Zeolitic Imidazolate Framework-8 (ZIF-8) having primary linker 2-methylimidazole inherently exhibits visible emission. In this study, ultraviolet (UV) emission in UVC-UVB range (290-300 nm) has been generated from ZIF-8 by incorporating a secondary linker (benzimidazole) in the framework. The intensity of this novel UV emission is further enhanced with a quantum yield of 62.3% by confining N,N-dimethylformamide (DMF) molecules with in the pore network of hybrid ZIF-8. Photoluminescence lifetime measurements under different excitations confirm its origin to rapid radiative decay of the excited states through fluorescence without any contribution from the phosphorescence. Theoretical studies using the Density Functional Theory provide evidence of modifications in band structure and density of states due to the involvement of the exchanged benzimidazole in the charge transfer mechanism. The modifications in the band structure leading to enhancement in the intensity are attributed to guest-host interaction between entrapped DMF molecules and the hybrid ZIF-8. The observed intense and tunable emission in UVC-UVB range from hybrid ZIF-8 makes it a suitable material for inactivation of bacteria and virus, curing, environmental sensing, plant growth lighting, and phototherapy.

Developing persistent luminescence (PersL) materials that operate reliably at elevated temperatures is challenging due to rapid trap depopulation and thermal quenching of emission. Here, we demonstrate long-lasting PersL for several hours with stable multi-modal and multi-color emission at temperatures as high as 300 degrees C from Tb3+ in LaAlO3 host system after being co-doped with Eu3+ and Yb3+ for the first time. These LaAlO3:Tb3+,Eu3+,Yb3+ nanoparticles, synthesized via co-precipitation followed by a molten salt reaction, exhibit efficient downconversion, upconversion, PersL, optically stimulated luminescence (OSL), and thermally stimulated luminescence (TSL). TSL reveals four continuous trap levels, including a deep trap (similar to 290 degrees C) responsible for long-term charge storage and high-temperature stability. Notably, Tb3+ dopant acts not only as an emission center but also as an auxiliary trap for Eu3+ in the co-doped system. Density functional theory (DFT) calculations provide a unified trapping-de-trapping mechanism consistent with experimental results. These luminescent nanoparticles further exhibit strong radioluminescence with linear X-ray response, highlighting its potential as a scintillator, while its PersL further underscores its suitability for storage and imaging applications. These findings overcome the limitation of poor PersL in LaAlO3 and position our LaAlO3-based luminescent nanoparticles as desirable candidates for high-temperature optical data storage and anti-counterfeiting technologies.

The immobilization of trivalent minor actinides (Am3+, Cm3+) is critical for nuclear waste management due to their long half-lives and radiotoxicity. LBNBS glasses were synthesized by melt quenching, with Eu3+ used as a spectroscopic surrogate. Structural, optical, chemical, and radiation responses were studied using XRD, SEM-EDX, photoluminescence (PL), gamma irradiation (5-1000 kGy), ASTM C1285-94 leaching tests, and positron annihilation lifetime spectroscopy (PALS). The glasses showed amorphous homogeneity and uniform dopant distribution. Leaching enhanced PL intensity due to reduced surface quenching, while irradiation caused defect-related PL quenching without altering spectral profiles. PALS revealed intrinsic free-volume defects in unirradiated glass (tau, = 0.297 ns, tau 2 = 0.765 ns), which decreased after irradiation up to 1000 kGy (tau, approximate to 0.247-0.250 ns; tau 2 approximate to 0.694-0.697 ns), indicating radiation-induced densification. The stable Eu3+ environment and dose-dependent CIE shift (0.56618, 0.42029 to 0.49101, 0.48826) confirm suitability for actinide immobilization and radiation sensing.

Developing persistent luminescence (PersL) materials that operate reliably at elevated temperatures is challenging due to rapid trap depopulation and thermal quenching of emission. Here, we demonstrate long-lasting PersL for several hours with stable multi-modal and multi-color emission at temperatures as high as 300 °C from Tb 3+ in LaAlO 3 host system after being co-doped with Eu 3+ and Yb 3+ for the first time. These LaAlO 3 :Tb 3+ ,Eu 3+ ,Yb 3+ nanoparticles, synthesized via co-precipitation followed by a molten salt reaction, exhibit efficient downconversion, upconversion, PersL, optically stimulated luminescence (OSL), and thermally stimulated luminescence (TSL). TSL reveals four continuous trap levels, including a deep trap (∼290 °C) responsible for long-term charge storage and high-temperature stability. Notably, Tb 3+ dopant acts not only as an emission center but also as an auxiliary trap for Eu 3+ in the co-doped system. Density functional theory (DFT) calculations provide a unified trapping–de-trapping mechanism consistent with experimental results. These luminescent nanoparticles further exhibit strong radioluminescence with linear X-ray response, highlighting its potential as a scintillator, while its PersL further underscores its suitability for storage and imaging applications. These findings overcome the limitation of poor PersL in LaAlO 3 and position our LaAlO 3 -based luminescent nanoparticles as desirable candidates for high-temperature optical data storage and anti-counterfeiting technologies.

Narrow ultraviolet and broad tunable near-infrared dual-band emitting single-phase phosphors are scientifically significant and technologically challenging. However, their development remains difficult due to the complexity of achieving multiple luminescent properties through single metal ion doping and defect engineering. In this study, we report narrow-band UV-B and broadband tunable NIR emissions from Gd-doped MgAl2O4 phosphors. Their photoluminescence covers down-conversion across UV, visible, and NIR regions. Its NIR emission is tunable and red-shifts when being excited at long excitation wavelengths. Also, they show visible-to-UVB and UVA up-conversion emissions, attributed to intermediate bands created by defects such as oxygen vacancies and interstitial oxygen as confirmed by EPR analysis. DFT-based calculations have identified defect-based mid-gap states, correlating with the observed emissions. These findings provide insights into the defect-related mechanisms governing both down-conversion and up-conversion in Gd-doped MgAl2O4. This study is expected to excite researchers to explore dual emitting phosphors across UV and NIR ranges.

Achieving multimodal luminescence within a single phosphor is vital for multifunctional applications but remains challenging due to complex color tuning and trap engineering. In this study, we report Pr3+ and Gd3+ co-doped LaAlO3 (LAO:PG) phosphors, designed through careful modulation of multilevel traps and Pr3+ → Gd3+ energy transfer dynamics. These materials exhibit diverse luminescence modes, including down-conversion luminescence (DCL), up-conversion luminescence (UCL), persistent luminescence (PersL), optically stimulated luminescence (OSL), and thermally stimulated luminescence (TSL) across a wide spectral range. Unlike previously studied Pr3+-doped LAO, the co-doped LAO:PG shows DCL in both UV-visible and NIR regions and displays ultraviolet-C UCL under visible excitation. Notably, we observe, for the first time, PersL lasting several minutes in these phosphors-an improvement over the non-PersL behavior of Pr3+ -only doped LAO. Additionally, the LAO:PG phosphors exhibit strong OSL response. TSL analysis reveals five distinct trap levels linked to these properties. Density functional theory calculations further correlate intrinsic defects to these traps, supporting a proposed mechanism for the observed multimodal luminescence. These findings highlight LAO:PG as a promising platform for developing advanced phosphors with integrated luminescence modes, paving the way for future applications in data storage, phototherapy, and anti-counterfeiting technologies.

Long-lasting persistent phosphors with efficient multimodal luminescence properties serve not only as effective storage phosphors but also as essential components for developing reliable anticounterfeiting materials. However, achieving simultaneous multimodal luminescence in storage phosphors poses a significant challenge, as it necessitates the coexistence of multiple luminescence mechanisms within the same matrix along with the creation of effective traps at various energy levels for charge carrier storage. This study presents the synthesis of LaAlO3 phosphors doped with varying mol % of Sm3+ using a coprecipitation method followed by a molten salt reaction. The objective is to investigate their multimodal luminescence properties and potential applications in optical storage and anticounterfeiting. These phosphors exhibit persistent luminescence (PersL) lasting for hours and controllable by doping levels along with efficient optically stimulated luminescence (OSL) when being excited by a 980 nm laser after UV preirradiation. Thermo-stimulated luminescence (TSL) reveals multiple deep traps with enhanced OSL. Additionally, the LAO:0.5S phosphor shows PersL upon X-ray irradiation, suggesting potential for imaging applications. Gd3+ incorporation optimized PersL and OSL performance while DFT calculations elucidated trapping mechanisms. These findings of tetra-modal luminescence comprising downconversion luminescence (PL & RL), PersL, OSL, and TSL highlight the multifunctional potential of these LaAlO3-based phosphors for advanced optical applications.

Persistent phosphors with high charge storage capacity are promising for a wide range of applications, mostly demonstrated at room temperature. Designing such long-persistent phosphor (LPP) applicable at higher temperature is largely unexplored and challenging. To prevent spontaneous charge release and ensure long-term data retention, high-temperature LPPs must feature multilevel traps with sufficient activation energies. In this report, LaAlO3:Eu3+ (LAO:E) phosphor is investigated with multiple traps and four integrated luminescent emissions: down-conversion photoluminescence and radioluminescence, thermally stimulated luminescence, persistent luminescence (PersL), and optically stimulated luminescence (OSL). Unlike earlier optical storage phosphors, our LAO:E phosphor possesses charge carriers that are released from these traps, ranging from shallow trap 1 to deep trap 4, across various temperatures. The potential for the long-term storage of charge carriers at both room and elevated temperatures is also examined. Supported by experimental data and density functional theory calculations, we establish a correlation between the various traps and the desired PersL and OSL properties of the LAO:E phosphor. Additionally, a comprehensive trapping-detrapping mechanism for charge carriers is developed. The studies here are expected to pave the way for designing advanced multimode phosphors for a wide range of applications at high temperatures.

Persistent phosphors with high charge storage capacity are promising for a wide range of applications, mostly demonstrated at room temperature. Designing such long‐persistent phosphor (LPP) applicable at higher temperature is largely unexplored and challenging. To prevent spontaneous charge release and ensure long‐term data retention, high‐temperature LPPs must feature multilevel traps with sufficient activation energies. In this report, LaAlO 3 :Eu 3+ (LAO:E) phosphor is investigated with multiple traps and four integrated luminescent emissions: down‐conversion photoluminescence and radioluminescence, thermally stimulated luminescence, persistent luminescence (PersL), and optically stimulated luminescence (OSL). Unlike earlier optical storage phosphors, our LAO:E phosphor possesses charge carriers that are released from these traps, ranging from shallow trap 1 to deep trap 4, across various temperatures. The potential for the long‐term storage of charge carriers at both room and elevated temperatures is also examined. Supported by experimental data and density functional theory calculations, we establish a correlation between the various traps and the desired PersL and OSL properties of the LAO:E phosphor. Additionally, a comprehensive trapping–detrapping mechanism for charge carriers is developed. The studies here are expected to pave the way for designing advanced multimode phosphors for a wide range of applications at high temperatures.

The deep-ultraviolet (UV) light market is currently dominated by low-pressure mercury-vapor lamps, which raise environmental concerns due to mercury toxicity and disposal challenges. This has prompted the development of eco-friendly UV light sources using non-toxic hosts. While UV phosphors doped with rare earth and transition metals are well-studied, defect-based UV-emitting materials without dopants offer a promising alternative. Producing emissions across UV, visible, and near-infrared (NIR) wavelengths from a single phosphor is challenging due to the complexity of creating multiple electronic states within the band gap. In this study, we demonstrate for the first time that dopant-free MgAl2O4 can function as a multi-color phosphor emitting across UVC, UVB, visible, and NIR regions via defect modulation. Our analysis shows that oxygen vacancies, cationic vacancies, and interstitial oxygen play key roles in the material's luminescence, capturing and recombining charge carriers. This work paves the way for developing versatile, non-toxic phosphors for various applications.

Effective management of radioactive liquid waste necessitates the development of advanced separation techniques with high capacity and selectivity for radionuclides. This study presents a facile, cost-effective, and environmentally friendly method for the simultaneous separation of trivalent americium (Am(III)), tetravalent plutonium (Pu(IV)), and hexavalent plutonium (Pu(VI)) from acidic nuclear waste solutions. We demonstrate the remarkable potential of thiol (SH-) -functionalized multi-walled carbon nanotubes (SH-MWCNTs) as adsorbents for these actinides. Amide functionality MWCNT with O = C-NH-CH2-CH2-SH- and this is termed as SH-MWCNT (Thiol Functionalized Multi-Walled Carbon Nanotubes).Batch adsorption experiments revealed an extraction efficiency trend of Am(III) < Pu(IV) < Pu(VI), suggesting a strong influence of actinide oxidation state on adsorption behavior. Detailed characterization of the SH-MWCNTs was performed using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray elemental mapping. The adsorption kinetics followed a pseudo-second-order model, indicating chemisorption as the dominant mechanism. Furthermore, the adsorption process adhered to the Langmuir isotherm model, suggesting monolayer coverage of the actinides on the SH-MWCNT surface. The measured distribution coefficients (Kd) for Pu(IV), Pu(VI), and Am(III) were 7055 ml/g, 4512 ml/g, and 3525 ml/g in 1 M HNO3 at room temperature, respectively. Thermodynamic investigations revealed the endothermic nature of the adsorption process. The SH-MWCNTs exhibited exceptional radiation stability under gamma irradiation and demonstrated potential for regeneration and reusability, making them promising candidates for long-term radioactive wastewater treatment.

Understanding the mechanisms of radiation induced defect generation is essential for assessment of materials to be used in nuclear environments. In the current work, we investigate the effect of 10 MeV electron irradiation on the generation and possible ordering of defects/oxygen vacancies in hydroxyapatite (HAP) powders. Comprehensive analyses of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Electron Paramagnetic Resonance (EPR) and Raman spectra establish that (a) HAP has a high level of structural stability even after exposure to electron irradiation; (b) irradiation leads to the generation of surface defects/oxygen vacancy predominantly in the PO43- polyanion site, particularly in part of asymmetric bonding within the P-O bonds and (c) there is noticeable evidence for an ordered arrangement of oxygen vacancies within the HAP irradiated at 1 MGy dose. These radiation-induced defects, such as oxygen vacancies, can migrate within the HAP lattice, leading to formation of defect/oxygen vacancies clusters which ultimately results in the ordering tendency of oxygen vacancies within the lattice. The observed ordering, as evidenced by the photoluminescence intensities, aligns with the sequence HAP-1MGy > HAP-20MGy > HAP, providing further support for the presence of ordered oxygen vacancies.

The manuscript reports the synthesis of Dy3+ incorporated lithium magnesium borate glass by melt quenching technique. FTIR study revealed the presence of both BO3 as well as tetrahedral BO4 units through their characteristic frequencies. Photoluminescence (PL) study of unirradiated samples confirmed the presence of Dy dopant in the '+3' oxidation states from the characteristic emissions at 482, 578, 666 and 716 nm corresponding to F-4(9/2) -> H-6(15/2), F-4(9/2) -> H-6(13/2) and F-4(9/2) -> H-6(11/2), F-4(9/2) -> H-6(9/2) transitions, respectively. Thermal neutron and gamma irradiated PL emission and lifetime characteristics were discussed in details based on the different defect centers. Thermal neutron irradiated TL study showed that the material has a broad and single dosimetry glow peak at about 450 K which showed high fading due to low temperature peak. TL based neutron sensitivity of LMB: Dy3+ was found to be about 37.4 times less than that of standard TLD-100 (LiF: Mg, Ti) powder. The net TL response from about 3 to 83 mSv of neutron dose was found to be linear (Adj. R-2 = 0.9994) which is one of the most desirable properties for dosimetry applications. In addition, the TL trap parameters were evaluated using both deconvolution of TL glow curve and peak shape method as suggested by Chen which were found to be matching with each other.

Long persistent phosphors (LPPs) with high charge storage capacity are promising for a wide range of applications, e.g., next-generation optical data storage and advanced anti-counterfeiting technologies. While more and more LPPs have been demonstrated to be effective at room temperature, their potential at high temperature remains mostly underexplored. Unlike magnetic storage technologies, which suffer from demagnetization and data loss at elevated temperatures, desirable LPPs must have deep traps to prevent spontaneous charge release and ensure data retention. In this report, we have investigated LaAlO3:Eu3+ phosphor with multiple traps with a red persistent luminescence lasting 17 hours and demonstrated its multi-modal luminescence properties for both room and high-temperature applications. Supported with experimental and density functional theory (DFT) calculations, we have identified four distinct traps with varying depths from the LaAlO3:Eu3+ phosphor and confirmed their role in sequential charge release at different temperatures. Additionally, we have detected highly intense optically stimulated luminescence from the LaAlO3:Eu3+ phosphor 35 days after UV irradiation. We have further demonstrated its potential anti-counterfeiting and data storage applications by integrating its four luminescence modes. This research work paves the way for developing novel LPPs suited for applications under diverse environmental conditions.

Fluorite single crystals, CaF2 are multifunctional crystals that have potential applications in environmental, thermo-luminescent and accidental dosimetry. A comprehensive investigation of the co-located naturally occurring colourless and coloured (yellow, sea-green, purple, blue, black) fluorites (CaF2) doped with bivalent and multivalent cations was carried out for the cationic and anionic sub-lattice defects generated due to natural irradiation from associated actinide containing pyrochlore grains. Detailed spectroscopic analyses have been used to map the various cationic and anionic defect structures such as O-3(-) and O2--Vacancy type defect complexes in yellow fluorites, F-centres and irradiation induced metallic Ca in purple, blue and black fluorites. The confinement of the radiation damage only to the anionic sub-lattice was explained in terms of higher displacement cross-section for F (59 b) as compared to Ca (33 b) as well as lower energy requirement to create F displacements and vacancies. It is observed that the fluorite retained its phase stability under natural radiation exposure and elemental substitutions.

Electron paramagnetic resonance (EPR) spectroscopy is very sensitive to paramagnetic (PM) defect centers and is widely used to monitor the magnetic ordering of various PM species. Because the line width and intensity of the EPR spectrum are related to the magnetic ordering of the PM species, temperature variation of EPR spectra provides a wealth of information about the presence of ferromagnetic ordering in the sample. This chapter focuses on PM anionic and cationic vacancies in many oxide-based compounds, which can cause dilute ferromagnetism. Furthermore, EPR spectroscopy provides information about the transformation of various defect centers, which has a direct impact on the magnetic properties.

In this manuscript, gel-combustion synthesis of Al5BO9:xTb(3+) (x = 0.0%, 0.05%, 0.1%, 0.2% and 1.5%) phosphor along with the detailed structural characterizations using a host of techniques such as XRD, SEM, EDS, IR, EXAFS and PL etc. has been reported. XRD analysis confirmed the phase pure formation and also the nanocrystalline nature of the materials. Detailed EXAFS analysis explained the oxidation state and the coordination behaviour of Tb3+ ion in the Al5BO9 matrix. PL study showed that the material can be a potential green light emitting phosphor. Thermoluminescence (TL) study revealed the presence of a wide shoulder peak and a broad dosimetry peak situating at 551 K. Net TL response from B-10 and B-11 enriched Al5BO9:0.1%Tb3+ thin pellets showed prolonged linearity within the thermal neutron fluence range of 3.2 x 10(10) to 1.6 x 10(11) n/cm(2). Also, the maximum fading of the TL signal is only 9% during the storage period of 112 days. These indicates that the developed material can be a potential candidate for dosimetry applications involving high intensity slow neutron beams. The TL glow curve was deconvoluted which revealed the presence of five individual peaks whose kinetic parameters viz. activation energy (E), order of kinetics (b) and frequency factor (s) were evaluated using both glow curve deconvolution and Chen's peak shape method and the results were found to be in good agreement.

Generating multicolor photoluminescence including white light from the same phosphor is advantageous while often a challenging task. Herein, a detailed study on excitation-dependent tunable photoluminescence characteristics in Eu3+ and Tb3+ co-doped SrF2 phosphor has been carried out. This phosphor yields lights of various colors including red, orange, and near white due to the change of the relative intensity of the blue, green, orange, and red color transitions of Eu3+ and Tb3+ ions. As revealed from DFT-based theoretical calculation, the existence of various mid-gap states created by the p orbitals of F- and f and d orbitals of Eu3+ and Tb3+ ions inside the wide band gap SrF2 host is responsible for the existence of multiple excitation peaks. The intensity of these excitation peaks is fully governed by the relative occupancy of these mid-gap states. This study helps future design of single phase multicolor emitting phosphor based lighting devices.