Thermally Stimulated Luminescence Research Articles

Effect of IRSL-BLSL-TSL reading modes combination on thermoluminescence (TL) response of BeO dosimeter.

The ultimate goal of this work is the study of the effect of luminescence stimulations and signals reading modes combinations on the thermoluminescence intensity and glow curve behaviour for the same X-ray irradiation dose. Three interesting stimulating and reading modes are considered, namely, infrared stimulated luminescence (IRSL), blue light-emitting diode stimulated luminescence (BLSL) and thermally stimulated luminescence (TSL). The studied stimulation and reading modes combination protocols are (Protocol 1) IRSL-TSL, (Protocol 2) IRSL-BLSL-TSL and (Protocol 3) BLSL-IRSL-TSL. Experiments are performed on beryllium oxide (BeO) dosimeter. Results demonstrate well that the combination of reading modes have direct impact on the TL signal in terms of intensity and glow curve shape. It was also found that when reading modes are correctly combined, particularly when IRSL is applied first, then BLSL and TL, it is possible to collect two or more exploitable signals of different stimulation types for the same irradiation that can be used for different purposes and final applications.

Electron paramagnetic resonance and luminescence spectroscopy of transition metal ion impurities and X-ray-induced radicals in brushite

Calcium phosphates hold paramount importance as the constituents of hard tissue of living organisms. Among them, brushite (CaHPO4·2H2O), also known as dicalcium phosphate dihydrate (DCPD), is a common precursor in phosphate synthesis and is becoming increasingly appealing as a biomaterial for bone regeneration applications. This study presents a comparative analysis of structural, morphological, thermal, and spectroscopic properties of synthetic brushite prepared by the wet precipitation method with several brushite products available from commercial vendors. Electron paramagnetic resonance (EPR) spectroscopy revealed that Mn2+ and Fe3+ ions are common trace impurities in commercial products. Following exposure to X-rays, EPR signals of several phosphorous-related radicals emerge. The annealing of the irradiated samples gives rise to broad thermally stimulated luminescence (TSL) signals in the 40-120 °C range, which correlates with the annealing kinetics of the radicals. The stability of radiation-induced EPR and TSL signals is limited by the phase transformation temperature from brushite to monetite (CaHPO4). The results of this study provide novel insights into the formation and stability of phosphorous-related radicals and demonstrate how minuscule amounts of impurity ions can strongly influence the spectroscopic properties of brushite.

Optical, scintillation, and TSL properties of Ce-doped LiMgAlF6

Ce differently (0, 0.01, 0.1, 1, 2 and 5% with respect to Mg) doped LiMgAlF6 ceramics were synthesized by the spark plasma sintering (SPS) method. In photoluminescence (PL), emission bands appeared at 300 nm with 30 ns day time, and these emission properties were almost the same in scintillation under X-ray irradiation. Further, thermally stimulated luminescence (TSL) was observed after X-ray irradiation, and the primary glow peak temperature was 160 °C with a lower detection limit of ∼10 mGy.

Photoluminescence and thermally stimulated luminescence properties of undoped and Tb-doped Sr3Gd(PO4)3 single crystals

Using the floating zone method, undoped and 0.5, 1, and 5% Tb-doped Sr3Gd(PO4)3 (SGPO) single crystals were synthesized. Investigations were conducted on the photoluminescence (PL) and thermally stimulated luminescence (TSL) of all the SGPO single crystals. The highest PL quantum yield was shown in the 5% Tb-doped single crystal among the synthesized SGPO single crystals. The undoped SGPO single crystal displayed an emission peak in both TSL and PL at 310 nm owing to the Gd3+ 4f–4f transition. In the Tb-doped SGPO single crystals, emission peaks in PL and TSL at 310–620 nm were caused by the 4f–4f transitions of Tb3+ in addition to Gd3+. In the TSL dose response function, the 1% Tb-doped SGPO single crystal exhibited the highest TSL intensity, and the TSL signal could be detected at least 0.01 mGy.

Thermally stimulated luminescence properties of Mn-doped MgAl2O4 translucent ceramics

MgAl2O4 translucent ceramics doped with Mn were fabricated by spark plasma sintering, and optical and dosimetric properties were evaluated. The 1% Mn-doped MgAl2O4 translucent ceramic exhibited a photoluminescence emission peak at 520 nm due to Mn2+. Thermally stimulated luminescence (TSL) glow peaks of the Mn-doped MgAl2O4 translucent ceramics were observed at around 60 and 260 °C. Moreover, the TSL intensity increased as the heating temperature rose to 490 °C. TSL spectra confirmed that Mn2+ had a role of recombination centers in the TSL process. The 0.01% Mn-doped MgAl2O4 translucent ceramic showed a proportional relationship between the TSL intensity and irradiation doses ranging from 0.1 to 1000 mGy.

Trap properties of novel UV-A persistent phosphor Sr3MgSi2O8:Ce3+

For the last few decades, there has been extensive research on the materials that persist to emit optical radiation long after any type of charging has stopped. Most of the established persistent luminescence (PersL) materials emit light in the visible part of the spectrum; however, in recent years, there has been a growing interest in UV-emitting persistent phosphors in recent years. These materials have been tested for various applications, such as photocatalysis, sterilization, and anti-counterfeiting, among others. Here, we report on the X-ray and UV-activated UV-A long PersL of Ce3+-doped Sr3MgSi2O8 material. We prepared samples with varied Ce3+ concentrations using solid–state reaction synthesis in an ambient atmosphere and conducted a thorough investigation using photoluminescence (PL), electron paramagnetic resonance (EPR), and thermally stimulated luminescence (TSL) spectroscopy methods. Our experiments show that the PersL signal of Ce3+ in the 300–450 nm range can be detected for at least 16 h when samples are irradiated with X-rays or UV. The TSL analysis reveals multiple discrete charge traps in the material with activation energies between 0.5 and 1.7 eV. Further EPR measurements confirm the presence of four paramagnetic centers. The thermal stability of these centers was analyzed, and it is established that one of these centers (g1 = 2.0056, g2 = 1.9981, and g3 = 1.9926) gradually decays at room temperature, which is correlated with the PersL processes.

Thermally Stimulated Luminescence in ZnSe:Ag and ZnSe:(Ag, Gd) Phosphors

AbstractWith a view to understanding the luminescence mechanism in ZnSe, a systematic study of thermally stimulated luminescence (TSL) of UV ray (3650 Å) irradiated ZnSe:Ag and ZnSe:(Ag, Gd) phosphors has been undertaken. TSL glow curves of these phosphors are recorded in the temperature range 110–340 K. The TSL parameters like trap depth, frequency factor, order of kinetics, and capture cross‐section of the glow peaks are evaluated employing Cutie's method, various heating method, and peak shape method.

X-ray assisted point defects creation in micron-size Zn, Mo oxide particles at liquid nitrogen temperature

Charge trapping processes induced by the X-ray irradiation in the heavy Mo doped ZnO and MoO3 micropowders synthesized by the hydrothermal growth method were investigated in detail. Electron paramagnetic resonance (EPR) and thermally stimulated luminescence (TSL) were applied in a correlated manner to discover the role of the Mo doping in the charge trapping processes in ZnO. Thermally unstable oxygen- and molybdenum-related charge trapping centers were studied. Molybdenum and oxygen created electron-hole trapping pairs in some cases were observed. Some part of the hole trapping centers seemed to be directly connected with the creation of Mo5+. The correlation between EPR and TSL data was found.

X-ray-induced luminescence properties of Na3AlF6 doped with TmF3

Tm-doped Na3AlF6 ceramics were prepared by the spark plasma sintering (SPS) method with different Tm concentrations (0.01, 0.1, 1, 3, 5 %), and optically-stimulated luminescence (OSL) and thermally-stimulated luminescence (TSL) were investigated. In the OSL properties, emission peaks were observed at 300 and 350 nm under 500 nm stimulation due to 4f-4f transitions of Tm3+. The 0.1, 1, and 3 % Tm-doped samples indicated a dose response linearity between 100 mGy and 10 Gy. The TSL glow peaks of Tm-doped samples were detected at 80, 120, 300, and 410 °C. The 0.1, 1, and 3 % Tm-doped samples indicated a dose response linearity over the range of 0.01–1000 mGy at dose response functions.

Dosimetric properties of Eu-doped Ca2BO3Cl

We prepared Ca2BO3Cl with different concentrations (0.1 %, 0.5 %, and 1.0 %) of Eu2O3 for radiation dosimetry. Sharp photoluminescence peaks derived from 4f → 4f transition of Eu3+ appeared at 575, 590, 610, and 645 nm. On the other hand, the Eu2O3-doped Ca2BO3Cl exhibited a broad scintillation peak at around 600 nm due to 5d → 4f transition of Eu2+, and sharp peaks at approximately 590 and 610 nm derived from 4f → 4f transition of Eu3+. Furthermore, a major thermally-stimulated luminescence glow peak was detected at 250 °C, and a linear response in the range of 1–3000 mGy was observed from the Eu2O3-doped Ca2BO3Cl.

New emission band of solid nitrogen

New results on the study of radiation effects in solid nitrogen and N2-doped Ne matrix are presented, with a focus on the so-called γ-line origin. The irradiation was carried out in dc regime with an electron beam of subthreshold energy. The relaxation dynamics was monitored by emission spectroscopy: cathodoluminescence (CL) and nonstationary luminescence (NsL), along with current activation spectroscopy. Thermally stimulated luminescence (TSL) and exoelectron emission (TSEE) of pure nitrogen and N2 in the Ne matrix were measured in a correlated manner. Three emission bands were recorded in the NIR CL spectra of solid N2: 794, 802, and 810 nm. The band at 810 nm was detected for the first time. These three bands are characterized by similar behavior and form molecular series with spacing between adjacent vibrational energy levels of the ground state of 125 and 123 cm−1. These data cast doubt on the recently made assumption that the γ-line is attributed to the emission of the nitrogen anion N− [R. E. Boltnev, I. B. Bykhalo, I. N. Krushinskaya et al. Phys. Chem. Chem. Phys. 18, 16013 (2016)]. The processes of electron attachment and neutralization of positively charged species are discussed. It has been established that the γ-line in the TSL spectra of pure nitrogen and N2-doped Ne matrix correlates with TSEE currents and recombination emission of O+, N2+, and N4+ ions, which indicates its connection with the neutralization reaction. The measurement of NsL supported this conclusion. A new possible assignment of the γ-line and its satellites to the emission of tetranitrogen N4 is discussed.

Photoluminescence, scintillation, and TSL properties of Dy-doped BaCaBO3F

We fabricated BaCaBO3F (BCBF) with various Dy concentrations (0.1 %, 1 %, and 5 %), and evaluated the luminescence properties for radiation dosimetry. Sharp scintillation peaks originating from the 4f → 4f transition of Dy3+ were observed. Furthermore, thermally stimulated luminescence (TSL) glow curves were recorded, and a TSL glow peak at approximately 120 °C was observed. The 0.1 % Dy-doped BCBF exhibited the highest TSL intensity, and dose response curves of the 0.1–1 % Dy-doped BCBF were obtained in the 0.1–10000 mGy range. Moreover, at least seven activation energy levels related to TSL were confirmed by the TSL isothermal decay analysis.

Dosimetric properties of Tm2O3-doped Ca2BO3Cl

In this work, we prepared Ca2BO3Cl with various amounts (0.1%–1.0%) of Tm2O3 by conventional solid-state reaction and investigated the dosimeter properties. Scintillation peaks at 370, 455, 470, and 650 nm that were derived from the 4f→4f transition of Tm3+ appeared in the X-ray induced scintillation spectra, and the highest scintillation intensity was detected from the 0.5% Tm2O3-doped Ca2BO3Cl. Furthermore, the Tm2O3-doped Ca2BO3Cl exhibited a thermally-stimulated luminescence (TSL) with a main glow peak at 300 °C, and the fabricated Tm2O3-doped Ca2BO3Cl exhibited a linear response in the 0.1–1000 mGy range. In addition, the TSL spectra confirmed that a final luminescence process for the TSL was the 4f→4f transition of Tm3+. In addition to TSL, optically-stimulated luminescence that was attributable to the 4f→4f transition of Tm3+ was recorded under 520 nm light, and the lowest detectable limit was about 1 mGy.

Comparative study of optical and dosimetric properties of Mn-doped CaF2

Mn-doped CaF2 has been used as a thermoluminescence detector. On the other hand, dosimetric properties of Mn-doped CaF2 transparent ceramics have not been thoroughly investigated. In this study, transparent ceramics (TC) of Mn-doped CaF2 were fabricated, and the optical and thermally stimulated luminescence (TSL) properties were investigated in comparison with Mn-doped CaF2 single crystal (SC) and opaque ceramics (Cer). The transmittance at 500 nm of the TC, SC, and Cer specimens was 58, 91, and 0%, respectively. All the specimens showed a PL peak at 490 nm with 340, 400, and 450 nm excitations, originating from d-d transitions of Mn2+ ions. The emission and excitation spectra changed with X-ray irradiation, and this phenomenon was attributed to optically stimulated luminescence. All the specimens mainly had a TSL glow peak at 300 °C. The TC specimen exhibited a higher TSL intensity than the SC and Cer specimens.

Photoluminescence, scintillation, and dosimetric properties of undoped and Tb-doped Ba3Gd(PO4)3 single crystals

Undoped and Tb-doped Ba3Gd(PO4)3 single crystals were synthesized by the floating zone method. Photoluminescence (PL), scintillation, and thermally stimulated luminescence (TSL) properties of the obtained single crystals were evaluated. The highest PL quantum yield value was obtained from the 5% Tb-doped single crystal. In X-ray-induced scintillation and TSL spectra, the undoped sample represented an emission peak originating from the 4f–4f transition of Gd3+ at 310 nm. The Tb-doped samples represented emission peaks originating from the 4f–4f transitions of Tb3+ and Gd3+ in the range of 310–620 nm. In TSL dose response functions, the 1% Tb-doped sample showed the highest TSL intensity, and the lower detection limit was 0.01 mGy.

Effect of Al-doping on dosimetric properties of CaF2

In this study, the effect of Al-doping on dosimetric properties of CaF2 was investigated. Al-doped CaF2 showed a radiophotoluminescence (RPL) peak at 750 nm after X-ray irradiation. The RPL intensity decreased with the increase of Al concentration and was less than that of undoped CaF2. The minimum detectable dose as the RPL dosimeter of 0.01% Al-doped CaF2 was 42 mGy. Al-doped CaF2 also indicated thermally stimulated luminescence (TSL) glow peaks at 225, 285, 387, and 436 °C. The wavelengths of TSL were 390 and 500 nm. The minimum detectable dose as the TSL dosimeter of 1% Al-doped CaF2 turned out to be 0.43 μGy which is comparable to commercial dosimeters.

Activation mechanisms of recombination processes in irradiated poly(arylenephthalides)

The recombination of separated ion-radical states (SIRS) in poly(arylenephthalide) (PAPh) films accompanied by emission of light with a maximum of ∼ 500 nm has been analyzed. The density functional theory methods [PBE1PBE/6-311+G(d,p)] and mathematical modeling were used for description of thermally stimulated luminescence (TSL) kinetics of PAPh. The versatility of the earlier proposed three-step kinetic model of metastable (X) and labile (Y) SIRS recombination was demonstrated on the example of various cardo polymers. The contribution of X-SIRS recombination to total luminescence was found to be characterized by the vanishingly small intensity in a vacuum and moderate and maximum one in inert gases and an oxygen-containing medium, respectively. It was found out that the recombination of labile SIRS does not depend on the nature of the atmosphere. It was theoretically substantiated that SIRS recombination can proceed via the transfer of both positive and negative charges. It was shown that the key factor determining the efficiency of thermal activation of recombination processes is the ratio of radiant and conductive channels of energy transfer from the heating element to the polymer sample.

Radiation response properties of Ce-doped CaF2 transparent ceramics

We report on the luminescence properties of CaF2 transparent ceramics having various concentrations of CeF3 (0.1 %, 0.5 %, and 1 %). Scintillation emissions centered at approximately 318, 345, and 386 nm derived from the 5d→4f transition of Ce3+ were detected, and scintillation light yields were determined to be 8600 photons/MeV (0.1 % CeF3), 1930 photons/MeV (0.5 % CeF3), and 1850 photons/MeV (1 % CeF3) under gamma-ray irradiation from 241Am. The Ce-doped CaF2 transparent ceramics showed thermally stimulated luminescence (TSL) with a broad glow peak at around 115–145 °C, and their dose response curves were determined over a broad dose range (0.01–3 mGy). Moreover, optically stimulated luminescence (OSL) exponential decay curves were obtained under 500 nm stimulation light, and dose response curves were obtained in the dose range of 0.1–100 mGy. The minimum detectable dose was estimated to be 0.1 mGy. A direct correlation between scintillation light yields under gamma-ray irradiation and TSL/OSL intensities was demonstrated.

Tailoring trap distribution via metal cation substitution in SrxBa1-xSi2O2N2 lattices for multicolor and multimodal dynamic information encryption strategy

Traditional anti-counterfeiting technology based on fluorescent materials is usually single-color emission and far from enough to meet the growing demand for anti-counterfeiting with high-level security. Here, dual luminescent centers with blue emission at 470 nm and green-yellow emission at 546 nm have been successfully achieved by controlling the Eu2+ sites in the SrxBa1-xSi2O2N2 (x = 0.25–0.50) host lattices via fine-tuning of Sr contents (x). Notably, Sr0.50Ba0.50Si2O2N2: 0.02Eu2+ exhibits particular optical information storage properties with intense yellow emission and can repeat the corresponding image patterns under the thermal stimulus, which can be regarded as an essential candidate in multicolor anti-counterfeiting technology. Further, the different luminescent center-trap center pairings have been found in Sr0.33Ba0.67Si2O2N2: 0.02Eu2+ due to the substitution of Ba2+ and Sr2+ by Eu2+ to generate blue and yellow luminescent centers and the substitution of N3− for O2− in the Sr and Ba lattices resulting in oxygen vacancies. Typically, Sr0.33Ba0.67Si2O2N2: 0.02Eu2+ exhibits a cool white emission in photoluminescence (PL) mode and changes to yellow emission in persistent luminescence (PersL) mode. Moreover, Sr0.33Ba0.67Si2O2N2: 0.02Eu2+ displays a thermochromic phenomenon (from cool white emission to blue emission) in thermally stimulated luminescence (TSL) mode, attributed to the different trap depths in Sr and Ba lattice. Hence, flexible film for optical information storage and patterns for multimodal dynamic anti-counterfeiting are fabricated using Sr0.33Ba0.67Si2O2N2: 0.02Eu2+. Finally, a dynamic optical information encryption and decryption strategy for Morse code is developed based on the different properties of SrxBa1-xSi2O2N2: 0.02Eu2+ (x = 0.25, 0.30, 0.33, and 0.50). The results demonstrate that SrxBa1-xSi2O2N2: 0.02Eu2+ (x = 0.25–0.50) phosphors can be potential candidates in optical information storage and optical anti-counterfeiting applications.

Floating zone growth and evaluation of photoluminescence and dosimetric properties of undoped and Eu-doped Al4SiO8 single crystals

We fabricated undoped and 0.5, 1.0, 2.0, and 3.0% Eu-doped Al4SiO8 single crystals by the floating zone method and analyzed their photoluminescence (PL) and thermally stimulated luminescence (TSL) properties. In PL properties, the undoped sample exhibited an emission band at 460 nm under excitation wavelength at 260 nm. The Eu-doped samples showed an emission band at 410 nm attributed to the 5d-4f transitions of Eu2+ ions. In TSL properties, the undoped sample exhibited TSL glow peaks at 280 and 390 °C, while the Eu-doped samples showed the ones at 230 and 370 °C. The TSL spectra of the Eu-doped samples under heating at 230 °C had an emission band due to the 5d-4f transitions of Eu2+ ions. TSL dose response functions showed a lower detection limit of 10 mGy for the undoped sample, 10 μGy for the 0.5% Eu-doped sample, and 1 μGy for the 1.0, 2.0, and 3.0% Eu-doped samples. The TSL intensity of the 2.0% Eu-doped sample was approximately 72.6% after 11 days from X-ray irradiation compared to immediately after X-ray irradiation.