Ppm Ethanol Research Articles

The SnO2/MXene Composite Ethanol Sensor Based on MEMS Platform

In recent years, two-dimensional layered material MXene has attracted extensive attention in the fields of sensors due to its large specific surface area and rich active sites. So, we employed multilayer Ti3C2TX and SnO2 microspheres to prepare SnO2/MXene composites for enhancing gas-sensing properties of pristine SnO2. The composite was brushed on a microelectromechanical system (MEMS) platform to make resistance-type gas sensors with low power consumption. The gas-sensing results show that the SnO2/MXene sensor with the best composite ratio (SnO2: MXene mass ratio is 5:1, named SM-5) greatly improves gas sensitivity of SnO2 sensor, among which the sensitivity to ethanol gas is the highest. At the same time, the composite also speeds up the response recovery speed of the sensor. When the SM-5 sensor worked at its optimal temperature 230 °C, its response value to 10 ppm ethanol reaches 5.0, which is twice that of the pristine SnO2 sensor. Its response and recovery time are only 14 s and 26 s, respectively. The sensing mechanism of the composite is discussed according to the classical the space charge or depletion layer model. It is concluded that the Schottky barrier of composites and the metal properties of Ti3C2Tx are responsible for improvement of the gas-sensing properties of the composite.

Hydrothermal synthesis of hollow CoSnO3 nanocubes for highly response and selective ethanol gas sensing

In this work, the CoSnO3 nanocubes with p-type semiconductor feature was synthesized via a hydrothermal method. The chemical composition, morphology, and structure of CoSnO3 were characterized by XRD, BET, SEM, TEM and XPS. The CoSnO3 exhibited excellent gas sensing performance to 30 ppm ethanol, including high gas response (22.5), low operating temperature (210℃) and response-recovery time (45 s, 44 s). The prepared CoSnO3 could be used as a promising gas sensing material to detect ethanol.

MOFs-derived Co-doped In2O3 hollow hexagonal cylinder for selective detection of ethanol

Shape controlled preparation and doping are important means to improve the gas sensitivity of metal oxide semiconductor materials. In this work, pure and Co-doped In2O3 porous hollow hexagonal cylinders were successfully prepared using metal–organic frameworks (MOFs) MIL-68(In) as self-sacrificial template. The size of the MIL-68(In) hexagonal cylinder is uniform, and the In2O3 obtained after pyrolysis better inherits the shape of the MIL-68(In), but becomes hollow, and the cylinder surfaces are porous. The product has a large specific surface area (46.52 m2/g), and the doping of Co significantly increases the oxygen vacancy of the material. The Co-doped sample obtained by pyrolysis at 500℃ has excellent gas sensing performances to ethanol gas, its sensitivity to 100 ppm ethanol gas at 210 ℃ is 14.6, response/recovery time is 21 s and 107 s, and the sensing selectivity to ethanol is also good.

The detection of ethanol vapors based on a p-type gas sensor fabricated from heterojunction MoS2–NiCo2O4

In this paper, the hydrothermally synthesized nanocomposites (MoS2–NiCo2O4) were exploited to detect various volatile organic compounds (VOCs). Some characterizations such as XRD, Raman, N2 adsorption-desorption isotherms, SEM, EDS and XPS were explored to identify the structure and morphology of these materials. More importantly, different sensors were designed from synthesized nanocomposites to see their sensing performance to various VOCs. Among these sensors, the sensor of MNCO-6 (6 mL MoS2 decorated with NiCo2O4) detected the highest response to 100 ppm ethanol while an insignificant response to other VOCs was noticed; moreover, good repeatability and response/recovery time (15/6 s), the response (1.63) to 0.1 ppm ethanol was also distinguished.

Enhanced ethanol gas sensing properties of hierarchical porous SnO2-ZnO microspheres at low working temperature

In this work, the hierarchical porous SnO2-ZnO microspheres have been successfully synthesized by hydrothermal method followed by calcination. The structure, chemical composition, specific surface area and morphology of as-synthesized samples were detailed characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy (PL), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. The results indicate that the response of hierarchical porous SnO2-ZnO microspheres-based sensor toward 100 ppm ethanol is 74 at low working temperature (225 °C), which is higher than that of pure hierarchical porous ZnO microspheres-based sensor (39). Moreover, the hierarchical porous SnO2-ZnO microspheres-based sensor presents fast response and recovery time (4 s, 6 s), good selectivity, repeatability and stability. Therefore, the sensor based on hierarchical porous SnO2-ZnO microspheres will be a potential candidate for ethanol detection.

Bimetallic AgAualloy@ZnO core-shell nanoparticles for ultra-high detection of ethanol: Potential impact of alloy composition on sensing performance

The detection/sensing properties of chemiresistive gas sensors are greatly improved by catalytically triggered bimetallic alloyed nanoparticles, because of their synergistic effect. In this work, well-defined AgAualloy@ZnO core-shell nanoparticles are synthesized with the various compositions of Ag and Au. Alloying Au with Ag gave superior thermal stability to Ag, which favored gas sensing performance. As the amount of Ag within the AgAualloy core increased, the optimum working temperature was lowered to 300 ℃ with the dramatically enhanced ultra-high response of 1755 was obtained for Ag70Au30 @ZnO NPs sensor to 100 ppm ethanol. The outstanding sensing performance of AgAualloy@ZnO were endorsed to the improved the electronic and catalytic properties of AgAualloy core, aplenty chemisorbed oxygen on the surface of ZnO, unique core-shell structure that bring large active surface area and enhanced electron transfer process at the interface between core and shell. Ultraviolet photoelectron spectroscopy (UPS) analysis shows that with increasing Ag concentration, the work function (ϕ) decreases and the chemisorbed oxygen increases that brings wider depletion layer and Schottky barrier between the AgAualloy core and the ZnO shell, enhancing the gas sensing response. Our findings suggest that the incorporation of noble metal alloy-metal oxide semiconductor based core-shell nanostructures enhance the gas sensing performance with selectivity in the practical field of applications in environmental issues and human health monitoring.

Highly sensitive and low detection limit of ethanol gas sensor based on CeO2 nanodot-decorated ZnSnO3 hollow microspheres

In order to achieve high response, excellent selectivity and stable detection of ethanol vapor, CeO2 nanodot-decorated ZnSnO3 hollow microspheres with heterostructures that could meet the requirements of ethanol detection were obtained through a convenient hydrothermal method. The prepared uniform nanodot-decorated hollow microspheres were observed by SEM and TEM, it is noticeable that CeO2 nanodots of about 10 nm were uniformly anchored on the surface of ZnSnO3 hollow microspheres with a diameter of 0.8–1.4 μm. Compared with the pure ZnSnO3, the 15% CeO2/ZnSnO3 hollow microspheres exhibited higher response (219.2) to 100 ppm ethanol, superior selectivity (ethanol) and rapid response recovery. In addition, a scientific and effective method was used to calculate the ultra-low theoretical gas detection limit (11.3 ppb) of the CeO2 nanodot-decorated ZnSnO3 hollow microspheres. The outstanding gas sensing properties were attributed to the existence of large amounts of dissociative oxygen and the n-n heterojunction between ZnSnO3 and CeO2. Meanwhile, our work confirmed that CeO2 nanodot-decorated ZnSnO3 hollow microspheres have satisfied the application needs of ethanol detection.

Low Mass Flux Laminar Jet Cooling with Different Additives: An Enhancement-cum-Comparative Study

The low flow rate laminar water jet is the most economical and efficient cooling methodology; however, the low heat removal capacity makes this process inappropriate for fast cooling operations. In the current work, the heat transfer rate has been increased by enlarging the stagnation zone length. This was attained by reducing the viscosity, surface tension and altering other thermo-physical properties of the coolants. The thermal analysis reveals that the maximum critical heat flux is achieved in case of 240 ppm Cetyltrimethylammonium bromide + water i.e., 1.7 MW/m2, which is 1.39 times higher than pure water. This is attributed to the significant reduction in the surface tension and viscosity. Use of additives like sodium carbonate and surfactant enhance the stagnation zone length. Furthermore, due to foaming nature of the coolant (500 ppm Ethanol + water), the heat transfer rate declines and a critical heat flux of 1.37 MW/m2 is observed. The visual observations are consistent with the results obtained for each coolant. Based on the high heat removal capacity, the low mass flux laminar jet cooling methodology with additives provide better cooling than that of the high-pressure laminar jet and high mass flux spray cooling.

High Sensitivity, Humidity-Independent Ethanol Gas Sensors Based on PFDS-ZnSnO₃ Hollow Microsphere

Breath analysis using gas sensors to detect disease-related exhaled breath for diagnosing human health has huge application potential. However, the humidity changing in both the surrounding environment and exhaled breath have great damage to the actual sensing results, so the humidity dependence of gas sensor is a major obstacle to breath analysis applications. Here, 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (PFDS) is used to hydrophobic the prepared ZnSnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> sensor to obtain a high sensitivity and humidity-independent ethanol sensor for breath analysis. The ethanol sensing characteristics of PFDS-treated sensors were studied under dry and high humidity (RH (relative humidity) = 80%) conditions. The response value of pure ZnSnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> sensor to ethanol dropped from 33.7 to 3.2 as the condition change form dry to 80% RH. On the contrary, the response of the 3h PFDS-ZnSnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> sensor to 100 ppm ethanol was 7.5 under 80% RH, which was basically the same as the response (7.3) under dry conditions, indicating the same sensing behavior under dry and humidity conditions without being affected by moisture. In addition, the PFDS-ZnSnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> sensors ignore the interference of other volatile gases under dry and humid conditions, while maintaining excellent selectivity to ethanol. The humidity-independent properties are attributed to the fact that PFDS with low-energy groups make the sensor surface hydrophobic, thus the material resists the contact of water molecules with the sensor and competition with ethanol in the gas response. Therefore, regardless of humidity fluctuations, the sensor shows great practicability in detecting ethanol and could be used for medical breath analysis.

Highly sensitive ethanol and acetone gas sensors with reduced working temperature based on Sr-doped BiFeO3 nanomaterial

An effective method to prolong the use time and long-term stability of gas sensors is by lowering the working temperature. However, reducing the working temperature and increasing the sensitivity of a gas sensor is essential to enhance gas-sensing performance. In this work, Sr-doped ferrite bismuth nanomaterial has been synthesized by the facile sol–gel method and their surface morphology, microstructure, and surface chemical composition were characterized. Sr-doped ferrite bismuth is a single-phase nanomaterial with about 50 nm average grain size and rhombohedral crystal structure (Space Group R 3c). The gas-sensing results show that Sr dopant can significantly enhance the sensitivity and reduce the working temperature. Furthermore, the optimum working temperature of Sr-doped BiFeO3 sensor reduces from 244 °C to 208 °C. At the optimum working temperature (208 °C), Sr-doped BiFeO3 gas sensor's sensitivities to 200 ppm ethanol and acetone are nearly the same value (49.5), which are respectively 1.3 and 1.4 times more than BiFeO3 gas sensor at 244 °C. A related gas-sensing mechanism is also discussed.

Synthesis of ZnO@In2O3 heterojunction with unique hexagonal three-dimensional structure for ultra sensitive ethanol detection

The unique interface barrier characteristics of heterojunction have a significant impact on the gas sensing properties of composites. In this work, we report the successful synthesis of ZnO@In2O3 heterojunction nanocomposites with ultra sensitive response to ethanol by simple hydrothermal method and subsequent annealing treatment. SEM, TEM, XRD and other morphological characterization methods were used to detect the composites. Through the analysis of the characterization results, it can be found that the special structure of heterojunction is a three-dimensional structure which composed of ZnO hexagonal nanosheets and surface attached In2O3 nanoparticles, with a specific surface area of 63.27 m2/g. Measurements show that diameter of the nanosheets is 200–300 nm, the thickness is 40–60 nm, and the particle size of In2O3 nanoparticle is 30–60 nm. Due to the unique hexagonal three-dimensional structure, large specific surface area and rich mesoporous structure, gas sensing test results of the sensor prepared through ZnO@In2O3 heterojunction present that response value to 100 ppm ethanol at 160 °C is 28.6, which is much higher than pure ZnO and In2O3; It also presents the ability of rapid ethanol detection (response and recovery time are 8 s and 17 s); The synthesis of unique heterojunction structure greatly improves the sensitivity to ethanol, lower operating temperature significantly reduces energy consumption, and the repeatability and stability of sensors also perform excellent. Above advantages confirm that ZnO@In2O3 heterojunction nanocomposite is one of the ideal materials for rapid ethanol detection.

Breath Analysis for the In Vivo Detection of Diabetic Ketoacidosis.

Human breath analysis of volatile organic compounds has gained significant attention recently because of its rapid and noninvasive potential to detect various metabolic diseases. The detection of ketones in the breath and blood is key to diagnosing and managing diabetic ketoacidosis (DKA) in patients with type 1 diabetes. It may also be of increasing importance to detect euglycemic ketoacidosis in patients with type 1 or type 2 diabetes or heart failure, treated with sodium-glucose transporter-2 inhibitors (SGLT2-i). The present research evaluates the efficiency of colorimetry for detecting acetone and ethanol in exhaled human breath with the response time, pH effect, temperature effect, concentration effect, and selectivity of dyes. Using the proposed multidye system, we obtained a detection limit of 0.0217 ppm for acetone and 0.029 ppm for ethanol in the detection range of 0.05–50 ppm. A smartphone-assisted unit consisting of a portable colorimetric device was used to detect relative red/green/blue values within 60 s of the interface for practical and real-time application. The developed method could be used for rapid, low-cost detection of ketones in patients with type 1 diabetes and DKA and patients with type 1 or type 2 diabetes or heart failure treated with SGLT2-I and euglycemic ketoacidosis.

Electrospun ZnSnO3/ZnO Composite Nanofibers and Its Ethanol-Sensitive Properties

In this work, a novel heterojunction based on ZnSnO3/ZnO nanofibers was prepared by a simple electrospinning method. The crystal, structural, and surface compositional properties of ZnSnO3 and ZnSnO3/ZnO composite nanofibers were investigated by X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectrometer (XPS), and Brunauer–Emmett–Teller (BET). Compared to pure ZnSnO3 nanofibers, the ZnSnO3/ZnO heterostructure nanofibers had high sensitivity and selectivity response with the fast response toward ethanol gas at low operational temperature. The sensing response of the sensor based on ZnSnO3/ZnO composite nanofibers was 19.6 toward 50 ppm ethanol gas at 225 °C, which was about 1.5 times superior to that of pure ZnSnO3 nanofibers. It can be owed mainly to the oxygen vacancies and the synergistic effect between ZnSnO3 and ZnO.

Glucose-assisted combustion synthesis of oxygen vacancy enriched α-MoO3 for ethanol sensing

The α-MoO3-based materials have been intensively investigated as chemiresistive-type gas sensors due to their excellent sensing performances for gas sensing applications. However, there still remains formidable challenges for developing a simple and scalable approach to synthesize α-MoO3 with controllable structures. Herein, we demonstrated a glucose-assisted combustion synthesis strategy for the synthesis of α-MoO3 materials with controllable structures. They were obtained by heat treatment of the gels containing ammonium heptamolybdate tetrahydrate and glucose. Owing to the coordination interactions between glucose and heptamolybdate, α-MoO3-2 sample obtained by adding 1.8 g of glucose featured the highest oxygen vacancy concentration with an O/Mo atomic ratio of 2.61. The gas sensing measurements indicated that α-MoO3-2 had excellent sensing performances for detecting ethanol. Such ethanol sensor displayed the lowest detection concentration of 5 ppm ethanol, high response of 3.86 toward 20 ppm ethanol, and wide detection range of 5–100 ppm. This study sheds light on preparation of metal oxides with controllable structures on a scalable way for various applications.

Highly sensitive and fast-response ethanol sensing of porous Co3O4 hollow polyhedra via palladium reined spillover effect

Highly sensitive and fast detection of volatile organic compounds (VOCs) in industrial and living environments is an urgent need. The combination of distinctive structure and noble metal modification is an important strategy to achieve high-performance gas sensing materials. In addition, it is urgent to clarify the chemical state and function of noble metals on the surface of the sensing material during the actual sensing process. In this work, Pd modified Co3O4 hollow polyhedral (Pd/Co3O4 HP) is developed through one-step pyrolysis of a Pd doped MOF precursor. At an operating temperature of 150 °C, the Pd/Co3O4 HP gas sensor can achieve 1.6 times higher sensitivity than that of Co3O4 HP along with fast response (12 s) and recovery speed (25 s) for 100 ppm ethanol vapor. Near-ambient pressure X-ray photoelectron spectroscopy (NAPXPS) was used to monitor the dynamic changes in the surface state of Pd/Co3O4 HP. The NAPXPS results reveal that the oxidation and reduction of Pd in the ethanol sensing process are attributed to a spillover effect of oxygen and ethanol, respectively. This work opens up an effective approach to investigate spillover effects in a sensing mechanism of noble metal modified oxide semiconductor sensors.

Hierarchical mesoporous zinc oxide microspheres for ethanol gas sensor

The increasing demand for hazardous gas detections has triggered the enormous efforts for the development of mesoporous materials for gas sensors. Especially, a universal method to synthesize such structure for semiconductor oxides is highly desirable. In this work, ZnO microspheres assembled by mesoporous nanosheets are prepared via a one-step hydrothermal method successfully. It is found that the morphology of ZnO and the thickness of ZnO mesoporous nanosheets, which affect the gas sensing response to ethanol, can be regulated by adjusting the amount of PVP. In addition, this method is also suitable for the synthesis of NiO, CuO and Co3O4 mesoporous nanosheets and the repeatability is excellent. Gas sensing investigation indicates that the gas sensors based on mesoporous ZnO nanospheres synthesized with 3.3 g PVP have the highest response (~58.4) to 100 ppm ethanol at 250°C, which is about 9.4 times higher than that of the ZnO nanosheets obtained without PVP under the same test conditions (~6.2). Furthermore, the detection limit could reach the ppb level with the response of 1.17–500 ppb ethanol. The possible mechanism of the formed structures and the enhanced ethanol sensing properties are discussed systematically.

CdS Micrometer Hollow Spheres for Detecting Alcohols Except Methanol with Strong Anti-interference Ability.

Cadmium sulfide micrometer hollow spheres (CdS MHs) were fabricated by a hydrothermal method. The performance of the CdS MHs sensor was evaluated by detecting volatile organic compounds such as methanol, ethanol, 1-propanol, isopropanol, n-butanol, iso-butyl alcohol, iso-amyl alcohol, acetone, and xylene. It was found that the optimum working temperature of the CdS MHs sensor is 190 °C. The response of the CdS MHs can reach 27.4–100 ppm ethanol and reach 84.55–100 ppm isopropanol. Comparing the response to pure 5 ppm isopropanol (iso-amyl alcohol) with the mixture of 5 ppm isopropanol (iso-amyl alcohol) and 50 ppm acetone or 5 ppm isopropanol (iso-amyl alcohol) and 50 ppm methanol, the relative deviation was −1.33% (−7.11%) or −6.19% (9.20%). It suggested that the CdS MHs sensor had a strong anti-interference ability to methanol and acetone and is suitable for detecting alcohols except methanol. Therefore, the CdS MHs sensor had good response and is a promising alcohol detection material.

High performance ethanol sensor based on Pr-SnO2/In2O3 composite

Metal-organic framework (MOF) can be used as sacrificial templates for preparing metal oxides with unique hollow structures. The heterojunction formed between two metal oxides is conducive to improvement of gas sensor performance. Herein, MOF compounds containing In with hexagonal prism morphology were synthesized first, and then annealed to obtain uniform hexagonal In2O3 hollow microtubes. Subsequently, the surface of In2O3 hollow microtubes was decorated by the Pr-doped SnO2 nanoparticles (NPs) in solution under stirring, and the Pr-SnO2/In2O3 composite was obtained. Various characterization techniques confirmed the successful preparation of the Pr-SnO2 NPs/In2O3 composite. The specific surface area of the composite reached 72.07 m2/g. The sensing performance of the SnO2, Pr-SnO2, In2O3, SnO2/In2O3, and Pr-SnO2/In2O3 sensors to ethanol gas were systematically investigated. Among these sensors, at the optimal working temperature, the Pr-SnO2/In2O3 sensor displayed the best sensing performance with a response value of 75 towards 50 ppm ethanol, and further exhibited good linearity coefficient, selectivity, reproducibility, and long-term stability.

Amplifying the receptor function on Ba0.9La0.1FeO3-SnO2 composite particle surface for high sensitivity toward ethanol gas sensing

Composite particles of Ba0.9La0.1FeO3 (BLF) and SnO2 have been designed to amplify the receptor function of semiconductor gas sensor and achieve high sensitivity toward volatile organic compound gases. During operation, the sensor was driven under double-pulse mode (DP-mode) that includes high-temperature preheating. According to the temperature programmed desorption measurement, oxygen desorption from the BLF-SnO2 composite occurred at lower temperatures than that from SnO2, and the amount of oxygen desorption was also larger. Under the DP-mode, the electrical resistance of BLF-SnO2 was significantly higher than that of SnO2, because BLF acted as an oxygen supplier to increase effective oxygen concentration in the sensing layer. In addition, temperature programmed reaction measurement revealed that ethanol desorbed from BLF, and that the total amount of ethanol desorption and combustion on BLF-SnO2 was larger than that on SnO2. Thus, the sensor response to ethanol based on ethanol combustion reaction was enhanced when using BLF-SnO2 under the DP-mode, especially the sensor response to 1 ppm ethanol showed 143 at the preheating and measurement temperatures of 400 °C and 250 °C, respectively. This enhanced response was attributed to the condensation of oxygen and ethanol under the DP-mode, with BLF playing the role of oxygen and ethanol provider. Thus, compositing BLF with SnO2 significantly amplified the receptor function of the sensing material, and such materials design could lead to improved sensitivity.

Flexible Impedimetric Electronic Nose for High-Accurate Determination of Individual Volatile Organic Compounds by Tuning the Graphene Sensitive Properties

We investigated functionalized graphene materials to create highly sensitive sensors for volatile organic compounds (VOCs) such as formaldehyde, methanol, ethanol, acetone, and isopropanol. First, we prepared VOC-sensitive films consisting of mechanically exfoliated graphene (eG) and chemical graphene oxide (GO), which have different concentrations of structural defects. We deposited the films on silver interdigitated electrodes on Kapton substrate and submitted them to thermal treatment. Next, we measured the sensitive properties of the resulting sensors towards specific VOCs by impedance spectroscopy. We obtained the eG- and GO-based electronic nose composed of two eG films- and four GO film-based sensors with variable sensitivity to individual VOCs. The smallest relative change in impedance was 5% for the sensor based on eG film annealed at 180 °C toward 10 ppm formaldehyde, whereas the highest relative change was 257% for the sensor based on two-layers deposited GO film annealed at 200 °C toward 80 ppm ethanol. At 10 ppm VOC, the GO film-based sensors were sensitive enough to distinguish between individual VOCs, which implied excellent selectivity, as confirmed by Principle Component Analysis (PCA). According to a PCA-Support Vector Machine-based signal processing method, the electronic nose provided identification accuracy of 100% for individual VOCs. The proposed electronic nose can be used to detect multiple VOCs selectively because each sensor is sensitive to VOCs and has significant cross-selectivity to others.