Irradiation of aqueous solutions

The irradiation of aqueous solutions of 2,4-dichlorophenol and 2,4,5-trichlorophenol with UV light at wavelengths above 280 nm gave little... 

Fig. 9 Epifluorescence microscopy images of the amyloid fibrils of PrP 90-231 (1 pM), stained at room temperature with (a) ThT alone (10 pM) (exposure time 1.6 s), and (b) with preformed ThT-Ag clusters (exposure time 0.02 s). ThT-Ag clusters were preformed by irradiation of aqueous solutions of ThT (10 pM)/AgN03 (1 pM) at 312 nm for 3 min. Scale bars = 10 pm. (c) Photobleaching kinetics of the fibrils stained with ThT (black line) vs. photoactivation kinetics of the fibrils stained with ThT-Ag clusters (red line). Data collected from a 5 pm x 5 pm area and normalized to the intensity measured at zero time [31 ]...

Vacuum UV irradiation of aqueous solutions containing formate is one of the methods to generate CO2 . Under such conditions, the carbon dioxide anion-radical is formed in the excited state. The excited anion-radical transfers an unpaired electron to nitrobenzene, benzoic acid, or benzal-dehyde (Rosso et al. 2000). 

Table 2. Synthesis conditions and equilibrium swelling degrees of PVME gels made by -/-irradiation of aqueous solutions containing 30 wt % PVME and 15 wt % ferric oxide. Reprinted from Polymer (1991) 33 990 by permission of the publishers, Butterworth Heinemann [46]...

The discovery of the hydrated electron in irradiated aqueous solutions has made it necessary to re-examine the mechanisms proposed for the irradiation of aqueous solutions of substances which are biologically important. The new technique of pulse radiolysis has provided a breakthrough in many ways, particularly in determining absolute rate constants. These advances have made it possible to begin working out the reactivity of solvated electrons in vivo, although it is not yet possible to specify the precise role of the reactions in radiation biology. 

Ultrasonic irradiation of aqueous solutions of the chlorophenols was carried out with a Vibra Cell Model VC-250 direct immersion ultrasonic horn (Sonics Materials Newtown, CT) operated at a frequency of 20 kHz with a constant power output of 50 W (the actual insonation power at the solution was 49.5 W, and the power density was 52.1 W/cm2). Reactions were done in a glass sonication cell (4.4 cm i.d. by 10 cm), similar to the one described by Suslick (1988). The temporal course of the sonochemical processes was monitored by HPLC. 

The ultrasonic irradiation of aqueous solution of PNP was carried out with a Branson 200 sonifier that was operated at 20 KHz and with an output of electrical power of 84 W. Reactions were performed in a stainless-steel, continuous-flow reaction cell operated in the batch mode. All reactions were carried out with air-saturated solutions, and the concentration of p-benzo-quinone (p-BQ) was determined spectrophotometrically. Hydrogen peroxide... 

The proposed reaction mechanism for the destruction of aqueous solutions of TCE or PCE predicts the formation of stable oxidized polar organic compounds. These compounds consist of acids, aldehydes, and possibly halo-acetic acids. Three possible mechanisms have been proposed for the formation of by-products due to the irradiation of aqueous solutions containing TCE and PCE. The first is for the formation of formaldehyde, acetaldehyde, and glyoxal, which are formed at a concentration of approximately two orders of magnitude less than the influent solute concentration. Second, the formation of formic acid decreased with increasing radiation dose. The formic acid concentration was found to be higher for PCE than TCE. These results are most probably due to the slower reaction rate constants of PCE with e and OH, compared to TCE. The third possible reaction is the formation of haloacetic acids when TCE and OH react. The mechanism of decomposition of PCE by OH is shown in Equation (12.30) to Equation... 

Armstrong D, Collinson E, Dainton FS, Donaldson DM, Hayon E, Miller N, Weiss J (1958) Primary products in the irradiation of aqueous solutions with X or gamma rays. Proc 2nd UN Int Conf Peaceful Uses of Atomic Energy 29 80-91... 

Krushinskaya NP (1983) Radiation-induced chemical alterations in sugar moiety of DNA Carbon-carbon bond rupture. In Dobo J, Hedvig P, Schiller R (eds) Proc. 5th Tihany Symp. Radiation Chemistry. Akedemiao Kiado, Budapest, pp 1061-1066 Krushinskaya NP, Shalnov Ml (1967) Nature of breaks in the DNA chain upon irradiation of aqueous solutions. Radiobiology 7 36-45... 

Fig. 5 Spectral changes caused by continuous irradiation of aqueous solutions ofthe Ct form of 4 -methoxyflavylium ion with 365 nm light (a) pH = 1.0, [Ct] = 2.5 x 10 5 Mjthe curves correspond to the following irradiation...

Considerable research has also been reported on the irradiation of aqueous solutions of PCE [15,16,18 21]. Perchloroethylene, at 10 ppm (60 l iM) behaved similarly to TCE, with a lower G value of 0.44 pmol. 1 1 [18], The lower G is expected because of PCE s lower bimolecular rate constant for OI I capture and the slightly lower molar concentration of TCE. The... 

Electron spin resonance observation of organic radicals during in situ radiolysis of solutions was initiated by Fessenden and Schuler (1960) (their major work on hydrocarbon solutions was published in 1963). A review on the e.s.r. spectra of radiation-produced radicals summarizes the literature up to 1968 (Fessenden and Schuler, 1970). However, e.s.r. observation of radicals during irradiation of aqueous solutions was not achieved until 1968 (Eiben and Fessenden, 1968 Avery et al., 1968). 

High-energy irradiation of aqueous solutions of 5,6-dihydroxyindole (136) in the presence of azide ions yields the oxidized product (137) in equilibrium with the quinone (138). Reaction of the quinone (138) with azide leads to the trapped product (139) and subsequently to 6,7-dihydroxy-l,2,3-triazolo[4,5-6]indole (140). It appears that the driving force for this reaction (138)->(140) is the electrocyclic ring closure as the quinone (138) is unreactive towards other nucleophiles (Scheme 11) <92TL3045>. 

Irradiation of aqueous solutions of 1-isobutenyl- and l-propenyl-2-pyridinones containing perchloric acid leads to formation of 2,3-dihydrooxazolo[3,2-a]pyridinium salts. It is suggested that the mechanism involves an initial excited state electrocyclization to generate a pyridinium ylide (255). The latter is rapidly trapped by proton transfer from water. In the absence of perchloric acid the hydroxide counterion acts as a nucleophile and opens the ring to the monocyclic alcohol (256) (79JA3607). 

Photooxidation of solvent water occurs upon irradiation of aqueous solutions of Ce4+ yielding oxygen as a product [100]. 

Synthesis of alloyed silver-palladium bimetallic nanoparticles was achieved by /-irradiation of aqueous solutions containing a mixture of Ag and Pd metal ions using different Ag/Pd ratios. The synthesis of alloys implies the simultaneous radio-induced reduction of silver and palladium ions. The nanoparticles were characterized by UV-visible spectroscopy, transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). The Ag-Pd nanoparticles display a face-centered cubic (fee) crystalline structure. The lattice parameter was measured for several Ag/Pd ratios and was found to closely follow Vegard s law, which indicates the formation of homogeneous alloys. In order to avoid the simultaneous reduction of silver and palladium ions which leads to alloyed bimetallic nanoparticles. 

The intramolecular addition of cysteine thiyl radicals (CysS ) to phenylalanine yielding alkylthio-substituted cyclohexadienyl radicals was observed in Cys-Phe and Phe-Gly-Cys-Gly peptides.CysS radicals were generated by pulse irradiation of aqueous solution containing the respective disuHide-linked peptide [reactions (11)-(14)] ... 

Irradiation of aqueous solutions by ionizing radiation has been found to be a very important and selective method for the generation of ROS and RNS. Interaction of ionizing radiation with dilute aqueous solutions causes excitation and ionization of water molecules which undergo subsequent changes, mainly due to ion-molecule reactions, dissociation reactions, and solvation reactions to produce a number of radical and molecular species [Eq. (18)]. 

Franck and Haber introduced radically new ideas into the field of inorganic kinetics (11). They postulated the formation of OH radicals in the course of the ultraviolet irradiation of aqueous solutions of halides and sulfites and also in the autoxidation of sulfites. At the same time OH radicals were postulated by Urey,... 

The irradiation of aqueous solutions of carbohydrates has the same effect as it does on alcohols. The hydroxyl groups are attacked to yield carbonyl compounds. Under anoxic conditions, dimer products and, ultimately, polymers are also formed. The primary alcohol... 

The precise nature of the chemical changes have been examined in detail for irradiations of aqueous solutions only. Oxygen exerts an important influence on the nature of the products, and, in radiation-chemical studies on carbohydrates, it is therefore essential to maintain either evacuated or oxygenated conditions throughout a particular irradiation. If initially air-equilibrated solutions are used, and no provision is made for re-... 

Amino acids, nucleic acid bases and organic acids were synthesized by the UV irradiation of aqueous solutions in which CO2 and NH3 gases or ammonium carbonate had been dissolved. For the photosyntheses of amino acids and nucleic acid bases, the irradiation of UV hght of wavelengths shorter than 280 nm at temperatures higher than 80 °C and the coexistence of Mg " in the solution were foimd to be effective. Oxahc acid and/or oxamic acid were assiuned to be possible intermediates for the syntheses. 

During ultrasonic irradiation of aqueous solutions, OH radicals are produced from dissociation of water vapor upon collapse of cavitation bubbles. A fraction of these radicals that are initially formed in the gas phase diffuse into solution. Cavitation is a dynamic phenomenon, and the number and location of bursting bubbles at any time cannot be predicted a priori. Nevertheless, the time scale for bubble collapse and rebound is orders of magnitude smaller than the time scale for the macroscopic effects of sonication on chemicals (2) (i.e., nanoseconds to microseconds versus minutes to hours). Therefore, a simplified approach for modeling the liquid-phase chemistry resulting from sonication of a well-mixed solution is to view the OH input into the aqueous phase as continuous and uniform. The implicit assumption in this approach is that the kinetics of the aqueous-phase chemistry are not controlled by diffusion limitations of the substrates reacting with OH. 

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