Response to high acidity and basicity at a platinum electrode in chronopotentiometry

Highly efficient photocatalytic degradation of methylene blue by PoPD/TiO2 nanocomposite

The poly-o-phenylenediamine (PoPD)/TiO₂ nanocomposite was successfully synthesized via ‘in situ’ oxidative polymerization method. The modified photocatalysts were characterized by BET, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transform infrarad spectra (FT-IR), thermogravimrtic analysis (TGA), X-ray photoelectron spectroscopy (XPS), Ultraviolet-visible diffuse reflectance spectrum (UV-Vis DRS) and Photocurrent Test. The results showed that the PoPD exists on the surface of TiO₂, the presence of PoPD does not impact on the lattice structure and grain size of TiO₂, and the presence of PoPD enhances the visible response and photoelectric property. The photocatalytic degradation of methylene blue (MB) was chosen as a model reaction to evaluate the photocatalytic activities of TiO₂ and PoPD/TiO₂. The optimal preparation condition was the molar ratio of oPD to TiO₂ = 3:1, HCl concentration = 1.2 mol/L, the molar ratio of APS to oPD = 1:1. The apparent first-order rate constant k_app of PoPD/TiO₂ nanocomposite was 0.0098 min^-1, which is 6 times higher than TiO₂ (0.0016 min^-1). Meanwhile, the PoPD/TiO₂ nanocomposites showed excellent photocatalytic stability, and the photocatalytic stability was depended on the stability of structure. At last, the photocatalytic mechanism of POPD/TiO₂ nanocomposites was also proposed based on the synergetic effect between TiO₂ and PoPD.

Optical Sensors for the Determination of Concentrated Hydroxide. Characterization of the Sensor Materials and Evaluation of the Sensor Performance

Optical sensors for the determination of highly concentrated bases such as NaOH (1-10 M) and materials to make these sensors have been characterized by X-ray photoelectron spectroscopy, 29Si solid-state NMR, FT-IR, and measurements of film porosity, surface area, and thickness. The bonding character and composition of the Si-Zr mixed oxides-organic polymer composites were evaluated. These studies suggest that there are Si-O-Zr matrixes in the mixed oxides, and that the Si-O-Zr matrixes contribute to the durability of the base sensors in highly alkaline solutions. The performance of these base sensors has been studied in detail as well. These sensors were stable for approximately 120 days, exhibited short response times (typically <10 s), and were fully reversible with minimal hysteresis effects in NaOH-ROH-H2O solutions (R = Me, Et, and i-Pr).