Dosimetry characteristics of the nitro blue tetrazolium-polyvinylalcohol film for high dose applications

The dosimetry characteristics of a polyvinylalcohol based radiochromic dye film containing the ditetrazolium salt nitro blue tetrazolium chloride were studied with respect to the potential use of the films for routine dosimetry in radiation processing. The useful dose range for the dosimeter film for gamma and electron irradiation is 5–50 kGy depending on the concentration of the dye. The effects of irradiation temperature and humidity, as well as the stability of the response of the film before and after irradiation, were investigated and determined. Formulations for preparation of the films with different concentrations of the dye and with different pH were tested. The films were also tested in industrial gamma irradiation facilities for process control purposes by comparing their performance with transfer standard dosimeters.     

Calcined ZnTi-Layered Double Hydroxide Intercalated with H3PW12O40 with Efficiently Photocatalytic and Adsorption Performances

Wastewater treatment is of great significance to environmental remediation. The exploration of efficient and stable methods for wastewater treatment is still a challenging issue. Herein, a heterojunction material with photocatalysis and adsorption properties has been designed to remove the complex pollutants from wastewater. The heterojunction material (ZnO/TiO₂−PW₁₂, PW₁₂=[PW₁₂O₄₀]³⁻) was synthesized by calcining the ZnTi−layered double hydroxide (ZnTi-LDH) intercalated with the Keggin-type polyoxometalate H₃PW₁₂O₄₀. In the construction of ZnO/TiO₂−PW₁₂ it was found that the polyanionic PW₁₂ remained unchanged in the process of forming the proposed heterojunction. The photochemical properties verify that heterojunction synergistic with PW₁₂ facilitated the separation of photoproduced electron-hole pairs and thus suppressed the recombination. Therefore, ZnO/TiO₂−PW₁₂ exhibits excellent photocatalytic property, and the efficiency of Cr(VI) photoreduction reached more than 90 % in the first 3 min. Furthermore, the electrostatic force between the PW₁₂ and cationic dyes makes ZnO/TiO₂−PW₁₂ having an outstanding adsorption performance for cationic dyes, such as rhodamine B, crystal violet and methyl blue. Such heterojunction material combined with polyoxometalate puts forward new insights for the design of functional materials for water treatment with low cost and high efficiency.     

Impregnation of tungstophosphoric acid on poly(methacrylamide-co-methyl methacrylate) and its acid catalytic activity in TMB alkylation

A poly(methacrylamide-co-methylmethacrylate) (abbreviated PMAA-MMA) polymer support was studied for supporting a heteropolyacid (tungstophosphoric acid, H₃PW₁₂O₄₀) with its surface positively charged in the polymerization step. PMAA-MMA supports could be obtained in a porous form by eliminating template reagent molecules (benzylmalonic acid) combined with properly selected monomer (methacrylamide). The amount of amine groups in PMAA-MMA directly determined the amount of H₃PW₁₂O₄₀ impregnated, because the amine groups induced a positive charge on the PMAA-MMA surface. Finally, H₃PW₁₂O₄₀/PMAA-MMA showed better acid catalytic activities than unsupported H₃PW₁₂O₄₀ in alkylation of 1,3,5-trimethylbenzene with cyclohexene, which confirmed that PMAA-MMA supported H₃PW₁₂O₄₀ effectively.     

Synthesis, characterization and photocatalytic application of H3PW12O40/BiVO4 composite photocatalyst

A series of H3PW12O40/BiVO4 composite with different H3PW12O40 loadings were prepared using a hydrothermal and impregnation method. The prepared composites were characterized by XRD, Raman, SEM, XPS, and DRS techniques. The bandgap of the composite was narrower compared with the as-prepared pure BiVO4 . As a novel photocatalytic material, the photocatalytic performance of the H3PW12O40/BiVO4 composite was investigated by the degradation of methylene blue (MB) dye solution under visible light irradiation and compared with that of pure BiVO4 . The results revealed that the introduction of H3PW12O40 could improve the photocatalytic performance and different concentrations of H3PW12O40 resulted in different photocatalytic activities. The highest activity was obtained by the sample with a loading HPW concentration of 10 wt%. The reason for the enhanced photocatalytic activities of H3PW12O40/BiVO4 samples was also discussed in this paper. Moreover, the H3PW12O40/BiVO4 composites retained the catalytic activity after four repeated experiments.     

Epoxidation of cycloolefins with hydrogen peroxide in the presence of heteropoly acids combined with phase transfer catalyst

Oxidation of cycloolefins (cyclohexene, cyclooctene, and cyclododecene) with a 30% solution of hydrogen peroxide at 65 °C in the presence of heteropoly acids (HPA) H₃PW_12–x Mo _x O₄₀ (x = 0—12), which are precursors of active peroxo complexes, and phase transfer catalysts Q⁺Cl^–, where Q⁺ is the quaternary ammonium cation containing C₄—C₁₈ alkyl groups or [C₅H₅NC₁₆H₃₃]⁺, was studied. The catalytic activity decreases in the HPA series: H₃PW₁₂O₄₀ > H₃PW₉Mo₃O₄₀ > H₃PW₆Mo₆O₄₀ > H₃PW₃Mo₉O₄₀ > H₃PMo₁₂O₄₀. The state of the H₃PW₁₂O₄₀—I₂I₂ system was studied using UV, IR, and ³¹P NMR spectroscopies with variation of the [H₂O₂] : [HPA] ratio from 2 to 200 during cyclohexene epoxidation. Despite different catalytic precursors, the reaction proceeds through the same peroxo complex.     

Catalytic Decomposition of Lignin Model Compounds to Aromatics over Acidic Catalysts

Recent progress on the catalytic decomposition of lignin model compounds to aromatics was reported in this review. Cesium-exchanged heteropolyacid catalysts (Cs_xH_3.0?xPW₁₂O₄₀), palladium catalysts supported on cesium-exchanged heteropolyacid (Pd/Cs_xH_3.0?xPW₁₂O₄₀), and palladium catalysts supported on various activated carbon aerogels (ACAs) (Pd/ACA-SO₃H (X), Pd/XCs_2.5H_0.5PW₁₂O₄₀/ACA, Pd/Cs_xH_3.0?xPW₁₂O₄₀/ACA, and Pd/Cs_2.5H_0.5PW₁₂O₄₀/ACA-SO₃H) were prepared, and they were employed for the decomposition of C–O bond in lignin to aromatics. Phenethyl phenyl ether, benzyl phenyl ether, and 4-phenoxyphenol were used as dimeric lignin model compounds representing for β-O-4, α-O-4, and 4-O-5 bonds in lignin, respectively. It was observed that Cs_xH_3.0?xPW₁₂O₄₀ and Pd/Cs_xH_3.0?xPW₁₂O₄₀ were highly active for the decomposition of phenethyl phenyl ether and benzyl phenyl ether to aromatics. However, these catalysts showed very low catalytic performance in the decomposition of 4-phenoxyphenol. Palladium catalysts supported on various ACAs (Pd/ACA-SO₃H (X), Pd/XCs_2.5H_0.5PW₁₂O₄₀/ACA, Pd/Cs_xH_3.0?xPW₁₂O₄₀/ACA, and Pd/XCs_2.5H_0.5PW₁₂O₄₀/ACA-SO₃H) were efficient for the decomposition of 4-phenoxyphenol to aromatics. Acidity of the catalysts played a key role in determining the catalytic performance in the decomposition of 4-phenoxyphenol to aromatics.     

Preparation of 1-butyl-3-methylimidazolium dodecatungstophosphate and its catalytic performance for esterification of ethanol and acetic acid

1-Butyl-3-methylimidazolium dodecatungstophosphate catalyst ([bmim]₃PW₁₂O₄₀) with high water tolerance was prepared from 1-butyl-3-methylimidazolium bromide ([bmim]Br) and phosphotungstic acid (H₃PW₁₂O₄₀). The catalyst was characterized by means of Fourier transform infrared spectroscopy, thermogravimetry-differential scanning calorimetry, n-BuNH₂ potentiometric titration, elemental analysis and so on. Its catalytic activity for esterification of ethanol and acetic acid to ethyl acetate was measured. The results show that there were three crystal-water molecules in the [bmim]₃PW₁₂O₄₀ catalyst, and it preserved the primary Keggin structure and acid strength of H₃PW₁₂O₄₀. The acid amount of [bmim]₃PW₁₂O₄₀ catalyst was less than that of H₃PW₁₂O₄₀. The [bmim]₃PW₁₂O₄₀ catalyst exhibited higher catalytic activity and reusability in the esterification of ethanol and acetic acid to ethyl acetate. __________ Translated from Chinese Journal of Catalysis, 2008, 29(7) (in Chinese)     

Direct synthesis of dimethyl carbonate ?from CH3OH AND CO2 by H3PW12O40/CexTi1-xO2 catalyst

Summary Ce_xTi_1-xO₂ and H₃PW₁₂O₄₀/Ce_xTi_1-xO₂ catalysts were prepared using a sol-gel method, and applied to the direct synthesis of dimethyl carbonate from methanol and carbon dioxide. H₃PW₁₂O₄₀/Ce_xTi_1-xO₂ showed a better catalytic performance than the corresponding Ce_xTi_1-xO₂, due to the bifunctional catalysis of Br?nsted acid sites (provided by H₃PW₁₂O₄₀) and base sites (provided by Ce_xTi_1-xO₂). H₃PW₁₂O₄₀/Ce_0.1Ti_0.9O₂ showed the highest catalytic performance among the H₃PW₁₂O₄₀/Ce_xTi_1-xO₂ catalysts.     

Dimethyl phthalate (DMP) degradation in aqueous solution by gamma-irradiation/H<Subscript>2</Subscript>O<Subscript>2</Subscript>

This work includes the applications of radiation processing to decompose dimethyl phthalate (DMP) with gamma and gamma/H₂O₂ processes. Changes in amounts of DMP, dissolved oxygen, total acidity and formaldehyde with irradiation dose were followed. The qualitative analysis of the DMP and the intermediates were determined by using a gas chromatography combined to mass spectrometry and ion chromatography. The results indicated that degradation rate of DMP was affected by H₂O₂ concentration, irradiation dose and removal efficiency of 25 mg L^?1 DMP can reach 100% for 1.42 kGy irradiation dose in the concentration of 4.8 mM H₂O₂, respectively.     

Selective Conversion of Cellobiose and Cellulose into Gluconic Acid in Water in the Presence of Oxygen,Catalyzed by Polyoxometalate‐Supported Gold Nanoparticles

Gold nanoparticles loaded onto Keggin‐type insoluble polyoxometalates (Cs_xH_3?xPW₁₂O₄₀) showed superior catalytic performances for the direct conversion of cellobiose into gluconic acid in water in the presence of O₂. The selectivity of Au/Cs_xH_3?xPW₁₂O₄₀ for gluconic acid was significantly higher than those of Au catalysts loaded onto typical metal oxides (e.g., SiO₂, Al₂O₃, and TiO₂), carbon nanotubes, and zeolites (H‐ZSM‐5 and HY). The acidity of polyoxometalates and the mean‐size of the Au nanoparticles were the key factors in the catalytic conversion of cellobiose into gluconic acid. The stronger acidity of polyoxometalates not only favored the conversion of cellobiose but also resulted in higher selectivity of gluconic acid by facilitating desorption and inhibiting its further degradation. On the other hand, the smaller Au nanoparticles accelerated the oxidation of glucose (an intermediate) into gluconic acid, thereby leading to increases both in the conversion of cellobiose and in the selectivity of gluconic acid. The Au/Cs_xH_3?xPW₁₂O₄₀ system also catalyzed the conversion of cellulose into gluconic acid with good efficiency, but it could not be used repeatedly owing to the leaching of a H⁺‐rich hydrophilic moiety over long‐term hydrothermal reactions. We have demonstrated that the combination of H₃PW₁₂O₄₀ and Au/Cs_3.0PW₁₂O₄₀ afforded excellent yields of gluconic acid (about 85 %, 418 K, 11 h), and the deactivation of the recovered H₃PW₁₂O₄₀–Au/Cs_3.0PW₁₂O₄₀ catalyst was not serious during repeated use.     

Electrocatalysis of the hydrogen evolution reaction by nanocomposites of poly(amidoamine)-encapsulated platinum nanoparticles and phosphotungstic acid

Poly(amidoamine) dendrimer (Generation-4) encapsulated platinum nanoparticles (PtNP-PAMAM) were prepared and used to fabricate nanocomposites with Keggin-type phosphotungstic acid (PW₁₂O₄₀³⁻) using a layer by layer electrostatic assembly technique. Indium tin oxide (ITO) electrodes, which were first modified with a monolayer of 3-aminopropyl triethoxysilane (3-APTES), were used as substrates for assembly of the PW₁₂O₄₀³⁻ monolayer. Nanocomposites were then fabricated by depositing PtNP-PAMAM on the monolayer of PW₁₂O₄₀³⁻. The amount of PtNP-PAMAM deposited was controlled by using different concentrations of PtNP-PAMAM diluted in 0.1 M H₂SO₄ solution. The hydrogen evolution reaction (HER) was used to test electrocatalytic activities of these nanocomposite modified electrodes. Modification of ITO|3-APTES with PW₁₂O₄₀³⁻ |PtNP-PAMAM showed significantly higher electrocatalytic activities toward the HER than electrodes modified with either PW₁₂O₄₀³⁻ or PtNP-PAMAM alone. The electrocatalytic activities were found to depend on the composition of PtNP-PAMAM and PW₁₂O₄₀³⁻ on electrode surfaces, which was attributed to an interaction between these species. Heat treatment of ITO|3-APTES|PW₁₂O₄₀³⁻ |PtNP-PAMAM electrodes at 200 °C produced significantly higher electrocatalytic activities, which supported the suggestion of an interaction. Presented at the 4th Baltic conference on Electrochemistry, Griefswald, March 13.−16., 2005.     

Degradation behavior of poly (l-lactide-co-glycolide) films through gamma-ray irradiation

Gamma-ray irradiation is a very useful tool to improve the physicochemical properties of various biodegradable polymers without the use of a heating and crosslinking agent. The purpose of this study was to investigate the degradation behavior of poly (l-lactide-co-glycolide) (PLGA) depending on the applied gamma-ray irradiation doses. PLGA films prepared through a solvent casting method were irradiated with gamma radiation at various irradiation doses. The irradiation was performed using 60Co gamma-ray doses of 25–500 kGy at a dose rate of 10 kGy/h.The degradation of irradiated films was observed through the main chain scission. Exposure to gamma radiation dropped the average molecular weight (M_n and M_w), and weakened the mechanical strength. Thermograms of irradiated film show various changes of thermal properties in accordance with gamma-ray irradiation doses. Gamma-ray irradiation changes the morphology of the surface, and improves the wettability. In conclusion, gamma-ray irradiation will be a useful tool to control the rate of hydrolytic degradation of these PLGA films.     

Effects of different matrixes on the dosimetric response of α-terthiophene films from the kGy to MGy range

Films of polymethylmethacrylate (PMMA) and polystyrene (PS) containing α-terthiophene (3T) undergo a radiochromic effect when exposed to electrons and gamma rays. The films turn either red–green or red, due to the formation of oligomeric radical cations. In both matrixes, absorbance at 465 nm grows linearly with dose when α-terthiophene concentration reaches 12%. Explored range goes up to ∼2×10⁶ Gy, with dose rates spanning over three orders of magnitude. Concerning their application as dosimeters, a higher sensitivity characterises the 3T–PMMA moiety, suggesting its suitability from the kGy range up to 1 MGy. Above this value films become fragile. 3T–PS films are less sensitive, but more radiation resistant. Therefore they better suit the medium-to-high dose dosimetry range. Dose rate influences the response sensitivity in a complex way, however above 80 and up to 3.6×10⁴ Gy/min an approximate linearity exists between log(dose rate) and sensitivity, as in the analogous cellulose triacetate system.     

Acetylation of Alcohols Catalyzed by Dodeca-tungsto(molybdo)phosphoric acid

Summary. Acetylation of primary, secondary, and tertiary alcohols was carried out in some refluxing alkyl acetates and in two carboxylic acids with the participation of catalytic amounts of H₃PW₁₂O₄₀, H₃PMo₁₂O₄₀, and H₁₄P₅W₃₀O₁₁₀ with good yields and high stereo(regio)specificity under mild reaction condition. H₃PW₁₂O₄₀ and H₃PMo₁₂O₄₀ have also shown excellent reactivity in the formylation of 1-butanol with ethyl formate at room temperature and in short reaction times. Heteropolyacid catalysts could be separated after a simple work up and reused for several times.     

Platinized-heteropolycompound-based nanostructured catalysts for low-temperature hydrogen-air fuel cells

Heteropoly acids Cs _x H_{3 − x} PW₁₂O₄₀ · nH₂O with different cesium content are synthesized as nanostructured compositions. Their actual composition and specific surface are determined, microstructure studied and proton conductivity measured. Composite electrocatalytic systems based on platinized cesium salt of phosphorus-tungsten heteropolyacid Cs_2.3H_0.7PW₁₂O₄₀ · nH₂O are prepared with admixture of Vulcan XC-72 carbon black. Mixed electronic-ionic conduction of the composite systems with different carbon black content is studied. Platinum-based nanostructured electrocatalyst based on the Cs_2.3H_0.7PW₁₂O₄₀ · nH₂O-materials as support is synthesized and studied. The possible effective using of the studied nanocomposite as electrode for low-temperature hydrogen-air fuel cells is demonstrated. Electrochemical studies of catalytic properties of the Pt-Cs_2.3H_0.7PW₁₂O₄₀ · nH₂O-C-electrodes in hydrogen and air are carried out by example of the prepared materials with different carbon black content.     

Microwave-promoted efficient conversion of acetophenones to 1,3,5-triarylbenzenes catalyzed by H3PW12O40 and nano-silica supported H3PW12O40 as reusable catalysts

H₃PW₁₂O₄₀ and nano-silica supported H₃PW₁₂O₄₀ were found to be efficient heterogeneous catalysts for the preparation of 1,3,5-triarylbenzenes via triple self condensation of acetophenones under microwave irradiation and solvent-free conditions. High yields, short reaction times, easy work-up, easy availability and handling, eco-friendly and reusability of the catalysts are the main aspects of the present method. The catalytic mechanism of 1,3,5-triarylbenzenes synthesis is also proposed.     

Acidity function of concentrated solutions of 12-tungstophosphoric acid

Conclusions The authors have measured the Hammett acidity functions H₀ of concentrated solutions of H₃PW₁₂O₄₀ in water, aqueous dioxane, and acetic acid. In these solvents the acidity of H₃PW₁₂O₄₀ is higher than those of sulfuric and hydrochloric acids.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 492–493, March, 1982.     

采用溶胶-凝胶-溶剂热路径合成H3PW12O40/TiO2和H4SiW12O40/TiO2 及其光催化降解二硝基甲苯

以非离子表面活性剂P123为结构导向剂,采用溶胶-凝胶与溶解热相结合方法,制备了两类介孔材料H₃PW₁₂O₄₀/TiO₂和H₄SiW₁₂O₄₀/TiO₂,并对其进行了表征.?X射线粉末衍射和拉曼光谱分析表明,所制催化剂为锐钛矿晶型,体系中H₃PW₁₂O₄₀和H₄SiW₁₂O₄₀的Keggin结构经400?℃焙烧后仍保持完整.?H₃PW₁₂O₄₀/TiO₂和H₄SiW₁₂O₄₀/TiO₂的平均粒径分别为15.49和7.75?nm.?N₂吸附-脱附和扫描电镜结果表明,P123的加入使催化剂的粒径减小,比表面积和孔体积明显增大,其中H₃PW₁₂O₄₀/TiO₂和H₄SiW₁₂O₄₀/TiO₂的比表面积分别高达252.2和250.0?m²/g.?紫外漫反射吸收光谱表明,与纯TiO₂相比,复合催化剂的吸收光谱发生了明显的红移,且吸收强度明显增大.?催化剂对DNT降解实验表明,在最佳操作条件下降解率可高达95%.?     

Effect of gamma radiation on the physico-chemical properties of alginate-based films and beads

Alginate solution (3%, w/v) was prepared using deionized water from its powder. Then the solution was exposed to gamma radiation (0.1?25 kGy). The alginate films were prepared by solution casting. It was found that gamma radiation has strong effect on alginate solution. At low doses, mechanical strength of the alginate films improved but after 5 kGy dose, the strength started to decrease. The mechanism of alginate radiolysis in aqueous solution is discussed. Film formation was not possible from alginate solution at doses >5 kGy. The mechanical properties such as puncture strength (PS), puncture deformation (PD), viscoelasticity (Y) coefficient of the un-irradiated films were investigated. The values of PS, PD and Y coefficient of the films were 333 N/mm, 3.20 mm and 27%, respectively. Alginate beads were prepared from 3% alginate solution (w/v) by ionotropic gelation method in 5% CaCl₂ solution. The rate of gel swelling improved in irradiated alginate-based beads at low doses (up to 0.5 kGy).     

Anchoring H3PW12O40 on aminopropylsilanized spinel‐type cobalt oxide (Co3O4‐SiPrNH2/H3PW12O40): A novel nanohybrid adsorbent for removing cationic organic dye pollutants from aqueous solutions

In this work, phosphotungstic acid (H₃PW₁₂O₄₀; PW₁₂) was chemically anchored on aminopropylsiloxane functionalized spherical Co₃O₄ nanoparticles (Co₃O₄–SiPrNH₂) and the resultant nanocomposite (Co₃O₄–SiPrNH₂/PW₁₂) was fully characterized. The results demonstrated successful anchoring of PW₁₂ on the surface of Co₃O₄–SiPrNH₂nanoparticles. The Co₃O₄–SiPrNH₂/PW₁₂ nanohybrid indicated a specific surface area of 42.14 m² g^?1, which was greater than that of pure PW₁₂ (ca. 5 m² g^?1). The adsorption efficiency of this novel adsorbent nanomaterial was evaluated for removing methylene blue (MB), rhodamine B (RhB) and methyl orange (MO) dyes from aqueous solutions. The hybrid nanomaterial exhibited a high adsorption rate and selective adsorptivity for the cationic MB and RhB dyes compared to those for anionic MO dye. The prepared hybrid nanomaterial removed over 98% of MB within 12 min. The effects of initial pH, contact time, adsorbent dosage, and temperature were investigated on the adsorption process. The adsorption capacity of nanohybrid for cationic MB dye was 38.46 mg g^‐1. Also, adsorption kinetics indicated that the adsorption by Co₃O₄–SiPrNH₂/PW₁₂ was well‐modeled using pseudo‐second‐order kinetic model. Finally, thermodynamic parameters revealed that the adsorption was endothermic and spontaneous. The adsorption rate and ability of the Co₃O₄–SiPrNH₂/PW₁₂ were enhanced as compared with Co₃O₄ and Co₃O₄–SiPrNH₂ samples due to enhanced electrostatic attraction intraction. The nanohybride was easily separated and reused without any change in structure. Thus, it could be a promising green adsorbent for removing organic pollutants in water.