Dual-mode optical thermometry and multilevel anti-counterfeiting based on Er3+/Eu3+ doped Ba5Gd8Zn4O21 phosphors

Designing and manufacturing novel anti-counterfeiting materials with multilevel, strong readability and inexpensive is a crucial challenge. Herein, a batch of Ba5Gd8(1-x-y)Zn4O21:xEu3+/yEr3+ phosphors with long persistent and multicolor luminescence were synthesized. Their structure and luminescence properties were studied through X-ray diffraction, scanning electron microscope, lifetime decay curves, emission, excitation, thermoluminescence and diffuse reflection spectra. Under different wavelengths irradiation, Ba5Gd8Zn4O21:Eu3+, Ba5Gd8Zn4O21:Er3+ and Ba5Gd8Zn4O21:Eu3+, Er3+ emit strong red, green and multicolor (green, yellow, red) luminescence, respectively. Importantly, Ba5Gd8Zn4O21:Eu3+ and Ba5Gd8Zn4O21:Eu3+, Er3+ phosphors exhibit long-lasting luminescence after 254 nm and X-ray radiation. Combine long afterglow and multicolor emissions under X-ray, UV and 980 nm laser excitation, these materials successfully achieve multilevel anti-counterfeiting. In terms of optical temperature measurement, the maximum relative sensitivity of Ba5Gd7.44Zn4O21:0.07Er3+ based on thermal coupling levels (2H11/2/4S3/2) and non-thermal coupling levels (4F9/2/2H11/2) of Er3+ are 1.29 % K−1 and 0.34 % K−1, respectively. Both two modes exhibit superior repeatability (98 %) in 333–573 K temperature range which can realize self-calibration temperature sensing. All findings reveal great potential of these phosphors for multilevel anti-counterfeiting and efficient optical temperature sensing.