High-dose Electron Beam Research Articles

Effect of high-dose electron beam irradiation on thermal decomposition behavior of polytetrafluoroethylene (PTFE)

In this study, we investigated the effect of high-dose (>10.0 MGy) irradiation on polytetrafluoroethylene (PTFE) decomposition in the presence of oxygen. To this end, we analyzed the chemical structures of PTFE residues after irradiation and thermal treatment as well as the outgas components during thermal treatment at 50 °C intervals. Thermogravimetric analyses indicated that the residual PTFE powder exhibited an initial decomposition (5% weight loss) at 159 °C, which is 365 °C lower than that of the original unirradiated sample. The initial decomposition temperature decreased at up to 5 MGy and gradually leveled off at above 140 °C. Fourier transform infrared (FT-IR) spectroscopy analysis of the residual PTFE powders indicated that the contents of thermal decomposition at lower temperature ranges were qualitatively related to the extent of the formation of oxidizable PTFE components, such as carbonyl groups. The formation of these components increased as the absorbed doses increased. The oxidized components gradually decreased with increasing thermal treatment temperature and tended to disappear at 470 °C. This demonstrated the effect of the oxidized compounds in the irradiated PTFE on lower temperature decomposition. The analysis of the gas components resulting from the thermal decomposition of the PTFE residuals revealed more detailed chemical information concerning the oxidative components of the irradiated PTFE. At temperatures below 420 °C, approximately 30% of the PTFE residue underwent pyrolysis to yield oxidized fluorocarbon products (CxFyOz) and further decomposed products (CO2). The remaining 70% of the residue thermally decomposed at temperatures above 420 °C, yielding monomer-related products such as C2F4, C3F6, and C4F8. These were identical to the gas products resulting from the thermal degradation of the original PTFE in the same temperature range. These results are indicative of the possibility of recycling and reusing fluorocarbons during irradiation.

The effect of annealing temperature on the change in the structure, luminescent and dosimetric properties of ultrafine α-Al2O3 ceramics

The influence of high-temperature annealing (900-1700 оС) on the morphological features, luminescent and dosimetric properties of ultrafine α-Al2O3 ceramics obtained from nanopowder by its compaction has been studied. In contrast to previously published papers, for more reliable and unambiguous determining of the relationship between the nanocrystallite size and luminescent properties, the samples were annealed in air without a reducing agent. It has been established that at Т>1500 оС there is a significant increase in the intensity of thermoluminescence (TL) of the peak at 170 оС, which coincides with the temperature range of the most significant increase in the size of nanocrystallite. Another reason for the increase in the TL response may be the formation of luminescence centers during annealing, which is proved by the appearance of a new cathodoluminescence band at 2.2–3.4 eV of unknown nature. The analysis of the dose dependences of TL of nanostructured ceramics irradiated with a high-dose pulsed electron beam (130 keV, 1.5 kGy per pulse) reveals their sublinear nature. Moreover, anomalous TL fading has been found, the magnitude of which increases with a crystallite size.

Effects of the electron-beam-induced modification of g-C3N4 on its performance in photocatalytic organic dye decomposition

Graphitic carbon nitride (g-C3N4) was irradiated with an electron beam (EB) to improve the photocatalytic efficiency of Rhodamine B (RhB) decomposition. EB irradiation up to 200 kGy improved the efficiency of RhB decomposition, whereas further EB irradiation lowered the reaction efficiency. The chemical structure and textural properties of g-C3N4 were altered via EB irradiation. Low-dose EB irradiation introduced structural defects in g-C3N4 and increased its surface hollow depth, resulting in improved photocatalytic efficiency. In contrast, high-dose EB irradiation decreased the surface hollow depth, probably owing to intense structural destruction following recomposition.

Study on antibacterial mechanism of electron beam radiation on Aspergillus flavus

Contamination with Aspergillus flavus, which produces carcinogenic metabolites, during the post-harvest storage of agricultural products seriously endangers human health and safety. In this study, the efficacy of short-term electron beam irradiation processing with high sterilization efficiency, no contamination and no additives was evaluated for the prevention and control of A. flavus. The effects of irradiation on Aspergillus growth were determined based on analyses of physical and chemical indexes, morphology, mycelial growth, spore germination rates, mycelial dry weights, and toxin-producing ability. The effects of irradiation on the cell membrane and cell wall of A. flavus were investigated based on assays of the chitin content, chitinase activity, protein concentration, and malondialdehyde content. Damage to the antioxidant system was determined by the hydrogen peroxide content, catalase activity, superoxide dismutase activity, superoxide anion radical scavenging activity and rates of 1,1-diphenyl-2-trinitrophenylhydrazine inhibition. The inhibitory effect of irradiation on peanut invasion by A. flavus was verified. After irradiation, the thallus morphology was destroyed, mycelial growth was inhibited, and the spore germination rate, mycelial dry weight, and toxin-producing ability of A. flavus were reduced. Chitinase activity and the malondialdehyde content increased, while the chitin and total protein contents decreased. Catalase activity, superoxide dismutase activity, superoxide anion radical scavenging activity, and the rate of 1,1-diphenyl-2-trinitrophenylhydrazine inhibition decreased, while the hydrogen peroxide content increased after irradiation. These findings suggested that electron beam irradiation can effectively inhibit the normal growth and toxin production of A. flavus. Irradiation increased cell membrane permeability and decreased the integrity of the cell wall. The antioxidant system was damaged to some extent. Compared with that in unirradiated A. flavus, high-dose electron beam irradiation effectively inhibited growth. As a means of postharvest control, electron beam irradiation may have wide applications in the agricultural industry.

Characterization of a Radiofluorogenic Polymer for Low-Energy Electron Beam Penetration Depth Visualization.

Low-energy (80–300 keV) electron beam accelerators are gaining in importance in the radiation processing industry due to their ease of use and wide range of applications (e.g. product surface sterilizations or polymer curing and cross-linking). Due to their very low penetration depth (tens to hundreds of microns), currently used film dosimeters exhibit dose gradients over their thickness and do not resolve the dose response in the first microns of the irradiated material. Hence, the surface dose, defined as the dose in the first micron Dµ, cannot be measured directly. This study presents a polymer material as a dosimeter candidate for high-dose low-energy electron beam irradiations. The readout of the dose-dependent fluorescence intensity, originating from a pararosaniline dye reaction when irradiated, is measured using fluorescence microscopy. So far, no in-depth characterization of the material has been performed, leaving the stability and fluorescence properties of the material not fully optimized. We describe the improvements in polymer composition and the fabrication method, and characterize the material properties in terms of the thermal stability, glass transition temperature, refractive index, hardness, rheological behavior, and water affinity. All of these create a complex set of requirements a polymer needs to fulfill to become an effective dosimeter when measuring using confocal microscopy. The fluorescence readout procedure will be addressed in further studies.

Glass transition temperature of Risø B3 radiochromic film dosimeter and its importance on the post-irradiation heating procedure

Full-color development and stability of measured absorbance of the commercially used Risø B3 radiochromic film dosimeter can be achieved by applying a post-irradiation heat treatment procedure, typically at 60 °C for 10 min. However, the choice of post-irradiation heating duration and temperature has only been based on a trial and error method, and thus, the thermal stability of the material has not been fully studied before. We show that B3 film undergoes a rapid thermal decomposition of the PVB polymer base at 400 °C, with an initiation of the process at 70 °C. It means that higher irradiation temperatures, which can occur e.g. at high-dose electron beam irradiation, may cause polymer degradation. We also show that the post-irradiation heating temperature agrees with the polymer material's glass transition temperature as measured by differential scanning calorimetry (DSC). The post-irradiation heating procedure successfully removes the film's thermal history. This can be seen as an endothermic peak in the first heating cycle, which becomes smaller for higher irradiation doses. Glass transition temperatures of irradiated and post-irradiation heated B3 film are lower than those of the non-irradiated film, and decrease with increasing the dose. That implies a probable chain scission or degradation of the base polymer upon irradiation using high dose rates with no irradiation temperature control.

NF-E2-Related Factor 2 (Nrf2) Ameliorates Radiation-Induced Skin Injury.

Radiation-induced skin injury (RISI) commonly occur in cancer patients who received radiotherapy and is one of the first clinical symptoms after suffering from nuclear exposure. Oxidative damage is the major causes of RISI. Nuclear factor erythroid 2-related factor 2 (Nrf2) is considered as a key mediator of the cellular antioxidant response. However, whether Nrf2 can alleviate RISI after high-dose irradiation remains unknown. In this study, we demonstrated that Nrf2-deficient (Nrf2 -/-) mice were susceptible to high-dose irradiation and adenovirus-mediated overexpression of Nrf2 (ad-Nrf2) protected against radiation in skin cells. Overexpression of Nrf2 attenuated the severity of skin injury after high-dose electron beam irradiation. To uncover the mechanisms of Nrf2 involved in RISI, mRNA sequencing technology was performed to analyze the mRNA expression profiles of Ad-Nrf2 skin cells following radiation. The results revealed that a total of 127 genes were significantly changed, 55 genes were upregulated, and 72 genes were downregulated after Nrf2 overexpression. GSEA showed that Nrf2 was associated with positive regulation of genes involved in the reactive oxygen species pathway after radiation. Taken together, this study illustrated the role of Nrf2 in RISI and provided potentially strategies for ameliorating RISI.

Degradation of PFOS and PFOA in soil and groundwater samples by high dose Electron Beam Technology

Remediation technologies are urgently needed to degrade poly – and per fluoroalkyl substances (PFAS) in groundwater and soils. Since high energy electron beam (eBeam) technology involves rapid oxidation and reduction reactions it has the potential to breakdown PFAS. In this study, the technology was applied to PFAS-contaminated groundwater and soil samples to degrade PFOS and PFOA and other PFAS. An eBeam dose of 2000 kGy (kGy) reduced PFOS and PFOA concentrations in groundwater by 87.9% and 53.7% respectively. In soils with 10% moisture content, PFOS and PFOA concentrations were reduced by 99.9% and 86.5%, respectively. Out of 17 different PFAS that were detected in the soil sample, the 2000 kGy dose was able to degrade 10 PFAS to below detectable levels: PFNA (initially 19.4 ng/g), PFDA (3.9 ng/g), PFPeS (12.1 ng/g), PFHxS (365 ng/g), PFHpS (18.0 ng/g), PFNS (4.3 ng/g), 4:2 FTS (16.6 ng/g), 6:2 FTS (146.1 ng/g), 8:2 FTS (165.6 ng/g) and PFOSA (171.8 ng/g). Of the remaining 7 PFAS, the removal efficiency ranged between 49% and 99.9%. It appears that eBeam degradation of PFAS in soil is more effective at reduced soil moisture content.

Fading and residual responses for thermoluminescent dosimetry of silica beads irradiated using a high-dose electron-beam

Thermoluminescent (TL) glow-curves of 10 different coloured Toho Japan bead types have been obtained using a Risø TL/OSL reader studied for a fading period of 6 months as well as for residual dosimetry for fading up to 16 months after irradiation. For the entirety of the delay period studied the Frosted beads showed the largest TL response followed by Pink and Rose beads. Pink beads showed the best fit to the second order polynomial fit applied to the observed fading. In a more detailed dose curve fitted for a 6 month delay between irradiation and readout in order to determine the nature of the TL response as a function of increasing dose, it was found to follow the same trend for all bead colours. The residual TL response was also studied for beads that showed a large TL response. In these studies all colours showed similar dose response curves to those for the 1st readout, with Pink beads showing the best agreement to the fit applied to model fading.

Observation of anomalous emissions of nonpolar a-plane MgZnO and ZnO epi-films based on XEOL and time-resolved XEOL in hybrid bunch mode

X-ray excited optical luminescence (XEOL) using an x-ray nanobeam operating in the hybrid bunch mode provides not only a sufficiently high peak power density but also high-quality temporal domain measurements for studying the luminescence dynamics of photonic materials and devices. We used these features to investigate the peculiar emission behavior of the as-grown and rapid thermal annealing (RTA)-treated a-plane MgZnO epi-films, from which an anomalous emission was observed at ∼325 nm, along with a rapid increase in near-band edge (NBE) emission with increasing x-ray irradiation time. This peculiar emission behavior was also observed in the cathodoluminescence spectra obtained under electron beam excitation. Increases in the NBE emission intensity of the RTA-treated a-plane MgZnO epi-film were observed in terms of both photoluminescence and small anomalous emissions of XEOL. This can be explained by the effective transfer of Mg atoms from interstitial sites to suitable sites as a result of RTA treatment. Based on comparison with an a-plane ZnO epi-film without Mg, we conclude that the anomalous emission peak is caused by Mg-related energy states created by the high-dose x-ray or electron beam irradiation. Furthermore, the rapid increase in NBE emission and the reduction in the long decay lifetime can be attributed to charge transfer from the Mg clusters, which are thus responsible for the anomalous emissions.

Optically Induced Effects in Irradiated Ultrafine Al2O3–BeO Ceramics

We studied optically induced effects in ultrafine Al2O3–BeO ceramics irradiated with a high-dose pulsed electron beam (130 keV). Upon optical excitation of ceramics at 470 nm, optically stimulated luminescence is observed due to the depletion of traps associated with thermoluminescence peaks at 380 and 530 K. These traps are characterized by a complex energy spectrum with a nonuniformly distributed photoionization cross section. The prospects of using optically stimulated luminescence of Al2O3–BeO ceramics in high-dose dosimetry (3–30 kGy) have been proved.

CO2 conversion by high-dose rate electron beam irradiation: one-step, metal-free and simultaneous production of H2, CO, CH4, C2H6 and organic acids from an acid-decomposed CaCO3/additive EtOH mixture

The reduction in CO2 emissions is an important issue across many industries.

Phototransferred Thermoluminescence of Dosimetric α-Al2O3 Crystals Irradiated by a Pulsed Electron Beam

The thermoluminescence (TL) of deep traps of anion-defective alumina monocrystals irradiated by a high-dose (more than 1 kGy) pulsed electron beam (130 keV) is studied. The deep traps in the studied material are classified according to the TL temperature range. It is demonstrated that the phototransferred thermoluminescence (PTTL) in the temperature range of the main TL peak is induced by optical charge migration from deep traps that are emptied at 400–470 and 470–600°C. An anomalous PTTL enhancement in crystals subjected to stepped annealing in the 350–400°C interval is observed. It is demonstrated that this effect may be caused by competing processes of charge transfer that involve deep traps corresponding to the TL peak at 390°C. The applicability of PTTL in the dosimetry of high-dose (1–50 kGy) pulsed electron beams is established.

Isothermal build-up of deep trap thermoluminescence of anion-defective alumina crystals

TL of a deep trap was studied during isothermal heating in dosimetric Al2O3:C crystals irradiated by a high-dose pulsed electron beam. The TL build-up of a deep trap associated with the peak at 440 °C was found. This effect was absent for TL peaks at 305 and 565 °C. The observed TL build-up can be interpreted in terms of the kinetic model taking into account the process of thermal ionization of excited states of F-centers. The dependences of TL build-up intensity and time on the temperature, heating rate and occupancy of deep hole traps were established experimentally and confirmed by calculations.

Does sterilization with fractionated electron beam irradiation prevent ACL tendon allograft from tissue damage?

Allografts are frequently used for anterior cruciate ligament (ACL) reconstruction. However, due to the inherent risk of infection, a method that achieves complete sterilization of grafts is warranted without impairing their biomechanical properties. Fractionation of electron beam (FEbeam) irradiation has been shown to maintain similar biomechanical properties compared to fresh-frozen allografts (FFA) in vitro. Therefore, aim of this study was to evaluate the biomechanical properties and early remodelling of grafts that were sterilized with fractionated high-dose electron beam irradiation in an in vivo sheep model. ACL reconstruction was performed in 18 mature merino mix sheep. Sixteen were reconstructed with allografts sterilized with FEbeam irradiation (8×3.4kGy) and two with FFA. Eight FFA from prior studies with identical surgical reconstruction and biomechanical and histological analyzes served as controls. Half of the animals were sacrificed at 6 and 12weeks, and biomechanical testing was performed. Anterior-posterior laxity (APL) was assessed with an AP drawer test at 60° flexion, and load to failure testing was carried out. Histological evaluation of mid-substance samples was performed for descriptive analysis, cell count, crimp and vessel density. For statistical analysis a Kruskal-Wallis test was used for overall group comparison followed by a Mann-Whitney U test for pairwise comparison of the histological and biomechanical parameters. Biomechanical testing showed significantly decreased stiffness in FEbeam compared to FFA at both time points (p≤0.004). APL was increased in FEbeam compared to FFA, which was significant at 6weeks (p=0.004). Median of failure loads was decreased in FEbeam grafts, with 12 reconstructions already failing during cyclic loading. Vessel density was decreased in FEbeam compared to FFA at both time points, with significant differences at 12weeks (p=0.015). Crimp length was significantly shorter in FEbeam compared to FFA at both time points (p≤0.004) and decreased significantly in both groups from 6 to 12weeks (p≤0.025). ACL reconstruction with fractionated Ebeam sterilization significantly alters the biomechanical properties and the early remodelling process of treated grafts in vivo. Therefore, this sterilization method cannot be recommended for clinical application. As substantial changes in the remodelling are inherent in this study, care in the rehabilitation of even low-dose sterilized allografts, used for ACL reconstruction, is recommended.

Structural, optical and compositional stability of MoS2 multi-layer flakes under high dose electron beam irradiation

MoS2 multi-layer flakes, exfoliated from geological molybdenite, have been exposed to high dose electron irradiation showing clear evidence of crystal lattice and stoichiometry modifications. A massive surface sulfur depletion is induced together with the consequent formation of molybdenum nanoislands. It is found that a nanometric amorphous carbon layer, unwillingly deposited during the transmission electron microscope experiments, prevents the formation of the nanoislands. In the absence of the carbon layer, the formation of molybdenum grains proceeds both on the top and bottom surfaces of the flake. If carbon is present on both the surfaces then the formation of Mo grains is completely prevented.

High-dose electron beam sterilization of soft-tissue grafts maintains significantly improved biomechanical properties compared to standard gamma treatment.

Allografts have gained increasing popularity in anterior cruciate ligament (ACL) reconstruction. However, one of the major concerns regarding allografts is the possibility of disease transmission. Electron beam (Ebeam) and Gamma radiation have been proven to be successful in sterilization of medical products. In soft tissue sterilization high dosages of gamma irradiation have been shown to be detrimental to biomechanical properties of grafts. Therefore, it was the objective of this study to compare the biomechanical properties of human bone-patellar tendon-bone (BPTB) grafts after ebeam with standard gamma irradiation at medium (25 kGy) and high doses (34 kGy). We hypothesized that the biomechanical properties of Ebeam irradiated grafts would be superior to gamma irradiated grafts. Paired 10 mm-wide human BPTB grafts were harvested from 20 donors split into four groups following irradiation with either gamma or Ebeam (each n = 10): (A) Ebeam 25 kGy, (B) Gamma 25 kGy, (C) Ebeam 34 kGy (D) Gamma 34 kGy and ten non-irradiated BPTB grafts were used as controls. All grafts underwent biomechanical testing which included preconditioning (ten cycles, 0-20 N); cyclic loading (200 cycles, 20-200 N) and a load-to-failure (LTF) test. Stiffness of non-irradiated controls (199.6 ± 59.1 N/mm) and Ebeam sterilized grafts did not significantly differ (152.0 ± 37.0 N/mm; 192.8 ± 58.0 N/mm), while Gamma-irradiated grafts had significantly lower stiffness than controls at both irradiation dosages (25 kGy: 126.1 ± 45.4 N/mm; 34 kGy: 170.6 ± 58.2 N/mm) (p < 0.05). Failure loads at 25 kGy were significantly lower in the gamma group (1,009 ± 400 N), while the failure load was significantly lower in both study groups at high dose irradiation with 34 kGy (Ebeam: 1,139 ± 445 N, Gamma: 1,073 ± 617 N) compared to controls (1,741 ± 304 N) (p < 0.05). Creep was significantly larger in the gamma irradiated groups (25 kGy: 0.96 ± 1.34 mm; 34 kGy: 1.06 ± 0.58 mm) than in the Ebeam (25 kGy: 0.50 ± 0.34 mm; 34 kGy: 0.26 ± 0.24 mm) and control (0.20 ± 0.18 mm) group that did not differ significantly. Strain difference was not different between either control or study groups (controls: 1.0 ± 0.03; Ebeam 34 kGy 1.04 ± 0.018; Gamma 34 kGy 1.0 ± 0.028; 25 kGy: 1.4 ± 2,0; 34 kGy: 1.1 ± 1.1). The most important result of this study was that ebeam irradiation showed significantly less impairment of the biomechanical properties than gamma irradiation. Considering the results of this study and the improved control of irradiation application with electronic beam, this technique might be a promising alternative in soft-tissue sterilization.

Identification of Mott insulators and Anderson insulators in self-assembled gold nanoparticles thin films.

How the interparticle tunnelling affects the charge conduction of self-assembled gold nanoparticles is studied by three means: tuning the tunnel barrier width by different molecule modification and by substrate bending, and tuning the barrier height by high-dose electron beam exposure. All approaches indicate that the metal-Mott insulator transition is governed predominantly by the interparticle coupling strength, which can be quantified by the room temperature sheet resistance. The Hubbard gap, following the prediction of quantum fluctuation theory, reduces to zero rapidly as the sheet resistance decreases to the quantum resistance. At very low temperature, the fate of devices near the Mott transition depends on the strength of disorder. The charge conduction is from nearest-neighbour hopping to co-tunnelling between nanoparticles in Mott insulators whereas it is from variable-range hopping through charge puddles in Anderson insulators. When the two-dimensional nanoparticle network is under a unidirectional strain, the interparticle coupling becomes anisotropic so the average sheet resistance is required to describe the charge conduction.

Ir6 Clusters Compartmentalized in the Supercages of Zeolite NaY: Direct Imaging of a Catalyst with Aberration-Corrected Scanning Transmission Electron Microscopy

By use of the precursor Ir(CO)2(acac) (acac is acetylacetonate), a ship-in-a-bottle synthesis was used to prepare Ir6(CO)16 and, by decarbonylation, clusters well approximated as Ir6 in the supercages of zeolite NaY. The samples were characterized by infrared and extended X-ray absorption fine structure (EXAFS) spectroscopies and imaged by aberration-corrected scanning transmission electron microscopy with a high-dose electron beam (∼108 e–/Ǻ2, 200 kV), and the catalyst performance was characterized by turnover frequencies for ethene hydrogenation at 298 K and atmospheric pressure. The images characterizing a sample with about 17% of the supercages occupied by decarbonylated nanoclusters indicated clusters well approximated as Ir6, with diameters consistent with such clusters, and some of the images show the clusters with atomic resolution and indicating each of the 6 Ir atoms. The cluster size was confirmed by EXAFS spectra. Two bonding positions of the Ir6 clusters in the supercages were distinguished; ...

Fractionation of high-dose electron beam irradiation of BPTB grafts provides significantly improved viscoelastic and structural properties compared to standard gamma irradiation

Irradiation >30kGy is required to achieve sterility against bacterial and viral pathogens in ACL allograft sterilization. However, doses >20kGy substantially reduce the structural properties of soft-tissue grafts. Fractionation of irradiation doses is a standard procedure in oncology to reduce tissue damage but has not been applied in tissue graft sterilization. Forty-four human 10-mm wide bone-patellar-tendon-bone grafts were randomized into four groups of sterilization with (1) 34kGy of ebeam (2) 34kGy gamma (3) 34kGy fractionated ebeam, and (4) non sterilized controls. Graft´s biomechanical properties were evaluated at time zero. Biomechanical properties were analyzed during cyclic and load-to-failure testing. Fractionation of ebeam irradiation resulted in significantly higher failure loads (1,327±305) than with one-time ebeam irradiation (1,024±204; P=0.008). Compared to gamma irradiation, significantly lower strain (2.9±1.5 vs. 4.6±2.0; P=0.008) and smaller cyclic elongation response (0.3±0.2 vs. 0.6±0.4; P=0.05), as well as higher failure loads (1,327±305 vs. 827±209; P=0.001), were found. Compared to non-irradiated BPTB grafts, no significant differences were found for any of the biomechanical parameters. Non-irradiated controls had significantly lower cyclic elongation response and higher failure loads than ebeam and gamma irradiation. In this study, it was found that fractionation of high-dose electron beam irradiation facilitated a significant improvement of viscoelastic and structural properties of BPTB grafts compared to ebeam and gamma irradiation alone, while maintaining levels of non-irradiated controls. Therefore, this technique might pose an important alternative to common methods for sterilization of soft-tissue allografts.