Vol.18,

The molar extinction coefficients at the absorption maximum of the solvated electron spectrum have been evaluated to be 900, 970, and 1000 mol^-1·m² for 1,2-ethanediol (12ED), 1,2-propanediol (12PD), and 1,3-propanediol (13PD), respectively. These values are two-third or three-fourth of the value usually reported in the published report. Picosecond pulse radiolysis studies have aided in depicting the radiolytic yield of the solvated electron in these solvents as a function of time from picosecond to microsecond. The radiolytic yield in these viscous solvents is found to be strongly different from that of the water solution. The temperature dependent absorption spectra of the solvated electron in 12ED, 12PD, and 13PD have been also investigated. In all the three solvents, the optical spectra shift to the red with increasing temperature. While the shape of the spectra does not change in 13PD, a widening on the blue side of the absorption band is observed in 12ED and 12PD at elevated temperatures.

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Photoinduced chemical reactions of 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]) were studied by laser photolysis at a wavelength of 266 nm. Excited triplet state ³[bmim]^+* was observed, radical cation [bmim] ²⁺^· and neutral [bmim]^· radical via photoionization were also formed. Energy transfer from ³[bmim]^+* to β-carotene was confirmed. Oxidation via one electron transfer from TMPD to ³[bmim]^+* was also observed and the rate constant was determined to be 1.2 × 10⁵ L·mol^-1·s^-1. The reaction of [bmim][PF₆] with hydrated electron (e_aq^-) was confirmed by laser photolysis in aqueous solution.

492

Pulsed photo-stimulated luminescence (PPSL) is a simple screening method that can be employed qualitatively at the spot for the detection of eggs treated with ionizing radiation. Due to the variations in the results during storage, the eggs of ostrich, duck, hen, and quail were irradiated to doses of 0, 1, 2, and 3 kGy. Most of the samples were incorrectly identified during storage after four months of irradiation. Thermoluminescence (TL) technique was also tried by using egg shells in order to confirm the irradiation treatment in eggs. TL glow curves were recorded between the temperatures 50 to 400 °C at the rate of 5 °/s for all the control and irradiated samples. On the basis of integrated areas of first glow curves (TL1), the glow curve ratios (TL1/TL2) and the shapes of maxima of TL1, the irradiation treatment of all the eggs was confirmed. Furthermore, the presence of calcite and aragonite minerals that cause the TL signal in the egg shells were studied using X-ray diffraction spectrometry.

443

Food irradiation is gaining popularity worldwide and this technology is important to improve quality and reduce the post harvest losses of food. Because of the rapid commercialization of irradiated foods throughout the world, compliance of different regulations relating to use of technology in different countries and demand of consumers for clear labelling of irradiated foods, there is need for the development of analytical methods to detect radiation treatment of food. Among several methods studied so far, thermoluminescence (TL) is an important method that can be used to find out the irradiation history of food that contain even a very minute amount of dust particles. In this study, the irradiated and unirradiated wheat and rice samples were analyzed using the TL method. The samples were purchased from the local market of Peshawar and irradiated to radiation doses of 0.5 and 1.0 kGy using Co-60 gamma irradiator at the Nuclear Institute for Food and Agriculture (NIFA), Peshawar. The mineral contaminants were isolated by jet water, ultrasonic treatment, and density gradient. TL glow curves of the isolated minerals from irradiated and unirradiated samples were recorded between the temperature ranges of 50-500^oC using a TL reader. Generally, the glow curves for irradiated samples showed much higher TL intensities (TL₁) than the unirradiated samples. The results were normalized by re-irradiation of mineral samples to gamma-ray dose of 1.0 kGy followed by determination of the second glow curves (TL₂). The ratio of the area of first glow curve to that of second glow curve (TL₁/TL₂) was calculated for selected temperature intervals and compared with the recommended values for unirradiated and irradiated samples. Finally, the shapes of the glow curves for irradiated and unirradiated samples were also analyzed. On the basis of these results (comparison of TL-intensities, TL₁/TL₂ ratios and shapes of the glow curves), all the irradiated and unirradiated samples of wheat and rice were unequivocally identified.

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Dependence of yields of OH (hydroxyl) radicals on the mass and specific energy of heavy ions and elapsed time after irradiation was investigated, to understand chemical reactions of aqueous solutions. The yields of irradiation products of phenol, super-linearly increased with the incident energy of He, C, and Ne ions ranging from 2 to 18 MeV/u. The yields of the OH radicals were estimated by analyzing the yields of the irradiation products of phenol. The yields of the OH radicals increased with the specific energy for each ion, but decreased both with the mass of each ion at the same specific energy and elapsed time after irradiation.

408

Carbon fiber-reinforced advance composites have been used for structural applications, mainly on account of their mechanical properties. The main factor for a good mechanical performance of carbon fiber-reinforced composite is the interfacial interaction between its components, which are carbon fiber and polymeric matrix. The aim of this study is to improve the surface properties of the carbon fiber using ionizing radiation from an electron beam to obtain better adhesion properties in the resultant composite. EB radiation was applied on the carbon fiber itself before preparing test specimens for the mechanical tests. Experimental results showed that EB irradiation improved the tensile strength of carbon fiber samples. The maximum value in tensile strength was reached using doses of about 250 kGy. After breakage, the morphology aspect of the tensile specimens prepared with irradiated and non-irradiated carbon fibers were evaluated. SEM micrographs showed modifications on the carbon fiber surface.

430

This article deals with the determination of the adsorption properties of metal ions and humic acid in water on crosslinked chitosan derivatives (carboxymethylchitosan) which were formed using the irradiation technique without any additives. The solubility test of these crosslinked materials were investigated in acidic, alkaline media, distilled water, and certain organic solvents. Scanning electron microscopic (SEM) images showed that the crosslinked chitosan derivatives possessed a porous morphological structure. Charged characteristic analyses demonstrated typically pH-dependent properties of the crosslinked materials. The adsorption studies were carried out by the batch method at room temperature. Adsorption of heavy metal ions (such as Cu²⁺, Cd²⁺) and humic acid onto crosslinked samples was found to be strongly pH-dependent. Adsorption kinetic studies indicated the rapid removal of metal ions, and humic acid from the aqueous solutions. Moreover, isothermal adsorption data revealed that Cu²⁺, Cd²⁺, and humic acid were removed by these crosslinked materials with high efficiency. Adsorption isothermal data were interpreted well by the Langmuir equation. These crosslinked carboxymethylated chitosan derivatives indicate favorable adsorption of metal ions and humic acid.

439

Radiation-induced grafting of styrene onto polytetrafluoroethylene (PTFE) membranes was studied by a simultaneous irradiation technique. Grafting was carried out using γ-radiation from a ⁶⁰Co source at room temperature. Effects of absorbed dose, atmosphere, dose rate, and the concentration of initial monomer on the degree of grafting (DOG) were investigated and the most appropriate grafting condition was obtained. Subsequently, sulphonation of the grafted PTFE membrane (PTFE-g-PS) was carried out and a series of ion exchange membranes (PTFE-g-PSSA) was prepared. Further characterizations of FTIR, TGA, and SEM testified that grafting and sulphonation of the membranes were successfully processed; moreover, grafting of styrene not only occurred in the surface of PTFE membrane, but also in the micropores of the membrane. Ion exchange capacity (IEC) and conductivity were found increase with the grafting yield. The results suggest that at a low dose, such as 17 kGy, the ion exchange membrane (IEM) which will be suitable for vanadium redox battery (VRB) use can be obtained.

426

In this study, hydrogels of P(NIPA-co-NVP)/clay were synthesized by γ-ray radiation. Different thermo-sensitive hydrogels were made under different experimental conditions such as dose, monomer ratio, and content of clay. X-ray diffraction shows that the layer distance between Na-clays is changed from 1.6 to 2.7 nm because Na-clay pieces can be intercalated or exfoliated by HTMAB, and that between P(NIPA-co-NVP)/Clay pieces is 3.4 nm. The swelling property tests show that the LCST of P(NIPA-co-NVP) is higher than PNIPA. With the increase of NVP content, LCST is higher. As the ratio of NIPA/NVP is 95/5, hydrogel shows the best swelling property and LCST is 37°C. LCST of P(NIPA-co-NVP)-clay hydrogel is not changed, but the strength and swelling properties are better.

433

Zn-doped TiO₂ catalysts were prepared using a sol-gel method and characterized by XPS,UV-Vis, BET, XRD in this study. Under the irradiation of simulant sunlight, the photocatalytic activity for the degradation of p-nitrophenol was studied too. After irradiation for 2.5 h, the degradation percentage of p-nitrophenol could rise to more than 80 %. The results showed that the spectrum absorption band edge of Zn/TiO₂ powder does not broaden obviously comparing with pure TiO₂ powder. Zinc exists as Zn (= 2 \* ROMAN II). When calcined at 973 K, there is a new phase as ZnTiO₃ in Zn/TiO₂ catalyst. The order of photocatalytic activity of Zn/TiO₂ catalysts calcined at different temperatures for p-nitrophenol is 773 K > 673 K > 873 K > 573 K > 973 K and the photocatalytic activity of Zn/TiO₂ catalyst calcined at 773 K is better than TiO₂ catalysts heated at the same temperature, and outclasses that of commercial TiO₂ catalyst. It also showed that the photocatalytic degradation of p-nitrophenol follows first-order kinetics under the irradiation of simulant sunlight.

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