Ppm Ethanol Research Articles

Synthesis of Calcium Ferrite by Inherent Source for Ethanol Sensor

AbstractIn this work, CaFe2O4 is successfully synthesized with a natural source of precursors by the milling method. The X‐ray diffraction confirms the orthorhombic CaFe2O4 compound. Scanning electron microscopy shows agglomerated porous crystalline type morphology. Photoluminescence spectra show that CaFe2O4 absorbs visible regain at wavelength 584 nm. The synthesized CaFe2O4 compound shows p‐type gas sensing behavior and high gas response towards ethanol 38.4% at 225˚C operating temperature at a concentration of 120 ppm ethanol gas.

Optimal Pt mesoporous layer modified nanocomposite film with highly sensitive detection of ethanol at low temperature

Developing highly sensitive and selective gas sensing MOS materials with low working temperature is urgent to fabricate high-performance ethanol gas sensors. Herein, we report a Pt mesoporous layer modified multi-layer TiO2/SnO2 nanocomposite thin film for improving sensitivity and selectivity of detecting ethanol at a low temperature. The Pt mesoporous layer is prepared by simple sputtering techniques, which are completely compatible with the MEMS process. The characterization results show the Pt sputtering time of 30 s and the annealing temperature of 500℃ are the opening condition and forming condition of Pt mesoporous layer, respectively, which has the most mesoporous of 5–50 nm. Because the Pt mesoporous layer has copious mesoporous and there is an abundant Schottky barrier between Pt and TiO2, the thin film (optimal parameters: 30 s, 500℃) based sensor has the highest sensitivity to ethanol at 130 ℃ and its response is as high as 3.32 to 0.1 ppm of ethanol, so the thin film is regarded as the optimal Pt mesoporous layer. Thus, the Pt mesoporous layer on the multi-layer TiO2/SnO2 nanocomposite thin film prepared by sputtering techniques is a simple but effective method to largely improve the gas sensing properties of the nanocomposite film.

Nanocrystalline spinel zinc-substituted cobalt ferrite thick film an efficient ethanol sensor

This study considered Zn-substituted cobalt ferrite (ZnxCo1-xFe2O4 (x = 0.0–1.0) (ZCF)) thick films structural, morphological, and electrical properties; and gas sensing performance. The ZCF thick film sensor was screen printed on a glass substrate and tested for different analyte gases, including H2, H2S, CO2, Cl2, NH3, LPG, and C2H5OH. We used X-ray photoelectron spectrometry to investigate composition, chemical state, iron/cobalt or zinc ratio, and cation distribution within Zn-substituted cobalt spinel ferrite tetrahedral and octahedral sites without impurities. FESEM and HR-TEM confirmed grain dimensions between 0.13 and 0.23 μm and porous, nearly spherical to flake-like morphology for the ZCF samples. Sample DC resistivity reduced with increasing temperature, confirming semiconductor nature. Thick film ZCF composition achieved highest the gas response and selectivity to 100 ppm ethanol at room temperature (30 °C). Overall results confirmed that flake-like ZCF sensors could be effective ethanol gas sensors.

Synthesis, characterization, and gas-sensing properties of macroporous Ag/SnO2 composite by a template method

Macroporous SnO2 (M − SnO2) materials with high specific surface area were synthesized by template method. In order to further improve the gas sensing performance of the sensor, Ag modified macroporous SnO2 (M-Ag/SnO2) gas sensing materials were finally prepared. The morphology, valence state and crystal structure of the samples were characterized by SEM, XRD, TEM, UV–Vis and XPS. The characterization results indicated that the macroporous gas sensing materials were successfully synthesized, and there were Ag nanoparticles in the samples. The gas sensing test showed that, compared with pure SnO2 (180), the gas sensitive response value of M − SnO2 with high specific surface area is 600, which is about 3.33 times than that of pure SnO2. Moreover, M-Ag/SnO2 sensor exhibits higher response value (830) to 10000 ppm ethanol gas at 260 °C, which was 4.61 times higher than that of pure SnO2 nanoparticles. This outstanding gas sensing properties are derived from the high specific surface area and catalytic activity of the M-Ag/SnO2 materials. More importantly, the great reversibility and repeatability of the material makes it have a broad application prospect in designing high performance ethanol sensors.

Synthesis of FeVO4 Nanoparticles and Sensing Performance for Ethanol Gas under Different Solution pH

AbstractFeVO4 nanoparticles are synthesized by the hydrothermal method. The effect of micromorphology under different pH conditions is investigated. Their microstructure, morphology, and chemical composition are analyzed by X‐ray diffraction (XRD), scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), Raman spectroscopy, and N2 adsorption–desorption. The results showed that an increase in pH leads to agglomeration of the material. The effect of different pH conditions on the gas‐sensitive performance of FeVO4 is subsequently investigated, and the best response performance of the FeVO4 sensor is achieved at a pH of 3. The consequences showed that the FeVO4 sensor has a response of 3.383 to 100 ppm ethanol gas, with the response and recovery time of 1 and 7 s. The response cycle test has proved that FeVO4 has good stability. Analyzed in conjunction with the characterization results, the oxygen vacancies on the surface of the nanoparticles not only improve the electronic conductivity but also provide active sites for the adsorption of gases, which helps to improve the sensitivity of the material to gases.

Selective ethanol sensor based on α-Fe2O3 nanoparticles

In this study, p-type α-Fe2O3 nanoparticles (NPs) were synthesized through a Pechini sol-gel method for gas sensing studies. Different characterization methods such as X-ray diffraction, Fourier transform-infrared spectroscopy and scanning electron microscopy were used to study the crystallinity, functional groups and morphology of the synthesized powers, respectively. The gas sensor was fabricated and gas sensing properties of α-Fe2O3 NPs were evaluated towards ethanol vapor and other gases. The sensor showed a p-type semiconducting behavior, based on the resistance variations in the presence of reducing gases. At optimized sensing temperature of 150 °C, it showed a response [(△R/Ra) × 100] of 14.5% to 100 ppm ethanol gas, along with good selectivity to this gas. The sensing mechanism is discussed in details.

Uji Aktivitas Sitotoksik Fraksi Daun Matoa (Pometia pinnata) dengan Metode Brine Shrimp Lethality Test (BSLT)

Matoa (Pometia pinnata) is parts of Sapindaceae family widely spread in tropical areas, especially in Papua. Several studies mentioned the use of its parts as antioxidants and contain phenolic compounds and flavonoids. This study aim(s) to conduct a phytochemical screening test as well as a cytotoxic test for Pometia pinnata leaves fraction using the BSLT method. The research series began with the extraction process using 96% ethanol, then fractionated using three solvent variations: n-hexane, ethyl acetate, and ethanol. Further, the phytochemical screening test was carried out for cytotoxic testing in order to see the mortality rate of shrimp larvae Artemia salina Leach. The result of the phytochemical showed that the secondary metabolite compounds on the ethanol and ethyl acetate fraction were alkaloids, flavonoids, saponins, tannins, and terpenoids compounds meanwhile the n-hexane fraction contained terpenoids. The results of cytotoxic testing BSLT showed the LC50 value in the n-hexane was 7029.10 ppm, 406.07 ppm for ethyl acetate and 614.47 ppm for ethanol. Thus, it could be said that ethyl acetate and ethanol fractions were classified as a toxic category, while n-hexane was classified as a non-toxic category.Key words: matoa; fraction; phytochemical screening; cytotoxic.

Comparison and influence of metal dopants on the opto-electrical, microstructure and gas sensing properties of nanostructured indium oxide films

Thin films of pure and Sn, Zn, Mn, and Ag-doped indium oxide (In2O3) with a thickness of 150 nm are grown by co-deposition using thermal evaporation technique and annealed at 500 °C. The crystal lattice strain, dislocation density, optical band gap, surface roughness, and gas sensitivity of the films are studied. Comparison of AFM results shows that the Ag-doped In2O3 has the highest roughness. The ethanol vapor sensing results demonstrate that 3% Ag-doped In2O3 films have higher sensitivity at the operating temperature of 325 °C to 1000 ppm of ethanol vapor, due to the presence of more roughness and defects than other films. The response and recovery times of this sample at 1000 ppm ethanol vapor were 32 and 51 s, respectively. Finally, it is shown how 3% of metal impurities in the In2O3 layer can affect the optical, microstructural, and gas sensing parameters of the samples, and also investigated the correlation between them.

Controlled preparation and gas sensitive properties of two-dimensional and cubic structure ZnSnO3

Two-dimensional (2D) ZnSnO3 is a promising candidate for future gas sensors due to its high chemical response and excellent electronic properties. However, the preparation of 2D ZnSnO3 nanosheets by utilizing soluble inorganic salts and nonorganic solvents remains a challenge. In this work, 2D ZnSnO3 was synthesized via a facile graphene oxide (GO)-assisted co-precipitation method, in which inorganic salts in the aqueous phase replaced metal organic salts in a non-aqueous system. Meanwhile, a “dissolution and recrystallization” mechanism was proposed to explain the transformation from 3D nanocubes to 2D nanosheets. In comparison, the 2D ZnSnO3 nanosheets showed a higher response to formaldehyde (HCHO) at low operating temperature (100 °C). The response (Ra/Rg) of the 2D ZnSnO3 sensor to 10 ppm HCHO was as high as 57, which was approximately 5 times the response of the ZnSnO3 nanocubes sensor. However, the ZnSnO3 nanocubes sensor showed better gas sensing performance to ethanol at high temperature (200 °C). Different gas-sensitive properties were attributed to the different gas diffusion and adsorption processes caused by the morphology and nanostructure. Moreover, both sensors could detect either 0.1 ppm HCHO or ethanol at their optimum operating temperature. This work presents a relatively economical method to prepare 2D compound metal oxides, provides a novel “dissolution and recrystallization” mechanism for 2D multi-metal oxide preparation, and sheds light on the great potential of high-efficiency HCHO and/or ethanol gas sensors.

Hydrothermally synthesized flower-like vanadium oxide nanostructures for ethanol sensing studies

In this study, we synthesized flower-like V2O5 nanostructures via a hydrothermal method. The hydrothermal synthesis was performed at 150°C for 2, 4 and 8 h. After crystallization at 450°C, the crystalline samples were prepared. The synthesized products were characterized by different techniques such as X-ray diffraction, Raman spectroscopy and Fourier transform infrared spectroscopy. Morphology was demonstrated by scanning electron microscopy studies. The gas sensing studies were performed toward different gases. It was found that the sensor prepared for 4 h had better ethanol sensing properties relative to other gas sensors. In particular, it showed a response of ∼ 50% to 20 ppm ethanol gas at low temperature of 175°C. The gas sensing mechanisms behind the enhanced gas response of the optimal gas sensor were explained. The results of this study showed promising effects of flower-like morphologies of V2O5 for sensing applications.

Defect-rich ultrathin Sn2O3 nanosheets with dominant polar (100) facets for efficient gas and humidity sensor applications

Defect-rich ultrathin heterovalent tin oxide (Sn2O3) nanosheets with dominant polar (100) facets were synthesized via a facile hydrothermal method for the first time. The structure, morphology, chemical state, bandgap, defects, and specific surface area of these Sn2O3 nanosheets were characterized by XRD, FE-SEM, TEM, XPS, UV–Vis, PL, N2-adsorption, respectively. Taking inspiration from the morphology, defects, and exposed facets that facilitate adsorption-interaction of molecules on the surface, gas and humidity sensors were fabricated based on Sn2O3 nanosheets. The gas sensor response to 200 ppm ethanol at 200 °C is as high as 70.1, and response and recovery times are only 6 s and 3 s, respectively. At room temperature, the humidity sensor exhibits a response up to 2.76 × 103 with a small humidity hysteresis of 1.95%, and the response and recovery times are divided into 27 s and 124 s, respectively. Additionally, both gas and humidity sensors demonstrate excellent repeatability and stability. Finally, gas and humidity sensing mechanisms of the Sn2O3 sensor have been discussed. This work provides a practical candidate for gas and humidity sensors and further develops a new promising application for heterovalent metal oxides in electrical sensory devices.

Ethanol sensor using gadolinia-doped ceria solid electrolyte and double perovskite structure sensing material

Mixed potential gadolinia-doped ceria (GDC)-based gas sensors using a double perovskite composite oxide (Sr2NiMoO6) were fabricated to detect ethanol. The influence of the sensing materials sintered at different temperatures on the sensor properties was investigated. The results showed that Sr2NiMoO6 annealed at 1000 °C was the most suitable sensing material for detecting ethanol due to its suitable micromorphology and high electrochemical catalytic activity. The sensor attached with Sr2NiMoO6-1000 °C displayed the highest sensitivity to 1–200 ppm ethanol at 550 °C, the response value ΔV was piecewise linearly with the logarithm of ethanol concentration, and the slopes were −8 and −51.3 mV/decade in the ranges of 1–10 ppm and 10–200 ppm ethanol, respectively. Moreover, the stability and sensing mechanism of the sensor were also investigated.

A high-performance ethanol gas sensor based on Ce-doped SnO2 nanomaterials prepared by the Pechini method

Ce doped SnO2 composite nanomaterials with different concentrations were prepared by a modified green Pechini method. The crystalline phases, elemental composition, and surface topography of the composite material were characterized by various characterization methods. The test results reveal that the sensor with appropriate Ce doping SnO2 has excellent gas sensing properties for ethanol. The device doped with 2% Ce showed a response as high as 69.4 in 50 ppm ethanol, which is 2.4 times that of the device based on Pure-SnO2. Moreover, the sensor has a lower optimum operating temperature, better ethanol selectivity, linearity, and stability. The enhancement factors of the sensing characteristics are further discussed. Ce-doped SnO2 nanomaterials prepared by the Pechini method have great application potential in gas sensors.

Preparation of composite SnO2/CuO nanotubes by electrospinning and excellent gas selectivity to ethanol

The composite SnO2/CuO nanotubes are prepared by uniaxial electrospinning. By controlling the molar ratio of tin to copper, SnO2/CuO nanotubes (F-1, molar ratio 1:1) and nanofibers (F-1, molar ratio 1:2) samples are prepared, respectively. The experimental results show that the composite SnO2/CuO nanotubes have excellent selectivity for ethanol, the response to ethanol at the same concentration and temperature is three times that of other gases, the saturated concentration of ethanol gas is 250 ppm and 300 ppm respectively, the optimal working temperature is 340 ℃ and the response value has a good linear relationship with the ethanol concentration between 25 and 300 ppm. The response value of F-1 is higher than that of F-2 in the same concentration of ethanol. The response value of the gas sensor based on F-1 to 250 ppm ethanol reaches 8.8 at 340 ℃, and its response and recovery time are 6 and 10 s respectively. The gas sensing mechanism of the material is explained by using the theory of electron depletion layer and barrier height, which is the basis of our follow-up work.

Green and ultrafast preparation of layered CuO nanoparticles and its ultrahigh-performance ethanol sensing application

Accurately controlling and rapidly fabricating ultra-sensitive micro/nano-scale CuO sensors without the assistance of any assembly template or organic solvent was a major challenge recently. In this work, a flower-like Cu3(PO4)2 precursor was prepared within 10 s by an ultrasonic spray method, and then the precursor was soaked in 80 °C NaOH solutions to rapidly prepare CuO material with different microscopic morphologies. Through testing the sensing performance of CuO products for 400 ppm ethanol, it was found that the highest sensitivity of CuO nanoparticles prepared by this method reached 135 (response/recovery time was 173 s/118 s respectively), which was much higher than CuO nanorods and CuO nanosheets, and the sensitivity for 10 ppm ethanol reached 19.9, indicating that the product had an ultra-high sensitivity and an ultra-low detecting limit. At the same time, the optimal detecting temperature has been reduced to 225 °C, while still retaining excellent selectivity, reproducibility, and stability. Furthermore, the whole process only took several minutes, instead of several-day reacting process in the previous work. It provided a way for the rapid fabrication of ultra-sensitive CuO sensor in a green strategy.

Synergistic effects of α-Fe2O3 nanoparticles and Fe-doping on gas-sensing performance of NiO nanowires and interface mechanism

High surface area nickel oxide nanowires (NiO NWs), Fe-doped NiO NWs and α-Fe2O3/Fe-doped NiO NWs were synthesized with nanocasting pathway, and then the morphology, microstructure and components of all samples were characterized with XRD, TEM, EDS, UV–vis spectra and nitrogen adsorption–desorption isotherms. Owing to the uniform mesoporous template, all samples with the same diameter exhibit the similar mesoporous-structures. The loaded α-Fe2O3 nanoparticles should exist in mesoporous channels between Fe-doped NiO NWs to form heterogeneous contact at the interface of n-type α-Fe2O3 nanoparticles and p-type NiO NWs. The gas-sensing results indicate that Fe-dopant and α-Fe2O3-loading both improve the gas-sensing performance of NiO NWs sensors. α-Fe2O3/Fe-doped NiO NWs sensors presented the highest response to 100 ppm ethanol gas (55.264) compared with Fe-doped NiO NWs (24.617) and NiO NWs sensors (3.189). The donor Fe-dopant increases the ground state resistance and the absorbed oxygen content in air. α-Fe2O3 nanoparticles in electron depletion region result in the increasing resistance in ethanol gas and decreasing resistance in air. In this way, α-Fe2O3/Fe-doped NiO NWs sensor presents the excellent gas-sensing performance due to the formation of heterogeneous contact at the interface.

Nickel-Oxide Based Thick-Film Gas Sensors for Volatile Organic Compound Detection

In this paper, we report on the development of a highly sensitive and humidity-tolerant metal-oxide-based volatile organic compound (VOC) sensor, capable of rapidly detecting low concentrations of VOCs. For this, we successfully fabricated two different thicknesses of nickel oxide (NiO) sensors using a spin-coating technique and tested them with seven different common VOCs at 40% r.h. The measured film thickness of the spin-coated NiO was ~5 μm (S-5) and ~10 μm (S-10). The fastest response and recovery times for all VOCs were less than 80 s and 120 s, respectively. The highest response (Rg/Ra = 1.5 for 5 ppm ethanol) was observed at 350 °C for both sensors. Sensors were also tested in two different humidity conditions (40% and 90% r.h.). The humidity did not significantly influence the observed sensitivity of the films. Furthermore, S-10 NiO showed only a 3% drift in the baseline resistance between the two humidity conditions, making our sensor humidity-tolerant compared to traditional n-type sensors. Thus, we propose thick-film NiO (10 μm) sensing material as an interesting alternative VOC sensor that is fast and humidity-tolerant.

A Low Power Bridge-Type Gas Sensor With Enhanced Sensitivity to Ethanol by Sandwiched ZnO/Au/ZnO Film Sputtered in O₂ Atmosphere

This paper proposes a ZnO-based gas sensor fabricated entirely by micro-electro-mechanical system (MEMS) process. The gas sensor is based on a narrow bridge-type micro-heater, which achieve ultra-low static power consumption. A physical vapor deposition (PVD) sputtering method was employed in depositing n-type ZnO-based sensing materials on this heater. Ethanol, a common VOC gas was selected as a choice of gas to be tested, and to enhance the performance of ethanol, a thin layer of metal additive Au is buried between two ZnO film layers in an atmosphere of O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> to form a “sandwiched” ZnO/Au/ZnO structure. The morphology and microstructure of the sensors are observed by SEM and AFM, its crystal structure is characterized by XRD, and its surface characteristic is analyzed by XPS. The results indicate that the “sandwiched” sensing layer shows higher response to ethanol compared with single-layer ZnO, and 15 ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{R}_{\text{air}} /\text{R}_{\text{gas}}$ </tex-math></inline-formula> ) was achieved as the best sensitivity to 100 ppm ethanol with the sensor consuming a low power consumption of just 12.17 mW

Hydrothermally grown uniform sized nickel hydroxide/oxyhydroxide hexagonal nanoprisms exhibiting room temperature ethanol sensing properties

This work reports a simple hydrothermal method for the synthesis of uniform sized hexagonal nanoprisms (~38 nm) of β-nickel hydroxide/oxyhydroxide that show room temperature ethanol sensing properties. The films made of these nanoprisms show response as high as 120 against 100 ppm ethanol vapour at room temperature with good repeatability over several cycles and fast response and recovery times of 2 s and 17 s, respectively. The films of nanoprisms also show high selectivity to ethanol vapour as evident from their almost negligible responses to other alcohol vapors and non-alcoholic vapors tested in this work. What is unique about the material is that it shows no degradation in performance with aging and humidity; rather shows an improved response and selectivity to ethanol at 75% relative humidity. The enhanced performance is explained in terms of the special surface properties of the nanoprisms that can adsorb excess oxygen via oxyhydroxide formation and large surface area as confirmed by photoemission and surface adsorption studies. Further, the change in infrared absorption intensity is measured to understand the decomposition reaction of ethanol on the nanoprism surface. Thus, the synthesized material shows enormous promise as a low-cost material for room temperature ethanol sensing.

Photochemical sensitive study of Au@CuO flower-like materials

CuO flower-like materials (FMs) were fabricated by hydrothermal method and then reduced to obtain Au@CuO FMs by in-situ reduction reaction. The performance of the Au@CuO FMs sensor was evaluated by detecting volatile and toxic gases such as ethanol, isopropanol, methanol, and formaldehyde under ultraviolet (UV) light illumination. It is found that the optimum working temperatures of the CuO FMs sensor and the Au@CuO FMs one are 240 and 100 °C respectively. The response of the Au@CuO FMs can reach 95.3–1000 ppm ethanol, being about 7 times stronger than that of the CuO FMs sensor. Moreover, the response of the Au@CuO FMs sensor to 1000 ppm ethanol increased from 95.3 to 174 under UV irradiation, nearly 2 times as large as that in dark. Accordingly, its corresponding LOD decreased from 99.8 to 78 ppb. Therefore, the Au@CuO FMs are a promising candidate to detect ethanol with excellent response and selectivity.