Patima Nizamidin

Room-temperature H 2 S Gas Sensor Based on Au-doped ZnFe 2 O 4 Yolk-shell Microspheres

Room-temperature type H2S sensing devices that use Au-doped ZnFe2O4 yolk-shell microspheres as the active material have been fabricated using a solvothermal method as well as subsequent annealing and a chemical etching process. The samples are characterized using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), field-emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). The results demonstrate that the doping of Au does not change the spinel structure of the products, which were yolk-shell microspheres, while the particle size varied with the Au doping concentration. Also, the as-fabricated sensor device exhibited excellent selectivity toward H2S gas at the room temperature; the gas-sensing property of 2 wt% Au-doped ZnFe2O4 microspheres was the best. The Au-doped ZnFe2O4 yolk-shell microspheres can be promising as a sensing material for H2S gas detecting at room temperature.

Optical Waveguide BTX Gas Sensor Based on Yttrium-Doped Lithium Iron Phosphate Thin Film

Yttrium-doped LiFePO4 powder was synthesized using the hydrothermal method in one step and was used as a sensing material. An optical waveguide (OWG) sensor based on Yttrium-doped LiFePO4 has been developed by spin coating a thin film of LiFe0.99Y0.01PO4 onto a single-mode Tin-diffused glass optical waveguide. Light was coupled into and out of glass OWG employed by a pair of prisms. The guided wave transmits in waveguide layer and passes through the film as an evanescent wave. The sensing film is stable in air, but when exposed to target gas at room temperature, its optical properties such as transmittance (T) and refractive index () were changed; thus, the transmitted light intensity was changed. The LiFe0.99Y0.01PO4 thin film OWG exhibits reversible response to xylene gas in the range of 0.1–1000 ppm. When the concentration of BTX gases was lower than 1ppm, other substances caused a little interference with the detection of xylene vapor. Compared to pure LiFePO4 thin film OWG, this sensor exhibited higher sensitivity to BTXs.

A Functionalized Tetrakis(4-Nitrophenyl)Porphyrin Film Optical Waveguide Sensor for Detection of H2S and Ethanediamine Gases

The detection of hydrogen sulfide (H2S) and ethanediamine, toxic gases that are emitted from industrial processes, is important for health and safety. An optical sensor, based on the absorption spectrum of tetrakis(4-nitrophenyl)porphyrin (TNPP) immobilized in a Nafion membrane (Nf) and deposited onto an optical waveguide glass slide, has been developed for the detection of these gases. Responses to analytes were compared for sensors modified with TNPP and Nf-TNPP composites. Among them, Nf-TNPP exhibited significant responses to H2S and ethanediamine. The analytical performance characteristics of the Nf-TNPP-modified sensor were investigated and the response mechanism is discussed in detail. The sensor exhibited excellent reproducibilities, reversibilities, and selectivities, with detection limits for H2S and ethanediamine of 1 and 10 ppb, respectively, and it is a promising candidate for use in industrial sensing applications.

Characterization of the Optical and Gas Sensitivities of a Nickel-Doped Lithium Iron Phosphate Thin Film

ABSTRACT The influence of heat-treatment temperature on the optical properties (refractive index, transmittance, and attenuation) and gas sensitivities of nickel-doped lithium iron phosphate (LiFe0.99Ni0.01PO4) thin films were discussed. LiFe0.99Ni0.01PO4 was synthesized in one step using hydrothermal methods and fixed to tin-diffused glass as a sensing film by spin-coating before calcination at different temperatures. The obtained thin films were characterized by refractive index, thickness, attenuation, and porosity, as well as gas sensing performances for benzene, toluene, and xylene. The experimental results indicated that the LiFe0.99Ni0.01PO4 thin films dried at 450°C displayed higher refractive indices, good transparency, and less attenuation; thus, the resulting sensor of a LiFe0.99Ni0.01PO4 thin film/tin-diffused optical wave-guide exhibited a greater response to xylene in the concentration range of 0.1–1000 ppm.