Chemical sensors based on atomically-thin two-dimensional (2D) semiconductors and their hetero-structures are promising candidates for sensing various agents with unipolar sensitivity, excellent ...selectivity, high responsivity and great long-term stability for versatile applications at the wide working temperature range. Further improvement of sensors’ main characteristics is inseparably connected to the hetero-interfacial engineering of few-nm thick sensing electrodes (SE) at nanoscale. Review focuses on advantages and advances of the atomic layer deposition (ALD) enabling technology among others different SE preparation methods and elaborates the devised strategies towards SE fabrication process, their phase compositions and nano-architectures as well as catalytic effects of 2D nanomaterials forming hetero-structured SE. The discussed ALD advantages ensure the employment of this technique for further development of hetero-structured 2D semiconductors with unique properties. Results, mainly obtained during last few years for ALD-enabled gaseous, aqueous and bio-sensors have been used for showing an opportunity of nano-structural engineering of 2D hetero-structures for optimization of sensing characteristics. Critical thinking and established ideas regarding the future development of hetero-structured 2D hybrid materials-based chemical sensors are discussed.
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•Enzymeless detection of diazinon based on Au-Pt nanoclusters-graphene modified sensor.•Direct and ultrasensitive electrochemical detection of diazinon at 0.50 V vs. Ag/AgCl.•The ...sensor was utilized for detection of diazinon in water, fruit and vegetable samples.
A new sensing layer composed of BSA templated Au-Pt bimetallic nanoclusters (Au-Pt@BSA/GCE) and graphene nanoribbons (GNRs) was employed for the rapid, selective and sensitive determination of diazinon as an enzyme-less electrochemical sensor. The UV–vis absorption spectroscopy, fluorescence spectroscopy, transmission electronic microscopy, X-ray diffraction and Fourier transform infrared techniques were used to investigate the size, morphology, and structure of the synthesized nanocomposite. Additionally, the electrochemical properties of the sensor were investigated by cyclic voltammetry, square wave anodic stripping voltammetry and electrochemical impedance spectroscopy. The results showed that Au-Pt@BSA-GNRs/GCE significantly catalyzes the oxidation and reduction of diazinon during electrochemical detection. The linear ranges of diazinon were between 0.01–10.0 and 10.0–170 μM, with a detection limit of 0.002 μM. The selectivity, stability, and reproducibility of Au-Pt@BSA-GNRs/GCE were studied, and obtained data indicates the great potential of the sensor as an alternative to enzyme inhibition-based biosensors for the determination of diazinon. The constructed electrode was employed for the determination of diazinon in some real samples with complex matrices such as soil, diverse water, fruit, and vegetables. The results indicate the excellent capability of the method for the detection of diazinon in real samples in comparison with the standard method.
We conducted a set of experiments to show that EV71 virus could induce a self-assembly process of silver nanoparticles in polyacrylamide. Silver nanoparticles were self-assembled aggregated to form ...EV71 specific binding site in the presence of EV71 template. The EV71 composites was applied as an EV71 biosensor to detect EV71 down to 0.0001 PFU/mL and 0.001 PFU/mL in PBS and serum respectively. Partial response to Coxsackie but Zika virus was observed. This was a direct method for EV71 detection in serum alternative to a widely used indirect antibody detection. The virus concentration that triggered silver nanoparticles aggregation was extremely low. This suggests more concern should be put on application of nanoparticles in humans where virus at small quantity could trigger nanoparticle aggregation.
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•The incorporation of enterovirus 71 (EV71) into silver nanoparticle (AgNPs) resulted in nanoparticle aggregation.•This aggregation represented a self-assembly process that lead to AgNP clusters.•These AgNP clusters possessed EV71 recognition property.•The biosensor developed from these composites demonstrated high selectivity towards EV71 compared to other viruses.
Real‐time monitoring of mental stress biomarkers in sweat provides the possibility to evaluate mental status in a precise manner. In general, wearable sweat sensors suffer from inconvenient sweat ...collection, low levels of diagnostic biomarkers in sweat, sophisticated signal processing, and challenges with data visualization. To overcome these challenges, herein an integrated wearable sweat‐sensing patch for continuous analysis of stress biomarkers (cortisol, Mg2+, and pH) at rest is demonstrated. The sweat sensing patch comprised a microfluidic chip, a highly sensitive sensing platform, an on‐site signal processing circuitry (SPCs), and a smartphone installed with a home‐developed display software. The sweat collection at rest is realized using a microfluidic chip without perspiration assistance. A ternary composite electrode is designed to obtain good conductivity, high surface area, and massive reactive sites, thereby yielding excellent electrochemical performances and high sensitivity to trace stress biomarkers. The on‐site SPC has the function of signal transduction, conditioning, processing, and wireless transmission. The detection results can be displayed on a smartphone through the software. This work represents a significant scientific and technological advancement toward indexing mental stress status and can be used as an innovative tool for psychological diagnosis.
The wearable sweat sensing patch fabricated integrates a microfluidic chip, an electrochemical sensing patch, and an on‐site signal processing circuitry capable of simultaneously detecting cortisol, magnesium ions, and pH in sweat. The detection results can be wirelessly transmitted to smartphones in real time to assess a person's mental health.
Amino acids are the building blocks of proteins and muscle tissue. They also play a significant role in physiological processes related to energy, recovery, mood, muscle and brain function, fat ...burning and stimulating growth hormone or insulin secretion. Accurate determination of amino acids in biological fluids is necessary because any changes in their normal ranges in the body warn diseases like kidney disease, liver disease, type 2 diabetes and cancer. To date, many methods such as liquid chromatography, fluorescence mass spectrometry, etc. have been used for the determination of amino acids. Compared with the above techniques, electrochemical systems using modified electrodes offer a rapid, accurate, cheap, real-time analytical path through simple operations with high selectivity and sensitivity. Nanomaterials have found many interests to create smart electrochemical sensors in different application fields e.g. biomedical, environmental, and food analysis because of their exceptional properties. This review summarizes recent advances in the development of nanomaterial-based electrochemical sensors in 2017–2022 for the detection of amino acids in various matrices such as serum, urine, blood and pharmaceuticals.
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•The state-of-the-art application of nanoparticles in electrochemical analysis of amino acid was reviewed.•Amino acid determination in variety of matrices such as serum, urine, blood and pharmaceuticals is presented.•New approach for amino acid sensor developments and challenges were discussed.
Many commercially available pH sensors are fabricated with a glass membrane as the sensing component because of several advantages of glass-based electrodes such as versatility, high accuracy, and ...excellent stability in various conditions. However, because of their bulkiness and poor mechanical properties, conventional glass-based sensors are not ideal for wearable or flexible applications. Here, we report for the first time the fabrication of a flexible glass-based pH sensor suitable for biomedical and environmental applications where flexibility and stability of the sensor are critical for long-term and real-time monitoring. The sensor was fabricated via a simple and facile approach using the cold atmospheric plasma technique in which a pH sensitive silica coating was deposited from a siloxane precursor onto a carbon electrode. In order to increase the sensitivity and stability of the sensor, we employed a postprocessing step which involves annealing of the silica coated electrode at elevated temperatures. This process was optimized to ensure that the crucial properties such as porosity and hydration functionality were balanced to obtain the best and most reliable sensitivity of the sensor. Our sensitivity test results indicated that these sensors exhibit excellent and stable sensitivity with a slope of about 48 mV/pH (
= 0.998) and selectivity across a pH range of 4 to 10 in the presence of various cations. The optimized sensor has shown stable sensitivity for a long period of time (30 h of immersion) and in different bending conditions. We demonstrate in this investigation that this flexible cost-effective pH sensor can withstand the sterilization process resulting from ultraviolet radiation and shows repeatable sensitivity with less than ±5 mV potential drift from the sensitivity values of the standard optimized sensor.
Recently, there has been significant interest in the utilization of indium-doped cadmium sulfide (CdS) for the detection of chloramphenicol (CAP) in food samples due to its exceptional performance. ...The objective of this research is to develop a simple, rapid, and highly sensitive sensor for CAP detection. CdS possesses remarkable characteristics as a semiconductor material, including a large specific surface area, abundant pore structure, and excellent electrical conductivity. The electrochemical properties of glassy carbon electrodes (GCE) were comprehensively investigated both in their pristine state and when modified with CdS/GCE, CdIn2S4/GCE, Cd1.5In2S4.5/GCE, and Cd2In2S5/GCE. The surface areas of the modified electrodes CdIn2S4/GCE, Cd1.5In2S4.5/GCE, and Cd2In2S5/GCE were measured to be 0.08 cm2, 0.097 cm2, and 0.25 cm2, respectively. Five replicate samples using the optimized proportioned electrode Cd2In2S5/GCE resulted in a response error below 5%. These results indicate that the composite demonstrates exceptional conductivity and reproducibility while maintaining satisfactory sensitivity and high specificity. The proposed sensor based on Cd2In2S5/GCE exhibited an impressive dynamic linear range from 10 nmol/L to 20 μmol/L with an exceptionally low detection limit of 3.8 nmol/L and remarkable sensitivity of 0.38 μA μm−1 cm−2. This sensor successfully quantified CAP in water samples with a satisfactory recovery rate ranging from 99.5% to 100.3%, accompanied by an RSD below 7.6%. Consequently，this developed electrochemical sensor presents itself as the optimal choice for simultaneous determination of CAP in both food and water samples.
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•The Cd2In2S5/GCE exhibited high repeatability and stability, along with excellent anti-interference ability.•An appreciably lower detection limit (3.8 nnol/L) and good sensitivity (0.38 μA μm−1 cm−2).•It shows that this method has a good application prospect in the pretreatment of wastewater containing CAP.
High-temperature electrochemical sensors based on stabilized zirconia play an important role in the control of exhaust emissions and the improvement of product quality and productivity. This paper ...gives an overview about high temperature oxygen sensor, auxiliary electrode type sensor, and mixed potential gas sensor. The response theories of a variety of sensors are elucidated. The related measurement ranges and application examples of oxygen sensors are presented. Since air pollution regulations are being reinforced in many countries, the worldwide demand for oxygen sensors is expected to be growing. Without appropriate solid electrolyte, auxiliary electrode type sensors are developed for measuring phosphorus, sulfur, silicon, manganese and chromium in melt and CO2, NOx and SOx in gas. We have described recent advances in improving the sensitivity, selectivity and long-term stability of mixed potential gas sensors which could be obtained by selecting suitable SE materials. This paper also reviews the limiting factors in measurement, the properties of stabilized zirconia and the role of electrode configuration in electrochemical sensors.
•Paper presents a review of electrochemical sensors based on stabilized zirconia.•Limiting factors in measurements are discussed.•Critical work of the state-of-the-art in the electrochemical sensors is presented.•Electrode reaction at the TPB and gas diffusion within electrode are discussed.
