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A selection of charged water-soluble phthalocyanines was employed for the photocatalytic oxidation of 2-mercaptoethanol in aqueous alkaline solution in the presence of oppositely charged detergents. Most efficient are Zn(I1) and Al(II1) phthalocyaninetetrasulfonic acids, which oxidize the thiolate to the sulfonic acid and sulfate, whereas Co(I1)phthalocyaninetetrasulfonic acid does not exhibit a photoeffect. During the photooxidation reactions, decomposition (photobleaching) of the zinc phthalocyanine derivatives occurs, whereas the analogous alumina chelates are more stable. Covalent binding of Zn(I1)phthalocyanine derivatives to silica carriers results in photocatalytic activities even in the absence of detergents, since the immobilization of the complexes preserves the required monomeric state. Moreover, the photodecomposition (bleaching) of the heterogenized complexes is strongly retarded. For the photooxidations mainly the pathway via the sensitized formation of singlet oxygen with subsequent oxidation reactions is valid. Hydrogen peroxide as one reduction product of oxygen was found.

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Ru(bpy)3 2+ (bpy ≡ bipyridine) and Ru(o-phen)3 2+ (o-phen ≡ o-phenanthroline) have been adsorbed to a membrane layer made of TiO2 nanocrystallites from aqueous solutions at pH 2.5 by means of pretreatment of the surface with Nafion, sodium dodecyl sulfate (SDS) or sodium dodecyl benzyl sulfate (SDBS). Pulsed laser-induced emission and absorbance changes have been studied. The time profiles provide information concerning environmental effects (charge and hydrophobic interactions) on the rates and yields of electron injection from the excited dyes to the TiO2 membrane and subsequent electron recapture by Ru(III). The differences between the rates of electron injection and recapture, the multiexponential nature of these reactions, and the differences between specific photosensitizers and binders are discussed in light of the semiconducting properties of the TiO2 nanocrystallites and the hydrophobic and ionic interactions between the photosensitizers and the binders. Oxidation of iodide ions by Ru(III) was also studied. Iodide ions react efficiently with Ru(III) despite the negative charge of the binders, indicating that most of the charge is neutralized by the surface charge of TiO2 and by the Ru(III) ions. Quantum yields for net electron injection were determined from the initial (extrapolated) bleaching. In most systems observed bleaching corresponds to 30−80% of the absorbed photons. At relatively high laser pulse intensities, emission measurements show that bimolecular (and apparent higher order) processes take place, involving fast triplet annihilation. A detailed mechanism provides quantitative kinetic treatment of the data. Comparison of results in dry and wet layers indicates that energy migration is responsible for the enhanced triplet annihilation.

The emergence of technologies operating at the nanometer scale for applications as varied as nano-fabrication and super-resolution microscopy has driven the need for ever more accurate spatial localization. In this context, nano-structures have been used as 1 probes in order to provide a reference to track lateral drifts in the system. Yet nanometer precision remains challenging and usually involves complicated measurement apparatus. In this work we report a simple method based on symmetry considerations to measure the position of a sub-wavelength nano-structure. For a particular choice of structures, gold nano-particles, we demonstrate a sub-nanometer lateral precision of 0.55 nm. The versatility of the method also allows for the use of different structures, offering a promising opportunity for sub-nanometer positioning accuracy for a wide variety of systems.

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This experiment involves a titrimetric determination of the oxidation states of molybdenum.