The study introduces dual-mode orthovanadates as a viable substitute for fluoride-based materials in the realm of anti-counterfeiting tags. All of above-mentioned features of the GdVO 4: Yb 3+, Tm 3+, Eu 3+ phosphors synthesized by the feasible hydrothermal approach, designate as perfect for the anti-counterfeiting applications as the color tunability within the same material is difficult to falsify. In this study, we aim to provide a comprehensive understanding of the properties and applications of the luminescent marks based on doped orthovanadates. Also, under UV irradiation, there is a possibility of direct Eu 3+ excitation or energy transfer from the orthovanadate matrix to dopant ions-in both cases, a red emission associated with Eu 3+ is observed 22, 23. Here, the NIR excitation of 980 nm can be absorbed by Yb 3+ and after transferring two or more photons towards Tm 3+ and Eu 3+ ions, a visible up-conversion emission is observed, which is highly dependent on Tm 3+ and Eu 3+ ratio. The perfect combination for obtaining tunable luminescence is the system comprising Yb 3+, Tm 3+, and Eu 3+ ions. When a combination of ions capable of absorbing energy with diverse energy values based on their electron structure is used, a unique luminescence color tunability can be achieved. Rare earth-doped materials exhibiting dual-mode luminescence possess vast potential for various applications 18, 19, 20, 21. In comparison to the vanadate materials, commonly used in phosphor applications fluoride materials are not only sensitive to high temperatures but also to surface contamination which may accidentally influence spectroscopic properties such as luminescence lifetime or emission color 17.Ĭontrary to the accidental influence, the intentional impact on the intensity and different luminescence color under UV or NIR excitation is caused by the specified Ln 3+ dopant concentration. light-emitting diode application, in which operating temperature exceeds 100 ☌ 16. Another advantage of vanadate-based phosphors as an alternative type of material versus fluoride-based phosphors is their high thermal stability, beneficial in i.e.
In our research, we chose GdVO 4-based dual-mode phosphors based on their strong energy absorption as well as the high efficiency of energy transfer processes 13, 14, 15. Also, during this rigorous process of fibers preparation, the luminescent modifier used has to outstand with its excellent stability. As an outcome, the so-called Tencel fibers may be used for paper modification or as a part of the fabric. Recently developed cellulose fibers modified- with inorganic phosphors 8, 9, 10, 11, 12 are prepared via an environmentally friendly NMMO (N-Methylmorpholine-N-Oxide) method. Every aforementioned security approach has its limitations and thus cannot be applied in i.e., clothes or document markings, which may be regularly treated with water, washing agents, or UV radiation. The last-mentioned group consists of several media in which anti-counterfeiting tags are implemented, such as bar codes, inks, holograms, RFID (Radio Frequency Identification). Inorganic materials doped with lanthanide ions (Ln 3+) play a significant role in many fields of everyday life, based on their numerous applications as lasers, thin film phosphors, in drug delivery, bioimaging, or anti-counterfeiting 1, 2, 3, 4, 5, 6, 7. Moreover, the GdVO 4: 20% Yb 3+, 0.5% Tm 3+, 5% Eu 3+ showed the most outstanding color tunability from red color (x = 0.6338, y = 0.3172) under UV to blue color (x = 0.2640, y = 0.1988) under NIR excitation, which can be applied in anti-counterfeiting activity. For Yb 3+, Tm 3+, and Eu 3+- codoped phosphors we observed bands related to the 1G 4 → 3H 6 and 1G 4 → 3F 4 transitions of Tm 3+ ions, occurred through the cooperative up-conversion mechanism, where two nearby Yb 3+ ions were involved in near-infrared absorption.
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Detailed spectroscopy analysis revealed tunable luminescence properties with an increasing Yb 3+ content in series of GdVO 4: x% Yb 3+, y% Tm 3+, 5% Eu 3+ (x = 5, 10, 15, 20 y = 0.1, 0.5, 1) phosphors.
The morphology of yielded phosphors was confirmed by transmission electron microscopy and scanning electron microscopy. The X-ray diffraction analysis determined the tetragonal structure as well as I4 1 /amd space group of products by comparing with a reference pattern no. GdVO 4-based dual-mode phosphors were successfully synthesized via a hydrothermal approach.
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