Electrochemical sensors and biosensors based on redox polymer/carbon nanotube modified electrodes: A review

The aim of this review is to present the contributions to the development of electrochemical sensors and biosensors based on polyphenazine or polytriphenylmethane redox polymers together with carbon nanotubes (CNT) during recent years. Phenazine polymers have been widely used in analytical applications due to their inherent charge transport properties and electrocatalytic effects. At the same time, since the first report on a CNT-based sensor, their application in the electroanalytical chemistry field has demonstrated that the unique structure and properties of CNT are ideal for the design of electrochemical (bio)sensors. We describe here that the specific combination of phenazine/triphenylmethane polymers with CNT leads to an improved performance of the resulting sensing devices, because of their complementary electrical, electrochemical and mechanical properties, and also due to synergistic effects. The preparation of polymer/CNT modified electrodes will be presented together with their electrochemical and surface characterization, with emphasis on the contribution of each component on the overall properties of the modified electrodes. Their importance in analytical chemistry is demonstrated by the numerous applications based on polymer/CNT-driven electrocatalytic effects, and their analytical performance as (bio) sensors is discussed.     

Harnessing host–guest chemistry for electrochemical sensing in complex matrices

Amid increasing demands for modernizing cumbersome and laboratory-bound analytical approaches, researchers are developing generalizable electrochemical sensing alternatives for point-of-need applications that are analogous to the glucometer. For this, integrating host–guest chemistry in electrochemical sensors represents an increasingly attractive strategy due to the vast library of host molecules and the ease with which they could be substituted for measuring different guest molecules. In response, we briefly explore the different signal transduction mechanisms (i.e., non-faradaic and faradaic) that enable electrochemical host–guest sensing. We describe the various advantages and shortcomings of the different approaches with hopes that this review will stimulate innovation toward the development of commercialized electrochemical devices relying on host–guest chemistry amenable at the point-of-need.     

Layer double hydroxides (LDHs)- based electrochemical and optical sensing assessments for quantification and identification of heavy metals in water and environment samples: A review of status and prospects

One of the most severe environmental problems is heavy metal contamination, putting the world's sustainability at risk. Much effort has been put into developing sensors that can be taken anywhere to detect the environmental effects of heavy metals. Sensitivity, selectivity, multiplexed detection ability, and mobility enhance significantly when nanoparticles and nanostructures are incorporated into sensors. LDHs (layered double hydroxides) have gotten much attention in analytical chemistry in recent years because of their benefits, including their large specific surface area, ease of synthesis, low cost, and high catalytic efficiency and biocompatibility. LDHs are often manufactured as nanomaterial composites or created with specialized three-dimensional structures depending on the application. However, in these settings, LDHs (as color indicators, extracting sorbents, and electrochemical sensing) are usually restricted. Upcoming signs of progress and development possibilities of LDHs in analytical chemistry are reviewed in this paper to assist overcome these problems. Furthermore, the approaches used in the design of LDHs, including structural aspects, are defined and assessed in preparation for future analytical applications. The latest advances in optical and electrochemical sensors to detect heavy metals are described in this review. The sorts and characteristics of LDHs will be explored first. We will then go into microelectrode (or nanoelectrode) arrays, nanoparticle-modified electrodes, and microfluidic optical and electrochemical sensing assays in detail. This paper also discusses design strategies for LDH-based nanostructured sensors and the advantages of using nanomaterials and nanostructures.     

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.     

柔性电子学中的表界面化学

柔性电子作为新兴的研究热点, 涉及材料、 化学、 物理等多个基础学科的交叉, 以及在生物医用、 可穿戴设备及人工智能等多个领域的应用. 柔性电子设备的制造加工过程中会用到弹性基底、 导电层、 功能层等多种性质各异的材料, 其互相之间的整合受到它们表面性质和界面结合力的限制; 器件的功能、 可靠性、 对环境的敏感性等也受到了器件表界面性质的影响; 因此, 对材料和器件表界面的处理在柔性电子学中具有重要作用. 本文对柔性电子学中常用的表界面化学过程分为3大类进行介绍: 表面电化学过程, 基于特定化合物反应产生的电流制备电化学传感器, 利用电流/电压控制表面负载化合物; 表面修饰, 通过表面改性提高材料的加工性能, 共价修饰分子层或其它材料赋予器件特殊功能性质或保护层; 不同材料之间的界面连接, 通过共价连接或化学反应辅助的物理交联实现不同材料的结合, 提高柔性器件的稳定性, 实现柔性设备的整合. 对各应用进行总结和举例后, 讨论了存在的问题, 并对未来的发展方向及前景进行了展望.     

基于功能性纳米材料的新型电化学界面的构筑以及相关应用(英文)

由于独特的光、电、磁以及催化性质,功能性纳米材料的研究已经渗透到各个学科并在不同领域展示出潜在的应用前景,尤其是利用纳米材料构建功能性电极界面、研究其电化学行为并发展新颖的电化学纳米器件引起了了人们的广泛关注. 本篇综述中,主要介绍作者研究小组在以功能性纳米材料构建新颖的电化学界面的最新进展,集中关注其在电化学传感器、燃料电池以及光谱电化学中的应用. 这些纳米材料的应用极大地增强了电子转移、提高了电化学传感器的灵敏度以及燃料电池的催化效率. 作者也通过合成一些光谱匹配的荧光以及电致变色纳米材料构建新颖的荧光光谱电化学器件,同时在材料的合成组装、多重刺激响应体系以及多功能化进行探索. 最后,作者对这类基于纳米材料的电化学器件的发展和应用予以展望.     

A mini-review on MXenes as versatile substrate for advanced sensors

MXenes have emerged as versatile 2D materials that are already gaining paramount attention in the areas of energy,catalyst,electromagnetic shielding,and sensors.The unique surface chemistry,graphene-like mo rphology,high hydrophilicity,metal-like conductivity with redox capability identifies MXenes,as an ideal material for surface-related applications.This short review summarizes the most recent reports that discuss the potential application of MXenes and their hybrids as a transducer material for advanced sensors.Based on the nature of transducing signals,the discussion is categorized into three sections,which include electrochemical(bio) sensors,gas sensors,and finally,electro-chemiluminescence fluorescent sensors.The review provides a concise summary of all the analytical merits obtained subsequent to the use of MXenes,followed by endeavors that have been made to accentuate the future perspective of MXenes in sensor devices.     

A review of opportunities for electrospun nanofibers in analytical chemistry

Challenges associated with analyte and matrix complexities and the ever increasing pressure from all sectors of industry for alternative analytical devices, have necessitated the development and application of new materials in analytical chemistry. To date, nanomaterials have emerged as having excellent properties for analytical chemistry applications mainly due to their large surface area to volume ratio and the availability of a wide variety of chemical and morphological modification methods. Of the available nanofibrous material fabrication methods, electrospinning has emerged as the most versatile. It is the aim of this contribution to highlight some of the recent developments that harness the great potential shown by electrospun nanofibers for application in analytical chemistry. The review discusses the use of electrospun nanofibers as a platform for low resolution separation or as a chromatographic sorbent bed for high resolution separation. It concludes by discussing the applications of electrospun nanofibers in detection systems with a specific focus on the development of simple electrospun nanofiber based colorimetric probes.     

石墨相碳化氮(g-C3N4)纳米材料在分析化学中的应用进展

石墨相碳化氮(g-C_3N_4)具有类似于石墨烯的片层结构,其独特的电子能带结构、热稳定性以及高化学稳定性,优异的光学、电学性质,使之在生物成像、光、电传感器方面具有广阔的应用前景。该文综述了g-C_3N_4纳米材料在电化学、光学分析等分离分析方面的应用进展,并展望了其发展前景。     

Advances in nucleic acid architectures for electrochemical sensing

Nucleic acid–based electrochemical sensors are ideally suited to the detection of molecular targets for which enzymatic detection or direct electrochemical oxidation – reduction reactions are not possible. Moreover, the versatility of nucleic acids in their ability to bind a great variety of target types, from small molecules to single-entity mesoscopic targets, makes them attractive receptors for the development of electrochemical biosensors. In this brief opinion piece, we discuss field advances from the past two years. We hope the works highlighted here will inspire the community to pursue creative designs enabling the detection of larger and more complex targets with a specific focus on analytical validation and translation into preclinical or clinical applications.     

柔性印刷可穿戴电化学传感器

实现对人体的健康监测和慢性病监测是包括材料科学、信息技术、电子技术、分析化学等科学领域在内的世界前沿课题。通过连续获取温度、压力、应力等物理信号来实现对人体活动情况和心率、血压、脑电图、心电图等实时监测的可穿戴设备已实现商业化,但连续监测人体体液、呼出气中的各类化学物质的可穿戴传感器仍面临许多问题,比如传感器的柔韧性、灵敏度、准确性以及与人体皮肤的贴合性等。针对这些问题,本文以柔性印刷技术为出发点,综述了各类柔性基底在电化学传感器/生物传感器领域的应用,同时对可穿戴传感器的发展方向提出了建议。     

Miniaturized electrochemical sensors and their point-of-care applications

Most of the current analytical methods depend largely on laboratory-based analytical techniques that require expensive and bullky equipment,potentially incur costly testing,and involve lengthy detection processes.With increasing requirements for point-of-care testing(POCT),more attention has been paid to miniaturized analytical devices.Miniaturized electrochemical(MEC)sensors,including different material-based MEC sensors(such as DNA-,paper-,and screen electrode-based),have been in strong demand in analytical science due to their easy operation,portability,high sensitivity,as well as their short analysis time.They have been applied for the detection of trace amounts of target through measuring changes in electrochemical signal,such as current,voltage,potential,or impedance,due to the oxidation/reduction of chemical/biological molecules with the help of electrodes and electrochemical units.MEC sensors present great potential for the detection of targets including small organic molecules,metal ions,and biomolecules.In recent years,MEC sensors have been broadly applied to POCT in various fields,including health care,food safety,and environmental monitoring,owing to the excellent advantages of electrochemical(EC)technologies.This review summarized the state-of-the-art advancements on various types of MEC sensors and their applications in POCT.Furthermore,the future perspectives,opportunities,and challenges in this field are also discussed.     

Recent advances in graphite powder-based electrodes

Graphite powder-based electrodes have the electrochemical performance of quasi-noble metal electrodes with intrinsic advantages related to the possibility of modification to enhance selectivity and their easily renewable surface, with no need for hazardous acids or bases for their cleaning. In contrast with commercial electrodes, for example screen-printed or sputtered-chip electrodes, graphite powder-based electrodes can also be fabricated in any laboratory with the form and characteristics desired. They are also readily modified with advanced materials, with relatively high reproducibility. All these characteristics make them a very interesting option for obtaining a large variety of electrodes to resolve different kinds of analytical problems. This review summarizes the state-of-the-art, advantages, and disadvantages of graphite powder-based electrodes in electrochemical analysis in the 21st century. It includes recent trends in carbon paste electrodes, devoting special attention to the use of emergent materials as new binders and to the development of other composite electrodes. The most recent advances in the use of graphite powder-modified sol–gel electrodes are also described. The development of sonogel–carbon electrodes and their use in electrochemical sensors and biosensors is included. These materials extend the possibilities of applications, especially for industrial technology-transfer purposes, and their development could affect not only electroanalytical green chemistry but other interesting areas also, for example catalysis and energy conversion and storage.     

Versatile Metalloporphyrin-Based Electrochemical Sensing Applications: From Small Gasotransmitters to Macromolecules

At the beginning of his youthful sixth decade, this work is dedicated to Prof. Dr. Fabio Doctorovich. He is distinctive in organometallic chemistry. During his successful career, he has been studying the reactivity and application of metalloporphyrins. Metalloporphyrins are organometallic complexes that exhibit, through synthetic modifications, the ability to tune their optical and electrochemical properties and their selectivity towards a particular molecule or ion. For this reason, they are systems extremely useful as electrochemical sensors to detect and quantify a wide variety of analytes with high selectivity, even in real samples such as food, water, biological fluids, or pharmaceutical compounds. This review presents an up-to-date list of reports in which metalloporphyrins are used as electrochemical sensors. In addition to compiling a comprehensive and up-to-date list of reported sensors that utilize metalloporphyrins, this work aims to provide an overview of currently available tools and techniques for the detection of various chemical species through similar approaches, which are constantly being developed.     

Synthetic membranes (vesicles) in inorganic ion analysis: a review

Vesicles are structures of amphiphile molecules occurring through a self-aggregation process at the molecular or nano scale level with a large structural variety and diverse properties providing a reaction environment for chemical reactions that resembles that of natural systems. Their high versatility and recognized utility in various applications have triggered a interdisciplinary scientific endeavor over their formation, characterization and potential applications with impressive results. However, in the vastness of applications surrounding vesicular structures, their utility in analytical chemistry has only received minor attention. Notwithstanding, studies demonstrating their potential as colorimetric or fluorescence sensors, extraction solvents of inorganic ions or their chelates and stationary phase modifiers in liquid chromatography have appeared. To this end, this article aims to present for the first time the analytical chemistry aspects behind the use of vesicle media with special emphasis on the detection and determination of inorganic ions and encourage further research on this promising field of analytical science.     

Selective Electrochemical Detection of Explosives with Nanomaterial Based Electrodes

Explosive detection technologies play a critical role in maintaining national security, remain an active research field with many devices and analytical/electroanalytical techniques. Analytical chemistry needs for homeland defense against terrorism make it clear that real-time and on-site detection of explosives and chemical warfare agents (CWAs) are in urgent demand. Thus, current detection techniques for explosives have to be improved in terms of sensitivity and selectivity, opening the way to electrochemical devices suitable to obtain the targeted analytical information in a simpler, cheaper and faster way. For the electrochemical determination of energetic substances, a large number of sensor electrodes have been presented in literature using different modification materials, especially displaying higher selectivity with molecularly imprinted polymers (MIPs). MIPs have already been utilized for the detection of hazardous materials due to their mechanical strength, flexibility, long-time storage and low cost. The sensitivity of MIP-based electrosensors can be enhanced by coupling with nanomaterials such as graphene oxide (GOx), carbon nanotubes (CNTs), or nanoparticles (NPs). Specific characteristics of involved nanomaterials, their modification, detection mechanism, and other analytical aspects are discussed in detail. Non-MIP electrosensors are generally functionalized with materials capable of charge transfer, H-bonding or electrostatic interactions with analytes for pre-concentration and electrocatalysis on their surface, whereas nanobio-electrosensors use analyte-selective aptamers having specific sequences of DNA, peptides or proteins to change the potential or current. This review intends to provide a combination of information related to MIPs and nanomaterial-based electrochemical sensors, limited to the most significant and illustrative work recently published.     

Sensing approaches on paper-based devices: a review

Paper has been present in the world of analytical chemistry for centuries, but it seems that just a few years back it was rediscovered as a valuable substrate for sensors. We can easily list some of the countless advantages of this simple cellulosic substrate, including mechanical properties, three-dimensional fibrous structure, biocompatibility and biodegradability, easiness of production and modification, reasonable price, and availability all over the world. Those characteristics make paper a first-choice substrate for disposable sensors and integrated sensing platforms. Nowadays, numerous examples of paper-based sensors are being presented in the literature. This review describes some of the most prominent examples classifying them by type of detection: optical (colorimetric, fluorescence, surface-enhanced Raman spectroscopy, and transmittance methods) and electrochemical (voltammetric, potentiometric, and conductivity-based methods). We take a closer look at recent advances in immunoassays fabricated on paper, excluding simple lateral flow tests assembled on nitrocellulose. This review also summarizes the main advantages and disadvantages of the use of paper as a substrate for sensors, as well as its impact on their performance and application, presents a short history of paper in analytical chemistry, and discusses fabrication methods and available sources of paper.     

Recent progress in the design of G-quadruplex–based electrochemical aptasensors

Aptamer-based electrochemical sensors are now developed for the detection of a wide variety of analytes including ions, low-molecular-weight molecules, proteins, and living cells. An aptamer-based sensor is an analytical device whose bio-sensing element (i.e. the aptamer) is immobilized on a transducer surface. Aptasensors have attracted great attention because of their high selectivity, sensitivity, and stability; they could be miniaturized and are of low production cost and offer extraordinary flexibility in the design of their assemblies. This review will emphasize recent developments of aptasensors using aptamers that are able to adopt the particular G-quadruplex (G4) conformations, which are secondary DNA structures formed from guanine-rich sequences. Indeed, G4 exhibits notable recognition properties inherent to their particular structuration.     

Targeting Chemical and Biological Warfare Agents at the Molecular Level

After the September 11 tragedies of 2001, scientists and law‐enforcement agencies have shown increasing concern that terrorist organizations and their “rogue” foreign government‐backers may resort to the use of chemical and/or biological agents against U.S. military or civilian targets. In addition to the right mix of policies, including security measures, intelligence gathering and training for medical personnel on how to recognize symptoms of biochemical warfare agents, the major success in combating terrorism lies in how best to respond to an attack using reliable analytical sensors. The public and regulatory agencies expect sensing methodologies and devices for homeland security to be very reliable. Quality data can only be generated by using analytical sensors that are validated and proven to be under strict design criteria, development and manufacturing controls. Electrochemical devices are ideally suited for obtaining the desired analytical information in a faster, simpler, and cheaper manner compared to traditional (lab‐based) assays and hence for meeting the requirements of decentralized biodefense applications. This articler presents a review of the major trends in monitoring technologies for chemical and biological warfare (CBW) agents. It focuses on research and development of sensors (particularly electrochemical ones), discusses how advances in molecular recognition might be used to design new multimission networked sensors (MULNETS) for homeland security. Decision flow‐charts for choosing particular analytical techniques for CBW agents are presented. Finally, the paths to designing sensors to meet the needs of today's measurement criteria are analyzed.     

Recent applications of carbon-based nanomaterials in analytical chemistry: critical review

The objective of this review is to provide a broad overview of the advantages and limitations of carbon-based nanomaterials with respect to analytical chemistry. Aiming to illustrate the impact of nanomaterials on the development of novel analytical applications, developments reported in the 2005-2010 period have been included and divided into sample preparation, separation, and detection. Within each section, fullerenes, carbon nanotubes, graphene, and composite materials will be addressed specifically. Although only briefly discussed, included is a section highlighting nanomaterials with interesting catalytic properties that can be used in the design of future devices for analytical chemistry.