Radiation-induced Decomposition Research Articles

Solubility Change Behavior of Fluoroalkyl Ether-Tagged Dendritic Hexaphenol under Extreme UV Exposure.

This study focuses on the discovery of a single-component molecular resist for extreme ultraviolet (EUV) lithography by employing the ionizing radiation-induced decomposition of carbon-fluorine chemical bonds. The target material, DHP-L6, was synthesized by bonding perfluoroalkyl ether moieties to amorphous dendritic hexaphenol (DHP) with a high glass transition temperature. Upon exposure to EUV and electron beam irradiation, DHP-L6 films exhibited a decreasing solubility in fluorous developer media, resulting in negative-tone images. The underlying chemical mechanisms were elucidated by Fourier transform-infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy, and nanoindentation experiments. These analyses highlighted the possible electron-induced decomposition of C-F bonds in DHP-L6, leading to molecular network formation via recombination of the resulting C-centered radicals. Subsequent high-resolution lithographic patterning under EUV irradiation showed that DHP-L6 could create stencil patterns with a line width of 26 nm at an exposure dose of 110 mJ cm-2. These results confirm that single-component small molecular compounds with fluoroalkyl moieties can be employed as patterning materials under ionizing radiation. Nonetheless, additional research is required to reduce the relatively high exposure energy for high-resolution patterning and to enhance the line-edge roughness of the produced stencil.

In-situ investigation of damage evolution and mechanism in composite propellants under monochromatic X-ray irradiation

Synchrotron radiation monochromatic X-ray computed tomography (CT) is a powerful tool for in-situ characterization of the internal microstructure evolution in composite materials. However, prolonged X-ray irradiation during long-term in-situ studies may affect the structure and properties of material. While the effects of white beam irradiation have been widely investigated, the specific damage mechanisms and material sensitivity to monochromatic X-ray irradiation, particularly in composite materials like propellants, are not well understood. In this study, we identify the threshold irradiation time that triggers radiation damage in PBT propellant and observe the accumulation and worsening of damage over time, primarilyinitiated by ether bond cleavage, leading to radiation-induced decomposition and increased internal porosity. This resulted in a significant reduction in the mechanical strength of PBT propellant, particularly under prolonged exposure to synchrotron radiation. In contrast, the inert binder system HTPB propellant exhibited better radiation stability. Our study highlights the importance of considering both radiation-induced damage and material X-ray sensitivity when designing in-situ synchrotron radiation CT experiments for composite materials, and suggests that the development of dynamic experimental methods to further reduce the risk of radiation damage for high-reliability in-situ assessment of material properties, as well as the need for careful consideration of radiation effects in the design and safety evaluation of solid propellant systems working in extreme circumstance.

Effects of acid generator anions on radiation-induced decomposition and dissolution kinetics of chemically amplified resists

Chemically amplified resists (CARs) are widely used in lithography for manufacturing semiconductor devices. To reduce the occurrence of stochastic defects in CARs, increased acid generator concentration is required. In this study, we investigated the effects of acid generator anions on the radiation-induced decomposition of acid generators using electron pulse radiolysis and γ-radiolysis methods. Their effects on the dissolution dynamics of poly(4-hydroxystyrene) (PHS) films were also investigated using contact angle measurement and quartz crystal microbalance methods. Triphenylsulfonium trifluoromethanesulfonate, triphenylsulfonium nonafluoro-1-butanesulfonate, triphenylsulfonium 4-toluenesulfonate, and triphenylsulfonium salicylate, were used as acid generators or photodecomposable quenchers. The anions showed minimal effect on the decomposition of the acid generators and photodecomposable quenchers; however, they influenced the surface free energy, dissolution kinetics of the PHS films, and water penetration into the PHS films. In particular, the effect of salicylate on the dissolution kinetics of PHS films is significant.

Effects of substituents in triphenylsulfonium cation on its radiation-induced decomposition and dissolution kinetics of chemically amplified resists

The suppression of stochastic effects is the most important issue in the development of resist materials. To suppress the stochastic effects in chemically amplified resists, a high acid generator concentration is required, which, however, likely affects the dissolution kinetics of resist films. In this study, the effects of substituents in the phenyl group of triphenylsulfonium triflate (TPS-TF) on the decomposition and dissolution kinetics of poly(4-hydroxystyrene) (PHS) films dispersed with monosubstituted TPS-TF were investigated using electron pulse radiolysis, γ-radiolysis, electron radiolysis, and quartz crystal microbalance. The phenyl group of TPS-TF was substituted with fluorine, iodine, or methyl groups at the fourth position. The electronegativity of the substituents had little effect on the reaction rate of the methanol-solvated electrons. The dipole moment of the TPS cation affected the C-S bond cleavage. The monosubstitution of the phenyl group of the TPS cation significantly affected the dissolution rate of the PHS films.

Production of Low-Molecular-Weight Organic Components by the Microwave Pyrolysis of Peat

A facility for conducting experiments on the microwave (MW) pyrolysis of peat at a source operating frequency of 2.45 GHz has been developed. The MW pyrolysis of peat for the production of low-molecular-weight organic components has been experimentally studied. The products of peat MW radiationinduced decomposition were determined, and reaction schemes for the degradation of peat components were proposed. A carbonaceous residue with relative carbon, hydrogen, nitrogen, and sulfur contents of 83–85, 4–5, 2–3, and 0.3 wt %, respectively, was obtained.

Spectroscopy and radiation-induced chemistry of an atmospherically relevant CH2F2…H2O complex: Evidence for the formation of CF2…H2O complex as revealed by FTIR matrix isolation and ab initio study

Difluoromethane is considered among the environment friendly alternatives to the ozone depleting chlorofluorocarbons. Due to its chemical inertness and lack of UV absorption above 200 nm, this compound can easily come to the upper layers forming complexes with widely abundant atmospheric components, such as water. The radiation-induced degradation of this compound and its complexes may be significant for reliable prediction of its long-term evolution in the environment as well as for development of new ways for its removal. In this work we have studied the vibrational spectroscopic properties and mechanisms of the radiation-induced decay of the CH2F2⋯H2O under the action of X-rays using matrix isolation FTIR spectroscopy and ab initio calculations. The IR spectrum of the complex in an argon matrix was characterized for the first time and assigned to a hydrogen-bonded structure with a binding energy of 11.1 kJ/mol (2.65 kcal/mol) (CCSD(T)/CBS level of theory). Complexation with water leads to a certain suppression of the efficiency of the radiation-induced decomposition of difluoromethane. The obtained results provide evidence for the radiation-induced formation of previously unreported CF2⋯H2O complex (in addition to other oxygen containing molecules, such as COF2 and CO). As demonstrated by calculations, the new difluorocarbene complex reveals a hydrogen bond and it is characterized by a binding energy of 5.73 kJ/mol (1.37 kcal/mol) (CCSD(T)/CBS level of theory).

Influence of Neutron Irradiation on the Characteristics of Phase Transitions in Multifunctional Materials with a Perovskite Structure (A Review)

Exposure to neutron radiation is an efficient way to enter dosed amounts of defects into the crystal and real structures of advanced inorganic materials. Thus-gained experimental data are of importance for both fundamental radiation materials science and for finding ways of usefully modifying the effect of radiation on the properties of practically important multifunctional materials with the perovskite structure. The review considers the specificity of the effect of exposure to neutron radiation on the parameters of crystal and real structures and on the multifunctional (ferroelectric, superconducting, nonlinear optical, magnetic, and other) properties of crystals of the perovskite family that experience various structural phase transitions. The review dwells on the effect of radiation defects on variations of the local and macroscopic properties of crystals, reflected in the anomalies of these properties in phase-transition regions. Ferroelectric perovskite crystals are shown to be particularly susceptible to defects. The main types of radiation-induced structural states are considered, including their formation mechanisms and patterns. Correlation relations between the structural alteration upon radiation exposure and the evolution of phase-transformation temperatures are considered. It is shown that variable irradiation parameters (dose, radiation annealing, impurity content, and concentration of a certain type of initial defects) offer a means to control the kinetics of radiation rearrangement and, ultimately, the radiation resistance of the structure. In addition, taking these factors into account, one can provide conditions for the generation of almost any metastable structural state, close to those formed in intact (non-irradiated) crystals at the pre-transition stage, that would be stable at room temperature. The study of effects of neutron irradiation by precision X-ray structural analysis shows that the structural states that occur under radiation exposure are stable over a wide temperature range, including room temperature, and the stability of metastable states, as a rule, increases with the radiation fluence. These radiation-induced states are actually new structural states, intermediate between low-temperature and high-temperature polymorphs of perovskite crystals. The analysis of literature data implies that the radiation-induced structural rearrangement, amorphization, and decomposition of the initial compound are in many cases competing processes, the activity of which depends on the neutron irradiation fluence and temperature. A decrease in exposure temperature often slows down the decomposition and suppresses the attendant deformation of the crystal, which is essential for the implementation and identification of structural alterations in irradiated crystals.

Radiation-induced transformations of HCN⋯C2H2, HCN⋯C2H4 and HCN⋯C2H6 complexes in noble gas matrices: Synthesis of C3HxN molecules in cryogenic media

The nitrogen containing molecules of general structure C3HxN are important astrochemical species, which occur in interstellar and other extraterrestrial media. In this work, we have first demonstrated the formation of a number of nitriles and isonitriles (C2H3CN, C2H3NC and C2H5NC) through a direct radiation-induced synthesis from the matrix isolated intermolecular complexes HCN⋯C2Hn (n = 2, 4, 6) at 6 K. The deposited matrices Ng/HCN/C2Hn (Ng = Ar, Kr or Xe) were irradiated with X-rays and the formation of products was monitored by FTIR spectroscopy. In addition to synthetic products (C3HxN molecules), irradiation results in dehydrogenation of the initial complexes and their isomerization to the corresponding HNC⋯C2Hn complexes. The formation of propionitrile (C2H5CN) also cannot be excluded, although this molecule was not detected experimentally, possibly due to its poor IR absorption coefficients. Cyanoacetylene (HC3N) is accumulated with an induction period and becomes predominating at high absorbed doses, which points to its formation from the radiation-induced decomposition of the primary products. The obtained results suggest new possible routes for formation of nitriles, isonitriles and cyanoacetylene in complex astrochemical ices.

Investigation of structural and optical properties of zirconia dioxide nanoparticles by radiation and thermal methods

The X-ray diffraction (XRD) spectrum of the nano-ZrO2compound was drawn, the crystal structure was determined at room temperature and under normal conditions. Radiation-thermal decomposition of water on nanosized ZrO2in the temperature range of [Formula: see text]–673 K has been studied by Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. It has been shown that nanosized zirconium dioxide adsorbs water via the molecular and dissociative mechanisms. Intermediate products of the radiation-induced heterogeneous decomposition of water, namely, the molecular oxygen and hydrogen peroxide radical ions, zirconium hydride, and hydroxyl radicals have been detected. A comparative analysis of changes in the absorption bands (ABs) of molecular water and surface hydroxyl groups with temperature has been conducted, and the stimulating role of radiation in the radiation-thermal process of water decomposition has been revealed. With the participation of nano-ZrO2during the radiation-heterogeneous decomposition of water to reveal the role of unbalanced cargo carriers that play the role of energy carriers under the influence of gamma-quantities in nano-ZrO2and nano-[Formula: see text] systems paramagnetic centers, their origin and acquisition kinetics learned by the EPR method.

Radiation-induced transformations of isolated toluene molecules in low-temperature matrices: Towards better understanding of molecular radiation chemistry in condensed phases

The transformations of isolated toluene molecules under X-ray radiolysis in solid noble gas matrices at 6 K were characterized by FTIR spectroscopy. It was found that the efficiency of the radiation-induced decomposition of toluene was generally comparable to that of benzene. Meanwhile, a remarkable matrix effect was observed: toluene is more stable than benzene in an argon matrix, whereas it becomes more sensitive in the case of xenon matrix. This result was ascribed to the increasing role of upper triplet excited states in a xenon matrix. In all the matrices two main radiolysis products observed at moderate absorbed doses were benzyl radical and 5-methylene-1,3-cyclohexadiene (MCHD). Benzyl radical predominates in all the cases, while the relative contribution of MCHD strongly decreases in the row Ar-Kr-Xe. On the basis of this comparison, the formation of MCHD was tentatively attributed to the rearrangement of excited primary toluene radical cations. Possible scheme of the radiation-induced processes is discussed.

All optical formation and decomposition of silver nanoparticles in glass

The process of laser radiation-induced formation and decomposition of Ag nanoparticles in glass is studied. Borosilicate glass samples are fabricated by melt quenching method. Silver nitrate is added in the fabrication stage in amount to form final glass samples with compositions of 1, 1.5, 5, and 10 wt% Ag. The fabricated samples are irradiated by laser pulses delivered by Nd:YAG nanosecond laser system at wavelength of 266 nm. It is found that at certain conditions laser radiation can induce coloration of the irradiated zone which is related to formation of silver nanoparticles. Detailed analyses are performed to characterize the formed nanoparticles. The application of a subsequent laser treatment of the glass samples with already formed nanoparticles can result in transparency recovery. The effect is demonstrated at wavelength of 355 nm of the Nd:YAG laser system. The observed formation and decomposition of nanoparticles are discussed on the basis of the calculated laser-induced heating dynamics and molecular dynamics simulation model for the silver atom motion. Diffusion growth and redox reactions are found to be responsible for the observed effects.

Radiation-Induced Decomposition of Water on the BeO Surface

Radiation-induced decomposition of water in the BeO-adsorbed H2O system at room temperature (T = 300 K) under the conditions of γ-irradiation for different times was studied by Fourier IR spectroscopy. The water adsorption onto BeO was found to occur by the molecular and dissociative mechanisms. Intermediate active products of radiation-induced heterogeneous decomposition of water, beryllium hydrides and hydroxy groups, were detected. The highest radiation-chemical yield of molecular hydrogen, G(H2), was reached at the BeO particle size d ≤ 4 μm.

Degradation of sulfamethoxazole by ionizing radiation: Kinetics and implications of additives

Sulfamethoxazole (SMX) is a widespread and persistent antibiotic pollutant in the aquatic environment. In this paper, SMX was degraded by gamma irradiation, and various influencing factors were explored. The experimental results revealed that after 1.5 kGy irradiation, 20 mg/L SMX could be completely decomposed. Kinetics studies suggested that the radiation-induced degradation process of SMX conformed first-order kinetic. The pH value had influence on the decomposition efficiency through changing the species of reactive radicals and the existing form of SMX molecules and their distribution. Additionally, the effect of inorganic anions (CO32−, HCO3−, NO3−, SO42−, Cl−, HPO42−) and organic matters (peptone, glucose, humic acid) on SMX degradation was evaluated, which had negative influence on SMX degradation. The degradation efficiency of SMX decreased in the effluent water of WWTP in comparison with that in deionized water, suggesting that the components in the effluent inhibited the radiation-induced decomposition of SMX. The mineralization of SMX by ionizing radiation was also evaluated. These results revealed that ionizing radiation is a promising technology to degrade SMX in aqueous solution as well as in wastewater.

Radicals initiated by gamma rays in selected amino acids and collagen

Abstract Calf skin collagen and three amino acids essential for its structure, namely glycine, L-proline and 4-hydroxyl-L-proline, were irradiated with gamma rays up to a dose of 10 kGy. Conversion of radicals over time or after thermal annealing to selected temperatures was monitored by X-band electron paramagnetic resonance (EPR) spectroscopy. Some experimental spectra were compared with signals simulated based on literature data from the electron nuclear double resonance (ENDOR) studies. The following phenomena were confirmed in the tested amino acids: abstraction of hydrogen atom (glycine, proline, hydroxyproline, collagen), deamination (glycine, hydroxyproline), decarboxylation (hydroxyproline). Chain scission at glycine residues, radiation-induced decomposition of side groups and oxidative degradation were observed in irradiated collagen. The decay of radicals in collagen saturated with water occurred at lower temperatures than in macromolecules having only structural water. The paramagnetic centres were the most stable in an oxygen-free atmosphere (vacuum). Radical processes deteriorated the structure of collagen; hence, radiation sterilization of skin grafts requires careful pros and cons analysis.

Formation and interconversion of CCN and CNC radicals resulting from the radiation-induced decomposition of acetonitrile in solid noble gas matrices.

Acetonitrile and the species resulting from its dehydrogenation play an important role in the radiation-induced evolution of organic matter in the space environment. In this work, we report on FTIR spectroscopic studies of the degradation of isolated CH3CN and CD3CN molecules induced by prolonged X-ray irradiation in solid noble gas matrices at 5 K. The principal products observed at high conversion degree of the parent acetonitrile molecules (70-90%) are CCN and CNC radicals, which result from prompt or two-step dehydrogenation of the corresponding precursors, H2CN and CH2NC radicals, respectively. CHCN and CHNC were also found as products of dehydrogenation at high absorbed doses, whereas the fragmentation products (CH3, CN, HCN, and HNC) were detected only in minor amounts over the whole dose range studied. CCN and CNC are produced in nearly equal amounts at high absorbed doses. Selective isomerization of CCN to CNC was observed under the illumination with visible light (460-470 nm), while subsequent action of the UV light (254 nm) induced reverse transformation leading to a photostationary state with the relative population of CNC/CCN being ca. 0.7. The astrochemical implications of the obtained results are discussed in connection with the recent discovery of CCN in extraterrestrial objects.

ANALYTICAL METHOD OF THE FORECAST OF KINETICS OF SURVIVAL OF ONCOLOGICAL PATIENTS AT THE COMBINED RADIATION THERAPY

Analytical method for prediction of the kinetics of survival (KS) and duration of the life expectancy (LE) in patients diagnosed with prostate cancer after combined radiation therapy was developed. It based on medical statistical data of the Federal state budget institution «Russian Research Center of Radiology and Surgical Technologies» (RRCRST) and the mathematical model of the kinetic aging theory of living systems. The quality of life indicators — KS and LE are determined by the solution of the differential equations describing the rate of aging homogeneous groups of patients and taking into account the four main stages of life from birth: «normal» (standard) life before the disease with probability of death for various reasons, life with additional cancer, determining at this stage the likely predominant cause of death from cancer, life is in the process of treatment and after its completion. Each stage of life has its own corresponding parameters of the mathematical model of aging rate, representing the competition of two opposite processes: the accumulation of damages of structural and functional relationships of the organism and their recovery speed. Their rate of destruction with cancer increases. The parameters of the mathematical model are determined by statistical processing of health indicators collected in banks demographic data CDR NES and medical data RRCRST. The main ideology of the developed model based on statistical correlation with survival in the published works of experts of the RRCRST. For patients with prostate cancer is the prostate-specific antigen (PSA) doubling time (PSADT), for patients with breast cancer is the value of S-index (indicator of the degree of radiation-induced DNA decomposition of blood samples in vitro) before treatment of patients. The model is tested on the example of prediction KS and LE in patients of RRCRST treated with radiation therapy that were grouped according to similar values of PSADT and S-index. The ability to improve forecast accuracy by reducing the number of individuals in the group due to the need to have a health and demographic information for each patient and, above all, on the rate of growth of cancer.

Fourier Transform IR Spectroscopic Study of Nano-ZrO2 + Nano-SiO2 + Nano-H2O Systems Upon the Action of Gamma Radiation

The radiation decomposition of water in a nano-ZrO2 + nano-SiO2 + H2O system at 300 K by the action of gamma radiation has been studied by Fourier transform IR spectroscopy. Water adsorption in the zirconium and silicon nanooxides is attributed to molecular and dissociative mechanisms. Active intermediates in this radiation-induced heterogeneous decomposition of water were detected including zirconium and silicon hydrides and hydroxyl groups. Variation in the ratio of ZrO2 and SiO2 nanopowders was shown to lead to change in their radiation catalytic activity compared to initial ZrO2.

Mechanism of the radiation-induced transformations of fluoroform in solid noble gas matrixes

The X-ray induced transformations in the CHF3/Ng systems (Ng=Ne, Ar, Kr or Xe) at 6K were studied by FTIR spectroscopy. The radiation-induced decomposition of CHF3 was found to be rather inefficient in solid xenon with low ionization energy, which suggests primary significance of the positive hole transfer from matrix to the fluoroform molecule. CF3•, :CF2, CHF2• and CF4 were identified as the products of low-temperature radiolysis in all the noble gas matrixes. In addition, the anionic complex HF⋯CF2− was detected in Ne and Ar matrixes. The radiolysis also resulted in formation of noble gas compounds (HArF in argon, HKrF in krypton, and XeF2 in xenon). While XeF2 and HArF were essentially formed directly after irradiation (presumably due to reactions of ’hot’ fluorine atoms), HKrF mainly resulted from annealing of irradiated samples below 20K due to thermally induced mobility of trapped fluorine atoms. In both krypton and xenon matrixes, the thermally induced reactions of F atoms occur at lower temperatures than those of H atoms, while the opposite situation is observed in argon. The mechanisms of the radiation-induced processes and their implications are discussed.

A Reflectron Time-of-Flight Mass Spectrometric Study on the Degradation Pathways of Glycine on Mars in the Presence of Perchlorates and Ionizing Radiation

Abstract The absence of abundant organics on the Martian surface is a much discussed observation. So far, no explanation is completely satisfactory. In this study we aim for a deeper understanding of the degradation processes of organics in the presence of perchlorates that can take place on the Martian surface. Our primary goal is to study the radiation-induced decomposition process of glycine (H2NCH2COOH) in the absence and presence of an oxidizer relevant to the Martian surface—perchlorate anions ( ClO 4 − ) . Glycine and various samples of glycine-1-13C (+H3NC H 2 13 COO−)–magnesium perchlorate hexahydrate (Mg(ClO4)2 · 6H2O) were exposed to energetic electrons mimicking secondary electrons originating from the interaction of galactic cosmic rays (GCRs) with the Martian regolith. Using isotope-labeled and deuterated pure glycine samples such as glycine-1-13C, glycine-d5 (+D3NCD2COO−), glycine-N,N,N-d3 (+D3NCH2COO−), and glycine-2,2-d2 (+H3NCD2COO−), we can conclude that decarboxylation (carbon dioxide loss) of the glycine molecule is exclusively the first decay step during irradiation regardless of whether perchlorate anions are present or not. In pure glycine samples, the decarboxylation co-product methylamine (CH3NH2) and its radiolytic decay product ammonia could both be detected explicitly for the first time. In the presence of perchlorates, (partial) oxidation of the glycine decarboxylation product CH3NH2 may occur. Because the decarboxylation is an equilibrium reaction and the CH3NH2 is effectively removed from the system by this oxidation, glycine cannot be recycled. Therefore the depletion of the CH3NH2 facilitates the process, resulting in an overall 10-fold increase in the formation rate of carbon dioxide and its elevated concentrations in the perchlorate-containing irradiated samples.

Communication: "Position" does matter: The photofragmentation of the nitroimidazole isomers.

A combined experimental and theoretical approach has been used to disentangle the fundamental mechanisms of the fragmentation of the three isomers of nitroimidazole induced by vacuum ultra-violet (VUV) radiation, namely, 4-, 5-, and 2-nitroimidazole. The results of mass spectrometry as well as photoelectron-photoion coincidence spectroscopy display striking differences in the radiation-induced decomposition of the different nitroimidazole radical cations. Based on density functional theory (DFT) calculations, a model is proposed which fully explains such differences, and reveals the subtle fragmentation mechanisms leading to the release of neutral species like NO, CO, and HCN. Such species have a profound impact in biological media and may play a fundamental role in radiosensitising mechanisms during radiotherapy.