Key Takeaways & Executive Findings
- •• PVA-modified Eu3+-doped lanthanum tungstate nanophosphors achieve 99.6% color purity and CIE coordinates (0.6351, 0.3644), making them highly suitable for WLEDs and latent fingerprint detection. • Surface modification with PVA significantly enhances red luminescence at 616 nm by suppressing nonradiative recombination and improving surface passivation. • The optimized nanophosphors exhibit extended luminescence lifetimes and excellent biocompatibility, indicating potential for biomedical applications. • This work provides a facile hydrothermal-assisted solid-state synthesis route for high-performance red-emitting nanophosphors with tunable optical properties via surface engineering.
Abstract
The luminescence behavior of Eu3+-activated lanthanum tungstate nanophosphors exhibiting intense red emission was systematically explored by modifying their surfaces using various agents, including polyvinylpyrrolidone (PVP), cetyltrimethylammonium bromide (CTAB), trisodium citrate (TC), polyvinyl alcohol (PVA), and ethylene glycol (EG). These nanophosphors were synthesized via a facile hydrothermal-assisted solid-state reaction. X-ray diffraction (XRD) analysis confirmed the orthorhombic crystal structure of all the prepared samples. Morphological and size analyses were performed using scanning electron microscopy (SEM) and particle size distribution profiling. High-resolution transmission electron microscopy (HRTEM) complemented by elemental mapping was used to evaluate the particle dimensions and interplanar spacing of the optimized sample. Fourier-transform infrared spectroscopy (FTIR) was used to identify functional groups and assign corresponding vibrational bands. X-ray photoelectron spectroscopy (XPS) provided insights into the elemental composition and binding energies of the optimized nanophosphors. Notably, the PVA-modified sample doped with 14mol% Eu3+ exhibited pronounced red emission at 616 nm, attributed to the 5D0→7F2 electric dipole transition of Eu3+ ions under ultraviolet (UV) excitation. Detailed excitation and emission spectral analyses were performed, with band assignments corresponding to the relevant electronic transitions. Among the surface-treated variants, the PVA-modified nanophosphors demonstrated exceptional color purity of 99.6%, international commission on illumination (CIE) chromaticity coordinates of (0.6351, 0.3644), and a correlated color temperature of 1147 K. These superior optical features are ascribed to the enhanced surface passivation and suppression of nonradiative recombination, facilitated effectively by the PVA surface layer. Lifetime decay analysis across all samples revealed a significantly extended lifetime for the optimized composition, further supporting its superior luminescence efficiency. In addition, evaluation of the biocompatibility of the nanophosphors highlighted their potential for biomedical applications. Overall, these findings emphasize the efficacy of PVA-modified Eu3+-doped lanthanum tungstate nanophosphors as highly efficient red emitters, suitable for application in white light-emitting diodes (WLEDs) and latent fingerprint detection while offering valuable insights into the role of surface modification in tuning the optical properties of nanophosphors.
1. Introduction
The features of nanomaterials doped with rare-earth elements, including their extremely small particle size, high luminescence quantum yield, and photostability, make them indispensable for a wide range of technologies. These advances are also applicable to the unique properties of certain materials known as nanophosphors with bright light-emitting potentials, a subset commonly referred to as fluorescent downshifting phosphors, ranging from lighting applications through the health and biosciences, including omics technologies [1]. Although traditional nitride and sulfide phosphors are widely used, their poor chemical stabilities and sensitivities to moisture make them unsuitable alternatives to organic luminescent probes [2–3]. Because nitride and oxynitride phosphors are mostly good emitters of red luminescence, they are difficult to synthesize using procedures that involve high temperatures for extended periods of time [4].
Oxide-based phosphors, which have higher brightness and environmental stability in that they are resistant to moisture, are one of the most attractive phosphor materials for photonic applications, and they are also relatively free from hazardous toxic elements. They also emit high-purity red light under near-ultraviolet (NUV) excitation [5]. The efficiency of phosphor absorption is strongly dependent on the host matrix and luminescent centers (>5%), particularly molybdat...
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K. Naveen Kumar, L. Vijayalakshmi, P.K. Vishwakarma, Jiseok Lim, Mohammad Rezaul Karim, Ibrahim A. Alnaser, D. Rajesh (2025). Optimization of Eu-doped lanthanum tungstate nanophosphors via surface modification for superior red luminescence and photonic applications. Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报). https://doi.org/10.1007/s12613-025-3212-9
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Frequently Asked Questions
What is the main finding of this study?
The study demonstrates that PVA-modified Eu3+-doped lanthanum tungstate nanophosphors exhibit superior red luminescence with 99.6% color purity, making them highly suitable for photonic applications such as white LEDs and latent fingerprint detection.
How were the nanophosphors synthesized?
The nanophosphors were synthesized via a facile hydrothermal-assisted solid-state reaction, followed by surface modification with various agents including PVP, CTAB, TC, PVA, and EG.
What is the significance of PVA surface modification?
PVA surface modification enhances surface passivation and suppresses nonradiative recombination, leading to significantly improved luminescence efficiency and extended lifetime compared to other surface modifiers.
What are the potential applications of these nanophosphors?
The nanophosphors are suitable for white light-emitting diodes (WLEDs), latent fingerprint detection, and biomedical applications due to their high color purity, biocompatibility, and efficient red emission.
What is the optimal Eu3+ doping concentration?
The optimal doping concentration is 14 mol% Eu3+, which yields the most pronounced red emission at 616 nm under UV excitation.
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