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The photoelectrochemical quantification of phenolic compounds such as hydroquinone (HQ) and 4-aminophenol (4-AP) is accomplished by integrating a photoelectrochemical cell into a flow injection analysis (FIA) setup. It is a well-known fact that during the electroanalysis of phenolic compounds, the electrode surface is susceptible to poisoning. However, electrode fouling can be reduced significantly by using the FIA system with periodic washing of the electrode. Reactive oxygen species (ROS), which are generated on the surface of TiO2 under UV light, can oxidize phenolic compounds such as 4-AP. The oxidized form of 4-AP is reduced back at the electrode surface, generating a measurable signal proportional to its concentration. The factors influencing the performance of the sensor, such as flow rate, applied potential for back reduction and pH, are investigated in detail. In the concentration range 0.0125–1.0 µM, a linear correlation between the photocurrent and the concentration of 4-AP was observed with a sensitivity of 0.6 A M−1 cm−2 and a limit of detection of 18 nM. A straightforward analytical methodology for the on-site, highly sensitive and low-cost quantification of phenolic compounds is presented, based on the use of TiO2 in a photoelectrochemical flow cell.

Abstract: The present work reports on enzyme attachment on and photoinduced release from TiO2 surfaces. TiO2 layers (amorphous and anatase) were modified with 3-aminopropyltriethoxysilane (APTES), followed by attachment of vitamin C and horseradish peroxidase (HRP). Using step by step XPS characterization and vis-spectroscopy we show that upon UV illumination the linker chain to the protein can be cut, releasing active HRP into the environment. The head silane group remains attached to the TiO2 surface. The kinetics of this photoinduced release is significantly faster for the anatase form of TiO2 compared with amorphous material. The results indicate that UV induced chain scission represents a very versatile tool for payload release from TiO2 surfaces. [Copyright &y& Elsevier]

Abstract: We report an improved performance of Pt–TiO2 nanostructure electrode for methanol oxidation in methanol fuel cells. The nanostructure electrode consisting of Pt nanophases and a titanium oxide matrix was fabricated by means of co-sputtering deposition method. The electrode showed a remarkably enhanced performance for methanol oxidation under UV illumination compared to that without UV illumination. Such a remarkably improved performance of the Pt–TiO2 electrode might be due to the enhanced methanol oxidation by photo-generated holes in the TiO2 under UV illumination. [Copyright &y& Elsevier]