synthesis conditions of Mn2+ source, grinding time on each reaction stage, Mn: Pb feeding ratio, and the sintering temperature. CsPbCl3:Mn had the same crystal structure as its undoped counterpart, while an obvious photoluminescence emission peak at 604 nm was obtained, which was originated from the doped Mn2+ ions. CsPbCl3:Mn had good stability against the ethanol environment and there was no organic ligands to hinder the ion exchange between Cl- and Br- from wastewater. Through testing the color difference of the resultant powders, a linear relationship with high correlation coefficient above 0.99 was established between chroma and Br- concentrations, and the Br- concentration in wastewater was accurately determined, demonstrating a promising application prospect of CsPbCl3:Mn in the fast detection of Br- ions.