A novel screen-printed electrode array for rapid high-throughput detection

A novel multi-channel electrode array sensing device was fabricated by screen-printing techniques using 96-well plate as the template. To confirm its practical value, we developed a one-step preparation of multi-walled carbon nanotubes (MWCNTs) doped electrode array by an ink containing MWCNTs, which was applied to the simultaneous detection of a variety of biological samples and environmental pollutants. Results demonstrated that the designed sensing device could carry out the multiple measurements of different analytes at the same time, while MWCNTs enhanced the electrocatalytic activity of electrodes toward electroactive molecules. The required amount of each sample was only ～200 μL. Moreover, the excellent differential pulse voltammetric (DPV) response toward dopamine, hydroquinone and catechol was obtained and the detection limits was determined to be 0.337, 0.289 and 0.369 μM, respectively. Comparing it with the traditional screen-printed electrode (SPE), this sensing device possesses the advantages of high-throughput, fast electron transfer rate for electrodes, short-time analysis and low sample consumption.     

3D‐printed Metal Electrodes for Heavy Metals Detection by Anodic Stripping Voltammetry

Heavy metals, being one of the most toxic and hazardous pollutants in natural water, are of great public health concern. Much effort is still being devoted to the optimization of the electroanalytical methods and devices, particularly for the development of novel electrode materials in order to enhance selectivity and sensitivity for the analysis of heavy metals. The ability of 3D‐printing to fabricate objects with unique structures and functions enables infinite possibilities for the creation of custom‐made electrochemical devices. Here, stainless steel 3D‐printed electrodes (3D‐steel) have been tested for individual and simultaneous square wave anodic stripping analysis of Pb and Cd in aqueous solution. Electrodeposition methods have also been employed to modify the steel electrode surface by coating with a thin gold film (3D−Au) or a bismuth film (3D−Bi) to enhance the analytical performance. All 3D‐printed electrodes (3D‐steel, 3D−Au and 3D−Bi) have been tested against a conventionally employed glassy carbon electrode (GC) for comparison. The surface modified electrodes (3D−Au and 3D−Bi) outperformed the GC electrode demonstrating higher sensitivity over the studied concentration ranges of 50–300 and 50–500 ppb for Pb and Cd, respectively. Owing to the bismuth property of binary alloys formation with heavy metals, 3D−Bi electrode displayed well‐defined, reproducible signals with relatively low detection limits of 3.53 and 9.35 ppb for Pb and Cd, respectively. The voltammetric behaviour of 3D−Bi electrode in simultaneous detection of Pb and Cd, as well as in individual detection of Pb in tap water was also monitored. Overall, 3D‐printed electrodes exhibited promising qualities for further investigation on a more customizable electrode design.     

New innovations in ionic liquid–based miniaturised amperometric gas sensors

Gas detection is an essential part of everyday life; for some applications, using sensors for toxic and hazardous gases can literally mean the difference between life and death. In this minireview, recent progress in amperometric gas sensing using miniaturised electrodes and devices is described. The focus is on the use of nonvolatile room-temperature ionic liquids (RTILs) as electrolytes, which possess inherent advantages such as wide electrochemical windows, high thermal and chemical stability, intrinsic conductivity and good solvating properties. Various different gases, electrodes and RTILs have been investigated in the strive towards new materials for improved gas sensors. The most recent developments using porous membrane electrodes, planar devices (e.g. screen-printed, thin-film, microarray and interdigitated electrodes) and the modification of these surfaces for improved sensitivity are described. RTILs have great potential to be used as electrolytes in amperometric gas sensors, with improved lifespan of the sensor in hot/dry environments and allowing miniaturisation of devices. However, it is clear that more understanding of their long-term operation and utility in real environments (e.g. background air, varying temperatures and humidity levels) is needed before their realisation in successful commercial devices.     

Applications of nanoscale carbon-based materials in heavy metal sensing and detection

This article reviews applications of nanoscale carbon-based materials in heavy metal sensing and detection. These materials, including single-walled carbon nanotubes, multi-walled carbon nanotubes and carbon nanofibers among others, have unique and tunable properties enabling applications in various fields spanning from health, electronics and the environment sector. Specifically, we highlight the unique properties of these materials that enable their applications in the sorption and preconcentration of heavy metals ions prior to detection by spectroscopic, chromatographic and electrochemical techniques. We also discuss their distinct properties that enable them to be used as novel electrode materials in sensing and detection. The fabrication and modification of these electrodes is discussed in detail and their applications in various electrochemical techniques such as voltammetric stripping analysis, potentiometric stripping analysis, field effect transistor-based devices and electrical impedance are critically reviewed. Perspectives and futures trends in the use of these materials in heavy metal sensing and detection will also be highlighted.     

A brief review on miniaturized electrochemiluminescence devices: From fabrication to applications

Miniaturized electrochemiluminescence (ECL) systems are widely recognized as a highly detection, user-friendly, and turnkey strategy to develop point-of-care-testing devices. The ECL sensing approach provides numerous advantages over other methods, including high signal-to-noise ratio and measurement with minimal or no background signal. The ECL signal can be easily controlled by a small external potential while providing high sensitivity and decreased electrode fouling, resulting in the use of ECL-based miniaturized systems for detection and monitoring of different analytes, including DNA and bacteria. In this work, different types of miniaturized ECL systems with various fabrication techniques are reviewed and their application in point-of-care-testing is thoroughly discussed. Furthermore, such ECL platforms have been summarized based on the type of the ECL mechanism, electrodes, range of detection, and limit of detection. Finally, some of the upcoming technological interventions to make such a miniaturized ECL platform amenable for portable and on-field analysis have been discussed.     

Engineered cells as biosensing systems in biomedical analysis

Over the past two decades there have been great advances in biotechnology, including use of nucleic acids, proteins, and whole cells to develop a variety of molecular analytical tools for diagnostic, screening, and pharmaceutical applications. Through manipulation of bacterial plasmids and genomes, bacterial whole-cell sensing systems have been engineered that can serve as novel methods for analyte detection and characterization, and as more efficient and cost-effective alternatives to traditional analytical techniques. Bacterial cell-based sensing systems are typically sensitive, specific and selective, rapid, easy to use, low-cost, and amenable to multiplexing, high-throughput, and miniaturization for incorporation into portable devices. This critical review is intended to provide an overview of available bacterial whole-cell sensing systems for assessment of a variety of clinically relevant analytes. Specifically, we examine whole-cell sensing systems for detection of bacterial quorum sensing molecules, organic and inorganic toxic compounds, and drugs, and for screening of antibacterial compounds for identification of their mechanisms of action. Methods used in the design and development of whole-cell sensing systems are also reviewed.     

Recent advances in electrochemical detection in capillary electrophoresis

Recent advances in the design and application of electrochemical (EC) detection systems in capillary electrophoresis (CE) are reviewed, with the objective of providing the nonelectrochemist with a state-of-the-art picture of CEEC instrumentation and an overview of the principal analytes for which CEEC is best suited. The detection schemes considered here include those based both on amperometry and on potentiometry as both kinds of EC systems are being actively developed in CE and have the potential for broad application in analysis. Over the three-year period covered by this review, an important direction that CEEC has taken is the construction of more complex electrode systems beginning with the use of multiple EC electrodes and culminating with the adaptation of EC detection to microfabricated "lab-on-a-chip" analysis devices. In addition, CEEC applications have now grown to include a broad variety of inorganic, organic, and biochemical analytes and samples.     

Electroanalytical Approach for Quantification of Pesticide Maneb

For the first time, in this study electrochemical oxidation behavior of pesticide maneb is evaluated. Due to the structure electroanalytical quantification of maneb has not been exploited enough. Maneb electrochemical behavior was investigated using glassy carbon (GC), graphene modified glassy carbon (GR/GC) and boron doped diamond (BDD) electrodes. It is shown that only BDD shows satisfactory results toward maneb detection. Based on this, a simple, sensitive and selective electroanalytical method for determination of pesticide maneb using differential pulse voltammetry (DPV) is proposed, with a working linear range of 80–3000 nM and the limit of detection of 24 nM. The developed methodology has been applied for the determination of maneb in river water samples with satisfactory recovery. Additionally, this green method, being simple, fast, and free of chemical‐reduction reagents, offers several advantages over modified electrodes and expands the scope of BDD based electrochemical sensing devices, with promise for wider applications in environmental analysis.     

Selective detection in flow analysis based on the combination of immobilized enzymes and chemically modified electrodes

The combination of immobilized enzymes and amperometry to build selective detection devices in flow-injection analysis and liquid chromatography is described. The pros and cons of enzyme electrodes and of immobilized enzyme reactors are discussed. The paper concentrates on the use of immobilized dehydrogenases, oxidases, peroxidases, and on electrodes on which these enzyme reactions can be selectively followed. The work in the field by the authors is reviewed.     

Compared EC-AFM Analysis of Laser-Induced Graphene and Graphite Electrodes in Sulfuric Acid Electrolyte

Flexible and economic sensor devices are the focus of increasing interest for their potential and wide applications in medicine, food analysis, pollution, water quality, etc. In these areas, the possibility of using stable, reproducible, and pocket devices can simplify the acquisition of data. Among recent prototypes, sensors based on laser-induced graphene (LIGE) on Kapton represent a feasible choice. In particular, LIGE devices are also exploited as electrodes for sensing in liquids. Despite a characterization with electrochemical (EC) methods in the literature, a closer comparison with traditional graphite electrodes is still missing. In this study, we combine atomic force microscopy with an EC cell (EC-AFM) to study, in situ, electrode oxidation reactions when LIGE or other graphite samples are used as anodes inside an acid electrolyte. This investigation shows the quality and performance of the LIGE electrode with respect to other samples. Finally, an ex situ Raman spectroscopy analysis allows a detailed chemical analysis of the employed electrodes.     

革除或减少增塑剂的敏感膜离子选择电极

基于国内外最新研究工作,系统总结了离子选择电极膜中革除或减少外增塑剂的新膜基体,包括丙烯酸酯类聚合物、羟基功能化的乙烯基树脂、聚氨酯、硅橡胶以及导电聚合物,对其物理化学性能以及传感器检测等进行了全面归纳与讨论.指出该类革除外增塑剂的传感膜不仅避免了增塑剂的泄漏及其对生物样品的污染,而且较传统增塑聚氯乙烯(PVC)膜扩散系数降低了约3个数量级,有利于抑制过膜离子流,使其检测下限较传统增塑PVC下降了5个数量级,且选择系数也有不同程度的改善.另外,该类传感膜材料由于与固体支撑材料间优良的粘附性保证了电极的使用寿命,特别是在微型化固态电极中.以这类传感膜构建的电位型离子传感器将以其独特的优势在环境监测、食品卫生,尤其是在医疗诊断、生物物质检测中展示出不可替代的作用.     

Screen printed electrodes provide micro-domain sites for fabricating disposable electro-catalytic ensembles

We demonstrate that bespoke screen printed electrodes which are basal plane-like in nature can be used as a template to produce randomly dispersed electro-catalytic micro-domains for analytical sensing purposes. Proof-of-concept is shown for the case of copper ensembles for nitrate detection and palladium ensembles for hydrazine sensing. The advantageous disposable nature of the ensemble precludes the need of pre-treatment between measurements. The screen printed ensembles act as excellent substrates for the deposition of a range of metals allowing the screen printed electrodes to act as a template for micro-domain ensembles of many different electrode materials for a variety of analytical challenges.     

A highly sensitive aptasensor for on‐site detection of lipopolysaccharides in food

A rapid, low‐cost, highly sensitive, and specific capacitive aptasensor is presented for detection of lipopolysaccharides (LPS). Exposure to LPS could cause fever, gram‐negative sepsis, septic shock, and eventual death. Hence, rapid, low cost, and sensitive detection of LPS is pivotal for the safety of food, pharmaceutical, and medical devices and products. In this work, a capacitive sensing method based on alternating current electrokinetics is developed to achieve rapid and specific detection of LPS. This method uses an alternating current signal for two purposes. One is to induce positive dielectrophoresis, which attracts LPS toward the sensor electrodes’ surface and accelerates its binding with the immobilized aptamer probe. The other purpose is to simultaneously sense the binding reaction by measuring the interfacial capacitance change on the electrodes’ surface. The testing procedures and instrumentation setup of this sensing platform are significantly simplified while finding quantitative concentrations of both analytical and complex samples within 30 s. When testing analytical samples of LPS from Escherichia coli O55:B5, a LOD of 4.93 fg/mL is achieved. The recovery analysis is also performed with LPS spiked in a complex matrix and good recovery rates are demonstrated. This work provides an affordable and field‐deployable platform for highly sensitive and real‐time LPS detection.     

Podand and macrocyclic amine receptors with urea functionalities for potentiometric detection of organic acids in HPLC

Ten synthetic receptors were tested in potentiometric coated wire electrodes. The electrodes were used as sensing devices in classical reversed phase HPLC determinations of dicarboxylic acids present in food materials. All receptors contained amine functionalities. Four of them were podand urea derivatives. The other six were macrocyclic polyamines with lipophilic groups. Three of them had urea functionalities in their side-chains. Glassy carbon (GC) substrate electrodes were coated with PVC-based “liquid membranes” containing plasticizers and receptors. All tested compounds strongly enhanced the detection limits for the dicarboxylic acids (low pg detection limits), in comparison to a non-specific electrode based on methyltridodecylammonium chloride (MTDDACl). Receptors of the podand urea type yielded high sensitivity, but the electrodes had a lower long-time stability (a few weeks) than the electrodes based on macrocyclic polyamines (at least 3 months).     

Textile‐based Electrochemical Sensing: Effect of Fabric Substrate and Detection of Nitroaromatic Explosives

This study examines the influence of textile substrates upon the behavior of wearable screen‐printed electrodes and demonstrates the attractive sensing properties of these sensors towards the detection of nitroaromatic explosives. Compared to electrodes printed on common cotton or polyester substrates, GORE‐TEX‐based electrochemical sensors display reproducible background cyclic voltammograms, reflecting the excellent water‐repellant properties of the GORE‐TEX fabric. The wetting properties of different printed textile electrodes are elucidated using contact angle measurements. The influence of laundry washing and mechanical stress is explored. The GORE‐TEX‐based printed electrodes exhibit favorable detection of 2,4‐dinitrotoluene (DNT) and 2,4,6‐trinitrotoluene (TNT) explosives, including rapid detection of DNT vapor.     

Fabrication of solid‐state nanopores and its perspectives

Nanofluidics is becoming an extensively developing technique in the field of bioanalytical chemistry. Nanoscale hole embed in an insulating membrane is employed in a vast variety of sensing platforms and applications. Although, biological nanopores have several attractive characteristics, in this paper, we focused on the solid‐state nanopores due to their advantages as high stability, possibility of diameter control, and ease of surface functionalizing. A detection method, based on the translocation of analyzed molecules through nanochannels under applied voltage bias and resistive pulse sensing, is well established. Nevertheless, it seems that the new detection methods like measuring of transverse electron tunneling using nanogap electrodes or optical detection can offer significant additional advantages. The aim of this review is not to cite all related articles, but highlight the steps, which in our opinion, meant important progresses in solid‐state nanopore analysis.     

Electrochemistry on Paper‐based Analytical Devices: A Review

Even though they were introduced less than a decade ago, electrochemical paper‐based devices (ePADs) have attracted widespread attention because of their inherent advantages in many applications. ePADs combine the advantages of microfluidic paper‐based devices (low cost, ease of use, equipment free pumping, etc.) for sample handling and processing with the advantages of sensitive and selective detection provided by electrochemistry. As a result, ePADs provide simplicity, portability, reproducibility, low cost and high selectivity and sensitivity for analytical measurements in a variety of applications ranging from clinical diagnostics to environmental sensing. Herein, recent advances in ePAD development and application are reviewed, focusing on electrode fabrication techniques and examples of applications specially focused on environmental monitoring, biological applications and clinical assays. Finally, a summary and prospective directions for ePAD research are also provided.     

Ion-selective potentiometric sensors with silicone sensing membranes: A review

Ion-selective electrodes (ISEs) are used widely in mainframe analyzers for clinical chemistry, but there is also an increasing interest in the development of paper-based devices, wearable and implantable sensors, and other miniaturized ISEs. This trend is spurring much research in developing solid contact materials that enable miniaturization. The development of suitable polymeric matrixes for such sensors has only received less attention. In particular, in spite of lifetime limitations and toxicity concerns, polymeric matrixes comprising plasticizers are still commonly used. To that end, we note the benefits of silicone materials as alternative polymeric matrixes and, in particular, their promise for enhanced biocompatibility. While there has been steady progress in the development of ISEs with silicone membranes, this topic has not been reviewed for many years. This review critically discusses key fundamental characteristics of ISEs with silicone sensing and reference membranes, including their biocompatibility, adhesion to device substrates, water uptake, polarity, common impurities, and commercial availabilities. This is followed by a discussion of specific types of silicones and their use in ISEs, with the goal to inform and stimulate future research efforts into such devices.     

Polyion Detection via All‐solid‐contact Paper‐based Polyion‐sensitive Polymeric Membrane Electrodes

The first all‐solid‐contact paper‐based single‐use polyion‐sensitive ion‐selective electrodes (ISEs) are described. These polyion‐sensitive ISEs are fabricated using cellulose filter paper coated with a carbon ink conductive layer. A polyanion sensing membrane is cast on a section of the coated paper and the sensor is insulated, resulting in a disposable, single‐use device. Various polyanions are shown to yield large negative potentiometric responses when using these disposable devices for direct polyanion detection. These new sensors are further demonstrated to be useful in indirect polycation detection when polycations (i. e., polyquaterniums (PQs)) are titrated with polyanionic dextran sulfate (DS). Titrations monitored using these paper‐based, all‐solid‐contact devices yield endpoints proportional to the given PQ concentration present in the test sample.     

Microbe-based electrochemical sensing systems

The combination of micro-organisms with electrochemical sensors can result in new sensing systems with extended analytical capabilities. The most common approaches for this combination are microbial electrodes and microbiological assays which utilize electrochemical detection.