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We report on the photoluminescence, long persistence luminescence, and thermally and optically stimulated luminescence properties of SrAl2O4:Eu2+,Dy3+ and SrAl2O4:Eu2+,Nd3+ phosphors synthetized by the combustion method and annealed under a carbon atmosphere at 1150 °C for 6 h. XRD indicated the presence of a single monoclinic crystalline phase for both phosphors. After exposure to beta radiation, the phosphors exhibited an intense persistent luminescence lasting more than 220 h. After excitation with 375 nm light the emission spectra depict a broad band peaked at 515 nm, which is the characteristic for Eu2+ emission in SrAl2O4 phosphors, and two weak bands at about 405 and 425 nm. After beta irradiation, the Dy co-doped phosphor exhibits an intense thermoluminescence (TL) with a maximum around 60 °C and a weaker peak at 140 °C. The low temperature TL of the Nd co-doped phosphor consist of three peaks; two well-separated peaks with maxima at about 80 and 160 °C and the third one with the maximum near 50 °C, which becomes evident at doses higher than 10 Gy. Stimulation with IR light of 830 nm releases trapped charges caused by irradiation exposure, generating an intense IR stimulated luminescence (IRSL), which exhibits a typical time decay behavior for continuous wave optically stimulated luminescence. The persistence luminescence and IRSL were related to the release of electrons from the traps responsible for the 60 and 140 °C TL peaks in SrAl2O4:Eu2+,Dy3+ and the 80 and 160 °C TL peaks in SrAl2O4:Eu2+,Nd3+ phosphors, respectively.

The long persistent luminescence, thermoluminescence (TL) and IR stimulated luminescence properties of two orthorhombic strontium aluminates (Sr4Al14O25) co-doped with Eu2+, Dy3+ and Eu2+, Nd3+ exposed to beta radiation is reported. The phosphors were synthesized by the combustion method followed by a post-annealing treatment under a reductive carbon atmosphere. Photoluminescence emission spectra of both phosphors are typical for emission of Eu2+ ions with 7-fold and 10-fold coordination in Sr4Al14025 and consist of the main band at 480 nm and a weak band between 390 and 440 nm. After exposure to beta radiation the Sr4Al14025:Eu2+,Dy3+ phosphor exhibits two strongly overlapped TL peaks at about 70 and 100 °C while the low temperature TL of the Sr4Al14025:Eu2+,Nd3+ phosphor consist of two well separated peaks with maxima at about 60 and 130 °C. Additionally, both phosphors exhibit a weak TL between 180 and 400 °C. The traps responsible for the low temperature TL peaks are the Dy3+ and Nd3+ centers situated in two different Sr sites with 7-fold and 10-fold coordination. The thermal emptying of the Dy and Nd filled traps creates ultra-long intense afterglow, which gradually decays with time and remains detectable after 220 h storage in dark. IR stimulation of beta irradiated phosphors creates intense IR stimulated luminescence, which is related to the release of electrons from the filled Dy and Nd traps.

The present study investigates the structural modification of polydimethylsiloxane (PDMS) with a molecular weight of 35 kDa, using varying high doses of gamma irradiation. Elastomeric structures with different crosslinked density values were obtained as a function of the gamma irradiation dose (250, 300, 350 and 400 kGy). The structural characterization of the obtained elastomers was performed by employing Fourier Transform Infrared, 29Si Magic Angle Spinning Nuclear Magnetic Resonance and X-Ray Diffraction (FTIR, 29Si MAS NMR and XRD), showing integration with the polymer chains by siloxane crosslinks (Type-Y) and methylene crosslinks (Type-H). The mechanical and thermal characterizations were carried out by employing dynamical-mechanical analysis (DMA) and modulated differential scanning calorimetry (MDSC). The results showed an important correlation between the thermo-mechanical behavior and the irradiation dose. The thermal stability, analyzed by a thermo-gravimetric analysis (TGA), exhibited interesting behavior that suggested a direct correlation between the decomposition temperature and the structure generated by the gamma irradiation. These results suggest that the obtained elastomers could potentially be considered shape changing materials (SCM).

In this work, the thermally stimulated luminescence (TSL) and persistent luminescence (PLUM) properties of praseodymium doped yttrium aluminum garnet (YAG:Pr 3+ ) exposed to β-irradiation are reported. X-ray diffraction (XRD) confirms a single phase of YAG obtained by the combustion method. Transmission electron microscopy (TEM) shows that powder particles appear to be irregular crystals with an average size of 67 nm. TSL glow-curve deconvolution of YAG:Pr 3+ after β-irradiation consist in six peaks centered at 394, 450, 467, 543, 637 and 705 K. The TSL fading and PLUM signals were found to be associated with at least with two different kinds of traps, corresponding to the peaks located at 394, 450 and 467 K. YAG:Pr 3+ nanophosphors analyzed in this work showed interesting features about the dosimetric sensitivity as well as the reproducibility for both TSL/PLUM techniques, with good linearity dose response. These results indicate that nanocrystalline YAG:Pr3 + is a good candidate for dosimetric applications in the range of 80 mGy-20 Gy.

Poly(lactic acid) (PLA) is a well-known biodegradable polymer with strong potential application in food packaging industry. In this paper, samples of PLA clamshell for tomatoes packaging were exposed with 60CO γ-ray's source (1.33 MeV) at different dose levels (0, 10, 60, 150, 300, and 600 kGy), at room temperature and in presence of air. The physicochemical properties of neat PLA and sample exposed to gamma irradiation were investigated using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and tensile measurements. Results show as the dose increases, the molecular weight (Mw), melting temperature (Tm), tensile strength and elongation at break decreased. However, the tensile modulus increased with increasing doses. The surface of PLA clamshells was degraded (scratches and minor cracks) when samples were exposed to doses greater than 60 kGy.

Thermoluminescence (TL) properties of gamma-irradiated chemical vapor deposition (CVD) diamond films at high doses are presented. Samples of undoped and nitrogen-doped CVD diamonds were exposed to 60Co gamma sources and TL intensity as a function of the dose was analyzed. To evaluate the feasibility of using these materials as TL high-dose dosimeters, reproducibility of the TL signal, and the TL response as a function of absorbed dose from 100 Gy up to 10 kGy were studied. Furthermore, the fading of the TL glow curve was analyzed. Finally, to estimate the kinetics parameter values associated with the trap distribution in the CVD diamond, a computerized deconvolution was carried out by using the general order kinetics (GOK) model.

We report on the effect of thermal treatments on photoluminescence, thermoluminescence and afterglow of CaAl2O4:Eu2+,Dy3+ synthesized by combustion method and annealed under a carbon atmosphere at 1423 K for 6 h. As synthetized phosphor exhibit a typical Eu2+ emission with a maximum at 438 nm corresponding to the allowed transition from 4f65d to 4f7 levels of Eu2+ ion. The TL glow curves recorded after beta irradiation consist of at least three overlapped TL peaks with maxima at about 340, 410, and 480 K and a high temperature TL with a peak maximum higher than 680 K. Immediately after beta irradiation, intense AG is observed demonstrating the possibility to emit lightfor hours at a level exceeding background signal. The decay curves exhibit two components, fast and slow, due to the liberation of electrons from traps responsible for the 340 and 410 TL peaks with characteristic duration times of about ten seconds and a couple of hours, respectively. The synthesized phosphor was subjected to additional thermal treatments (TTs) in an air atmosphere at 883 and 1183 K for 1h. The TTs lead to a pronounced increase the narrow excitation and emission bands attributable to f – f transitions of the Eu3+ ions and slight changes of the excitation and emission bands corresponding to Eu2+ ions. The effect the TTs on the TL reveals itself in the decrease of the 410 and 480 K TL peaks. On the other hand, the 340 K TL peak does not change under the TTs. The study of TT effects on luminescent properties of calcium aluminate codoped with rare earth is important for understanding the mechanism of trapping and detrapping processes in this phosphor.

Erbium-activated lithium niobate; 1, 2, and 4 mol% (LN-1, LN-2 and LN-4 respectively) were synthesized by solid-state method and their thermoluminescent (TL) properties were analyzed. The glow curve of LN-4 showed a maximum at 177 °C and its linear dose-response interval ranged from 50 to 350 Gy. Its TL intensity was two orders of magnitude greater compared to those of pure lithium niobate (LN), LN-1 and LN-2. We conclude that LN-4 is an interesting material for TL dosimetry applications.

Nanodiamonds (NDs) possess exceptional physical, chemical, and biological properties, which make them suitable for potential biomedical applications. They are biocompatible and their usefulness as effective Raman/fluorescence probes for labeling as well as for drug delivery has been demonstrated. Related to their biocompatibility, the interaction between NDs and red blood cells (RBCs) is of great interest. In this work, the influence of carboxylated NDs (cNDs) in the re-oxygenation capability of both γ-irradiated and stored RBCs was studied. The standard 25 Gy γ dose recommended to prevent transfusion associated graft-versus-host disease was used. A 5-day maximum storage time was used to evaluate the “storage lesion.” The hemoglobin (Hb) oxygenation state was assessed by Raman microspectroscopy and the morphologic changes on cells were tracked by optical imaging. Our results show that irradiated RBCs have a better re-oxygenation capability and morphological recovery when they are in presence of cNDs.

A study of the thermoluminescent response of commercial synthetic high pressure high temperature (HPHT) type-Ib diamond crystals is reported. In previous works, it was found that the thermoluminescence (TL) glow curves of HPHT diamonds are non-reproducible. In this work, we compare the TL of samples irradiated with β-radiation (5.4 Gy min−1) before and after a stabilization procedure (SP) which includes a high γ-dose irradiation (500 kGy) and a thermal treatment (TT) at 1073 K for 1 h in N2 atmosphere. McKeeveŕs method and Kitis general kinetics order were used, identifying four peaks around 389, 465, 507, and 567 K before the SP which shifted to lower temperatures around 373, 455, 489, 527 K after the SP and the rise of a new TL peak around 620 K. Before the SP both the TL and afterglow (AG) signals presented irregular dosimetric behavior, especially the low temperature TL peaks (373 and 455 K). The uncertainty associated to TL reproducibility was of 12%. After the SP cycle, the TL and AG showed an enhancement in their linear dosimetric response between 0.09 and 1 Gy, reaching saturation around 2 Gy. The TL reproducibility was significantly improved with deviations around 3%, and a better behavior of TL fading was observed.

A method to grow homogeneous micro-sized diamond clusters on silicon by Hot-Filament Chemical Vapor Deposition in a homemade reactor is reported in this work. Thermal decomposition of a CH4:H2 mixture gases was carried out in a horizontal quartz-tube reactor at 2200 °C filament temperature and 1000 °C substrate temperature at relative low pressure around 150 Torr depositing diamonds on silicon wafers. The diamond micro-structures are formed by nano-crystalline diamonds, they have a rounded shape and a narrow particle size distribution around a micrometer. The diamond micro-structures synthesized in this work showed a strong Raman shift signal, a peak at 1330 cm‒1 typical of the diamond and a single optical trap was localized nearby 300 °C by Thermoluminescence analysis indicating that these diamond micro-structures could be a good thermoluminescent dosimeter material. Due to their excellent properties, diamonds obtained by this technique should find application in the biomedical and optoelectronic industry.

HPHT diamonds have been studied for several years for their potential in different applications. In previous studies it has been found that the thermoluminescence (TL) glow curves of “as-grown” HPHT diamonds are non-reproducible. In this work, we study the afterglow (AG), thermoluminescent (TL), and optically stimulated luminescence (OSL) response of commercial samples of synthetic HPHT type-Ib diamond crystals exposed to X-ray irradiation (0.75 mA, 35 kV) at a dose rate of 0.624 Gy/s, after a high gamma (60Co) dose irradiation of 500 kGy followed by a thermal treatment at 1073 K for 1 h in nitrogen atmosphere. Deconvolution of the TL glow curves shows four peaks, located around 379, 509, 561, and 609 K. The crystals exhibit evident AG recorded for 300 s immediately after X-ray irradiation, due to the thermal emptying of the traps responsible for the low-temperature TL peaks (below 400 K). The stimulation of irradiated crystals with 870-nm light, creates pronounced OSL and destroys all TL peaks with the exception of the high-temperature peak at 609 K. The dose responses of the integrated AG, TL, and OSL are linear in the range of 0.6–5 Gy and saturated at higher doses. The reproducibility of AG, TL, and OSL measurements is about 5%. The fading in the first hour of storage in dark conditions at RT of TL signal of HPHT diamond is mainly associated to the emptying of the traps responsible for the 379-K TL peaks.

The persistent luminescence (PLUM), thermoluminescence (TL) and optically stimulated luminescence (OSL) properties of strontium aluminates co-doped with Eu +2 and Dy +3 exposed to beta radiation is reported. The phosphor was synthesized by the combustion synthesis method employing a highly exothermic redox reaction between the metal nitrates [Al(NO 3 ) 3 , Sr(NO 3 ) 2 , Eu(NO 3 ) 3 and Dy(NO 3 ) 3 ] and organic fuel carbohydrazide (CH 6 N 4 O). The long decay PLUM emission, TL and OSL were measured as a function of beta radiation dose. A wide emission band centered at 510 nm (green) related to Eu 2+ ions and lattice defects were observed for the synthesized samples. The presence of a variety of defects and aggregates were responsible for the observed broad 100 °C peaked TL glow curve of the irradiated sample which is composed of several overlapped TL peaks. The existence of multiple trapping levels, with different trapping/detrapping probabilities, is behind the particular features for the PLUM, TL and OSL emissions. We conclude that in the SrAl 2 O 4 :Eu 2+ , Dy 3+ phosphors, the low temperature TL peaked around 30–75 °C is responsible for the PLUM emission and those around 100 °C were related to very stable trapping states which provide suitable radiation storage properties to be used as a PLUM/TL/OSL radiation phosphor.

In this article, we present the effects of Ag doping and after-growth thermal annealing on the photoluminescence (PL) and thermoluminescence (TL) behaviors of SnO2 nanoparticles. SnO2 nanoparticles of 4-7 nm size range containing different Ag contents were synthesized by hydrothermal process. It has been observed that the after-growth thermal annealing process enhances the crystallite size and stabilizes the TL emissions of SnO2 nanostructures. Incorporated Ag probably occupies the interstitial sites of the SnO2 lattice, affecting drastically their emission behaviors on thermal annealing. Both the TL response and dose-linearity of the SnO2 nanoparticles improve on 1.0% Ag doping, and subsequent thermal annealing. However, a higher Ag content causes the formation of Ag clusters, reducing both the TL and PL responses of the nanoparticles.

The behaviour of afterglow (AG) and thermoluminescence (TL) in nine beta-irradiated HPHT Ib type diamond crystals is presented. The transparent yellow synthetic crystals (Sumicrystal, UP-3510) were purchased from ProDiamond, Germany. Immediately after irradiation, the crystals exhibit pronounced AG (phosphorescence) caused by thermal emptying of the traps responsible for the low temperature TL peaks. All AG decay curves are well fitted with the sum of one, two or three exponential decays with the same decay lifetimes of 6.73, 12.8 and 145 s for the fast, medium and slow decay components, respectively. Two different groups of AG decay curves can be distinguished. The first group (three crystals) exhibits intense AG related to fast emptying of some shallow traps. The initial AG intensity of other crystals (second group) is 2–3 order lower than those of the first group crystals. This difference is due to the absence (or very low intensity) of the shallow traps in these crystals. TL glow curves consist of two sets of peaks. The first one with peak maxima at about 50, 70, 180 and 280 °C has high sensitivity but saturates at doses higher 1 Gy. The second set looks like several strongly overlapped TL peaks that exhibit linear–sublinear behaviour. The intensity of the TL peaks of the second set correlates with the intensity of TL below 100 °C. TL glow curves recorded immediately after beta irradiation with indicated doses; the initial part of the curves (below 30 °C) corresponds to AG at room temperature. The inset shows the dose growth of integrated TL between 30 and 330 °C.

There are a number of thermoluminescence (TL) phosphors (and CVD diamond among of them), for which the integrated TL response decreases with the increasing of the heating rate. This effect relates to the thermal quenching (TQ) of luminescence caused by the increasing the non-radiative recombination with the temperature increasing. In this work we present a new fitting method of evaluation the TQ parameters from a series of experimental TL glow curves recorded with variable heating rates. The method is simple, fast and effective. It quite general and can be applied to any series of TL glow curves consisting of several overlapped peaks and does not assume a particular type of TL kinetics. The only limitation of the method is that the end temperature of heating must be enough to ensure full readout of the analyzed TL peaks for all heating rates. The proposed method was applied to a series of TL glow curves measured with the heating rates from 0.1 to 17 K/s for the undoped CVD diamond film. The evaluated TQ parameters were found to be: an activation energy of 0.37 eV and a dimensionless constant of 3.7 × 103.

The persistent luminescence and thermoluminescence properties of SrAl 2 O 4 : Eu 2+ , Dy 3+ phosphors excited with UV–VIS light in the 200–500 nm region were investigated. The thermoluminescence glow curve was found to be composed of peaks around 70, 125 and 245 °C. The persistent luminescence and thermoluminescence excitation spectra exhibited a broad band around 300–500 nm centered at 400 and 420 nm respectively. A linear behavior of the integrated thermoluminescence intensity and persistent luminescence versus irradiation time was found for the first 60 s. The charge detrapping from the 70 °C trapping levels was the major contributor to the observed persistent luminescence at room temperature. The SrAl 2 O 4 : Eu 2+ , Dy 3+ phosphors have suitable properties to be applied as storage and persistent luminescence UV–VIS irradiation dose phosphor.

The thermoluminescence (TL) glow curve of polycrystalline chemically vapor deposited (CVD) diamond is strongly dependent on the heating rate used. In the present work, we report results about the heating rate effects on a 500 μm hot filament (HF) CVD diamond film grown on silicon substrate using a precursor gas mixture composition of CH 4 (5 sccm)― CO( 10 sccm)―H 2 (400 sccm). The irradiations were performed with 60 Co source. The TL measurements were carried out at different heating rates in the 2―30 K/s range. As the heating rate increases, the maximum TL peak intensity decreases and shifts to higher temperature. The shift was from 578 to 669 K for heating rates of 2 and 30 K/s, respectively. The kinetics parameter and its dependence on the heating rate were evaluated using the Chen's peak shape method and a computerized glow curve deconvolution (CGCD) method.

The thermoluminescence (TL), optically stimulated luminescence (OSL) and afterglow (AG) properties of chemical vapour deposition (CVD) diamond film irradiated by beta rays with doses from 0.5 to 1000 Gy have been studied. The film (23 μm) was grown for 47 h on monocrystalline silicon. The TL dose responses are similar for all the peaks and exhibit the typical linear―supralinear―sublinear behaviour. The supralinear growth starts at about 1.0 Gy and goes up to 100 Gy. At higher doses the dose responses go to saturation. The AG and OSL dose responses are similar to the TL one and exhibit the supralinear― sublinear behaviour. The linear part (if it exists) is not observed due to low AG and OSL intensity at doses lower than 2.0 Gy. The diamond film that had been irradiated with high doses, partially preheated and irradiated again with low test dose, exhibits increased TL, OSL and AG sensitivity that can be considered as a mixture of the supralinearity and sensitization. Pure sensitization is observed for the 350 and 400 K TL peaks and AG after preheating the sample to temperatures higher than 500 K. This sensitization gradually decreases from 10 to 1 as the preheating increases from 500 to 770 K.

The thermoluminescence (TL) properties of CVD diamond film irradiated with β rays and illuminated with UV and visible light (200―450 nm) have been studied. The film (23 μm) was grown for 47 h on monocrystalline silicon. The TL glow curves are similar for β irradiation and short wavelength UV light. The β dose response curves and UV light time response curves exhibit linear―supralinear―sublinear behaviour. The structure of the glow curve was determined by a simultaneous deconvolution of a set of curves recorded after preliminary heating to various temperatures. One set of the TL peak parameters was found for all the curves during the deconvolution. The TL glow curves were found to consist of five strongly overlapped peaks. The peaks at about 350 and 400 K obey first-order kinetics. The next three peaks at about 480, 540 and 580 K are described well by general-order kinetics. The TL curves created with light of wavelength between 250 and 450 nm are different from those created by β radiation and short wavelength UV light. The former have low sensitivity and consist of several strongly overlapped peaks, two of them are observed at about 330 and 600 K.

Dose rate effects on the thermoluminescence (TL) properties of undoped and 750ppm nitrogen doped microwave chemical vapor deposition (MWCVD) diamond films were analyzed. The diamond samples were exposed to 2.4-20.67 Gy/min dose rates from a 60 Co source. The TL glow curve of undoped sample showed no apparent dose rate effects. The doped diamond film exhibited dose rate effects consisting in a 10-30% integrated TL increase as the dose rate increased. The TL response as a function of dose rates showed a nonlinear behavior for the doped sample contrary to the undoped diamond film. The dose rate effects were evaluated through the determination of the kinetics parameters by fitting of the TL glow curves. The results indicate that chemical vapor deposition (CVD) diamond may present some dose rate effects on the TL properties in a given dose range, implying that some care should be exercised in order to use CVD diamond films in radiation dose assessments.

The use of nanodiamonds in studies with living systems generally involves the modification of their surfaces with functional groups. Fluorescent molecules can be attached to these groups, so that one can know the exact position of the particles in each moment of the interaction with the cells. Here we modify the surface of detonation nanodiamonds and nitrogen-vacancy center nanodiamonds using carboxylation and hydroxylation procedures. Subsequent reactions with silicates and cysteine, before addition of fluorescein allow to obtain fluorescent nano-conjugates. We used confocal microscopy to observe the position of nanodiamonds interacting with HeLa cells. At 3 h post-incubation the green fluorescence is localized in extracellular rounded like-vesicles assemblies while at 24 h the conjugates can be observed inside the cells. The measurement of the fluorescence emitted by both conjugates allowed to find an enhanced emission of fluorescein isothiocyanate (FITC) when the nitrogen-vacancy center is present. We propose the existence of a fluorescence enhancement by electron transference process. The procedure described in this work allows the functionalization of nanodiamonds with FITC and other molecules using functional surface groups and small size mediators. Also, as was proved in our work, the nanodiamond-fluorescein conjugates can be used to track nanoparticles position within the cell. Localization studies are particularly important for drug delivery applications of nanodiamonds.

The behaviour of afterglow (AG), thermoluminescence (TL) and infrared-stimulated luminescence (IRSL) in beta-irradiated chemical vapour deposition diamond is presented. The TL glow curve consists of four peaks with maxima at about 380, 430, 530 and 610 K. The AG decay is fitted by Becquerel's law with exponent close to 1, and correlates well with the thermal emptying of the traps responsible for the 380 K peak. Stimulation with IR light (830 nm) creates intense IRSL and destroys the 380, 430 and 530 K peaks. Illumination with shorter wavelength light also destroys the 610 K peak. The thermal cleaning procedure removes subsequently TL peaks, AG and IRSL. The AG signal decays together with the disappearance of the 380 K peak. The IRSL signal decays continuously with the removal of the 380, 430 and 530 K peaks. Traps responsible for the 610 K peak do not participate in the IRSL process.

Chemical vapor deposition (CVD) diamond has not found extensive application as a thermoluminescence (TL) dosimeter, mainly because its TL glow curve shape is not reproducible. A slight variation in the growing conditions may result in strong changes in the morphology, microstructure, and surface-impurity-related defects, considerably affecting the TL glow curve features. In order to study the main TL characteristics under controlled growing conditions, we present results on three 0.5, 1.0, and 4.0 μm thick hot filament CVD (HFCVD) diamond films grown on Si (100) substrates. The recorded TL glow curves were resolved into individual peaks by a home-made deconvolution program and the kinetic parameters of the peaks were extracted. The best fits of the TL glow curves were obtained using four peaks, except for the 4.0 μm thick sample that required five TL components. All samples showed three high intensity TL peaks between 180-400°C and a less intense one or two peaks in the 100-180°C low-temperature region. The low-temperature components all obey second-order kinetics while the high-temperature ones obey first and 1.6 order kinetics. The samples showed similar TL peaks with comparable kinetics parameters. It is concluded that the manufacturing of high quality HFCVD diamond may require a further improvement in the growing process in order to exploit its excellent tissue-equivalence properties in clinical and medical applications.

SrAl2O4:Eu2+, Dy3+ is a phosphor characterized by a long persistent luminescence (PLUM) when excited with UV–vis light and ionizing radiation exhibiting intensity variation in the 10–320 K temperature range and maximum intensity around 320 K. In this work, we study the PLUM behavior of SrAl2O4:Eu2+, Dy3+ as a function of temperature from room temperature to 670 K in samples exposed to β irradiation. The room-temperature irradiation followed by PLUM readout revealed an integrated PLUM maximum at 323 K decreasing later. In contrast, irradiation and PLUM readout at temperatures above room temperatures produced integrated PLUM intensities maxima around 425 and 625 K. Successive cycles of preheating followed by irradiation and PLUM readout produced an increasing of the PLUM intensity as a function of cycle number. The observed phenomenon was ascribed to trapped electrons at the multiple trapping states related to the 425 and 625 K defects levels and electron transfer from one trap to another (electron hopping). Eventually, there is a return to the 5d level of Eu3+ cations with the characteristic PLUM emission by thermal energy supplied at room temperature (lattice vibrations) or by a preheating–irradiation-readout cycle. This property may allow keeping up the PLUM properties of SrAl2O4:Eu2+, Dy3+ phosphors through background radiation self exposure and adequate heating processes.

The γ-radiation effects on copper-doped NaCl:Cu crystals were investigated. Single crystals exposed to gamma radiation from 0.001 kGy to 30 kGy at room temperature exhibited optical absorption bands attributed to Cu– (236 nm), Cu+ (255 nm) and F (463 nm) centers. The F and Cu absorption annealing bands were correlated to the thermoluminescence (TL) glow-curve peak structure around 30–165 °C and 215–350 °C, respectively. The TL glow curves of samples doped with 0.04 mol% and 0.08 mol% of Cu+ ions showed a strong quenching effect for higher doping concentration. In addition, thermal bleaching of γ-irradiated specimens confirmed the color centers and Cu-doping participation on the TL process. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Microwave chemically vapour-deposited (MWCVD) diamond films have been successfully used in dosimetric applications including radiotherapy and industrial dose assessments. The thermoluminescence (TL) properties and dose response, in a suitable MWCVD diamond film thermoluminescent dosimeter, should be independent of the irradiation dose rate used. Dose rate effects have been reported to exist, affecting the TL performance of polycrystalline CVD diamond. In the present work, dose rate effects on the TL kinetic parameters of two MWCVD diamond films of 6 and 12 μm thickness, exposed to 60Co gamma dose rates of 2.4, 5.94 and 13.1 Gy/min, were investigated using a computerised glow curve deconvolution method. The TL glow curves featured a single TL peak at different dose rates, which were best fitted with a first-order kinetic curve having 2–3% figure of merit. No significant dose rate effects on the TL kinetic properties of the studied samples were observed. †Paper presented as a contribution to the 10th Intern...

The thermoluminescence (TL) and optically stimulated luminescenece (OSL) response of TiO2:Yb nanoparticles are studied. After beta irradiation, the materials developed a significant TL/OSL signal associated to several localized trapping states around 360-620 K. The OSL signal is mainly due to the releasing of trapped charges in the low temperature (360 and 460 K) trapping states. A computer glow curve deconvolution procedure was used to determine the activation energies and kinetic order of the TL processes.

ZnO nanophosphors prepared by a glycol mediated chemical synthesis exhibit afterglow (AG) and thermoluminescence (TL) after excitation with beta rays. These properties, which are of great interest in dose assessment of ionizing radiation fields, could be appreciably modified by Yb doping. Concentration of 1, 2 and 5% diminished the AG and TL efficiency and modified the TL glow curve shape significantly. However, the 5% Yb doping concentration reduced the AG and TL fading behavior, improving the use of ZnO:Yb (5%) as potential TL ionizing radiation dosimeter.

The thermoluminescence (TL) of undoped and Dy3+ doped ZrO2 nanocrystals under β-ray irradiation is reported. The TL glow curves are the result of the overlapping of four TL peaks produced partly by the intrinsic defect of highly asymmetrical monoclinic structure and partly due to defects produced during the synthesis process. The introduction of dopant ions induces changes in the glow curve due to the enhancement of high temperature peaks intensity. The results show that both undoped and doped ZrO2 nanocrystalline phosphor present good TL efficiency as well as good dose response which qualify them as a potential β-ray dosimeter.

The ionoluminescence (IL) spectrum resulting through the interaction of proton beams with bulk samples has become an adequate technique for material characterization. In the present work, we have investigated the IL response of microwave (MW) and hot-filament (HF) CVD diamonds, by examining the radiative recombination induced by a 1.9 MeV proton beam (0.25-3.0 μA) on the diamond films. The IL spectral characteristics were different for dissimilar diamond films. The HFCVD diamond showed two broad IL bands around 300-450 nm and/or 500-750 nm. The bands may be associated to intrinsic defects and to [N-V] and [N-V-N] centers. In some cases the H3-center band around 503 nm (2.46 eV) was also clearly depicted. The HFCVD diamond displayed mainly a well-defined dislocation-related A band centered at 440 nm (2.82 eV). The results indicated that the IL technique is a practical tool to obtain spectral information about defects and centers in CVD diamonds.

The effects of gamma radiation dose rates on the thermoluminescence (TL) properties of hot filament CVD diamonds films, in the 2.4–81.11 Gy/min dose rate range was investigated. The integrated TL increased at the dose rate increased reaching a maximum value at 43.4 Gy min − 1 . Dose rate effects were not observed in the TL glow curve shape and kinetics parameters as demonstrated by using a computerized glow curve deconvolution procedure. The diamond films exhibited 3–5% TL reproducibility irrespective of the radiation dose rate used, which is comparable to commercial dosimeter materials. The results indicate that dose rate effects should be taken into consideration when performing dose assessment with HFCVD diamonds, since a given irradiation dose at different dose rates may result in different TL read outs.

It is known that the thermoluminescence (TL) performance of CVD diamond depends on the impurity concentration and doping materials introduced during growing. We report on the TL properties of undoped and 750 ppm nitrogen-doped CVD diamond grown on (0 0 1) silicon substrate. The samples were exposed to gamma radiation from a Gammacell 200 Nordion irradiator in the 10–500 Gy dose range at 627 mGy/min dose rate. The nitrogen-doped CVD diamond sample exhibited a TL glow curve peaked around 537 K and a small shoulder about 411 K and a linear dose behavior in the 10–60 Gy dose range. In contrast, the undoped specimen showed a 591 K peaked TL glow curve and linear dose response for 10–100 Gy doses. However, both samples displayed a non-linear dose response for doses higher than 100 Gy. The doping effects seem to cause a higher TL efficiency, which may be attributed to the differences in the diamond bonding and amorphous carbon on the CVD samples as well as to the presence of nitrogen. In addition, the nitrogen content may produce some structural and morphological surface effects, which may account for the distinctive TL features and dose response of the diamond samples.

Current radiation dosimetry methods involve the release of trapped charge carriers in the form of electrons–holes pairs generated by irradiation exposure of the dosimetric materials. Thermal and optical stimulations of the irradiated material freed the trapped charges that eventually recombine with interband centers producing the emission of light. The integrated intensity of the emitted light is proportional to the radiation dose exposure. In this work, we present an UV radiation dosimetry technique based on the characteristic persistence luminescence (PLUM) 4f65d1→4f7 electronic transition of Eu2+ ions in SrAl2O4:Eu2+, Dy3+. The dose assessment is carried out by measuring the PLUM signal integrated during a certain time. The PLUM performance of SrAl2O4:Eu2+, Dy3+ phosphor exhibited a linear behavior for the first 50 s of UV irradiation. For higher UV time exposure the behavior is sublinear with no apparent saturation during a 10 min period. The PLUM dosimetry response was performed at 400 nm that corresponds to the main band component of the PLUM excitation spectrum in the 250–500 nm range. The main advantage of a dosimeter device based on the PLUM of SrAl2O4:Eu2+, Dy3+ is that neither thermal nor optical stimulation is required, avoiding the need of cumbersome electronic photo/thermal stimulation equipment. Due to the highly efficient 250–500 nm PLUM response of SrAl2O4:Eu2+, Dy3+, it could have potential application as UV radiation dosimeter in the UV range of grate human health concerns caused by UV solar radiation.

It is known that room temperature beta-irradiated Ib type diamond generates a non-reproducible TL glow curve shape, due to mobility of the impurity-vacancy (I-V) and interstitials (I) defects in the 30-800 °C temperature range. This situation may hinder the use of this type of diamond material in dose assessment applications. The recurring heating of the Ib type diamond sample changes the defects concentration and consequently the intensity of the TL glow peaks associated to the characteristic temperature annealing stages. In the present work we have performed thermal annealing (TA) treatment on an Ib type diamond in the 100-800 °C range previous to beta irradiation. It was observed that after the 800 °C annealing treatment the TL glow curve showed 3-5% reproducibility, in contrast to the non-reproducible TL observed in non-annealed diamond, and remained the same after two months of successive TL read outs. Moreover, the 800 °C annealing treatment assured a linear integrated TL dose behavior, a significant improvement over non-annealed samples that could facilitate the employment of Ib type synthetic diamond in dosimetric applications.

Dose rate effects are important in thermoluminescent (TL) dosimeter applications because a certain absorbed dose given at different dose rates may result in a different TL yield. The present work reports about the dose rate effects on TL glow curves and kinetics properties of microwave plasma assisted chemical vapor deposition (MWCVD) diamond films grown on (100) silicon. The diamond films were exposed to γ radiation at 20.67, 43.4 and 81.11 Gy min -1 dose rates in the range of 0.05-10 kGy. The films showed a linear dose behavior up to 2 kGy and reached saturation for higher doses. The TL intensity varied as a function of dose rate and the samples had a maximum TL response for relatively lower dose rates. A single first order kinetics TL peak was typical for low doses while at higher doses two first order kinetics peaks were necessary to fit the glow curves. The results indicate that dose rate effects may be significant in dosimetric applications of MWCVD diamond.

Afterglow (AG) and thermoluminescence (TL) of CVD diamond UV-irradiated with wavelength of 200-260 nm at room temperature are reported. The AG curves monotonously decrease with time and are fitted well by the hyperbolic law. The decay times depends on UV wavelength and decreases with the AG intensity increasing. The TL glow curves exhibit two pronounced TL peaks with maxima at about 350 K and 513 K with unstructured signal between them and are fitted well by four TL peaks. The first, 350 K peak with the activation energy of 0.59 eV was supposed to be second kinetics order. The higher temperature peaks at 402 K, 445 K and 513 K with the activation energies of 0.46 eV, 0.49 eV and 0.68 eV, respectively were assumed to be first kinetics order. The comparison of the AG decay times with the kinetics parameters of the 350 K TL peak proved that AG is caused by thermal emptying of the traps responsible for the 350 K peak. The behaviour of AG and 350 K TL peak was described by the model, in which shallow traps, recombination centers and deep thermally disconnected traps are taken into account. The AG and TL creation spectra are practically the same and consists of a broad band, which exponentially increases from 260 nm, reaches a maximum at 240 nm and then begins decreasing. The creation spectra of the AG and TL peaks are the same and closely related with the fundamental absorption of UV light near indirect band gap of diamond.

Synthetic CVD diamond, being non-toxic and tissue equivalent, has been proposed as a ionizing radiation passive dosimeter with relevant applications in radiotherapy and clinical dosimetry. In the present work, the thermoluminescence (TL) properties of microwave-assisted chemical vapor deposition (MWCVD) diamond, 6 μm thick film grown on (100) silicon substrates, were studied after room temperature γ-irradiation for 2.4, 3.1, 5.94, 13.1, 20.67, 43.4 and 81.11 Gy min−1 dose rates in the range of 0.05–10 kGy. At fixed irradiation dose the TL efficiency increases as the dose rate increases. As the dose increases the peak temperature at the maximum intensity of the TL glow curve is shifted about 10 K degrees toward the lower temperature side. The TL glow curve shape resembles first-order kinetics for low-radiation doses and second-order kinetics for higher doses. Linear dose behavior was found for doses below 200 Gy and supralinear for higher doses; respectively, with a significant dependence on the dose rate,...

The thermoluminescence (TL) characterization of microwave plasma assisted chemical vapor deposition diamond (MWCVD) films of 6 and 12 μm thickness grown on (1 0 0) silicon substrates was performed. The films exhibited a single well-resolved TL peak around 580 K at doses lower than 40 Gy. As the irradiation dose increased the TL peak broaden and shifted towards the low temperature side of the glow curve. The diamond samples exposed to 0.67 Gy/min 60 Co gamma radiation displayed a linear dose behavior up to 100 Gy being non-linear for higher doses. The 12 μm film showed lower TL efficiency as compared to the 6 μm specimen. The discrepancy was attributed to the non-uniform distribution of nucleated sp 3 diamond and sp 2 bonded carbon on the substrate as revealed by SEM micrograph and Raman spectroscopy of the samples. The integrated TL glow curve of the samples exhibited low room temperature thermal fading and 3% reproducibility. The results show that MWCVD diamond films possess promising properties for radiation dosimetry applications.

The luminescence in SrAl 2 O 4 : Eu 2 + , Dy 3 + under continuous excitation is quite different from the “standard” intra-ion photoluminescence (PL) and gradually grows during hundreds of seconds before reaching the saturation (photo-charging effect). In this work, we report the behavior of photo-charging effect under the blue and UV light irradiation at temperatures between 20 and 370 K, as well as afterglow (AG) and thermoluminescence (TL) observed after the irradiation termination. At 20 K the photo-charging effect is absent. With increasing temperature the photo-charging effect appears as a result of PL decreasing due to competitive trapping process with activation energy of 0.17 eV. The AG decay curves are described well by the Becquerel's law with the exponent close to 1. The AG decay time is about 10–50 s and practically does not depend on temperature. The TL glow curve exhibits at least seven partially overlapped peaks with maxima at 50, 65, 80, 155, 200, 250 and 290 K. The emission spectra of Eu 2 + consist of two bands at 450 and 520 nm. Both the bands are the same for the PL, AG and TL spectra, but their ratio depends on temperature and the luminescence type.

The thermoluminescence (TL) properties of undoped, Ce 3+ and Tb 3+ doped Y 3 Al 5 O 12 (YAG) nanocrystals under UV-, X- and β-rays irradiation is reported. The TL signal of undoped and doped samples indicates a high sensitivity to UV-, X- and β-ray irradiation. The introduction of the doping ions induces changes in the trapping processes and the TL efficiency. The results show that both undoped and doped YAG nanocrystalline phosphor present good TL efficiency as well as good dose response which qualify them as a potential UV-, X- and β-ray dosimeter. A linear response under X-ray irradiation is observed for low doses level in the 0.02–1.02 μGy range and for relatively high doses level of β-ray irradiation in the range from 10 to 600 Gy.

The presence of nitrogen or other impurities in HPHT type Ib synthetic diamond may produce shallow or deep localized trapping states for electrons (holes) with activation energies below the conduction (above the valence) band. The present work deals with room temperature afterglow (AG), thermoluminescence (TL) and infrared-stimulated luminescence (IRSL) in HPHT type Ib diamond. The existence of vacancy impurity-related defects gives rise to a characteristic AG, TL and IRSL in beta-irradiated samples. The AG luminescence decays fast, decreasing to about 103 of its initial intensity value in 100 s. The deconvoluted TL glow curve is composed of a 1.4-order peak at 375 K and three first-order kinetics peaks at 442, 475 and 514 K. The IRSL was excited with 830 nm light releasing electrons from the trapping states with different efficiencies. The TL glow curve was found to be non-reproducible because the multiple impurity-related defects induced by irradiation are unstable at temperatures around 800 K. The peculiar AG and TL behavior observed in the investigated HPHT type Ib synthetic diamond may hinder its application in TL dosimetry.

Pure ZrO2 powders were prepared by the sol–gel method from zirconium oxychloride. For hydrolysis and peptization aqua ammonia and nitric acid were used. The obtained hydrogel was converted to xerogel by aging in air at room temperature and subsequent drying at 373 K for 30 min. This initial xerogel was calcinated in air at different temperatures in the range from 873 to 1273 K for 30 min. Beta irradiated powder exhibit four thermoluminescence peaks with maxima at 340, 415, 470 and 540 K. To clarify the structure of the glow curves a thermal cleaning procedure was used. The initial rise method and deconvolution of the glow curves recorded after preheats were applied to determine the peaks kinetic parameters. All the peaks are well described by one set of the kinetic parameters. The kinetics orders are equal to 2.0, 1.4, 1.7, 1.3 and the activation energies are equal to 0.65, 0.78, 1.1, 1.2 for the increasing peak temperatures, respectively. The calcination temperature strongly influences the sensitivity of ZrO2. The dependences of the peak areas on the calcination temperature are fitted well with straight lines in the Arrhenius coordinates with the activation energy of 1.7 eV that can be related with migration of oxygen vacancies.

Polycrystalline chemically vapor deposited (CVD) diamond films have been proposed as detectors and dosimeters of ionizing radiation with prospective applications in high-energy photon dosimetry applications. We present a comparison study on the thermoluminescence (TL) properties of two diamond film samples grown by the hot filament CVD method having thickness of 180 and 500 μm and exposed to γ radiation in the 1–300 Gy dose range. The 180 μm thick sample deposited on silicon substrate displayed a TL glow curve peaked at 145 °C. The 500 μm, which was a free standing sample, exhibited higher intensity and a well defined first order kinetics TL glow peak around 289 °C. Both diamond samples showed a linear dose behavior in the 1–50 Gy range and sublinear behavior for higher doses. The 180 and 500 μm samples presented about 80% and 30% TL losses in a 24 h period, respectively, with both samples showing excellent TL reproducibility. The results indicate that the 500 μm CVD diamond film exhibited a good TL behavior adequate for γ radiation dosimetry.

Diamond is a material with extreme physical properties. Its radiation hardness, chemical inertness and tissue equivalence qualify it as an ideal material for radiation dosimetry. In the present work, the optically stimulated luminescence (OSL) and thermoluminescence (TL) characteristics of a 10 microm thick CVD diamond (polycrystalline diamond films prepared by chemical vapor deposition) film were studied in order to test its performance as a beta radiation dosemeter. The TL response is composed of four main TL glow peaks; two of these are in the range of 150-200 degrees C and two additional peaks in the 250-400 degrees C temperature range. The integrated TL as a function of radiation dose is linear up to 100 Gy and increases with increasing dose exposure. The dose dependence of the integrated OSL exhibits a similar behavior. The observed OSL/TL behavior for the CVD diamond film clearly demonstrate its capability for applications in radiation dosimetry with special relevance in medical dosimetry owing to the diamond's intrinsic material properties.