Lanthanide-doped Na₂MgScF₇ exhibiting downshifting and upconversion emissions for multicolor anti-counterfeiting

Abstract

Na2MgScF7 (NMSF) was experimentally obtained for the first time by combining hydrothermal and high-temperature solid-state reactions. X-ray powder diffraction (XRD) combined with Rietveld refinement confirm that NMSF is crystallized in...

Site occupation and upconversion process enabled multicolor emission in a Gd3GaO6:Bi3+,Er3+ phosphor for quad-mode anti-counterfeiting

“…It is worth mentioning that four distinguishable luminescence pictures can be obtained with just one phosphor under four different excitation wavelengths, which does not require a delicate core/shell structure, 7 a complicated lifetime measurement set-up, 13 or multiple kinds of similar phosphors. 8 These luminescent materials, which include both UC luminescence and DS luminescence, provide a high level of security and have the potential to further enhance the current anti-counterfeiting technology based on photoluminescence in society.…”

“…6 The reliability of anti-counterfeiting is largely dependent on the performance of the added luminescent materials. The materials with multicolor emission, either the excitation orthogonalized emissions 7,8 or different emissions in the localized parts of a single microcrystal, 9,10 can offer highly distinguishable patterns for multi-mode anti-counterfeiting with a higher security level. 11 Compared with other types of luminescent materials such as organic dyes, quantum dots and metal complexes, iondoped inorganic materials offer a distinct advantage of readily realizing multicolor emission.…”

“…14,15 For example, the downshifting (DS) emission in some phosphors can be adjusted from reddish to greenish through changing the dopant from Eu 3+ to Tb 3+ ions. 8 In order to construct multi-mode anti-counterfeiting materials, it is usually necessary to synthesize several phosphors with different colors separately. It is more convenient and practical to realize multicolor emissions in just one luminescent material.…”

“…[20][21][22] In some UC processes, the excitation can effectively control the emission. 8 Therefore, we reason that the combination of the DS emission from Bi 3+ and the UC emission from lanthanide ions, such as Er 3+ , can potentially achieve multi-mode anti-counterfeiting in a single phosphor.…”

“…6 The reliability of anti-counterfeiting is largely dependent on the performance of the added luminescent materials. The materials with multicolor emission, either the excitation orthogonalized emissions 7,8 or different emissions in the localized parts of a single microcrystal, 9,10 can offer highly distinguishable patterns for multi-mode anti-counterfeiting with a higher security level. 11…”