TiO2@CdS core–shell nanorods films: Fabrication and dramatically enhanced photoelectrochemical properties

In this paper, we prepared TiO₂@CdS core–shell nanorods films electrodes using a simple and low-cost chemical bath deposition method. The core–shell nanorods films electrodes were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and UV–vis spectrometry techniques. After applying these TiO₂@CdS core–shell nanorods electrodes in photovoltaic cells, we found that the photocurrent was dramatically enhanced, comparing with those of bare TiO₂ nanorods and CdS films electrodes. Moreover, TiO₂@CdS core–shell nanorods film electrode showed better cell performance than CdS nanoparticles deposited TiO₂ nanoparticles (P25) film electrode. A photocurrent of 1.31 mA/cm², a fill factor of 0.43, an open circuit photovoltage of 0.44 V, and a conversion efficiency of 0.8% were obtained under an illumination of 32 mW/cm², when the CdS nanoparticles deposited on TiO₂ nanorods film for about 20 min. The maximum quantum efficiency of 5.0% was obtained at an incident wavelength of 500 nm. We believe that TiO₂@CdS core–shell heterostructured nanorods are excellent candidates for studying some fundamental aspects on charge separation and transfer in the fields of photovoltaic cells and photocatalysis.     

Photoelectrochemical solar cell properties of heteropolytungstic acid-incorporated TiO2 nanodisc thin films

Thin film of heteropolytungstic acid (HPA)-incorporated TiO₂ nanodisc was fabricated, and its photovoltaic performances were observed as a function of irradiation wavelength from 400 nm to 750 nm. Its incident photon-to-current efficiency (IPCE) was determined to be 18.6% around 500 nm, with energy conversion efficiency of 6.9%, which were observed to be further enhanced to 23% and 9%, respectively, by adsorption of ruthenium or porphyrin dyes. Complementary electron transports from both HPA and dyes to TiO₂ nanodisc seems to avoid most of the backward electron or hole transfer reactions to enhance the photoelectrochemical efficiencies of dye-sensitized solar cells.     

Modification of photocatalytic TiO2 thin films by electron beam irradiation

Noble metal-modified TiO₂ films were prepared by electron beam deposition of Pt, Pd, Au and Ag on the surface of TiO₂ films with diameters ranging from <1 nm to 500 nm. The morphology of the films was characterized by X-ray diffractometry (XRD), field emission scanning electron microscope (FMSEM) and transmission electron microscope (TEM). The photocatalytic capability of the films were tested and compared by degradation of methyl orange (MO) in aqueous solutions under both UV and visible light illumination.     

Control factors and by-products during decomposition of butane in electron beam irradiation

This research was conducted to determine the removal characteristics of butane, using an electron beam. Influential factors, such as an initial concentration, background gases (nitrogen, air, and helium), and absorbed doses (kGy) were investigated. The decomposition efficiencies of background gases showed that oxidation caused by radicals formed from gases, such as N₂ and O₂, had a greater influence on results than oxidation from primary electrons for butane removal. Removal efficiencies were 40% at 2.5 kGy and 66% at 10 kGy, when the initial concentration of butane was 60 ppmC. When the initial concentration was lower, the energy efficiency of butane removal by electron beam was higher. By-products, including CO₂, CO, acetaldehyde, and acetone, formed after electron beam irradiation. Concentrations of CO₂ and CO tended to increase when absorbed doses increased as butane was decomposed by the electron beam through an advanced oxidation.     

Catalytic conversion of CO2–CH4 mixture into synthetic gas—Effect of electron-beam radiation

The radiolysis of methane (0.7 MeV electron beam) was studied as a function of its concentration at two doses: 5 and 20 kGy. In both cases the G (–CH₄) value raised with the increase of the substrate concentration. Thereby the yields observed at 20 kGy are much lower, because of recombination processes. Results are also reported on the conversion of the gas mixture CH₄:CO₂:He=1:1:1 into synthetic gas (H₂/CO) at 500 °C, using two catalysts : (N5) and (N20), containing 5 wt% Ni and 20 wt% Ni, respectively, supported on γ-Al₂O₃. In an experimental series the catalysts (N5) and (N20) were treated by irradiation (4 MGy dose) before use. The highest conversion yields (above 35%) were observed by implementation of N5 and N20 catalyst at 500 °C under the influence of electron beam radiation.     

Highly efficient CdSe quantum-dot-sensitized TiO2 photoelectrodes for solar cell applications

With 4.2 nm quantum-dots (QDs) as seeds on TiO₂ film, a highly efficient TiO₂ photoelectrode was prepared by a seed-growing process using chemical bath deposition technique, followed by a covering process with ZnS layer, and a post-sintering process at 400 °C. The assembled solar cells presented IPCE peak values of 73% and power conversion efficiency of 3.21% under AM 1.5 G irradiation.     

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.     

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.     

Facile synthesis of thick ordered mesoporous TiO2 film for dye-sensitized solar cell use

Crack-free thick ordered mesoporous TiO₂ films with excellent optical quality have been synthesized by combination of “Doctor Blade” technique and a two-step evaporation induced self-assembly (EISA) method. By employing the as-synthesized mesoporous film with the thickness of 7 μm as the photoanode in dye-sensitized solar cell (DSC), a solar conversion efficiency of 6.53% has been obtained at 30 mW cm⁻² light intensity.     

Preparation and photocatalytic activity of Cu-deposited TiO2 film with high transparency

Cu-deposited TiO₂ films were prepared by photoreduction of Cu(II) in the presence of sodium formate. With the initial Cu(II) concentrations more than 100 mg L^?1, induction periods were observed before the transmittance decreased. Scanning electron microscopy indicated that Cu particles of 2.6 ± 0.5 μm were deposited isolatedly with much open space in the induction periods. The films prepared by changing the irradiation time within the induction periods showed a higher photocatalytic activity than a pure TiO₂ for the degradation of methylene blue under the reaction condition without purging air.     

Cross-linking of poly(N-vinyl pyrrolidone) films by electron beam irradiation

Biocompatible hydrogels based on poly(N-vinyl pyrrolidone) (PVP) were synthesized by electron beam irradiation of the dry polymer under various conditions. Sol–gel analysis of the bulk gel (in mm range) gave a dose of gelation of 94 kGy. As seen for various other polymers, the network density rises with the increase in dose. At around 350 kGy, PVP began to decompose. Based on these observations, films in μm range on a silicon wafer were synthesized by electron beam irradiation. Due to irradiation, the films adhered irreversibly on the wafer. Their swelling behavior was analyzed by ellipsometry.     

Electron beam irradiation of fluoropolymers containing polyethers

A highly fluorinated monomer, 1,3-bis(1,1,1,3,3,3-hexafluoro-2-pentafluorophenyl methoxy-2-propyl)benzene (12F-FBE) was polymerized with some diphenols by polycondensation and then was electron beam irradiated between 100 and 1000 kGy to determine degradation radiochemistry yield (G_s) by gel permeation chromatography (GPC). The samples were characterized after irradiation by DSC, FTIR, and nuclear magnetic resonance (NMR). The fluoropolymers show apparent degradation in mechanical properties at 300 kGy, except 12F-FBE polymerized with biphenol and bisphenol A, when they did not show any apparent physical change up to 300 kGy; and continue to be flexible and transparent, with a radiochemical yield scission (G_s) of 0.75, 0.53, 0.88, and 0.38 for 12F-FBE/SDL aliphatic, 12F-FBE/biphenol, 12F-FBE/bisphenol A, and 12F-FBE/bisphenol O, respectively. The number average molecular weights for three of the polymers decrease upon 1000 kGy irradiation to 10% of their original values; however, the polymer from bisphenol A is much more stable and its M_n decreases to only 24% of original.     

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.     

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.     

Oxidation of gaseous styrene by electron beam irradiation

In this research, the absorbed dose, background gases, relative humidity, and initial concentrations were selected as control factors to discover decomposition characteristics of styrene using electron beam irradiation. It was confirmed that a considerable amount of styrene was removed by primary electrons as well as radicals and ions, which were produced after the electron beam irradiation. Moreover, the removal efficiencies of styrene were observed to rise when the initial concentration was lower, moisture content was higher, and the absorbed dose increased. For instance, 50 ppmv styrene showed extremely high removal efficiency (over 98%) at a condition of 2.5 kGy. A small amount of styrene oxide, benzaldehyde, aerosol, CO, and CO₂ were produced as by-products after EB irradiation.     

Quality of fresh-cut Iceberg lettuce and spinach irradiated at doses up to 4 kGy

Fresh-cut Iceberg lettuce packaged in modified atmosphere packages and spinach in perforated film bags were irradiated with gamma rays at doses of 0, 1, 2, 3, and 4 kGy. After irradiation, the samples were stored for 14 days at 4 °C. O₂ levels in the packages of fresh-cut Iceberg lettuce decreased and CO₂ levels increased with increasing radiation dose, suggesting that irradiation increased respiration rates of lettuce. Tissue browning of irradiated cut lettuce was less severe than that of non-irradiated, probably due to the lower O₂ levels in the packages. However, samples irradiated at 3 and 4 kGy had lower maximum force and more severe sogginess than the non-irradiated control. In addition, ascorbic acid content of irradiated lettuce was 22–40% lower than the non-irradiated samples after 14 days of storage. The visual appearance of spinach was not affected by irradiation even at a dose of 4 kGy. Consumer acceptance suggested that more people would dislike and would not buy spinach that was treated at 3 and 4 kGy as compared to the non-irradiated sample. Overall, irradiation at doses of 1 and 2 kGy may be employed to enhance microbial safety of fresh-cut Iceberg lettuce and spinach while maintaining quality.     

Microbial quality evaluation and effective decontamination of nutraceutically valued lotus seeds by electron beams and gamma irradiation

Lotus seeds are nutraceutically valued natural plant produce, which succumbs to microbial contamination, predominantly to toxigenic moulds. Results of the present study revealed seed coat portion to harbor higher proportion of microbial load, particularly fungi than cotyledon portion. Among the mycotoxins analyzed, aflatoxins (B₁, B₂, G₁ and G₂) were below detectable limits, while the seeds were devoid of Ochratoxin-A (OTA). Application of different doses of electron beam and gamma irradiation (0, 2.5, 5, 7.5, 10, 15 and 30 kGy) for decontamination purpose revealed significant dose-dependent decrease in the fungal contaminants (P<0.05). However, the contaminant yeasts could survive up to 10 kGy dose, which could be completely eliminated at 15 kGy. From the results obtained, a dose range between 10 and 15 kGy is recommended for complete decontamination, as these doses have also been shown earlier to have minimal effects on nutritional and functional properties of lotus seeds.     

X-ray induced photocatalysis on TiO2 and TiO2 nanotubes: Degradation of organics and drug release

The photocatalytic activity of titanium dioxide under X-ray radiation is of great interest for biomedical applications. In the present work we explore the use of compact TiO₂ layers and TiO₂ nanotubes for X-ray induced photocatalysis, in particular the degradation of organics and monolayer chain scission for drug release. The radiation was done with a conventional X-ray source and doses up to 50 × 10^?3 J/kg. The results show the feasibility of X-ray catalysis on TiO₂ and X-ray induced monolayer chain scission by the release of surface attached Zn–porphyrin molecules. Furthermore, a higher efficiency for anatase films and nanotubes is obtained than for amorphous morphologies.     

Synthesis and photovoltaic properties of organic sensitizers containing electron-deficient and electron-rich fused thiophene for dye-sensitized solar cells

Diverse fused thiophenes with electron-rich and electron-deficient blocks have been synthesized and employed as the π-conjugated spacers of organic dyes for the dye-sensitized solar cells (DSSCs). The effects of these fused thiophenes were investigated by their absorption spectra, electrochemical and photovoltaic properties. For a typical device a maximum power conversion efficiency of 6.11% was obtained under simulated AM 1.5 irradiation (100 mW cm^?2): a short-circuit current (J_SC) of 14.47 mA cm^?2, an open-circuit voltage (V_OC) of 670 mV, and a fill factor (FF) of 0.63.     

Effect of gamma radiation on the mechanical and barrier properties of HEMA grafted chitosan-based films

Chitosan films were prepared by dissolving 1% (w/v) chitosan powder in 2% (w/v) aqueous acetic acid solution. Chitosan films were prepared by solution casting. The values of puncture strength (PS), viscoelasticity coefficient and water vapor permeability (WVP) of the films were found to be 565 N/mm, 35%, and 3.30 g mm/m² day kPa, respectively. Chitosan solution was exposed to gamma irradiation (0.1–5 kGy) and it was revealed that PS values were reduced significantly (p≤0.05) after 1 kGy dose and it was not possible to form films after 5 kGy. Monomer, 2-hydroxyethyl methacrylate (HEMA) solution (0.1–1%, w/v) was incorporated into the chitosan solution and the formulation was exposed to gamma irradiation (0.3 kGy). A 0.1% (w/v) HEMA concentration at 0.3 kGy dose was found optimal-based on PS values for chitosan grafting. Then radiation dose (0.1–5 kGy) was optimized for HEMA grafting. The highest PS values (672 N/mm) were found at 0.7 kGy. The WVP of the grafted films improved significantly (p≤0.05) with the rise of radiation dose.