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A novel porphyrin dye ZnP-triazine-(gly) 2 , consisting of a zinc-metallated porphyrin unit covalently linked through its peripheral aryl-amino group with a 1,3,5-triazine group which is functionalized by two carboxylic acid groups of glycine moieties, has been synthesized. Photophysical and electrochemical measurements, as well as theoretical DFT calculations, suggest that the compound exhibits appropriate light absorption characteristics and frontier molecular orbital levels for use as sensitizer in dye-sensitized solar cells (DSSCs). The ZnP-triazine-(gly) 2 based solar cell was found to exhibit a power conversion efficiency (PCE) value of 4.72%. A significant improvement of the overall photovoltaic efficiency of the solar cell was achieved up to 7.34% upon co-sensitization with a tertiary aryl-amine D with two ethynyl-pyridine substituents and cyano-acetic acid anchoring group, which exhibits complementary light absorption characteristics with the porphyrin dye. The higher PCE value of the co-sensitized solar cell is attributed to its enhanced short circuit current ( J sc ), which is due to improved light harvesting efficiency, reduced porphyrin aggregation, and faster electron injection and charge collection, as well as its enhanced open circuit voltage ( V oc ), which is due to increased electron density in the TiO 2 conduction band of the photoanode. These results are in accordance with electrochemical impedance spectra (EIS) of the solar cells, which revealed higher charge recombination resistance ( R rec ), longer electron lifetime ( τ e ), and shorter electron transport time ( τ d ) for the co-sensitized solar cell. [ABSTRACT FROM AUTHOR]

Abstract: In-situ UV–visible and EPR Spectroelectrochemistry of a free base porphyrin, 5,10,15,20-tetrakis[3,4-(1,4-dioxan)phenyl]porphyrin, and its zinc derivative, 5,10,15,20-tetrakis[3,4-(1,4-dioxan)phenyl]porphyrinatozinc(II) were performed. On one-electron oxidation of the free base porphyrin in dichloromethane/0.1 M BuN4PF6 using an optically transparent thin layer cell, the initial Soret band retains its intensity and an equally intense new band appears at 453 nm. The initial Q bands disappear, and new bands appear at 516, 555 and 694 nm. At 295 K, it exhibits an isotropic EPR signal with a peak to peak separation of about 6 G and centered at g = 2.004. On one-electron oxidation of the zinc-porphyrin in similar conditions, the Soret band loses its intensity, and a new band appears at 466 nm. The in-situ generated one-electron oxidized species exhibits an isotropic EPR signal at 295 K which is centered at g = 2.0035. The formations of aggregates/self-assemblies of zinc-porphyrin were monitored by UV–vis spectroscopy, fluorescence imaging by confocal microscope, TEM, SEM and DLS measurements. A tentative mechanism has been also proposed for the generation of different aggregates, with varying size and shape, in water–DMF binary mixtures. [Copyright &y& Elsevier]

Abstract: In this work an attempt to obtain a more compact system for gas sensing, designed directly on a transducer, is presented. In the nature, a mucous layer covers the olfactory receptor cells of mammalians and selectively tunes the chemical interactions between odorous molecules and sensing systems. Such natural double layer design was reproduced in this study using a double coating comprised of a proper hydrophobic Teflon-like overlayer tuning the humidity interference between the odorous molecules and the sensitive matrix below consisting of a Zn-porphyrin film. This double coating was applied on both surfaces of the quartz crystal microbalance used for transducing into electrical signals the chemical signals deriving from the adsorption of volatile molecules. [Copyright &y& Elsevier]