温度对非色散红外气体分析仪测量准确度的影响

分析了温度对非色散红外气体分析仪测量准确度的影响，并提出温度补偿方案。参考HITRAN数据库，以某型CO2红外气体分析仪为例，分析其在5～40℃的测量准确度。研究结果表明，非色散红外气体分析仪指示值与温度呈非线性正相关，原因是气体吸收、光源、滤波器、检测器、吸收池等元素交叉作用。温度是影响非色散红外气体分析仪测量准确度的重要参数。该研究对非色散红外气体分析仪的温度补偿研究具有一定参考意义。     

改性碳纳米管气体传感器

碳纳米管气体传感器具有灵敏度高、响应速度快、尺寸小和能在室温下工作等诸多优点,是一种很有前景的气体传感器.然而本征碳纳米管气体传感器只对少数几种气体如NH3、O2、NO2和SO2敏感,检测范围有限;而且这类传感器的检测灵敏度和选择性也有待提高.研究表明对碳纳米管进行改性可以克服这些缺陷.目前已有的改性方法主要包括对碳纳米管表面有机修饰、对碳纳米管掺入无机杂原子以及径向力学变形等.本文对改性碳纳米管气体传感器研究的最新进展进行了综述,分析了上述改性方法在扩大碳纳米管气体传感器的检测范围、提高检测灵敏度和选择性方面的优势和不足,并对其研究前景进行了展望.     

气敏新材料MXenes在呼出气体传感器中的应用

电子鼻结合人工智能对呼出气进行检测、分析和识别已成为非侵入性医疗检测领域的研究热点。然而,目前已报道的气体传感材料尚不能同时满足高灵敏度、高选择性和稳定的室温检测,阻碍了气体传感器在医疗健康领域的应用及发展,寻找合适的传感材料具有重要的意义和挑战。新型二维层状纳米材料MXenes具有种类多、比表面积大、导电性能强、表面含有丰富的官能团以及能带宽度可调等优异性能,是高灵敏、低能耗气体传感器的明星候选材料。本综述针对MXenes基材料的特殊结构,总结梳理了MXenes基材料在气体传感中的最新研究成果,聚焦于MXenes材料的气体传感机理和改性方法,对MXenes材料用于气体传感依然存在的问题和挑战进行深入探讨。     

碳纳米管气体传感器研究进展

碳纳米管具有一维纳米结构、高表面吸附能力、良好的导电性和电子弹道传输特性等优异的力学、电学、物理和化学性能,成为制作纳米气体传感器的理想材料之一.近年来,各国研究者广泛开展了碳纳米管气体传感器的研究工作,并取得了许多显著成果.研究结果表明,碳纳米管气体传感器具有灵敏度高、响应速度快、尺寸小、能耗低和室温下工作等诸多特点.本文结合本研究小组近年来在碳纳米管气体传感器领域所做的大量研究工作,从环境监测、医学检测和国防军事等方面,对碳纳米管气体传感器取得的研究进展进行了综述,同时也阐述和分析了碳纳米管气体传感器的工作原理和制作过程.尽管面临诸多挑战,随着研究的不断深入,碳纳米管气体传感器仍有可能凭借其独特的性能优势成为当前商业应用气体传感器的有力竞争者.     

类金刚石薄膜修饰传感器在电化学中的应用

综述了类金刚石薄膜及其修饰的传感器特性以及制备工艺,介绍了类金刚石薄膜修饰的传感器在生物检测、电化学微重力测量、痕量金属检测、氢离子选择场效应晶体管和气体检测等领域的应用,并对类金刚石薄膜修饰传感器在电化学相关领域的应用进行了展望。     

基于人体呼气检测应用的气体传感器

人体呼气中挥发性有机物浓度的变化与某些疾病密切相关，通过分析人体呼气中的挥发性有机物来诊断疾病是一种无创非侵入性、操作方便的手段，近年来在疾病诊断和早期筛查方面的应用中受到越来越多的关注。目前检测呼气中挥发性有机物的设备主要有两类：质谱类分析仪器和气敏传感器。气敏传感器具有易集成、小型化、成本低、操作简单等优势，在未来大规模人群疾病的诊断和早期筛查中具有广阔的应用前景。本综述系统地阐述了气敏传感器的工作机制、传感器性能、不同敏感材料的应用现状和不同的气体传感器类型在人体呼气检测中的应用情况，同时介绍了与部分疾病存在关联的人体呼气中挥发性有机物的种类，之后对呼气采样手段和目前常用的数据处理方法也进行了简单介绍。最后指出了目前气体传感器技术在呼气检测方面存在的问题，并展望了气体传感器技术在人体呼气检测中的未来发展前景。     

烟道气国际比对中低浓度一氧化碳的精确测量

研究了烟道气体中低浓度一氧化碳(CO)的精确分析方法.结果显示,使用非色散红外光谱法的重复性明显优于气相色谱法,但烟道气中高浓度二氧化碳( CO2)的存在会影响光谱法对CO的精确测量,因此测量样品时采用含有CO2成分的标准气体作为标准.由不确定度评定结果及比对样品重复性测量结果可知,本方法精确度高.通过参加国际计量局物...     

类金刚石薄膜修饰的传感器在电化学中的应用

综述了类金刚石薄膜及其修饰的传感器特性以及制备工艺,介绍了类金刚石薄膜修饰的传感器在生物检测、电化学微重力测量、痕量金属检测、氢离子选择场效应晶体管和气体检测等领域的应用,并对类金刚石薄膜修饰传感器在电化学相关领域的应用进行了展望。     

超支化敏感聚合物基于QCM检测痕量TNT爆炸物

为对TNT类爆炸物进行痕量检测,以石英晶体微天平(QCM)传感器为平台,用具有氢键酸性的氟化醇为敏感端基的超支化敏感聚合物材料构造了化学传感器。制备的QCM传感器可以在室温下对2.2×10~(-10)mol/L浓度以上的TNT气体进行响应;连续循环检测3次TNT气体未见信号衰减;对H_2O、乙醇、H_2、H_2S、SO_2、甲烷和NO_2等气体有良好的抗干扰能力;QCM传感器可以用于对TNT类爆炸物的痕量检测。     

钼酸铋基气敏材料研究进展

气体传感器被广泛应用于检测工业和家庭中有毒有害气体。气体敏感材料是气体传感器中重要的组成部分,敏感材料的性质决定了气体传感器的性能。研制精度高、检测快、集成度高的气体检测器迫在眉睫。钼酸铋作为一种新型双金属氧化物气敏材料,具有高选择性、高敏感度的优势。本文从气敏机理、形貌控制、掺杂和复合材料构建方面对近年来钼酸铋作为气敏材料的研究进行了总结,并对钼酸铋基气敏材料未来的研究方向进行了展望。     

Stability of a NDIR analyser for CO2 at atmospheric concentration

Carbon dioxide monitoring is significant in the environmental field since this gas plays an important role in the greenhouse effect. In order to determine CO2 concentration and to develop simulation models, it is necessary to carry out measurements which are accurate and comparable in time and space, i.e. SI-traceable. Non-dispersive infrared (NDIR) analysers are employed for CO2 measurements, as they are precise and stable. In order to achieve traceability, such instruments have to be characterized and calibrated. At the Istituto di Metrologia "G. Colonnetti"--CNR, a procedure for calibrating NDIR analysers for CO2 at atmospheric level was developed, which enables to calculate a correction for the analyser output. In addition, a complete uncertainty analysis was carried out and a correct traceability chain was established. The goal of the present work is the study of the stability of a NDIR analyser by repeating calibrations during three years and comparing the correction curves obtained to identify a proper re-calibration interval for such analysers. The investigated instrument has good repeatability and reproducibility, hence satisfactory stability during time, as shown by the short-term and long-term compatibility of calibration curves.     

Discrepancy in infrared measurement results of carbon monoxide in nitrogen mixtures due to variations of the 13C/12C isotope ratio

Significant errors in the non-dispersive infrared (NDIR) analyses of carbon monoxide (CO) can be made when the ¹³C/¹²C isotope ratio in the sample and the calibrant differ significantly. This paper shows that variations in the ¹³C/¹²C isotope ratio of 5×10⁻² mol/mol CO in nitrogen mixtures on three different NDIR CO analysers may lead to serious deviations in the instrument response, whereas the instrument response using GC-TCD is unaffected. The observed deviations in the assigned amount-of-substance fraction CO for a ¹³C depleted mixture vary from +2 to −5% relative to the gravimetric amount-of-substance fraction for different NDIR analysers. A GC-MS method has been developed to perform a pre-screening of the isotopic composition of CO in nitrogen mixtures. This method proved to be an adequate tool to measure differences in the ¹³C/¹²C ratio. Based on the GC-MS results a suitable measurement technique can be selected, or information about a possible error in NDIR analysis can be given to the producer or user of the calibration gas mixture. Presented at 3. International Gas Analysis Symposium, October 6–8, 2004, in Amsterdam     

Sensing performance of CuO/Cu2O/ZnO:Fe heterostructure coated with thermally stable ultrathin hydrophobic PV3D3 polymer layer for battery application

Gas sensors are demanded in many different application fields. Especially the ever-growing field of batteries creates a great need for early hazard detection by gas sensors. Metal oxides are well known for gas sensing; however, moisture continues to be a major problem for the sensors, especially for the application in battery systems. This study reports on a new type of moisture protected gas sensor, which is capable to solve this problem. Sensitive nano-materials of CuO/Cu₂O/ZnO:Fe heterostructures are grown and subsequently coated with an ultrathin hydrophobic cyclosiloxane-polymer film via initiated chemical vapor deposition to protect the sensor from moisture. The monomer 1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane is combined with the initiator perfluorobutanesulfonyl fluoride to obtain hydrophobic properties. Surface chemistry, film formation and preservation of functional groups are confirmed by X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. It turns out that the hydrophobicity is retained even after annealing at 400 °C, which is ideal for gas sensing. Molecular distances in the polymer nanolayer are estimated by geometry optimization via MMFF94 followed by density functional theory. Compared with unprotected CuO/Cu₂O/ZnO:Fe, the coated CuO/Cu₂O/ZnO:Fe exhibit a much better sensing performance at a higher relative humidity, as well as tunability of the gas selectivity. This is highly beneficial for hazard detection in case of thermal runaway in batteries because the sensors can be used under high concentrations of relative humidity, which is ideal for Li–S battery applications.     

Evolved gas analysis (EGA) of brick clays

Using a system based on non-dispersive infrared (NDIR) detectors, evolved gas analysis (EGA) was able to identify and quantify the principal volatiles produced by heating powdered samples of UK brick clays. From these results, atmospheric emissions likely to result from brick production can be predicted. In addition, EGA results for extruded brick clay test pieces are significantly different from those of powdered samples. Within an extruded brick clay body, evolved gases are contained within a pore system and evolved gas-solid phase reactions also occur. This EGA study provides further evidence on the nature of firing reactions within brick clay bodies. The qualitative and quantitative influence of heating rate — a key process condition in brick manufacture — on gas release is also outlined.Dedicated to Dr. Robert Mackenzie on the occasion of his 75th birthday     

Tailoring the structure of metal oxide nanostructures towards enhanced sensing properties for environmental applications

The present article reviews recent works in our laboratory about the sensing properties to toxic gases using nanostructured WO(3), TiO(2), FTiO(2), and CuO functionalized quartz crystal microbalance (QCM) sensors. WO(3) and TiO(2) functionalized QCM sensors have much shorter response time than those functionalized by conventional hydrogen-bond acidic branched copolymers for detection of dimethyl methylphosphonate (DMMP). FTiO(2) functionalized QCM sensors can improve the gas sensing characteristics by shortening the response time but at the price of partial irreversibility. The sensing mechanism was examined by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Varied CuO nanostructures were synthesized by simple modulation of reaction conditions. All the as-prepared CuO was applied on QCM resonators and explored for HCN sensing. Surprisingly, responses of all the sensors to HCN were found to be in an opposite direction as compared with other common volatile substances, offering excellent selectivity for HCN detection. The sensitivity was very high, and the response and recovery were very fast. Comparison of the specific surface areas of CuO nanostructures showed that CuO of higher surface area is more sensitive than that of lower surface area, indicating that the specific surface area of these CuO nanostructures plays an important role in the sensitivity of related sensors. Based on experimental results, a sensing mechanism was proposed in which a surface redox reaction occurs between CuO and Cu(2)O on the CuO nanostructures reversibly upon contact with HCN and air, respectively. The CuO functionalized QCM sensors are considered to be a promising candidate for trace HCN gas detection in practical applications.     

Uncertainty estimation in chemical measurements: carbon dioxide determination at atmospheric concentration

The present work deals with the evaluation of measurement uncertainty in the determination of carbon dioxide (CO2) concentration in atmosphere, given the high relevance of this greenhouse gas that influences earth climate. In order to carry out CO2 measurements, non dispersive infrared (NDIR) analysers are usually employed as they are stable and scarcely affected by interferences from other air components or pollutants. Typical uncertainty sources are the resolution of the analyser, its time drift and the contributions due to instrument calibration, which is required in order to produce traceable measurement results. The calibration uncertainty takes into account the uncertainty of the composition of the calibration gas mixtures, the instrument repeatability and the possible or residual lack of fit of the adopted mathematical model.     

Dual cantilever enhanced photoacoustic detector with pulsed broadband IR-source

The cantilever enhanced photoacoustic (CEPA) trace gas detection was combined with an electrically modulated broadband infrared (EMBIR) source. The high sensitivity of the detection method was further improved by using two cantilever sensors on the opposite walls of the photoacoustic cell in order to suppress noise. Methane (CH₄) gas was used to demonstrate the sensitivity of the method yielding a detection limit of 0.5 ppm with 5 s sample integration time employing an optical filter with a center wavenumber 2950 cm⁻¹. The achieved result is very good with a low power infrared source and enables the utilization of the benefits of such a source: low price and power consumption, easily controlled and simple electrical modulation of the radiation intensity and absence of the mechanical chopper and its noise. The structure of the source enables a relatively high pulse rate to be used as the modulating frequency. Optical filters can be used to select the wavenumber region for the selective detection of different gases.     

Macroporous silicon and its application in sensing

Periodic silicon nanostructures can be used for different kinds of gas sensors depending on the analyte concentration. First, we present an optical gas sensor based on the classical non-dispersive infrared technique for ppm-concentration using ultra-compact photonic crystal gas cells (Pergande et al., 2011) [1]. It is conceptually based on low group velocities inside a photonic crystal gas cell and anti-reflection layers coupling light into the device. Secondly, we report on silicon nanotip arrays (Gesemann et al., 2011) [2], suitable for gas ionization in ion mobility microspectrometers (micro-IMS) having detection ranges in principle down to the ppt-range. Such instruments allow the detection of explosives, chemical warfare agents, and illicit drugs, e.g., at airports. Third of all, we describe the thermal emission properties of heated silicon photonic crystals (Gesemann et al., 2010) [3], revealing a photonic stop gap effect or strong silicon oxide emission, depending on the setup. All silicon microstructures have been fabricated by photo-electrochemical etching of silicon.     

Traceability in routine chemical measurements: an example of application in the determination of CO2 at atmospheric concentration

In routine chemical measurements traceability can be achieved by using analytical instruments calibrated against primary reference materials. In the present work the calibration of a CO₂ non-dispersive infrared (NDIR) analyzer with measuring range 0–2000 μmol/mol of CO₂ and a resolution of 5 μmol/mol is reported. A procedure with working reference gas mixtures (WRMs) has been adopted, which requires seven calibration points. Primary reference gas mixtures (PRMs) are used to validate WRMs in a narrower range around the average atmospheric CO₂ concentration value. In this range the relative uncertainty reached is of the order of some parts in 10³ and the corrections are between 1 μmol/mol and 5 μmol/mol. Received: 16 March 2000 Accepted: 27 November 2000