Search

A highly uniform nanostructured polypyrrole (PPy) film prepared by a simple, straightforward in situ route of chemical vapor oxidation has been demonstrated as a sensitive substrate for NH3 gas sensing. The structure of PPy film was investigated by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The binding characteristics of the functional groups of the PPy film were examined by Fourier transform infrared and Raman spectroscopy. NH3 sensing properties of the PPy film were evaluated by its resistive response to gas concentrations from 45 to 350 ppm at different temperatures ranging from 25 to 100°C. The sensing response maximum value was 142.6% when exposed to 350 ppm of NH3 gas at room temperature (25°C). The sensing response of PPy film shows an excellent linear relationship and high selectivity toward NH3. The NH3 sensing mechanism is due to the physisorption and chemisorption interactions of NH3 molecules and the adsorptive sites of PPy (polaron and bipolaron charging carriers).

In this work, a photoelectrochemical reactor with an anode based on hybrid structure between conducting polymer polypyrrole (PPy) and porous silicon (PSi) was fabricated and utilized to evaluate the photocatalysis and electro‐assisted photocatalysis for degradation of rhodamine B (RhB) solution. The PSi was made of n‐type silicon single‐crystal wafer by the metal‐assisted chemical etching (MACE). The anode PPy/PSi formed following a polymerization of the PPy on the PSi from the vapour‐phase route using oxidant FeCl3. Typical material characterizations of the PPy, PSi and PPy/PSi were investigated via scanning electron microscope (SEM), and spectroscopies of Fourier‐transform infrared (FTIR), Raman scattering and UV‐vis. Under visible light radiation (halogen light with the wavelength region of 400–700 nm), photocatalytic and electro‐assisted photocatalytic processes of the reactor were conducted by degradation of the RhB solution. A heterojunction (p‐n) of the PPy/PSi was proposed to explain the efficient catalytic performance of the reactor. [ABSTRACT FROM AUTHOR]

Abstract: Yttria-stabilized zirconia (YSZ) ceramic has been well known as a solid electrolyte in electrochemical gas sensors working at high temperature. In this work, YSZ-8 (ZrO2 doped 8mol% Y2O3) powder was synthesized by a sol–gel method. Crystalline structure of the synthesized powder YSZ-8 was analyzed by X-ray diffraction. The impedance spectroscopy investigation showed that the pressed plate YSZ-8 sintered at 1300°C had good ionic conductivity at high working temperature. The gas sensing properties of the mixed potential sensor Pt/YSZ-8/SmFeO3 were investigated by exposing to NO2, CO, CH4, C3H8 and C6H14 at the operating temperatures from 300 to 500°C. The experimental results indicated that the sensor Pt/YSZ-8/SmFeO3 presented very good sensitivity and selectivity to NO2 gas. The high sensitivity of the sensor Pt/YSZ-8/SmFeO3 to NO2 was suggested by relation to high catalytic activity of the oxide SmFeO3 to NO2. [Copyright &y& Elsevier]

Abstract: In this paper, we report the properties of the nano-crystalline oxides LnFeO3 (Ln =La, Nd and Sm) synthesized by sol–gel citrate technique. The crystalline structure of the oxides was analyzed by X-ray diffraction (XRD). The surface morphologies of the LnFeO3 thick-films on Al2O3 substrates were measured by scanning electron microscope (SEM). The gas-sensing characteristics of the oxides LnFeO3 were investigated in methane (CH4), propane (C3H8) and n-hexane (C6H14) gases. All LnFeO3-based sensors exhibited good HC sensing characteristics. The very high n-hexane sensitivities of NdFeO3 and SmFeO3-based sensors were discussed in terms of an important role of rare earth elements. [Copyright &y& Elsevier]