Ethanol Sensor Research Articles

Room temperature and high response ethanol sensor based on two dimensional hybrid nanostructures of WS2/GONRs

Here in this research, room temperature ethanol and humidity sensors were prepared based on two dimensional (2D) hybrid nanostructures of tungsten di-sulfide (WS2) nanosheets and graphene oxide nanoribbons (GONRs) as GOWS. The characterization results based on scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (ESD), Raman spectroscopy and X-ray diffraction (XRD) analysis confirmed the hybrid formations. Ethanol sensing of drop-casted GOWS films on SiO2 substrate indicated increasing in gas response up to 5 and 55 times higher compared to pristine GONRs and WS2 films respectively. The sensing performance of GOWS hybrid nanostructures was investigated in different concentrations of WS2, and the highest response was about 126.5 at 1 ppm of ethanol in 40% relative humidity (R.H.) for WS2/GONRs molar ratio of 10. Flexibility of GOWS was studied on Kapton substrate with bending radius of 1 cm, and the gas response decreased less than 10% after 30th bending cycles. The high response and flexibility of the sensors inspired that GOWS are promising materials for fabrication of wearable gas sensing devices.

Cubic shaped hematite (α-Fe2O3) micro-structures composed of stacked nanosheets for rapid ethanol sensor application

Herein, the synthesis, characterization, and ethanol gas sensing properties of hematite iron oxide(α-Fe2O3) microstructures were investigated. Detailed examinations using different techniques confirmed the high-density growth and rhombohedral crystal structure of the synthesized Fe2O3 micro-structures with an average crystal size of 38.29 nm. The appearance of several Raman-active A1g(1), A1g(2), and Eg modes in Raman-scattering spectrum further revealed the formation of the hematite phase. The sensor device was fabricated using Fe2O3 micro-structures and tested for various gases such as ethanol, carbon monoxide (CO), and hydrogen (H2). It was observed that the fabricated sensor demonstrated a high response of 13.1for 100 ppm ethanol gas concentration at a temperature of 400 °C. Including the response and recovery times for the fabricated sensors, the transient response for various gases was also recorded and analyzed. The fabricated sensor exhibited a rapid gas response at 400 °C for ethanol gas (13.1) compared to CO (1.95) and H2 (1.71) gases for 100 ppm gas concentrations. A plausible ethanol sensing mechanism was also proposed and presented.

Ethanol sensor based on microrod-like La-doped barium stannate

Due to its importance in human health and environmental monitoring, ethanol sensing has generated large research interest across the globe. In this work, we report a simple co-precipitation method to synthesize La-doped BaSnO3 and evaluate its ethanol sensing properties. Electron microscopy and X-ray diffraction analyses revealed formation of crystalline BaSnO3 having rod-like shape, few microns in length and 1–2 µm in width. The optimal sensing performance was achieved when operated at 220 °C for 4 wt% La-doped BaSnO3 microrods for which a response as high as 48 was obtained against 100 ppm of ethanol exposure, whereas the undoped BaSnO3 exhibited its best performance (although much lower response) at 260 °C. Multiple characterization techniques revealed that the enhancement of the sensor performance by incorporation of La was due to changes in the physico-chemical properties like specific surface area, oxygen content and electronic bandgap of the BaSnO3. The high repeatability, high selectivity to ethanol, fast response and recovery times, and low detection limit of 0.01 ppm suggest good potential for the 4% La-doped BaSnO3 film as a low cost ethanol sensor.

Ultrasensitive ethanol sensor based on segregated ZnO-In2O3 porous nanosheets

ZnO nanosheets exhibit notably interesting gas sensing performances due to their great carrier transport and high special surface area. However, not only the 2D nanosheets tend to stack suppressing the surface area, but also the pristine ZnO cannot show desired ethanol sensing properties. Herein, segregated ZnO-In2O3 porous nanosheets are synthesized facilely via one-pot solvothermal method. The Indium doping stems the porous nanosheets stacking, as well as induces lots of heterojunctions. Due to the specific porous structure for high gas accessibility, thickness less than double Debye length, abundant reaction sites and heterojunctions, the segregated ZnO-In2O3 nanosheets exhibit remarkable ethanol sensing performance (LOD of 100 ppb, response/recovery time of 3/8 s, and great repeatability and selectivity under natural humidity for a long period). This study provides a prospect for practical applications of ZnO-In2O3 ethanol sensors.

High-performance ethanol sensor based on In2O3 nanospheres grown on silicon nanoporous pillar array

At the interfaces between different materials, electronic systems with unusual electronic properties can be generated. Here, we report an In2O3/Si nanoheterostructures prepared by depositing indium grain film on silicon nanoporous pillar array (Si-NPA) by a vacuum thermal evaporation technique and a following thermal oxidation method. The composition and morphology of In2O3 film on Si-NPA were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), which disclosed that the In2O3 film is composed of a layer of In2O3 nanospheres with massive interfaces coating on Si-NPA. The sensor based on In2O3/Si-NPA showed high selectivity to ethanol, and demonstrated a high response of 3.38 at the extremely low ethanol gas concentration of 2 ppm. The response and recovery times to 100 ppm were 3 s and 39 s, respectively. The high performance was attributed to the specific nanostructure feature of In2O3/Si-NPA sensor, large specific surface area and massive surface active sites. Moreover, the impressive features of In2O3/Si-NPA heterostructures have been discussed in detail from its geometrical and band structure. These results observed here indicate that the In2O3/Si-NPA sensor may be a promising sensing candidate for detecting low-concentration ethanol.

Strain-regulated sensing properties of α-Fe2O3 nano-cylinders with atomic carbon layers for ethanol detection

The sensitivity of ethanol sensor is of paramount importance in a variety of areas, including chemical production with ethanol, alcohol testing for driving safety, etc. Herein, α-Fe2O3 nano-cylinders with atomic carbon layers are synthesized, for the first time, through in-situ catalytic chemical vapor deposition combined with hydrothermal techniques for the detection of ethanol. The reported α-Fe2O3@C nano-cylinders with double surficial strain effects deliver an ethanol detection sensitivity of ～8 times as compared with α-Fe2O3 nano-cylinders, ∼10 times higher as compared with its detection sensitivity to ammonia, para-xylene, methanol and benzene. The sensor also exhibits over-14-day operation stability and the minimum detection limit of 10 ppm. To our best knowledge, the performances surpass those of previously reported α-Fe2O3. Such attractive performances are attributed to the enhanced charge transfer in α-Fe2O3 owing to the double surficial strain effects of α-Fe2O3@C nano-cylinders and the efficient adsorption of ethanol with atomic carbon layers.

High-Sensitivity and Ultrafast-Response Ethanol Sensors Based on Graphene Oxide

Ethanol sensors with ultrafast response and high sensitivity have attracted much attention to be applied to daily industrial production processes. In this work, graphene oxide-aniline (GOA) sensors are proposed to meet the requirements of detecting ethanol concentration. Graphene oxide is an outstanding material that has excellent electrical and thermal conductivity, large specific surface area, and high carrier mobility. Because of its special bonding reactions, GOA has advantages of good dispersibility, good electrical conductivity, insolubility in water, and strong plasticity. When testing ethanol concentration with sensors, there will be a lag time, which determines the sensitivity of the sensors. To the best of our knowledge, the GOA sensors in this work have the fastest response time, which is only 27 ms. The GOA ethanol sensors show a good ethanol sensing performance, including excellent sensitivity, cycle stability, and long-term stability.

Improving sensing properties of entangled carbon nanotube-based gas sensors by atmospheric plasma surface treatment

Entangled multi-walled carbon nanotubes (MWCNTs) on polyurethane (PUR) after Ar plasma-treatment and He plasma-treatment have been tested as gas sensors for ethanol sensing. It was found that plasma-treated sensors exhibit higher sensitivity compared to the non-treated samples along with different ethanol concentration. Non-treated sensors exhibit similar sensor response with the increase in ethanol concentration, while Ar plasma-treated sensors displays ~5 times improvement and He plasma-treated sensors show ~3 times improvement with an increase in ethanol concentration. The sensitivity of the plasma-treated sensors is also stable for following two-weeks after the preparation compared to the non-treated sensor. Entangled nanotube network exhibits a significant shift in the baseline resistance after both plasma-treatments. The response time of the sensor was increased after the plasma-treatment, while the recovery was rather quick. Surface analyses revealed that plasma-treatment did not make any significant morphological changes. Thus, the improvements in stability and sensitivity after plasma-treatment are attributed to the plasma-enhanced surface modification and formation of functional bonds on the surface of nanotubes, which are sensitive to the ethanol vapour.

Influence of synthesis methods on the microstructure and Ethanol Sensing properties of barium stannate

Herein, we report the synthesis of BaSnO3 (BSO) from molten salts (BSO1) and test its efficacy as an ethanol sensor, for the first time. BSO was also synthesized using a more well-established coprecipitation method (BSO2), and the influence of the synthesis method on morphology, microstructure and surface chemical composition of BSO was compared using electron microscopy, x-ray diffraction and photoelectron spectroscopy. Both BSO1 and BSO2 exhibited their best responses to 100 ppm of ethanol at 260 °C, but BSO1 showed higher response (12.5) and lower detection limit (0.5 ppm) compared to those of BSO2 (8.2 and 1 ppm) suggesting its superior ethanol sensing properties. The improved sensing of BSO1 was correlated with the corresponding surface morphology and chemical composition.

Pd/ZnO/Ni photoelectrochemical ethanol sensor

In this paper, by using hexagonal prism nanometer zinc oxide absorbing UV-light photoinduced charge separation excitation electrode. The separation of excitation source and detection source reduces the interference of background noise and effectively improves the sensitivity of the electrode. At the same time, the surface of the electrode was modified by metal particles to increase the surface area of the electrode, improve the adsorption capacity of the electrode to ethanol, and inhibit electron hole recombination improves the sensitivity of the electrode. We have engineered a kind of Pd/ZnO/Ni photochemical ethanol electrode, which by hydrothermal method using nickel foam as the base to grow Hexagonal prism nanometer zinc oxide and by electrochemical deposition on the surface of ZnO/Ni electrode were deposited palladium particles. The electrode has been verified by the experiment can detect 0.02 μM the change of ethanol. The electrode surface morphology of the electrode was characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Energy dispersive spectrum (EDS), and the performance of the electrode was tested by Cyclic Voltammetry (CV) and Chronoamperometry (CA). The test results showed that the electrode had favorable sensitivity and linear relationship to ethanol. Compared with traditional electrochemical sensors, the sensitivity of Pd/ZnO/Ni has been improved greatly. It provides an effective solution to improve the detection accuracy of ethanol sensor in industrial and medicine and fruit and vegetable storage.

Mechanistic Insight into the Limiting Factors of Graphene-Based Environmental Sensors.

Graphene has demonstrated great promise for technological use, yet control over material growth and understanding of how material imperfections affect the performance of devices are challenges that hamper the development of applications. In this work, we reveal new insight into the connections between the performance of the graphene devices as environmental sensors and the microscopic details of the interactions at the sensing surface. We monitor changes in the resistance of the chemical-vapor deposition grown graphene devices as exposed to different concentrations of ethanol. We perform thermal surface treatments after the devices are fabricated, use scanning probe microscopy to visualize their effects down to nanometer scale and correlate them with the measured performance of the device as an ethanol sensor. Our observations are compared to theoretical calculations of charge transfers between molecules and the graphene surface. We find that, although often overlooked, the surface cleanliness after device fabrication is responsible for the device performance and reliability. These results further our understanding of the mechanisms of sensing in graphene-based environmental sensors and pave the way to optimizing such devices, especially for their miniaturization, as with decreasing size of the active zone the potential role of contaminants will rise.

Plastic Optical Fiber Sensor for Detection of Ethanol Concentrations

An optimized study of tapered polymer optical fiber (POF) for measurement of different concentration of ethanol in deionized water (0.5%-3.5%) is proposed and demonstrated. This sensor operated based on evanescent wave absorption principle. The cladding of PMMA based POF is removed using organic solvents which can be used to create tapered POF. The unclad length around 1 cm and 3 cm as well as the waist diameters of POF in the range of 5 mm and 8 mm were compared for their efficiency as an ethanol sensor based on power output ratio values. Tapered POF with smaller waist diameter and longer tapered length showed higher sensitivity as ethanol sensor. Therefore, by tailoring the length and tapered diameter of POF, high sensitivity of ethanol sensor can be fabricated.

Triboelectric Nanogenerator Enhanced Schottky Nanowire Sensor for Highly Sensitive Ethanol Detection.

Highly sensitive ethanol sensors are important for environmental and industrial monitoring. In our work, we demonstrate a method to enhance the response of a Schottky sensor based on a ZnO nano/microwire (NMW) by triboelectric nanogenerator (TENG). Via lowering the Schottky barrier height (SBH) via the high voltage from TENG, the response of the sensor is enhanced by 139% for 100 ppm ethanol. This method accelerates the recovery process. The high voltage from TENG produces a high intensity electric field to drive diffusion of the oxygen vacancies in ZnO NMW toward to the junction area around the interface. It is equivalent to applying the reverse voltage on the Schottky junction, which leads to the increase of depletion width. More chemisorbed oxygen on the depletion region is consumed once the ethanol gas is injected into the chamber, which improves the response of the ethanol sensor. This study provides a new, simple, and effective method to improve the sensor response.

Sensitivity enhancement of AZO-based ethanol sensor decorated by Au nano-islands

Detecting the hazardous gases for monitoring air pollution and medical diagnosis make highly sensitive gas sensors appeal to many researches. In this paper, benefiting from unique properties of noble metals, Al-doped ZnO based Ethanol sensors were fabricated and characterized in three structures including Al: ZnO thin film, Silver and Gold nano-islands on Al: ZnO thin film. The Silver and Gold thin films turn to nano-islands after a simple annealing process. The XRD analysis of the sputtered Al: ZnO layer indicates the wurtzite crystal structure of the layer with a peak at (002) plane. Moreover, the sensitivity study reveals that Nano-islands of noble metals substantially affects the sensitivity of the sensors. The decorated Gold nano-island Al: ZnO Ethanol sensor has the highest response showing an amount of 45. The response of Al: ZnO and Silver decorated Al: ZnO sensors are virtually identical to all concentrations of Ethanol, whereas the Al: ZnO gas sensor with Gold nano-islands has the substantial sensitivity for different concentrations. In addition, the response times of the sensors are 85, 70 and 90 s for Al: ZnO, Al: ZnO with Ag islands and Al: ZnO decorated by Au islands, respectively. The recovery time of Al: ZnO sensor decorated by Au islands is about 23s, while the recovery time of the Al: ZnO and Al: ZnO decorated by Silver islands are 360 and 370s, respectively. Hence, the simple annealing process on the sputtered gas sensor with a thin layer of Gold makes nano-islands on the sensor which elevates the performance of Ethanol sensing due to the high sensitivity and sensitivity of the sensor.

Local grain-to-grain conductivity in an SnO2–V2O5 nanocomposite ethanol sensor

Nanocrystalline tin oxide—vanadium oxide (SnO2–V2O5) nanocomposite was prepared by the hydrothermal route. Morphological and conductive atomic force microscopy studies were employed to explore the properties of the interface between the grains and grain boundaries of these binary oxides. Detailed analysis of this nanocomposite revealed that the barrier height of 0.512 eV favours a pronounced sensitivity of 63.99% towards 160 ppm of ethanol at room temperature. This might also be due to the decrease in the resistance from 2000 MΩ (individual SnO2) to 830 MΩ (nanocomposite). The synergistic effect, large surface area, greater number of interfaces and more conduction electrons provide a greater number of surface active sites for the nanocomposite. This leads to the nanocomposite showing better sensing performance than the corresponding individual systems.

A novel ppm level ethanol sensor based on La loaded ITO impregnated with Pd and Sb additives

The present work reports on a novel resistive ppm level ethanol sensor, prepared from nanocrystalline lanthanum loaded indium tin oxide (ITO) impregnated with palladium and antimony additives. A simple unique gel calcination process was adapted to synthesize the nanocomposite powders from their water based precursor salts. This was followed by detailed material characterizations through X-ray diffractometer, FESEM, TEM, EDX and XPS analyses. Fabricated Taguchi type sensor with an optimum concentration of Pd exhibited an excellent sensing performance towards a wide concentration range of (1–100 ppm) ethanol vapour. The sensor showed ~87% sensing response for 10 ppm ethanol vapour at an operating temperature of 300 °C. Even at 1 ppm concentration, ~53% response was observed with fast response and recovery time. The sensing action has been elucidated as the catalytic oxidation of ethanol to carbon di oxide over the La loaded ITO surface layer that resulted in electron transfer to the indium tin oxide site. In addition, synergistic effect of palladium and antimony enhanced the sensing performance as well as reduced the base resistance of the sensor by chemical/electronic sensitization and increasing carrier ion concentration respectively. Comparatively low resistance, negligible cross sensitivity, quick response/recovery time and good long term stability makes the sensor suitable for deployment in practical applications.

Nanochitin-based composite films as a disposable ethanol sensor

Abstract Miniaturized and inexpensive sensing platforms remains an important goal for the field-deployable monitoring of toxic gases. In this work, we report a disposable ethanol sensor based on nanochitin-composite containing chitin nanowhiskers/zinc oxide nanoparticles/polyaniline (ChitNW-ZnO/PANI) produced via solution casting method. The as-prepared material was fully characterized by transmission electron microscopy, atomic force microscopy, contact angle measurements, mechanical tests, thermogravimetric analysis and X-ray diffraction, confirming its successful preparation and revealing its morphology, microstructure and composition. Such nanocomposite showed enhanced ethanol sensing performance at room temperature, in which quantitative analysis was obtained in the range 20–100 ppm with a detection limit of 17 ppm (S/N = 3). We further validated that common potential interfering agents were not misidentified with ethanol. The development of such a unique nanochitin-based composite as a disposable sensor is a great step ahead in flexible and wearable electronics having potential applications in different fields such as biomedical and biotechnological engineering, security and internet of things (IoT).

PCB-integrated non-destructive microwave sensor for liquid dielectric spectroscopy based on planar metamaterial resonator

This paper presents a novel, cost-effective printed circuit board (PCB)-integrated microwave sensor with a planar circular complementary split-ring resonator (CSRR) for the dielectric measurement of liquids. The proposed sensor design comprises glass capillary tubes inside the PCB substrate; these tubes contain the samples. Thus, the sensor can estimate the complex permittivity of the sample inserted in the tubes passing through the PCB and parallel to the CSRR sensor plane. These sensors can be manufactured on low-cost substrates, using conventional methods employed in the PCB industry. Subsequently, the sensors can be integrated into the PCB of an electronic circuit. As a proof of principle, a PCB-integrated water–ethanol sensor is fabricated on a FR4 substrate. To evaluate the operation of the sensor, a measurement setup is used to determine the resonant frequency and the Q factor. The complex permittivities of the tested samples are estimated using these determined values. Based on a comparison with the values reported in previous studies, it is concluded that the proposed sensor operates successfully and detects the proportions of each constituent in tested water–ethanol mixtures tested. Moreover, additional types of liquid mixtures can be tested by employing the proposed method.

Optofluidic in-fiber on-line ethanol sensing based on graphene oxide integrated hollow optical fiber with suspended core

Abstract In this study, a novel in-fiber optofluidic trace ethanol sensor is proposed firstly. The microstructured hollow fiber (MHF) with a suspended core is a key part of the overall device which is integrated with graphene oxide (GO). The GO can be uniformly trapped on the whole surface of the suspended core in the MHF by using evanescent field inducing method. When trace microfluidic ethanol passes through the in-fiber device, the light intensity of the suspended core can be significantly modulated through the interaction between the GO on the core and ethanol. The device presents an excellent linearity on-line response with an average sensitivity of 0.16 dB/% with linear regression equation of y = 0.16x + 25.989. In general, this compact optofluidic in-fiber trace ethanol sensor can be utilized as for on-line detection of trace amounts of ethanol in special environments.

Development of a long-acting direct-acting antiviral system for hepatitis C virus treatment in swine

Chronic hepatitis C virus (HCV) infection is a leading cause of cirrhosis worldwide and kills more Americans than 59 other infections, including HIV and tuberculosis, combined. While direct-acting antiviral (DAA) treatments are effective, limited uptake of therapy, particularly in high-risk groups, remains a substantial barrier to eliminating HCV. We developed a long-acting DAA system (LA-DAAS) capable of prolonged dosing and explored its cost-effectiveness. We designed a retrievable coil-shaped LA-DAAS compatible with nasogastric tube administration and the capacity to encapsulate and release gram levels of drugs while resident in the stomach. We formulated DAAs in drug-polymer pills and studied the release kinetics for 1 mo in vitro and in vivo in a swine model. The LA-DAAS was equipped with ethanol and temperature sensors linked via Bluetooth to a phone application to provide patient engagement. We then performed a cost-effectiveness analysis comparing LA-DAAS to DAA alone in various patient groups, including people who inject drugs. Tunable release kinetics of DAAs was enabled for 1 mo with drug-polymer pills in vitro, and the LA-DAAS safely and successfully provided at least month-long release of sofosbuvir in vivo. Temperature and alcohol sensors could interface with external sources for at least 1 mo. The LA-DAAS was cost-effective compared to DAA therapy alone in all groups considered (base case incremental cost-effectiveness ratio $39,800). We believe that the LA-DAA system can provide a cost-effective and patient-centric method for HCV treatment, including in high-risk populations who are currently undertreated.