Nittaya Tamaekong

Sensing Characteristics of Flame-Spray-Made Pt/ZnO Thick Films as H(2) Gas Sensor.

Hydrogen sensing of thick films of nanoparticles of pristine, 0.2, 1.0 and 2.0 atomic percentage of Pt concentration doped ZnO were investigated. ZnO nanoparticles doped with 0.2–2.0 at.% Pt were successfully produced in a single step by flame spray pyrolysis (FSP) technique using zinc naphthenate and platinum(II) acetylacetonate as precursors dissolved in xylene. The particle properties were analyzed by XRD, BET, SEM and TEM. Under the 5/5 (precursor/oxygen) flame condition, ZnO nanoparticles and nanorods were observed. The crystallite sizes of ZnO spheroidal and hexagonal particles were found to be ranging from 5 to 20 nm while ZnO nanorods were seen to be 5–20 nm wide and 20–40 nm long. ZnO nanoparticles paste composed of ethyl cellulose and terpineol as binder and solvent respectively was coated on Al2O3 substrate interdigitated with gold electrodes to form thin films by spin coating technique. The thin film morphology was analyzed by SEM technique. The gas sensing properties toward hydrogen (H2) was found that the 0.2 at.% Pt/ZnO sensing film showed an optimum H2 sensitivity of ∼164 at hydrogen concentration in air of 1 volume% at 300 °C and a low hydrogen detection limit of 50 ppm at 300 °C operating temperature.

H2 Sensing Response of Flame-Spray-Made Ru/SnO2 Thick Films Fabricated from Spin-Coated Nanoparticles

High specific surface area (SSABET: 141.6 m2/g) SnO2 nanoparticles doped with 0.2–3 wt% Ru were successfully produced in a single step by flame spray pyrolysis (FSP). The phase and crystallite size were analyzed by XRD. The specific surface area (SSABET) of the nanoparticles was measured by nitrogen adsorption (BET analysis). As the Ru concentration increased, the SSABET was found to linearly decrease, while the average BET-equivalent particle diameter (dBET) increased. FSP yielded small Ru particles attached to the surface of the supporting SnO2 nanoparticles, indicating a high SSABET. The morphology and accurate size of the primary particles were further investigated by TEM. The crystallite sizes of the spherical, hexagonal, and rectangular SnO2 particles were in the range of 3–10 nm. SnO2 nanorods were found to range from 3–5 nm in width and 5–20 nm in length. Sensing films were prepared by the spin coating technique. The gas sensing of H2 (500–10,000 ppm) was studied at the operating temperatures ranging from 200–350 °C in presence of dry air. After the sensing tests, the morphology and the cross-section of sensing film were analyzed by SEM and EDS analyses. The 0.2%Ru-dispersed on SnO2 sensing film showed the highest sensitivity and a very fast response time (6 s) compared to a pure SnO2 sensing film, with a highest H2 concentration of 1 vol% at 350 °C and a low H2 detection limit of 500 ppm at 200 °C.

Flame-spray-made undoped zinc oxide films for gas sensing applications.

Using zinc naphthenate dissolved in xylene as a precursor undoped ZnO nanopowders were synthesized by the flame spray pyrolysis technique. The average diameter and length of ZnO spherical and hexagonal particles were in the range of 5 to 20 nm, while ZnO nanorods were found to be 5–20 nm wide and 20–40 nm long, under 5/5 (precursor/oxygen) flame conditions. The gas sensitivity of the undoped ZnO nanopowders towards 50 ppm of NO2, C2H5OH and SO2 were found to be 33, 7 and 3, respectively. The sensors showed a great selectivity towards NO2 at high working temperature (at 300 °C), while small resistance variations were observed for C2H5OH and SO2, respectively.

Ultra-rapid CO gas detection by a gas sensor based on flame-spray-made Pt/ZnO nanoparticles

ZnO nanoparticles doped with 0.2-2 at.%Pt were successfully produced in a single step by flame spray pyrolysis (FSP) technique using zinc naphthenate and platinum (II) acetylacetonate dissolved in xylene. The particle properties were analyzed by XRD, BET and TEM. Depending on FSP conditions, ZnO nanoparticles and nanorods were observed. The crystallite sizes of ZnO spheroidal particles were found to be ranging from 5 to 20 nm, while ZnO nanorods were seen to be 5-20 nm in width and 20-40 nm in length. ZnO sensing films were prepared using Al2O3 substrate interdigitated with Au electrodes by spin-coating technique. The gas sensing properties toward carbon monoxide (CO) was studied at the operating temperatures ranging from 200 to 350°C. It was found that the 0.2 at.%Pt/ZnO sensing film showed the highest sensitivity and the fastest response time at 350°C.

Characterization of Pt-doped WO 3 nanoparticles synthesized by flame spray pyrolysis

Undoped WO3 and WO3 nanoparticles doped with 0.251.0 wt.% Pt were successfully produced in a single step by flame spray pyrolysis (FSP) [. Tungsten (VI) ethoxide 5% w/v in ethanol 99.8% and platinum (II) acetylacetonate were used as W and Pt precursors respectively dissolved in ethanol. The undoped WO3 and Pt-doped WO3 nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The BET surface area (SSABET) of the nanoparticles was measured by nitrogen adsorption. From BET measurement, SSABET increased and dBET decreased with increasing Pt concentration from 0 to 1.0 wt.%. The morphology and accurate size of the primary particles were further investigated by high-resolution transmission electron microscopy (HRTEM). The crystallite size of undoped WO3 spherical was found to be ranging from 520 nm and the crystallite sizes of 0.251.0 wt.% Pt-doped WO3 spherical particles were found to be in the range of 520 nm.