Photoluminescence and afterglow of Dy3+ doped CaAl2O4 derived via sol–gel combustion

Temperature-dependent photoluminescence of novel Eu3+, Tb3+, and Dy3+ doped LaCa4O(BO3)3: Insights at low and room temperatures

This study explores the structural and optical qualities of LaCa4O(BO3)3 (LACOB) phosphors doped with Eu3+, Dy3+, and Tb3+ using a microwave-assisted sol-gel technique. It uncovers oxygen-related luminescence defects in LACOB, highlighting emission peaks at 489 and 585 nm for Dy3+, a distinct sharp peak at 611 nm for Eu3+ in the red spectrum, and a notable green emission for Tb3+ due to specific transitions. The photoluminescence (PL) analysis indicates that luminescence is optimized through precise doping, leveraging dipole interactions, and localized resonant energy transfer, which are influenced by dopant concentration and spatial configuration. Temperature studies show emission intensity variations, particularly noticeable below 100 K for Tb3+ doped samples, demonstrating the nuanced balance between thermal quenching and luminescence efficiency. This temperature dependency, alongside the identified optimal doping conditions, underscores the potential of these materials for advanced photonic applications, offering insights into their thermal behavior and emission mechanisms under different conditions.

Temperature-responsive insights: Investigating Eu3+ and Dy3+ activated yttrium calcium oxyborate phosphors for structure and luminescence

An investigation into the luminescent behavior of YCOB (Yttrium Calcium Oxyborate) doped with Eu3+ and Dy3+ ions, synthesized via the combustion method, is presented. The study, employing X-ray diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), and Energy-Dispersive X-ray Spectroscopy (EDS) analyses, confirms the structural integrity and purity of the synthesized nanophosphors. An XRD pattern exhibiting distinct crystalline peaks indicates that the dopant ions were successfully integrated into the YCOB lattice. The photoluminescence (PL) response of YCOB with Eu3+ and Dy3+ ions is thoroughly examined, uncovering distinct excitation and emission spectra. In the case of Eu3+ doping, excitation spectra reveal a significant charge transfer (CT) band at 254 nm, indicative of electron transfer between oxygen and europium ions. This CT transition enhances our understanding of the excitation behavior, with the dominant and Laporte-forbidden 5D0 → 7F2 transition. Characteristic peaks at 345 nm in the excitation spectra efficiently stimulate YCOB:Dy3+ when Dy3+ is used as a dopant. The primary emission peak at 585 nm corresponds to the hypersensitive electric dipole transition 4F9/2-6H13/2. Concentration quenching phenomena are observed, with a maximum Eu3+ concentration of 7 wt % attributed to the dipole-quadrupole interaction. Dy3+ doping, with a maximum concentration of 2 wt % primarily shows multipolar interactions, especially dipole-dipole interactions. The study extends to CIE chromaticity analysis, emphasizing Eu3+ doping's suitability for white light-emitting diode (WLED) applications and ensuring color stability. Conversely, varying Dy3+ concentrations do not yield consistent chromaticity coordinates. These findings have significant implications for the development of advanced phosphor materials across diverse applications, offering a roadmap for optimizing their optical performance.

A Review of the Efficiency of White Light (or Other) Emissions in Singly and Co-Doped Dy3+ Ions in Different Host (Phosphate, Silicate, Aluminate) Materials

In this review we will present several research papers pertaining to white colour (or other) emission from Dy3+ doped and undoped phosphor materials. The search for a single component phosphor material that could deliver high quality white light under UV or near UV excitation is an area of active research for commercial purposes. Amongst all rare earth elements Dy3+ is the only ion that could deliver simultaneously blue and yellow light under UV excitation. In optimizing the Yellow/Blue emission intensity ratios, white light emission can be realized. Dy3+ (4f9) displays approximately 4 emission peaks at around 480 nm, 575 nm, 670 and 758 nm corresponding to transitions from the metastable 4F9/2 state to various lower states, such as 6H15/2 (blue), 6H13/2 (yellow), 6H11/2 (red) and 6H9/2 (brownish red), respectively. In general, the hypersensitive transition at 6H13/2 (yellow) is electric dipole in nature and becomes prominent only when Dy3+ ions are positioned at low symmetric sites with no inversion symmetry in the host matrix. On the other hand, the blue magnetic dipole transition at 6H15/2 becomes prominent only when Dy3+ ions are positioned at highly symmetric sites in the host material with inversion symmetry. Despite the white colour emission from the Dy3+ ions, these transitions are mainly associated with parity forbidden 4f -4f transitions, the white light produced maybe diminished at times, hence the need to include a sensitizer to bolster the forbidden transitions experienced by Dy3+ ions. In this review we will focus on the variability of the Yellow/Blue emission intensities in different host materials (phosphates, silicates, and aluminates) from Dy3+ ions (doped or undoped) by studying their photoluminescent properties (PL), their CIE chromaticity coordinates and correlated colour temperature (CCT) values for white colour emissions that is adaptable to different environmental conditions.

Bluish-green afterglow and blue photoluminescence of undoped BaAl2O4

Undoped BaAl2O4 was derived via sol-gel combustion technique. The afterglow and photoluminescence (PL) properties of undoped BaAl2O4 were explored with the combination of experiments and density functional theory (DFT) calculations. Undoped BaAl2O4 is found to display bluish-green afterglow that is discernible to naked eye in dark for about 20 s. The broad afterglow spectrum of undoped BaAl2O4 is peaked at around 495 nm. As a contrast, the broad PL spectrum of undoped BaAl2O4 can be decomposed into a bluish-green PL band peaking at about 2.53 eV (490 nm) and a blue PL band centered at about 3.08 eV (402.6 nm). DFT calculations indicate that the defect energy levels generated by oxygen and barium vacancies are critical to the afterglow and PL of undoped BaAl2O4. This work demonstrates that the oxygen and barium vacancies in undoped BaAl2O4 are liable for the bluish-green afterglow and blue PL of undoped BaAl2O4. The recorded bluish-green afterglow of BaAl2O4 is particularly important to understand the afterglow mechanisms of rare-earth doped BaAl2O4.

Development of water-dispersible Dy(III)-based organic framework as a fluorescent and electrochemical probe for quantitative detection of tannic acid in real alcoholic and fruit beverages

Tannic acid (TA) is a water-soluble polyphenol and used in beverages, medical fields as clarifying and additive agents. In daily life, TA is unavoidable, and excessive consumption of tannin containing foods can harm health. Thus, rapid and sensitive quantification is highly necessary. Herein, an eco-friendly fluorometric and electrochemical sensing of TA was developed based on a dysprosium(III)-metal-organic framework (Dy(III)-MOF). An aqueous dispersion of Dy(III)-MOF exhibits strong dual emissions at 479 and 572 nm with an excitation at 272 nm, due to the 4f-4f electronic transition and "antenna effect". Chromophore site of the functional ligand, and Dy(III) ion could potentially serve as a sensing probe for TA via quenching (fluorescence). The fluorometric sensor worked well in a wide linear range concentrations from 0.02 to 25 μM with a limit of detection (LOD) of 0.0053 μM. Secondly, the cyclic voltammetric of TA at Dy(III)-MOF modified screen-printed carbon electrode (SPCE) has been investigated. The Dy(III)-MOF/SPCE showed an anodic peak signal at +0.22 V with a five-fold stronger current than the control electrode surface. Under optimized sensing parameters, the Dy(III)-MOF/SPCE delivered wide linear concentrations from 0.01 to 200 μM with a LOD of 0.0023 μM (S/N = 3). Accessibility of real practical samples in alcoholic and juice-based beverages were quantified, resulting in superior recovery rates (98.13-99.53%), F-test, and t-test confirmed high reliability (<95% confidence level (n = 3)). Finally, practicability result of the electrochemical method was validated by fluorometric with a relative standard deviation (RSD) of 0.18-0.46 ± 0.17% (n = 3). The designed probe has proven to be a key candidate for the accurate analysis of TA in beverage samples to ensure food quality.