Neutralizing the Charge Imbalance Problem in Eu3+-Activated BaAl2O4 Nanophosphors: Theoretical Insights and Experimental Validation Considering K+ Codoping

Tailoring the structural and electro-optical properties of avisible-light emitting BaZrO3 photocatalyst: integrating DFT and comprehensive experimental analysis

In the present work, the synthesis of BaZrO3 nano-ceramics is explored through flash combustion utilizing glycine as a fuel. The resulting nanoparticles exhibit a cubic Pm3̄m space group and a spherical morphology with an average size of 45.31 nm. XRD and EDAX verify the integrity of the phase. FTIR and Raman spectroscopy is used to analyze the molecular bonds and their vibrations, while XPS reveals surface compositions and oxidation states. The electro-optical properties of BaZrO3 are explored through UV-Vis spectroscopy and electronic band structure analysis. The Tauc plot displays a pair of band gaps, with values of 3.08 eV and 3.84 eV, corresponding to indirect and direct characteristics. BaZrO3 demonstrates photocatalytic potential with a degradation efficiency of approximately 36.41% for rhodamine B under visible light. Electronic band structure analysis reveals an indirect band gap of 3.05 eV in BaZrO3. The Bader analysis emphasizes the pronounced covalent characteristics present in the Zr-O bond. Photoluminescence spectra exhibit electronic transitions with a peak observed at 420.57 nm (∼2.94 eV), suggesting activity within the violet light spectrum. The CIE chromaticity coordinates imply prospective uses in the manufacture of violet-blue LEDs. These findings underscore the tailored properties of BaZrO3 nano-ceramics, showcasing their versatility for various applications, notably in advanced optoelectronic devices.

Luminescence Dynamics of BaAl2O4:Eu2+ Phosphor

We studied steady-state and time-resolved photoluminescence of Eu doped BaAl2O4 phosphor. The undoped BaAl2O4 sample shows a dominant blue emission band at ~ 428 nm and two secondary maxima at ~ 405 and 456 nm due to F-centre and aggregate defects such as F2 -centre. The samples after doping of Eu at 1-5% show additional emission bands at ~ 485 and 518 nm due to Eu2+ centre and a red emission band at ~ 657 nm is attributed to Eu3+ centre. The sample doped with 2% of Eu shows anomalous emission having the dominant peak at ~ 494 nm. The average luminescence lifetime of the emission band at ~ 428 nm in the undoped sample was estimated to be (3.29 ± 0.91) ns. The average luminescence lifetime of this emission band after doping of Eu was found to increase by 102 orders of magnitude. The intensity of the 428 nm blue emission band was found to quench after doping of Eu beyond 3%. The concentration quenching effect was attributed to dipole-quadrupole interaction. Further, a non-radiative fluorescence energy transfer mechanism from an extrinsic Eu2+ centre to an intrinsic F-centre is proposed to describe the luminescence dynamics of the samples.

Photocatalytic Activity of BaAl2O4 for Water Purification

Degradation of dyes under natural light sources is one of the most active research areas in basic science for greener technology. In this context, the photocatalytic activity of semiconductors has received massive attention in solving water treatment-related issues as these possess enormous potential for degrading organic impurities. Here, we report that barium aluminate (BaAl2O4, BAO), which has been extensively studied for photoluminescence applications, is found to be a highly potent candidate for photocatalytic activities. We have explored the degradation of dyes (meant for water purification) by using the photocatalytic properties of pure and Dy- and Yb-codoped BAO. Crystal structure, electron microscopy, and Raman analysis of the autocombustion-synthesized pure and codoped BAO samples revealed significant morphological changes such as increased particle size and stabilization of rod-like structures. UV-vis absorbance measurements confirm the presence of multiple bandgaps in the BAO samples, which is substantiated by X-ray absorption spectroscopy measurements. Photocatalytic degradation studies of methylene blue (MB) dye (with different catalyst concentrations, dopings, and MB dye concentrations) have been carried out by using BAO. The kinetics of the photocatalytic degradation measurements has been explained by the Boltzmann distribution function, and the fastest (in less than 40 min), with more than 99% degradation of MB impurity, is reported here for the first time in BAO compounds. Synthesized BAO samples show excellent cyclic stability, which is essential for their potential applications in environmental remediation. The trade-off between the enhancement of surface area and increased particle size is considered the key parameter for controlling the photocatalytic performance of the BAO catalyst after Dy and Yb codopings.

An Ultrafast and Room-Temperature Strategy for Kilogram-Scale Synthesis of Sub-5 nm Eu3+ -doped CaMO4 Nanocrystals with a Photoluminescence Quantum Yield Exceeding 85

Rare earth-doped metal oxide nanocrystals have a high potential in display, lighting, and bio-imaging, owing to their excellent emission efficiency, superior chemical, and thermal stability. However, the photoluminescence quantum yields (PLQYs) of rare earth-doped metal oxide nanocrystals have been reported to be much lower than those of the corresponding bulk phosphors, group II-VI, and halide-based perovskite quantum dots because of their poor crystallinity and high-concentration surface defects. Here, an ultrafast and room-temperature strategy for the kilogram-scale synthesis of sub-5 nm Eu3+ -doped CaMoO4 nanocrystals is presented, and this reaction can be finished in 1 min under ambient conditions. The absolute PLQYs for sub-5 nm Eu3+ -doped CaMoO4 nanocrystals can reach over 85%, which are comparable to those of the corresponding bulk phosphors prepared by the high-temperature solid state reaction. Moreover, the as-produced nanocrystals exhibit a superior thermal stability and their emission intensity unexpectedly increases after sintering at 600 °C for 2 h in air. 1.9 kg of Eu3+ -doped CaMoO4 nanocrystals with a PLQY of 85.1% can be obtained in single reaction.

Photoluminescence enhancement of orange-emitting Ca5(PO4)2SiO4:Sm3+ phosphor through charge compensation of A+ (Li+, Na+ and K+) ions for white light-emitting diodes

The orange-emitting Ca_5-x(PO₄)₂SiO₄:xSm³⁺ (C₅PSO:Sm³⁺) phosphor was prepared via a simple solid-state method, and the charge compensators A⁺ (A = Li, Na and K) were codoped into C₅PSO:Sm³⁺ for improving the luminescence performance. The influences of Sm³⁺ doping and Sm³⁺/A⁺ codoping on the crystal structure and the luminescence performance of the C₅PSO:Sm³⁺ phosphor were investigated in detail. The X-ray diffraction results exhibited that all the as-prepared samples were assigned to the standard structure Ca₅(PO₄)₂SiO₄ possessing the P63/m space group. Upon near-ultraviolet excitation at 401 nm, the characteristic emission peaks of the C₅PSO:Sm³⁺ phosphors are located at 558 nm, 605 nm and 656 nm, respectively, which are derived from the ⁴G_5/2 → ⁶H_J (J = 5/2, 7/2, and 9/2) electron transitions of Sm³⁺ ions. Furthermore, a significant luminescence improvement of the C₅PSO:Sm³⁺ phosphor was attained through charge compensation of codoped A⁺ ions, and the emission intensity is enhanced by 1.79-, 1.45-, and 1.14-fold for K⁺, Na⁺, and Li⁺, respectively. In addition, the actual orange-red LED and w-LED fabricated with the as-prepared C₅PSO:Sm³⁺,K⁺ phosphor showed excellent optical performance. All the results demonstrated that the C₅PSO:Sm³⁺,K⁺ orange-emitting phosphor could act as a potential orange-red component in the w-LEDs illumination field.

ZnSnO3–hBN nanocomposite-based piezocatalyst: ultrasound assisted reactive oxygen species generation for degradation of organic pollutants

Ultrasound assisted sustainable degradation of RhB by a lead-free ferroelectric ZnSnO₃–hBN piezocatalyst.

Blue Emitting BaAl2O4:Ce3+ Nanophosphors with High Color Purity and Brightness for White LEDs

In this work, strongly blue emitting Ce3+-activated BaAl2O4 nanophosphors were successfully synthesized by a sol-gel technique. The crystal structure, morphology, and microstructure of the nanophosphors have been studied by X-ray powder diffraction, field emission scanning electron microscopy, and high-resolution transmission electron microscopy. The photoluminescence spectra show the impact of concentration variation of Ce3+ on the photoluminescence emission of the phosphor. These nanophosphors display intense blue emission peaking at 422 nm generated by the Ce3+ 5d → 4f transition under 350 nm excitation. Our results reveal that this nanophosphor has the capability to take part in the emergent domain of solid-state lighting and field-emission display devices.

Layered Structure Produced Nonconcentration Quenching in a Novel Eu3+-Doped Phosphor

Energy migration (energy transfer among identical luminescence centers) is always thought to be related to the concentration quenching in luminescence materials. However, the novel Eu³⁺-doped Ba₆Gd₂Ti₄O₁₇ phosphor seems to be an exception. In the series of Ba₆Gd_{2(1- x)}Ti₄O₁₇: xEu³⁺ ( x = 0.1, 0.3, 0.5, 0.7, and 0.9) phosphors prepared and investigated, no concentration quenching is found. Detailed investigations of the crystal structure and the luminescence properties of Ba₆Gd_{2(1- x)}Ti₄O₁₇: xEu³⁺ reveal that the nonoccurrence of concentration quenching is related to the dimensional restriction of energy migration inside the crystal lattices. In Ba₆Gd₂Ti₄O₁₇, directly increasing the number of Eu³⁺ ions to absorb as much excitation energy as possible allows to achieve a higher brightness. The highly Eu³⁺-doped Ba₆Gd_{2(1- x)}Ti₄O₁₇: xEu³⁺ ( x = 0.9) sample can convert near-UV excitation into red light, whose Commission Internationale de l'Eclairage (CIE) coordinates are (0.64, 0.36) and the color purity can reach up to 94.4%. Moreover, warm white light with the CIE chromaticity coordinates of (0.39, 0.39), the correlated color temperature of 3756 K, and the color rendering index of 82.2 is successfully generated by fabricating this highly Eu³⁺-doped phosphor in a near-UV light-emitting diode chip together with the green YGAB:Tb³⁺ and blue BAM:Eu²⁺ phosphors.

White light emitting MgAl2O4:Dy3+,Eu3+ nanophosphor for multifunctional applications

An efficient energy transfer from Dy³⁺ to Eu³⁺ in MgAl₂O₄ offers white light emission and self-referencing thermal behaviour.