Non-irradiated Samples Research Articles

Serum miRNA-based signature indicates radiation exposure and dose in humans: A multicenter diagnostic biomarker study

PurposeMouse and non-human primate models showed that serum miRNAs may be used to predict the biological impact of radiation doses. We hypothesized that these results can be translated to humans treated with total body irradiation (TBI), and that miRNAs may be used as clinically feasible biodosimeters. MethodsTo test this hypothesis, serial serum samples were obtained from 25 patients (pediatric and adults) who underwent allogeneic stem-cell transplantation and profiled for miRNA expression using next-generation sequencing. miRNAs with diagnostic potential were quantified with qPCR and used to build logistic regression models with lasso penalty to reduce overfitting, identifying samples drawn from patients who underwent total body irradiation to a potentially lethal dose. ResultsDifferential expression results were consistent with previous studies in mice and non-human primates. miRNAs with detectable expression in this and two prior animal sets allowed for distinction of the irradiated from non-irradiated samples in mice, macaques and humans, validating the miRNAs as radiation-responsive through evolutionarily conserved transcriptional regulation mechanisms. Finally, we created a model based on the expression of miR-150-5p, miR-30b-5p and miR-320c normalized to two references and adjusted for patient age with an AUC of 0.9 (95%CI:0.83–0.97) for identifying samples drawn after irradiation; a separate model differentiating between high and low radiation dose achieved AUC of 0.85 (95%CI: 0.74–0.96). ConclusionsWe conclude that serum miRNAs reflect radiation exposure and dose for humans undergoing TBI and may be used as functional biodosimeters for precise identification of people exposed to clinically significant radiation doses.

Structural organization and properties of surface layers of WC–Co hard alloys after pulsed laser processing

The article presents the metal-physical studies results of the structure formation effects in surface layers in the hard alloys of the WC–Co system under extreme thermal and deformation effects of pulsed laser radiation. It is shown that the structural organization and properties of hard alloys VK6, VK8, VK10 upon radiation treatment with a power density of 175 MW/m2 are determined by state of the zones which are formed around carbide inclusions due to the various kinds of stresses appearance at the “carbide-bond” composition boundaries, including thermostrictive and phase stresses. The result is dissolution of the carbides boundary zones due to contact melting, which is accompanied by mutual mass transfer of atoms at the boundaries in the “carbide-bond” system with the possible formation of a thin amorphous-like super hard shell. These processes make it possible to create compositions in hard alloys with a set of differentiated properties specified by varying the laser treatment process parameters and composition of the starting materials. After laser alloying with a radiation power density of 200 MW/m2, temperature gradients and thermal stresses appearing in the surface layers of hard alloys with coatings (cobalt, nickel) contribute to convective mixing of the molten coating components and their penetration into the hard alloy to a depth of more than 20 μm. Simultaneously, despite the extremely short laser pulse time (10–3 s), mass transfer of tungsten, carbon and titanium atoms from the melted boundary zones of carbides to the adjacent bond zones with their hardening is possible in the irradiated zones. It was established that after high-temperature laser heating, carbides, in contrast to the initial ones, achieve a globular shape of grains. They are dispersed, and stoichiometric characteristics change in the local zones bordering the bond (the complex type carbide CoxWyCz is formed). As a result, due to these processes, the surface layers’ viscosity of hard alloys and the irradiated products performance increase. Compared to non-irradiated samples of hard alloy, the ultimate strength increases by 15 %, strength and durability – by 30 – 40 %.

The effect of Cobalt-60 gamma irradiation on dielectric parameters and junction features of the Al/Orange G/p-Silicon diode

In this study, an Al/Orange G (OG)/p-Si device was constructed using a solution processing method. The electronic and interfacial features of the Al/OG/p-Si structure under 60Co gamma radiation were determined using the Cheung and Norde techniques. The barrier height (ϕ b), ideality factor (n), and series resistance (Rs) of the Al/OG/p-Si diode were computed from the current-voltage (IV) measurements. Then, the n and ϕ b parameters were extracted as n = 2.65 ± 0.07 and ϕ b = 0.76 ± 0.05 eV from the IV results for the irradiated Al/OG/p-Si structure. It has been seen that these parameters were higher than those of the non-irradiated sample. In addition, it was observed that the rectification ratio of the diode decreased after irradiation, particularly in the wide voltage region. Moreover, the capacitance-voltage (CV) measurements showed that the capacitance values of the irradiated Al/OG/p-Si device increased, and the conductance (G) values in the inversion section for low frequencies increased because of the formation of electron-hole pairs or crystalline changes after irradiation. Furthermore, the irradiated and non-irradiated samples were evaluated by X-ray diffraction (XRD), and shifts in the diffraction angles and traces of microstructural changes were observed in the irradiated samples. Thus, it has been found that the radiation has remarkable effects on the dielectric parameters and the electronic and microstructural features of the Al/OG/p-Si structure.

THE ACTIVATION OF ANIONIC DYE ADSORPTION AFTER UV IRRADIATION OF INDIVIDUAL AND BINARY XEROGELS OF ALUMINUM AND ZIRCONIUM OXIDES

Mesoporous xerogels of hydrated individual and binary oxides of aluminum (A) and zirconium (Z) were obtained by hydrolysis sol-gel method after drying at 180 °C of a hydrogel synthesized from aluminum nitrate and zirconium oxychloride in the presence of polyvinylpyrrolidone. The samples were examined by IR spectroscopy, SEM, XRD, BET/BJH. It was found that the xerogels are X-ray amorphous. The particles have a hierarchical structure, the specific surface in a series (number and mol.%) of samples A (1) < 65AZ (2) < 35AZ (3) < Z (4) increases exponentially from 21 to 298 m2/g. The pore diameter is 4-6 nm. Photoactive aluminum oxohydroxide (δAlOOH = 1070 cm-1) is registered only in samples 1 and 2. Adsorption from an aqueous solution using the example of anionic dye methyl orange was determined by spectrophotometer for long-time (24 h) and dynamic (10 min) regime. In both cases, Gibbs adsorption of Гm (μmol/g) increases in a number of samples 1 < 2 < 3 < 4. The value of ГS (μmol/m2) in the same series decreases sharply. Therefore, the adsorption centers of Al+3 and Zr+4 have different activity. It is shown that only in the case of AZ samples a photo activated adsorption rise after UV irradiation of sorbents with a mercury lamp for 10 min of duration. Kinetic adsorption curves for samples without and with UV treatment correspond to the pseudo-second-order equation with Langmuir-type two-fold adsorption model. The parameters of this equation Гmax (monolayer capacity) and W0 (initial adsorption rate) increase in a series of non-irradiated samples 1 < 2 < 3 < 4. The effect of UV activation, as the ratio of Гmax and W0 after and before irradiation, augments in the sequence Z < A < 35AZ < 65AZ (for 65AZ sample the growth of Гmax and W0 is 2.4 and 1.8 times, while the adsorption rate constant k2 decreases tenfold). Comparison of adsorption after 24 h with Гmax showed a linear decrease in the ratio Г24/Гmax for unirradiated sorbents A (2.9) > 65AZ (2.2) > 35AZ (1.6) > I(1.0). This result is explained by adsorption-induced deformation of the xerogel framework, which is greatest in Al2O3 and absent in ZrO2. For citation: Vakhrushev N.E., MIkhalenko I.I., Podzorova L.I. The activation of anionic dye adsorption after UV irradiation of individual and binary xerogels of aluminum and zirconium oxides. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 6. P. 61-68. DOI: 10.6060/ivkkt.20236606.6744.

Evaluation of HPK [formula omitted] planar pixel sensors for the CMS Phase-2 upgrade

To cope with the challenging environment of the planned high luminosity upgrade of the Large Hadron Collider (HL-LHC), scheduled to start operation in 2029, CMS will replace its entire tracking system. The requirements for the tracker are largely determined by the long operation time of 10 years with an instantaneous peak luminosity of up to 7.5 × 1034cm−2s−1 in the ultimate performance scenario. Depending on the radial distance from the interaction point, the silicon sensors will receive a particle fluence corresponding to a non-ionising energy loss of up to Φeq= 3.5 × 1016cm−2. This paper focuses on planar pixel sensor design and qualification up to a fluence of Φeq = 1.4 × 1016cm−2.For the development of appropriate planar pixel sensors an R&D program was initiated, which includes n+-p sensors on 150mm (6”) wafers with an active thickness of 150µm with pixel sizes of 100×25 µm2 and 50×50 µm2 manufactured by Hamamatsu Photonics K.K. (HPK). Single chip modules with ROC4Sens and RD53A readout chips were made. Irradiation with protons and neutrons, as well was an extensive test beam campaign at DESY were carried out. This paper presents the investigation of various assemblies mainly with ROC4Sens readout chips. It demonstrates that multiple designs fulfil the requirements in terms of breakdown voltage, leakage current and efficiency. The single point resolution for 50×50 µm2 pixels is measured as 4.0µm for non-irradiated samples, and 6.3µm after irradiation to Φeq = 7.2 × 1015cm−2.

Volatolomic approach by HS-SPME/GC–MS and chemometric evaluations for the discrimination of X-ray irradiated mozzarella cheese

In this work, an untargeted screening of the volatile profile of X-ray irradiated mozzarella cheese was carried out to study the possible radio-induced modifications. A Central Composite Design (CCD) for Response Surface Methodology (RSM) was employed to optimise the HS-SPME analysis of volatile organic compounds (VOCs). The optimised HS-SPME conditions, in terms of sample amount (5.0 g), extraction temperature (50 °C) and extraction time (75 min), were used to analyse non-irradiated and irradiated samples at three dose levels, 1.0, 2.0, 3.0 kGy. Partial Least Squares-Discriminant Analysis (PLS-DA) and Linear Discriminant Analysis (LDA) were applied to explore the variation of volatile profile with respect to the X-ray irradiation treatment. Both methods highlighted a high discriminant capability with excellent values of accuracy, specificity and sensitivity, demonstrating the effectiveness of the volatolomic approach to evaluate the variations induced by the treatment and allowing to select a total of 35 VOCs as potential irradiation markers.

Physico-Chemical Changes Induced by Gamma Irradiation on Some Structural Protein Extracts.

In this study, the effect of gamma irradiation (10 kGy) on proteins extracted from animal hide, scales, and wool was evidenced by calorimetric (μDSC) and spectroscopic (IR, circular dichroism, and EPR) methods. Keratin was obtained from sheep wool, collagen and bovine gelatin from bovine hide, and fish gelatin from fish scales. The μDSC experiments evidenced that gamma irradiation influences the thermal stability of these proteins differently. The thermal stability of keratin decreases, while a resistance to thermal denaturation was noticed for collagen and gelatins after gamma irradiation. The analysis of the IR spectra demonstrated that gamma irradiation determines changes in the vibrational modes of the amide groups that are associated with protein denaturation, most meaningfully in the case of keratin. As evidenced by circular dichroism for all proteins considered, exposure to gamma radiation produces changes in the secondary structure that are more significant than those produced by UV irradiation. Riboflavin has different effects on the secondary structure of the investigated proteins, a stabilizing effect for keratin and fish gelatin and a destabilizing effect for bovine gelatin, observed in both irradiated and non-irradiated samples. The EPR spectroscopy evidences the presence, in the gamma-irradiated samples, of free radicals centered on oxygen, and the increase in their EPR signals over time due to the presence of riboflavin.

Long-term high-temperature exposure effects on mechanical properties and structure of the 42XNM alloy after neutron irradiation in the VVER-1000. Part 1. Mechanical tests

The paper presents the results of mechanical tests of ring specimens made of the 42XNM alloy after irradiation as part of the control and protection system of the VVER-1000 reactor to a damaging dose of ~12 dpa at a temperature of ~350°C and subsequent isothermal annealings in the temperature range of 400– 1150°C (heating and holding for ~2 h). A model was constructed and validated by the finite element method, it describes the mechanical characteristics of irradiated and non-irradiated samples from the 42XNM alloy during tests in the temperature range from 500 to 1000°C. The model was used to plot the temperature dependences of the maximum local plastic deformation and the yield strength of the material under study.

Irradiation effects on phenolic content in Bulgarian honey bee products and correlation to the antioxidant activity

Abstract Bee pollen and bee bread are considered for a good source of nourishing and polyphenol substances which may act as powerful antioxidants. Some main phenolic compounds of studied non-irradiated and irradiated samples were identified and compared by high performance liquid chromatography (HPLC). The effects of irradiation treatment of bee pollen and bee bread on their phenolic content were studied. For this purpose, the samples were γ-irradiated with 2, 5, 10 and 20 kGy. The results show that the ionizing radiation affect phenolic content of analyzed samples depends on the dose and the chemical composition of honey bee product. The identified phenolic substances and changes in their amount after irradiation were related to free radical scavenging activity (FRSA) of studied samples. FRSA of bee pollen and bee bread were determined by electron paramagnetic resonance (EPR). Gamma treatment with 5 kGy has a positive effect on antioxidant potential at both honey bee products.

Highly Selective Polyene-Polyyne Resistive Gas Sensors: Response Tuning by Low-Energy Ion Irradiation

The formation of polyene-polyyne-based nanocomposites by dehydrohalogenation of the drop-cast-deposited polyvinylidene fluoride, assessment and ion-induced tailoring of their gas sensing properties are reported. The investigated structure was analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy, transmission electron microscopy and Fourier-transform infrared spectroscopy, revealing the thickness-dependent incomplete dehydrofluorination of the structure and its porosity induced by KOH treatment. The polyene-polyyne structures modified by low-energy Ar+ were studied by SEM and Raman spectroscopy, which showed the morphology variation, the shortening of chains and the graphitization of samples. The resistive gas sensing properties of the samples were analyzed at room temperature, revealing selective sensing of ammonia vapor by non-irradiated sample and the enhancement of the sensing properties for ethanol and water vapor after ion irradiation. With the ion dose enlargement, the change in the sensing response from electrical conductivity increase to decrease was observed for ammonia and ethanol, allowing us to discuss the origin and tunability of the sensing mechanism of the samples.

An emerging application of gamma irradiation in reducing higher levels of hydroxymethyl furfural (toxic hazard) in date syrup and enhancing the microbial and nutritional quality.

Date syrup is a very rich nutritional and medicinal product. It can be used alone or mixed with other food products. Now, it is widely used as a natural sweetener instead of harmful sugar in several food products. However, date syrup contains higher levels of 5-hydroxyl methyl furfural (5-HMF) (heat-induced toxicant). HMF is normally formed during processing via Maillard reaction as a result of heating. Thus, the present study aims at investigating the effect of gamma irradiation in reducing HMF content and improving the quality properties of date syrup. Date syrup samples (commercial) were irradiated at different doses (15, 20 and 25 kGy). HMF content was determined using the HPLC method. The obtained results showed that γ-irradiation reduced the toxic compound (HMF) in date syrup, where irradiation dose (20 kGy) recorded the lowest HMF level (1956.40 mg/kg) with a reduction percentage of 46.96% compared to the non-irradiated sample. While the non-irradiated sample revealed the highest level of HMF and bacterial growth. Therefore, γ-irradiation is considered an effective treatment that reduces HMF using a particular dose (20 kGy) and prevents microbial growth (20-25 KGy). Furthermore, it may increase the nutritional value by increasing minerals' bioavailability (15 kGy).

Thermophysical study of neutron irradiated silicon nitride nanoparticles

Silicon nitride (Si3N[Formula: see text] nanoparticles were irradiated with neutrons at different energy fluxes. Differential thermal analysis of non-irradiated and neutron irradiated samples was performed in the temperature range of 300–1400 K. Based on the obtained experimental results, relevant thermophysical parameters were calculated and discussed in detail. All analyses were comparatively discussed for non-irradiated and neutron irradiated nano-Si3N4 particles. On the basis of endotherms observed in DTA spectra, entropy and enthalpy in Si3N4 are interpreted in detail. Compared with the non-irradiated sample, slightly negative values of enthalpy indicate the formed [Formula: see text]P isotope due to neutron irradiation. In the mentioned temperature range, the values of the free Gibbs energy were calculated for all samples, and it was determined that it is varied around zero up to 600 K. Moreover, the effect of neutron transmutations on heat transfer in Si3N4 nanoparticles has been studied.

Impact of neutron irradiation on electronic carrier transport properties in Ga2O3 and comparison with proton irradiation effects

The minority charge carrier transport in beta gallium oxide (-Ga2O3) before and after exposure to neutrons from a 241Am-Be source was studied. Cathodoluminescence (CL) spectroscopy and current–voltage (I-V) characteristics were used to study minority carrier behavior. High energy radiation affects minority carrier properties through the production of carrier traps that reduce the conductivity and mobility of the material. In this paper, we report the effects of neutron radiation in silicon-doped -Ga2O3, using rectifiers or transistors as the measurement platform. The thermal activation energy of the reference (non-irradiated) sample was 40.9 meV, which is ascribed to silicon-donors. CL measurements indicate a slightly indirect bandgap energy of 4.9 eV. Neutrons create disordered regions in -Ga2O3 rather than just point defects, resulting in the lowest carrier removal rate because of the lowest average non-ionizing energy loss. The neutron irradiation caused an increase in reverse bias leakage current in rectifiers and a carrier removal rate of 480 cm−1 but had little effect on reverse recovery switching time. Differences in CL spectra were observed between vertical and lateral device structures, emphasizing the importance of impurities and defects in the starting material. The neutron energies in the Am-Be source range up to 11 MeV, with an average energy between 4 and 5 MeV (Figure 1). We also contrasted neutron damage with the effects of irradiation with 10 MeV protons. Under 10 MeV proton irradiation, the thermal activation energies increase. This is attributable to high order defects and their influence on carrier lifetimes. The measurements show that -Ga2O3 is more resistant to radiation damage than other wide bandgap semiconductors due to its higher displacement threshold energy, which is inversely proportional to the lattice constant.

Efficiency of post-preparation treatment by gamma radiation to guarantee quality properties of plum molasses

Purpose This study aimed to assess specific gamma irradiation doses to be applied as a post-preparation process to assure the chemical, physical and sensory properties of plum molasses (PM). Materials and methods Samples of PM were treated with 0, 3, 6 and 9 kGy in a 60Co gamma irradiation plant. Proximate composition, chemical, the physical and sensory determination was accomplished immediately after treatment. Results Our results showed that, the moisture content of PM were significantly (p < .05) rise by treating with 3 kGy. Whereas, ash and reducing sugar quantity of PM was significantly (p < .05) decreased by treatment at the same dose (3 kGy). Irradiation treatment induced small and not significant alterations (p > .05) in crude protein, crud fat, and total sugar of PM. The chemical and physical parameters including; total acidity (TA), pH, volatile basic nitrogen (VBN), total soluble solids (TSS) (%, Brix), viscosity and color, which were elected as the indicators of quality, were all well within the recommended values for PM treated with 0, 3, 6 and 9 kGy. Sensory determination indicated no significant (p > .05) alterations between irradiated samples and non-irradiated samples of PM. Conclusion Irradiation treatment at 3 kGy was considered as acceptable to be used for the preservation purpose of PM without modifying their quality properties.

The influence of γ-irradiation on molecular structure and mass attenuation coefficients of γ-Al2O3 nanoparticles

In this research, γ-Al2O3 nanoparticles (NPs) were synthesized by using the sol–gel process. The photon attenuation properties of these NPs were obtained by measuring the linear and mass attenuation coefficients (μl, μm) at different photon energies. In addition, the theoretical values of μm for γ-Al2O3 micro-particles were calculated using the WinXCom computer program and compared with the experimental values of μm for NPs of γ-Al2O3. Furthermore, in order to evaluate the impact of γ-irradiation on these NPs, the experimental values of μl and μm for γ-Al2O3 NPs, before and after receiving 20 kGy dose of γ-irradiation, were investigated. It was observed that μm of γ-Al2O3 NPs decreases after receiving γ-irradiation because of increasing the photon’s energy, which indicates the changes in the molecular structure of NPs after γ-irradiation. Moreover, the structural properties of NPs were evaluated by UV–Vis spectroscopy, x-ray diffraction patterns, and scanning electron microscopy images. UV–Vis spectroscopy showed an absorption peak at 212.5 nm before γ-irradiation, and the absorption peak of NPs disappeared when γ-irradiation was started. The average crystalline size was determined to be 3.65 nm in the sample before γ-irradiation and 9.29 nm in the sample with the maximum dose of 20 kGy. The results of scanning electron microscopy show an increase in particle size from 6.5 nm in a non-irradiated sample up to 9 nm in a sample with the highest γ-irradiation dose.

Impact of radiotherapy on the morphological and compositional structure of intra-radicular dentin

Considering the side effects in the oral cavity and dental structures of radiotherapy (RDT) for head and neck cancer, this study aimed to evaluate the effects of RDT on the root dentin concerning the obliteration of dentinal tubules, the inorganic composition of intra-radicular dentin, and the integrity of collagen fibers. Thirty human canines were selected from a biobank and randomly divided into two groups (n=15). The samples were sectioned buccolingually, and a hemisection was used for structural analysis by scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometer (EDS). Low-vacuum SEM images were obtained at 2000-x magnification to observe the obliteration of the dentinal tubules. Moreover, compositional evaluation was performed using EDS. After RDT, the SEM and EDS analyses were repeated using the same methodology. RDT was applied fractionally at 2 Gy per day, 5 days per week, for 7 weeks, resulting in a total dose of 70 Gy. The collagen integrity of the irradiated and non-irradiated samples was analyzed using Masson's trichrome and picrosirius red staining polarization microscopy. Samples subjected to RDT exhibited dentinal tubule obliteration (p < 0.001); low integrity of type I and III collagen fibers (p < 0.05); compositional reduction of calcium (p = 0.012), phosphorus (p = 0.001), and magnesium (p < 0.001); an increased Ca/P ratio (p < 0.001). RDT affects the structure of dentinal tubules, the inorganic composition of intra-radicular dentin, and the collagen fiber integrity in the root dentin, which may interfere with the effectiveness and durability of dental procedures.

Gamma ray irradiated binuclear and mononuclear transition metal complexes with polydentate ligand: Template synthesis, spectral, XRD, morphology, solid electrical conductivity and antimicrobial activity

In this work, new binuclear Fe(III), Ni(II) and mononuclear Cu(II) Schiff base complexes that obtained via template condensation of Fe(III), Ni(II) and Cu(II) chlorides with N1-(3-aminopropyl) propane-1,3-diamine and 1,3-diphenylpropane-1,3‑dione (1B, 2B, 3B), respectively were prepared and well investigated. The structure of the complexes was elucidated by means of microanalyses, various spectroscopic techniques (FT–IR, UV/Vis, X–ray diffraction), thermal (TG/DTG), molar conductivity and magnetic moment measurements, Fe(III), Ni(II) complexes have an octahedral structure, while Cu(II) complex adopts distorted square pyramidal geometry. To study γ– irradiation induced modifications, powder sample of these complexes was exposed to high energetic γ–ray irradiation at a dose of 20 kGy, (hereafter referred to as 1A, 2A, 3A, respectively). Physico-chemical properties of irradiated samples were also investigated by the aforementioned tools. The results revealed no remarkable change in the molar conductivity values and little shift of the peak position and the intensity for FT–IR and electronic spectra as a result of the distortion of lattice planes. Also, TG/DTG studies revealed decreasing in the thermal stability for all irradiated samples. From the powder XRD data for non-irradiated and γ–irradiated Ni(II) (2B, 2A) and Cu(II) (3B, 3A) complexes, average crystallite size (D) and dislocation density (δ) were calculated, the γ–irradiation resulted in decrease in the crystallite size for Ni(II) (2A) complex. The irradiated (3A) showed changes in the surface morphology compared to its non-irradiated one. The solid state electrical conductivity of non-irradiated and γ–irradiated Ni(II) complexes have been investigated. Furthermore, the non-irradiated samples (1B, 3B) and their γ–irradiated (1A, 3A) were assayed for their antibacterial property against Gram–positive as Staphylococcus aureus, Gram– negative as Escherichia coli and antifungal property against fungi as Candida albicans.

γ-irradiation induced effects on structural, morphological and photoluminescence properties of PEO-PVA blended polymer films

PEO/PVA blends have been prepared to investigate the effect of gamma rays on the structural, morphological and photoluminescence properties. The studies of non-irradiated and irradiated samples with radiation doses of 10 kGy were examined by using XRD, ATR-FTIR, Optical microscopy and PL. Gamma photons induced important chemical rearrangements, especially by PVA hydroxyl groups. We found that the crystallinity rate is strongly influenced by radiation. In this context, one could predict that the immiscibility of PVA with PEO and the interactions between the chains are of the electrostatic type. A structural-scale disturbance due to the radical formation leads to spherulitic texture modifications of the PEO. Due to the luminescence properties, the blend samples behave like core-shell nanoparticles. This phenomenon is due to the fact that the PVA polymer played the role of shell. Irradiation makes it possible to obtain well-ordered spherulites and to get a high pore density. The irradiated blend showed a higher quantum yield. The significant chemical and morphological changes caused by gamma radiation favored the optical recombination of hydroxyl groups.

Microfluidics unveil nucleation and growth in the radiolytic synthesis of colloidal silver and allow X-ray detection with nanoclusters

We developed a two-stage microfluidic reactor consisting of one hot and one cold region to systematically investigate a radiolytic method to synthesize colloidal silver and to improve the sensitivity of radiation dosimeters based on the Ag nanoparticles plasmon intensity. The microfluidic approach avoided growth during the heating stage, resulting in the total absence of a plasmon band for non-irradiated samples, greater control of the particle size distribution, and decreased minimal detectable dose. Doses as low as 0.2 Gy could be detected with sensitivities higher than the reported in the literature. This is a great achievement once most chemical dosimeters, besides 3D gels, are not sensitive to such low doses. Samples prepared in the microreactor and exposed to doses from 0 to 0.75 Gy presented an unexpected absorption band above 500 nm and a fluorescence emission around 380 nm, evidencing the presence of Ag nanoclusters (AgNCs). Both, absorption and emission bands from AgNCs, increase in the 0-0.75 Gy range, suggesting that nucleation predominates in the microreaction stage and in the radiolytic step for doses below 1 Gy. Decreased fluorescence intensity and undetected absorption above 500 nm indicate that growth prevails for doses ≥1 Gy. Thus, our work presents a novel way to measure doses based on silver nanoclusters, including both absorption and emission as dosimetric parameters. Besides unveiling nucleation and growth mechanisms associated to nano clusters and particles formation in this radiolytic microreaction, the results put the spotlight on new possibilities for enhanced radiation detection employing AgNCs.

Изменение состава и коррозионно-электрохимических свойств хромоникелевой стали 03Х18Н11 при имплантации ионов аргона, кислорода и азота

The effect of implantation of argon, oxygen and nitrogen ions on the physicochemical structure of the surface and the corrosion-electrochemical behavior of chromium-nickel steel 03Cr18Ni11has been studied. Methods of electrochemical polarization (EP), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used. Ion implantation of argon, oxygen and nitrogen leads to an increase in the corrosion resistance of steel 03Cr18Ni11 both in a neutral environment and in the presence of a corrosion activator (chloride anions), while irradiation with argon ions is most effective. It was found that after implantation of argon ions, a partial etching of the steel surface occurs, i.e. an increase in the true surface. This, in turn, facilitates the onset of the passive state. At the same time, the use of oxygen and nitrogen ions leads to smoothing of the surface. AFM data indicate that the studied steel treated with argon ions exhibits the greatest resistance to local corrosion. The implantation of oxygen and argon ions reduces the overall corrosion to the greatest extent. It is important to note that deep craters and traces of pitting corrosion do not form on the surface of the steel. The XPS data show that after ion implantation, there was a change in the concentration of the elements that make up the steel in the near-surface layers of the material in the depth of the implanted layer compared with the non-irradiated sample. It is established that the surface layers of steel are enriched with chromium atoms during ion implantation. This process occurs most intensively when samples are treated with argon ions. In this case, mixed chromium and iron oxides are formed, contributing to the passivation of the steel surface. Also, the process of ion implantation is accompanied by oxidation of the surface of the steel under study. This is confirmed by an increase in the oxygen content in the surface layers. To the greatest extent, this process occurs during implantation of oxygen ions. After corrosion tests, an increased chromium content is also observed on the surface of steel treated with Ar+ ions, which confirms the formation in this case of strong chromium oxides that remain on the surface during the corrosion of steel. The analysis of the fine structure of the XPS spectra showed that under the action of argon ions, the oxygen of surface oxides is redistributed in favor of chromium atoms and the formation of strong mixed iron and chromium oxides of the spinel type, including Fe2+, Fe3+, Cr3+ and Cr6+ compounds. It is important to note that although chromium oxides are also formed during oxygen implantation and in the same quantities as during argon implantation, the protective properties of the resulting compounds are noticeably lower. Therefore, not only the chemical composition is important, but also the structure of the resulting layers. It can be assumed that the high kinetic energy of heavy argon ions affects both the formation of a developed surface relief and the formation of strong mixed iron and chromium oxides of the spinel type.