RuO2–IrO2 solid state micro-liquid film pH sensor based on polymeric precursor method

The glass-type electrodes based pH sensors suffer from the weakness of fragility and poor stability in acid/alkali solution. To overcome these disadvantages, a novel solid-state pH sensor based on a RuO2–IrO2 H+ sensitive electrode via a polymeric precursor method was developed in this paper. The electrochemical performance of pH sensor was tested in different conditions. The experimental results showed that the sensitivity of the pH sensor could reach a high level of 52.0 mV/pH in a wide pH range of 2 ∼ 10. Furthermore, the response of pH sensor was fast and the response time remained less than 2.2 s even under varying pH conditions. The experiment was repeated three times during a period of time, the potential difference of pH sensor was between ±0.3 mV and ±0.9 mV in different pH value solutions, demonstrating its good stability, repeatability, recyclability and small potential drift. The negligible interference of Li+, Na+, K+, Ca2+, Mg2+, to the proposed pH sensor was also proven experimentally.

Heterogeneous catalysis for thioanisole oxidation using hydrogen peroxide and Copper, Nickel and Zinc tungstates prepared by the polymeric precursor method

The oxidation of sulfides to sulfoxides and sulfones provides valuable sulfur-containing chemical compounds that are used in the pharmaceutical agrochemical industry. Although some tungsten catalytic systems have been applied to sulfide oxidation, the most desirable heterogeneous catalytic protocols have not been described. The copper, nickel and zinc tungstates powders obtained by the polymeric precursor method and the evaluation of their catalytic activity in thioanisole oxidation were investigated. Thioanisole was oxidized by hydrogen peroxide to sulfoxides and sulfones and the presence of catalyst accelerates the conversion. Of the three catalysts, copper tungstate was the most efficient in the conversion process followed by nickel tungstate and finally zinc tungstate. The copper tungstate has higher hydrogen consumption, indicating a higher oxygen content on the surface and the ability to increase surface mobility, which increases the conversion and selectivity of the process. The addition of 0.1 mL of hydrogen peroxide enhanced the conversion and increased the amount of sulfone produced. The ideal reaction time was 12 hours and the optimum temperature was 75 °C.