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Cyromazine is an insect growth regulator insecticide with high selectivity and is widely used in the production and cultivation of fruits and vegetables. In recent years, incidents of excessive cyromazine residues in food have occurred frequently, and it is urgent to establish an accurate, fast, and convenient method for the detection of cyromazine residues to ensure the safety of edible agricultural products. To achieve rapid detection of cyromazine residues, we prepared a molecularly imprinted electrochemical sensor for the detection of cyromazine residues in agricultural products. Samples of tomato (Lycopersicon esculentum Miller), cowpea (Vigna unguiculata), and water were tested for the recovery rate of cyromazine. The results showed that the concentration of cyromazine showed a good linear relationship with the peak response current of the sensor developed in this study. The lower limit of detection for cyromazine was 0.5 µmol/L, and the sensor also had good reproducibility and interference resistance. This paper can be used as a basis for the study of methods for the detection of cyromazine residues in edible agricultural products. [ABSTRACT FROM AUTHOR]

Wearable sweat sensors are a rapidly rising research area owing to their convenience for personal healthcare and disease diagnosis in a real-time and noninvasive manner. However, the fast and scalable fabrication of flexible electrodes remains a major challenge. Here, we develop a wearable epidermal sensor for multiplexed sweat analysis based on the laser-induced graphene (LIG) technique. This simple and mask-free technique allows the direct manufacturing of graphene electrode patterns on commercial polyimide foils. The resulting LIG devices can simultaneously monitor the pH, Na+, and K+ levels in sweat with the sensitivities of 51.5 mV/decade (pH), 45.4 mV/decade (Na+), and 43.3 mV/decade (K+), respectively. Good reproducibility, stability, and selectivity are also observed. On-body testing of the LIG-based sensor integrated with a flexible printed circuit board during stationary cycling demonstrates its capability for real-time sweat analysis. The concentrations of ions can be remotely and wirelessly transmitted to a custom-developed smartphone application during the period in which the sensor user performs physical activities. Owing to the unique advantages of LIG technique, including facile fabrication, mass production, and versatile, more physiological signals (glucose, uric acid, tyrosine, etc.) could be easily expanded into the LIG-based wearable sensors to reflect the health status or clinical needs of individuals. [ABSTRACT FROM AUTHOR]

Wearable sweat electrochemical sensors have attracted wide attention due to their advantages of non-invasive, portable, real-time monitoring, etc. However, existing sensors still have some problems with efficient sweat collection. Microfluidic channel technology and electrospinning technology are commonly used to collect sweat efficiently, but there are some limitations such as complex channel design and multiple spinning parameters. Besides, existing sensors are mostly based on flexible polymers, such as, PET, PDMS, PI and PI, which have limited wearability and permeability. Based on the above, all fabric and dual-function flexible wearable sweat electrochemical sensor is proposed in this paper. This sensor uses fabric as the raw material to implement the directional transport of sweat and the multi-component integrated detection dual functions. Meanwhile, the high-efficiency collection of sweat is obtained by a Janus fabric, wherein one side of the selected silk is superhydrophobic graft treated and the other side is hydrophilic plasma treated. Therefore, the resulting Janus fabric can effectively transfer sweat from the skin side to the electrode, and the minimum sweat droplet can reach 0.2 μL to achieve micro-volume collection. Besides, the patterned sensor, made of silk-based carbon cloth, is fabricated using a simple laser engraving, which could detect Na+, pH, and glucose instantaneously. As a result, these proposed sensors can achieve good sensing performance and high-efficiency sweat collection dual functionality; moreover, it has good flexibility and comfortable wearability. [Display omitted] • The flexible substrate, electrode and sweat collection layers are all made of fabric. • Full-fabric sweat sensors have good flexibility and wearability. • Full-fabric sweat sensors have the dual functions of sweat collection and detection. • Janus fabric can achieve micro-volume sweat collection of 0.2 μL. [ABSTRACT FROM AUTHOR]

In organic electrochemical transistor (OECT) based glucose sensors Pt-based electrodes are usually used as the gate electrodes due to its excellent electrocatalytic activity. In this paper, a cheap and biocompatible material, TiO 2 nanotube arrays (TNTAs), was used as the gate electrode of the OECT device for the first time. It is encouraging that the sensing performance of OECTs using TNTAs-based gate electrodes is comparable to or better than those of the previously reported OECTs using Pt-based gate electrodes. Highly sensitive and selective OECT devices can be obtained by modifying TNTAs electrodes with Pt nanoparticles (Pt-NPs) and enzyme (glucose oxidase). The device shows a linear response to the logarithm of glucose concentration over the range from 100 nM to 5 mM, and the detection limit as low as 100 nM was achieved, which is three orders of magnitude lower than that of a conventional electrochemical measurement with the same electrode. On the other hand, the glucose can be selectively detected in the presence of interferences, such as ascorbic acid and uric acid, when the gate electrode is modified with Nafion. Moreover, the device presents a good stability and reproducibility. By modifying with other specific enzymes and nanomaterials, it is expected that many other type of enzyme sensors with high sensitivity and selectivity could be realized. [ABSTRACT FROM AUTHOR]

• A smartphone-based water quality monitoring system was successfully constructed. • It comprised of a whole-copper electrochemical sensor, a hand-held detector, a smartphone, and a Cloud map website. • The hand-held detector can perform CA, SWV, and LSV methods. • The detection of Pb2+ ions and COD was realized by the smartphone-based system. • Spatiotemporal mapping of water contamination was displayed on the central website. Portable, rapid, and cost-effective detection of environmental contamination remains an important challenge in the field of water quality analysis. Herein, we described a smartphone-based water quality monitoring system that allowed for the quantification of Pb2+ ions and chemical oxygen demand (COD) at an exact location. The system was composed of four main parts: (i) a whole-copper electrochemical sensor, (ii) a hand-held detector, (iii) a smartphone installed with a custom application program, and (iv) a Cloud map website. The sensor chips were made of low-cost copper, including microfabricated Cu working electrodes, Cu counter electrodes, and Cu/CuCl 2 reference electrodes. The hand-held detector (∼50 g) can perform several types of electroanalytical techniques, including chronoamperometry, cyclic voltammetry, linear sweep voltammetry, and square wave voltammetry. With an Application (App), the smartphone was used to control the detector and visualize the testing results in real time. A Cloud map website was used to receive and display the contamination concentrations and geographic locations for public sharing and viewing. Since the smartphone-based system is cost-effective, small in size, field-portable, and fully wireless, it shows great potential for applications in resource-limited settings. [ABSTRACT FROM AUTHOR]

Organic electrochemical transistors (OECTs) are promising devices for applications in in vitro and in vivo measurements. OECTs have two important sensing interfaces for signal monitoring: One is the gate electrode surface; the other is the channel surface. This mini review introduced the new developments in chemical and biological detection of the two sensing interfaces. Specific focus was given on the modification technological approaches of the gate or channel surface. In particular, some unique strategies and surface designs aiming to facilitate signal-transduction and amplification were discussed. Several perspectives and current challenges of OECTs development were also briefly summarized. [ABSTRACT FROM AUTHOR]

A competitive smartphone-based portable electrochemical aptamer sensing system was developed for MC-LR detection. The platform was composed with a smartphone-controlled portable electrochemical system, a smartphone with custom application and a screen-printed carbon electrode (SPCE). The portable electrochemical system consisted a homemade ARM STM32 with chronoamperometry (CA), cyclic voltammetry (CV) and square wave voltammetry (SWV) modules that had a similar performance to commercial electrochemical workstations. The control of the portable electrochemical system, reception and visualization of the assay results were implemented by a smartphone. SPCE was modified by in situ electrodeposition with gold nanoparticles (AuNPs) and reduced graphene oxide (rGO). Subsequently, the aptamer was incubated onto the SPCE through Au-S bonds. The complementary DNA labeled with methylene blue (cDNA-MB) was conjugated onto the surface of MXene to form the probe for signal amplification. The competitive aptasensor was accomplished when the probe was complemented with the aptamer. The fabricated system exhibited the outstanding capability for the determination of MC-LR over a range of 0.0001–5 nM with a limit of detection of 4 × 10−5 nM. Furthermore, the system demonstrated acceptable stability, reproducibility, specificity and high recovery rate. The smartphone-based competitive aptasensor system exhibited the merits of portability, low-cost and fast-response to satisfy the demand for on-site detection of MC-LR. [Display omitted] • A portable smartphone-based competitive electrochemical aptasensor was developed for MC-LR determination. • A multifunctional portable electrochemical system was developed for CA, CV and SWV measurement. • Mxene/cDNA-MB was applied as a probe for signal enhancement. • The portable system exhibited the detection limit of 4 × 10-5 nM. [ABSTRACT FROM AUTHOR]

A highly sensitive and selective sensor is urgently needed in many practical H 2 O 2 detection, such as water quality monitoring, quality control of food products, and so on. However, the traditional three electrode system limits its further development in recent years due to its difficulty in miniaturization and integration. To effectively improve its sensitivity and selectivity, highly-ordered TiO 2 nanotube arrays (TNTAs) are modified with Pt nanoparticles and Prussian blue (PB) nanotubes and creatively combines with thin-film transistor (TFT) based on ZnO to prepare an electrochemical sensor. The sensor uses PBNCs as recognition units for the specific detection of H 2 O 2, and the generated electrical signal is amplified by TFT. Thus, a highly sensitive and selective H 2 O 2 sensor is achieved. The detection limit of the sensor is as low as 5.19 nM, which is three orders of magnitude lower than the conventional electrochemical detection methods using the same electrode. The sensor also possesses wider linear detection range of 0.1–50 μM and 50 μM–5 mM comparable to that of other reported H 2 O 2 sensors. Besides, the sensor has good selectivity for H 2 O 2 in the presence of common interferences such as ascorbic acid, uric acid, glucose, and dopamine. Furthermore, the device presents good reproducibility and exhibits good long-term stability over 27 days of continuous measurement. This study offers important insights for the rational design of sensors with high sensitivity and selectivity. [Display omitted] • H 2 O 2 sensor based on ZnO thin-film transistors was proposed using PBNCs/Pt-NPs/TNTAs electrode. • Detection limit is three orders of magnitude lower than conventional electrochemical methods under the equivalent conditions. • The long-term stability has been demonstrated by the constant results from day 1 to day 27. • A low detection limit of 5.19 nM and a wide linear detection range were obtained. • Inherent amplification of the transistor helps construct highly sensitive and selective H 2 O 2 sensors. [ABSTRACT FROM AUTHOR]

• A smartphone-based nitrite sensing system was successfully constructed. • The system could detect nitrite as low as 0.2 μM. • A smarphone application was designed to collect and display the sensing data. • Spatiotemporal nitrite contamination map could be displayed on the smartphone. Because trace amounts of nitrite would cause adverse effects on human health, the development of low-cost, portable, and easy-to-use tools is very significant for tracking and evaluating nitrite contamination in water. Herein, we described a smartphone-based electrochemical system for rapid quantification and mapping of nitrite contamination. The system contained a smartphone, a hand-held detector, and a modified screen-printed carbon electrode (SPCE). With a home-made Android application, the smartphone was used to control the detector, display the detection results, and link the system to the Cloud. The hand-held detector (∼42 g) was designed to apply the excitation signals on the modified SPCE and transmit the response data to the smartphone via Bluetooth. The SPCE was used as a sensor for nitrite sensing, on which gold nanoparticles, NiO nanoparticles, and reduced graphene oxide were in-situ electrochemically deposited by the system. The smartphone-based system showed excellent analytical performance for the detection of nitrite with a low detection limit of 0.2 μM in a linear range of 1-500 μM. Furthermore, a nitrite contamination map was constructed by measuring the water samples at different locations in Hainan Province, thus showing great potential of this system for water quality monitoring, especially in low-resource countries. [ABSTRACT FROM AUTHOR]