Inkjet printed Prussian blue films for hydrogen peroxide detection

An inkjet printing method is described to fabricate hydrogen peroxide (H(2)O(2)) sensors. Insoluble Prussian blue (PB) nanoparticles were dispersed in aqueous solvent, and were printed on screen printed carbon electrodes with a piezoelectric inkjet printer for H(2)O(2) detection. The electrochemical behavior of the printed sensors was studied by using cyclic voltammetry and chronoamperometry. The printed sensors showed great electrocatalytic activity toward H(2)O(2) and can be used for amperometric detection of H(2)O(2). The calibration curves for H(2)O(2) determination showed a linear range from 0.02 to 0.7 mM with a sensitivity of 164.82 μA M(-1) cm(-2) for the printed PB film. The results showed the feasibility of applying inkjet printing technology on surface modification; the results also provide an alternative way for manufacturing electrochemical sensors.     

Nickel oxide Nanoparticles/Carbon Nanotubes Nanocomposite for Non-enzymatic Determination of Hydrogen Peroxide

In this work, nickel oxide nanoparticles-modified multi-walled carbon nanotubes (CNTs) were prepared and used for H2O2 sensing application. Firstly, ex situ NiO nanoparticles (NPs) were prepared and further used to decorate polyethylenimine (PEI)-modified carboxylated CNTs. The obtained nanocomposite and its precursors were identified by using X-ray diffraction, thermal analysis, Raman spectroscopy and SEM and TEM images, N2 adsorption-desorption isotherms, and electrochemical techniques. The sensing properties of the NiO-modified nanocomposite toward H2O2 were studied by electrochemical techniques using glassy carbon electrodes (GCEs) as support material. After optimizing the sensor construction, the sensor sensitivity was about of 0.83±0.01 A M⁻¹ cm⁻² with a LOD of about 1.0 μM. In addition, it showed excellent anti-interference properties, reproducibility, and stability (over 4 months). Finally, such sensors were coupled to a flow injection device and the H2O2 concentration of some commercial antiseptic solutions were successfully obtained (with recovery ratios between 96.3–102.4 %).     

Gold nanoparticle-embedded porous graphene thin films fabricated via layer-by-layer self-assembly and subsequent thermal annealing for electrochemical sensing

A uniform three-dimensional (3D) gold nanoparticle (AuNP)-embedded porous graphene (AuEPG) thin film has been fabricated by electrostatic layer-by-layer assembly of AuNPs and graphene nanosheets functionalized with bovine serum albumin and subsequent thermal annealing in air at 340 °C for 2 h. Scanning electron microscopy (SEM) investigations for the AuEPG film indicate that an AuNP was embedded in every pore of the porous graphene film, something that was difficult to achieve with previously reported methods. The mechanism of formation of the AuEPG film was initially explored. Application of the AuEPG film in electrochemical sensing was further demonstrated by use of H(2)O(2) as a model analyte. The AuEPG film-modified electrode showed improved electrochemical performance in H(2)O(2) detection compared with nonporous graphene-AuNP composite film-modified electrodes, which is mainly attributed to the porous structure of the AuEPG film. This work opens up a new and facile way for direct preparation of metal or metal oxide nanoparticle-embedded porous graphene composite films, which will enable exciting opportunities in highly sensitive electrochemical sensors and other advanced applications based on graphene-metal composites.     

Glucose and choline on-line biosensors based on electropolymerized Meldola's blue

Electropolymerized film of Meldola's blue (MB) was prepared and demonstrated as electron shuttle between the immobilized horse peroxidase (HRP) and glassy carbon electrode (GCE) for sensing hydrogen peroxide (H(2)O(2)) produced by enzyme catalytical reactions. Electrochemical polymerization of Meldola's blue was carried out by cyclic voltammetry (CV) in a phosphate buffer solution (pH 7.00) in a potential window from -0.60 to +1.30 V. The pH of the electropolymerization solution was found to be closely related to the resulted polymeric MB and the best polymeric film was obtained in a pH 7.00 phosphate buffer. The polymeric MB was demonstrated to shuttle the electron transfer between the immobilized HRP and GCE and utilized as a mediator for HRP immobilized biosensor for biocatalytical reduction of H(2)O(2) at a potential of -0.30 V (versus AgCl/Ag). The H(2)O(2) sensing system was applied to construct glucose and choline on-line sensors by wiring H(2)O(2) produced by enzyme oxidase catalytical reaction. The possibility of these sensors as on-line detectors for on-line and continuous measurement was explored off-line. The operating potential, interference, and lifetime of these sensors were also examined.     

Gas sensors based on nanostructured materials

Gas detection is important for controlling industrial and vehicle emissions, household security and environmental monitoring. In recent decades many devices have been developed for detecting CO(2), CO, SO(2), O(2), O(3), H(2), Ar, N(2), NH(3), H(2)O and several organic vapours. However, the low selectivity or the high operation temperatures required when most gas sensors are used have prompted the study of new materials and the new properties that come about from using traditional materials in a nanostructured mode. In this paper, we have reviewed the main research studies that have been made of gas sensors that use nanomaterials. The main quality characteristics of these new sensing devices have enabled us to make a critical review of the possible advantages and drawbacks of these nanostructured material-based sensors.     

Significance of nanomaterials in electrochemical sensors for nitrate detection: A review

Nanomaterial-enabled electrochemical sensors are designed as an economical, efficient, and user-friendly analytical tool for on-site and routine nitrate analysis over a wide range of environmental samples. The remarkable advances and tunable attributes of nanomaterials have greatly improved the analytical performance of electrochemical nitrate sensors. In this review, a comprehensive elucidation of the recent advances in nanomaterial-based electrochemical nitrate sensors is presented. The review firstly provides a general introduction, followed by typical electrochemical sensing methods. The next two sections detail various nanomaterials, including graphene derivatives, carbon nanotubes/fibers, metal/bimetal/metal oxide nanoparticles, and conducting polymers for modifying electrodes in enzymatic and non-enzymatic electrochemical nitrate sensors. Finally, the perspectives and current challenges in achieving real-world applications of nanomaterial-based electrochemical nitrate sensors are outlined.     

Ultra Flexible Paper Based Electrochemical Sensors: Effect of Mechanical Contortion upon Electrochemical Performance

The influence of mechanical contortion upon the electrochemical performance of screen‐printed graphite paper‐based electroanalytical sensing platforms is evaluated and contrasted with traditionally employed polymeric based screen‐printed graphite sensors. Such a situation of implementation can be envisaged for the potential sensing of analytes on the skin where such sensors are based, for example in clothing where mechanical contortion, viz, bending will occur, and as such, its effect upon electrochemical sensors is of both fundamental and applied importance. The effect of mechanical contortion or stress upon electrochemical behaviour and performance is of screen printed sensors is explored. Comparisons are made between both paper‐ and polymeric‐ based sensing platforms that are evaluated towards the sensing of the well characterised electrochemical probes potassium ferrocyanide(II), hexaammine‐ruthenium(III) chloride and nicotinamide adenine dinucleotide (NADH). It is determined that the paper‐based sensors offer greater resilience in terms of electrochemical performance after mechanical stress. We gain insights into the role played by both the effect of the time of mechanical contortion and additionally the potentially detrimental effects of repeated contortion are explored. These unique paper‐based sensors hold promise for widespread applications where flexible and ultra‐low cost sensors are required such as applications into medical devices were ultra‐low cost sensors are a pre‐requisite, but also for utilisation within applications which require the implementation of ultra‐flexible electroanalytical sensing platforms such as in the case of wearable sensors, whilst maintaining useful electrochemical performances.     

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.     

Controllable deposition of a platinum nanoparticle ensemble on a polyaniline/graphene hybrid as a novel electrode material for electrochemical sensing

We demonstrate for the first time an interfacial polymerization method for the synthesis of high-quality polyaniline-modified graphene nanosheets (PANI/GNs), which represents a novel type of graphene/polymer heterostructure. The interfacial polymerization at a liquid-liquid interface allows PANI to grow uniformly on the surface of the GNs. An ultra-high loading of Pt nanoparticles was then controllably deposited on the surface of the PANI/GNs to form a Pt/PANI/GNs hybrid. The obtained composites were characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The Pt/PANI/GNs hybrid shows excellent electrocatalytic activity toward methanol oxidation and oxygen reduction. H(2)O(2) and glucose were used as two representative analytes to demonstrate the sensing performance of a Pt/PANI/GNs-modified electrode. It is found that this sensing element shows high sensitivity and a low detection limit for H(2)O(2) and glucose. The results demonstrate that the Pt/PANI/GNs hybrid may be an attractive and advanced electrode material with potential applications in the construction of electrochemical sensors and biosensors.     

Nickel-Palladium Nanoparticles for Nonenzymatic Methanol Detection

Silicon microchannel plates (MCP) modified by nickel-palladium nanoparticles (Ni-Pd/Si-MCP) have highly ordered microchannels with uniform diameters and lengths isolated and parallel to one another and are excellent sensors for the determination of methanol in alkaline solutions. The 3D ordered Si MCP is fabricated by electrochemical etching used as the backbone, and the Ni-Pd nanoparticles are sensitive materials for detecting methanol that was obtained by an electroless plating method. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and electrochemical methods were employed to characterize the Ni-Pd/Si-MCP structure. An electrochemical workstation was used to monitor the sensing characteristics of the Ni-Pd/Si-MCP electrode. As a result of the synergetic effects rendered by the MCP and Ni-Pd nanoparticles, these sensors present a high sensitivity of 0.168 mA mM^?1, and the detection limits was 12 μM. In particular, since the fabrication process is compatible with conventional silicon technology, the structure has immense potential as an efficient, nonenzymatic, and integrated methanol sensors.     

电催化合成过氧化氢用于环境消毒

流行性疾病贯穿整个人类历史,伴随全球人口流动,它们可能演变成大型流行病.时至今日,我们仍在见证已知和新生的病原体对人类历史格局的改变.在与流行性疾病的抗争中,诸如紫外线辐射、巴氏杀菌和化学氧化法等技术被用于病原体的消杀和抗体的研制.然而,这些技术在环境消毒方面存在诸多不利,譬如过长的消杀时间、昂贵的特殊设备以及伴生的环境污染.过氧化氢是一种环境友好的多功能氧化剂,其分解的最终产物是氧气和水,广泛用于伤口消毒、纸浆和纺织品漂白、废水废气处理、化学合成、半导体清洗以及洗涤剂.目前,过氧化氢的生产严重依赖于传统的蒽醌法,该技术由Riedl和Pfleiderer于1939年提出,并沿用至今.然而,蒽醌法能耗高,该技术仅在较大规模上经济可行.不稳定的过氧化氢溶液存在危险性,这对大宗过氧化氢的运输和存储提出了额外的挑战.电化学合成过氧化氢被认为可有效替代传统蒽醌法,其反应条件温和,所需反应物是环境中广泛存在的水和氧气;与可再生能源相结合,有望实现分布式原位生产过氧化氢.过氧化氢既可以通过两电子的水氧化反应生成,又可以经由两电子的氧还原反应产生.Berl等在上世纪30年代首次报道了经由两电子的氧还原反应合成过氧化氢,并随后在1991年将其商业化(亦即Huron-Dow法).自此,Huron-Dow法被广泛用于纸浆和纸张的漂白过程.最近,Huron-Dow法进一步演变为电子-芬顿工艺,并被广泛用于饮用水净化和污水处理.目前,涉及高活性和高选择性的电化学合成过氧化氢的优秀综述见诸各大期刊;但是鲜有综述探讨该技术在环境消毒方面的应用.为了探寻提升公共卫生安全的有效替代方法,本文探讨了在电催化制备过氧化氢在环境消毒方面的可行性.本文涵盖三个主题,从基础理论到实践两个层次探讨了该技术在实际应用中的可行性.首先,回顾了H2O2消杀病原体的机理;其次,讨论了影响电催化制备过氧化氢的关键因素,并对现有的用于两电子水氧化和氧还原的催化剂进行了系统性的评述;最后,讨论了电极和电解池的合理设计,以实现电催化制备过氧化氢在实际中的应用.本文试图为最终实现电催化制备过氧化氢在环境消毒,尤其是公共卫生领域,提供可寻的研究方向.     

A novel non-enzymatic glucose sensor modified with Fe2O3 nanowire arrays

Fe(2)O(3) was generally considered to be biologically and electrochemically inert, and its electrocatalytic functionality has been rarely realized directly in the past. In this work, Fe(2)O(3) nanowire arrays were synthesized and electrochemically characterized. The as prepared Fe(2)O(3) nanomaterial was proved to be an ideal electrode material due to the intrinsic peroxidase-like catalytic activity. The Fe(2)O(3) nanowire array modified glucose sensor exhibited excellent biocatalytic performance towards the oxidation of glucose with a response time of <6 s, a linear range between 0.015-8 mM, and sensitivity of 726.9 μA mM(-1)cm(-1). Additionally, a high sensing selectivity towards glucose oxidation in the presence of ascorbic acid (AA) and dopamine (DA) has also been obtained at their maximum physiological concentrations, which makes the Fe(2)O(3) nanomaterial promising for the development of effective electrochemical sensors for practical applications.     

S‐Click Reaction for Isotropic Orientation of Oxidases on Electrodes to Promote Electron Transfer at Low Potentials

Electrochemical sensors are essential for point‐of‐care testing (POCT) and wearable sensing devices. Establishing an efficient electron transfer route between redox enzymes and electrodes is key for converting enzyme‐catalyzed reactions into electrochemical signals, and for the development of robust, sensitive, and selective biosensors. We demonstrate that the site‐specific incorporation of a novel synthetic amino acid (2‐amino‐3‐(4‐mercaptophenyl)propanoic acid) into redox enzymes, followed by an S‐click reaction to wire the enzyme to the electrode, facilitates electron transfer. The fabricated biosensor demonstrated real‐time and selective monitoring of tryptophan (Trp) in blood and sweat samples, with a linear range of 0.02–0.8 mm . Further developments along this route may result in dramatic expansion of portable electrochemical sensors for diverse health‐determination molecules.     

Microfluidic device architecture for electrochemical patterning and detection of multiple DNA sequences

Electrochemical biosensors pose an attractive solution for point-of-care diagnostics because they require minimal instrumentation and they are scalable and readily integrated with microelectronics. The integration of electrochemical biosensors with microscale devices has, however, proven to be challenging due to significant incompatibilities among biomolecular stability, operation conditions of electrochemical sensors, and microfabrication techniques. Toward a solution to this problem, we have demonstrated here an electrochemical array architecture that supports the following processes in situ, within a self-enclosed microfluidic device: (a) electrode cleaning and preparation, (b) electrochemical addressing, patterning, and immobilization of sensing biomolecules at selected sensor pixels, (c) sequence-specific electrochemical detection from multiple pixels, and (d) regeneration of the sensing pixels. The architecture we have developed is general, and it should be applicable to a wide range of biosensing schemes that utilize gold-thiol self-assembled monolayer chemistry. As a proof-of-principle, we demonstrate the detection and differentiation of polymerase chain reaction (PCR) amplicons diagnostic of human (H1N1) and avian (H5N1) influenza.     

Nanomaterials‐based Electrochemical Sensing of Cardiac Biomarkers for Acute Myocardial Infarction: Recent Progress

The development of the methods for early and accurate diagnosis of acute myocardial infarction are needed to facilitate immediate treatment of patients. One of the ways to achieve that is the detection of cardiac biomarkers for myocardial infarction, such as thrombin, cardiac troponins (I and T), myoglobin, etc. Nanotechnology has played an important role in the development of sensitive and efficient electrochemical sensors for cardiac biomarkers. In this review, we discuss recent progress on nanomaterial‐based electrochemical sensing of various cardiac biomarkers for acute myocardial infarction.     

Development of a paper-based,inexpensive, and disposable electrochemical sensing platform for nitrite detection

Electrochemical techniques are attractive for nitrite detection owing to their intrinsic advantages. However, traditional electrochemical sensors often suffer from the effects of fouling due to the adsorption of oxidation products on the electrode surface. In this work, a paper-based, inexpensive, disposable electrochemical sensing platform was developed for nitrite analysis based on a simple and efficient vacuum filtration system. Taking advantage of the physicochemical properties of graphene nanosheets and gold nanoparticles, the mass transport regime of nitrite at the paper-based electrode was thin layer diffusion rather than planar diffusion. In comparison with the electrochemical responses of commercial gold electrodes and glassy carbon electrodes (GCE), a considerably larger current signal was seen at the paper-based sensing interface, which significantly improved its sensitivity for nitrite detection. In particular, the paper-based electrode was a disposable sensing device, so that it effectively avoided the fouling effect arising from the adsorption of oxidation products. Moreover, the paper-based sensing platform made it possible to determine nitrite in environmental and food samples in an accurate, convenient, inexpensive, and reproducible way, indicating that the proposed system is promising for practical applications in environmental monitoring and public health.     

Ultraflexible Screen‐Printed Graphitic Electroanalytical Sensing Platforms

The pursuit of ultraflexible sensors has arisen from the recent implementation of electrochemical sensors into wearable clothing where extensive mechanical stress upon the sensing platform is likely to occur. Such scenarios have witnessed screen‐printed electrodes being incorporated into the waistband of undergarments for the determination of key analytes while others have reported incorporation into a neoprene wetsuit. In these conformations, the substrates which the sensors are printed upon need to be ultraflexible and capable of withstanding extensive individual mechanical stress. Therefore the composition, thickness and its combination of screen‐printed ink require extensive consideration. A common short‐coming within the field of screen‐printed derived sensors is the lack of consideration towards the substrate material employed, and is rather in favour of the development of new electrode geometries and screen‐printing inks. In this paper we explore the screen‐printing of graphite based electroanalytical sensing platforms onto graphic paper commonly used in house‐hold printers, and for the first time both tracing paper and ultraflexible polyester‐based substrates are used. These sensors are electrochemically benchmarked with the redox probes hexaammine‐ruthenium(III) chloride and potassium ferrocyanide(II). The effect of mechanical contortion upon two types of electrode substrates is also performed where it was found that these ultraflexible based polyester‐based electrodes are superior to the previously reported ultraflexible paper electrodes since they can withstand extensive mechanical contortion, yet they still give rise to useful electrochemical performances. Most importantly the ultraflexible polyester electrodes do not suffer from capillary action as observed in the case of paper‐based sensors causing the solution to wick‐up the electrode towards the electrical connections resulting in electrical shorting, therefore compromising the electrochemical measurement; as such this new substrate can be used as a replacement for paper‐based substrates and yet still be resilient to extreme mechanical contortion. A new configuration is also explored using these electrode substrate supports where the working carbon electrode contains the electrocatalyst, cobalt(II) phthalocyanine (CoPC), and is benchmarked towards the electroanalytical sensing of the model analytes citric acid and hydrazine which demonstrate excellent sensing capabilities in comparison to previously reported screen‐printed electrodes.     

Copolymerization of luminol on screen-printed cells for single-use electrochemiluminescent sensors

An efficient electrochemiluminescent (ECL) single-use sensor for H(2)O(2) is presented based on an electropolymerized film prepared on screen-printed gold electrode (gold SPE). A study of the copolymerization of luminol in the presence of different monomers was carried out. The polymeric films were grown potentiodynamically with a potential interval between -0.2 and 1.0 V in 0.2 M H(2)SO(4) and were characterized by their electrochemical, electrochemiluminescent, and superficial features. The polymer with the most efficient growth and ECL emission was poly(luminol-3,3',5,5'-tetramethylbenzidine) at 1:5 ratio. These prepared SPE cells present good mechanical and photoemissive properties. A semi-logarithmic linearization shows a noticeable four decade-width concentration range with a limit of detection (LOD) of 2.6 × 10(-9) M and a precision of 10.2% (n = 5; as relative standard deviation, RSD) in the medium range level. The described SPE ECL sensors will be useful for the determination of oxidase substrates in ECL single-use biosensors.     

石墨烯在自供能传感系统中的应用

随着现代社会智能化的加速发展,传感系统中传感器的数量、密度和分布范围不断增加,传统的供能方式难以满足如此复杂多变的传感器供能需求,从周围环境中收集能量并转化为电能的自供能传感器件是解决这一难题的有效途径。石墨烯不仅具有优异的传感性能,而且在各种能源器件中有广泛的应用,这为基于石墨烯的自供能传感器件设计提供了便利。近年来,人们已经研究和发展了多种多样的石墨烯自供能传感器件。本文基于自供能器件的基本能量供给原理,包括电化学供能、光伏供能、摩擦电供能、水伏供能以及热电、压电、热释电等其它供能,分别介绍了石墨烯在自供能传感器件中的应用,并展望了基于石墨烯的自供能传感器件的未来发展、挑战和前景。