Effect Of Soft X-ray Irradiation Research Articles

Photon energy dependence of graphene oxide reduction by soft X-ray irradiation and atomic hydrogen annealing

The effects of soft X-ray irradiation and atomic hydrogen annealing on the reduction of graphene oxide (GO) to obtain graphene were investigated. To clarify the interaction between soft X-rays and GO, soft X-rays of 300 eV and 550 eV were used for C 1s and O 1s inner-shell electron excitation, respectively at the NewSUBARU synchrotron radiation facility. Low-temperature reduction of the GO film was achieved by using soft X-ray at temperatures below 150 °C at 300 eV, and 60 °C at 550 eV. O-related peaks in X-ray photoelectron spectroscopy, such as the C–O–C peak, were smaller at 550 eV than those at 300 eV. This result indicates that excitation of the core–shell electrons of O enhances the reduction of GO. Soft X-rays preferentially break C–C and C–O bonds at 300 and 550 eV, respectively.

Effect of Soft X-ray Irradiation on Film Properties of a Hydrogenated Si-Containing DLC Film.

The effect of soft X-ray irradiation on hydrogenated silicon-containing diamond-like carbon (Si-DLC) films intended for outer space applications was investigated by using synchrotron radiation (SR). We found that the reduction in film thickness was about 60 nm after 1600 mA·h SR exposure, whereas there was little change in their elemental composition. The reduction in volume was attributable to photoetching caused by SR, unlike the desorption of hydrogen in the case of exposure of hydrogenated DLC (H-DLC) film to soft X-rays. The ratio of the sp2 hybridization carbon and sp3 hybridization carbon in the hydrogenated Si-DLC films, sp2/(sp2 + sp3) ratio, increased rapidly from ~0.2 to ~0.5 for SR doses of less than 20 mA·h. SR exposure significantly changed the local structure of carbon atoms near the surface of the hydrogenated Si-DLC film. The rate of volume reduction in the irradiated hydrogenated Si-DLC film was 80 times less than that of the H-DLC film. Doping DLC film with Si thus suppresses the volume reduction caused by exposure to soft X-rays.

In-situ soft X-ray effects on graphene oxide films

ABSTRACTIn the present study, the effects of soft X-ray irradiation on graphene oxide (GO) films are discussed. In particular, by means of the XPS technique, it has been observed that even with a short exposure time GO is sensitive to the soft x-ray radiation. The X-ray radiation effects were investigated evaluating the C/O atomic ratio. Different irradiation times were applied ranging between 12 and 450 min. Significant modifications were detected in the C/O ratio and consequently in the C1s and O1s XPS profiles. At the highest soft X-ray exposure times, we disclosed the transformation of the C–OH groups to the phenol/aromatic diol ones.

Erosion of fluorinated diamond-like carbon films by exposure to soft X-rays

The effects of soft X-ray irradiation on fluorinated diamond-like carbon (F-DLC) films were investigated using synchrotron radiation (SR). The Vickers hardness of the F-DLC films substantially increased from an initial value of about 290 to about 800 HV at a dose of 50 mA·h and the remained constant at about 1100 HV at doses of more than 300 mA·h. This dose dependence was consistent with those of the film thickness and elemental composition. The depth profile of the elemental composition inside each F-DLC film obtained by the measurement of the X-ray photoelectron spectrum (XPS) during sputtering showed that the composition ratio of fluorine was approximately constant from the surface to the neighborhood of the substrate. Namely, fluorine atoms were desorbed by SR irradiation from not only the surface but also the substrate neighborhood. Modification by SR irradiation was found to occur in the entire F-DLC film of about 200 nm thickness.

Study on Schottky Diode Characteristics Improving by X-Ray Irradiation

The effect of soft X-ray irradiation to the Schottky diode properties was analyzed in this paper. The built-in voltage, leakage current, and work function of Schottky diode were investigated. The current-voltage characteristics of the Schottky diode are measured at room temperature. After irradiation at 70 keV for 55 seconds the forward current and leakage current are increase slightly. On the other hand, the built-in voltage is decrease from the initial value about 0.12 V. Consequently, this method can cause the Schottky diode has low power consumption. The results show that soft X-ray can improve the characteristics of Schottky diode.

Low-temperature crystallization of amorphous silicon and amorphous germanium by soft X-ray irradiation

The low-temperature-crystallization effects of soft X-ray irradiation on the structural properties of amorphous Si and amorphous Ge films were investigated. From the differences in crystallization between Si and Ge, it was found that the effects of soft X-ray irradiation on the crystallization strongly depended on the energy band gap and energy level. The crystallization temperatures of the amorphous Si and amorphous Ge films decreased from 953K to 853K and 773K to 663K, respectively. The decrease in crystallization temperature was also related to atoms transitioning into a quasi-nucleic phase in the films. The ratio of electron excitation and migration effects to thermal effects was controlled using the storage-ring current (photon flux density). Therefore, we believe that low-temperature crystallization can be realized by controlling atomic migration through electron excitation.

Effect of the Soft X-rays on Highly Hydrogenated Diamond-Like Carbon Films

The effect of soft X-ray irradiation of diamond-like carbon films in vacuum was investigated using synchrotron radiation (SR). Etching and the desorption of hydrogen upon SR exposure in vacuum occurred in highly hydrogenated diamond-like carbon (H-DLC) films; these processes were not observed in the irradiation of a low-hydrogenated DLC film. The extent of decrease in hydrogen content due to SR exposure was found to decrease with increasing the etching ratio of the H-DLC film. This indicates that hydrogen desorption from the H-DLC films competed with the etching process. Namely, the modified surface, in which hydrogen content was decreased by SR exposure, was immediately removed from the H-DLC film that had a high etching rate.

Comparative Theoretical and Experimental Study of the Radiation-Induced Decomposition of Glycine

The radiation-induced decomposition of glycine is studied using a combination of near-edge X-ray absorption fine structure (NEXAFS) measurements and DFT calculations. The measured spectra show strong dose- or time-dependent effects consistent with a complex, multistep decomposition. Principal component analysis was used to determine the number of distinct molecules that were needed to explain the observed changes in the measured spectra, and the emerging absorption features are assigned to various product molecules through comparison with simulated spectra of several model compounds. It is clear from the experiment that the major effect of soft X-ray irradiation is the fragmentation of the molecule, primarily at the carbonyl sites. Peptide formation is shown to occur under irradiation; a condensation reaction initiated by the removal of a carbonyl oxygen is the proposed mechanism. This study utilizes a novel approach to the study of radiation damage that can occur during measurements and suggests that it may be possible to use simulated model spectra to correct for these effects in measured spectra.

Soft X-ray induced chemical modification of polysaccharides in vascular plant cell walls

Scanning transmission X-ray microscopy and micro carbon X-ray Absorption Near Edge Spectroscopy (C-XANES) can provide quantitative information regarding the distribution of the biopolymers cellulose, hemicellulose, and lignin in vascular plant cell walls. In the case of angiosperms, flowering plants, C-XANES may also be able to distinguish variations in lignin monomer distributions throughout the cell wall. Polysaccharides are susceptible to soft X-ray irradiation induced chemical transformations that may complicate spectral analysis. The stability of a model polysaccharide, cellulose acetate, to variable doses of soft X-rays under conditions optimized for high quality C-XANES spectroscopy was investigated. The primary chemical effect of soft X-ray irradiation on cellulose acetate involves mass loss coincident with de-acetylation. A lesser amount of vinyl ketone formation also occurs. Reduction in irradiation dose via defocusing does enable high quality pristine spectra to be obtained. Radiation induced chemical modification studies of oak cell wall reveals that cellulose and hemicellulose are less labile to chemical modification than cellulose acetate. Strategies for obtaining pristine C-XANES spectra of polysaccharides are presented.

Effect of soft X-ray irradiation on the migratory ability of primordial germ cells in chickens

1. The present study was conducted to elucidate the effect of soft X-ray irradiation on the migratory ability of primordial germ cells (PGCs) to the germinal ridges of chicken embryos. 2. PGCs (Barred Plymouth Rock, BPR) were isolated from embryonic blood and irradiated with soft X-rays for 1–10 min. Then, the PGCs were transfected in vitro with GFP gene by lipofection. The manipulated PGCs were transferred to recipient embryos (White Leghorn, WL) and migration to the germinal ridges was analysed by examining GFP gene expression in the gonads of recipient embryos under UV light at ×40 magnifications. The expression of GFP gene was detected in all the gonads of recipient embryos examined up to 10·5 d of culture. 3. Migration of PGCs irradiated with soft X-rays to the germinal ridges was also confirmed by detecting a single nucleotide polymorphism in the D-loop region of the mitochondrial DNA of BPR and WL chickens. Freshly collected PGCs (BPR) were transferred to the bloodstream of recipient embryos (WL). The fate of the transferred donor PGCs was traced by detecting the single nucleotide polymorphism in the D-loop region of the mitochondrial DNA in BPR and WL used in this study. Transferred donor PGC-derived cells were detected in all the gonads of 17-d cultured embryos by PCR. 4. The results suggest that PGCs irradiated with soft X-rays still retain the ability to migrate to the germinal ridges of recipient embryos.

Effects of Soft X-Ray Irradiation to Stage X Blastoderm on Restriction of Proliferation of Primordial Germ Cells in Early Chicken Embryos

It is necessary to deplete the endogenous primordial germ cells (PGCs) from recipient embryos when germline chimaeric chickens are produced by the transfer of PGCs. In this study, effects of soft X-ray irradiation on the restriction of PGC proliferation were examined to obtain recipient embryos with as many depleted PGCs as possible. The stage X blastoderm was irradiated with soft X-rays (15 kVP, 5mA, 0.083nm, 16 cm distance) for 20-180 seconds (0.27-2.4Gy), and concentrations of PGCs in the bloodstream of embryos at stages 13-16 were analysed. The viabilities of embryos irradiated with soft X-rays for 20-90 seconds was not significantly different from those in the control, but were markedly reduced when embryos were irradiated with soft X-rays for 120-180 seconds. The concentration of PGCs in the bloodstream of embryos was reduced by increasing the irradiation time of soft X-rays. In particular, the concentration of PGCs at stages 14-15 started to decrease rapidly when irradiated with soft X-rays for more than 90 seconds. Administration of busulfan in the stage X blastoderm showed a similar effect to soft X-ray irradiation on the concentration of PGCs in the bloodstream of embryos. Our results suggest that a 90-second irradiation of soft X-rays to the stage X blastoderm is recommended for reducing the concentration of PGCs in chicken embryos without affecting their viability.

Lens formation in the absence of optic cup in rat embryos irradiated with soft X-ray.

In order to investigate the effect of soft X-ray irradiation on ocular development, pregnant rats were exposed to a single 12.5 Gy irradiation on embryonic day 9 (ED 9). The embryos obtained by laparotomy on ED 12 and 21 were examined for ocular abnormalities under a binocular stereo-microscope and a light microscope. The ED 12 embryos were stained with osmium tetroxide to facilitate the observation. The stereo-microscopic examination on ED 12 and 21 revealed various types of ocular abnormalities characterized primarily by aplasia or hypoplasia of the optic cup and invaginated lens placode. The light microscopic examination further confirmed these findings histomorphologically, and the hypoplastic abnormalities were classified into three types: (1) hypoplasia of the optic cup and invaginated lens placode, (2) complete malformation of the optic cup and hypoplasia of the invaginated lens placode, and (3) complete malformation of the optic cup and invaginated lens placode. Because the lens was formed in the complete absence of the retina, the development and differentiation of the retina and lens do not seem to be tightly synchronized. Thus, this sequential analysis on ocular abnormalities during the early stage of development supports the notion that the presence of the retina is not always necessary for the development of the lens.

Characterization of the effects of soft X-ray irradiation on polymers

The physical and chemical effects of the soft X-ray irradiation of polymers have been systematically evaluated for photon energies just above the C 1s binding energy. This exposure causes radiation damage in the form of the loss of mass and changes to the chemical structure of the polymers. These effects are evident in the Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra of the exposed polymers, posing a fundamental limit to the sensitivity of NEXAFS spectroscopy for chemical microanalysis. Quantitative understanding of the chemistry and kinetics of radiation damage in polymers is necessary for the successful and validated application of NEXAFS microscopy. This paper outlines a method for quantifying this radiation damage as a function of X-ray dose, and applies these methods to characterize the loss of mass and loss of carbonyl group functionality from a diverse series of polymers. A series of simple correlations are proposed to rationalize the observed radiation damage propensities on the basis of the polymer chemical structure. In addition, NEXAFS spectra of irradiated and virgin polymers are used to provide a first-order identification of the radiation chemistry.

Evaporation and Expansion of Poly-tetra-fluoro-ethylene Induced by Irradiation of Soft X-Rays from a Figure-8 Undulator

The effects of soft X-ray irradiation of poly-tetra-fluoro-ethylene (PTFE) have been investigated using a figure-8 undulator. In the case of high-intensity irradiation, the surface temperature of the irradiated region increased and PTFE near the surface was evaporated effectively. In contrast, the PTFE surface swelled by the under low-intensity irradiation with the insertion of Al filters more than 9 µm thick. This reaction was found to be strongly dependent on the flux. The surface profile is largely determined by the relationship between fragment desorption and porous structure generation, and an increase in the surface temperature enhances the fragment desorption and has considerable influence on the surface profile. Al filter insertion decreases the flux and suppresses low-energy photons which are absorbed near the surface. Hence irradiated photons are composed of high-energy photons which penetrate deeply, and the surface temperature is difficult to increase by Al-filter-inserted irradiation.

Effects of soft X-ray irradiation on NK cell activity and the percentage of asialo GM1-positive cells in spleen cells of mice.

Effects of soft X-ray irradiation on the natural killer (NK) cell activity and the percentage of asialo GM1-positive cells of spleen cells in mice were investigated by using a soft X-ray generator intended for non-destructive radiological examination. Soft X-ray irradiation in graded doses of more than 25.8 mC/kg indicated dose dependent reductions in the NK cell activity in the spleen of irradiated mice. Significant reductions in the population of asialo GM1-positive cells in spleen cells were also observed. These results suggest that a soft X-ray generator could also be useful in immuno-irradiation studies.

Effect of soft x-ray irradiation on immunological functions in mice.

Effect of soft x-ray irradiation on immunological functions in mice was investigated. Soft x-ray irradiation with 100R or more induced a significant reduction in the number of plaque-forming cells (PFC). The reduction in the number of PFC depended on the irradiation doses. Irradiation with 600R or more showed a significant reduction in the delayed reaction of footpad swelling. However, soft x-ray irradiation with doses ranging from 100R to 1000R did not exert significant influence on the K values of carbon clearance test. Irradiation with 100R or more of soft x-ray showed a remarkable reduction of response to concanavalinA (ConA) or lipopolysaccharide (LPS) in spleen cells, and the response to ConA was lower than that to LPS. These results suggest that in the soft x-ray-irradiated mice, antibody-producing ability, delayed type hypersensitivity reaction and mitogenic activity are sensitive to soft x-ray irradiation and furthermore, T cell is more sensitive than B cell, but phagocytic activity of reticulo-endothelial system (RES) is resistant to soft x-ray irradiation.

Effects of soft X-ray irradiation on solid-state imagers

The visible effects of soft X-ray damage in solid-state imagers are changes in the flat-band voltages, degradation in charge transfer efficiency and increased dark current. Details of these effects, and possible underlying mechanisms, are discussed. Deep level transient spectroscopy is introduced as a useful tool for identifying existing and radiation-induced trapping centres in charge-coupled devices. The effects of various annealing methods for charge-coupled and photodiode imagers are presented.

Inhibitory effect of soft X-ray irradiation on growth of syngeneic tumor in mice.

Effect of soft x-ray irradiations through a 10 mm-thick acrylfilter on a syngeneic MC-1 tumor in C57BL/6 mice was investigated. The irradiations with 1000 and 2000 R produced a significant inhibitory effect on tumor growth. Although the irradiation with 300 and 600 R did not produce a significant effect on the tumor size and survival days, histological inspection showed appreciable inhibition of the tumor growth by these low doses.

Effect of soft X-ray irradiation on antibody production in mice.

C3H/He, C57BL/6マウスについて, SRBCに対するIgM・PFCを指標として軟X線全身照射の抗体産生能への影響をしらべた. 抗体産生は照射により明らかに抑制され, 抑制の程度は照射線量に比例したが, C3H/He, C57BL/6間には軟X線照射の影響について差があることがわかつた.

The Effect of Soft X-ray Irradiation on Bacteriophages

The Effect of Soft X-ray Irradiation on Bacteriophages