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The development of electronic gadgets has become of great relevance for the detection of fraud in beverages such as wine, due to the addition of adulterants that bring risks to human health as well as economic impacts. Thus, the present study aims to apply a buckypaper (BP) based on functionalized multiwalled carbon nanotubes (MWCNTs)/cellulose fibers as a sensor for the analysis of Port wine intentionally adulterated with 5 vol.% and 10 vol.% distilled water and ethyl alcohol. The morphology of BP characterized by scanning electron microscopy indicates the formation of agglomerates of random MWCNTs dispersed on the surface and between the fibers of the cellulosic paper. The analysis of the response of the film through the normalized relative resistance change showed a higher response of 0.75 ± 0.16 for adulteration with 10 vol.% of water and a mean response time of 10.0 ± 3.60 s and recovery of approximately 17.2 min for adulteration with 5 vol.% alcohol. Principal component analysis (PCA) was used in data processing to evaluate the ability of BP to recognize and discriminate analytes and adulterating agents, allowing the investigation of its potential application as a low-cost and easy-to-handle multisensor. [ABSTRACT FROM AUTHOR]

ZnO/Pd nanocomposites containing 0.5–3.0 mol.% palladium and possessing improved gas-sensitive properties for VOC's detection were prepared using solvothermal synthesis. The synthesised powders have been characterised using various methods of physicochemical analysis (DSC/TGA, XRD, SET/TEM, XPS). It is shown that Pd@PdO nanoparticles (4–7 nm in diameter) are localised on the surface of ZnO nanoparticles (40–50 nm in size). According to the combined XRD and XPS data, it was found that palladium is in partially oxidised state, and the nanocomposite has a structure close to "core@shell": Pd@PdO. The influence of palladium concentration in the ZnO/Pd composite on the complex of chemoresistive gas-sensitive properties was studied. It is shown that at 250 °C the obtained nanocomposites demonstrate a high (up to 57.8 a.u.) response to 100 ppb–20 ppm acetone, which can be used as a part of supersensitive devices for noninvasive diagnostics of diseases. • ZnO/Pd nanocomposites were prepared using solvothermal synthesis. • The synthesised ZnO/Pd nanocomposites have been characterised using various methods of analysis. • Chemoresistive gas-sensitive properties to a wide group of analyte gases have been studied. • High and reproducible response to acetone (100 ppb-20 ppm) was obtained. [ABSTRACT FROM AUTHOR]

Humanity endeavors to resume crewed missions to the Moon and prepares for the exploration of Mars. These missions will require sustained human presence in space for longer periods than ever before. Space exposes astronauts to demanding conditions, including microgravity, radiation, rapid light-dark cycles, and hazardous chemicals. Gas sensors will be pivotal in preserving astronaut health by providing critical health data (e.g., through breath analysis) and space-resolved environmental information. Here, we explore the recent progress of gas sensors to meet the key needs of space exploration. First, the fundamental sensing principles of electrochemical, chemoresistive, mass-sensitive, and optical sensors are briefly introduced. Then, we connect space-related health challenges with suitable breath markers and sensor solutions, encompassing areas like gut microbiome, muscle activity, cardiovascular health, hepatic and renal function, and circadian rhythm. Finally, environmental exposure guidelines and suitable sensor innovations for distributed air quality monitoring in space vehicles and habitats are presented. • Deep space exploration will require sustained human presence. • Breath analysis enables continuous health monitoring of astronauts. • Space-resolved air quality monitoring is needed for rapid pollutant detection. • Key breath markers and air pollutants with exposure thresholds are identified. • Electrochemical, chemoresistive, mass-sensitive, and optical sensors are reviewed. [ABSTRACT FROM AUTHOR]

The development of electronic gadgets has become of great relevance for the detection of fraud in beverages such as wine, due to the addition of adulterants that bring risks to human health as well as economic impacts. Thus, the present study aims to apply a buckypaper (BP) based on functionalized multiwalled carbon nanotubes (MWCNTs)/cellulose fibers as a sensor for the analysis of Port wine intentionally adulterated with 5 vol.% and 10 vol.% distilled water and ethyl alcohol. The morphology of BP characterized by scanning electron microscopy indicates the formation of agglomerates of random MWCNTs dispersed on the surface and between the fibers of the cellulosic paper. The analysis of the response of the film through the normalized relative resistance change showed a higher response of 0.75 ± 0.16 for adulteration with 10 vol.% of water and a mean response time of 10.0 ± 3.60 s and recovery of approximately 17.2 min for adulteration with 5 vol.% alcohol. Principal component analysis (PCA) was used in data processing to evaluate the ability of BP to recognize and discriminate analytes and adulterating agents, allowing the investigation of its potential application as a low-cost and easy-to-handle multisensor.

Sensors of volatile organic compounds (VOCs) play a vital role in environmental monitoring. Although much progress has been made to develop new sensing materials, it remains challenging to detect a particular VOC selectively and without the interference of humidity. Herein, we report the effect of In2O3 nanoparticles on the VOC-sensing performance of ZnO twin-rods. The VOC-sensing tests were carried out in dry air and at a relative humidity (RH) of 26, 59, and 98%. The results indicated that the In2O3/ZnO heterostructure exhibited an improved sensing performance to triethylamine (TEA) compared to ZnO. In dry air, the responses to 100 ppm of TEA at 350 °C were 60.2 for the In2O3/ZnO heterostructure and 39.2 for pure ZnO. In2O3/ZnO even exhibited a high response of 6.2 to 1 ppm of TEA. Moreover, In2O3/ZnO exhibited a response to TEA up to 46.2 times higher than those of the other VOCs, indicating excellent selectivity. At 98% RH, the In2O3/ZnO heterostructure still had a high sensitivity to TEA, showing a response of 21.2 to 100 ppm of TEA with a response time of 1 s. The improved TEA-sensing performance of the In2O3/ZnO heterostructure can be attributed to the formation of the n-n heterojunction.

Based on an analysis of the signal characteristics of gas sensors, this work presents a chemoresistive sensor readout circuit design for detecting gases with slow response time characteristics. The proposed readout circuit directly generates a reference voltage corresponding to the initial value of the gas sensor and extracts only the amount of gas concentration change in the sensor. Because the proposed readout circuit can adaptively regenerate the suitable reference voltage under various changing ambient conditions, it can alleviate the variation in output values at the same gas concentration caused by non-uniformities among gas sensors. Furthermore, this readout circuit effectively eliminates the initial value shifts due to the poor reproducibility of the gas sensor itself without requiring complex digital signal calibrations. This work focuses on a commercially viable readout circuit structure that can effectively obtain slow response gas information without requiring a large capacitor. The proposed readout circuit operation was verified by simulations using spectre in cadence simulation software. It was then implemented on a printed circuit board with discrete components to confirm the effectiveness with existing gas sensor systems and its commercial viability.

Spinel NiCo2O4 material has received considerable attention as an excellent gas sensing material. In this study, we report facile and hydrothermal method synthesis for preparing mesoporous NiCo2O4 and its composite with reduced graphene oxide (rGO) by wet impregnation method. The as-prepared samples were subjected to structural and morphological investigations. The constructed NiCo2O4-rGO composite gas sensor shows superior NH3 gas sensing performance at room temperature and the response for 100 ppm NH3 is 1.068 at room temperature. Moreover, this sensor shows better gas sensing performances with fast response times, recovery times, and good repeatability for a test period of 10 cycles along with high selectivity for NH3 gas sensor. Thus, NiCo2O4-rGO composite may be used as an efficient NH3 gas sensor. The sensing mechanism of the NiCo2O4-rGO composite sensors has also been proposed in this paper. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Magnetic iron oxide nanoparticles decorated graphene gas sensor is presented. • The accurate particle size synthesis was conducted by using poly(ion liquids) (PIL). • The influence of particle size on sensitivity was evaluated. • Particles of a size of 20 nm have a significant enhancement of sensitivity. • The graphene-Fe 3 O 4 sensor detect trace amounts (1 ppm) of the NO 2 and ethanol. Abstract We report a synthesis of magnetic nanoparticles chemically immobilized onto reduced graphene oxide sheets (referred to as rGO-Fe 3 O 4 NPs) as a gas and vapor sensing platform with precisely designed particle size of 5, 10 and 20 nm to explore their influence of particle size on sensing performance. The rGO-Fe 3 O 4 NP sensors have been investigated their responses to different gases and volatile organic compounds (VOCs) at part-per-million (ppm) levels. Results show that the Fe 3 O 4 NPs with smaller size (5 and 10 nm) on the rGO surface led to a lower sensitivity, while particles of a size of 20 nm have a significant enhancement of sensitivity compared to the bare rGO sensor. The rGO-Fe 3 O 4 NP20 sensor can detect trace amounts of NO 2 gas and ethanol vapor at the 1 ppm and is highly selective to the NO 2 and ethanol among other tested gases and VOCs, respectively. The particle size causes different distribution behaviour of NPs over rGO surface and interspaced between them, which results in deceased or increased the surface interactions between gas and graphene. The NPs themselves contained different defects level and the charge depletion layer that affect their adsorption gas/vapor molecules, which are explained for different sensing responses. [ABSTRACT FROM AUTHOR]

The dc electrical and volatile organic compound (VOC) sensing properties of TiO 2 nanotubes in both anatase and rutile phases were investigated. TiO 2 nanotube arrays were obtained in aqueous HF (0.5 wt.%) electrolytes by anodizing of Ti thin films that deposited on quartz substrates using thermal evaporation. Anodization was performed at 10 V in aqueous HF at 0 °C. Then the fabricated TiO 2 nanotubes were annealed at 300 °C and at 700 °C under dry air for 5 h to obtain anatase and rutile phases, respectively. The TiO 2 nanotubes were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) as structural, and UV–vis spectrophotometer as optical. The current voltage characteristics of the nanotubes under dry air flow revealed that the conductivity of the sample with anatase phase was higher than that of the sample with rutile phase. The VOCs sensing properties of the nanotubes were investigated at 200 °C. It was found that the sensor response of anatase was higher than that of rutile for almost all VOC gases. On the other hand, the sensitivities of two sensors are the highest for isopropyl alcohol. [ABSTRACT FROM AUTHOR]

Abstract: Ti thin films were anodized in aqueous HF (0.5wt.%) and in polar organic (0.5wt.% NH4F+ethylene glycol) electrolytes to form TiO2 nanotube arrays. Ti thin films were deposited on microscope glass substrates and then anodized. Anodization was performed at potentials ranging from 5V to 20V for the aqueous HF and from 20V to 60V for the polar organic electrolytes over the temperatures range from 0 to 20°C. The TiO2 nanotubes were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX). It has been observed that anodization of the deposited Ti thin films with aqueous HF solution at 0°C resulted in nanotube-type structures with diameters in the range of 30–80nm for an applied voltage of 10V. In addition, the nanotube-type structure is observed for polar organic electrolyte at room temperature at the anodization voltage higher than 40V. The volatile organic compound (VOC) sensing properties of TiO2 nanotubes fabricated using different electrolytes were investigated at 200°C. The maximum sensor response is obtained for carbon tetrachloride. The sensor response is dependent on porosity of TiO2. The highest sensor response is observed for TiO2 nanotubes which are synthesized using aqueous HF electrolyte and have very high porosity. [Copyright &y& Elsevier]

Based on an analysis of the signal characteristics of gas sensors, this work presents a chemoresistive sensor readout circuit design for detecting gases with slow response time characteristics. The proposed readout circuit directly generates a reference voltage corresponding to the initial value of the gas sensor and extracts only the amount of gas concentration change in the sensor. Because the proposed readout circuit can adaptively regenerate the suitable reference voltage under various changing ambient conditions, it can alleviate the variation in output values at the same gas concentration caused by non-uniformities among gas sensors. Furthermore, this readout circuit effectively eliminates the initial value shifts due to the poor reproducibility of the gas sensor itself without requiring complex digital signal calibrations. This work focuses on a commercially viable readout circuit structure that can effectively obtain slow response gas information without requiring a large capacitor. The proposed readout circuit operation was verified by simulations using spectre in cadence simulation software. It was then implemented on a printed circuit board with discrete components to confirm the effectiveness with existing gas sensor systems and its commercial viability. [ABSTRACT FROM AUTHOR]

Abstract: The precise knowledge of the operating temperature is a very important topic in the field of gas sensing. Experimental evidence suggests in fact that not only the temperature of the film but also that of the air in the immediate contact with the sensing layer is crucial to determine the sensor''s behavior. In this paper we analyze the main factors which contribute to heat exchange inside the test chamber; a system of three equations is proposed to calculate the temperature in the various zones of the system, in particular that of the gas adjacent to the sensor. The model, applied to the system operating in flow, was in good agreement with the experimental data. [Copyright &y& Elsevier]