Room-temperature synthesis of near-ultraviolet light-excited Tb3+-doped NaBiF4 green-emitting nanoparticles for solid-state lighting

One material, many possibilities via enrichment of luminescence in La2Zr2O7:Tb3+ nanophosphors for forensic stimuli aided applications

Engineering a single material with multidirectional applications is crucial for improving productivity, low cost, flexibility, least power consumption, etc. To achieve these requirements, novel design structures and high-performance materials are in urgent need. Lanthanide-doped nanophosphors have the greatest strengths and ability in order to tune their applications in various dimensions. However, applications of nanophosphor in latent fingerprints visualization, anti-counterfeiting, and luminescent gels/films are still in their infancy. This study demonstrated a simple strategy to enhance the luminescence of Tb³⁺ (1-11 mol %) doped La₂Zr₂O₇ nanophosphors by conjugating various fluxes via a simple solution combustion route. The photoluminescence emission spectra reveal intense peaks at ~ 491, 546, 587, and 622 nm, which arises from ⁵D₄ → ⁷F_J (J = 6, 5, 4, 3) transitions of Tb³⁺ ions, respectively. The highest emission intensity was achieved in the NH₄Cl flux assisted nanophosphor as compared to NaBr and NH₄F assisted samples. The colorimetric images of fingerprints visualized using the optimized nanophosphor on forensic related surfaces exhibit level -III ridge details, including sweat pores, the width of the ridges, bifurcation angle, and the successive distance between sweat pores, etc. These results are decisive parameters that clearly support the statement "no two persons have ever been found to have the same fingerprints". The anti-counterfeiting security ink was formulated using optimized nanophosphor and various patterns were designed by simple screen printing and dip pen technologies. The encoded information was decrypted only under ultraviolet 254 nm light. All the designed patterns are exhibit not just what it looks/feel like and how better it works. As a synergetic contribution of enhanced luminescence of the prepared nanophosphor, the green-emissive films were fabricated, which display excellent flexibility, uniformity, and transparency in the normal and ultraviolet 254 nm light illumination. The aforementioned results revealed that the prepared NH₄Cl flux-assisted La₂Zr₂O₇: Tb³⁺(7 mol %) NPs are considered to be the best candidate for multi-dimensional applications.

Utilizing energy transfer strategy to produce efficient green luminescence in Ca2LuHf2Al3O12:Ce3+,Tb3+ garnet phosphors for high-quality near-UV-pumped warm-white LEDs

White light-emitting diodes (LEDs) are widely used in lighting and display devices, and the exploration of phosphors with excellent luminescence performance and good stability is the key to the development of white LEDs. In this work, we reported novel near-UV-excited green-emitting Ca₂LuHf₂(AlO₄)₃:Ce³⁺,Tb³⁺ garnet phosphors with efficient Ce³⁺ → Tb³⁺ energy transfer. The CLHA:Ce³⁺,Tb³⁺ green phosphors were successfully synthesized by a high-temperature solid-state method, and the phosphors were characterized by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, elemental mapping, photoluminescence excitation and photoluminescence spectra, the Commission International de I'Eclairage (CIE) chromaticity coordinates, quantum efficiency and temperature-dependent emission spectra. Due to the spin-allowed 4f → 5d transition of Ce³⁺ ions, the CLHA:Ce³⁺,Tb³⁺ phosphors exhibited a strong broad excitation band in the 300-470 nm near-ultraviolet (near-UV) range. Under 408 nm excitation, the CLHA:Ce³⁺,Tb³⁺ phosphors showed strong green light with emission center at 543 nm. The mechanism of energy transfer from Ce³⁺ to Tb³⁺ ions was attributed to quadruple-quadruple interaction. Impressively, the internal quantum efficiency and external quantum efficiency of the optimal CLHA:0.02Ce³⁺,0.5Tb³⁺ green phosphors were measured to be 77.1% and 55.8%, respectively. Finally, using the CLHA:0.02Ce³⁺,0.5Tb³⁺ phosphors as green-emitting color converter, a near-UV-pumped white LED device was fabricated, and under 80 mA driving current the LED device demonstrated bright warm-white light with high color rendering index (93.7), low correlated color temperature (3574 K), CIE chromaticity coordinates (0.3922, 0.3633), and high luminous efficacy (29.35 lm/W).

Novel high-efficiency Eu3+-activated Na2Gd2B2O7 red-emitting phosphors with high color purity

Novel high-efficiency Eu³⁺-activated Na₂Gd₂B₂O₇ red-emitting phosphors with color purity as high as 99% were developed for warm white LEDs.