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Organic–inorganic ternary nanohybrids consisting of oxidized-single walled carbon nanohorns-SnO2-polyvinylpyrrolidone (ox-SWCNH/SnO2/PVP) with stoichiometry 1/1/1 and 2/1/1 and ox-SWCNH/ZnO/PVP = 5/2/1 and 5/3/2 (all mass ratios) were synthesized and characterized as sensing films of chemiresistive test structures for ethanol vapor detection in dry air, in the range from 0 up to 50 mg/L. All the sensing films had an ox-SWCNH concentration in the range of 33.3–62.5 wt%. A comparison between the transfer functions and the response and recovery times of these sensing devices has shown that the structures with ox-SWCNH/SnO2/PVP = 1/1/1 have the highest relative sensitivities of 0.0022 (mg/L)−1, while the devices with ox-SWCNH/SnO2/PVP = 2/1/1 have the lowest response time (15 s) and recovery time (50 s) for a room temperature operation, proving the key role of carbonic material in shaping the static and dynamic performance of the sensor. These response and recovery times are lower than those of “heated” commercial sensors. The sensing mechanism is explained in terms of the overall response of a p-type semiconductor, where ox-SWCNH percolated between electrodes of the sensor, shunting the heterojunctions made between n-type SnO2 or ZnO and p-type ox-SWCNH. The hard–soft acid–base (HSAB) principle supports this mechanism. The low power consumption of these devices, below 2 mW, and the sensing performances at room temperature may open new avenues towards ethanol sensors for passive samplers of environment monitoring, alcohol test portable instruments and wireless network sensors for Internet of Things applications.

Many principles and methods have been described in literature for measuring relative humidity (RH) and several types of materials have been employed as RH sensing layers [1,2]. [...]

This paper presents the manufacturing of high-performance millimeter wave lumped elements on polyimide membranes obtained by micromachining of semi-insulating GaAs. The microwave performances of the devices are compared with those obtained for similar structures manufactured on SiO2/Si3N4/SiO2 membranes on silicon micromachined substrates, as well as with the performances of similar devices manufactured on bulk GaAs and high-resistivity silicon. S parameter analysis and the computed lumped equivalent circuit emphasize the substantial decrease in the parasitic capacitances and, as a result, the outstanding improvement in the resonant frequency of membrane supported inductors. Comparative analysis of roughness and planarity of both types of micromachined structures was also performed. Polyimide membranes manufactured on GaAs substrate have proved to be a very good support for millimeter wave circuit elements, both from mechanical as well as electrical points of view.