Effects of electron beam irradiation on the photoelectrochemical properties of TiO2 film for DSSCs

TiO₂ has been widely utilized for various industrial applications such as photochemical cells, photocatalysts, and electrochromic devices. The crystallinity and morphology of TiO₂ films play a significant role in determining the overall efficiency of dye-sensitized solar cells (DSSCs). In this study, the preparation of nanostructured TiO₂ films by electron beam irradiation and their characterization were investigated for the application of DSSCs. TiO₂ films were exposed to 20–100 kGy of electron beam irradiation using 1.14 MeV energy acceleration with a 7.46 mA beam current and 10 kGy/pass dose rates. These samples were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and X-ray photoelectron spectroscopy (XPS) analysis. After irradiation, each TiO₂ film was tested as a DSSC. At low doses of electron beam irradiation (20 kGy), the energy conversion efficiency of the film was approximately 4.0% under illumination of simulated sunlight with AM 1.5 G (100 mW/cm²). We found that electron beam irradiation resulted in surface modification of the TiO₂ films, which could explain the observed increase in the conversion efficiency in irradiated versus non-irradiated films.     

Large-scale synthesis of silver nanoparticles using Ag(I)–S12 polymer through electron beam irradiation

Size-controlled large scale synthesis of silver nanoparticles was performed using Ag(I)–S12 inorganic-organic hybrid polymer with supramolecular structures though electron beam irradiation. The Ag(I)–S12 polymer was simply prepared by mixing dodecanethiol with the solution of silver salts. The silver nanoparticles with various sizes were prepared from Ag(I)–S12 polymer with an electron beam voltage from 0.3 MeV to 2 MeV, current from 0.06 mA to 0.48 mA, and/or irradiation time from 1 to 10 min. The morphology and chemical composition of the irradiated samples were characterized by transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR).     

Effect of electron beam radiation dose on the foam formation in pre-ceramic polymer

Methylsilicone resin as a polymer precursor for a SiOC ceramic material was cured and foamed by electron beam (EB) irradiation in air prior to the pyrolysis under an inert atmosphere. Methylsilicone foams were obtained without additional foaming agent when exposed to accelerated electrons with radiation doses up to 9 MGy and dose rate of 2.8 kGy/s. During irradiation the polymer was melted and simultaneously gaseous products were formed by the methyl group oxidation and by the poly-condensation crosslinking reactions. The formed gases could not escape from the molten polymer and began to aggregate into bubbles. The effect of the radiation dose on the polymer foam molecular structure, the gel fraction and the ceramic yield was analyzed. The results indicate that the maximum amount of crosslinking in methylsilicone, when EB radiation is used, occurred between 1.0 and 2.0 MGy radiation dose. Methylsilicone foams were pyrolysed in N₂ atmosphere at temperatures of 1200 and 1500 °C, resulting in amorphous SiOC and partially crystalline ceramic foams, respectively. A porosity of ~84% was achieved in the pyrolyzed foams, with cell size ranging from 30 to 300 μm and density of about 0.31 g cm^?3.     

Reinforcement of natural rubber/high density polyethylene blends with electron beam irradiated liquid natural rubber-coated rice husk

Coating of rice husk (RH) surface with liquid natural rubber (LNR) and exposure to electron beam irradiation in air were studied. FTIR analysis on the LNR-coated RH (RHR) exposed to electron beam (EB) showed a decrease in the double bonds and an increase in hydroxyl and hydrogen bonded carbonyl groups arising from the chemical interaction between the active groups on RH surface with LNR. The scanning electron micrograph showed that the LNR formed a coating on the RH particles which transformed to a fine and clear fibrous layer at 20 kGy irradiation. The LNR film appeared as patches at 50 kGy irradiation due to degradation of rubber. Composites of natural rubber (NR)/high density polyethylene (HDPE)/RHR showed an optimum at 20–30 kGy dosage with the maximum stress, tensile modulus and impact strength of 6.5, 79 and 13.2 kJ/m², respectively. The interfacial interaction between the modified RH and TPNR matrix had improved on exposure of RHR to e-beam at 20–30 kGy dosage.     

Demonstration of a novel,flexible, photocatalytic oxygen-scavenging polymer film

The preparation of a novel, flexible, photocatalytic, oxygen-scavenging polymer film is described. The film incorporates nanocrystalline titania particles in an ethyl cellulose polymer film, with or without an added sacrificial electron donor of triethanolamine. When coated on the inside of a glass vessel its UV-driven light-scavenging action is demonstrated by platinum octaethyl porphyrin coated glass beads sealed inside, since their luminescence increases with increasing UV-irradiation time. When used as a flexible film, work with an oxygen electrode shows that the film is able to scavenge oxygen at an average rate of 0.017 cm³ O₂ h⁻¹ cm⁻² over a 24 h period, which compares favourably to other, well-established oxygen-scavenger systems. The potential of using such as system for oxygen scavenging in packaging is discussed briefly.     

Target thickness dependence of bremsstrahlung from solid films

We report initial results of a study of the target thickness dependence of bremsstrahlung from solid film targets. The electron beam energy is 50 keV and bremsstrahlung is observed at 90°. Targets are aluminium and gold. Target thicknesses from 50 μg/cm², where single interaction conditions apply, to twice the electron range, where a multiple interaction model applies, were studied. We observe the transition from thin to thick film spectra. The purpose is to investigate whether the polarization bremsstrahlung contribution may be suppressed in solid film targets.     

Evolution of microstructure and crack pattern in NiO thin films under 200 MeV Au ion irradiation

NiO thin films grown on Si (100) substrate by electron beam evaporation method and sintered at 700 °C were irradiated with 200 MeV Au¹⁵⁺ ions. The fcc structure of the sintered films was retained up to the highest fluence (1×10¹³ ions cm^?2) of irradiation. However the microstructure of the pristine film underwent a considerable modification with increasing ion fluence. 200 MeV Au ion irradiation led to compressive stress generation in NiO medium. The diameter of the stressed region created by 200 MeV Au ions along the ion path was estimated from the variation of stress with ion fluence and found to be ～11.6 nm. The film surface started cracking when irradiated at and above the fluence of 3×10¹² ions cm^?2. Ratio of the fractal dimension of the cracked surface obtained at 200 MeV and 120 MeV (Mallick et al., 2010a) Au ions was compared with the ratio of the radii of ion tracks calculated based on Coulomb explosion and thermal spike models. This comparison indicated applicability of thermal spike model for crack formation.     

Modification of microstructure of the surface and the bulk in ion-irradiated membrane studied using positron annihilation spectroscopy

The effect of ion irradiation and etching on the microstructure of polyethyleneterephthalate (PET) membrane has been studied using positron annihilation spectroscopy. PET membrane of 25 μm thickness was irradiated by 100 MeV ³⁵Cl beam (7×10⁷ ions/cm²) and then etched with NaOH for 45 min. The modification in the microstructure at the surface of the membrane was probed by depth-dependent Doppler-broadened S-parameter and positronium 3γ–2γ annihilation ratio using a slow positron beam, while the free volume properties in the bulk of the membrane were studied using the conventional positron lifetime technique. Positron annihilation parameters were found to be very sensitive to the microstructural changes occurring in the polymer at such a low fluence. It was observed that on ion-irradiation, the surface of the membrane is modified in a different way than the bulk. While the ion-irradiation produces large fraction of excess free volumes at the surface of the membrane due to chain scission, the free volumes are reduced in the bulk of the membrane due to cross-linking. FTIR and XRD measurements were also carried out to investigate the changes occurring in the chemical structure and crystallinity of the polymer samples on ion-irradiation and etching.     

Characterization of a power bipolar transistor as high-dose dosimeter for 1.9–2.2 MeV electron beams

Results of the characterization studies on a power bipolar transistor investigated as a possible radiation dosimeter under laboratory condition using electron beams of energies from 2.2 to 8.6 MeV and gamma rays from a ⁶⁰Co source and tested in industrial irradiation plants having high-activity ⁶⁰Co γ-source and high-energy, high-power electron beam have previously been reported. The present paper describes recent studies performed on this type of bipolar transistor irradiated with 1.9 and 2.2 MeV electron beams in the dose range 5–50 kGy. Dose response, post-irradiation heat treatment and stability, effects of temperature during irradiation in the range from –104 to +22 °C, dependence on temperature during reading in the range 20–50 °C, and the difference in response of the transistors irradiated from the plastic side and the copper side are reported. DLTS measurements performed on the irradiated devices to identify the recombination centres introduced by radiation and their dependence on dose and energy of the electron beam are also reported.     

Switchable electrode functionalized with an azobenzene-containing copolymer thin film using the Langmuir–Schaefer technique for a “smart” uric acid/air fuel cell

A new photoswitchable electrode triggered by a brief light signal was fabricated by depositing an azobenzene-containing copolymer on an indium tin oxide substrate decorated with gold nanoparticles. The polymer formed a compact, complete thin film on the electrode surface using the Langmuir–Schaefer technique and offered reversible and stable switching performance. The conductivity and hydrophilicity of the electrode changed under UV/visible light due to the photoisomerization of the azobenzene moieties in the polymer film, influencing electron transfer and mass transport at the electrode. The electrochemical characterization demonstrated that the electrode exhibited reversibly switchable electrochemical behavior. In its active state, the as-prepared electrode possessed efficient electrocatalytic capability towards uric acid oxidation with a maximum anodic current density of 0.97 mA·cm^− 2. The uric acid/air fuel cell assembled from the photo-triggered anode and a Pt/C-modified cathode operated with an open circuit voltage of 0.12 V and a maximum power density of 41.33 μW·cm^− 2. The cell exhibited reversible switching performance (four cycles) and high stability: after one month the power output was 94.2% of the original maximum value.     

Microstructural modifications in swift ion irradiated PET

Polyethylene terephthalte (PET) was irradiated with carbon (70 MeV) and copper (120 MeV) ions to analyze the induced modifications with respect to optical, structural and thermal properties. In the present investigation, the fluence for carbon irradiation was varied from 1×10¹¹ to 1×10¹⁴ ions cm⁻², while that for copper beam was kept in the range of 1×10¹¹ to 1×10¹³ ions cm⁻². UV–vis, FTIR, XRD and DSC techniques were utilized to study the induced changes. The analysis of UV–vis absorption studies reveals that there is decrease of optical energy gap up to 10% on carbon ion irradiation (at 1×10¹⁴ ions cm⁻²), whereas the copper beam (at 1×10¹³ ions cm⁻²) leads to a decrease of 49%. FTIR analysis indicated the formation of alkyne end groups along with the overall degradation of polymer with copper ion irradiation. X-ray diffraction analysis revealed that the semi-crystalline PET losses its crystallinity on swift ion irradiation. It was found that the carbon beam (1×10¹⁴ ions cm⁻²) decreased the crystallite size by 16% whereas this decrease is of 12% in case of the copper ion irradiated PET at 1×10¹³ ions cm⁻². The loss in crystallinity on irradiation has been supported by DSC thermograms.     

A study on solution deposited CuSCN thin films: Structural,electrochemical, optical properties

A cost-effective successive ionic layer adsorption and reaction (SILAR) method was used to deposit copper (I) thiocyanate (CuSCN) thin films on glass and steel substrates for this study. The deposited thin films were characterized for their structural, morphological, optical and electrochemical properties using X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible spectroscopy and VersaSTAT potentiostat. A direct band gap of 3.88 eV and 3.6 eV with film thickness of 0.7 μm and 0.9 μm was obtained at 20 and 30 deposition cycles respectively. The band gap, microstrain, dislocation density and crystal size were observed to be thickness dependent. The specific capacitance of the CuSCN thin film electrode at 20 mV/s was 760 F g⁻¹ for deposition 20 cycles and 729 F g⁻¹ for deposition 30 cycles.     

Effects of gamma and electron beam irradiation on the survival of pathogens inoculated into sliced and pizza cheeses

The objective of this study was to identify the efficacy of gamma and electron beam irradiation of the food-borne pathogens (Listeria monocytogenes and Staphylococcus aureus) in sliced and pizza cheeses commercially available in the Korean market. Total aerobic bacteria and yeast/mold in the cheeses ranged from 10² to 10³ Log CFU/g. Irradiation of 1 kGy for sliced cheese and 3 kGy for pizza cheese were sufficient to lower the total aerobic bacteria to undetectable levels (10¹ CFU/g). Pathogen inoculation test revealed that gamma irradiation was more effective than electron beam irradiation at the same absorbed dose, and the ranges of the D₁₀ values were from 0.84 to 0.93 kGy for L. monocytogenes and from 0.60 to 0.63 kGy for S. aureus. Results suggest that a low dose irradiation can improve significantly the microbial quality and reduce the risk of contamination of sliced and pizza cheeses by the food-borne pathogens which can potentially occur during processing.     

Modelling of phenol removal in aqueous solution depending on the electron beam energy

This paper deals with the influence of the electron beam energy (E=1.2–3 MeV; I=20–125 μA; D_R=1.3–8.3 kGy s⁻¹) on the degradation of phenol in aqueous solution. The decomposition of phenol and the concentration of its principal by-products are significantly influenced by the energy of the electron beam. The degradation yield increases with the electron energy. A simplified phenomenologic model of the reactor was proposed to describe the results.     

Effects of electron beam irradiation on the microbial growth and quality of beef jerky during storage

Electron beam irradiation was applied to improve the microbial safety of beef jerky during storage. Beef jerky samples were irradiated at doses of 1, 3, 5, and 10 kGy and stored at 20 °C for 60 d. Microbiological data indicated that the populations of total aerobic bacteria significantly decreased with increasing irradiation dosage. In particular, the populations of total aerobic bacteria were significantly decreased by 1.76 log CFU/g at 10 kJ/m², compared to the control. Color measurements showed reduced Hunter L and a values of beef jerky for all the treatments during storage, and the Hunter L, a, and b values of beef jerky were not significantly different among the treatments. Sensory evaluation results also showed that electron beam irradiation did not affect sensory scores in overall during storage. Therefore, the results suggest that electron beam irradiation could be useful in improving the microbial safety without impairing the quality of beef jerky during storage.     

Combined radiolytic and catalytic oxidizing method to remove toluene in gas phase

We enhanced the decomposition and the removal of toluene in gas phase using a combined method that consists of electron beam (EB) irradiation and catalytic oxidation. The catalytic oxidation system comprises oxidizing particles of 0.1 wt% Pt or 0.1 wt% Pd deposited to supporting materials, which were also used as adsorbents. These adsorbents—supporting materials are Cordierite, Y-zeolite, and γ-alumina. We demonstrated that 100% removal of toluene can be achieved using approximately 9 kGy of dose level in the presence of Pt or Pd deposited to 12 wt%. The G (-toluene) values were determined to be 0.498 and 0.829 μmol/J in the absence and presence of these catalysts with adsorbents, respectively. We have also demonstrated that the presence of the oxidation-catalyst prevents the toluene from undergoing radiolytic polymerization.     

Advanced oxidation of aromatic VOCs using a pilot system with electron beam–catalyst coupling

The decomposition of volatile organic compounds (VOCs) using a pilot system of electron beam (EB)–catalyst coupling was investigated. Two aromatic VOCs, toluene (1800 ppmC) and o-xylene (1500 ppmC), were irradiated with a dose range of 0–10 kGy at room temperature. The removal efficiencies for toluene and o-xylene were 92.4% and 94.5%, respectively, under a 10 kGy absorbed dose condition, which were higher than the results of 45.7% and 52.3% when EB-only was used, respectively. The CO₂ selectivity approached 100% for both toluene and o-xylene using the EB-catalyst coupling system, while the concentrations of O₃ formed were 0.02 ppm (toluene) and 0.003 ppm (o-xylene) at 10 kGy. The aerosol concentration was also measured as 43.2 μg/m³ (toluene) and 53.4 μg/m³ (o-xylene) at 10 kGy absorbed dose.     

Effect of electron beam irradiation on dynamic mechanical,thermal and morphological properties of LLDPE and PDMS rubber blends

The effect of electron beam irradiation on the blends of linear low-density polyethylene (LLDPE) and poly dimethyl siloxane rubber (PDMS) prepared over a wide range of compositions starting from 70:30 to 30:70 (LLDPE: PDMS) by varying the radiation doses from 50 to 300 kGy has been studied. The dynamic modulii and dielectric strength of the blends increase on irradiation at 100 kGy as compared to that for the unirradiated blends. Degree of crystallinity and melting behaviour remain unchanged upon irradiation upto a dose of 100 kGy, beyond which it decreases. Thermal stability increases with increase in the proportion of PDMS rubber in the blend as well as on irradiation at 100 kGy. The phase morphology of the blends examined under the SEM exhibit two phase morphology before electron beam irradiation, whereas single phase morphology is observed after electron beam irradiation due to intra- as well as inter-molecular crosslinking leading to a miscible system.     

Fabrication and electrochemical characterization of interdigitated nanoelectrode arrays

Interdigitated nanoelectrode arrays with controlled electrode bandwidth and gap geometries ranging from 30 nm to 1 μm were fabricated on glass substrates by a planar process involving high resolution electron beam lithography and lift-off, and their characteristic electrochemical responses to an aqueous ferrocene derivative solution were examined using fundamental electrochemical techniques. Despite the comparatively large electrode area of electrode arrays containing 10 bands to a single band electrode, quasi-steady-state currents with high current density were obtained at a slow potential sweep rate in cyclic voltammograms of ferrocene derivative since the lateral dimension of the nanoelectrode arrays was considerably less than the scale of the diffusion layer of redox species. Additionally, it was demonstrated that the electrode thickness influenced limiting currents of voltammograms in the case of nanoelectrode arrays. In generation-collection mode experiments, furthermore, a collection efficiency as high as ∼99% was attained by 100 nm wide electrode arrays with a gap dimension of 30 nm.     

Mineralization of aqueous phenolate solutions: A combination of irradiation treatment and wet oxidation

Wet oxidation (high-temperature, high-pressure oxidation of organic wastes in aqueous solution) and radiation technology were combined in γ-ray and electron beam induced oxidation of 4×10^?4–1×10^?2 mol dm^?3 Na-phenolate solutions in a wide O₂ concentration (1–20 bar pressure) and absorbed dose (0–50 kGy) range. Most experiments were made in stainless steel high pressure autoclave equipped with magnetic stirrer. The rate of oxidation was followed by chemical oxygen demand and total organic carbon content measurements. The rate was similar in γ-ray and pulsed electron beam irradiation and increased with O₂ concentration in the liquid.