Reductive Photodegradation of 4,4'-Isopropylidenebis(2,6-dibromophenol) on Fe3O4 Surface.

BACKGROUND: Advanced Oxidation Processes (AOPs) are the water treatment techniques that are commonly used forthe decomposition of the non-biodegradable organic pollutants. However, some pollutants are electron deficient and thus resistant to attack by reactive oxygen species (e.g., polyhalogenated compounds) but they may be degraded under reductive conditions. Therefore, reductive methods are alternative or supplementary methods to the well-known oxidative degradation ones. METHODS: In this paper, the degradation of 4,4'-isopropylidenebis(2,6-dibromophenol) (TBBPA, tetrabromobisphenol A) using two Fe3O4 magnetic photocatalyst (F1 and F2) is presented. The morphological, structural and surface properties of catalysts were studied. Their catalytic efficiency was evaluated based on reactions under reductive and oxidative conditions. Quantum chemical calculations were used to analyse early steps of degradation mechanism. RESULTS: The studied photocatalytic degradation reactions undergo pseudo-first order kinetics. The photocatalytic reduction process follows the Eley-Rideal mechanism rather than the commonly used Langmuir-Hinshelwood mechanism. CONCLUSIONS: The study confirms that both magnetic photocatalyst are effective and assure reductive degradation of TBBPA.

High energy radiation - Induced cooperative reductive/oxidative mechanism of perfluorooctanoate anion (PFOA) decomposition in aqueous solution.

The mechanism of high-energy radiation induced degradation of perfluorooctanoate anion (PFOA, C7F15COO-) was investigated in aqueous solutions. Identification and quantification of transient species was performed by pulse radiolysis and of final products by gas and ion chromatography, electrochemical method using fluoride ion-selective electrode and ESI-MS after γ-radiolysis. Experimental data were further supported by kinetic simulations and quantum mechanical calculations. Radiation induced degradation of PFOA includes as a primary step one-electron reduction of PFOA by hydrated electrons (e-aq) resulting in formation of [C7F15COO-]●-. The rate constants of this reaction were found to be in the range 7.7 × 107-1.3 × 108 M-1s-1 for ionic strength of the solutions in the range 0.01-0.1 M and were independent of pH of the solutions. At pH > 11 [C7F15COO-]●- tends to defluorination whereas at lower pH undergoes protonation forming [C7F15COOH]•-. A sequence of consecutive reactions involving [C7F15COOH]•- leads to PFOA regeneration what explains a high radiation resistance of PFOA at moderately acidic solutions. A simultaneous presence of oxidizing transient species (●OH) in the irradiated system enhanced decomposition of (C7F14)·COO- as well as [C7F15COOH]•-. The key steps in this complex radical mechanism are the reactions of both these radical anions with ●OH leading to semi-stable products which further undergo consecutive thermal reactions. On the other hand, direct reactions of PFOA with ●OH and ●H were found to be relatively slow (7 × 103 and <4 × 107 M-1s-1, respectively) and do not play relevant role in PFOA degradation. Collected for the first time results, such as dependence of selected reaction rate constants and selected products radiation chemical yields on pH as well as finding of several semi-stable products, missing in previous studies, indicate incompleteness of published earlier reaction pathways of PFOA degradation. The presented overall mechanism explains experimental results and verifies previously suggested mechanisms found in the literature.

Sterilization of Semiconductive Nanomaterials: The Case of Water-Suspended Poly-3-Hexylthiophene Nanoparticles.

In this work, the feasibility of sterilizing a water suspension of poly-3-hexylthiophene nanoparticles (P3HT-NPs) is investigated using ionizing radiation, either γ-rays or high-energy electrons (e-beam). It is found that regardless of the irradiation source, the size, polydispersity, aggregation stability, and morphology of the NPs are not affected by the treatment. Furthermore, the impact of ionizing radiation on the physicochemical properties of NPs at different absorbed radiation doses (10-25 kGy) and dose rates (kGy time-1 ) is evaluated through different spectroscopic techniques. The results indicate that delivering a high dose of radiations (25 kGy) at a high dose rate, that is, kGy s-1 , as achieved by e-beam irradiation, preserves the characteristics of the polymeric NPs. Differently, the same radiation dose but delivered at a lower dose rate, that is, kGy h-1 , as attained by using a γ-source, can modify the physicochemical properties of the polymer. Sterility tests indicate that an absorbed dose of 10 kGy, delivered either with γ-rays or e-beam, is already sufficient for effective sterilization of the colloidal suspension and for reducing the endotoxin content. Finally, NPs irradiated at different doses, exhibit the same cytocompatibility and cell internalization characteristics in human neuroblastoma SH-SY5Y cells of NPs prepared under aseptic conditions.

New Insights into the Reaction Paths of Hydroxyl Radicals with Purine Moieties in DNA and Double-Stranded Oligodeoxynucleotides.

The reaction of hydroxyl radical (HO•) with DNA produces many primary reactive species and many lesions as final products. In this study, we have examined the optical spectra of intermediate species derived from the reaction of HO• with a variety of single- and double-stranded oligodeoxynucleotides and ct-DNA in the range of 1 µs to 1 ms by pulse radiolysis using an Intensified Charged Coupled Device (ICCD) camera. Moreover, we applied our published analytical protocol based on an LC-MS/MS system with isotopomeric internal standards to enable accurate and precise measurements of purine lesion formation. In particular, the simultaneous measurement of the four purine 5',8-cyclo-2'-deoxynucleosides (cPu) and two 8-oxo-7,8-dihydro-2'-deoxypurine (8-oxo-Pu) was obtained upon reaction of genetic material with HO• radicals generated either by γ-radiolysis or Fenton-type reactions. Our results contributed to the debate in the literature regarding absolute level of lesions, method of HO• radical generation, 5'R/5'S diastereomeric ratio in cPu, and relative abundance between cPu and 8-oxo-Pu.

Spectral and Kinetic Study of 3-Styrylquinoxalin-2(1 H)-ones Photoreduced by N-Phenylglycine and Amines.

The photoreduction by amines and N-phenylglycine, NPG, of six styrylquinoxalin-2(1 H)-ones derivatives substituted in the styryl moiety, R-SQ, was studied by using flash photolysis. The photoreaction is initiated via a single electron transfer from the electron donor (amines or NPG) to R-SQ excited triplet state, 3R-SQ*, with the formation of a triplet state radical ion pair or a charge transfer exciplex, 3[CRIP/CTE]. These species live longer than the respective 3R-SQ* and have very similar transient spectra. In the presence of NPG, these 3[CRIP/CTE] evolve on µs time scale to the respective hydrogenated radicals, R-SQH•, whose transient spectra and reaction rate constants with NPG are reported. The identity of these hydrogenated radicals was supported by the spectra obtained with the α-H donor triethylamine and previous pulse radiolysis studies in 2-propanol. Our findings allow proposing a radical chain reaction mechanism that explains the observed spectral behavior and rationalizes formation of the main product formed by binding of four PhNHCH2• derived from NPG decarboxylation.

A survey of analytical methods employed for monitoring of Advanced Oxidation/Reduction Processes for decomposition of selected perfluorinated environmental pollutants.

The monitoring of Advanced Oxidation/Reduction Processes (AO/RPs) for the evaluation of the yield and mechanisms of decomposition of perfluorinated compounds (PFCs) is often a more difficult task than their determination in the environmental, biological or food samples with complex matrices. This is mostly due to the formation of hundreds, or even thousands, of both intermediate and final products. The considered AO/RPs, involving free radical reactions, include photolytic and photocatalytic processes, Fenton reactions, sonolysis, ozonation, application of ionizing radiation and several wet oxidation processes. The main attention is paid to the most commonly occurring PFCs in the environment, namely PFOA and PFOS. The most powerful and widely exploited method for this purpose is without a doubt LC/MS/MS, which allows the identification and trace quantitation of all species with detectability and resolution power depending on the particular instrumental configurations. The GC/MS is often employed for the monitoring of volatile fluorocarbons, confirming the formation of radicals in the processes of C‒C and C‒S bonds cleavage. For the direct monitoring of radicals participating in the reactions of PFCs decomposition, the molecular spectrophotometry is employed, especially electron paramagnetic resonance (EPR). The UV/Vis spectrophotometry as a detection method is of special importance in the evaluation of kinetics of radical reactions with the use of pulse radiolysis methods. The most commonly employed for the determination of the yield of mineralization of PFCs is ion-chromatography, but there is also potentiometry with ion-selective electrode and the measurements of general parameters such as Total Organic Carbon and Total Organic Fluoride. The presented review is based on about 100 original papers published in both analytical and environmental journals.

Hierarchical Growth of Supramolecular Structures Driven by Pimerization of Tetrahedrally Arranged Bipyridinium Units.

A shape-persistent molecule, featuring four bipyridinium units, has been synthesized that upon reduction undergoes intermolecular pimerization because of the rigid architecture of the molecule. The pimerization process has been investigated by a variety of techniques, such as absorption measurements, EPR spectroscopy, as well as gamma and pulse radiolysis, and compared with the behavior of a model compound. Computational studies have also been performed to support the experimental data. The most interesting feature of the tetramer is that pimerization occurs only above a threshold concentration of monoreduced species, on the contrary to the model compound. Furthermore, there is an increase of the apparent pimerization constant by increasing the concentration of reduced bipyridinium units. These results have been interpreted by the fact that pimerization is favored in the tetrahedrally shaped molecule because of a cooperative mechanism. Each multiply reduced molecule can indeed undergo multiple intermolecular interactions that enhance the stabilization of the system, also leading to hierarchical supramolecular growth. The resulting supramolecular system formed by such intermolecular pimerization should exhibit a diamond-like structure, as suggested by a simplified modeling approach. The intermolecular nature of the pimerization process occurring in the tetramer has been demonstrated by measuring the corresponding bimolecular rate constant by pulsed radiolysis experiments.

Application of Radiation Chemistry to Some Selected Technological Issues Related to the Development of Nuclear Energy.

The most important contributions of radiation chemistry to some selected technological issues related to water-cooled reactors, reprocessing of spent nuclear fuel and high-level radioactive wastes, and fuel evolution during final radioactive waste disposal are highlighted. Chemical reactions occurring at the operating temperatures and pressures of reactors and involving primary transients and stable products from water radiolysis are presented and discussed in terms of the kinetic parameters and radiation chemical yields. The knowledge of these parameters is essential since they serve as input data to the models of water radiolysis in the primary loop of light water reactors and super critical water reactors. Selected features of water radiolysis in heterogeneous systems, such as aqueous nanoparticle suspensions and slurries, ceramic oxides surfaces, nanoporous, and cement-based materials, are discussed. They are of particular concern in the primary cooling loops in nuclear reactors and long-term storage of nuclear waste in geological repositories. This also includes radiation-induced processes related to corrosion of cladding materials and copper-coated iron canisters, dissolution of spent nuclear fuel, and changes of bentonite clays properties. Radiation-induced processes affecting stability of solvents and solvent extraction ligands as well oxidation states of actinide metal ions during recycling of the spent nuclear fuel are also briefly summarized.

Radiation stability of cations in ionic liquids. 2. Improved radiation resistance through charge delocalization in 1-benzylpyridinium.

Hydrophobic room-temperature ionic liquids (ILs) hold promise as replacements for molecular diluents for processing of used nuclear fuel as well as for the development of alternative separations processes, provided that the solvent can be made resistant to ionizing radiation. We demonstrate that 1-benzylpyridinium cations are uniquely suited as radiation resistant cations due to the occurrence of charge delocalization in both their reduced and oxidized forms in the ILs. It is suggested that the excess electron and hole in the latter ILs are stabilized through the formation of π-electron sandwich dimers that are analogous to the well-known dimer radical cations of aromatic molecules. This charge delocalization dramatically reduces the yield of fragmentation by deprotonation and the loss of benzyl arms, thereby providing a synthetic path to radiation resistant ILs that are suitable for nuclear fuel processing.

Photoreduction of azaoxoisoaporphines by amines: laser flash and steady-state photolysis and pulse radiolysis studies.

Photoreduction of 7H-benzo[e]perimidin-7-one (3-AOIA, A1) and its 2-methyl derivative (2-Me-3-AOIA, A2) by non-H-donating amines (1,4-diazabicyclo[2.2.2]octane [DABCO]; 2,2,6,6-tetramethylpiperidine [TMP]), and a hydrogen-donating amine (triethylamine [TEA]), has been studied in deaerated neat acetonitrile solutions using laser flash photolysis (LFP) and steady-state photolysis. The triplet excited states of A1 and A2 were characterized by a strong absorption band with λmax = 440 nm and lifetimes of 20 and 27 µs respectively. In the presence of tertiary amines, both triplet excited states were quenched with rate constants close to the diffusional limit (kq ranged between 10(9) and 10(10) M(-1) s(-1)). The transient absorption spectra observed after quenching with DABCO and TMP were characterized by maxima located at 460 nm and broad shoulders in the range of 500-600 nm. These transient species are attributed to solvent-separated radical ion pairs and/or to isolated radical anions. In the presence of TEA, these transients undergo proton transfer, leading to the neutral hydrogenated radicals, protonated over the N1- and O-atoms. Transient absorption spectra of these transients were characterized by maxima located at 400 and 520 nm and 430 nm respectively. Additional support for these spectral assignments was provided by pulse radiolysis (PR) experiments in acetonitrile and 2-propanol solutions.

Electron solvation dynamics and reactivity in ionic liquids observed by picosecond radiolysis techniques.

On time scales of a nanosecond or less, radiolytically-generated excess electrons in ionic liquids undergo solvation processes and reactions that determine all subsequent chemistry and the accumulation of radiolytic damage. Using picosecond pulse radiolysis detection methods, we observed and quantified the solvation response of the electron in 1-methyl-1-butyl-pyrrolidinium bis (trifluoromethylsulfonyl)amide and used it to understand electron scavenging by a typical solute, duroquinone.

Thermostability of glucose oxidase in silica gel obtained by sol-gel method and in solution studied by fluorimetric method.

The thermostability of glucose oxidase entrapped in silica gel obtained by sol-gel method was studied by thermostimulated fluorescence of FAD at pH 5 and 7 and compared with that of the native enzyme in the solution and at the presence of ethanol. The unfolding temperatures were found to be lower for the enzyme immobilised in gel as compared with the native enzyme but higher as for the enzyme at the presence of ethanol. In gel, the thermal denaturation of glucose oxidase is independent on pH while in solution the enzyme is more stable at pH 5. The investigation the enzyme in different environment by steady-state fluorescence of FAD and tryptophan, synchronous fluorescence and time-resolved fluorescence of tryptophan indicates that the state of the molecule (tertiary structure and molecular dynamics) is different in gel and in solution. The ethanol produced during gel precursor hydrolysis is not the main factor influencing the thermostability of the enzyme but more important are interactions of the protein with the gel lattice.

Expression in promoter variant of the ERalpha gene in bos taurus liver.

Due to the variant functions that estrogens play in the regulation of reproduction, development of the mammary gland, growth and differentiation of cells, estrogen receptors and their genes are considered as a candidates for the markers of production and functional traits in farm animals, including cattle. In the earliest study, a 2853-bp bovine ER gene 5'-region was PCR amplified and sequenced. Moreover, for the first time, a polymorphism was described within 5' region of the bovine ERalpha gene--A/G transition lying upstream at position 2591 from acceptor splice site +85, possibly within its promoter--which could be recognized with RFLP-BglI. In other study we are found second polymorphism-A/G transition at position 1213 from acceptor splice site +85, located in promoter for exon B. We have examined the specific mRNA expression of ERalpha in various genotypes using real-time RT-PCR. We used four animals from each genotype group--AG, GG for BglI and AA, AG for SnaBI--to analyse liver ERalpha expression at the level of Real-time PCR. Liver samples were taken from the 16 young Friesian bulls of the different ERalpha genotypes, slaughtered at the local abattoir. As shown by Real-Time PCR, on the livers of animals with different genotype ERalpha mRNA for BglI polymorphism we didn't found variability, but for SnaBI we have found variability between AG and AA genotypes.

Estrogen receptors and their genes--potential markers of functional and production traits of farm animals.

Estrogen receptors, similarly as other nuclear receptors, are transcription factors, which after binding to a proper ligand (17beta-estradiol, estron or estriol) are capable of regulating transcription of target genes. Due to the functions that estrogens play in the regulation of reproduction, development of the mammary gland, growth and differentiation of cells, estrogen receptors and their genes are considered as candidate markers for production and functional traits in farm animals. Known are two isoforms of the estrogen receptor-alpha and beta. They are encoded by separate genes located on different chromosomes. The typical feature of all genes coding for nuclear receptors, including the ER genes, is the complex structure of their 5' regions. In the 5' region of the ERalpha gene of different species are located alternative exons that code for transcripts of different length with different 5'-UTR (untranslated region). The mRNA variants are created by the alternative splicing of the primary transcripts. We sequenced a 2853 bp of the bovine ER gene 5' region, including exons A, B, C and their promoters. Moreover, we found several polymorphic sites, differing by single nucleotide substitutions (SNPs), in the 5' regulatory region and in the coding region of the bovine ERalpha gene.

Tetraalkylphosphonium polyoxometalate ionic liquids: novel, organic-inorganic hybrid materials.

Pairing of a Keggin or Lindqvist polyoxometalate (POM) anion with an appropriate tetraalkylphosphonium cation is shown to yield the first members of a new family of ionic liquids (ILs). Detailed characterization of one of them, an ambient-temperature "liquid POM" comprising the Lindqvist salt of the trihexyl(tetradecyl) phosphonium cation, by voltammetry, viscometry, conductimetry, and thermal analysis indicates that it exhibits conductivity and viscosity comparable to those of the one previously described inorganic-organic POM-IL hybrid but with substantially improved thermal stability.

Tetraalkylphosphonium polyoxometalates: electroactive, "task-specific" ionic liquids.

The pairing of selected polyoxometalate (POM) anions with appropriate tetraalkylphosphonium cations is shown to yield an original family of ionic liquids, among them an ambient-temperature "liquid POM".

Polymorphism within the bovine estrogen receptor-alpha gene 5'-region.

Due to the functions that estrogens play in the regulation of reproduction, development of the mammary gland, growth and differentiation of cells, estrogen receptors and their genes are considered candidates for the markers of production and functional traits in farm animals, including cattle. In the present study, on the basis of the sequences of the human, ovine, and porcine ER genes, available in the GenBank database, sets of PCR primers were designed and used to amplify the bovine ERalpha gene 5'-region. Seven overlapping fragments of the 5' region of the bovine ERalpha gene were amplified and then sequenced. Altogether, these fragments were composed in the 2853-bp sequence which was deposited in the GenBank database under accession no. AY340597. The sequenced fragment included the noncoding exons A, B, C, their putative promoters, and a part of the coding exon 1. A polymorphism within the 5' region of the bovine ERalpha gene-A/G transition, which could be recognized with RFLP-BglI, lying upstream to the exon C, was identified for the first time using this sequence.