Abu Z. Sadek

A layered surface acoustic wave gas sensor based on a polyaniline/In2O3 nanofibre composite

A polyaniline/In2O3 nanofibre composite based layered surface acoustic wave ( SAW) sensor has been developed and investigated for different gases. Chemical oxidative polymerization of aniline in the presence of finely divided In2O3 was employed to synthesize a polyaniline nanofibre/In2O3 nanoparticle composite. The nanocomposite was deposited onto a layered ZnO/64 degrees YX LiNbO3 SAW transducer. The novel sensor was exposed to H-2, NO2 and CO gases. Fast response and recovery times with good repeatability were observed at room temperature.

High-Temperature Anodized WO3 Nanoplatelet Films for Photosensitive Devices

Anodization at elevated temperatures in nitric acid has been used for the production of highly porous and thick tungsten trioxide nanostructured films for photosensitive device applications. The anodization process resulted in platelet crystals with thicknesses of 20-60 nm and lengths of 100-1000 nm. Maximum thicknesses of approximately 2.4 microm were obtained after 4 h of anodization at 20 V. X-ray diffraction analysis revealed that the as-prepared anodized samples contain predominantly hydrated tungstite phases depending on voltage, while films annealed at 400 degrees C for 4 h are predominantly orthorhombic WO3 phase. Photocurrent measurements revealed that the current density of the 2.4 microm nanostructured anodized film was 6 times larger than the nonanodized films. Dye-sensitized solar cells developed using these films produced 0.33 V and 0.65 mA/cm2 in open- and short-circuit conditions.

Anodization of Ti thin film deposited on ITO.

We have investigated several key aspects for the self-organization of nanotubes in RF sputtered titanium (Ti) thin films formed by the anodization process in fluoride-ion-containing neutral electrolytes. Ti films were deposited on indium tin oxide (ITO) glass substrates at room temperature and 300 degrees C, and then anodized. The films were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-vis spectrometry before and after anodization. It was observed that anodization of high temperature deposited films resulted in nanotube type structures with diameters in the range of 10-45 nm for an applied voltage of 5-20 V. In addition, the anatase form of TiO(2) is formed during the anodization process which is also confirmed using photocurrent measurements. However, the anodization of room temperature deposited Ti films resulted in irregular pores or holes.

A room temperature polyaniline nanofiber hydrogen gas sensor

Electro-conductive polyaniline (PANI) nanofiber based surface acoustic wave (SAW) gas sensors have been investigated with hydrogen (H 2) gas. A template-free, rapidly mixed method was employed to synthesize polyaniline nanofibers using chemical oxidative polymerization of aniline. The nanofibers were deposited onto a layered ZnO/64deg YX LiNbO3 SAW transducer for gas sensing applications. The novel sensor was exposed to various concentrations of H2 gas at room temperature. The sensor response, defined as the relative variation in operating frequency of oscillation due to the introduction of the gas, was 3.04 kHz towards a 1% H2 concentration. A relatively fast response time of 8 sec and a recovery time of 60 sec with good repeatability were observed at room temperature. Due to room temperature operation, the novel gas sensor is promising for environmental and industrial applications

ZnO Nanobelt Based Conductometric H2 and NO2 Gas Sensors

Conductometric H2 and NO2 gas sensors based on single-crystalline ZnO nanobelt sensitive layers have been developed. These layers were deposited using a rf magnetron sputterer. TEM and SEM characterization methods were employed to study the morphology of the nanobelts. These sensors were exposed to H2 and NO2 gases at operating temperatures between 225degC and 420degC. Study showed that sensors responded with highest magnitude at above 300degC. The fastest response and recovery times, with greater repeatability occurred at 385degC and 350degC for H2 and NO2 gases, respectively. Sensor with ZnO nanobelts has a much lower optimum operational temperature than that of conductometric sensors with other forms of ZnO crystal layers

Titanium Dioxide-Based YX Surface Acoustic Wave Hydrogen Gas Sensors

Amorphous titanium dioxide () and gold (Au) doped -based surface acoustic wave (SAW) sensors have been investigated as hydrogen gas detectors. The nanocrystal-doped films were synthesized through a sol-gel route, mixing a Ti-butoxide-based solution with diluted colloidal gold nanoparticles. The films were deposited via spin coating onto YX SAW transducers in a helium atmosphere. The SAW gas sensors were operated at various temperatures between 150 and C. It was found that gold doping on increased the device sensitivity and reduced the optimum operating temperature.

A Room Temperature Polyaniline/In2O3 Nanofiber Composite Based Layered ZnO/64° YX LiNbO3 SAW Hydrogen Gas Sensor

A Polyaniline/In₂O₃ nanofiber composite based surface acoustic wave (SAW) gas sensor has been developed. Chemical oxidative polymerization of aniline was employed to synthesize polyaniline nanofibers with lIn₂O₃ nanoparticles. The nanocomposite was deposited onto a layered ZnO/64deg YX LiNbo₃ SAW transducer. The sensor was exposed to various concentrations of H₂ gas and operated at room temperature. The sensor response was found to be 11 kHz towards 1% of H₂ in synthetic air. A fast response and recovery with good repeatability in a stable baseline condition were observed at room temperature.

Energetic deposition of carbon in a cathodic vacuum arc with a biased mesh

Carbon films were deposited in a filtered cathodic vacuum arc with a bias potential applied to a conducting mesh mounted in the plasma stream between the source and the substrate. We determined the stress and microstructural properties of the resulting carbon films and compared the results with those obtained using direct substrate bias with no mesh. Since the relationship between deposition energy and the stress, sp2 fraction and density of carbon are well known, measuring these film properties enabled us to investigate the effect of the mesh on the energy and composition of the depositing flux. When a mesh was used, the film stress showed a monotonic decrease for negative mesh bias voltages greater than 400V, even though the floating potential of the substrate did not vary. We explain this result by the neutralization of some ions when they are near to or passing through the negatively biased mesh. The microstructure of the films showed a change from amorphous to glassy carbonlike with increasing bias. ...

A Room Temperature Polyaniline/SnO 2 Nanofiber Composite Based Layered ZnO/64° YX LiNbO 3 SAW Hydrogen Gas Sensor

Polyaniline/SnO2 nanoflber based surface acoustic wave (SAW) gas sensor has been investigated towards hydrogen (H2) gas. Chemical oxidative polymerization of aniline was employed to synthesize polyaniline nanofibers with SnO2 nanoparticles. The nanocomposite was deposited onto a layered ZnO/64deg YX LiNbO3 SAW transducer. The sensor was exposed to various concentrations of H2 gas and operated at room temperature. The sensor response was found to be 7 kHz towards 1% of H2 in synthetic air. A fast response and recovery with good repeatability in a stable baseline condition were observed at room temperature.

Highly dispersed gold nanoparticles on nitrogen doped carbon nanotubes for hydrogen sensing

Highly dispersed gold (Au) nanoparticles (NPs) supported on nitrogen doped multi-walled carbon nanotubes (NCNTs) were synthesised using a simple electrochemical method. Morphology of Au-NPs and their dispersion profile were studied depending on the applied potential and deposition duration. Novel conductometric gas sensors were developed from the thin films of Au-NPs/NCNTs nanocomposites and evaluated towards H2 gas. Electron microscopy revealed that the Au-NPs were deposited homogeneously on the outer surface of the NCNTs. The average size of the Au-NPs is 5 nm when the applied potential is 10 V for 10 mins and 10 nm when the applied potential is 20 V for 10 mins. The sensors were exposed to different concentrations of H2 in synthetic air at room temperature. The highest sensitivity of 75% was measured towards 1% H2 when average size of Au-NPs on NCNTs is 5 nm.