空芯光波导在光谱气敏检测中的应用

空芯光波导(HWG)用于光谱气体检测中,既可以实现光路的传输,又可以充当气体样品池实现长光程高灵敏度测量,具有体积小,响应时间快、成本低、光路稳定灵活等优点。介绍了基于镀银/碘化银的空芯光波导(Ag/AgI-HWG)、光子带隙空芯光波导(PBG-HWG)和基片集成空芯光波导(iHWG)等类型的空芯光波导,并总结了近年来空芯光波导在光谱气敏检测中的研究及进展,梳理了其应用方式及应用领域。研究表明,空芯光波导替代传统的气体池与傅里叶变换红外光谱(FTIR)、激光吸收光谱和拉曼光谱等不同的光谱技术结合已取得一系列成果,且已经应用于环境监测、呼气诊断和工业过程检测和控制等领域。其中,基于中红外激光吸收光谱的空芯光波导传感器组成相对简单,成本较低,与各类光波导的兼容性和环境适应性较强,发展前景较好。总之,随着激光技术、光波导技术和光谱技术的发展,基于空芯光波导的光谱气体检测正在迅速发展,并逐步由实验室走向现场应用。     

Methods of highly sensitive gas analysis of molecular biomarkers in study of exhaled air

The methods of highly sensitive gas analysis of molecular biomarkers in exhaled air were reviewed. Specific features of the analysis of the chemical content of exhaled air at the level of microconcentrations as well as general requirements for the applied instrumental approach were discussed. The experimental data demonstrating a relationship between some light gas molecules and organ pathology and the possibility of using such molecules as biomarkers were reviewed. Basic approaches to highly sensitive gas analysis on the basis of gas chromatography, mass spectroscopy, electrochemical sensors, UV chemiluminescence, and IR spectroscopy were considered from the point of view of their possible application to the analysis of breath content. Characteristics of the spectral gas analysis based on tunable diode lasers were analyzed in details. The possibility of applying diode laser spectroscopy to biomedical diagnostics based on highly sensitive gas analysis of human breath content was discussed.     

基于Fluoral-P衍生物的新型甲醛探针的光谱特性研究

甲醛(HCHO)是目前室内空气主要污染物之一,长期暴露在过量甲醛环境中会对人的眼睛、皮肤、呼吸器官等产生严重危害,甚至可能导致神经系统功能的丧失[1]以及耳、鼻和喉癌[2]。因此,快速、高效、准确地实现甲醛气体的检测,对于保障人类健康具有重大的意义。当前有很多种方法可以用于甲醛气体的检测。例如,气相色谱法(GC)[3]和高效液相色谱法(HPLC)[4],色谱仪器能够提供低至μg·m-3级别的浓度检测,但是仪器较为大型笨重,并且检测非常耗时,难以实现实时连续地对甲醛气体浓度的监测;基于气敏薄膜的半导体气体传感器具备响应时间短,稳定性高以及可连续监测等优点,然而这类传感器通常检测限较高(>300 μg·m-3),并且选择性差[5];基于酶的生物传感器通常有较好的灵敏性和选择性,但是其热稳定性通常较差,这严重限制了其应用[6]。比色法和荧光法由于响应速度快,灵敏度高,检测限低,选择性好以及传感器简单便宜等特点,被广泛地应用于甲醛气体传感器的设计中去[7-9]。这种方法是利用探针分子与甲醛发生特异性结合,形成新的物质,从而引起探针吸收光谱的变化或者发出荧光,实现对甲醛的定量测量。Descamps等使用4-氨基-3-戊烯-2-酮(Fluoral-P)作为探针分子,设计了一种手提式的甲醛检测仪[10]。Fluoral-P是一种烯氨酮结构的物质,能与甲醛特异性结合形成环状化合物3,5-diacetyl-1,4-dihydrolutidine(DDL)。由于Fluoral-P自身的特征吸收带与DDL的吸收带相隔较远,同时与甲醛结合后能够产生大斯托克斯位移的荧光峰,因而被广泛应用于甲醛检测。然而,Fluoral-P在空气中有水分子存在的情况下极其不稳定,容易发生水解,形成乙酰丙酮和氨气,严重限制了Fluoral-P在甲醛检测上的应用[10]。采用紫外可见吸收光谱、稳态荧光光谱和气相色谱质谱(GC-MS)技术研究了Fluoral-P的一种衍生物,4-氨基-1,1,1-三氟-3-丁烯-2-酮(3F-FP),与甲醛溶液相互作用的光学和化学特性。实验发现,Fluoral-P的水解速率为k＝1.555 9×10-5 L2·mol-2·s-1,然而,3F-FP具有非常低(接近0)的水解速率,水溶液环境下表现出了极好的稳定性。同时,3F-FP可以与甲醛反应生成一种类似DDL的环状化合物6F-DDL,使得3F-FP在430 nm处出现了一个新的吸收带,并且在峰值489 nm处的荧光强度也得到了明显增强,增强因子为12,在峰值处的荧光增长速率为k=7.881×103 h-1。下一步我们将使用多孔玻璃作为3F-FP探针的载体,不仅可以提高3F-FP分子浓度,也可以增加探针分子与甲醛的接触表面积[11],荧光增长速率还可以得到进一步的提高,因此3F-FP分子在甲醛气体检测领域具备了良好的应用前景。     

Mass Spectrometry Coupled to Thermogravimetry (TG-MS) for Evolved Gas Characterization: A Review.

INTRODUCTION

Combining thermal analysis (TA) with gas-analykal techniques significantly enhances the possibilities for correctly interpreting the mechanism of thermally induced reactions, which involve the formation of gaseous species. Several techniques can be used for evolved gas analysis (EGA), ranging from simple, non-specific detection to the more elaborate multidimensional/multifunctional methods, such as gas chromatography (GC), infrared spectroscopy (IR) or mass spectrometry (MS), for gas detection and analysis [1]. While the GC methods were used as early as the 1960s [2], EGA by FTIR was described much later and was used for the analysis of pyrolytic and combustion products. Presently, there are several commercial FTIR systems available that can be coupled to a thermogravimetric analyzer (TGA), and a broad range of applications have been investigated by this important hyphenated technique [3].     

Review on multi gas detector using infrared spectral absorption technology

To provide some references for researchers engaged in infrared multi gas detection, this study introduced the infrared multi gas detection system thoroughly from infrared light source, infrared detector, optical multiplexing structure, and detection method. Currently, the coherent source represented by quantum cascade laser has replaced the traditional incoherent source like thermal radiant infrared light source and became the dominant light source in infrared multi gas detection. Accordingly, the infrared photodetector is widely used. The optical multiplexing structure based on the “multiplexing thought” is the core of infrared multi gas detection system. It mainly includes the single-source multiplex detection structure and multi-source multiplexing detection structure. Nondispersive infrared spectroscopy, long optical distance spectroscopy, wavelength/frequency modulation spectroscopy, cavity enhancement spectroscopy, and photoacoustic spectroscopy are major detection methods used in the infrared multi gas detection. This has important significance to many fields, such as industrial and agriculture production, environmental monitoring, life science, etc.     

大气压低温等离子体发射光谱检测含磷有毒气体（模拟剂）方法研究

化学气体毒剂杀伤快、易扩散、难处置,一旦使用或泄露将对国家安全和社会稳定造成巨大威胁,因此有必要发展一种可以现场实时检测化学毒害气体的方法。目前,传统气体检测方法主要包括红外吸收光谱、气相色谱/质谱、离子迁移谱和各种气体传感器等,但其便携性、灵敏度、广谱性难以兼得,无法完全满足现场检测需求。基于发射光谱（OES）响应快、灵敏度高、广谱性好、可重复性强的独特优势,提出了一种大气压低温等离子体发射光谱检测技术。分别以纳秒高压脉冲、直流自脉冲和微波作为等离子体激励源,使用毒性较小的甲基膦酸二甲酯（DMMP）作为沙林模拟剂进行发射光谱检测;以乙醇作为环境有机干扰物,对乙醇与DMMP光谱进行了主成分分析;并探究了放电脉冲频率与特征光谱强度的关系。结果表明,三种激励源产生的等离子体都可辨别出DMMP特征光谱：P原子特征谱线波长为213.82和215.09 nm,PO基团谱带波长为253.67和255.6 nm。光谱识别度方面,使用微波激励源时DMMP特征光谱最为明显,而使用纳秒脉冲与直流自脉冲激励源时光谱连续本底强烈。方法适用性方面,微波等离子体无电极污染、但需要氩气维持,可作为建立毒害气体发射光谱数据库的手段;而纳秒脉冲与直流自脉冲激励源可在常压空气环境中直接检测。三种激励形式下等离子体区域都存在气体加热效应,微波等离子体气体温度最高（约1 300 K）,而纳秒脉冲和直流自脉冲放电气体温度相近（分别约为980和880 K）。研究发现,提升脉冲重复频率可以显著增加DMMP特征光谱强度,其与脉冲频率在1~40 kHz内呈线性关系（相关系数大于0.98）。所提出的大气压等离子体发射光谱检测方法具有响应快、操作简单等优点,可扩展性强、具有小型化潜力,为毒害气体快速检测装备研发提供了技术参考。     

Hollow-waveguide-based carbon dioxide sensor for capnography

A CO2 sensor for capnography, based on a hollow waveguide(HWG) and tunable diode laser absorption spectroscopy(TDLAS), is presented; the sensor uses direct absorption spectroscopy and requires neither frequent calibration nor optical filters, giving it a significant advantage over existing techniques. Because of the HWG, the CO2 measurement achieved a concentration resolution of 60 ppm at a measurement rate of 25 Hz, as characterized by Allan variance. The length of the HWG was selected to efficiently suppress the optical fringes. This setup is perfectly suited for the detection of CO2 by capnography, and shows promise for the potential detection of other breath gases.     

Monitoring insect pest infestation via different spectroscopic techniques

Nowadays, monitoring and observing insect pest populations is a major and crucial issue in agriculture, especially for crop protection. Spectroscopic techniques are well recognized for detecting and monitoring insect pests in the field and also the internal quality of fruit. There are several spectroscopic techniques with specific characteristic features, including mass spectrometry, ultraviolet–visible spectroscopy, infrared spectroscopy, and nuclear resonance spectroscopy. Nevertheless, limitations and complexity are the constraints of these technologies. In this paper, the spectroscopic and imaging spectroscopic techniques are discussed, compared, and investigated, namely fluorescence light detection and ranging (LIDAR) to study the fluorescence of diverse types of planthopper (Hemiptera) and moth (Lepidoptera), visible and near-infrared (Vis/NIR) spectroscopy to detect internal insect-infested jujubes, NIR spectroscopy to determine spectral properties of oil palm bagworms, hyperspectral transmittance image for detecting insect-damaged vegetable soybeans, and remote sensing measurement to detect bagworm infestation in oil palm plantations. These techniques are found to be reliable methods for better monitoring of insect pest movement in the harvested plant and in the ground, for the detection of insect-damaged vegetable soybeans and internal insect infestation in jujubes, and for the determination of oil palm bagworm spectral properties.     

光谱分析方法在同位素检测中的研究和应用进展

同位素在核工业为主的各种工业生产中受到广泛的关注,并推动着地质学、材料科学、化学等相关学科的发展。近年来,基于光谱分析原理的同位素分析方法的开发逐渐受到关注。虽然多接收杯电感耦合等离子体质谱（MC-ICP-MS）、热电离质谱（TIMS）和气体同位素质谱（IRMS）等质谱技术是同位素分析的标准方法,但是这些质谱方法通常需要复杂的样品前处理流程以及频繁的仪器维护。光谱分析方法在这些方面有着自身独特优势,甚至可以满足现场实时快速的同位素分析,并在核工业同位素分析和传统稳定同位素分析领域已经取得了日益广泛的应用。随着光谱仪器关键部件和数据处理方法的进一步发展,极大地改善了光谱法同位素分析的性能（灵敏度、分辨率和精密度）,使光谱分析方法被逐渐开发并应用于环境和地质同位素分析领域。综述了光谱分析方法在同位素分析（定量或定性）领域的主要进展,从光谱分析原理的角度归类为发射光谱（原子发射、分子发射、拉曼光谱）和吸收光谱（原子吸收、分子吸收）两大类。着重讨论了光谱法进行同位素分析的基本原理、发展历程以及重要进展,简述了与质谱法相比的优缺点。针对仍然有待突破的技术难点,展望了光谱法应用于同位素分析的发展前景。该综述可为光谱分析方法在同位素检测中的发展方向提供重要参考。     

Integrated cavity output spectroscopy measurements of NO levels in breath with a pulsed room-temperature QCL

A cavity-enhanced spectrometer is developed for detection of exhaled nitric oxide in human breath. A thermoelectrically cooled, pulsed, quantum cascade laser, coupled to a high-finesse cavity, is used for trace-gas measurements. The trace-gas analyzer operates at 5.2 microns and utilizes integrated cavity output spectroscopy. Effective optical path lengths of 1.5 km are achieved in a 50-cm-length cell with a sample volume of 60 mL. The instrument is also capable of simultaneously measuringCO2 concentration in exhaled breath. Measurements were performed on human breath samples as well as simulated breath samples. Here we report a detection limit of ≤ 1 ppbv in 4 s for NO in human breath samples.     

光纤光热干涉气体检测技术研究进展

本文阐述光纤光热干涉气体检测的基本原理,从光纤光热相位调制的产生、动态过程、探测方法以及响应时间等方面出发,综述本研究组在光纤光热干涉气体检测方面的最新工作进展.光纤光热干涉技术具有灵敏度高、动态范围大、测量不受散射及其他损耗影响等优势,能够实现小型化、多点复用、组网及远程监测,在环境、医疗、安防等领域具有重要的应用.     

Spectroscopic monitoring of NO traces in plants and human breath: applications and perspectives

Optical methods based on quantum cascade lasers (QCLs) are becoming popular in many life science applications. We report on two trace gas detection schemes based on continuous wave QCLs for on-line detection of nitric oxide (NO) at the sub-part-per-billion level by volume (ppbv, 1:10^?9), using wavelength modulation spectroscopy (WMS) and Faraday rotation spectroscopy (FRS) at 1894 cm^?1 and 1875.73 cm^?1, respectively. Several technical incremental steps are discussed to further improve the sensitivity of these methods. Examples are included to demonstrate the merits of WMS-based sensor: direct monitoring of NO concentrations in exhaled breath, and from plants under pathogen attack. A simple hand-held breath sampling device that allows single breath collection at various exhalation flows (15, 50, 100 and 300 mL/s, respectively) is developed for off-line measurements and validated in combination with the WMS-based sensor. Additionally, the capability of plants to remove environmental NO is presented.     

Secondary ion mass spectrometry and optical characterization of Ti:LiNbO3 optical waveguides

Secondary ion mass spectrometry (SIMS) and m-lines spectroscopy have been applied to study Ti:LiNbO₃ slab optical waveguides with high titanium surface concentration. By combining the two techniques, a saturation in the dependence of the refractive index change on the dopant concentration has been found. By the use of SIMS in image mode, the lateral diffusion of titanium in Ti:LiNbO₃ channel waveguides has been observed and analyzed.     

Selected optoelectronic sensors in medical applications

Optoelectronic technology plays an important role in medical diagnosis. In the paper a review of some optoelectronic sensors for invasive and non-invasive human health test is presented. The main attention is paid on their basic operation principle and medical usefulness. The paper presents also own research related to developing of tools for human breath analysis. Breath sample unit and three gaseous biomarkers analyzer employing laser absorption spectroscopy designed for clinical diagnostics were described. The analyzer is equipped with sensors for CO, CH₄ and NO detection. The sensors operate using multi-pass spectroscopy with wavelength modulation method (MUPASS-WMS) and cavity enhanced spectroscopy (CEAS).     

A calibration-free ammonia breath sensor using a quantum cascade laser with WMS 2f/1f

The amount of ammonia in exhaled breath has been linked to a variety of adverse medical conditions, including chronic kidney disease (CKD). The development of accurate, reliable breath sensors has the potential to improve medical care. Wavelength modulation spectroscopy with second harmonic normalized by the first harmonic (WMS 2f/1f) is a sensitive technique used in the development of calibration-free sensors. An ammonia gas sensor is designed and developed that uses a quantum cascade laser operating near 1,103.44 cm^?1 and a multi-pass cell with an effective path length of 76.45 m. The sensor has a 7 ppbv detection limit and 5 % total uncertainty for breath measurements. The sensor was successfully used to detect ammonia in exhaled breath and compare healthy patients to patients diagnosed with CKD.     

2.0μm附近模拟呼吸气体中~(13)CO_2/~(12)CO_2同位素丰度的高精度实时在线测量

采用可调谐二极管激光吸收光谱技术,结合一新型多通池搭建了一套模拟呼吸气体中CO_2同位素丰度的测量装置.气体的压强、温度和流速被很好地控制且均能保持长期的稳定性;采用三次多项式拟合光谱基线,对光谱进行归一化,很好地消除了功率变化对测量结果的影响;利用移窗-回归技术消除频率漂移对同位素丰度测量的影响.实验结果表明:移窗-回归法的引入不仅延长了系统的稳定时间,还提高了系统的测量精度;小波去噪的应用获得了比多光谱平均法高2倍的信噪比;系统的稳定时间为100 s;Kalman滤波后系统测量精度为0.067‰.     

All-optical mass sensing with coupled mechanical resonator systems

With the small mass, large quality-factor and high frequency, mechanical resonators (MRs) will ultimately find usage in a broad range of applications, such as electrometry, optomechanical/electromechanical signal processing, and mass detection. In this review, we focus on a particular MR application: mass sensing in an all-optical domain. Compared to the mass detection based on the electrical techniques, we have proposed an optical protocol to weigh the external particles deposited onto the surface of a mechanical resonator. This protocol, which is so far the first method to deal with the mass sensing in an all-optical domain, is based on some coupled mechanical resonator systems. Here we review our recent optical mass sensors comprehensively. These all-optical mass sensors have the potential to break through the limitation of frequency restriction and to enhance the sensitivity of mass detection.     

Cavity-enhanced direct frequency comb spectroscopy

Cavity-enhanced direct frequency comb spectroscopy combines broad spectral bandwidth, high spectral resolution, precise frequency calibration, and ultrahigh detection sensitivity, all in one experimental platform based on an optical frequency comb interacting with a high-finesse optical cavity. Precise control of the optical frequency comb allows highly efficient, coherent coupling of individual comb components with corresponding resonant modes of the high-finesse cavity. The long cavity lifetime dramatically enhances the effective interaction between the light field and intracavity matter, increasing the sensitivity for measurement of optical losses by a factor that is on the order of the cavity finesse. The use of low-dispersion mirrors permits almost the entire spectral bandwidth of the frequency comb to be employed for detection, covering a range of ～?10% of the actual optical frequency. The light transmitted from the cavity is spectrally resolved to provide a multitude of detection channels with spectral resolutions ranging from several gigahertz to hundreds of kilohertz. In this review we will discuss the principle of cavity-enhanced direct frequency comb spectroscopy and the various implementations of such systems. In particular, we discuss several types of UV, optical, and IR frequency comb sources and optical cavity designs that can be used for specific spectroscopic applications. We present several cavity-comb coupling methods to take advantage of the broad spectral bandwidth and narrow spectral components of a frequency comb. Finally, we present a series of experimental measurements on trace gas detections, human breath analysis, and characterization of cold molecular beams. These results demonstrate clearly that the wide bandwidth and ultrasensitive nature of the femtosecond enhancement cavity enables powerful real-time detection and identification of many molecular species in a massively parallel fashion.     

Determination of (13)CO(2)/(12)CO(2) Ratio by IRMS and NDIRS

Abstract Breath tests using (13)C-labelled substrates require the measurement of (13)CO(2)/(12)CO(2) ratio in breath gas samples. Next to isotope ratio mass spectrometry (IRMS), which is very sensitive but also complex and expensive, alternatively isotope selective nondispersive infrared spectrometry (NDIRS) can be used to determine the (13)CO(2)/(12)CO(2) ratio in expired breath. In this study we compared NDIRS- with IRMS-results to investigate whether the less expensive and very simply to operate NDIRS works as reliable as IRMS. For this purpose we applicated 1-(13)C-Phenylalanine to patients with advanced liver cirrhosis and healthy volunteers and took duplicated breath samples for IRMS and NDIRS at selected time points. Our data show a good correlation between these two methods for a small number of samples as required for simple breath tests. Longer series, where repeated measurements are required on the NDIRS instrument lead to a decreasing correlation. This indicates the superiority of IRMS concerning (13)CO(2)-kinetics over longer time periods.     

Isomer-resolved ion spectroscopy

We demonstrate the isomer-resolved spectroscopy of gas-phase ions, with different geometries separated prior to spectroscopic probe using ion mobility techniques. Specifically, ring and chain isomers of carbon cluster anions with 10;-12 atoms have been separated by ion mobility/mass spectrometry and examined by photoelectron spectroscopy. This methodology should also apply to other ion spectroscopies, including IR photodissociation.