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The leakage of gases and chemical vapors is a common accident in laboratory processes that requires a rapid response to avoid harmful effects if humans and instruments are exposed to this leakage. In this paper, the performance of a portable sensor node designed for integration with mobile and stationary robots used to transport chemical samples in automated laboratories was tested and evaluated. The sensor node has four main layers for executing several functions, such as power management, control and data preprocessing, sensing gases and environmental parameters, and communication and data transmission. The responses of three metal oxide semiconductor sensors, BME680, ENS160, and SGP41, integrated into the sensing layer have been recorded for various volumes of selected chemicals and volatile organic compounds, including ammonia, pentane, tetrahydrofuran, butanol, phenol, xylene, benzene, ethanol, methanol, acetone, toluene, and isopropanol. For mobile applications, the sensor node was attached to a sample holder on a mobile robot (ASTI ProBOT L). In addition, the sensor nodes were positioned close to automation systems, including stationary robots. The experimental results revealed that the tested sensors have a different response to the tested volumes and can be used efficiently for hazardous gas leakage detection and monitoring. [ABSTRACT FROM AUTHOR]

CMOS-MEMS microresonators have become excellent candidates for developing portable chemical VOC sensing systems thanks to their extremely large mass sensitivity, extraordinary miniaturization capabilities, and on-chip integration with CMOS circuitry to operate as a self-sustained oscillator. This paper presents two 4-anchored MEMS plate resonators, with a resonance frequency of 2.2 MHz and 380 kHz, fabricated together with the required circuitry using a commercial 0.35 µm CMOS technology and then coated with poly-4-vinylheduorocumyl alcohol (P4V) via inkjet deposition. Such P4V constitutes a functionalization layer for specific acetone detection as a key step in the development of an integrated device for non-invasive diabetes diagnosis through exhaled human breath. The coated sensor system has been proven to increase the acetone injection response by 6-times compared to the uncoated platform and shows a cross-sensitivity to butane of 1:11. Experimental data show an acetone sensitivity of -0.012 ppm Hz-1 in the best case that, together with a measured frequency Allan deviation of 0.32 ppm, provides an expected limit of detection as low as 20 ppb of acetone. Additionally, this work presents an alternative resonator design with folded flexure anchors that provide a drastic reduction of the sensor temperature sensitivity and mitigate the impact of a fluid flow inherent to the calibration system. [ABSTRACT FROM AUTHOR]

Acetone is a biomarker of diabetics. The exhaled acetone concentration of diabetics is higher than that of a healthy person. Semiconductor gas sensors provide an accurate non-invasive detection method for low-concentration breath acetone of diabetics, but the their selectivity presents a drawback. In order to detect the concentration of exhaled acetone accurately from exhaled breath, an acetone detector based on a separation channel and semiconductor gas sensors is presented in this paper. Carbon dioxide, acetone, and ethanol were simulated and separated by a gas chromatography (GC) column in the separation channel. The separated time of carbon dioxide, exhaled acetone, and ethanol are 25 s, 236 s, and 574 s at room temperature, respectively. Carbon dioxide, acetone, and ethanol flow into three gas detection channels with the control of a time-sharing conversion switch. Then, carbon dioxide, acetone, and ethanol can be detected accurately by the semiconductor gas sensors. Exhaled acetone can be measured as low as 1 ppm within 5 min without any interference. A highly selective acetone detector based on GC and semiconductor technology has potential in monitoring and detecting diabetes as well as safe driving in a non-invasive way. [ABSTRACT FROM AUTHOR]

Acetone is a slightly toxic volatile organic gas, which exists in the breath and is closely related to diseases such as diabetes. In this paper, a quartz crystal microbalance (QCM) was used to fabricate an acetone sensor, and graphene quantum dots (GQDs) were used as a gas-sensing material to modify the QCM. GQDs were prepared by citrate pyrolysis and characterized by high-resolution transmission electron microscopy (TEM). The gas sensitivity of the sensor to low concentrations of acetone was investigated. It exhibited good linearity at acetone concentrations of less than 240 ppm with a sensitivity of 16.78 Hz/ppm and a minimum detection limit of 2.5 ppm, and the fitted line had a coefficient of determination R2 of 0.95658. In a mixture of acetone, butanol, and isopropanol, the sensor exhibited good selectivity for acetone. For different acetone concentrations, the response speed of the same sensor was basically the same, and the response and recovery times were 32 and 48 s, respectively. We showed that the prepared gas sensor has good sensitivity, repeatability, and selectivity for low concentrations of acetone. [ABSTRACT FROM AUTHOR]

Fabrication of fast, high-selectivity and reliable gas sensors for real-time monitoring of acetone in exhaled gases remains a key challenge for the development of accurate diabetes diagnosis systems. Inspired by the cactus, in this paper, acetone gas sensor using graphene oxide (GO) with porous zinc oxide (ZnO) nanotube clusters was introduced by room temperature liquid phase method. Porous ZnO nanotubes with lengths of 1∼2 μm formed nanoclusters and were uniformly dispersed on the GO sheets, presenting a specific "cactus-like" three-dimensional structure, which supplied more channels and active sites for the diffuse and adsorption of acetone molecules. The cactus-like GO/ZnO sensor exhibits a high response value of 54.3 (5.9-fold improvement compared to ZnO), fast response/recovery time of 3.8/2.9 s (15.7/19.8 s for ZnO), and robust stability to 50 ppm acetone at 180 °C. Special, the sensor can detect even acetone down to 0.1 ppm with a remarkable response (2.1). Moreover, the adsorption energies of different gases were calculated by density functional theory, which further confirmed the good acetone selectivity of the cactus-like GO/ZnO sensor. The appreciable gas sensing performances are mainly attributed to the unique cactus-like nanostructure with abundant holes and high specific surface area, as well as the heterojunctions between GO and ZnO. This unique biomimetic structure provides a promising strategy for designing acetone gas sensors with high practicality. [ABSTRACT FROM AUTHOR]

In recent years, clinical studies have found that acetone concentration in exhaled breath can be taken as a characteristic marker of diabetes. Metal–oxide–semiconductor (MOS) materials are widely used in acetone gas sensors due to their low cost, high sensitivity, fast response/recovery time, and easy integration. This paper reviews recent progress in acetone sensors based on MOS materials for diabetes diagnosis. The methods of improving the performance of acetone sensor have been explored for comparison, especially in high humidity conditions. We summarize the current excellent methods of preparations of sensors based on MOSs and hope to provide some help for the progress of acetone sensors in the diagnosis of diabetes. [ABSTRACT FROM AUTHOR]

This paper reports the preparation of an excellent acetone gas-sensitive material consisting of a Eu3+-decorated α-Fe2O3 microflower (EFM) composite film by a simple hydrothermal and calcination method. For comparison, pure α-Fe2O3 microflowers (PFM) are prepared with the same method. Scanning electron microscopy (SEM) images show that the samples are a loose 3D flower-like structure with many voids surrounded by many thin nanosheets. The structure of the samples was investigated using X-ray diffraction and X-ray photoelectron spectroscopy (XPS). The PFM and EFM gas sensors were systematically tested for gas sensitivity at an optimum temperature of 145 °C. The sensitivity of the EFM gas sensor with 50 ppm of acetone gas was 83, which was up to four times that of the PFM sensitivity (19). The EFM sensor had an extremely fast response time (4 s) and recovery time (38 s). Moreover, the minimum concentration of acetone that we could detect was 0.1 ppm with a response value of 2.1. The enhancement of gas sensitivity was attributed to the high catalytic activity of the Eu3+ additive. [ABSTRACT FROM AUTHOR]

The competitive adsorption of water over Volatile Organic Compound (VOC) in Metal Oxide Sensor (MOS) is well known in literature and is one of the main disturbing factors that contributes to worsen electronic nose (enose) performance in classifying and quantifying odours. This constitutes one of the most important limitations for the large-scale diffusion of e-noses since it hinders their use for several applications. In this paper, we investigate the possibility to implement the Orthogonal Signal Correction (OSC) method for compensating the relative humidity effect on MOS sensors. Two different e-noses have been used for this study, each one equipped with a different sensor array comprising only MOS sensors. In order to investigate the relative humidity (RH) effect on the sensors response for different compounds, four calibrants (acetone, butanol dimethyl-disulphide and toluene) have been analyzed at differente levels of RH (20%, 50% and 80%, for a fixed temperature of 20°C) for training the instruments to compensate its intereference. The concentration of the sample analyzed has been set equal to 2.5 ppm. The results achieved proved that the OSC implementation can be a suitable method for the mitigation of the RH interference on MOS sensors, since its application significantly improved the performances of classification, increasing the global accuracy above 70% for both e-noses considered in this study. [ABSTRACT FROM AUTHOR]

In this paper different Indium Tin Oxide (ITO)-based ethanol vapor sensors (fabricated as thin films and nanoparticles) are presented, and their structural and sensing properties are investigated. An Electrophoretic Deposition (EPD)-Enhanced method is proposed for the fabrication of pure, and Ag-decorated indium tin oxide sensors. The proposed sensors are then compared to conventional indium tin oxide sensors fabricated by sputtering (thin film), and drop-casting method in terms of response, and working temperature. It is shown that the electrophoretic deposition method has decreased the final particle size of the indium tin oxide nanoparticles by limiting the agglomeration of nanoparticles, and increased the sparsity of the particles forming the sensing material. Results suggest that compared to the conventional sensors, the sensors fabricated by the proposed electrophoretic deposition method (i.e., the pure-indium tin oxide (EPD-TF), and the Ag-decorated indium tin oxide (Ag-EPD) sensors), has considerably better performance for the detection of the ethanol vapors, showing reduced working temperature (110 and 130 °C, respectively), higher response, and better selectivity over CO, methane, methanol, and acetone. Moreover, the response and recovery time of the proposed sensors were found to be lower than most of the previously reported indium tin oxide-based ethanol sensors, approving the positive effect of the electrophoretic method as a simple, controllable method for sensor fabrication. [ABSTRACT FROM AUTHOR]

Zeolite additional layers coating on metal oxide surfaces to improve the selectivity and response values of the sensors are effective and widely used. The specific adsorption and diffusion of gas molecules in the zeolite are recognised to play an important role in gas sensing improvement. In this work, the adsorption and diffusion behaviours of formaldehyde and acetone in H-Y and H-A zeolites were calculated by Monte Carlo and molecular dynamics simulations. The loading of acetone is greater than formaldehyde in these two kinds of zeolites under the same temperature and pressure, and the water load is lower. The simulation results show that the effects of the nature of the guest molecule and steric hindrance of the diffusing molecule on diffusivity are significant. The diffusivity in H-A zeolite decreases by several orders of magnitude than that in H-Y zeolite However, in H-A zeolite, the internal diffusion dominates, and only the smaller diameter formaldehyde can diffuse between the pores, which is beneficial to improving the sensing properties of formaldehyde. In addition, in the competition diffusion with water molecules, formaldehyde dominates than acetone. The H-Y/SnO2 and H-A/SnO2 sensors were prepared to verify the reliability of the molecular simulations. Research highlights The adsorption and diffusion behaviour of formaldehyde and acetone in H-Y and H-A zeolites were investigated using molecular simulation. Molecular diameter mainly influences the kinetic behaviour. The sensitisation mechanism of H-Y/SnO2 sensor to acetone and H-A/SnO2 sensor to formaldehyde was proved. Focuses on the relationship between gas-sensing the performance of zeolite-covered SnO2 sensors and the adsorption. [ABSTRACT FROM AUTHOR]

Thick-film VOCs sensors based on ruthenated multi-walled carbon nanotubes coated with tin-dioxide nanoparticles (MWCNTs/SnO2) nanocomposite structures are prepared using three methods: hydrothermal synthesis, sol-gel technique and their combined method. It is shown that the optimal conditions for applications as acetone and toluene as well as ethanol and methanol vapors sensors in view of high response and selectivity relative to each other depend on choice of material synthesis method, mass ratio of the nanocomposite components and selected operating temperature. Selective sensitivity to acetone and toluene vapors at 150oC operating temperature MWCNTs/SnO2 are shown sensor structures with the mass ratio of the components 1:4 and 1:24, respectively. The samples with 1:200 mass ratio of the nanocomposite components are shown the selective response to acetone vapor exposure in the range of 200-250oC operating temperatures. The high sensitivity to ethanol and methanol vapors at 200oC operating temperature was revealed for the sensor structures made by different methods with the 1:8, 1:24, 1:50 and 1:66 ratios of the components, respectively. The results of research works related to the study of thick-film multiwall carbon nanotube-tin oxide nanocomposite sensors of propylene glycol (PG), dimethylformamide (DMF) and formaldehyde (FA) vapors are also presented in this paper. Investigations of response-recovery characteristics in the 50-300oC operating temperature range reveal that the optimal operating temperature for PG, DMF and FA vapor sensors, taking into account both high response and acceptable response and recovery times are about 200 and 220oC, respectively. The dependence of the sensor response on gas concentration is linear in all cases. Minimal propylene glycol, dimethylformamide and formaldehyde gas concentrations, where the perceptible signal was noticed, were 13, 5 and 115 ppm, respectively. [ABSTRACT FROM AUTHOR]

The paper presents the tuning of sensitivity and selectivity performance of volatile organic compounds (VOCs) chemoresistive sensors for biomarker detection using the hybridization of pristine graphene (pG) and metal organic frameworks (MOFs). The synergistic effect of this nanocomposite material was discovered showing improved sensing performances where graphene acts as a highly conductive sensing element, and MOFs, with a high surface area and adsorption capacity provide an enhanced sensitivity and selectivity for specific VOCs. By combining and selecting different MOFs, we proposed that is possible to tailor sensing performances of chemoresistive sensors for VOC biomarkers detection. To prove that graphene hybrid nanocomposite with selected MOFs including copper–benzene-1,3,5-tricarboxylate (pG-Cu BTC), zirconium 1,4-dicarboxybenzene (pG-UiO 66) and 2-methylimidazole zinc salt (pG-ZIF 8), were investigated to enhance the sensing performance and capability of distinguishing different VOC biomarkers (e.g., methanol, ethanol, chloroform, acetone, acetonitrile and THF). Results showed that the pG-Cu BTC sensor has the highest sensitivity and selectivity towards chloroform and methanol VOCs at 2.82–22.6 ppm level. The proposed concept presents a valuable contribution for the development of low-cost and high-performing VOC biomarker sensors for monitoring human health from metabolic human breath and further implementation for non-invasive biomedical diagnostics for personalized telehealth monitoring. Image 10660 [ABSTRACT FROM AUTHOR]

In this paper, YSZ-based high performance acetone sensor was successfully developed for intelligent medical service, environmental monitoring, and safety production of smart city. New type spinel electrode sensing materials NiGa x Al 2-x O 4 (x = 0, 0.6, 1 and 1.4) were synthesized by a sol-gel method. Compared to the other sensing electrode materials, NiGa 0.6 Al 1.4 O 4 had the highest electrochemical catalytic activity to acetone, and the sensor based on NiGa 0.6 Al 1.4 O 4 -SE performed the best sensing performance of −48 mV to 10 ppm acetone. Moreover, the present acetone sensor has a wide detection range of 0.2–1000 ppm, with sensitivity of −45 mV/decade, meeting the field of diabetic non-invasive diagnosis and real-time in-situ environmental monitoring. In addition, the device also performs excellent repeatability, acceptable selectivity, terrific humidity resistance and marvelous long-term stability during continuous measurements over 30 days. Overall, based on its excellent sensing performance, the developed sensor has marvelous application prospects for acetone detection in intelligent medical service, environmental monitoring, and safety production fields of smart city. • NiGa x Al 2-x O 4 were firstly used as sensing electrode for YSZ-based acetone sensor. • The sensor with NiGa 0.6 Al 1.4 O 4 -SE performed the largest response to 10 ppm acetone. • The low detection limit can reach 200 ppb and the detection range is 0.2–1000 ppm • The sensor has excellent repeatability, humidity resistance and long-term stability. [ABSTRACT FROM AUTHOR]

• The superfine porous NiFe2O4 microspheres were successfully synthesized via a one-step solvothermal approach. • The porous NiFe2O4 sensors exhibited high and rapid response for selective detection of acetone gas. • The porous NiFe2O4 sensors exhibited low detection limit (200 ppb) to acetone gas. Spinel-type oxides have attracted a broad interest in sensing materials research owing to their high catalytic activity and flexibly tunable chemical properties. Here, we report the synthesis of superfine porous NiFe 2 O 4 microspheres by one-step solvothermal approach, in order to fabricate ultra-sensitive acetone sensors for real-time monitoring, relying on the high catalytic activity of NiFe 2 O 4 and effective mass transfer property of porous microspheres structure. The porous NiFe 2 O 4 sensors displayed high selectivity to acetone against other interfering gases, giving a high sensitivity (27.4), fast response time (2 s) towards 100 ppm acetone and low detection limit (200 ppb) at 250 °C. This paper proposed a general approach for fabricating highly sensitive gas sensor based on spinel-type oxides in monitoring volatile organic pollutants. [ABSTRACT FROM AUTHOR]

A sensitive volatile organic vapor sensor based on the LSPR properties of silver triangular nanoprisms is proposed in this paper. The triangular nanoprisms were fabricated by a nanosphere lithography (NSL) method. They have sharp vertices and edges, and are arranged in an ideal hexangular array. These characteristics ensure that they exhibit an excellent LSPR spectrum and a high sensitivity to the exterior environment changes. The LSPR spectra responding to ethanol vapor and four other volatile organic vapors--acetone, benzene, hexane and propanol--were measured with a UV-vis spectrometer in real time. Compared with the other four vapors, ethanol exhibits the highest sensitivity (~0.1 nm/mg L-1) and the lowest detection limit (~10 mg/L) in the spectral tests. The ethanol vapor test process is also fast (~4 s) and reversible. These insights demonstrate that the triangular nanoprism based nano-sensor can be used in ethanol vapor detection applications. [ABSTRACT FROM AUTHOR]

In this paper, to address the problems of large blood draws, long testing times, and the inability to achieve dynamic detection of invasive testing for diabetes, stemming from the principle that type 1 diabetic patients exhale significantly higher levels of acetone than normal people, a FAIMS-MEMS gas sensor was designed to detect acetone, which utilizes the characteristics of high sensitivity, fast response, and non-invasive operation. It is prepared by MEMS processes, such as photolithography, etching, and sputtering, its specific dimensions are 4000 μm in length, 3000 μm in width and 800 μm in height and the related test system was built to detect acetone gas. The test results show that when acetone below 0.8 ppm is introduced, the voltage value detected by the sensor basically does not change, while when acetone gas exceeds 1.8 ppm, the voltage value detected by the sensor increases significantly. The detection accuracy of the sensor prepared by this method is about 0.02 ppm/mV, and the voltage change can reach 1 V with a response time of 3 s and a recovery time of 4 s when tested under 20 ppm acetone environment; this has good repeatability and stability, and has great prospects in the field of non-invasive detection of type 1 diabetes. [ABSTRACT FROM AUTHOR]

Precise temperature, humidity, and organic pollutants monitoring are required for industrial, environmental and medical applications. The interesting properties of polyaniline for sensors, such as environmental responsiveness and stability, combined with the large surface area and tunable properties of graphene oxide, offer excellent prospects for the development of sensor materials. In this paper, we show that HCl-doped polyaniline/reduced graphene oxide (PANI/rGO) layer-by-layer deposition and subsequent reduction can be used as resistive sensors for temperature, humidity, acetone, and electrochemical sensors for organophosphate detection in aqueous solutions. Sensors were characterized using atomic force and scanning electron microscopies and energy-dispersive x-ray and Raman spectroscopies, and impedance spectroscopy complemented by semi-empirical quantum chemical calculations. Reduction temperature and bilayer numbers influence PANI/rGO sensor characteristics significantly. The results show that only one PANI/rGO bilayer is needed to provide a temperature coefficient of resistance of − 0.758 °C−1 and 37% sensitivity at 95% relative humidity. PANI/rGO shows potential for electrochemical detection of dimethoate affected by the number of bilayers and reduction temperature. The response to acetone vapor is linear from 1 to 60 ppm and detectable at 1 ppm. The sensors do not respond to methanol and some other volatile organic compounds (VOCs) at the same concentration. Food monitoring with total VOCs detection was successfully demonstrated. PANI/rGO sensors feature versatile sensing capabilities, making them feasible due to their rapid production and low cost. [Display omitted] • Versatile PANI/rGO multimodal sensors, interpreted by semi-empirical quantum calculations and impedance spectroscopy. • Resistive PANI/rGO relative humidity and temperature sensors achieved with high sensitivity. • Highly sensitive and selective detection of acetone as low as 1 ppm demonstrated. • PANI/rGO detects VOCs from food samples, allowing differentiation of food types. • Dimethoate pesticide is detectable by optimization number of layers and reduction. [ABSTRACT FROM AUTHOR]

This research represents a novel detection method of acetone level in the exhaled breath samples (RH=88 %) based on polypyrrole/tungsten oxide (PPy/WO3) nanocomposite sensor. The PPy/WO3 sensor was fabricated by the deposition of nanocomposite on/between interdigitated electrodes (IDEs) through electrospray coating and was then characterized by FE‐SEM imaging. In this detection method, the coulometric signal of the sensor was calculated using Fast Fourier Continuous Cyclic Voltammetry (FFTCCV), where cyclic voltammetry (CV) was applied to the sensor in the defined potential rang and then charge changes of the sensor was obtained by integration of the current in all scanned potential ranges. FFTCCV method enhances the sensitivity of the sensor when exposed to the gas mixtures containing acetone. In addition to its fast coulometric response time (≤5 s) in the two linear ranges of 0.7–2.8 ppm and 2.8–28.2 ppm (R2=0.99), FFTCCV method provides the low detection limit of 70 ppb, and high sensitivity toward acetone at the optimum values of the parameters. The fabricated sensor showed great selectivity toward acetone when exposed to humid air and some exhaled gas like carbon dioxide, ammonia, methanol, ethanol and alkyl amines. The results were very satisfying as the sensor was capable to detect different acetone levels in human exhaled breath as non‐invasive diagnosis of diabetes with a good correlation (R2≃0.9) to the routine blood sugar test taken by different commercial glucometers results. [ABSTRACT FROM AUTHOR]

A nanocomposite rod-shaped structure with a single-walled carbon nanotube (SWCNT) embedded in polypyrrole (PPy) doped with nonafluorobutanesulfonic acid (C4F), SWCNT/C4F-PPy, was synthesized using emulsion polymerization. The hybrid ink was then directly coated on a polyimide film interdigitated with the Cu/Ni/Au electrodes via a screen-printing technique to create a flexible film sensor. The sensor film showed a response of 1.72% at 25 °C/atmospheric pressure when acetone gas of 5 ppm was injected, which corresponds to almost 95% compared to the Si wafer-based array interdigitated with the Au electrode. Additionally, C4F was used as a hydrophobic dopant of PPy to improve the stability of humidity and to produce a highly sensitive film-type gas sensor that provides stable detection even in humid conditions. [ABSTRACT FROM AUTHOR]

Recently, precise detection of VOCs in particular acetone, ammonia alcohol has attracted huge attention for industrial safety, monitoring of environment and human health. In this article we have reported for a polypyrrole nanotube (PPNT)‐based chemiresistive sensor for the selective detection of trace acetone vapour at room temperature (25 °C). Polypyrrole (PPy) nanoparticles with different morphologies, viz. nanotubes, nanowire, and globular were synthesized using methyl orange (MO), cetyltrimethyl ammonium bromide (CTAB), and pure polypyrrole as the growth template. The as synthesized powders were exploited to fabricate Taguchi‐type thick‐film sensors. The synthesized powders and fabricated sensors were characterized by multiple sophisticated techniques, such as, XRD, FTIR, Raman spectroscopy, SEM, EDS, UV‐VIS spectroscopy, optical non‐contact profilometry, and current‐Voltage (I‐V) measurement. It is observed that the PPNT sensor shows the highest response to trace acetone vapour with a lower detection limit of 500 ppb at room temperature (25 °C) and quick response (∼5.4 sec) and recovery (∼73.94 sec) times. Achieved enhanced sensing behaviour can be attributed to formation of hydrogen bond between acetone and PPy. Combined with room temperature sensing, good stability, repeatability, produce sensor may find application in various sensing fields. [ABSTRACT FROM AUTHOR]

Highly efficient gas sensors able to detect and identify hazardous gases are crucial for numerous applications. Array of conventional single-output sensors is currently limited by problems including drift, large size, and high cost. Here, we report a sensor with multiple chemiresistive and potentiometric outputs for discriminative gas detection. Such sensor is applicable to a wide range of semiconducting electrodes and solid electrolytes, which allows to tailor and optimize the sensing pattern by tuning the material combination and conditions. The sensor performance is boosted by equipping a mixed-conducting perovskite electrode with reverse potentiometric polarity. A conceptual sensor with dual sensitive electrodes achieves superior three-dimensional (sub)ppm sensing and discrimination of humidity and seven hazardous gases (2-Ethylhexanol, ethanol, acetone, toluene, ammonia, carbon monoxide, and nitrogen dioxide), and enables accurate and early warning of fire hazards. Our findings offer possibilities to design simple, compact, inexpensive, and highly efficient multivariate gas sensors. The application of multivariate gas sensors is limited due to their size and cost. Here the authors developed a compact gas sensor with multiple chemiresistive and potentiometric readouts enabling 3D discriminative response of gases at (sub)ppm levels and used the sensor for early fire detection. [ABSTRACT FROM AUTHOR]

The acetone content in the exhaled breath of individuals as a biomarker of diabetes has become widely studied as a non-invasive means of quantifying blood glucose levels. This calls for development of sensors for the quantitative analysis of trace concentration of acetone, which is presents in the human exhaled breath. Traditional gas detection systems, such as the Gas Chromatography/Mass Spectrometry and several types of chemiresistive sensors are currently being used for this purpose. However, these systems are known to have limitations of size, cost, response time, operating conditions, and consistent accuracy. An ideal breath acetone sensor should provide solutions to overcome the above limitations and provide good stability and reliability. It should be a simple and portable detection system of good sensitivity, selectivity that is low in terms of both cost and power consumption. To achieve this goal, in this paper, we report a new sensing nanomaterial made by nanocomposite, 1D KWO (K2W7O22) nanorods/2D Ti3C2Tx nanosheets, as the key component to design an acetone sensor. The preliminary result exhibits that the new nanocomposite has an improved response to acetone, with 10 times higher sensitivity comparing to KWO-based sensor, much better tolerance of humidity interference and enhanced stability for multiple months. By comparing with other nanomaterials: Ti3C2, KWO, and KWO/Ti3C2Tx nanocomposites with variable ratio of KWO and Ti3C2Tx from 1:1, 1:2, 1:5, 2:1, 4:1, and 9:1, the initial results confirm the potential of the novel KWO/Ti3C2 (2:1) nanocomposite to be an excellent sensing material for application in sensitive and selective detection of breath acetone for diabetics health care and prevention. [ABSTRACT FROM AUTHOR]

A copolymer of pyrrole and o-aminophenol was synthesized by single step oxidative polymerization technique. Two different nanocomposites of copolymer with αFe2O3 and Co-αFe2O3 were prepared and acetone sensing property of both composites were studied at room temperature with different gas concentrations. The calculated sensitivity of the Co-α-Fe2O3 nanocomposite was 0.68 and αFe2O3 nanocomposite was 0.44. The sensitivity of prepared composites was higher than the pure polymer. The LOD of the αFe2O3 composite was found to be 0.13 ppm and Co-αFe2O3 composite was 0.37 ppm. Both the prepared composites have showed excellent selectivity with good repeatability for the acetone gas. The 20% Co-Fe2O3 containing nanocomposite sensor exhibited faster response time of 1.4 s and recovery time of 4.4 s towards the target gas and 15% αFe2O3 containing nanocomposite sensor exhibited the response time of 1.4 s and recovery time of 4.8 s for the acetone gas. The polymer and the nanocomposites have shown excellent repeatability for 7 cycles. The faster response of the sensor can be attributed to the increased number of oxygen vacancies on the sensor as well as the free O H groups present in the polymer back bone. [ABSTRACT FROM AUTHOR]

Nanocomposites of SmFeO3/YFeO3 (1:0, 0.8:0.2, 0.6:0.4, 0.4:0.6, 0.2:0.8, and 0:1) with different molar proportions were prepared by the sol–gel method. The material's properties were characterized by various test methods, such as scanning-electron microscopy (SEM) and X-ray photoelectron-diffraction spectrometry (XPS). The gas-sensing characteristics of the sensor were tested in darkness and under illumination using monochromatic light with various selected wavelengths. The test results show that the SmFeO3/YFeO3 sensor with the molar ratio of 0.4:0.6 had the highest gas response to volatile organic compound (VOC) gases and that the optimum operating temperature was lower (120 °C). The light illumination improved the sensor's sensitivity to gas. Under the 370-nanometer light illumination, the sensor's responses to 30 ppm of ethanol, acetone, and methanol gases were 163.59, 134.02, and 111.637, respectively, which were 1.35, 1.28, and 1.59 times higher, respectively, than those without light. The high gas sensitivity of the sensor was mainly due to the adsorption of oxygen on the material's surface and the formation of a p–p heterojunction. The SmFeO3/YFeO3 sensor, which can respond to different VOC gases, can be used to detect the safety of unknown environments and provide a timely warning of the presence of dangerous gases in working environments. [ABSTRACT FROM AUTHOR]

In view of the low sensitivity, high operating temperature and poor selectivity of acetone measurements, in this paper much effort has been paid to improve the performance of acetone sensors from three aspects: increasing the surface area of the material, improving the surface activity and enhancing gas diffusion. A hierarchical flower-like Pt-doped (1 wt %) 3D porous SnO2 (3DPS) material was synthesized by a one-step hydrothermal method. The micropores of the material were constructed by subsequent annealing. The results of the experiments show that the 3DPS-based sensor's response is strongly dependent on temperature, exhibiting a mountain-like response curve. The maximum sensor sensitivity (Ra/Rg) was found to be as high as 505.7 at a heating temperature of 153 °C and with an exposure to 100 ppm acetone. Additionally, at 153 °C, the sensor still had a response of 2.1 when exposed to 50 ppb acetone gas. The 3DPS-based sensor also has an excellent selectivity for acetone detection. The high sensitivity can be explained by the increase in the specific surface area brought about by the hierarchical flower-like structure, the enhanced surface activity of the noble metal nanoparticles, and the rapid diffusion of free-gas and adsorbed gas molecules caused by the multiple channels of the microporous structure. [ABSTRACT FROM AUTHOR]

• AlGaN/GaN HEMT based polar sensor showing a drain current of 21.2 mA at 3.3 V. • Sensor can detect water with different metal ion contamination and different polar liquids based on their different dipole moments. • Sensor shows easily detectable change in drain current for different polar liquids which lies in range of 100–350 μ A. • Sensor has a sensitivity of 5.98 mA/mm/Debye for detection of polar liquids. In this paper, a GaN-high electron mobility transistor (HEMT) based sensor is designed, fabricated and characterized for polar liquid sensing. The fabricated HEMT sensor chip is packaged by using low temperature co-fired ceramic (LTCC) technique. The sensor shows a typical drain current of 21.2 mA at 3.3 V. The fabricated sensor shows a percentage change of 1.78%, 2.18% and 6.3% in drain current for mercury chloride, copper chloride and sodium chloride respectively with respect to the drain current of pure water. The readout circuit shows a change of 0.15, 0.20 and 0.34 mA in drain current for acetone, water and methanol respectively and ensures the detection of different polar liquids. Due to the novel inter-digital structure, the sensor shows a sensitivity of 5.98 mA/mm/Debye at a drain voltage of 3.3 V. Sensing mainly depends on the dipole moment because the change in the dipole moment of the liquid causes a change in surface potential at the gate sensing area. This paper gives a theoretical and practical perspective on polar liquid detection using both, the sensor and system. [ABSTRACT FROM AUTHOR]

Studying an acetone sensor with prominent sensitivity and selectivity is of great significance for the development of portable diabetes monitoring system. In this paper, cubic-like NiO/ZnO composites with different contents of Ni2+ were successfully synthesized by modifying MOF-5 with Ni2+-doped. The structure and morphology of the prepared composites were characterized by XRD, XPS, and SEM. The experimental results show that the NiO/ZnO composite showed an enhanced gas sensing property to acetone compared to pure ZnO, and the composites showed the maximum response value when Ni2+ loading amount was 5 at%. The response value of the 5% NiO/ZnO composite to acetone (500 ppm) at the optimum operating temperature (340 °C) is 7.3 times as that of pure ZnO. At the same time, the 5% NiO/ZnO composite has excellent selectivity and reproducibility for acetone. The gas sensing mechanism of the heterojunction sensor was described. [ABSTRACT FROM AUTHOR]

Recently, the environmental situation in the world has been deteriorating everywhere and there is a need to find new effective means of detecting harmful substances in the air. Every year, the content of carbon dioxide in the air is growing, which in the end can lead to a deterioration in the health of people. Various types of sensor devices are currently used to timely fix the increase in the gas level. Modern unique materials can be used as the active material of such a sensor: nanotubes, which, due to their sorption properties, are able to detect the presence of harmful impurities in the air space of the premises. It is also possible to use sensors such as detectors of some human diseases by analyzing exhaled air, which makes their use in medicine possible. The results of a theoretical study of the sorption interaction of modified boron-nitride nanotubes (BNNTs) with molecules of carbon dioxide and acetone, obtained using the quantum-chemical DFT method, are presented, which prove the possibility of using this type of nanotube as the sensor material for sensor devices. [ABSTRACT FROM AUTHOR]

This paper reports a study on the enhanced H2 selectivity of SnO2 gas sensors with SiO2 on the surface of the sensors obtained via chemical vapor deposition using dirthoxydimethylsilane as the Si source. The gas sensors were tested for sensing performance towards ethanol, acetone, benzene, and hydrogen at operating temperatures from 150 °C to 400 °C. Our experimental results show that higher selectivity and responses to hydrogen were achieved by the deposition of SiO2 on the surface of the sensors. The sensor with SiO2 deposited on its surface at 500 °C for 8 h exhibited the highest response (Ra/Rg = 144) to 1000 ppm hydrogen at 350 °C, and the sensor with SiO2 deposited on its surface at 600 °C for 4 h attained the maximum response variation coefficient (D = 69.4) to 1000 ppm hydrogen at 200 °C. The mechanism underlying the improvement in sensitivity and the higher responses to hydrogen in the sensors with SiO2 on their surface is also discussed. [ABSTRACT FROM AUTHOR]

In this paper, we successfully prepared Ru-doped Co 3 O 4 flower-like hollow microspheres by a simple hydrothermal method. The microstructure characterization results indicated the formation of well-organized microflowers with a size of 0.5–1 µm, which were composed of nanosheets. The gas sensing performances of sensors by using the synthesized Ru-doped Co 3 O 4 hollow microflowers as sensing material were investigated. The 1 at% Ru-doped Co 3 O 4 sensor showed the best acetone sensing performance and had a response 18.8–10 ppm acetone, which was almost 5.4 times that of pure Co 3 O 4. Significantly, the sensor had an ultra-low detection limit, with a response value of 1.5–50 ppb acetone at 137.5 °C (30%RH). We propose a plausible mechanism for sensing performance improvement. Namely, the substitution of Ru4+ regulated the carrier concentration and induced the change of Co 3 O 4 defect oxygen and chemisorbed oxygen. • Ru-doped Co 3 O 4 flower-like hollow microspheres were synthesized via a facile one-step hydrothermal method. • 1 at% Ru-doped Co 3 O 4 flower-like hollow microspheres exhibited better acetone gas sensing performance. • 1 at% Ru-doped Co 3 O 4 sensor had a response 18.8–10 ppm acetone at 137.5 ℃. • 1 at% Ru-doped Co 3 O 4 sensor had a low detection limit (50 ppb-1.5). [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we described how WO3 microspheres have been synthesized by a simple hydrothermal treatment from the precursor of Na2WO4 and CO (NH2)2 at 160 °C for 3 h. The sample was characterized by X-ray diffraction (XRD), energy dispersive spectrum (EDS), scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), high resolution transmission electronic microscopy (HRTEM), selected area electron diffraction (SAED), and X-ray photoelectron spectroscopy (XPS). Obtained results indicated that the average diameter of the as-prepared WO3 microspheres is ∼1 μm with orthorhombic phase. The WO3 microspheres are constructed of polycrystalline WO3 nanoparticles. The thickness of the WO3 coating of the gas sensor is ∼2 μm. The WO3-based gas sensor exhibited a good sensitivity and high selectivity to acetone vapor at 200 °C. A possible mechanism for the acetone vapor gas sensing was proposed. [Copyright &y& Elsevier]

Abstract: This paper presents a silicon cantilever sensor based on n-type metal–oxide–semiconductor transistor for chemical sensing and analysis using the chemisorption-induced surface stress sensing principle. The cantilever is along the 〈100〉 crystal orientation of the (100) silicon, and the transistor channel is parallel to as well as located at the rear part of the cantilever to obtain high stress sensitivity. The gold film deposited on the bottom surfaces of cantilevers is chemically functionalized with a self-assembled monolayer of 4-mercaptobenzoic acid via the Au–SH covalent bonding. The vapor phase chemical sensing experiments with acetone, ethanol, nitroethane and water vapor as targets are performed. The observed response differentiation implies that the molecular interaction mechanisms between different chemical molecules are different. [Copyright &y& Elsevier]

Abstract: In the present paper, a highly sensitive and selective sensor for acetone was demonstrated, which was based on intensive cataluminescence (CTL) emission on the surface of nano-sized La2O3. The CTL characteristics and the optimum conditions for the sensor, including La2O3 morphology, wavelength, working temperature, and airflow rate, were investigated in detail. Under the optimized conditions, the CTL intensity versus concentration of acetone was linear in the range of 0.19–140μgmL−1, with a correlation coefficient (r) of 0.9981 and a detection limit (signal-to-noise ratio is 3; and noise is the width of baseline) of 0.08μgmL−1. The relative standard deviation (R.S.D.) for 9.3μgmL−1 acetone (n =5) was 1.4%. There was no or weak response to common foreign substances, such as ammonia, toluene, benzene, formaldehyde, ethanol, methanol, ethyl acetate, and acetaldehyde. The gas sensor also exhibited good stability and durability for continuously introducing 19μgmL−1 acetone for 80h over 8 days, with a long-term R.S.D. less than 5%. [Copyright &y& Elsevier]

Nobel metal functionalized chemiresistive type metal-oxide sensors were fabricated and tested against hazardous gases such as acetone, ethanol, hydrogen sulfide, hydrogen cyanide and dimethyl methylphosphonate. WO 3 nanoflakes (NFs) were fabricated on Al 2 O 3 substrates by a facile hydrothermal route. 2D nanoflakes randomly aligned and uniformly covered on the substrate surface, and the thickness of the NFs were found approximately 100 nm. Then, Pt was loaded on WO 3 nanoflakes by RF sputtering method. According to the sensor tests, Pt modification tremendously improved the sensor performance of nanoflakes against acetone gas in terms of sensor response, selectivity among the measured gases and operation temperature. The spillover effect of Pt increased the sensing response and the sensor was able to selectively detect acetone with 237 particle per billion (ppb) at operation temperature of 250 ∘ C. Pt functionalization suppresses the sensor responses of NFs against gases (ethanol, hydrogen sulfide, hydrogen cyanide and dimethyl methylphosphonate) other than acetone. While pristine NFs sensor was able to sense these gases at low temperatures, Pt-functionalized WO 3 NFs did not sense at temperatures lower than 200 ∘ C by giving rise to the selectivity of the sensor against acetone. [ABSTRACT FROM AUTHOR]

The preparation of fast, highly responsive and reliable gas sensing devices for the detection of acetone gas is considered to be a key challenge for the development of accurate disease diagnosis systems through exhaled respiratory gases. In the paper, yolk shell Sb 2 O 3 /WO 3 is synthesized and its gas sensing performance was studied by static test system. Special, the maximum response value of 1:1 Sb 2 O 3 /WO 3 yolk-shell (WO 3 -1 YSL) sensor to 100 ppm acetone can reach as high as 50.0 at 200 ℃. And it also exhibits excellent response/recover time (4 s/5 s), low detection limit (2 ppm) and superior selectivity towards acetone. More importantly, in mixed selective gas test, the sensor shows high selectivity towards acetone. And the mechanism is analyzed by ex-situ XPS. The excellent gas-sensing performance can be attributed to unique yolk-shell structure, which facilitates the rapid transport of charge carriers from the surface to the bulk and provides more active sites for gas adsorption and desorption; the heterojunction between of Sb 2 O 3 and WO 3 , which promotes oxygen pre-adsorption on the surface and increasing the interfacial potential; the increased oxygen vacancies which allowing more chemisorbed oxygen to form. [Display omitted] • The 1:1 Sb 2 O 3 /WO 3 sensor shows fast response/recovery time (4 s/5 s). • Ex-situ XPS technique was used to characterize sensor. • The 1:1 Sb 2 O 3 /WO 3 sensor shows excellent selectivity to acetone. [ABSTRACT FROM AUTHOR]

In this paper, the fabrication of aligned semiconducting single-walled carbon nanotube (SWNT) devices on a thermally grown silicon dioxide (SiO 2) over silicon (Si) substrate is presented. The SWNTs are aligned between the nickel fingers that are patterned on the substrate. Subsequently, the fabricated devices are bonded onto a low-cost printed circuit board (PCB) with wire bonder. The mounted sensors have been tested for carbon dioxide (CO 2) gas, acetone, and isopropyl alcohol (IPA) vapor sensing at room temperature. The sensitivity values of 27% for the concentration of 15000 ​ppm of CO 2 , 52% for the concentration of 7000 ​ppm of acetone, and 67% for the concentration of 900 ​ppm of IPA have been observed with good response and recovery times. The fabricated sensors show better performance than the already reported sensors. [Display omitted] [ABSTRACT FROM AUTHOR]

A conductometric transducer is proposed for the first time for the detection of ethanol vapor. This ethanol microsensor is prepared by encapsulation of alcohol dehydrogenase (ADH) in chitosan. Interdigitated electrodes fabricated by silicon technology were used. The electrodeposition of chitosan allows the addressing of the chitosan film on the microconductometric devices and to encapsulate ADH and nicotinamide adenine dinucleotide (NAD+), which was monitored by FTIR. The analytical performance of the ethanol microsensor was determined in gaseous methanol, ethanol, and acetone samples, collected from the headspace above aqueous solutions of known concentration. The response time (tRec) of the sensor varies from 7 to 21 s from lower concentrations to higher concentrations. The detection limit is 0.12v/v % in the gas phase, corresponding to 0.22 M in the liquid phase. The relative standard deviation for the same sensor is from 12% for lower concentrations to 2% for higher concentrations. The ethanol sensor presents 2.6 times lower sensitivity for methanol and 28.3 times lower sensitivity for acetone. A detection of ethanol in the headspace of a red wine sample lead to an alcohol content in good agreement with the value given by the producer. [ABSTRACT FROM AUTHOR]

Acetone is known as the breath biomarker of diabetes. In this paper we have reported on a highly sensitive, stable cobalt chromite (CoCr 2 O 4) thick film-based trace acetone sensor with quick response and recovery times promising for the detection of diabetes from exhaled breath. CoCr 2 O 4 nanoparticles were prepared by a cost-effective and easy sol-gel method. The as prepared nanoparticles were well characterized by sophisticated characterization techniques, such as, XRD, FESEM. TEM, HRTEM, XPS, and BET. Further these nanoparticles were exploited to fabricate a Taguchi type chemoresistive sensor using a customized drop coater. The developed sensor was characterized by I–V measurement. The developed sensor exhibited high p-type response towards 1 ppm of acetone vapor (~3.81 folds), and appreciable resolution between 1 ppm, 2 ppm (response = ~4.82 folds), and 5 ppm (response = ~6.64 folds) acetone vapor at 300 °C. Further, the sensor exhibited fast response and recovery times of ~1.65 s and ~62 s, respectively. Also, the response of the sensor to 1 ppm acetone vapor is appreciably higher than that of 0.2 ppm ethanol, 0.25 ppm ammonia vapor, and saturated moisture. Finally, the sensor is stable for at least 6 months and exhibits repeatable measurements. Image 1 • Facile sol-gel synthesis of cobalt chromite (CoCr 2 O 4) nanoparticles. • High p-type response to 1 ppm acetone vapor (~3.81 folds). • Appreciable resolution between 1 ppm, 2 ppm, and 5 ppm acetone vapor. • Minimal cross-sensitivities to 0.25 ppm ammonia, 0.2 ppm ethanol, and saturated moisture. • Fast response (~1.65s) and recovery (~62s) times and prolonged stability (≥6 months). [ABSTRACT FROM AUTHOR]

Combination of anti‐resonant hollow‐core fiber (HCF) and semiconductor nanomaterial is an effective strategy to obtain high‐performance gas sensors with exceptional sensitivity and low power consumption. However, controlling the semiconductor morphology onto HCF is a major challenge to achieve the desired gas sensor with the enhanced sensitivity. Here, a ZnO‐Bi2O3 nanosheets (NSs) heterostructure is grown in situ on the surface of HCF by sol–gel and hydrothermal methods. ZnO‐Bi2O3 NSs serving as electron acceptors trap electrons after acetone adsorption and then change the refractive index of the surface of HCF. Benefiting from the unique sheet structure and the synergetic effects for multi‐component, the resulting ZnO‐Bi2O3 NSs enabled HCF gas sensor exhibits high sensitivity, selectivity, and repeatability for detecting acetone at room temperature, particularly in the low concentration range, with the theoretical limit of detection down to 140 parts‐per‐billion. Meanwhile, the successful application of the ZnO‐Bi2O3 NSs enabled HCF gas sensor to distinguish the exhaled breath from the healthy individuals and simulated diabetic cases is demonstrated, which paves the way to achieve non‐invasive, ultra‐sensitivity gas sensing at room temperature for the early diagnosis of diabetes. [ABSTRACT FROM AUTHOR]

As a preliminary drive to eventually develop dye‐sensitized solar cell (DSSC)‐powered gas sensors, many oxide‐based systems have been explored to fabricate sensors that can show response at room temperature for any analyte gas. As an outcome of recent work in this endeavor, a composite nanorod of anatase TiO2 with Na0.23TiO2 is found to exhibit both photovoltaic performance and gas sensing at room temperature as demonstrated here. An interesting morphology change along with a phase change from nanoparticle to nanorod is observed during the hydrothermal synthesis of anatase TiO2 nanoparticles with sodium hydroxide under a highly basic condition. In order to understand the effect of the minor phase Na0.23TiO2 on the inherent properties of anatase TiO2, the application of nanorod composite in two unique potential application areas, DSSC and acetone sensings is investigated. The composite material exhibits an enhanced efficiency of 7.85% for a DSSC. Surprisingly, a resistive sensor fabricated with the synthesized composite material exhibits room temperature p‐type sensing behavior toward different concentrations of acetone (10, 5, 3, 2, and 1 ppm) with high selectivity. [ABSTRACT FROM AUTHOR]

Today, gas sensors offer a vital method to detect and monitor the level, type, and environmental information of various gases in order to guarantee the safety of life in modern civilization. In this regard, the analysis of human breath components is one of the novel applications of analytic gas sensors to monitor the body's metabolism function, which has received a lot of attention. The detection of acetone gas concentration in the exhaled breath is a novel promising method for the diagnosis of diabetes patients in the community health improvement plan. In the present work, a gas sensor based on zinc oxide/copper oxides composite nanostructure (ZCS) has been prepared to meet low-level acetone-sensing requirements. The XRD, FESEM, EDS, and BET analysis confirmed the presence of hexagonal wurtzite ZnO and monoclinic CuO in the composite nanostructure with nanorod morphology. The response, response/recovery time, optimum operating temperature, selectivity, and stability of the sensor were examined in dynamic situations. The results show that the ZCS can efficiently detect low-level acetone concentration. The response and response time obtained around 41.57–60.86%, and 12.6–8.1 s, respectively, toward 0.5–2 ppm target gas at the optimum operating temperature of 90 °C. The possible acetone-sensing mechanism of the ZCS through physicochemical reaction, and applying a standard thermionic emission model on I–V characteristics were discussed in detail. Investigations of temperature and frequency-dependent dielectric parameters of the ZCS were also discussed. The outstanding sensing performance of the ZCS demonstrates that it is a favorable and reliable functional acetone sensor for the monitoring of diabetes at dynamic conditions. [ABSTRACT FROM AUTHOR]

We describe the use of 2-hydroxy-1,4-naphthoquinone (HNQ, Lawsone) as a potential sweat electrolyte measurement marker. We use ultraviolet-visible absorbance measurements to determine the absorbance energy in a particular wavelength range (400 nm-500 nm). This novel approach allows us to eliminate the importance of the exact wavelength of the absorbance peak but find the integral of the range of interest. Although we numerically calculate the absorbance energy, it is imperative to use photodiodes to measure the intensity of the transmitted light that is fabricated particularly for the range of interest for future device implementations. We explored various mixing ratios of water and acetone to find the optimum solvent that would give the most sensitive and accurate relative electrolyte sensing. The pH value was also modified to see the effect on the absorbance energy and intensity. A representative group of subjects were used to collect sweat from the dehydration and hyperhydration cases. The results are convincing that HNQ solutions can be used as a wearable, continuous sweat sensor. [ABSTRACT FROM AUTHOR]

Historically, production of high-performance gas sensing materials has promised to satisfy the worldwide research interests with the increasingly enhanced gas sensor devices. In this paper we are adopting a facile hydrothermal strategy to prepare the ternary FeCo 2 O 4 /graphene hybrid nanocomposites. The spinal phase of FeCo 2 O 4 with spherical shaped morphology was obtained through XRD, SEM and TEM images which confirms. In addition, an average particle size within the range of 30−40 nm was observed for the individual spherical shaped morphology. The Raman and XPS studies also explore the vibration modes and chemical composition of the FeCo 2 O 4 /graphene composites. The BET surface area and BJH pore size of FeCo 2 O 4 /graphene composites is estimated to be 93.2 m2/g and 19.45 nm, respectively. Such high surface area will provide the active path to gas molecules which will increase the efficiency of gas sensing. Measurement of ethanol and acetone gas sensing using clad altered fiber optic sensors and sensitivities for ethanol and acetone gases are 22 and 43 counts/ppm, respectively. Also discussed is the proposed gas sensing mechanism. [ABSTRACT FROM AUTHOR]

• Co 3 O 4 nanoparticle decorated ZnO nanowires are synthesized. • Optimal amount of Co 3 O 4 nanoparticles showing best properties are investigated. • Sub-ppm acetone gas sensing properties are analyzed. • Selectivity of the acetone sensors against other gases is analyzed. (p)-Co3O4 nanoparticle-decorated (n)-ZnO nanowires were synthesized by two step process. ZnO nanowires and Co3O4 nanoparitcles were synthesized using a vapor-liquid-solid method and hydrothermal method, respectively. To decorate Co3O4 nanoparticles on ZnO nanowires, several amount of Co3O4 nanoparticle-suspended solution was dropped to ZnO nanowires, and this process was repeated to several times to find optimum amount of Co3O4 nanoparticles. As a result, Gas sensing response of ZnO nanowire-based sensor presented 1.73, 2.44, 3.07, 4.09, and 5.13 when exposed to 0.1 ppm, 0.5 ppm 1 ppm, 5 ppm, and 10 ppm acetone gas, respectively, whereas presented 5.38, 10.1, 15.81, 31.85, and 43.86 in case of three times of Co3O4 nanoparticle-decorated ZnO nanowire-based sensor to exposed to same condition of gas. In this paper, detailed method for synthesis of (p)-Co3O4 nanoparticle-decorated (n)-ZnO nanowires were introduced, and its enhanced acetone sensing mechanisms followed by decoration of optimum amount of Co3O4 nanoparticles on ZnO nanowires were discussed. [ABSTRACT FROM AUTHOR]

The authors report the fabrication and characterization of chemiresistive sensors, composed of a thermoplastic elastomer (TPE), styrene‐ethylene‐ran‐butylene‐styrene, and a high‐structure carbon black (CB) targeted for detecting hydrocarbons at or near room‐temperature (RT). The sensors are fabricated via drop‐on‐demand inkjet‐printing (IJP) for which jettable inks are formulated and their printability systematically studied as a function of different ink components, that is, polymer concentration, solvent mixture, and CB dispersion. The printed sensors are characterized upon exposure to various analytes showing a high sensitivity to nonpolar compounds (pentane, heptane), moderate sensitivity to polar aprotic analytes (acetone), low sensitivity to polar protic analytes (ethanol), and almost no sensitivity to humidity. While operating at 28 °C, the sensors have a fast response and recovery (a few seconds) owing to the rapid analyte diffusion into the TPE. Moreover, it is shown that the sensor response and recovery further improve without affecting the sensitivity by increasing the droplet spacing in the printed film. Such performance demonstrates the great potential of TPE‐based nanocomposites for RT detection of volatile organic compounds and IJP as a suitable manufacturing method for integrating the sensing material with the electronic devices in applications where low‐cost sensors with low power consumption are required. [ABSTRACT FROM AUTHOR]

• One-dimensional SnO 2 and a series of Ru-doped SnO 2 nanostructures were synthesized by electrospinning. • The grain size of the SnO 2 nanocrystal were greatly decreased by Ru doping. • The sensors based on 2 mol% Ru-doped SnO 2 nanofibers showed greatly enhanced gas sensing performance. • The detection limit for acetone gas of the SnO 2 sensor was reduced after 2 mol% Ru doping. We report the Ru doping effect on the gas-sensing properties of SnO 2 nanofibers for acetone detection in this paper. For this purpose, pure and 1, 2, 3 mol% Ru-doped SnO 2 nanofibers were prepared through electrospinning technique combined with calcination treatment. The fibrous microstructure of these nanofibers were maintained and the grain size of the SnO 2 nanoparticals were decreased from 9.2 nm (pure) to 5.1 nm (3% Ru-doped) after Ru doping. In order to confirm that Ru doping is an effective way to improve the gas sensing properties of the SnO 2 -based gas sensor, the gas sensing properties of the sensors based on pure and Ru doped SnO 2 nanofibers were investigated systematically. The results showed that the response to 100 ppm acetone of 2 mol% Ru-doped SnO 2 nanofibers was 118.8, which was 12 times higher than that of pure SnO 2 nanofibers. In the end, the role of Ru in the gas sensing mechanism of SnO 2 nanofibers was analyzed according to the results of the X-ray photoelectron spectroscopy (XPS) and Ultraviolet photoelectron spectroscopy (UPS). [ABSTRACT FROM AUTHOR]

Detection of acetone gas embraces a broad range of purposes. It encompasses medical application for healthcare, serving as an alternative for conventional diagnosis of diabetes as well as aiding in environmental monitoring. Thus, a comprehensive understanding of recent development for chemiresistive acetone gas sensors is essential to ensure rapid progression is upheld in the future. The objectives of this review are to assess state-of-the-art of chemiresistive sensors for acetone gas detection and to identify factors affecting performance of the sensors which could bring about sensing developments. For these purposes, sensing characteristics entailing limit of detection, response and recovery time, stability as well as factors affecting sensing mechanisms are discussed thoroughly in the paper. This review informs readers about deficiencies that majority of gas sensors are still facing to date. Recognizing the shortcomings would encourage improvements on detection of acetone gas in the future. [ABSTRACT FROM AUTHOR]