Search query: Research statusof gas sensing for methane sensors

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abstract: The development of fast response, highly accurate methane sensor becoming an important target for their indispensable role in the detection of methane during the coal mine and natural gas transportation, supply and use. In this cut edge review, we summarized the development of gas sensors in these years in both technology and materials aspects. We believe this review could inspire scientists, inventors, researchers and engineers in this field. The methane sensors can be divided into semiconductor resistive type gas sensors, optical fiber gas sensors and mass sensitive gas sensors according to their functions. For example, the typical methane gas sensing materials can be divided into semiconductor metal oxides, nanocomposites, organic polymer composites, cryptophane A, carbon nanotubes and their doping materials etc. Semiconductor metal oxide nanomaterials such as SnO2, ZnO, In2O3, Fe2O3, Co3O4 are the most used methane gas sensing materials. In a certain temperature range, the resistance of the gas sensor can be changed by the adsorption and desorption of methane molecules with the surface of semiconductor metal oxide film. In order to promote the sensitivity and lower the working temperature of methane sensors with semiconductor metal oxides, noble metal nanoparticles, carbon nanotubes or graphene were doped into metal oxides to form nanocomposites. The methane sensor prepared by doped polymer composites could work at room temperature which made it more applicable in closed, flammable and explosive places. Cryptophane A has an amazing affinity for methane. When cryptophane A was exposed to the methane gas, the methane molecules would enter the cavity of the cryptophane A. Furthermore, some studies have shown that CNTs doped with noble metals were sensitive to methane but remain controversial. The future challenges and opportunities in this field are also discussed in the perspective section. The exploitation of high response, high sensitivity and selectivity methane sensing materials which can work at room temperature remains a major challenge. The properties of methane sensors can be improved from grain size, porosity and thickness of gas sensing materials. With the development of preparation process of gas sensing materials and intelligent control technology, the intelligent gas sensors which could monitor many kinds of gas would be one trend in development of methane gas sensor.
author_names: Yanbao Guo

Chengcheng Liu

Deguo Wang

Renyang He
title: Advances in the development of methane sensors with gas sensing materials
venue: Chinese Science Bulletin
year: 2019

abstract: Methane is an explosive gas in coalmines and needs to be monitored by methane sensors. Conductive type methane sensors are small, simple and stable, and they are very promising for mining safety or home safety applications. They can even be employed in mining Internet of things if the power consumption can be lowered down to few milliwatts. Many researches of nanomaterials based conductive type methane sensors have been reported recently. This review intends to present a comprehensive and critical summary on the recent progresses in the nanomaterials based conductive type methane sensors field. Many excellent methane sensitive nanomaterials will be present, such as SnO2, ZnO, TiO2, WO3, carbon nanotubes, graphene, rare earth metal based perovskite oxides and their hybrids. Particular attention is given to the synthetic methods of the nanomaterials, sensing mechanisms of the nanomaterials and the relationship between the sensing performance and the structures and components of the nanomaterials. Finally, the future trends and perspectives of nanomaterials based conductive type methane sensors are proposed.
author_names: Ming-Zhi Jiao

Xiao-Yu Chen

Ke-xiang Hu

De-Yu Qian

Xiao-Hu Zhao

En-Jie Ding
title: Recent developments of nanomaterials based conductive type methane sensors
venue: Rare Metals
year: 2021

abstract: Methane (CH4) gas sensors play an important role in industrial safety and detection of indoor gas quality. In general, metal oxide semiconductor sensing materials with nano structure have high responses to the target gas. However, the sensor resistance is usually very high. Considering the practical application, it is vital to reduce base resistance and improve sensitivity for gas sensors. Herein, Pd doped SnO2 nanoparticles were prepared as the basis material by a simple sol gel method. In order to adjust the resistance, the pentavalent metal element (Sb) was introduced via a simple doping route. As CH4 sensing layers, the prepared SnO2 sensors doped with Pd and Sb exhibited the most obvious resistance reduction effect. Meantime, excellent sensing performances including high response, fast response/recovery time, excellent reproducibility and great stability were also obtained. In depth research has shown that the ability to reduce resistance depends on the effective internal doping of cation with high valence. The enhanced sensing capability can be attributed to the 'synergistic effects' including catalytic effects of novel metals, increased oxygen vacancies and decreased band gap energy. This work can provide a new opportunity to design metal oxide sensing materials with low resistance and high sensitivity.
author_names: Jiawen Shi

Sen Liu

Ning Sui

Shuang Cao

Tingting Zhou

Tong Zhang
title: Sb/Pd co doped SnO2 nanoparticles for methane detection: resistance reduction and sensing performance studies
venue: Nanotechnology
year: 2021

abstract: Two projects were designed and implemented in an effort to gather high quality data focused on two metrics important to environmental science: methane emissions from cities and the flow rate of sap in trees. Methane is a powerful greenhouse gas that is emitted to the atmosphere in many ways. In cities, these sources include landfills and fugitive emissions from natural gas infrastructure, and the quantification of these emissions is an important area of research. Sap flow, which is a direct measure of the water use of a tree, is also vital to the understanding of rates of carbon exchange between the atmosphere and the biosphere. A recently developed technology, the EM27/SUN spectrometer, was deployed in the city of Indianapolis for a five day measurement campaign. Five of the sensors were spread across the greater urban area so that atmospheric methane concentrations could be measured as air moved across the city. An inverse modelling framework was designed which combined these observations with a trace gas transport model and information on the location and predicted magnitude of methane sources. This framework was able to estimate the magnitude of emissions from small diffuse sources, such as individual pipeline leaks, spread across the urban domain. Diffuse emissions from the city were found to be 47.0 14.8Gg yr 1, which was more twice the suggested by some bottom up inventories, but consistent with other observation and modelling efforts. The insights gained during this project are important to future urban measurement and modelling efforts, especially those using remote sensing sensors like the EM27/SUN or current and future satellites. The second project was the development of new sensor to measure the flow rate of sap in trees. There are two issues with conventional sap flow sensors which limit their widespread use. The first is that the probes are costly and difficult to manufacture. The second major issue is that installing the probes correctly, so that they are aligned properly with each other, is quite difficult which introduces large uncertainties in the data. The new design, the ribbonized sap flow (RSF) sensor solves these issues by placing all of the components of the sensor onto a single circuit board that can be easily slid into a slot made in the tree, and can be manufactured at much lower cost. This sensor, and a custom control and data collection system, were designed, built, calibrated, and tested in field conditions in multiple locations. The results from the calibration suggest that the RSF system has the sensitivity and accuracy needed to make meaningful sap flow measurements, and the reduced cost over conventional systems make in an appealing option for future sap flow deployments.
author_names: Taylor S Jones
title: Advances in Environmental Measurement Systems: Remote Sensing of Urban Methane Emissions and Tree Sap Flow Quantification
year: 2019

abstract: Abstract Two dimensional (2D) nanomaterials with porous structure have stimulated much research interest owing to their unique structure and fascinating physical and chemical properties. Here, ultrathin 2D porous nanosheets (PNSs) of pure and SnO2 decorated NiO with uniform hexagonal shape were synthesized by using the pre synthesized Ni(OH)2 nanosheets precursor. The obtained SnO2/NiO PNSs were about 100~150 nm in size and their mean thickness was about 7.5 nm. The gas sensing properties of the prepared pure and SnO2 decorated NiO PNSs were investigated intensively. It was found that after decorating with different amount of SnO2, the sensor based on NiO PNSs showed an improved sensing properties to methane (CH4) and the optimal SnO2 content in the composite was determined to be 2 mol% At the optimum working temperature of 330 degC, the SnO2/NiO 2 sensor showed higher response and faster response/recover speed towards 500 ppm CH4 than the pure NiO sensor. In addition, the SnO2/NiO 2 sensor also exhibited a good long term stability within 28 days, demonstrating its potential application for CH4 detection. The porous structure and p n junction related sensing mechanism of SnO2/NiO PNSs was also discussed.
author_names: Saisai Zhang

Yanwei Li

Guang Sun

Bo Zhang

Yan Wang

Jianliang Cao

Zhanying Zhang
title: Enhanced methane sensing properties of porous NiO nanaosheets by decorating with SnO2
venue: Sensors and Actuators B: Chemical
year: 2019

abstract: Abstract In this research, flame spray made 0 2 wt% Cr doped SnO2 nanoparticles were synthesized and methodically studied for specific detection of methane (CH4) for the first time. From characterizations using X ray diffraction, X ray photoelectron spectroscopy, scanning/transmission electron microscopy and nitrogen adsorption, Cr was found to form substitutional solid solution in 5 20 nm nanoparticles with tetragonal SnO2 structure. In addition, grain and particle sizes decreased while surface area increases considerably with increasing Cr content. The sensing films prepared by spin coating technique were evaluated towards various flammable and toxic gases in dry air at 200 400 degC. Gas sensing data evidently showed that the SnO2layer with the optimum Cr doping level of 0.5 wt% offered a remarkable response of ~1268 with a decent response time of ~3.9 s to 1 vol% CH4at the optimum working temperature of 350 degC. In addition, the optimal Cr doped SnO2sensor gave high CH4 selectivity against H2, C2H2, NO2, NO, N2O, CO, NH3, SO2, C2H5OH, C3H6O and H2O. Therefore, the flame spray made Cr doped SnO2material is an attractive choice for selective and sensitive detection of CH4.
author_names: K Bunpang

Anurat Wisitsoraat

Adisorn Tuantranont

Suparat Singkammo

Sukon Phanichphant

Chaikarn Liewhiran
title: Highly selective and sensitive CH4 gas sensors based on flame spray made Cr doped SnO2 particulate films
venue: Sensors and Actuators B: Chemical
year: 2019

abstract: Nowadays, gas sensors are fast becoming an imperative part of modern life with extensive applications in domestic safety, environmental monitoring, industrial process control, public security, medical applications and chemical warfare assessment amongst many others. The detection of minor gas leaks has been a challenging area of research, particularly in view of the hazards to human health and safety posed by toxic gases like NO2, NO, CO, NH3 etc and combustible gases like methane, hydrogen gas and some volatile organic compounds. Thus it is imperative to evolve and employ simple yet reliable gas sensing mechanisms with optimum response and selectivity towards even low concentration of analyte gas at room temperature. Most of the conventional gas sensors are based on metal oxide semiconductors which are low cost, exhibit good sensitivity and fast response/recovery. Zinc oxide is one such n type semiconducting oxide, which has been widely studied for gas sensing response due to its ease of fabrication, high sensitivity and environment friendly nature. However, the operating temperature of such sensors is usually high >200degC) owing to the wide band gap (3.37 eV) and high electrical resistance (kO MO) which limits their practical utilization. In order to be used in hazard monitoring and home/workplace safety, the gas sensors need to be sensitive to gas exposure in mild operating conditions. As an alternative, more recently, graphene and its derivatives like pristine graphene (PG) reduced graphene oxide (rGO) etc. have been studied for sensing applications owing to their exceptional electronic and physical properties such as high carrier mobility at room temperature, good thermal stability, high mechanical strength, ballistic conductivity and large specific surface area. These sensors show high sensitivity at low operating temperatures (down to room temperature) towards low concentrations of analyte gas. However most of these rGO based sensors exhibit relatively longer response/recovery times than metal oxide based gas sensors. Hence, nanocomposites formed by hybridizing graphene or its derivatives with metal oxide nanoparticles are being explored as gas sensing materials. Combining reduced graphene oxide with zinc oxide to form hybrid nanostructures is particularly interesting because not only do they display the individual properties of the metal oxide NPs (faster response/recovery times) and of graphene (high electronic conductivity leading to efficient room temperature gas response) but may also have synergistic effects leading to better sensitivity as a gas sensing material. Here we present a review of the recent progress in rGO ZnO nanocomposites based gas sensors. Copyright (c) 2018 VBRI Press.
author_names: Sitakshi Gupta

Chhaya Ravikant
title: Reduced graphene oxide zinc oxide nano composites for gas sensing applications
year: 2018

abstract: In the late summer of 2016, our team deployed a network of low cost air quality sensing systems in partnership with community based organizations in a neighborhood in South Los Angeles, California. Residents of this community were concerned about possible emissions from local oil and gas activity, however in addition to these potential emissions, the neighborhood is also subject to a complex mixture of pollutants from other nearby sources including major highways. For this deployment, metal oxide VOC sensors were quantified to provide methane (CH4) and total non methane hydrocarbon (TNMHCs) concentration estimates. This data along with other sensor signals, meteorological data, and community member observations was used to examine the composition and possible origins of observed emissions. The sensor network displayed expected environmental trends and highlighted short term elevations in CH4 and/or TNMHCs, which we were then able to investigate more closely. The results indicated that sources of both combusted and volatilized hydrocarbons were likely affecting air quality throughout the community, including near the site of the local oil and gas activity. This deployment may serve as a model for how multi sensor systems deployed in networks can be leveraged to better understand sources in complex areas, potentially supporting future community based air quality research.
author_names: Ashley Collier-Oxandale

Nicole J Wong

Sandy Navarro

Jill E Johnston

Michael Hannigan
title: Using Gas Phase Air Quality Sensors to Disentangle Potential Sources in a Los Angeles Neighborhood.
venue: Atmospheric environment
year: 2020

abstract: Abstract A compact refractive index (RI) sensor, based on the Mach Zehnder Interferometer (MZI) has been developed and experimentally evaluated for the highly sensitive detection and quantification of gases (Helium, Methane, and Carbon Dioxide) The RI sensor utilizes a variety of fibre types: Single Mode Fibre (SMF) Photonic Crystal Fibre (PCF) and Hollow Core Photonic Crystal Fibre (HC PCF) In order to fabricate the MZI sensors, a short length of sensing fibre was positioned between a lead in and a lead out single mode fibre (SMF) with an air gap at each interface. Three types of sensors were fabricated using this configuration employing 4 mm stub of: (i) PCF, (ii) 10 um HC PCF, and (iii) 20 um HC PCF as the sensing elements. The performance of these sensors, for detecting and measuring the quantity of gas present, were compared. The transmission spectrum of MZI sensors are formed by interference between the cladding and core modes. These transmission signals correspond to the frequency components in the sensor's Fast Fourier Transform (FFT) spectrum. The effect of gap distance on the number and amplitude distribution of the modes was examined in an effort to optimize the design elements. The resulting fiber sensors can measure the RI of a gas filled cavity and they showed high sensitivity to helium, methane, and carbon dioxide. The highest RI sensitivity of 3210 nm/RIU was demonstrated in the RI range of 1.0000347 to 1.000449 by a sensor with a 4 mm long sensing stub element of 10 um HC PCF. Cyclic tests with the group of gases demonstrated that the measurements are highly repeatable. The measurement response and recovery times for all sensors were determined, and it was concluded that the 20 um HC PCF sensor has the fastest response/recovery time and the PCF sensor has the slowest. This research illustrates that the sensors fabricated by the proposed method have potential for improving the ability to detect and quantify pure gases. Additionally, the sensors are highly sensitive to low percentages of CO2, making them suitable for greenhouse gas measurement.
author_names: Kaveh Nazeri

Colin Bradley
title: The effect of photonic crystal fibre structure on the performance of Mach Zehnder interferometer fibre optic gas sensors
year: 2020

abstract: Reducing the operating temperature to room temperature is a serious obstacle on long life sensitivity with long term stability performances of gas sensors based on semiconducting oxides and this should be overcome by new nano technological approaches. In this work, we report the structural, morphological, chemical, optical and gas detection characteristics of Eu doped ZnO (ZnO:Eu) columnar films as a function of Eu content. The scanning electron microscopy (SEM) investigations showed that columnar films, grown via synthesis from chemical solutions (SCS) approach, are composed of densely packed columnar type grains. The sample sets with a content of ~0.05, 0.1, 0.15 and 0.2 at% of Eu in ZnO:Eu columnar films were studied. The surface functionalization was achieved using PdCl2 aqueous solution with additional thermal annealing in air at 650 oC. The temperature dependent gas detection characteristics of Pd functionalized ZnO:Eu columnar films were measured in detail, showing a good selectivity towards H2 gas at operating OPT temperatures of 200 300 oC among several test gases and volatile organic compounds (VOCs) vapors; such as methane, ammonia, acetone, ethanol, n butanol and 2 propanol. At an operating temperature OPT of 250 oC a high gas response Igas/Iair 115 for 100 ppm H2 was obtained. Experimental results indicate that Eu doping with an optimal content about 0.05 0.1 at% along with Pd functionalization of ZnO columns leads to a reduction of the operating temperature of the H2 gas sensor. DFT based computations provide mechanistic insights into the gas sensing mechanism by investigating interactions between the Pd functionalized ZnO:Eu surface and H2 gas molecules supporting the experimentally observed results. The proposed columnar materials and gas sensor structures would provide a special advantage in the fields of fundamental research, applied physics studies, ecological and industrial applications.
author_names: Cristian Lupan

Rasoul Khaledialidusti

Abhishek Kumar Mishra

Vasile Postica

Maik-Ivo Terasa

Nicolae A Magariu

Thierry Pauporte

Bruno Viana

Jonas Drewes

Alexander Vahl

Franz Faupel

Rainer Adelung
title: Pd Functionalized ZnO:Eu Columnar Films for Room Temperature Hydrogen Gas Sensing: A Combined Experimental and Computational Approach.
venue: ACS applied materials interfaces
year: 2020