Radiation induced in-situ generation of conductivity in the blends of polyaniline-base with chlorinated-polyisoprene

Radiation induced acid doping of PANI to generate electrical conductivity was achieved by radiation induced HCl release from chlorinated-polyisoprene (ClPIP). Blends of PANI with ClPIP were prepared by mechanical mixing/grinding in the composition range of 9–43% ClPIP by weight and pelletized under 10 t press. The pellets were irradiated in ⁶⁰Co Gammacell in air at room temperature to doses up to 300 kGy. The maximum electrical conductivity increase was observed for the blend PANI43 which changed from 10^?10 to 10^?4 S cm^?1 when it was irradiated to 300 kGy dose. Radiation induced changes on the blends were also studied by UV–vis spectroscopy using reflection technique and FTIR spectroscopy. The broad absorption band in the visible range (630 nm) increased by increasing irradiation dose. The band (1110 cm^?1) in the IR spectra which is indicative of conductivity showed linear correlation with irradiation dose.     

Preparation of conducting silver paste with Ag nanoparticles prepared by e-beam irradiation

Conducting silver paste was prepared by using Ag nanoparticles which were synthesized by e-beam irradiation method (from KAERI); its conductivity was comparatively determined with Ag nanoparticles which were prepared by thermolysis method (commercial). The silver nanoparticles with the diameter of approximately 150 nm size prepared by e-beam irradiation were mixed with glass frit and sintered for 1 h at 500 °C. It is presumably concluded that the wt% of silver nanoparticle, size distribution and homogenous dispersibility of Ag nanoparticles in the pastes are the critical factors for the high conductivity of the paste. Among the various wt% of silver nanoparticle in the conducting silver pastes, silver paste with 90 wt% of silver nanoparticle has the highest conductivity as 1.6×10⁴ S cm^?1. This conductivity value is 1.6 times higher than the Ag pastes which were prepared with silver nanoparticles obtained by thermolysis method.     

Systematic fabrication of chitosan nanoparticle by gamma irradiation

The present investigation is mainly focused on the systematic preparation of chitosan nanoparticle in the potential range 1–100 nm using γ-ray irradiation. The effect of irradiation conditions in terms of physical form of chitosan, i.e. flake, colloidal and acidic solution, and γ-ray dose was studied. The molecular weights of chitosan were 10, 25, and >1000 times reduced when irradiated with the γ-ray dose as high as 100 kGy in Chi-flake, Chi-colloid, and Chi-acid, respectively. The particle size reduced to 70 nm after being irradiated to only 10 kGy γ-rays and it showed a tendency to decrease when the γ-ray doses were increased. The γ-rays effectively induced the reduction of chitosan particle size to <100 nm with narrow size distribution. The effective size reduction was particularly observed in Chi-colloid. Heterogeneous chemical conjugation of deoxycholic acid onto 10 kGy irradiated Chi-colloid resulted in narrow particle size as small as 50 nm.     

Surface-enhanced Raman studies of bradykinin using colloidal gold

In this paper, bradykinin (BK), an endogenous peptide hormone, which is involved in a number of physiological and pathophysiological processes was deposited onto the colloidal Au nanoparticles. The surface-enhanced Raman spectroscopy (SERS) was used to determine the adsorption mode of BK under different environmental conditions, including: excitation wavelengths (514.5 nm and 785.0 nm), pH of aqueous sol solutions (from pH = 3 to pH = 11), and size of the colloidal nanoparticles (10, 20, and 50 nm). The metal surface plasmon of the colloidal suspended Au nanoparticles was examined by ultraviolet-visible (UV–vis) spectroscopy. The results showed that the C-terminal part of BK plays a crucial role in the adsorption process onto the colloidal suspended Au particles. The Phe^5/8 and Arg⁹ residues of BK mainly participate in the interactions with the colloidal Au nanoparticles. At acidic pH of the solution (pH = 3), the BK COO⁻ terminal group through the both oxygen atoms strongly binds to the Au nanoparticles. The Phe⁵/Phe⁸ rings adopt tilted orientation with respect to the colloidal Au nanoparticles with diameters of 10 and 20 nm. As the particle size increases to 50 nm, the flat orientation of the Phe ring(s) with respect to the Au nanoparticles is observed.     

Effect of gamma irradiation on microbial decontamination,and chemical and sensory characteristic of lycium fruit

Lycium fruit, popular traditional Chinese medicine and food supplement generally is ingested uncooked, was exposed to several doses of gamma irradiation (0–14 kGy) to evaluate decontamination efficiency, changes in chemical composition, and changes in sensory characteristic. In this study, lycium fruit specimens contained microbial counts of 3.1×10³–1.7×10⁵ CFU/g and 14 kGy was sufficient for microbial decontamination. Before irradiation, the main microbe isolated from lycium fruit was identified as a strain of yeast, Cryptococcus laurentii. After 10 kGy of irradiation, a Gram-positive spore-forming bacterium, Bacillus cereus, was the only survivor. The first 90% reduction (LD₉₀) of C. laurentii and B. cereus was approximately 0.6 and 6.5 kGy, respectively, the D₁₀ doses of C. laurentii and B. cereus was approximately 0.6 and 1.7 kGy, respectively. After 14 kGy irradiation, except the vitamin C content, other chemical composition (e.g., crude protein, β-carotene, riboflavin, fructose, etc.) and the sensory characteristic of lycium fruit specimens did not have significant changes. In conclusion, 14 kGy is the optimal decontamination dose for lycium fruit for retention of its sensory quality and extension of shelf life.     

High-energy ionising radiation initiated decomposition of acetovanillone

Hydroxyl radical, hydrated electron and hydrogen atom intermediates of water radiolysis react with acetovanillone with rate coefficients of (1.05±0.1)×10¹⁰, (3.5±0.5)×10⁹ and (1.7±0.2)×10¹⁰mol^?1 dm³ s^?1. Hydroxyl radical and hydrogen atom attach to the ring forming cyclohexadienyl type radicals. The hydroxyl–cyclohexadienyl radical formed in hydroxyl radical reaction in dissolved oxygen free solution partly transforms to phenoxyl radical. In the presence of O₂ phenoxyl radical formation and ring destruction are observed. Hydrated electron in O₂ free solution attaches to the carbonyl oxygen and undergoes protonation yielding benzyl type radical. In air saturated 0.5 mmol dm^?3 solution using 15 kGy dose most part of acetovanillone is degraded, for complete mineralisation five times higher dose is required. The experiments clearly show that acetovanillone can be efficiently removed from water by applying irradiation technology.     

Enhanced mass transfer during solid–liquid extraction of gamma-irradiated red beetroot

The exposure to gamma-irradiation pretreatment increases cell wall permeabilization, resulting in loss of turgor pressure, which led to the increase of extractability of betanin from red beetroot. The degree of extraction of betanin was investigated using gamma irradiation as a pretreatment prior to the solid–liquid extraction process and compared with control beetroot samples. The beetroot subjected to different doses of gamma irradiation (2.5, 5.0, 7.5, 10.0 kGy) and control was dipped in an acetic acid medium (1% v/v) to extract the betanin. The diffusion coefficients for betanin as well as ionic component were estimated considering Fickian diffusion. The results indicated an increase in the diffusion coefficient of betanin (0.302×10⁻⁹–0.463×10⁻⁹ m²/s) and ionic component (0.248×10⁻⁹–0.453×10⁻⁹ m²/s) as the dose rate increased (from 2.5 to 10.0 kGy). The degradation constant was found to increase (0.050–0.079 min⁻¹) with an increase gamma-irradiation doses (2.5–10.0 kGy), indicating lower stability of the betanin as compared to control sample at 65 °C.     

Biomimetic synthesis of silver nanoparticles by Citrus limon (lemon) aqueous extract and theoretical prediction of particle size

In the present study, silver nanoparticles were rapidly synthesized at room temperature by treating silver ions with the Citrus limon (lemon) extract. The effect of various process parameters like the reductant concentration, mixing ratio of the reactants and the concentration of silver nitrate were studied in detail. In the standardized process, 10^?2 M silver nitrate solution was interacted for 4 h with lemon juice (2% citric acid concentration and 0.5% ascorbic acid concentration) in the ratio of 1:4 (vol:vol). The formation of silver nanoparticles was confirmed by Surface Plasmon Resonance as determined by UV–Visible spectra in the range of 400–500 nm. X-ray diffraction analysis revealed the distinctive facets (1 1 1, 2 0 0, 2 2 0, 2 2 2 and 3 1 1 planes) of silver nanoparticles. We found that citric acid was the principal reducing agent for the nanosynthesis process. FT-IR spectral studies demonstrated citric acid as the probable stabilizing agent. Silver nanoparticles below 50 nm with spherical and spheroidal shape were observed from transmission electron microscopy. The correlation between absorption maxima and particle sizes were derived for different UV–Visible absorption maxima (corresponding to different citric acid concentrations) employing “MiePlot v. 3.4”. The theoretical particle size corresponding to 2% citric acid concentration was compared to those obtained by various experimental techniques like X-ray diffraction analysis, atomic force microscopy, and transmission electron microscopy.     

New applications of the VDmax approach to substantiation of preselected sterilization doses

The VD_max approach for substantiation of 25 kGy has been in use for more than 10 years. VD_max methods are included in ISO 11137-2:2006 and AAMI TIR33:2005. ISO Technical Specification, 13004, is under development that will include sterilization doses from 15 to 35 kGy.For substantiation of a sterilization dose for very low bioburden products, less than or equal to 0.3, values of VD_max have now been derived and tabulated for a sterilization dose of 12.5 kGy.Products have been encountered that have both low bioburden and a relatively low maximum dose. In several situations, existing tabulated VD_max values could not be effectively used; in one such situation, the average bioburden was too high to substantiate a 15 kGy sterilization dose and the use of a 17.5 kGy sterilization dose was not practicable due to the likelihood of exceeding the product's maximum acceptable dose. For this product, values of VD_max were derived and tabulated for substantiation of a 16.1 kGy sterilization dose.Values of VD_max have been derived and tabulated for the substantiation of sterilization doses linked to a sterility assurance level (SAL) of 10^?3. To offer a potential alternative to aseptic processing, the notion of using an “aseptic processing equivalent dose”, 10^?4 SAL, has been investigated along with the use of alternate model populations for calculation of VD_max values.     

Effect of gamma irradiation on the expressed proteins in the foodborne pathogen Staphylococcus aureus

A capillary electrophoresis method with UV detection was developed to analyze protein composition of the foodborne pathogen Staphylococcus aureus. Bacterial samples containing 10⁹ CFU/ml, obtained after two cycles of incubations of 24 h, were gamma irradiated at different doses of 1.2, 3.5 and 2.9 kGy to respectively create damage cells, to kill cells and to provoke viable but non cultivable cells (VBNC). It was observed that an irradiation at a sensitive dose of 1.2 kGy caused a significantly increase in the protein with molecular weight (MW) of 17.7 kDa (from 0.61% to 1.2%). This treatment also caused decreases in the expressed proteins with the MWs of 16.3 kDa (from 6.2% to 5.3%) and of 23.4 kDa (from 4.0% to 2.30%). Irradiation at a VBCN dose of 2.9 kGy caused increases in expressed proteins with the MWs of 17.7 kDa (from 0.61% to 3.43%), 18.7 kDa (from 1.04% to 4.30%), 19.5 kDa (from 0.71% to 2.30%), 21.1 kDa (from 1.20% to 3.80%). Moreover, this treatment (2.9 kGy) also caused significantly decreases (P≤0.05) in the expressed proteins with the MW of 30.7 kDa (from 8.6% to 5.15%), 36.3 kDa (from 3.1% to 2.7%) and 40.5 kDa (from 11.3% to 8.5%). Finally, for the irradiation at a lethal dose of 3.5 kGy, it can be found that the expressed proteins with the MW of 17.7 kDa, 18.7 kDa and 19.5 kDa were increased less than that of expressed proteins at the VCNC dose (2.9 kGy) and these might be the very important proteins which are responsible for the survival of the S. aureus. Further, there were also the decreases in expressed proteins with the MW of 30.7 kDa, 36.3 kDa and 75.1 kDa at this dose of treatment (3.5 kGy) which can be expected that these proteins are seriously affected at high dose of γ-irradiation treatment.     

Decomposition of persistent pharmaceuticals in wastewater by ionizing radiation

Pharmaceuticals in wastewater were treated by the combined method of activated sludge and ionizing radiation in laboratory scale. Oseltamivir, aspirin, and ibuprofen at 5 μmol dm^?3 in wastewater were decomposed by the activated sludge at reaction time for 4 h. Carbamazepine, ketoprofen, mefenamic acid, clofibric acid, and diclofenac were not biodegraded completely, but were eliminated by γ-ray irradiation at 2 kGy. The rate constants of the reactions of these pharmaceuticals with hydroxyl radicals were estimated by the competition reaction method to be 4.0–10×10⁹ mol^?1 dm³ s^?1. Decompositions of the pharmaceuticals in wastewater by ionizing radiation were simulated by use of the rate constants and the amount of total organic carbon as parameters. Simulation curves of concentrations of these pharmaceuticals as a function of dose described the experimental data, and the required dose for the elimination of them in wastewater by ionizing radiation can be estimated by this simulation.     

Radiation-induced grafting of styrene into poly(vinylidene fluoride) film by simultaneous method with two different solvents

Radiation-induced grafting of styrene into poly(vinylidene fluoride) (PVDF) films with 0.125 mm thickness at doses of 1 and 2.5 kGy in the presence of a styrene/N,N-dimethylformamide (DMF) solution (1:1, v/v) and at doses of 20, 40 and 80 kGy in presence of a styrene/toluene solution (1:1, v/v) at dose rate of 5 kGy h^?1 was carried out by the simultaneous method under nitrogen atmosphere and room temperature, using gamma rays from a Co-60. The films were characterized before and after modification by calculated grafting yield (GY %), infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetry (TG/DTG). GY results shows that grafting increases with dose, and the grafting of styrene was confirm by FT-IR due to the new characteristic peaks and by the TG and DSC attributed to changes in thermal behavior of the grafted material. Results showed that the system allows the controlled grafting of styrene into PVDF using gamma rays at doses as low as 1 kGy in DMF.     

Demonstration of cavity enhanced FTIR spectroscopy using a femtosecond laser absorption source

A proof of principle experiment was performed by recording the cavity enhanced absorption spectrum of the weak b–X transition of molecular oxygen in the atmosphere using a Ti:Sa femtosecond laser as an absorption source and a high resolution continuous scan Fourier transform interferometer. The cavity was mode matched and either continuously scanned or stabilized at the so-called magic point. An optimal rms noise equivalent absorption of 3 × 10^?7 cm^?1 Hz^?1/2 was reached in the latter case, corresponding to α_min = 3 × 10^?7 cm^?1.     

Spectrofluorimetric determination of fexofenadine hydrochloride in pharmaceutical preparation using silver nanoparticles

A novel sensitive fluorimetric method was investigated for the assay of fexofenadine hydrochloride (FEX) using silver nanoparticles (NPs) as a fluorescence probe. The NPs, which were prepared by chemical reduction of silver nitrate with sodium borohydride (reducing agent) in aqueous solution (without organic stabilizers) were water soluble, stable and had narrow emission band. The addition of drug to NPs solution caused considerable quenching of the emission band of silver NPs, which was likely due to the complexation of the drug to silver NPs. Under the optimum conditions, the quenched fluorescence (FL) intensity was linear with the concentration of FEX in the range of 1 × 10^?7 to 2.5 × 10^?5 mol L^?1 (0.9985) with a detection limit of 1.2 × 10^?8 mol L^?1. The quenching mechanism of the studied drug on the emission band of silver NPs was explained by Stern–Volmer law. The developed method was applied to FEX determination in a pharmaceutical formulation (allegra tablets) and biological fluids (human serum and urine).     

Sensory evaluation by gamma radiation effect on protein allergen of laying hen eggs

Although considered the most complete food and nutritionally shown to be part of a healthy diet, the egg is the source of many eating disorders, especially for infants. Irradiation has been used in studies not only as a means of microbiological control, but also on its structural action in the substances molecules and has been used to reduce the allergenic effects. The aim of this study was to evaluate the sensory effects of Co⁶⁰ gamma radiation on proteins, enabling the acceptability of allergy food for genetically intolerant people. Eggs commercial fresh and freeze-dried and subjected to gamma irradiation by Co⁶⁰ source at doses 0 (control), 10 kGy; 20 kGy and 30 kGy and rates of doses of 19.4 kGy/h and 31.8 kGy/h. Acceptability test was used by the hedonic scale, since it is necessary to know the “affective status” of consumers for the product, implying a preference, i.e. the most preferred samples are the most accepted and vice versa. The samples were presented as the habit of consumption (cooked) to a group of 41 adults panelists of both gender, aged from 21 to 40 years, and served under complete block design balanced with respect to the order of presentation. The evaluated attributes was flavor, appearance and overall acceptability. In general, for boiled eggs and freeze-dried, it was observed that the control sample was the most acceptable, followed by the sample irradiated with 10 kGy in both dose rates. In addition, panelists presented in testimony that they found interesting changes due to irradiation; also said they would not buy the product because of the marked change in appearance and smell, which at one point he ended up in disgust and detract from sales of the product, but they would buy irradiated with 10 kGy in both dose rate and dose of 20 kGy at a dose rate of 19.4 kGy/h.     

Post-irradiation thermal degradation of PA6 and PA6,6

PA 6 and PA6,6 sheets irradiated with electron beam were investigated in relation to their thermal stability in various environments (air, distilled water and NaCl 5% solution) at 70 °C. The preexposure doses were 100, 200, 400 and 600 kGy at a dose rate of 22.4 kGy/s. The FTIR spectra allowed the evaluation of the progress of sample oxidation by elucidating the contributions of each environment to the ageing of polyamides. The increases in the absorbance at 1652 cm^?1 placed the surrounding aggressive attack in the following sequence: air<water<NaCl solution. A scheme of degradation mechanism is proposed for the explanation on the involvement of amidic units.     

Radiation induced degradation of pharmaceutical residues in water: Chloramphenicol

The γ-radiolytic degradation of chloramphenicol (CPL) was investigated in 0.1–1 mmol dm^?3 aqueous solutions at various radiation conditions. The destruction of CPL was monitored by UV–vis spectrophotometric method through the decrease in the intensity of the absorbance band at 276 nm. LC-MS/MS was used to identify the degradation products. Results indicate that ^?OH can add onto the CPL aromatic ring or can abstract H-atom from the side chain. The reductive dechlorination of CPL was also studied based on the reaction of e_aq^? with CPL. In 0.1 mmol dm^?3 solution above 2.5 kGy dose complete CPL degradation was achieved. In the presence of dissolved oxygen at relatively low dose, various oxidation products were observed. In the presence of tertiary butanol radical scavenger tertiary butanol group containing products were also detected. The toxicity increased as a function of dose to 1.0 kGy. At doses higher than 1.0 kGy the toxicity decreased continuously due to further degradation. It was also demonstrated that the O₂^??/HO₂^? pair has low reactivity in CPL solution.     

Evaluation of γ-radiation on oolong tea odor volatiles

The aim of this study was to evaluate the gamma radiation effects on odor volatiles in oolong tea at doses of 0, 5, 10, 15 and 20 kGy. The volatile organic compounds were extracted by hydrodistillation and analyzed by GC/MS. The irradiation has a large influence on oolong tea odor profile, once it was identified 40% of new compounds after this process, the 5 kGy and 20 kGy were the doses that degraded more volatiles found naturally in this kind of tea and the dose of 10 kGy was the dose that formed more new compounds. Statistical difference was found between the 5 kGy and 15 kGy volatile profiles, however the sensorial analysis showed that the irradiation at dose up 20 kGy did not interfere on consumer perception.     

A voltammetric study of the binding of copper(II) to peptide fragments of prion

Binding of copper to three peptide fragments of prion (Cu²⁺ binding sites: 60–91, 92–96 and 180–193 amino acid residues) was investigated by anodic stripping voltammetry to determine the stoichiometries of Cu²⁺-prion peptide interactions. The method relies on the synthesis of N-terminally acetylated/C-terminally amidated peptide fragments of prion by solid-phase synthesis and direct monitoring of the oxidation current of copper in the absence and presence of each prion fragment. Titration curves of Cu²⁺ with Ac-PHGGGWGQ-NH₂, Ac-GGGTH-NH₂ and Ac-VNITKQHTVTTTT-NH₂ were obtained in concentrations ranging from 8.52 × 10^?7 to 5.08 × 10^?6, 3.95 × 10^?7 to 1.94 × 10^?6 and 7.82 × 10^?8 to 4.51 × 10^?7 M, respectively. The acquired data were used to calculate the stoichiometries (one peptide per Cu²⁺ ion for all the three studied systems) and apparent dissociation constants (K_d = 4.37 × 10^?8–3.50 × 10^?10 M) for the three complexes.     

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.