Optical chemical sensors for the detection of explosives and associated substances

The main analytical characteristics of optical chemical sensors for detecting the vapors and microparticles of explosives and associated substances are compared. The limits of detection, sensitivity, sensor setting time (response speed) and recovery time after the action of an analyte, and the selectivity of fluorescence sensors, chemiluminescence sensors, surface-enhanced Raman sensors, surface plasmon resonance sensors, absorption integrated optical waveguide sensors, waveguide interferometric sensors, and ring resonator based sensors. The effectiveness of the use of nanosized structures and bio- and nanostructured specific coatings in optical sensors is analyzed.     

多荧光光纤传感器及其在混合溶剂检测中的应用

微纳光纤与其他微纳结构的集成可以拓展荧光光纤传感器检测范围和集成度,是光纤传感领域的研究热点。目前,国际上关于荧光光纤传感器这一领域的研究还处于单一检测物荧光响应的阶段,对多检测物的多通道荧光响应仍存在很大挑战。本文结合微纳光纤的光波导性能以及有机荧光材料的光功能特性,制备了能够同时激发和收集多种荧光的微纳光纤,并将之应用于高性能荧光光纤传感器的制备。通过选用不同荧光波长的有机材料与凝胶掺杂,制备了多荧光发射的光纤涂层材料,可控构筑了多组分荧光检测剂掺杂凝胶涂层。利用荧光光谱结合色度图分析,确定检测物与色坐标的关系,实现了多检测物的多通道荧光响应,为实现多荧光光纤传感器的可控构筑提供了有益的借鉴和指导意义。     

Optical sensors for determining phenolic compounds with different structures

The literature data published in 1993–2012 on the development and application of optical sensors for the determination of phenolic compounds of various structures are summarized. The design, analytical characteristics, and advantages and disadvantages of the existing optical sensors are reviewed, and some examples of using optical sensors in the analysis of real samples, including those from field experiments, are considered in detail.     

Multi-Analyte Sensing: From Site-Selective Deposition to Randomly-Ordered Addressable Optical Fiber Sensors

In this report we review the progress in the development of imaging fiber chemical sensors. Emphasis is placed on the chemical sensor component and the fabrication of architectures appropriate for multi-analyte sensing, such as optical fiber sensors. Two main approaches in the fabrication of such sensors will be highlighted: first, sensors made with spatially-resolved sensing sites by site-selective polymerization, second, sensors prepared by random distribution of microsphere sensors on an optical imaging fiber containing thousands of μm-scale wells. Examples of each are given.     

Optical sensors and biosensors based on sol-gel films

The sol-gel technology is being increasingly used for the development of optical sensors and biosensors, due to its simplicity and versatility. By this process, porous thin films incorporating different chemical and biochemical sensing agents are easily obtained at room temperature, allowing final structures with mechanical and thermal stability as well as good optical characteristics. In this article, an overview of the state-of-the-art of sol-gel thin films-based optical sensors is presented. Applications reviewed include sensors for determination of pH, gases, ionic species and solvents, as well as biosensors.     

Recent progress in fluorescent and colorimetric sensors for the detection of ions and biomolecules

Optical sensors are widely used in the field of analytical sensing and optical imaging because of their high sensitivity, fast response time, and technical simplicity. This review focuses on recent contributions concerning the ions, neutral molecules and especially tumor micro-environment-related parameters based fluorescent or colorimetric sensors and is organized according to their target classifications.     

Biological and chemical sensors based on graphene materials

Owing to their extraordinary electrical, chemical, optical, mechanical and structural properties, graphene and its derivatives have stimulated exploding interests in their sensor applications ever since the first isolation of free-standing graphene sheets in year 2004. This article critically and comprehensively reviews the emerging graphene-based electrochemical sensors, electronic sensors, optical sensors, and nanopore sensors for biological or chemical detection. We emphasize on the underlying detection (or signal transduction) mechanisms, the unique roles and advantages of the used graphene materials. Properties and preparations of different graphene materials, their functionalizations are also comparatively discussed in view of sensor development. Finally, the perspective and current challenges of graphene sensors are outlined (312 references).     

High effective sensors based on photonic crystals

Photonic crystals have been extensively studied as high effective sensors for environmental monitoring and chemical and biological detections. This paper reviews recent achievements on photonic crystal sensors. Especially, the band gap responsiveness and the ability in amplifying spontaneous emission are demonstrated in the reported photonic crystal monitors/sensors. They are of great importance for optical monitors/sensors visualized by the naked eye and sensors based on fluorescence applications. The photonic crystal sensors are promising for low-cost and high effective sensors and detection methods, although challenges still exist in practical applications.     

Intrinsic Artefacts in Optical Oxygen Sensors—How Reliable are our Measurements?

Optical oxygen sensing is of broad interest in many areas of research, such as medicine, food processing, and micro‐ and marine biology. The operation principle of optical oxygen sensors is well established and these sensors are routinely employed in lab and field experiments. Ultratrace oxygen sensors, which enable measurements in the sub‐nanomolar region (dissolved oxygen), are becoming increasingly important. Such sensors prominently exhibit phenomena that complicate calibration and measurements. However, these phenomena are not constrained to ultratrace sensors; rather, these effects are inherent to the way optical oxygen sensors work and may influence any optical oxygen measurement when certain conditions are met. This scenario is especially true for applications that deal with high‐excitation light intensities, such as microscopy and microfluidic applications. Herein, we present various effects that we could observe in our studies with ultratrace oxygen sensors and discuss the reasons for their appearance, the mechanism by which they influence measurements, and how to best reduce their impact. The phenomena discussed are oxygen photoconsumption in the sensor material; depletion of the dye ground state by high‐excitation photon‐flux values, which can compromise both intensity and ratiometric‐based measurements; triplet–triplet annihilation; and singlet‐oxygen accumulation, which affects measurements at very low oxygen concentrations.     

Principles and applications of electrochemical and optical biosensors

The principles of biocatalytic and bioaffinity biosensors are reviewed with emphasis on electron transfer-type enzyme sensors, optical enzyme sensors and optical immunosensors for homogeneous immunoassay. An enzyme sensor for ethanol was fabricated by electrochemical polymerization of pyrrole onto the surface of platinized platinum-adsorbed alcohol dehydrogenase—NAD—Meldola Blue. Ethanol was determined amperometrically by measuring the oxidative current through polypyrrole. An optical enzyme sensor is exemplified by an acethylcholine sensor based on an optical pH fibre sensor using a thin polyaniline film. The optical immunosensor for homogeneous immunoassay consists of an optical fibre, the end of the which is coated with an optically transparent platinum electrode. With using luminol as a label, highly sensitive homogeneous immunoassay is carried out by measuring the electrochemical luminescence of the label.     

Humidity sensing characteristics of Sn doped Zinc oxide based quartz crystal microbalance sensors

The electrical, optical and humidity sensor properties of nanostructured ZnO samples were investigated. The structural properties of Sn doped ZnO samples were characterized by X-ray diffraction and atomic force microscopy. It was found that the all samples have a hexagonal crystal structure. The electrical conductivity of the samples indicates that undoped and Sn doped ZnO samples exhibit the semiconducting behavior. The optical absorption method was used to determine the optical band gaps of the samples. The optical band gap and activation energy values of the ZnO samples were changed with Sn doping. The ZnO based on quartz crystal microbalance humidity sensors were prepared and sensing properties of the sensors were changed with Sn doping. The response time required to reach 70 % is about 13–16 s, while the recovery time from 70 to 30 % RH is about 13–15 s. The fast response of the sensors is due to easy diffusion of water molecules between ZnO nanopowders. The prepared sensors have a high reproducibility and sensitivity for humidity sensing applications.     

光控二芳烯化学传感器及其研究进展

有机光致变色材料由于在光学记忆及分子开关器件等领域具有潜在的应用价值而备受关注。在众多有机光致变色系统中,二芳烯类光致变色化合物具有热稳定性好、耐疲劳、响应速度快和灵敏度高等优点,在光电材料和生物医学领域具有广阔的应用前景。近年来,围绕二芳烯构建可调控光化学传感器已成为功能材料领域的一大研究热点。本文主要介绍以二芳烯作为光调控单元合成具有多重调控功能的化学传感器的研究进展,并展望了该领域的应用前景和研究方向。     

Application of MXene in Electrochemical Sensors: A Review

Electroanalysis has obtained considerable progress over the past few years, especially in the field of electrochemical sensors. Broadly speaking, electrochemical sensors include not only conventional electrochemical biosensors or non-biosensors, but also emerging electrochemiluminescence (ECL) sensors and photoelectrochemical (PEC) sensors which are both combined with optical methods. In addition, various electrochemical sensing devices have been developed for practical purposes, such as multiplexed simultaneous detection of disease-related biomarkers and non-invasive body fluid monitoring. For the further performance improvement of electrochemical sensors, material is crucial. Recent years, a kind of two-dimensional (2D) nanomaterial MXene containing transition metal carbides, nitrides and carbonitrides, with unique structural, mechanical, electronic, optical, and thermal properties, have attracted a lot of attention form analytical chemists, and widely applied in electrochemical sensors. Here, we reviewed electrochemical sensors based on MXene from Nov. 2014 (when the first work about electrochemical sensor based on MXene published) to Mar. 2021, dividing them into different types as electrochemical biosensors, electrochemical non-biosensors, electrochemiluminescence sensors, photoelectrochemical sensors and flexible sensors. We believe this review will be of help to those who want to design or develop electrochemical sensors based on MXene, hoping new inspirations could be sparked.     

光学薄膜氧气传感器研究进展

光学薄膜氧气传感器具有检测精度高、选择性好、抗干扰能力强等优点,近年来日益得到人们的广泛重视,研究工作也在不断深化和拓展,展现出十分广阔的应用前景。本文按光学薄膜氧气传感器的制备方法分类扼要综述了光学薄膜氧气传感器的研究现状,并展望了其研究前景。     

Electrochemical plasmonic sensors

The enormous progress of nanotechnology during the last decade has made it possible to fabricate a great variety of nanostructures. On the nanoscale, metals exhibit special electrical and optical properties, which can be utilized for novel applications. In particular, plasmonic sensors including both the established technique of surface plasmon resonance and more recent nanoplasmonic sensors, have recently attracted much attention. However, some of the simplest and most successful sensors, such as the glucose biosensor, are based on electrical readout. In this review we describe the implementation of electrochemistry with plasmonic nanostructures for combined electrical and optical signal transduction. We highlight results from different types of metallic nanostructures such as nanoparticles, nanowires, nanoholes or simply films of nanoscale thickness. We briefly give an overview of their optical properties and discuss implementation of electrochemical methods. In particular, we review studies on how electrochemical potentials influence the plasmon resonances in different nanostructures, as this type of fundamental understanding is necessary for successful combination of the methods. Although several combined platforms exist, many are not yet in use as sensors partly because of the complicated effects from electrochemical potentials on plasmon resonances. Yet, there are clearly promising aspects of these sensor combinations and we conclude this review by discussing the advantages of synchronized electrical and optical readout, illustrating the versatility of these technologies.     

Oxygen indicators and intelligent inks for packaging food

The detection of oxygen using optical sensors is of increasing interest, especially in modified atmosphere food packaging (MAP), in which the package, usually containing food, is flushed with a gas, such as carbon dioxide or nitrogen. This tutorial review examines the ideal properties of an oxygen optical sensor for MAP and compares them with those developed to date, including the most recent advances. The basic technologies underpinning the different indicator types are described, examples given and their potential for application in MAP assessed. This tutorial review should be of interest to the MAP industry and researchers in optical sensors and oxygen sensing.     

Humidity-sensing inverse opal hydrogels

Soft material hydrogel sensors have seen increased interest recently. Most of these sensors are used in an aqueous environment. In this study, we depart from this trend and analyze the ability of a periodic hydrogel structure to respond to variations in ambient humidity through an optical change. First, a polyacrylamide inverse opal hydrogel structure was created from a colloidal crystal template. Next, this material was tested under various humidity conditions and responded to these changes by shifting its optical reflection peak noticeably within the visible wavelength range. This effect opens the doors for these materials as humidity sensors. The kinetics of the peak shifts was also observed, showing a rapid response to ambient humidity changes. Finally, the structural dimension change is compared through peak shifts, Fabry-Perot fringes of the optical cavity, and scanning electron microscopy observations.     

Optical waveguide sensors in analytical chemistry: today’s instrumentation, applications and trends for future development

Current concepts for chemical and biochemical sensing based on detection with optical waveguides are reviewed. The goals are to provide a framework for classifying such sensors and to assist a designer in selecting the most suitable detection techniques and waveguide arrangements. Sensor designs are categorized on the basis of the five parameters that completely describe a light wave: its amplitude, wavelength, phase, polarization state and time-dependent waveform. In the fabrication of a successful sensor, the physical or chemical property of the determined species and the particular light wave parameter to detect it should be selected with care since they jointly dictate the sensitivity, stability, selectivity and accuracy of the eventual measurement. The principle of operation, the nature or the detected optical signal, instrumental requirements for practical applications, and associated problems are analyzed for each category of sensors. Two sorts of sensors are considered: those based on direct spectroscopic detection of the analyte, and those in which the analyte is determined indirectly through use of an analyte-sensitive reagent. Key areas of recent study, useful practical applications, and trends in future development of optical waveguide chemical and biochemical sensors are considered.     

Silica-based optical chemosensors for detection and removal of metal ions

Because some metal ions are highly toxic even at trace level, a constant demand of developing methods for monitoring and removing these metal ions is extremely urgent. Silica-based optical chemosensors are supposed as good alternatives to classical instrumental methods for detecting and adsorbing metal ions, due to their effect and lower price. Silica nanoparticles, silica gel and mesoporous silica are used as supporting platforms to fabricate optical chemosensors. They have certain properties containing high porosity and expectant adsorption capacity. Chromogenic-type and fluorogenic-type optical probes, such as azobenzene, naphthalimide and rhodamine, are grafted to the surface of silica-based materials by sol–gel reaction, the limit of detection, response time and selective properties of optical sensors are improved sequentially. In this paper, the articles of silica-based optical chemosensors are retrospected since 2008, describing silica-based optical sensors used for sensing metal ions. The sensing mechanism, optical phenomenon, detection limit, adsorption capacity and application are also reviewed.