Multimodal and Multicolor Anti-counterfeiting Realized in CaCd₂Ga₂Ge₃O₁₂ with a Single Activator of Mn²⁺

Abstract

The continuously growing significance of information security and authentication has put forward many new requirements and challenges for modern luminescent materials and anti-counterfeiting technologies. Recently, luminescent materials have attracted much attention in this field owing to their legibility, repeatability, multicolor, and multiple stimuli-responsive nature. In this work, the efficient multicolor and multimodal luminescence material CaCd2Ga2Ge3O12:Mn2+ was successfully designed and synthesized using the strategy of single-doped Mn2+ in a single matrix. Also, we combined the morphology, crystal structure, energy band calculation, luminescence properties, and trap analysis to study the optical data storage capacity of CaCd2Ga2Ge3O12:Mn2+. Interestingly, in the presence of the 254 nm UV lamp, the sample can exhibit a tunable emission color from bule to cyan to yellow by increasing the dopant concentration of Mn2+. Also, under the afterglow and thermoluminescence luminescence modes, it presented strong yellow emission centered at 558 nm. Based on the advantage of multiple tunable luminescence, samples were made into anti-counterfeiting ink and were used to print four optical devices through the screen printing technology. The results show that the material has excellent multicolor anti-counterfeiting properties under the three luminescence modes, which has contributed to the development of many kinds of luminescent anti-counterfeiting materials for security purposes.

Investigation on the luminescence properties and mechanism of a novel Pr3+-based red persistent luminescence phosphor Cd3Ga2Ge3O12:Pr3+

“…29–31 Notably, the radii difference percentage allowance between the doped and substituted ions must be within 30% according to a report by Davolos. 32,33 Meanwhile, the radii difference percentage can be calculated approximately using the following equation:where R m (CN) and R d (CN) represent the radii of the host cation and the doped ion, respectively. Based on Cd 2+ ( r = 1.1 Å, CN = 8), Ga1 3+ ( r = 0.62 Å, CN = 6), Ga2 3+ ( r = 0.47 Å, CN = 4), Ge1 4+ ( r = 0.53 Å, CN = 6), Ge2 4+ ( r = 0.39 Å, CN = 4), Pr 3+ ( r = 1.126 Å, CN = 8), the Dr between Pr 3+ and the host cations are −2.36%, −81.61%, −139.57%, −112.45% and −188.72% for Cd 2+ , Ga1 3+ , Ga2 3+ , Ge1 4+ and Ge2 4+ , respectively.…”

“…4(c) depicts the corresponding HRTEM image, in which the d-spacing corresponding to (420) of CGGO: 0.0015Pr 3+ is calculated to be 0.271 nm. 32,35 As shown in Fig. 4(d-i), the CGGO:0.0015Pr 3+ sample contains five elements of Cd, O, Ge, Pr, and Ga, which are all uniformly distributed in the particles.…”

“…[29][30][31] Notably, the radii difference percentage allowance between the doped and substituted ions must be within 30% according to a report by Davolos. 32,33 Meanwhile, the radii difference percentage can be calculated approximately using the following equation:…”

Insights into blue-light activated red-emitting persistent luminescence from Pr3+-doped phosphors

“…11,22,25,32,33 It is to be noted that the radii difference percentage allowance between the doped and substituted ions must be within 30% according to the report of Davolos. 21,34 Moreover, we can calculate the radii difference percentage using the following equation:where R m (CN) and R d (CN) represent the radii of the host cation and the doped ion, respectively. Considering Ca 2+ ( r = 1.12 Å, CN = 8), Cd 2+ ( r = 1.1 Å, CN = 8), Ga1 3+ ( r = 0.62 Å, CN = 6), Ga2 3+ ( r = 0.47 Å, CN = 4), Ge1 4+ ( r = 0.53 Å, CN = 6), Ge2 4+ ( r = 0.39 Å, CN = 4), and Pr 3+ ( r = 1.126 Å, CN = 8), the D r between Pr 3+ and the host cations are −0.54%, −2.36%, −81.61%, −139.57%, −112.45% and −188.72% for Ca 2+ , Cd 2+ , Ga1 3+ , Ga2 3+ , Ge1 4+ and Ge2 4+ , respectively.…”

“…20 And the matrix has an adjustable band gap and abundant defect energy levels, which is conducive to the realization of super strong afterglow. 11,21 Furthermore, host materials with an excellent garnet structure have a stable lattice and have attracted considerable attention. 4,22–24 Pr 3+ is a prominent and excellent activator and can exhibit a strong red emission band at 613 nm attributed to the 1 D 2 → 3 H 4 transition of the Pr 3+ ion.…”