Γ-ray Radiolysis Research Articles

γ-Ray radiolysis of dihydroxyurea in water and its radiolytic by-products

γ-Ray radiolysis of dihydroxyurea in water and its radiolytic by-products

γ-ray radiolysis of dihydroxyurea in nitric acid and its radiolytic products

γ-ray radiolysis of dihydroxyurea in nitric acid and its radiolytic products

H2 production from the radiolysis of aqueous suspensions of ZnO nanoparticles by 5.5 MeV He2+ ions

The effects of ion beam irradiation on aqueous suspensions of metal oxides has received relatively little attention compared to γ-ray irradiation despite being a highly prevalent process in spent nuclear fuel storage and reprocessing. This is partly due to the difficulties associated with homogeneously irradiating condensed-phase matter using α-particles. Here, we report experimental yields of H2 from the 5.5 MeV He2+ ion irradiation of aqueous suspensions of ZnO nanoparticles. The obtained results are compared to our previously measured results for the γ-radiolysis of the same system. The amount of H2 increases linearly with adsorbed dose for all studied concentrations. The measured yields are of the same order of magnitude as those observed for pure water, but decrease with increasing water content. Overall, the yields follow a similar trend to those observed for γ-ray radiolysis.

TOPAS-nBio validation for simulating water radiolysis and DNA damage under low-LET irradiation

The chemical stage of the Monte Carlo track-structure simulation code Geant4-DNA has been revised and validated. The root-mean-square (RMS) empirical parameter that dictates the displacement of water molecules after an ionization and excitation event in Geant4-DNA has been shortened to better fit experimental data. The pre-defined dissociation channels and branching ratios were not modified, but the reaction rate coefficients for simulating the chemical stage of water radiolysis were updated. The evaluation of Geant4-DNA was accomplished with TOPAS-nBio. For that, we compared predicted time-dependent G values in pure liquid water for ·OH, e– aq, and H2 with published experimental data. For H2O2 and H·, simulation of added scavengers at different concentrations resulted in better agreement with measurements. In addition, DNA geometry information was integrated with chemistry simulation in TOPAS-nBio to realize reactions between radiolytic chemical species and DNA. This was used in the estimation of the yield of single-strand breaks (SSB) induced by 137Cs γ-ray radiolysis of supercoiled pUC18 plasmids dissolved in aerated solutions containing DMSO. The efficiency of SSB induction by reaction between radiolytic species and DNA used in the simulation was chosen to provide the best agreement with published measurements. An RMS displacement of 1.24 nm provided agreement with measured data within experimental uncertainties for time-dependent G values and under the presence of scavengers. SSB efficiencies of 24% and 0.5% for ·OH and H·, respectively, led to an overall agreement of TOPAS-nBio results within experimental uncertainties. The efficiencies obtained agreed with values obtained with published non-homogeneous kinetic model and step-by-step Monte Carlo simulations but disagreed by 12% with published direct measurements. Improvement of the spatial resolution of the DNA damage model might mitigate such disagreement. In conclusion, with these improvements, Geant4-DNA/TOPAS-nBio provides a fast, accurate, and user-friendly tool for simulating DNA damage under low linear energy transfer irradiation.

Effect of monomethylhydrazine on γ-ray radiolysis and radiolytic by-products of DMHA in nitric acid

N,N-dimethylhydroxylamine (DMHA) is an effective novel salt-free reductant used in spent fuel reprocessing. This paper reports the effect of monomethylhydrazine (MMH) on γ-ray radiolysis and radiolytic by-products of DMHA in HNO3. The presence of MMH improves the stability of DMHA against radiation significantly, the main radiolytic by-products are N-methylhydroxylamine, HCHO, HCOOH and HNO2, which concentration increases with the dose. The concentration of N-methylhydroxylamine increases with the MMH concentration, but that of HCHO, HCOOH and HNO2 decreases with increasing MMH concentration. These results will provide considerable reference for the application of DMHA in the PUREX process.

Pd-functionalized core-shell composite nanowires for self-heating, sensitive, and benzene-selective gas sensors

We devised a new low power consumption nanocomposite sensor based on Pd-functionalized SnO2-ZnO core-shell nanowires (C-S NWs) in self-heating mode. Functionalization of Pd nanoparticles (NPs) was performed by γ-ray radiolysis at room temperature. Characterization results confirmed formation of the C-S NW morphology with the desired composition. The effects of various applied voltages (1−20 V) and different gases upon the sensing response of synthesized NWs was examined. In particular, increasing the applied voltage increased the gas sensitivity, where the response for 50 ppm C6H6 was 1.19 at 3 V, and it increased to 2.62 at 20 V through the generation of heat within the sensor via self-heating. Additionally, the sensors revealed outstanding selectivity towards C6H6. The effects of sensing temperatures (RT-200 °C) without applied voltages were also studied. The high response to C6H6 along with the excellent selectivity was due to the unique design of the sensor and the catalytic activity of Pd towards C6H6. The sensor in self-heating mode consumed only 70.5 nW at 5 V, indicating a good potential to be integrated in portable, low power consumption electronic devices.

Photocatalytic degradation of ethylene by TiO2 nanotubes/ reduced graphene oxide prepared by gamma irradiation

A nanocomposite photocatalyst of TiO2 nanotubes/reduced graphene oxide (rGO-TNTAs) were prepared by γ-ray radiolysis. The rGO-TNTAs were studied for photocatalytic decomposition of ethylene (C2H4) in a refrigerated environment. Degradation efficiency of ethylene by these materials was described by the apparent first-order rate constant (K). The composite was characterized by Raman spectroscopy (RS), X-ray photoelectron spectroscopy (XPS), Atomic force microscopy (AFM) and Field emission electron microscopy (FESEM). The preparing parameters for materials affecting the degradation efficiency in terms of the rate constant were studied, including the GO addition and the irradiation dose. The results showed that (1) gamma irradiation can induce GO to partial rGO, the rGO surface of rGO-TNTAs was smooth and loosely lamellar structure. (2) The K of the rGO-TNTAs is highly dependent on the GO addition and the irradiation dose. With a GO addition of 0.1 g and an irradiation dose of 20 kGy, the maximum K value of rGO-TNTAs could be obtained under the experimental conditions. (3) From analysis of the Raman spectroscopy spectrum, optimum changes had occurred in the intensity ratio of D-band to G-band of the GO that had been γ-ray-irradiated with a dose of 20 kGy, resulting in the K of rGO-TNTAs increased by 40.9% compared with that of TNTAs.

Photocatalytic degradation of ethylene by TiO2 nanotubes/ reduced graphene oxide prepared by gamma irradiation

A nanocomposite photocatalyst of TiO2 nanotubes/reduced graphene oxide (rGO-TNTAs) were prepared by γ-ray radiolysis. The rGO-TNTAs were studied for photocatalytic decomposition of ethylene (C2H4) in a refrigerated environment. Degradation efficiency of ethylene by these materials was described by the apparent first-order rate constant (K). The composite was characterized by Raman spectroscopy (RS), X-ray photoelectron spectroscopy (XPS), Atomic force microscopy (AFM) and Field emission electron microscopy (FESEM). The preparing parameters for materials affecting the degradation efficiency in terms of the rate constant were studied, including the GO addition and the irradiation dose. The results showed that (1) gamma irradiation can induce GO to partial rGO, the rGO surface of rGO-TNTAs was smooth and loosely lamellar structure. (2) The K of the rGO-TNTAs is highly dependent on the GO addition and the irradiation dose. With a GO addition of 0.1 g and an irradiation dose of 20 kGy, the maximum K value of rGO-TNTAs could be obtained under the experimental conditions. (3) From analysis of the Raman spectroscopy spectrum, optimum changes had occurred in the intensity ratio of D-band to G-band of the GO that had been γ-ray-irradiated with a dose of 20 kGy, resulting in the K of rGO-TNTAs increased by 40.9% compared with that of TNTAs.

Effect of nitrous acid on γ-ray radiolysis and radiolytic products of N, N-dimethylhydroxylamine

N, N-dimethylhydroxylamine (DMHA) is a new salt-free reductant used in spent fuel reprocessing, this paper reports the effect of HNO2 on γ-ray radiolysis and radiolytic products of DMHA in nitric acid medium. DMHA concentration in irradiated samples decreases with the increasing dose and initial HNO2 concentration, and the radiolytic rate of DMHA is lower than 21% at 10 kGy supposed to be the maximum dose absorbed by the reagent during the U/Pu separation and the Pu purification. The main radiolytic products are H2, CH3NHOH, HCHO, and HCOOH, and their quantity increases with the dose and initial HNO2 concentration.

Donor–Donor′–Acceptor Triads Based on [3.3]Paracyclophane with a 1,4‐Dithiafulvene Donor and a Cyanomethylene Acceptor: Synthesis, Structure, and Electrochemical and Photophysical Properties

Donor-donor'-acceptor triads (1, 2), based on [3.3]paracyclophane ([3.3]PCP) as a bridge, with electron-donating properties (D') using 1,4-dithiafulvene (DTF; TTF half unit) as a donor and dicyanomethylene (DCM; TCNE half unit) or an ethoxycarbonyl-cyanomethylene (ECM) as an acceptor were designed and synthesized. The pulse radiolysis study of 1 a in 1,2-dichloroethane allowed the clear assignment of the absorption bands of the DTF radical cation (1 a.+ ), whereas the absorption bands due to the DCM radical anion could not be observed by γ-ray radiolysis in 2-methyltetrahydrofuran rigid glass at 77 K. Electrochemical oxidation of 1 a first generates the DTF radical cation (1 a.+ ), the absorption bands of which are in agreement with those observed by a pulse radiolysis study, followed by dication (1 a2+ ). The ESR spectrum of 1 a.+ showed a symmetrical signal with fine structure and an ESR simulation predicted that the spin of 1 a.+ is delocalized over S and C atoms of the DTF moiety and the central C atom of the trimethylene bridge bearing the DTF moiety. Pulse radiolysis, ESR, and electrochemical studies indicate that the DTF radical cation of 1 a.+ is more stable than that of 6.+ , and the latter shows a strong tendency to dimerize. This result indicates that the [3.3]PCP moiety as a bridge can stabilize the DTF radical cation more than the 1,3-diphenylpropane moiety because of kinetic stability due to its rigid structure and the weak electronic interaction of DTF and DCM moieties through [3.3]PCP.

γ-Ray radiolysis of acetohydroxamic acid in HNO3 and its radiolytic product

Acetohydroxamic acid (AHA) is a novel salt-free reagent used for the separation of Pu and Np from U in the advanced Purex process. This paper reports the γ-ray damage of AHA in HNO3 and its radiolytic product. For 0.2 mol L−1 AHA in 0.2–2.0 mol L−1 HNO3 irradiated at a dose of 5–25 kGy, the radiolytic rate of AHA is 6.63–77.5%, and it increases with the HNO3 concentration and absorbed dose. The main radiolytic gases are N2O and H2, with volume fractions of (0.500–16.2) × 10−2 and (1.30–11.8) × 10−3, respectively, and they increase with the absorbed dose; the H2 volume fraction decreases with increasing HNO3 concentration. The main liquid radiolytic products are CH3COOH and HNO2, and their concentrations are (3.40–19.7) × 10−2 and (0.200–4.80) × 10−3 mol L−1, respectively, which increase with the HNO3 concentration. Since a significant concentration of HNO2 is present in the irradiated AHA-HNO3 solution, a holding reductant must be used to destroy HNO2 and stabilize Pu(III) and Np(V) when AHA is applied for the separation of Pu and Np from U.

Radical Ions of a π-Bowl Sumanene: Effects of Strained Structure on the Electronic Transitions.

Strained polyaromatic carbon molecules exhibit interesting properties owing to enhanced interactions between p orbitals of sp2 carbons; sumanene (SUM) is one of these bowl-shaped π-conjugated molecules (π-bowls). In the present study, the radical cation and radical anion of SUM were characterized by radiation chemical methods, that is, pulse radiolysis and γ-ray radiolysis. Absorption spectra of the SUM radical cation and radical anion in a wide spectral region ranging from the visible to near-IR were successfully obtained. Absorption spectra of the SUM radical cation and radical anion are similar in shape to those of the corresponding species of triphenylene (TP), which possesses a planar structure and the same π-electron system as SUM. However, the SUM radical anion showed lower peak shifts than the TP radical anion. Theoretical calculations revealed that the MOs responsible for the electronic transitions of the SUM radical anion are different from those of the TP radical anion, in contrast to the radical cations. These results demonstrate that the strains in the molecular geometries affect the electronic transitions of radical ions.

Extremely sensitive and selective sub-ppm CO detection by the synergistic effect of Au nanoparticles and core–shell nanowires

An extremely sensitive CO sensor based on novel hybrid SnO2–ZnO core–shell (C–S) nanowires (NWs) functionalized by Au nanoparticles (NPs) was synthesized. First, networked SnO2 NWs were successfully prepared using the vapor–liquid–solid growth method on an electrode layer with special patterns. A ZnO shell was subsequently coated on the SnO2 core using atomic layer deposition, and Au NPs were then attached onto the ZnO shell using γ-ray radiolysis. The resulting sensor exhibited a very high response of 26.6–100ppb CO gas. Furthermore, the responses to other gases such as C6H6 and C6H7 were extremely low, indicating the very good selectivity of the sensor to CO gas. Besides acting as heterojunctions, the catalytic effect of the Au NPs on CO gas greatly improved the CO sensing capability of the Au-functionalized SnO2–ZnO C–S NWs. The high sensitivity and selectivity of this sensor can open a path for prompt toxic monitoring and early detection of fatal diseases related to CO.

Radiolysis of water with aluminum oxide surfaces

Aluminum oxide, Al2O3, nanoparticles with water were irradiated with γ-rays and 5MeV He ions followed by the determination of the production of molecular hydrogen, H2, and characterization of changes in the particle surface. Surface analysis techniques included: diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), nitrogen absorption with the Brunauer – Emmett – Teller (BET) methodology for surface area determination, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Production of H2 by γ-ray radiolysis was determined for samples with adsorbed water and for Al2O3 – water slurries. For Al2O3 samples with adsorbed water, the radiation chemical yield of H2 was measured as 80±20 molecules/100eV (1 molecule/100eV=1.04×10−7mol/J). The yield of H2 was observed to decrease as the amount of water present in the Al2O3 – water slurries increased. Surface studies indicated that the α-phase Al2O3 samples changed phase following irradiation by He ions, and that the oxyhydroxide layer, present on the pristine sample, is removed by γ-ray and He ion irradiation.

Photocatalytic degradation of ethylene using titanium dioxide nanotube arrays with Ag and reduced graphene oxide irradiated by γ-ray radiolysis

Titanium dioxide nanotube arrays (*TNTAs) made by anodic oxidation method and irradiated under 60Co-γ radiation combining with silver nanoparticles (AgNPs) and reduced graphene oxide (rGO) irradiated by 60Co-γ rays as well were investigated for photocatalytic degradation of ethylene in cold storage environment. Rate constant K of degradation was selected to describe the decomposition efficiency of ethylene with the new photocatalytic composite material (AgNPs/rGO-*TNTAs). Microstructure of the materials as prepared were characterized using analytic techniques: Atomic Force Microscope (AFM), Raman Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscope (FESEM), Transmission Electron Microscope (TEM), X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). We also compared the performance of five photocatalysts (Thermal annealing TNTAs, *TNTAs, rGO-*TNTAs, AgNPs-*TNTAs, AgNPs/rGO-*TNTAs) concerning ethylene decomposition. Results showed that AgNPs/rGO-*TNTAs exhibited enhancement of photocatalytic degradation of ethylene compared with rGO-*TNTAs and AgNPs-*TNTAs in photocatalytic process. Photocatalytic activity and structural evolution of photocatalysts irradiated by gamma rays and impact of the photocatalysts properties responsible for enhancing photocatalytic activity were discussed.

Realization of ppb-Scale Toluene-Sensing Abilities with Pt-Functionalized SnO2-ZnO Core-Shell Nanowires.

In this paper, we report the exceptional toluene-sensing properties of SnO2-ZnO core-shell nanowires (C-S NWs) functionalized with Pt nanoparticles (NPs). A response of 279 was obtained for 100 ppb of toluene, and to the best of our knowledge, this is the highest toluene response to be reported in the literature. The SnO2-ZnO C-S NWs were synthesized via a two-step process: First, a networked core of SnO2 nanowires was prepared via vapor-liquid-solid growth on the patterned electrode layer. Second, the ZnO shell layers were created with atomic layer deposition. The electron-depleted region of the shell layer was further expanded by attaching Pt NPs, which were synthesized using γ-ray radiolysis, to the shell layer. In addition to the expansion of the electron-depleted region, the catalytic effect of Pt on toluene greatly improved the toluene-sensing performance of the C-S NWs. The extraordinary toluene-sensing ability of the Pt-functionalized C-S NWs means they have great potential as the sensing platform in exhaled breath sensors to detect ppb-scale toluene.

Radiolysis of di-2-ethylhexyl hydrogen phosphate and its toluene solutions

The products of radiolytic decomposition of a 25% solution of di-2-ethylhexyl hydrogen phosphate in toluene and of the separate solution components in the dose range 0.10–5.00 MGy were studied by viscometry, pH-metry, and electronic spectrophotometry. The γ-ray radiolysis of this solution occurs via decomposition of the ester molecules by the free radical mechanism to form mono-2-ethylhexyl dihydrogen phosphate C8H17OP(O)(OH)2 (via cleavage of the C-O bond), orthophosphoric acid, and polymeric products. The kinetic scheme of the process is presented. Irradiation with doses of up to 0.80 MGy leads to the HDEHP dealkylation with the formation of C8H17OP(O)(OH)2 with the radiation-chemical yield G = 0.1 molecule/100 eV. At higher doses (2.50–5.00 MGy), orthophosphoric acid is formed with a yield G = 0.01 molecule/100 eV. In the dose range 0.80–5.00 MGy, the radiolytic decomposition of di-2-ethylhexyl hydrogen phosphate yields polymeric products, which is associated with insufficient radiation resistance of toluene and with the loss of its protective properties at high absorbed doses. The limiting absorbed dose at which the extractant is efficiently protected by toluene was estimated at 0.8 MGy. Aromatic additives (biphenyl, naphthalene, anthracene, etc.) are suggested for enhancing the extracting solvent performance. These additives are capable of scavenging charges of both signs; in addition, they exhibit higher radiation resistance compared to toluene. In their presence, it is possible to suppress the formation of both acidic esters and polymeric products in the extracting solvent.

Radical Ions of Cyclopyrenylene: Comparison of Spectral Properties with Cycloparaphenylene

Hoop-shaped π-conjugated molecules have attracted much attention. In this study, the radical ions of [4]cyclo-2,7-pyrenylene ([4]CPY), a cyclic tetramer of pyrene, and [4]cyclo-4,5,9,10-tetrahydro-2,7-pyrenylene ([4]CHPY) were investigated using radiation chemical methods, namely, γ-ray radiolysis and pulse radiolysis. The absorption spectra of the radical ions of [4]CPY and [4]CHPY showed clear peaks in the near-IR and UV-vis regions similar to those of [8]cycloparaphenylene ([8]CPP). Theoretical calculations using time-dependent density functional theory provided reasonable assignments of the observed absorption bands. It was indicated that the C4-C5 and C9-C10 ethylene bonds of [4]CHPY do not contribute to the electronic transitions, resulting in absorption spectra similar to those of [8]CPP. On the other hand, it was confirmed that the allowed electronic transitions of the radical ions of [4]CPY are different from those of the radical ions of [4]CHPY and [8]CPP.

Low Temperature Sensing Properties of Pt Nanoparticle-Functionalized Networked ZnO Nanowires.

Networked ZnO nanowires were fabricated via a vapor-phase selective growth method. Pt nanoparticles were functionalized on the networked ZnO nanowires. In this study, for the functioanlization, γ-ray radiolysis was applied. By the method, Pt nanoparticles of - 10 nm in diameter were uniformly anchored on the surface of each ZnO nanowire. The sensing properties of the Pt-functionalized, networked ZnO nanowires were investigated in terms of NO2, CO and benzene at 100 degrees C. The sensing capability of the Pt-functionalized ZnO nanowires at that temperature supports their potential use in chemical gas sensors.

Enhancement of the photoelectrocatalytic activity of TiO2/ACF for ethylene removal by Ag nanoparticles synthesized by γ-ray radiolysis

Silver nanoparticles (AgNPs), obtained by reduction from AgNO3 solution and stabilized in polyvinyl pyrrolidone (PVP), have been synthesized by γ-ray radiolysis. The application of photoelectrocatalytic (PEC) oxidation in ethylene gas treatment using a TiO2 photocatalyst combined with as-prepared AgNPs on activated carbon fiber (ACF) ([Ag+TiO2]/ACF) as a photoelectrode in a Nafion-based photoelectrocatalytic cell is presented. The effects on the PEC degradation of C2H4 of the preparation parameters of the AgNPs, such as the radiation dose and the amount of PVP added, have been systematically investigated. Emphasis is placed on comparison of the C2H4 decomposition rate constant with [Ag+TiO2/ACF] as a photoelectrode in a photoelectrocatalytic cell with that achieved with [TiO2/ACF]. The factors responsible for the enhancing effect of AgNPs on the PEC activity of the [Ag+TiO2/ACF] photoelectrode are discussed.