We report on novel, sensitive, selective and low-temperature hydrogen sulfide (H 2 S) gas sensors based on metal-oxide nanoparticles incorporated within polymeric matrix composites. the copper-Oxide (CuO) nanoparticles were prepared by a colloid microwave-assisted hydrothermal method that enables precise control of nanoparticle size. The sodium carboxymethyl cellulose (CMC) powder with 5% glycerol ionic liquid (IL) was prepared and mixed with different concentrations of CuO NPs (2.5-7.5 wt.%) to produce flexible and semi-conductive polymeric matrix membranes. Each membrane was then sandwiched between a pair of electrodes to produce an H 2 S gas sensor. the temperature-dependent gas sensing characteristics of the prepared sensors were investigated over the temperature ranges from 40 °C to 80 °C. The sensors exhibited high sensitivity and reasonably fast responses to H 2 S gas at low working temperatures and at a low gas concentration of 15 ppm. Moreover, the sensors were highly selective to H 2 S gas, and they showed low humidity dependence, which indicates reliable functioning in humid atmospheres. This organic-inorganic hybrid-materials gas sensor is flexible, with good sensitivity and low power consumption has the potential to be used in harsh environments.Hydrogen sulfide gas (H 2 S) is a major air pollutant that is produced in a large quantity from industrial fields such as petroleum and gas drilling and refining, sewage treatment, coke ovens, kraft paper mills, and landfills 1,2 . H 2 S gas is toxic gas with a malodor of rotten eggs. It can damage human respiratory and nerve systems, causing the public to lose consciousness with a possibility to die at minimal concentrations as low as a few hundreds of ppm 3-5 . Therefore, improving H 2 S sensors in terms of sensitivity, selectivity, response time, power consumption, and the cost is needed for environmental and safety concerns.Different materials and methods have been reported in the literature for H 2 S gas detection, including electrochemical (solid electrolyte) sensors 5 , optical sensors 6,7 , piezoelectric sensors 8,9 , and oxide-semiconductor sensors 10,11 . However, most of these sensors developed using such methods suffer from high fabrication cost, high power consumption, poor stability, and malfunction in harsh environment 12,13 . Therefore, these sensors have been under continuous development to meet the growing demand of high-performance sensors. Metal-oxide semiconducting nanoparticles based sensors are the most promising materials for the H 2 S gas detection; they are cost-effective, easy to operate and fast in response with high sensitivity to the target gas 14,15 . Therefore, the development of new sensors that include polymer membranes and metal-oxide nanoparticles (organic-inorganic sensors) is expected to enhance the functionalities of such sensors; as they are flexible, easy to fabricate, and can be operated at low temperature with a low electrical power requirement [14][15][16] . Metal-oxide based sensors are flexible, easy to fabricate,...

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A technique is presented to measure simultaneously the catalytic efficiency (φc) and the atom concentration (α∞) in a dissociated hypersonic free stream. The principle involved is to measure the differential heat transfer by using a combination of axisymmetric and two-dimensional differential catalytic probes, mounted side by side in an uniform free stream. Using these measured quantities in the appropriate stagnation point heat-transfer relations for a frozen flow, simple formulas for φc and α∞ are derived, which are independent of such quantities as viscosity, velocity, and density. This self-calibrating principle is shown to apply even in the viscous shock layer (merged layer) regime. The most suitable geometric proportions for the probes are given. The practical feasibility of this technique has been successfully demonstrated by measuring the gauge-catalytic efficiency of a silver surface and the free-stream oxygen atom concentrations in the University of Toronto Institute of Aerospace Studies 11 × 15-in. hypersonic shock tunnel test section. The free-stream atom concentration α∞ was measured at five reservoir conditions (14.2 atm ≤ P0 ≤ 40.7 atm, 4530°K ≤ T0 ≤ 4700°K, 0.54 ≥ α0 ≥ 0.32) and varied from 0.30 to 0.16. The measured values of α∞ compared favorably with those computed from coupled vibrational and dissociational nonequilibrium nozzle flow calculations.

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