Doping Pb2+ in LaAlO3 to generate dual emission centers and an optical storage container for visible and near infrared persistent luminescence

Abstract

Defects play an important role in luminescence, not only as non-radiative transition centers to decrease the luminescence intensity, but also as useful centers for improving luminescence. Phosphors with unique characteristics can be designed by using effective defects combined with the luminescence center. Here, a novel phosphor of LaAlO₃:Pb²⁺ was synthesized by a solid state reaction. Two kinds of defects, which are and Pb′_La, were constructed by incorporation of Pb²⁺ into LaAlO₃. Under UV excitation at 285 nm, the sample outputted a broad cyan emission at 460 nm that is related to the ³P₁–¹S₀ transition of Pb²⁺, along with a weak near infrared (NIR) emission at 735 nm. However, only NIR emission at 735 nm can be found upon 211 nm excitation. The defect levels of and Pb′_La in the band gap are evidenced to be the contributor for the NIR output. Heating the sample resulted in a weakened cyan emission and an enhanced NIR output. Because the defects of and Pb′_La also act as the electron and hole traps, the sample outputted cyan and NIR afterglows after removing the irradiation source. Since the optical signal of LaAlO₃:Pb²⁺ is sensitive to the excitation wavelength, temperature, and duration time, the multimodal luminescent phosphor may be used as a potential anti-counterfeiting material.