Popularity of graphene oxide (GO) became ballistic in the last few years – in short, it almost seems that now everyone wants to work with graphene. However, as the number of electrochemical papers about graphene grows, so is the amount of misinterpretations. Our work was mostly focused on preparation of GO and its electrochemical properties, namely catalysis. Our results show, that chemical preparation of GO by strong oxidation is very tricky. Several approaches were tested, such as different sizes of graphite particles, oxidation mixtures, even repetitive preparations under the same conditions usually resulted in different products. Another big topic are impurities which are present due to natural occurrence in graphite and some of them might be also introduced during purification processes of GO. This could also lead to often observed catalytic activity of graphene. From our observations neither selectivity nor significant electrocatalytic abilities of the reduced graphene oxide modified electrodes towards H2O2 were observed. Moreover, our results suggest that GO does not need linking molecules in order to be deposited onto the surface of the electrodes, since it attaches spontaneously and keeps its electrochemical properties. Graphene is usually reported as a superior material, but its proper description and characterization should not be underestimated.

About graphene oxide

Environmental pollution has been a known threat to our world due to the rapid urbanization, changing lifestyle of people, and modern industrialization. Therefore, there is an urgent need to develop novel sensing approaches having promising performance with high reliability and sensitivity for the precise monitoring of various pollutants. Metal–organic frameworks (MOFs) have been intensively investigated by many researchers as electrode modifiers for electrochemical sensing due to their excellent properties and efficiency. Diverse MOF-based electrochemical sensing systems are applied for environmental analysis for the sensitive, rapid and cost-effective determination of various analytes because of their unique structures, and properties, including the tunable pore size, high surface area, high catalytic activity, and high density of active sites. The aim of this review article is to evaluate the application of MOFs in the electrochemical sensing of environmental pollutants including heavy metal ions, pesticides, phenolic compounds, nitroaromatic compounds, antibiotics, nitrite, and hydrazine. Current limitations and future directions for the application of MOF-based electrochemical sensors for the detection of environmental pollutants are discussed.

Performance of metal-organic frameworks in the electrochemical sensing of environmental pollutants

Diabetes leads to chronic microvascular complications for the heart, kidney, and eyes due to uncontrolled glycemic fluctuations. Self-monitoring blood glucose meters can only provide a snapshot of glucose level and are incapable of capturing the granular glucose fluctuations over the 24 h in day. The clinical research has indicated that random blood glucose fluctuations can lead to organ damage. In pursuit of better glucose management, Continuous Glucose Monitoring (CGM) is emerging as a popular alternative owing to its ability to detect instantaneous changes in glucose levels and to alert the users of impending hypo- or hyper-glycemic events. In the last decade, several CGM devices have been launched in the market based on different glucose sensing chemistries and techniques. More research is still needed to come up with novel bio sensing concepts to make CGM low cost and highly accurate. Here, we elaborate the CGM techniques such as electrochemical, optical, reverse iontophoresis, microdialysis, and impedance spectroscopy. We emphasize on the widely used electrochemical CGMs with a focus on sensor design and bio-compatibility. We also provide an outlook for the future technologies, highlighting the need for innovative materials, possibility of integrating with the Internet of Things (IoT) for real-time e-health monitoring.

Review—Electrochemistry and Other Emerging Technologies for Continuous Glucose Monitoring Devices

Biosensor can convert the concentration of biological analyte into an electrical signal or other signals for detection. It is widely used in medical diagnostics, food safety, process control and environmental monitoring fields. In recent years, new schemes of stable biosensor interfaces have attracted much attention. Interface design is a vital part of biosensor development, since its stability can be directly related to the quality of sensing performance such as sensitivity, stability and linearity. This review summarized the latest methods and materials used to construct stable biosensor interfaces, and pointed some future perspectives and challenges of them. From the literature, we found that nanomaterials, polymers as well as their composites such as chitosan, cellulose and conducting polymers are the most common materials used in the biosensor interfaces design. Apart from materials, there are increasing developments in monolayer membranes techniques, three-dimensional constructions and other interface techniques. This review is a study of the latest progress in biosensor interface stability solutions, which may provide some references and innovative directions of biosensor interface design for researchers in biosensor fields, and encourage people to further explore new materials and methods.

/pdf/materials-and-methods-of-biosensor-interfaces-with-stability-sexlabtugy.pdf

Materials and methods of biosensor interfaces with stability

Currently, there is growing interest in screening and quantifying antioxidants from biological samples in the quest for natural and effective antioxidants to combat free radical-related pathological complications. Antioxidants play an important role in human health and provide a defense against many diseases. Due to the valuable dietary role of these compounds, the analysis and determination of their amount in food is of particular importance. In recent years, many attempts have been made to provide simple, fast, and economical analytical approaches for the on-site detection and determination of antioxidant activity in food antioxidants. In this regard, electrochemical sensors and biosensors are considered promising tools for antioxidant research due to their high sensitivity, fast response time, and ease of miniaturization; thus, they are used in a variety of fields, including food analysis, drug screening, and toxicity research. Herein, we review the recent advances in sensors and biosensors for the detection of antioxidants, underlying principles, and emphasizing advantages, along with limitations regarding the ability to discriminate between the specific antioxidant or quantifying total antioxidant content. In this work, both direct and indirect methods for antioxidants detecting with electrochemical sensors and biosensors are analyzed in detail. This review aims to prove how electrochemical sensors and biosensors represent reliable alternatives to conventional methods for antioxidant analysis.

/pdf/a-review-on-electrochemical-sensors-and-biosensors-used-in-3vqqcfxn.pdf

A Review on Electrochemical Sensors and Biosensors Used in Assessing Antioxidant Activity

In recent years, non-toxic quantum dot has caught the attention of biomedical fields. However, the inherent cytotoxicity of QDs makes its biomedical application painful, and is a major drawback of this method. In this paper, a non-toxic and water-soluble quantum dot AgInZnS-GO using graphene oxide was synthesized. A simple model of state complex was also established, which is produced through a combination of quantum dots and protein. The interaction between AIZS-GO QDs and human serum albumin (HSA) has significant meaning in vivo biological application. Herein, the binding of AIZS-GO QDs and HSA were researched using fluorescence spectra, Uv-visible absorption spectra, FT-IR spectra, and circular dichroism (CD) spectra. The results of fluorescence spectra demonstrate that AIZS-GO QDs have an obvious fluorescence quenching effect on HSA. The quenching mechanism is static quenching, which implies that some type of complex was produced by the binding of QDs and HSA. These results were further proved by Uv-visible absorption spectroscopy. The Stern-Volmer quenching constant Ksv at various temperatures (298 K, 303 K, 308 K) were acquired from analyzing Stern-Volmer plots of the fluorescence quenching information. The Van't Hoff equation could describe the thermodynamic parameters, which demonstrated that the van der Waals and hydrogen bonds had an essential effect on the interaction. FT-IR spectra and CD spectra further indicate that AIZS-GO QDs can alter the structure of HSA. These spectral methods show that the quantum dot can combine well with HSA. The experimental results showed that AgInZn-GO water-soluble quantum dots have good biocompatibility, which can be combined with proteins to form new compounds which have no cytotoxicity and biological practicability. It provides an important basis for the combination of quantum dots and specific proteins as well as fluorescent labeling.

/pdf/study-on-aginzns-graphene-oxide-non-toxic-quantum-dots-for-55zgloixz7.pdf

Study on AgInZnS-graphene oxide non-toxic quantum dots for biomedical sensing

Bisphenol A (BPA) is an endocrine disruptor that may lead to reproductive disorder, heart disease, and diabetes. Infants and young children are likely to be vulnerable to the effects of BPA. At present, the detection methods of BPA are complicated to operate and require expensive instruments. Therefore, it is quite vital to develop a simple, rapid, and highly sensitive method to detect BPA in different samples. In this study, we have designed a rapid and highly sensitive biosensor based on an effective self-assembled monolayer (SAM) and alternating current (AC) electrokinetics capacitive sensing method, which successfully detected BPA at nanomolar levels with only one minute. The developed biosensor demonstrates a detection of BPA ranging from 0.028 μg/mL to 280 μg/mL with a limit of detection (LOD) down to 0.028 μg/mL in the samples. The developed biosensor exhibited great potential as a portable BPA biosensor, and further development of this biosensor may also be useful in the detection of other small biochemical molecules.

https://www.mdpi.com/2072-666X/11/1/41/pdf

Rapid and Sensitive Detection of Bisphenol A Based on Self-Assembly.

Nitrite is a toxic substance, when excessive nitrite enters the human body, it will be seriously harmful to human. At present, the detection methods of nitrite are complicated to operate and require expensive detection instruments. Therefore, an effective, fast and highly selective nanogold film interdigital electrode sensors that can detect nitrite easily and quickly is developed in the work. Firstly, the variation of the sensitivity of nanogold film nitrite sensors with concentrations (1 mol/L, 10-1 mol/L, 10-2 mol/L, 10-3 mol/L, 10-4 mol/L, and 10-5 mol/L) was measured by experiments. Then, Chrome-black T was modified to the surface of the nanogold film interdigital electrodes by electrochemical polymerization, and the film of chrome-black T had affinity for nitrite ions, so nitrite ions were enriched on the sensor surface. The change law of the impedance signal of the modified nanogold film nitrite sensors after being added to different concentrations of sodium nitrite solution were also concluded. The study demonstrates that the larger the concentration of sodium nitrite solution is added to the modified interdigital electrodes, the smaller impedance and resistance of the modified interdigital electrodes are reflected. Finally, specificity of the modified interdigital electrode sensors has been demonstrated. The novel interdigital electrode sensors can detect the concentration of nitrite solution conveniently and quickly with only 30 s. Therefore, the prospect of applying the novel nanogold film interdigital electrode sensors to the detection of nitrite in blood, body fluid, food and drinking water is promising.

/pdf/a-fast-and-highly-selective-nitrite-sensor-based-on-4zwifxeh07.pdf

A Fast and Highly Selective Nitrite Sensor Based on Interdigital Electrodes Modified With Nanogold Film and Chrome-Black T.

/pdf/electrochemical-biosensors-for-circulating-tumor-dna-1clp4lxt.pdf

Zhijia Peng

Papers

Materials and methods of biosensor interfaces with stability

Study on AgInZnS-graphene oxide non-toxic quantum dots for biomedical sensing

Rapid and Sensitive Detection of Bisphenol A Based on Self-Assembly.

A Fast and Highly Selective Nitrite Sensor Based on Interdigital Electrodes Modified With Nanogold Film and Chrome-Black T.

Electrochemical Biosensors for Circulating Tumor DNA Detection