Optical gas sensing performance of optical fibers coated with sputtered Pd/WO3 films was investigated for low concentration H2
sensing. This optical fiber H2 sensor was prepared by RF sputtering of WO3 on the tip of the multimode fiber at 260°C and
subsequently depositing a Pd catalytic layer. Highly uniform nanotextured film, with individual crystallites having diameters in the
range of 35-50 nm was observed. The sensing mechanism was based on the reflectance change of Pd/WO3 layers towards H2 reliant on
the gasochromic effect. Under the conditions of different sensing layer thicknesses and different operating temperatures, full Vis-NIR
spectra investigations were carried out during the sensor testing. It was found that the optical fiber H2 sensor coated with Pd/WO3 film
show a remarkable optical reflectance response towards H2 concentrations as low as 0.06%. The optimum sensing layer thickness was
200 nm and the optimum operating temperature was found to be 100°C.
Presented is the dielectrophoresis of multiwalled carbon nanotubes on piezoelectric substrates patterned with gold inter
digitated electrodes. An alternating current oscillating at frequencies of 1 kHz and 150 kHz at a peak-to-peak (p-p)
voltage of 1V to 10V was applied to the electrodes, aligning carbon nanotubes suspended in droplets of isopropyl alcohol
(IPA). The carbon nanotubes were suspended in a dielectric medium (IPA) at a concentration of approx 0.1 mg/mL and
stabilized with sodium citrate (0.02 mg/ml). Sonicated for two hours and spun down in a centrifuge for 30 minutes at
4500 rpm. The carbon nanotubes used in the DEP experimentation were multiwalled carbon nanotubes with aspect ratios
of approx 100:1.
Presented is an investigation of surface morphology of arrayed MoOx structures with increasing aspect ratios, and their
resultant superhydrophillic, and their modified superhydrophobic properties. Molybdenum oxide (MoOx) submicron
structures were grown on lithium niobate (LiNbO3) substrates via the thermal evaporation of MoO3 nanopowder at 750°C in a horizontal tube furnace. A mixture of 90% argon and 10% oxygen was introduced into the thermal
evaporation tube at flow rate of 1L/min. This resulted in the formation of a white film which consisted of submicron
tabular structures. Scanning electron micrographs revealed that the tabular molybdenum oxide grew in arrays 80-100°
with respect to the plane of the substrate, with tabular structures with a thickness of approx 0.5 - 1.5μm. Initial testing of
MoOx structures revealed that they were extremely super hydrophilic. Such MoOx arrays were coated with
fluoropolymer Teflon, deposited using the RF sputtering technique. The addition of a semi-conformal Teflon layer
effectively converts the superhydrophilic MoOx layer into a superhydrophobic surface. These superhydrophobic surfaces
exhibit contact angles with aqueous media in excess of 150°. Such surfaces can be utilized for the selective adsorption
and desorption of protein or pharmacokinetic molecules, with applications in drug delivery and biomedical systems.
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