Thermoluminescence Analysis Research Articles

Improving storage duration of tomatoes (Solanum lycopersicum) through electron beam technology.

Electron beam (EB) technology typically consists of high-energy electron streams produced by a linear accelerator. Although promising, the use of EB irradiation as a technique to delay ripening and prevent spoilage in tomatoes has not been extensively investigated. In this study, the effectiveness of EB irradiation in prolonging the shelf life of tomatoes postharvest was investigated. The results indicated that EB irradiation successfully reduced microbial contamination and decay, preserved key quality attributes (such as total soluble solids, titratable acidity, pH, and firmness), and significantly minimized weight loss. Notably, the treatment delayed the biosynthesis of lycopene, a key indicator of ripening, without adversely affecting phenolic content and antioxidant activity, which remained consistent regardless of irradiation. Additionally, different methods for detecting irradiation were evaluated. Thermoluminescence analysis proved to be the most dependable technique, especially for doses exceeding 600Gy, due to its high sensitivity and specificity. In contrast, photostimulated luminescence and electron spin resonance analyses showed limitations in accurately identifying the irradiation status of foods with high moisture content, such as tomatoes. This study confirms that EB irradiation, while maintaining postharvest quality, extends the shelf life of tomatoes by 5-10days, suggesting its potential for commercial application in food preservation.

Band-gap engineering enabled emission switch in solid-solution phosphors LiIn1-xScxGeO4:Bi3+ for spectral-temporal anti-counterfeiting

The interaction between matrix lattice and doped activator has long been pivotal topic in the research of the state-of-the-art functional materials, particularly luminescent materials. With the ceaseless development of advanced anti-counterfeiting, there are imperative need for developing luminescent materials with wide emission tunability, excellent visibility, and adjustable persistent luminescence. Herein, we present a paradigm to obtain great emission tunability in a solid-solution phosphors LiIn1-xScxGeO4:Bi3+ (x = 0–1) via band-gap engineering. With the increase in Sc content, the band-gap enlarges, causing the Bi3+ emissions gradually shift from 580 to 456 nm. As Sc substitution continues, the Bi3+ emissions transfer from the metal-to-metal charge transfer band to the inter s-p transition, resulting in a rapid shift in emission from 456 to 356 nm. This emission shift not only achieves a record total tunability of 224 nm among Bi3+-doped solid-solution phosphors but also an informative band-gap dependent emission mechanism of the Bi3+ activator. Furthermore, the samples gradually exhibited a persistent luminescence through the substitution process, attributed to the increasing traps by the thermoluminescence analysis. Leveraging these unique spectral properties, we designed two types of patterns that can be distinguished from color and time within the visible light range, demonstrating that the obtained phosphors can serve as promising candidate materials for spectral-temporal anti-counterfeiting.

Beta-irradiated ZnGa2O4:Sm3+ phosphor: Thermoluminescence glow curves and kinetic parameters via gel combustion synthesis

This study examines the X-ray Diffraction (XRD) characteristics of Sm3+-doped ZnGa2O4 phosphor, shedding light on its structural characteristics. The XRD data reveal distinctive peaks that represent the crystal's lattice structure. This provides the basis for a more detailed analysis of thermoluminescence (TL). Initially, the TL glow curves corresponding to different concentrations of Sm were analysed, leading to the identification of the most favorable Sm concentration. Subsequently, an investigation was conducted into the TL behavior of the material in response to varying doses within a broad spectrum of beta radiation, revealing a linear characteristic (b=1.075) across doses ranging from 0.1 Gy to 50 Gy. Following this, a reusability assessment was executed over three measurement sets, wherein it was ascertained that the deviation in peak area across ten cycles did not surpass 2 %. Furthermore, it was investigated how different heating rates ranging from 0.5 °C/s to 7 °C/s affect the TL curve of the material. To determine the TL trap parameters of the sample, Initial Rise (IR) and Computerized Glow Curve Deconvolution (CGCD) methods were employed. A consistent pattern of activation energy values was observed in both IR in the TM-Tstop experiment and CGCD analyses, indicating a uniform response to distinct energy levels within the sample. In terms of providing valuable insights into the characteristics of TL, these methods were found to be very effective. This contributed to a comprehensive understanding of charge carrier dynamics within the crystal lattice. Moreover, Peaks I, II, and III showed a linear response to applied doses, indicating the material's potential for dosimetry applications. The findings of this study not only provide insights into Sm3+-doped ZnGd2O4 phosphors' TL properties, but also enhance our understanding of how to optimize their radiation response.

Theoretical study on the thermoluminescence kinetics by glow curve analysis based on the genetic algorithm

The analysis of thermoluminescence (TL) glow curve is an important way to investigate the trap structure of the materials as well as the kinetics of the charge carrier transfer. Most currently used methods rely on the existence of an explicit expression of the theoretical glow curve. However, since the set of kinetic equations describing the TL process does not have analytical solutions, the derivation of an explicit expression always involves some sort of assumptions and approximations, which can compromise the universality and accuracy of the method. This paper proposes a new algorithm that focuses on the original kinetic equations and does not necessitate an explicit expression to analyze the TL glow curve. This algorithm establishes an objective function to evaluate the fitness of a selected combination of kinetic parameters, and then using the genetic algorithm (GA) to search for the optimal parameters. Various occasions were numerically simulated, demonstrating the algorithm's capability to handle kinetics of different order, multiple interactive peaks, deep trap, non-linear heating, and temperature dependent parameter cases. An actual glow curve of the LiF:Mg,Cu,P chip was also analyzed using this algorithm, and the corresponding kinetic parameters were identified. This algorithm provides a more universal and valid method for TL glow curve analysis.

Investigations of structural, photoluminescence, colorimetric, lifetime, and luminous efficiency of Tb3+ and Sm3+ co-doped calcium tungstate for WLEDs

Structure, photoluminescence, colorimetric, and thermoluminescence analysis of Ca1-x-yTb2x/3Sm2y/3WO4; x = 0.01; y = 0.01–0.05 ceramics are reported in this manuscript. The materials are made by the use of the solid-state method. Reitveld refinements of the obtained X-ray diffraction patterns are done by using the Fullprof Suite software. The obtained results denoted that the synthesized materials have a tetragonal structure and I41/a space group. Energy bandgaps are found in the UV–visible absorbance spectra. Photoluminescence investigations of the phosphors are done. The critical quenching concentrations of the phosphor are found to be x = 0.01; and y = 0.04. Moreover, the critical distance of energy shift with the adjacently presented ions is computed. Dexter’s theory is employed to elucidate that the dipole-dipole electronic interactions are the imperative reasons for the transfer of energy in the phosphor. The white color of emission is achieved for x = 0.01, y = 0.04 Tb, and Sm doped CaWO4 material. Moreover, great values in color purity, correlated color temperature, color rendering index as well as luminous efficiency of radiation are obtained from the CIE Chromaticity coordinates. Quantum yield efficiency of x = 0.01, y = 0.04 Tb & Sm codoped CaWO4 is measured. Photoluminescence decay analysis of all the samples is done to study the long-after glow properties and also the average lifetime values are evaluated. This is an indication of the suitable usage of the prepared materials in the white light-emitting diodes. Concentration as well as dose-dependent Thermoluminescence spectroscopy is investigated thoroughly. Kinetic parameters are calculated by deconvoluting the spectra of x = 0.01; y = 0.01 Tb & Sm codoped CaWO4 irradiated with 15 min of UV excitation dose. These results are denoted by high trap depth, second-order kinetics, and low UV dosimetry of the phosphor.

Super long ultraviolet-A persistent luminescence and photo-stimulated luminescence from CaMgGeO4: Bi3+

Here, we have developed a novel ultra long ultraviolet-A afterglow material CaMgGeO4: Bi3+, which shows more than 24 h UVA afterglow emission peaked at 346 nm. The crystal structure shows that the prepared sample is a pure phase with an orthogonal system of Pmnb space group. The composition of valence band and conduction band was analyzed by the density of states, which reveals that the bandgap of the CaMgGeO4 matrix is 3.69 eV. The photoluminescence spectrum of the sample consists of a broadband in the 320–400 nm UVA region, which belongs to the 3P1 → 1S0 electron transition of Bi3+. More importantly, under the excitation of ultraviolet lamp for 3 min, CaMgGeO4: Bi3+ exhibited an UVA ultra long persistent luminescence (LPL) with a duration of more than 24 h, which afterglow emission intensity still reaches 1500 cps and is about 6 times of the background intensity. In addition, the UVA emission of CaMgGeO4: Bi3+ after 13 h day can be repeatedly by short periods of low-energy light sources stimulation. The thermoluminescence analysis indicates that the presence of shallow and deep traps is responsible for excellent UVA-LPL and photo-stimulate luminescence (PSL). The excellent LPL and PSL properties can prompt CaMgGeO4: Bi3+ phosphor to be widely used in the field of photodynamic therapy.

Highly efficient mechanoluminescence of SrAl2–xYxO4:Eu2+,Dy3+ via trap regulation for dynamic signature anticounterfeiting

Mechanoluminescence (ML) materials have shown tremendous application potential due to their luminescent properties stimulated by mechanical energy. Owing to the narrow awareness of alterations in the crystal field environment of materials, the ML performance optimization is severely restricted. Here, a novel strategy of doping Y3+ into SrAl2O4:Eu2+,Dy3+ phosphors was employed by solid-phase reaction, significantly improving the ML performance. Based on analysis of structure and luminescent properties, it is proved that Y3+ occupies Al3+ sites, causing lattice expansion and crystal field distortion, altering trap engineering, strengthening carrier de-trapping ability, and improving ML performance. Through thermoluminescence (TL) analysis, the brighter ML behavior can be attributed to the carriers re-combination generated by high-density deep traps of 0.836 eV and above. Materials were also investigated in relation to pressure, stability and repeatability and conducive to achieving dynamic anticounterfeiting of personal signature. This study also provides more evidence that doping ions is an efficient tactic for greatly enhancing ML performance.

Effects of UVC irradiation on polystyrene for healthcare packaging: Study by FTIR and Raman spectroscopy with thermoluminescence

The interaction between ultraviolet C radiation (UVC) and polystyrene (PS) materials has been investigated, particularly in post-packaging irradiation processes for healthcare applications. Effective UVC penetration through PS materials, regardless of their thickness (0.16 and 0.40 mm) has been observed. However, the penetration effectiveness could be affected by the thickness of the PS material. Achieving optimal post-packaging UVC treatment requires a thorough evaluation of chemical composition and material thickness, especially in pharmaceutical and medical packaging industries.Preliminary results reveal minimal degradation in UVC-irradiated PS packaging samples, as supported by FTIR and Raman spectroscopy characterization. Minor variations could be attributed to intrinsic PS materials properties and/or their respective background, rather than the influence of UVC radiation. Consequently, PS materials exhibit resilience under the experimental conditions following UVC irradiation treatment. Furthermore, a comprehensive analysis of thermoluminescence (TL) emissions evaluates several commercial dosimeter materials for UVC radiation detection. The TLD-100 and TLD-200 dosimeters show potential as UVC detectors, displaying distinct responses linked to the non-ionizing component of UVC radiation at 310 °C and in the range of 150–250 °C, respectively. However, the TLD-400 and GR-200 dosimeters are not suitable for UVC detection due to their spread TL emissions considering intensity and curve shape.This UVC-TL analysis consistently detects radiation in the proposed commercial dosimeter materials one-hour post-exposure, providing assurance that healthcare materials have been irradiated. Such analysis enhances reliability during extended UVC exposures, offering valuable insights for industries employing UVC-irradiated materials, particularly in healthcare applications.

Multicolor-emitting Er3+ and Er3+/Yb3+ doped Zn2GeO4 phosphors combining static and dynamic identifications for advanced anti-counterfeiting application

Anti-counterfeiting labels based on luminescence materials are a newly emerging technique for protecting legal goods and intellectual property. In the anti-counterfeiting field to prevent forgery and cloning, luminescence materials with properties different from the commercialized and traditional ones are in urgent need. In this work, multicolor-emitting Er3+ single-doped and Er3+/Yb3+ co-doped Zn2GeO4 phosphors combining static and dynamic identifications were developed in order to achieve advanced anti-counterfeiting application. The variation of trap content with increasing the doping content of rare earth ions was analyzed through X − ray photoelectron spectroscopy, thermoluminescence analysis. It was found that there are two types of traps with different depth in Zn2GeO4 phosphors. The depths of the traps were experimentally confirmed to be 0.68 and 0.79 eV, respectively. The transient photocurrent response measurement confirmed the existence of charge carriers, and the mechanism for long persistent luminescence was deduced. The multicolor upconversion mechanisms under 980 and 1550 nm excitation were also discovered. Based on the multicolor steady and transient emission features, an anti-counterfeiting pattern was designed using the phosphors. Static and dynamic identification was demonstrated and presented in detail. Finally, it is indicated that the studied phosphors are excellent candidates for potential applications in luminescence anti-counterfeiting labels.

Thermoluminescence studies of Pakistani limestone pellets for X-rays

The quest to identify low-cost thermoluminescence (TL) materials is vital, and the identification and assessment of natural materials suitable for radiation detection is a rapidly growing area of research. In addition to their specific dosimetric characteristics, such materials must be rigid, insoluble, and chemically inert. One such promising low-cost material can be a limestone having vast deposits in Pakistan. The present study reports the TL and dosimetric features of Pakistani limestone pellets and their comparison with TLD-100.The quarried crystalline limestone rock was hand crushed, sieved, and compressed into the standard TLD chip-sized pellets. The TL response, kinetic parameters, batch homogeneity, dose linearity, individual sensitivity correction factor (i.e., elemental correction coefficient ECC), lowest detectable dose limit (LDDL), coefficient of variation (COV), energy dependency, and fading were determined, and compared with TLD-100. For TL analysis, the pellets were exposed to an 8 Gy dose of 250 kVp X-rays. These exhibited complex TL showing four peaks (P1: 90–110 °C, P2: 130–170 °C, P3: 240–280 °C and P4: 320–350 °C). The limestone response was linear in the studied dose range of X-rays (1–10 Gy), unlike the supra-linear behavior of TLD-100. The kinetic parameters (i.e., the frequency factor (f), activation energy (E), and the kinetic order (b)) were estimated through computerized glow curve deconvolution using the general order of kinetics while confirmed by the Tm-Tstop method. The values of E and f were observed in the ranges of 0.85–1.27 eV and 5.98 × 107 to 1.81 × 1013 s−1, respectively. The calculated value of figure-of-merit (FOM) (i.e., 2.37%) showed a good agreement between the experimental and fitted glow curves. The overall variation in the ECCs for TLD-100 and limestone was found within ±4% and ±7%, respectively. The results of the ECC confirmed batch homogeneity. The calculated value of LDDL was ∼1.01 Gy. The investigation found that the maximum variation in normalized intensity and COV was within the tolerance limit of 5%. The limestone pellets showed less sensitivity than TLD-100. Like TLD-100 at high energy, the pellets showed an independent response. In contrast to TLD-100, the limestone pellets showed a higher response dependency for low-energy X-rays.During the fading study, the total TL intensity decreased by 20% within the initial 24 h of irradiation and then sustained stability for the subsequent week. The results of this study indicate that limestone pellets are effective as an X-ray dosimeter for doses between 1 and 10 Gy.

Quasi‐Continuous Defect Levels in Broadband Gap: A New Strategy for High‐Temperature Long Persistent Luminescence Materials

AbstractLong persistent luminescence (LPL) materials widely employed in the fields of emergency lighting and anti‐counterfeiting are mostly used at room temperature. As temperatures rise, the performance of LPL materials deteriorates dramatically, which hinders their application in in vivo imaging, high‐temperature display, and information storage. Herein, a multifunctional material LiGa5O8:Tb3+ (LGT) with green high‐temperature LPL (HT‐LPL) and blue cathodoluminescence (CL) is reported. Its LPL performance is anomalously enhanced with increasing temperature, and the duration time is more than 8 h at 423 K. With combined temperature‐dependent decay curves and thermoluminescence analyses, the unique quasi‐continuous defect levels are found in the band gap. The high‐concentration carriers in deep traps are frozen at room temperature and activated only at high temperatures, accompanied by changes in energy transfer pathways. The excellent HT‐LPL makes LGT a light‐emitting component of next‐generation smart wearable devices, as well as high‐temperature warning equipment in deep well exploration at a depth of 4500 m. The intense anti‐degradation blue CL makes it suitable for field emission displays, while the manipulable emission property makes it suitable for high‐level anti‐counterfeiting. This study fills a gap in HT‐LPL materials and opens up a new gateway for the efficient design of HT‐LPL and other multifunctional materials.

Thermoluminescence studies of NaMgF3:Tb for gamma dosimetry applications

NaMgF3 is a recognized sensitive thermoluminescence (TL) dosimeter but it shows fading at room temperature which limits its use as a radiation dosimeter. It is important to improve this parameter of NaMgF3 for its potential application in the field of radiation dosimetry. Thus, the current work focuses on enhancing the dosimetric properties of NaMgF3 exclusively the TL fading characteristics. In the present study, Tb doped NaMgF3 has been synthesized by two different methods i.e. solid state reaction method (SSR) and melting method (MT). A comparative and detailed TL studies have been carried out after irradiation with gamma rays which has not been reported so far. Detailed analysis of TL and Photoluminescence (PL) properties reveal that NaMgF3:Tb prepared via MT shows good luminescence properties in comparison to SSR and previously reported results. Thus, Tb doped NaMgF3 synthesized by melting method can be a potential dosimeter for the detection of gamma rays.

Multicolor Mechanoluminescence in Sr2Ga2GeO7: Pr3+ for Stress Sensing and Anticounterfeiting

AbstractMechanical luminescence (ML) is the conversion of mechanical energy into light energy when a material is subjected to a force. It is challenging to develop ML materials with tunable luminescent properties by single ion doping, which have broad application prospects in the fields of stress sensing and dynamic signature anticounterfeiting. In this study, a Pr3+ doped Sr2Ga2GeO7 tunable ML material is reported. Due to the traps resulting from unequal substitution of Pr3+–Sr2+ in [SrO6] heptahedra, the deep/shallow traps redistribution occurs towards a multicolor ML from red to green. In addition, even after continuous friction sliding force (15 N), the ML intensities can be recovered after ultraviolet pre‐irradiation, indicating that Sr2Ga2GeO7: Pr3+ has excellent ML emission stability. Based on thermoluminescence analysis, potential PersL and ML mechanisms are further elaborated by a lattice engineering (trap regulation) strategy. In all, the development of single‐ion doped multicolor ML materials may have crucial research value and show a variety of potential applications in the fields of anticounterfeiting and information encryption.

Luminescence characteristics of white light emitting BaGa2O4:Dy3+ phosphors for LEDs and stress sensing applications

A series of single-phase white-light-emitting BaGa2O4:xDy3+(x = 0.1,0.3,0.5,0.7,1) phosphors have been synthesised using solid-state reaction technique. The structural studies using the X-ray diffraction (XRD) technique indicate that the phosphors are single-phase and Scanning Electron Microscope (SEM) study reveals that the particle size is in micrometer range. The phosphors emit white light with peaks at 346 nm, 357 nm, 386 nm, and 426 nm generated by Dy3+ ion transitions (6H15/2 → 6P7/2), (6H15/2 → 6P9/2), (6H15/2 → 4F7/2+4I13/2) and (6H15/2 → 4G11/2). The colour coordinates calculated for BaGa2O4:xDy3+ (x = 0.5,0.7) phosphors are identical to the conventional white light. BaGa2O4:Dy3+ exhibits good Mechanoluminescence (ML) response at varied impact velocities for both unirradiated and gamma-irradiated samples. This characteristic is reasonably beneficial in the development of damage and pressure sensors. Thermoluminescence (TL) analysis shows a single glow curve of similar shape irrespective of increasing irradiation, and the TL parameters have been calculated.

First Evidence of Electron Trapped Ln2+ Promoting Afterglow on Eu2+, Ln3+ Activated Persistent Phosphor‐Example of BaZrSi3O9:Eu2+, Sm3+

AbstractBaZrSi3O9:Eu2+, Sm3+ (Em:525 nm) is prepared. The role played by the trivalent co‐doping ion Sm3+ in the afterglow and the type of trap are clarified. BaZrSi3O9:Eu2+, Sm3+ is found to produce Sm2+ during the excitation by X‐ray absorption near‐edge structure (XANES), etc., and it is thus proved that Sm3+ exists as an electron trap in the afterglow process. In the field of persistent phosphors activated by Eu2+ and Re3+ such as Sm3+ or Dy3+ having been widely utilized as emergency guide lights, clock faces, etc. for > 25 years, for the first time it is successfully observed that after excitation Re2+ is formed, transferring its electron to 5d band of Eu2+, returning to Re3+ by itself, where the decrease in Sm2+ coincides with the increase in Sm3+, and the two decay time τ1 and τ2 of PL (5D0→7F0) of Sm2+ coincides with the two evolution time of PL (5d→4f) of Eu2+. The behavior of electron transfer from Sm2+ to Eu2+ as a key of afterglow is detected. The detailed afterglow mechanism is proposed by analysis of thermoluminescence and defect reaction, which is very important for the in‐depth investigation of the long afterglow material and the further improvement of the mechanism.

Highly efficient yellow emission and abnormal thermal quenching in Mn2+-doped Rb4CdCl6.

In this paper, Mn2+-doped Rb4CdCl6 metal halide single crystals were prepared by a hydrothermal method. The Rb4CdCl6:Mn2+ metal halide exhibits yellow emission with photoluminescence quantum yields (PLQY) as high as 88%. Due to the thermally induced electron detrapping, Rb4CdCl6:Mn2+ also displays good anti-thermal quenching (ATQ) behavior with thermal quenching resistance (131% at 220 °C). The increase in the photoionization and the detrapping of the captured electrons from the shallow trap states were appropriately attributed to this exceptional phenomenon based on thermoluminescence (TL) analysis and density functional theory (DFT) calculations. The relationship between the fluorescence intensity ratio (FIR) of the material and temperature change was further explored using the temperature-dependent fluorescence spectrum. It was used as a temperature measuring probe based on absolute sensitivity (Sa) and relative sensitivity (Sb) with the change in temperature. The phosphor-converted white light emitting diodes (pc-WLEDs) were fabricated using a 460 nm blue chip with a yellow phosphor, which has a color rendering index (CRI = 83.5) and a low correlated color temperature (CCT = 3531 K). Because of this, finding new metal halides with ATQ behavior for high-power optoelectronic applications may be made possible by our findings.

Influences of gamma irradiation on structural, morphological and luminescence characteristics of Nb doped TiO2 nanophosphors

The irradiation induced effects on structural, morphological and luminescence characteristics of Nb:TiO2 phosphors were systematically investigated. Possible defect centers present in the Nb:TiO2 phosphors were also characterized. Anatase phase of TiO2 with minor parasitic Nb-containing phases was specified in crystallographic structure of phosphors. Crystalline size and internal stress enhance with enhancing the exposed dose. The observed rise in the crystalline size was also confirmed in morphological evolution. Moreover, the Nb:TiO2 phosphor exhibits five different photoluminescence peaks. Intensity variations and blue-green–red shifts on the PL peaks were observed after irradiation exposures. Similarly, various trap sites/centers with depth energies between 1.09 eV and 1.99 eV were found in the thermoluminescence analysis. The irradiation exposures both enhance the oxygen vacancies and cation interstitial defects in the structure. The results have depicted that gamma exposure significantly affects the crystallographic and luminescence features of the Nb:TiO2 nanophosphors.

X-ray-activated long afterglow in Tb-doped CaZnOS-layered semiconductors

Long afterglow materials feature long-lasting luminescence after the cessation of the excitation source. The rising demand for afterglow materials in many applications such as deep tissue imaging, ultrasensitive sensing, and radiation detection has led to extensive research on X-ray-activated afterglow systems. However, the progress in this field is constrained by the limitation and shortage of radiation-induced afterglow materials. Herein, a newly X-ray-excited long afterglow phosphor CaZnOS:Tb3+ has been developed by using lithium-assisted synthetic protocol. Afterglow properties of Tb3+-doped CaZnOS microcrystals are systematically investigated by considering the dopant concentration, reaction temperature, reaction time, reaction atmosphere, and gas flow. As the gas flow of argon atmosphere increases from 0.05 to 0.5 L/min, the CaZnOS:Tb3+ microcrystals exhibit a distinct change in trap depth from 0.59 to 0.75 eV, corresponding to a gradual increase in afterglow time. Together with thermoluminescence analysis, the long afterglow mechanism is also discussed in this work. These results highlight the importance of reaction gas flow for the efficient regulation of traps and defects in afterglow materials. Furthermore, they provide a fundamental design principle and new route for the creation of lanthanide-doped CaZnOS afterglow phosphors.

TL and OSL as research tools in luminescence: Possibilities and limitations

The objective of this paper is to review the use of the thermoluminescence (TL) and optically stimulated luminescence (OSL) techniques as research tools in luminescence, particularly to detect the presence of trapping centers that can degrade the efficiency of scintillators, and shape the properties of persistent phosphors, storage phosphors and dosimeters. A brief review of the main analysis techniques is provided, followed by a discussion of their limitations. Examples of applications in which the TL or OSL analyses have provided useful information on the trapping and recombination of charges created by ionizing radiation is given.

Deep-red to NIR mechanoluminescence in centrosymmetric perovskite MgGeO3: Mn2+ for potential dynamic signature anti-counterfeiting

Developing deep-red to near infrared (NIR) materials with multi-mode luminescence is challenging, which has promising utilization in various applications such as stress sensing and dynamic signature anti-counterfeiting. Different to the mainstream non-centrosymmetric mechanoluminescence (ML), a centrosymmetric perovskite compound (MgGeO3: Mn2+) ML material is reported. Deep-red to NIR light (600–800 nm) from Mn2+ ion is confirmed, which is attributed to the strong crystal field within the [MgO6] polyhedron. The stiffness tetrahedral units and large defect accommodating space within the host are favorable for both ML and persistent luminescence (PersL). Mn2+ ion is the only luminescent center, which is confirmed by spectral characterizations. Based on diffuse reflectance spectra, thermoluminescence analysis and density functional theory calculations, the inherent relationship between PersL, ML and PL is further clarified in detail. Due to the formation of MnMg defects, shallow trap significantly become shallower after adding Mn2+ ions. This study reports a Mn2+-doped deep-red to NIR ML phosphor, and further describes the PersL and ML mechanisms via defect engineering regulation. In general, this study may also open up a new approach for the development of efficient NIR ML materials, and show various potential applications such as in anti-counterfeiting and information encryption fields.