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Here it is reported about the development of microwave disk resonators and their employment as transducers in gas sensing devices. The sensors were developed by designing, modeling and realizing microstrip resonators on several microwave substrates, and by depositing sensing films on the disk. The transduction mechanism can be explained through the change in the permittivity value, in a low thickness of the sensing film, due to the interaction with the gas target. Furthermore, due to the microwave penetration on the sensing material, the response depends on volume effect, not only on surface one. These devices own intrinsic stability due to the fact that the resonance frequency value is related to the physical dimensions. [ABSTRACT FROM AUTHOR]

The development and application of a hydrogen dual sensor (HDS) for the application in the fuel cell (FC) field, is reported. The dual sensing device is based on a ceramic platform head with a semiconducting metal oxide layer (MOx) printed on Pt interdigitated contacts on one side and a Pt serpentine resistance on the back side. MOx layer acts as a conductometric (resistive) gas sensor, allowing to detect low H 2 concentrations in air with high sensitivity and fast response, making it suitable as a leak hydrogen sensor. The proposed Co-doped SnO 2 layer shows high sensitivity to hydrogen (R 0 /R = 90, for 2000 ppm of H 2 ) at 250 °C in air, and with fast response (<3 s). Pt resistance serves as a thermal conductivity sensor, and can used to monitor the whole range of hydrogen concentration (0–100%) in the fuel cell feed line with short response-recovery times, lower than 13 s and 14 s, respectively. The effect of the main functional parameters on the sensor response have been evaluated by bench tests. The results demonstrate that the dual sensor, in spite of its simplicity and cheapness, is promising for application in safety and efficiency control systems for FC power source. [ABSTRACT FROM AUTHOR]

Spinels (AB 2 O 4 ) metal oxides have gain extensive attention in recent years for gas sensing applications. In the present work, the synthesis, characterization and hydrogen sensing characteristics of nanostructured Sm-doped cobalt ferrite (Sm x -CoFe 2−x O 4 ) have been reported. The structural and morphological properties of the synthetized material were studied by X-ray diffraction (XRD), scanning electron microscopy, micro-Raman and X-ray photoelectron spectroscopy (XPS). In order to check the potential applicability of the synthesized Sm-doped Co-ferrite for hydrogen leak sensing, a simple conductometric sensor has been fabricated and tested. The electrical behavior of the sensor has been recorded by exposure to hydrogen and some interfering gases. The results demonstrated that the sensor developed is promising for the detection of hydrogen leak as it possesses good sensitivity, stable behavior and fast response and recovery. [ABSTRACT FROM AUTHOR]

This paper reports on the high sensitivity of sub-spherical In 2 O 3 -Pt nanoparticles (NPs) for detecting ppb levels of acetone, a biomarker for diabetes. The In 2 O 3 -Pt NPs, in the form of monodisperse metal-oxide In 2 O 3 NPs with diameters of 6–8 nm, decorated with 2 wt% Pt metal NPs (2–3 nm) on the surface, were synthesized by a novel non-aqueous sol–gel route. NPs samples were investigated by X-ray powder diffraction (XRPD), using the advanced whole powder pattern modeling (WPPM) method, and high-resolution transmission electron microscopy (HR-TEM). The advantage of this preparative process is that it preserves metallic platinum NPs formed during the synthesis. The highly sensitive acetone sensor based on these NPs, showed a lower detection limit as low as 10 ppb or less, which is the lowest detection limit ever reported for any chemoresistive acetone sensors. This exceptional performance is likely due to the key role played by very small Pt metal NPs uniformly distributed in the In 2 O 3 -Pt nanostructure. The developed sensor would be suitable for use as a highly sensitive, practical breath acetone checker for daily diet and diabetes management and diagnosis. [ABSTRACT FROM AUTHOR]

This work addresses an innovative processing strategy to improve the classification of Steady-State Visually Evoked Potentials (SSVEPs). This strategy resorts to the combined use of fast Fourier transform and Canonical Correlation Analysis in time domain, and manages to outperform by over 5% previous results obtained for highly wearable, single-channel Brain–Computer Interfaces. In fact, a classification accuracy of 90% is reached with only 2-s time response. Then, the proposed algorithm is employed for an experimental characterization of three different Augmented Reality (AR) devices (namely, Microsoft Hololens I, Epson Moverio BT-350, and Oculus Rift S). These devices are used to generate the flickering stimuli necessary to the SSVEP induction. Also, in the three pieces of instrumentation under test, the number of simultaneous visual stimuli was increased with respect to the state-of-art solutions. The aim of the experimental characterization was to evaluate the influence of different AR technologies on the elicitation of user's SSVEPs. Classification accuracy, time response, and information transfer rate were used as figures of merit on nine volunteers for each piece of instrumentation. Experimental results show that choosing an adequate AR headset is crucial for obtaining satisfying performance: in fact, it can be observed that the classification accuracy obtained with Microsoft Hololens is about 20% greater than Epson Moverio one. • Highly wearable, single-channel SSVEP-based BCI. • Enhanced SSVEP classification algorithm. • Performance comparison between AR HMDs used for SSVEPs elicitation. • Metrological characterization in terms of classification accuracy and time response. [ABSTRACT FROM AUTHOR]

Abstract: The light-enhanced NO2 sensing behavior of mesoporous In2O3 is measured and interpreted by means of a new sensing model. The model aims at explaining (i) the drop in electronic resistance of n-type semiconducting In2O3 under UV light exposure, (ii) the light-enhanced reaction to oxidizing gases, and (iii) the faster reaction and regeneration in mesoporous In2O3 as compared to non-porous material. Contrary to the conventional double Schottky model the dominating factor for the change in resistance is a change of oxygen vacancy donor states (0.18eV below the conduction band) in the bulk phase due to photoreduction, instead of chemisorption. For the faster reaction and regeneration we propose an explanation based on enhanced oxygen diffusion in the In2O3 crystal lattice, specifically dominant in the mesoporous structure. The response of ordered mesoporous In2O3 to NO2 is stronger than in case of unstructured bulk material (with an average grain size of ca. 40nm). The reaction is significantly accelerated by illuminating the samples with UV light. However, the response of the mesoporous material is weaker in the illuminated case. [Copyright &y& Elsevier]

Abstract: Crystalline SnO2/reduced graphene oxide (RGO) nanocomposites were synthesized by a one-pot microwave-assisted non-aqueous sol–gel method, in which partially reduction of the graphene oxide and nanoparticle formation occurs simultaneously. Composite samples with different SnO2 loadings on the RGO were prepared and characterized by TEM, XRD, TGA-DSC and FT-IR. Chemoresistive devices, consisting of a thick layer of the samples synthesized on alumina substrates provided with Pt interdigitated electrodes, were fabricated and their electrical and NO2 sensing characteristics investigated. The results obtained have shown the possibility of a fine tuning of the sensing characteristics of the devices fabricated by simply controlling the amount of metal oxide nanoparticles loaded onto the reduced graphene oxide sheets. This was explained on the basis of the critical role played by the n-SnO2/p-RGO heterojunction formed on the composite materials. [Copyright &y& Elsevier]