Polyhedron engineering by chemical unit co-substitution in LaAlO3:0.02Pb2+ to generate multimode and condition-sensitive luminescence for dynamic anticounterfeiting

Currently, optical responses, including photo-stimulated luminescence, thermo-luminescence, and persistent luminescence have been revealed to provide advanced security in the field of anti-counterfeiting technology. However, developing optical materials with multi-modal optical outputs is scarce but urgent. Here, a series of multimode luminescent materials of LaAlO3:0.02Pb2+ were synthesized successfully via chemical unit co-substitution, with Li+-Ta5+, Ba2+-Ge4+ and Y3+-Sc3+ substituting for La3+-Al3+. The co-substitution makes the Pb2+ ions be located in two kinds of different crystal environments, mainly due to the differences in bond length of Pb-O and geometry of PbO12, which are related to the changes in centroid shift, Stokes shift and crystal field splitting of Pb2+. Therefore, co-doping Li+-Ta5+, Ba2+-Ge4+ and Y3+-Sc3+ results in new emissions at 410 nm, 320 nm and 420 nm, respectively, along with the intrinsic emission of Pb2+ at 460 nm. Because of the increased deep traps, co-doping Li+-Ta5+, Ba2+-Ge4+ and Y3+-Sc3+ also enhances the NIR emission, which is related to the defect-related luminescent center of VO··-PbLa′ Meanwhile, the prepared samples show various colors at different temperatures, due to the varied thermal quenching of Pb2+ emissions and the NIR emission. The prepared phosphors exhibited dynamical and multimode luminescence, and they outputted inimitable and advanced signals for optical anticounterfeiting, indicating that they are the potential materials for anticounterfeiting technology.