Photodecomposition of Iron(III) Hydroxo and Sulfato Complexes in Aqueous Solution: Wavelength Dependence of OH and SO4- Quantum Yields

1995 ◽  
Vol 99 (14) ◽  
pp. 5214-5221 ◽  
Author(s):  
Heinz-Juergen Benkelberg ◽  
Peter Warneck
Keyword(s):  
Aqueous Solution ◽  
Wavelength Dependence ◽  
Quantum Yields ◽  
Sulfato Complexes

scholarly journals The behaviour of visual purple at low temperature

1941 ◽  
Vol 179 (977) ◽  
pp. 151-159 ◽  
Keyword(s):  
Aqueous Solution ◽  
Low Temperature ◽  
Low Temperatures ◽  
Room Temperature ◽  
Absorption Curve ◽  
Quantum Yields

Visual purple is soluble and stable in a mixture of glycerol and water (3:1). At room temperature the spectrum of such a solution is identical with that of the aqueous solution. At — 73° C the peak of the absorption curve is higher and narrower than at room temperature, and it is shifted towards longer waves. The product of photodecomposition at — 73° C has a spectrum in ­ dependent of pH and is at low temperatures thermostable and photostable, but at room temperature it decomposes therm ally to indicator yellow. The primary product appears to be identical with transient orange. The quantum yields of the photoreaction at low and at room temperature are of the same order.

Quantum Yields for the Photodegradation of Pollutants in Dilute Aqueous Solution: Phenol, 4-Chlorophenol and N-Nitrosodimethylamine

1996 ◽  
Vol 1 (2) ◽  
Author(s):  
Te-Fu L. Ho ◽  
James R. Bolton ◽  
Ewa Lipczynska-Kochany
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Peroxide ◽  
Quantum Yield ◽  
High Performance ◽  
Flash Photolysis ◽  
Quantum Yields ◽  
Visible Absorption ◽  
Dilute Aqueous Solution ◽  
Uv Visible ◽  
Photolysis Of Phenol

AbstractA broadband method has been applied to determine the quantum yields for the photochemical removal of three common pollutants: phenol, 4-chlorophenol and N-nitrosodimethylamine (NDMA) in dilute aqueous solution. Flash photolysis (xenon flash lamps) was used to cause a significant amount of photolysis without photolyzing intermediates. The analysis of reactant depletion following a single flash was carried out by high- performance liquid chromatography (HPLC) or UV/visible absorption spectroscopy. The method for determining quantum-yields employed p-benzoquinone as an actinometer and was validated by determining the average (200-400 nm) quantum yield for the generation of hydroxyl radicals from the photolysis of hydrogen peroxide (0.90 ± 0.10) and the quantum yields for the photolysis of phenol (0.13 ± 0.02) and 4-chlorophenol (0.24 ± 0.04). The values determined agree very well with the literature ones obtained with monochromatic radiation. The quantum yield for the direct photolysis of NDMA was found to be 0.11 ± 0.03 at neutral pH and 0.27 ± 0.02 at pH 2-4. Under conditions where hydrogen peroxide is the principal absorber, the NDMA quantum yield is 0.32 ± 0.04, independent of pH in the range 2-8.

scholarly journals Laboratory-scale photomineralisation of n-alkanes in aqueous solution, by photocatalytic membranes immobilising titanium dioxide

2005 ◽  
Vol 7 (2) ◽  
pp. 79-85 ◽  
Author(s):  
Ignazio Renato Bellobono ◽  
Franca Morazzoni ◽  
Riccardo Bianchi ◽  
Emilia Simona Mangone ◽  
Rodica Stanescu ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Photocatalytic Oxidation ◽  
Point Of View ◽  
Laboratory Scale ◽  
Kinetic Constants ◽  
Quantum Yields ◽  
Oxidation Of Methane ◽  
Oxygen Donor ◽  
Absorbed Power ◽  
Kinetics Of

Kinetics of photocatalytic oxidation of methane, ethane,n-heptane,n-decane, andn-dodecane, to yield intermediates, and photomineralisation of intermediates, to yield carbon dioxide and water, was studied in aqueous solution, by a laboratory-scale photoreactor and photocatalytic membranes immobilizing30±3wt.% ofTiO2, in the presence of stoichiometric hydrogen peroxide as oxygen donor. The whole volume of irradiated solution was4.000±0.005L, the ratio between this volume and the geometrical apparent surface of the irradiated side of the photocatalytic membrane was3.8±0.1cm, and the absorbed power 0.30W/cm (cylindrical geometry). A kinetic model was used, by which mineralisation of substrate toCO2was supposed to occur, by kinetic constantsk1, through one single intermediate, mediating the behaviour of all the numerous real intermediates formed in the path from the substrate toCO2(kinetic constants of formation of the latter beingk2). A competitive Langmuirian adsorption of both substrate and “intermediate” was also supposed to be operative, as expressed by apparent adsorption constantsk1andk2, possessing a, partly at least, kinetic significance. By Langmuir-Hinshelwood treatment of initial rate data, starting values of thekandKcouples were obtained, from which, by a set of differential equations, the final optimised parameters,k1andk1,k2andK2, were calculated, able fit the whole photomineralisation curve, and not only its initial segment, as the Langmuirian parameters do. The parameters of present work are critically compared with those obtained in two preceding set of studies relative ton-alkanoic acids and ton-alkanols. They are interpreted on the basis of a closer behaviour of hydrocarbons to alkanols, from the photocatalytic point of view, than to carboxylic acids are. Discussion of limiting effective quantum yields, and their comparison with maximum, theoretical values, are also carried out.

scholarly journals Spectral properties and photophysical behaviour of water soluble cationic Mg(II) and Al(III) phthalocyanines

2014 ◽  
Vol 12 (3) ◽  
pp. 403-415 ◽  
Author(s):  
Mopelola Idowu ◽  
Yasin Arslanoğlu ◽  
Tebello Nyokong
Keyword(s):  
Aqueous Solution ◽  
Aqueous Medium ◽  
Spectral Properties ◽  
Photophysical Properties ◽  
Strong Dependence ◽  
Water Soluble ◽  
Quantum Yields ◽  
Fluorescence Lifetimes ◽  
High Solubility ◽  
Medium Ph

AbstractPeripherally and non-peripherally tetrasubstituted-[(N-methyl-2-pyridylthio)]phthalocyaninato magnesium (II) (5 and 6) and chloro aluminium (III) (7 and 8) tetraiodide have been synthesized and characterized. The photophysical properties of the complexes in dimethyl sulfoxide (DMSO) and aqueous medium in the presence and absence of cremophore EL have been studied. These complexes show high solubility in aqueous medium though they were aggregated. The triplet state quantum yields (FT) and the triplet lifetimes (tT) were found to be higher in DMSO with ΦT ranging from 0.32 to 0.51, while tT ranged from 282 to 622 ms in DMSO, compared to aqueous medium (pH 7.4 buffer) where ΦT ranged from 0.15 to 0.19 and tT from 26 to 35 ms. Addition of cremophore EL in aqueous solution resulted in partial disaggregation and increased photoactivity. The fluorescence lifetimes of the complexes showed strong dependence on their immediate environment. The ionic magnesium(II) and aluminium(III) phthalocyanines strongly bind to bovine serum albumin (BSA).

scholarly journals Photoinduced Transformation of Carbon Monoxide in Aqueous Solution

1988 ◽  
Vol 43 (5) ◽  
pp. 430-434
Author(s):  
Hyoung Ryun Park ◽  
Nikola Getoff
Keyword(s):  
Aqueous Solution ◽  
Carbon Monoxide ◽  
Product Formation ◽  
Quantum Yields ◽  
Ph Values ◽  
Probable Reaction Mechanism ◽  
Probable Reaction ◽  
Photoinduced Transformation ◽  
Vacuum Uv Radiation ◽  
Vacuum Uv

Abstract The photoinduced conversion of CO in aqueous solution under the influence of vacuum-uv radiation at λ = 185 nm has been investigated at pH values ranging from 2 to 13. Formaldehyde, glyoxal, carboxylic acids and small amounts of glycol were determined as final products. Initial quantum yields for product formation have been determined. A probable reaction mechanism is presented.

scholarly journals Topochemical control of the photodimerization of aromatic compounds by γ-cyclodextrin thioethers in aqueous solution

2013 ◽  
Vol 9 ◽  
pp. 1858-1866 ◽  
Author(s):  
Hai Ming Wang ◽  
Gerhard Wenz
Keyword(s):  
Aqueous Solution ◽  
Inclusion Complex ◽  
Aromatic Compounds ◽  
Quantitative Yield ◽  
Quantum Yields ◽  
Reaction Conditions ◽  
Salting Out ◽  
Parallel Orientation

The formation of soluble 1:2 complexes within hydrophilic γ-cyclodextrin (γ-CD) thioethers allows to perform photodimerizations of aromatic guests under controlled, homogenous reaction conditions. The quantum yields for unsubstituted anthracene, acenaphthylene, and coumarin complexed in these γ-CD thioethers were found to be up to 10 times higher than in the non-complexed state. The configuration of the photoproduct reflected the configuration of the dimeric inclusion complex of the guest. Anti-parallel orientation of acenaphthylene within the CD cavity led to the exclusive formation of the anti photo-dimer in quantitative yield. Parallel orientation of coumarin within the complex of a CD thioether led to the formation of the syn head-to-head dimer. The degree of complexation of coumarin could be increased by employing the salting out effect.

Article

1999 ◽  
Vol 77 (5-6) ◽  
pp. 868-874
Author(s):  
Maike Fischer ◽  
Yijian Shi ◽  
Bao-ping Zhao ◽  
Victor Snieckus ◽  
Peter Wan
Keyword(s):  
Aqueous Solution ◽  
Vinyl Ether ◽  
Hydroxy Group ◽  
Ground State ◽  
Cycloaddition Reaction ◽  
Quinone Methide ◽  
Quantum Yields ◽  
Ethyl Vinyl Ether ◽  
High Chemical ◽  
Ethyl Vinyl

The photosolvolysis of 1- and 2-hydroxy-9-fluorenols 4-6 has been studied in aqueous solution. All of these 9-fluorenols photosolvolyze efficiently in 1:1 H2O-CH3OH, to give the corresponding methyl ether products in high chemical and quantum yields. Whereas the photosolvolysis of the parent 9-fluorenol (2, R = H) is known to proceed via the very short-lived and formally ground-state antiaromatic 9-fluorenyl cation (1, R = H), the photosolvolysis of 1-hydroxy-9-fluorenol (4) proceeds via a much longer-lived (approximately = 5-10 s) fluorenyl quinone methide 9, which is trappable by ethyl vinyl ether via a [4+2] cycloaddition reaction to give a chroman derivative. Interestingly, 2-hydroxy-9-fluorenol (5) photosolvolyzes via a very short-lived intermediate with similar lifetimes as observed for the 9-fluorenyl cation (1, R = H), although a corresponding fluorenyl quinone methide intermediate is accessible for this compound. This study demonstrates that the mechanism of photosolvolysis of these types of compounds can be dramatically altered when an aryl hydroxy group is present.Key words: photosolvolysis, 9-fluorenyl cation, quinone methide, carbocation, antiaromatic.

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