Manganese halides with timely and delayed reversible thermal fluorescence quenching for dual-secure information encryption and anti-counterfeiting

Mn (II)−based hybrid metal halides have become a promising class of optoelectronic materials due to their non-toxic, diverse molecular coordination, efficient photoluminescence and tunable emission wavelength. Three novel manganese halides TAMn₂Cl₅·2H₂O, TA₂MnBr₄ and TMG₂MnBr₄ (TA = triethylamine, TMG = 1,1,3,3-tetramethylguanidine) were successfully prepared, exhibiting bright green light emission with the max emission at 525, 525 and 527 nm, with the photoluminescence quantum yields (PLQY) of 11.64 %, 89.61 % and 90.02 %, respectively. TAMn₂Cl₅·2H₂O and TA₂MnBr₄ exhibit delayed and timely quenching of thermal fluorescence and recovery of green light emission, while TMG₂MnBr₄ shows thermally stable green luminescence. TA₂MnBr₄ and TMG₂MnBr₄ were used to achieve timely information encryption and anti-counterfeiting. The pairing combinations of TAMn₂Cl₅·2H₂O, TA₂MnBr₄ and TMG₂MnBr₄ achieved dual-secure encryption and anti-counterfeiting of information. This work demonstrates the potential applications of Mn (II)-based metal halides in the fields of information encryption and anti-counterfeiting.