CO Gas Sensitivity Research Articles

Influence of Pt or Au doping on improving the detection of CO by ZnO: A first-principles calculations study

ZnO doped with Pt or Au (Pt/Au-ZnO) is considered a promising gas sensing material, owing to its high gas response at room temperature. Despite several experiments that have discovered the phenomenon, its promoting mechanism and gas adsorption behavior is still unclear. Thus, through the first-principles methods, this work illustrated the adsorption behavior and the electrical properties of CO on Pt/Au-ZnO. We elucidated the mechanism of enhancing the CO gas sensitivity of ZnO due to Pt or Au doping, which fills the theoretical gap from the microscopic scale and provides a theoretical basis for the research of CO detection.

Effect Synthesis Time of CeO2 Nanoparticles by Microwave-Assisted Hydrothermal as a Sensing Device on CO Gas Sensitivity

Effect Synthesis Time of CeO2 Nanoparticles by Microwave-Assisted Hydrothermal as a Sensing Device on CO Gas Sensitivity

Density functional theory study of Cu-doped BNNT as highly sensitive and selective gas sensor for carbon monoxide

The adsorption of CO, CO2, CH4, H2, N2 and N2O on armchair (5,5) boron nitride nanotube (BNNT) with and without the doping of transition metals (TM), i.e. Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu or Zn, was investigated using the density functional theory calculation. The results indicate all the considered gases are physically adsorbed by weak interaction on the pure BNNT, revealing that pure BNNT has poor sensing performance for these gases. TM are then doped in the B or N vacancy of BNNT to improve the sensitivity and selectivity. As a result, it was found that the gas adsorption performance of BNNT is obviously enhanced due to the introduction of TM dopant atom. In particularly, according to the results of adsorption energy, Cu doped BNNT (Cu-BNNT) system shows a high selectivity toward CO molecule compared with other metal doped systems. This is further confirmed by the density of state, energy gap and charge transfer analyses. Furthermore, based on the sensor performance analysis, it was found that Cu-BNNT also has favorable desorption characteristics for CO. Therefore, this study concluded that Cu-BNNT can be used as a superior sensor material with high sensitivity, selectivity and favorable recycle time for CO gas.

Effect of the Morphology and Electrical Property of Metal-Deposited ZnO Nanostructures on CO Gas Sensitivity.

The development of a highly sensitive gas sensor for toxic gases is an important issue in that it can reduce the damage caused by unexpected gas leaks. In this regard, in order to make the sensor accurate and highly responsive, we have investigated which morphology is effective to improve the sensitivity and how the deposited nanoparticle affects the sensitivity by controlling the morphology of semiconductor oxides—either nanorod or nanoplate—and depositing metal nanoparticles on the semiconductor surface. In this study, we compared the CO gas sensitivity for sensors with different morphology (rod and plate) of ZnO nanostructure with metal nanoparticles (gold and copper) photodeposited and investigated the correlation between the gas sensitivity and some factors such as the morphology of ZnO and the properties of the deposited metal. Among the samples, Au/ZnO nanorod showed the best response (~86%) to the exposure of 100 ppm CO gas at 200 °C. The result showed that the electrical properties due to the deposition of metal species also have a strong influence on the sensor properties such as sensor response, working temperature, the response and recovery time, etc., together with the morphology of ZnO.

Selective and Reversible Sensing of Low Concentration of Carbon Monoxide Gas Using Nb-Doped OMS-2 Nanofibers at Room Temperature

A reversible and selective resistive gas sensor using Nb-doped cryptomelane octahedral molecular sieves (Nb-OMS-2) nanofibers for room-temperature CO gas detection was developed. The electrical resistance of the Nb-OMS-2 nanofibers decreases on exposure to CO gas. The sensor displayed response of 22% for 2 ppm and 91% for 400 ppm of CO gas in air. The average detection and recovery time were ~25 s for 200 ppm of CO at room temperature. The substitution of Mn with Nb in the OMS-2 framework, the formation of Nb-O-Mn bridge, and the reaction of CO with bridge oxygen are proposed to be responsible for high sensitivity and selectivity for CO gas in air.

CO gas sensitivity and its oxidation over TiO2 modified by PANI under UV irradiation at room temperature

A series of polyaniline–titanium dioxide (PANI/TiO2) nanocomposite film sensor were fabricated by an in-situ chemical oxidation polymerization of aniline at TiO2 (anatase) surface, and were evaluated the CO gas sensitivity under UV irradiation at room temperature. Although adding PANI into TiO2 seemed to weaken the photo-assisted conductivity of film sensor sample at N2 atmosphere, it enhanced the photo-assisted gas sensitivity to CO. Based on the chemical characterization results of PANI/TiO2 by FT-IR, Raman and XPS, it is proposed that the protonated N site in PANI chains (formed by TiO2 interacting with PANI) would promote the adsorption of CO, resulting in the more electrons from CO to PANI by the typical π–conjugated structures of benzenoid and quinonoid units and then to TiO2 by the hydrogen bonds (N⋯H⋯O) in the interface of PANI and TiO2. Moreover, the presence of H2O could enhance this photo-assisted gas sensitivity. Furthermore, the PANI/TiO2 powder sample also exhibited a higher activity of photocatalytic oxidizing CO than the pure TiO2 sample, indicating that the enhancement in the photo-assisted sensing response to CO would benefit the photocatalytic oxidation of CO over PANI/TiO2. This study not only provides a possible approach to develop a photo-assisted gas-sensitive material by introducing the structure of organic-inorganic hybrided nanocomposite, but also provides a possible method to estimate the photocatalytic activity of a semiconductor material by testing its photo-assisted sensitivity to the reactant gas.

Electric field improved the sensitivity of CO on substitutionally doped antimonene

The geometrics and electronic structures of substitutionally doped antimonene and the interaction between CO molecule different substrates have been investigated using first-principles calculations to exploit the sensitivity of CO to antimonene. It is found that CO adsorption on pristine antimonene is physical adsorption, while it is converted to chemical adsorption after doping. The results indicate that an external electric field (V) ranges from −0.5eV/Å to 0.21eV/Å could improve the CO gas sensitivity of the antimonene, which is helpful to realize the use of CO gas sensor at room temperature. The adsorption and desorption of CO molecule could be controlled by external electric field too, which is helpful to collect and storage of CO gas.

열처리 시간에 따른 메조기공 타이타니아의 비표면적 향상 연구: 가스센싱 특성 변화

낮은 열전도도 및 높은 비표면적 특성으로 흡착제 및 가스센서 등 여러 응용 분야로 연구되고 있는 규칙적 메조기공 세라믹 소재는 폐기공 메조기공 구조와 개기공 메조기공 구조로 나뉜다. 이중 폐기공 메조기공 세라믹 소재는 개기공 메조기공 세라믹 소재보다 높은 기계적 특성을 가짐에도 내부에 존재하는 기공을 이용한 비표면적 증가에 한계가 있어 응용에 제약을 가지고 있다. 본 연구팀은 규칙적 폐기공 메조기공 타이타니아(<TEX>$TiO_2$</TEX>)의 열처리 시간 변화에 따른 입자성장으로부터 폐기공 연결의 도입을 통하여 비표면적을 변화시키는 연구를 수행하고자 하였다. 열처리 시간 증가시 타이타니아 결정상의 변화는 없었으며 입자성장이 일어나게 되면서 기공구조의 무너짐 및 기공의 연결성 증가를 확인할 수 있었다. 24시간 열처리 시료의 경우, 기공률은 36.3%에 34.1%로 감소하였으나 기공의 연결도 증가로 인해 비표면적은 <TEX>$48m^2/g$</TEX>에서 <TEX>$156m^2/g$</TEX>으로 증가하였다. 이러한 비표면적의 증가는 CO 가스의 감응도 측정을 통하여 감응도가 약 7.4배 증가하는 것으로부터 확인될 수 있었다. Mesoporous ceramic materials were applied in various fields such as adsorbent and gas sensor because of low thermal conductivity and high specific surface area properties. This structure could be divided into open-pore structure and closed-pore structure. Although closed-pore structure mesoporous ceramic materials have higher mechanical property than open-pore structure, it has a restriction on the application because the increase of specific surface area is limited. So, in this work, specific surface area of closed-pore structure <TEX>$TiO_2$</TEX> was increased by anneal time. As increased annealing time, crystallization and grain growth of <TEX>$TiO_2$</TEX> skeleton structured material in mesoporous structure induced a collapse and agglomeration of pores. Through this pore structural change, pore connectivity and specific surface area could be enhanced. After anneal for 24 hrs, porosity was decreased from 36.3% to 34.1%, but specific surface area was increased from <TEX>$48m^2/g$</TEX> to <TEX>$156m^2/g$</TEX>. CO gas sensitivity was also increased by about 7.4 times due to an increase of specific surface area.

SnO2 based sensors with improved sensitivity and response‐recovery time

The objective of this work is to develop gas sensors using tin oxide (SnO2) based thin films doped by Iron (Fe) and Indium (In) for good sensitivity and better response–recovery time. The structural properties and crystalline behavior of the synthesized films is studied by X-ray diffraction (XRD). The surface morphology and particle size is investigated by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The studies performed with energy-dispersive X-ray spectroscopy (EDS) confirmed the composition of the films. The sensitivity measurements are carried out as a function of operating temperature (50–350°C) and at 400, 600 and 800ppm partial pressure of chemical inputs. The In-doped sensors exhibit maximum sensitivity for ethanol, while Fe-doped sensors showed maximum sensitivity for CO gas at its working temperatures. Most importantly, both of these sensors exhibited faster response time of the order of 1–2s and short recovery time of the order of 15–25s. Increase of texture coefficient of less dense (200) plane and reduction in band gap upon doping is found to have influence on better sensitivity.

The effect of multiwalled carbon nanotube doping on the CO gas sensitivity of TiO2 xerogel composite film

A simple sol–gel method was applied for the synthesis of 0.01wt% multiwalled carbon nanotubes (MWCNTs)-doped TiO2 xerogel composite film. The film's CO gas sensing properties were then evaluated. Doped MWCNTs were coated with TiO2 and distributed on a TiO2 xerogel matrix. The TiO2 xerogel showed an anatase structure after heat treatment at 450°C under vacuum. The specific surface area of the composite material was larger than the pure TiO2 xerogel material. The CO gas sensitivity of the MWCNTs(0.01wt%)-doped TiO2 xerogel composite film was found to be seven times higher than that of pure TiO2 xerogel film and to have good stability. This higher gas-sensing property of the composite film was due to both an increase of specific surface area and the n–p junction structure of the TiO2 xerogel coated on MWCNTs. The electrons generated from TiO2 after adsorption of CO gas induces electron transfer from the TiO2 to the MWCNTs. This induces a characteristic change in the MWCNTs from p-type to n-type, and the resistance of MWCNTs-doped TiO2 xerogel composite sensor is therefore decreased.

Post Treatment of Plasma-Polymerized SnOx Organic-Like Films with Poly Ethylene Glycol for Improving CO Gas Sensitivity

In this study, a new room temperature type gas sensor device based on plasma deposition of tetramethyltin (TMT) and O2 organically hybridized film followed by post treatment on the deposited film was developed for improving CO gas sensitivity and distinguishing from methane, butane, and carbon monoxide gases in the test environment. Plasma deposited SnOx thin film was first produced from TMT and O2 gas mixtures at room temperature, and then post treatments on the SnOx thin films were carried out by either spin coating with poly ethylene glycol (PEG) or surface grafting with p-styrenesulfonic acid sodium salt (Nass). It was found that the gas sensor spin coating post treated with PEG exhibits linear response to CO gas with the sensitivity not affected by methane and butane gases. For CO concentrations ranging from 30 to 650 ppm, steep change in the sensor resistance can be detected without warming up the sensor.

Gas sensing properties of nanostructured MoO3 thin films prepared by spray pyrolysis

Thin films of molybdenum trioxide (MoO3) were deposited on common glass using the chemical spray pyrolysis technique. A (NH4)6Mo7O244H20 solution 0.1M was used as the precursor one. The influence of substrate temperature on the crystallographic structure, surface morphology and electrical behavior of MoO3 thin films was studied. MoO3 can exist in two crystalline forms, the thermodynamically stable orthorhombic α-MoO3 and the metastable monoclinic β-MoO3 phase. XRD-spectra showed a growth of α-MoO3 phase percentage as substrate temperature increases from 420K up to 670K. Films deposited in the 500–600K range have a clearly porous surface structure of nanometer order as can be seen in SEM images. Changes up to six magnitude orders were observed in MoO3 thin films electrical resistance when films temperature varied from 100K up to 500K. The sensing property of these MoO3 films was also studied. The sensitivity was investigated in the temperature range 160 and 360K for H2O and CO gases, respectively. Both of them are of reducing nature. In all studied cases sensitivity decreases slowly as film temperature is raised. At room temperature the sensitivity changes from 12 up to 75% depending on substrate temperature. The sensitivity for CO gas was found to be lower than that of H2O.

The impact of high energy ion irradiation upon CO gas sensitivity of nanostructured GaN epilayers

Photoelectrochemically nanostructured GaN epilayers were found to exhibit good sensitivity towards CO in the temperature range from 180 to 280°C. We show that subjection of nanostructured GaN samples to 166 MeV Xe+23 ion irradiation causes considerable reduction of the gas sensitivity, while post-irradiation rapid thermal annealing results in sensitivity restoration, the effect being dependent upon the dose of irradiation and annealing temperature. A 50% restoration of the relative sensitivity is demonstrated after rapid thermal annealing for 1 min at 800°C in samples irradiated by Xe+23 ions at a dose of 1012 cm−2. The article is published in the original.

수열합성법으로 제조된 Co3O4분말을 사용한후막 가스센서의 CO 감지 특성

CO sensing thick film gas sensors using <TEX>$Co_3O_4$</TEX> powders prepared by hydrothermal reaction method, were fabricated, and their structural, electrical and CO gas sensing properties were investigated. The specific surface area of the <TEX>$Co_3O_4$</TEX> powders obtained from BET analysis was about 79.0 <TEX>$m^2/g$</TEX>. XRD and SEM results show that the thick films heat-treated at <TEX>$500^{\circ}C$</TEX> for 30 min after screen printing had the preferred orientation of (311) direction and the crystalline size was calculated to 221 <TEX>$\AA$</TEX>. The maximum activation energy obtained from the temperature-resistance characteristics was 3.11 eV in the temperature range of <TEX>$290^{\circ}C$</TEX> to <TEX>$310^{\circ}C$</TEX>. The sensitivity to 1,000 ppm CO was about 150 %. The specific surface area, crystalline size, and maximum activation energy were increased significantly and the sensitivity for CO gas was improved largely.

Low Power Consumption and High Sensitivity Carbon Monoxide Gas Sensor Using Indium Oxide Nanowire

In this paper, micro gas sensor was fabricated using indium oxide nanowire for effective gas detection and monitoring system. Indium oxide nanowire was grown using thermal CVD, and their structural properties were examined by the SEM, XRD and TEM. The electric properties for microdropped indium oxide nanowire device were measured, and gas response characteristics were examined for CO gas. Sensors showed high sensitivity and stability for CO gas. And with below 20 mw power consumption, 5 ppm CO could be detected.

When Organometallic Chemistry and Metal Oxide Nanoparticles Meet Optimized Silicon-based Gas Sensor

AbstractA robust silicon gas sensor chip (platinum heater, low deformation membrane) has been designed and successfully operated with various metal oxide nanoparticles synthesized by an organometallic route (SnO2, ZnO) and deposited by a generic ink-jet method. High quality and micron thick layers are obtained and the CO gas sensitivity is presented.

Fabrication and carbon monoxide sensing characteristics of mesostructured carbon gas sensors

We demonstrated a micro-chemoresistive gas sensing device using mesoporous carbon as the sensitive film and immobilized by dielectrophoresis (DEP) process. The mesoporous materials were characterized by X-ray diffraction (XRD) patterns, N 2 adsorption–desorption isotherms, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). N 2 adsorption–desorption isotherms shows the specific surface area of 1200 m 2/g, total pore volume is 1.2 cm 3/g of the mesoporous carbon, and the pore size distribution of mesoporous carbon yields an average pore size of 3 nm. SEM images show a rod-like morphology and TEM images show a highly ordered pore channel with linear arrays. CO gas sensor properties were measured and the resulting sensitivities were 5.7, 6.8, 8.8, 11.6, and 37.6% for concentrations of 30, 45, 60, 75, and 90 ppm, respectively. Additionally, this sensor also exhibited high sensitivity and fast response times for CO gas.

The effect of multiwalled carbon nanotube doping on the CO gas sensitivity ofSnO2-based nanomaterials

A simple in situ method is applied for the synthesis ofSnO2-coatedmultiwalled nanotubes (MWNTs), in which MWNT bundles are uniformly coated with a monolayer ofSnO2 nanoparticles(∼4 nm).A hybrid SnO2 material combined with 0.1% wt MWNTs is fabricated and its CO gas-sensing properties are evaluated.SnO2-coated MWNTs are homogeneously distributed in theSnO2 matrix and the specific surface area of the hybrid material is nearly two times higher compared topure SnO2 material. The electrical resistance is found to be dramaticallydecreased by three orders of magnitude compared to a conventionalSnO2 sensor. The CO gas sensitivity is found to be three times higher than that of aSnO2 sensor, with good stability, indicating that the addition of 0.1% wtMWNTs is effective in improving the sensitivity towards CO. A model isproposed to explain the improvement of CO gas sensitivity for our hybridMWNT/SnO2 material.

Preparation of CuO Nanopowder in Aqueous Solution by Applying Ultrasonic and its CO Gas Sensitivity

We report on a process in which CuO nanopowder was produced in a high yield by adopting ultrasonic in aqueous solution. In our experiment, CuCl2 solution was reacted with NaOH solution and NaNO2, at ambient conditions applying ultrasonic for 5 min. Precipitation was performed by varying the molar ratios of NaOH/CuCl2 and NaNO2/CuCl2. CuO nanoparticles of ~ 5 nm and spherical shape were obtained at the NaOH/CuCl2 of 2.0 and the NaNO2/CuCl2 of 0.097. Without ultrasonication, an amorphous phase was formed at these conditions. This indicates that sonochemical reaction facilitates direct formation of the nanosized CuO particles. In addition, the particle morphology varied from sphere through ellipsoid to needle forms depending on pH. In thick films prepared with the CuO powder for gas sensing, the maximum CO gas sensitivity reached 93 % at the temperature of 250 °C and depended linearly on CO concentration in log scale over the range of 10 ~ 104 ppm.

Effects of Substrate on the Characteristics of SnO2 Thin Film Gas Sensors

Effects of substrate materials on the microstructure and the sensitivity of <TEX>$SnO_2$</TEX>thin film gas sensors have been studied. Various substrates were studied, such as oxidized silicon, sapphire, polished alumina, and unpolished alumina. It was observed that strong correlation exists between the electrical resistance and the CO gas sensitivity of the manufactured sensors and the surface roughness of <TEX>$SnO_2$</TEX>thin films, which in turn was related to the surface roughness of the original substrates. X<TEX>$SnO_2$</TEX>thin film gas sensor on unpolished alumina with the highest surface roughness showed the highest initial resistance and CO gas sensitivity. The transmission electron microscopy observation indicated that shape and size of the columnar microstructure of the thin films were not critically affected by the type of substrates.