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Photochemical chemical efficiency

The quantum yields are 0.15-0.21 in ethanol and 0.01-0.02 in an aqueous medium, but in micelles, the quantum yields are five to tenfold increased. The aggregation of these dyes was studied in [53]. The amphiphilic squaraines 4 combine favorable photophysical properties and good solubility in aqueous media and in addition interact efficiently with micelles, and therefore have the potential to be used as NIR fluorescent sensors. However, our own investigations show that aniline-based squaraines lack chemical and photochemical stability when compared to oxo-squaraines with heterocyclic end-groups. [Pg.79]

Khan, S.U.M., Al-Shahry, M., and Ingler W.B., Jr., Efficient photochemical water-splitting by a chemically modified n-Ti02, Science, 297, 2243, 2002. [Pg.280]

The chemical sensitization effect was 0.006 (calculated from the quantum yield of the photochemical transformation of 130 to 131, the yield of 131 obtained with the oxalate/hydrogen peroxide reaction, and the moles of oxalate employed). Higher chemical sensitization efficiencies (about 0.04) were observed when the oxalate/hydrogen-peroxide system was used in the addition of ethyl vinyl ether onto phenanthrene quinone... [Pg.130]

Our goal is the rational design of molecules that have a specific set of properties, generally including efficient emissions, long luminescence t s, simple optical pumping, specific environmental sensitivity, and chemical and photochemical inertness. Unfortunately, some of these aims are mutually antagonistic. [Pg.76]

Photochemical decomposition can also be carried out in the presence of a suspension of photoactive material such as Ti02 where substrate absorption onto the uv activated surface can initiate chemical reactions e. g. the oxidation of sulphides to sul-phones and sulphoxides [37]. This technology has been adapted to the destruction of polychlorobiphenyls (PCB s) in wastewater and is of considerable interest in environmental protection. Using pentachlorophenol as a model substrate in the presence of 0.2 % TiOj uv irradiation is relatively efficient in dechlorination (Tab. 4.5) [38]. When ultrasound is used in conjunction with photolysis, dechlorination is dramatically improved. This improvement is the result of three mechanical effects of sonochemistry namely surface cleaning, particle size reduction and increased mass transport to the powder surface. [Pg.142]

In many cases, a combination of physical, chemical, physico-chemical, and biotechnological treatments may be more efficient than one type of treatment (Table 3). Efficient pretreatment schemes, used prior to biotechnological treatment, include homogenization of sohd wastes in water, chemical oxidation of hydrocarbons by H2O2, ozone, or Fenton s reagent, photochemical oxidation, and preliminary washing of wastes by surfactants. [Pg.148]

Within the kinetic and thermodynamic limitations on the conversion of light energy to chemical energy, I have shown that a reasonable efficiency goal would be 25 - 28% for conversion to electricity and 10 - 13% for storage as chemical energy. Five types of photochemical converters have been defined and described with examples where possible. [Pg.218]


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See also in sourсe #XX -- [ Pg.40 ]




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