High-level anti-counterfeiting using a Dy3+ single-activated germanate afterglow phosphor with color-tunable luminescence and multi-mode reading

Abstract

Development of luminescent materials has aroused substantial attention, especially in the advanced anti-counterfeiting field involving high-security information encryption and storage. However, the preparation of tunable multicolor luminescence and multi-mode reading materials is currently limited by complex and expensive synthetic processes involving physical mixing and multiple luminescence center-regulated and complex structure design, restricting practical application for multilevel information encryption. Herein, a single Dy³⁺ is incorporated into a single-host CaCdGe₇O₁₆ material via a high-temperature solid-phase reaction, yielding a series of color-tunable luminescence (cyan, red, white and yellow) and multi-mode reading (photoluminescence, long afterglow and thermoluminescence) afterglow CaCdGe₇O₁₆:xDy³⁺ (x = 0, 0.002, 0.006, 0.01, and 0.014) phosphors. By adjusting the Dy³⁺ doping concentration, the powder initially exhibited a cyan emission under 254 nm irradiation, followed by a red to white emission when the UV lamp was turned off. Color variations in the CaCdGe₇O₁₆:xDy³⁺ (x = 0, 0.002, 0.006, 0.01, and 0.014) afterglow turned from a characteristic emission of the host to characteristic emission of Dy³⁺ with increased Dy³⁺ content. Moreover, in thermoluminescence mode, a color-tunable emission from red to yellow was realized. Advanced anti-counterfeiting labels were fabricated based on the color-tunable luminescence and multi-mode reading properties of CaCdGe₇O₁₆:xDy³⁺ (x = 0, 0.002, 0.006, 0.01, and 0.014) phosphors, greatly improving the security of the encrypted information. The study provides fresh perspectives on the development of advanced anti-counterfeiting and information encryption strategies.