Silver nanostructures - poly(3,4-ethylenedioxythiophene) sensing material prepared by sinusoidal voltage procedure for detection of antioxidants

Single-Fe-Atom Catalyst for Sensitive Electrochemical Detection of Caffeic Acid

A single-atom catalyst (Fe SAs/-N-C) with excellent stability and conductivity was strategically fabricated via high-temperature calcination using the NiFe layered double hydroxide (LDH)/ZIF-8 composite as precursors. With the help of Ni as a catalyst, a great number of carbon nanotubes were produced whereby the isolated carbon bulks were interconnected to form an "island-bridge"-like 3D network structure, which greatly enhanced the exposure of active sites and the electron transfer. Accordingly, caffeic acid (CA) with versatile biological and pharmacological activities was chosen as the model analyte. The Fe SAs/-N-C with Fe-N4 as the catalytic active site was employed to establish the electrochemical sensing of CA with satisfactory sensitivity, selectivity, and long-term stability. This work expands the application range of single-atom catalysts and contributes a significant reference for the synthesis of hybrid double-atom catalysts.

Electrochemical Sensing Platform Based on Metal Nanoparticles for Epinephrine and Serotonin

A sensing platform based on nanocomposite materials composed of gold metal nanoparticles (AuNPs) and conducting polymer (CP) matrix has been developed for serotonin and epinephrine detection. The CP-AuNPs nanocomposite materials have been synthesized onto glassy carbon electrodes (GCE) by using novel electrochemical procedures based on sinusoidal currents (SC). The SC procedures ensured good control of the metal nanoparticles distribution, increased electrochemical surface area, and enhanced analytical performance. The proposed sensing platform displayed good analytical performance toward serotonin and epinephrine detection. A wide linear analytical response toward epinephrine in the range from 10 to 640 μM and a low detection limit of 1.4 μM epinephrine has been obtained. The sensing platform has also displayed a linear response toward serotonin in the range from 10 to 320 μM, with a detection limit of 5.7 μM serotonin. The sensing platform has been successfully applied in the analysis of epinephrine and serotonin in real samples of tap water and urine with good accuracy.

Fast Analysis of Caffeic Acid-Related Molecules in Instant Coffee by Reusable Sonogel-Carbon Electrodes

Reusable Sonogel-Carbon electrodes containing carbon black (SNGC-CB) have been used for the electrochemical analysis of caffeic acid (CA) in real matrices. Measurements were firstly performed in standard solutions, in which SNGC-CB electrodes allowed the electrochemical determination of CA with high sensitivity and low limit of detection, equal to 0.76 μM. The presence of CB nanostructures in the formulation led to improved performances with respect to pristine SNGC electrodes. Then, measurements were performed in four instant coffees of different brands. A comparison between the results obtained by electrochemical, chromatographic and spectroscopic methods showed that SBGC-CB electrodes represent a simple and economic tool for the rapid assessment of caffeic acid-related molecules in instant coffees.

Nanomaterials-based electrochemical sensors for the detection of natural antioxidants in food and biological samples: research progress

Antioxidants are healthy substances that are beneficial to the human body and exist mainly in natural and synthetic forms. Among many kinds of antioxidants, the natural antioxidants have great applications in many fields such as food chemistry, medical care, and clinical application. In recent years, many efforts have been made for the determination of natural antioxidants. Nano-electrochemical sensors combining electrochemistry and nanotechnology have been widely used in the determination of natural antioxidants due to their unique advantages. Therefore, a large number of nanomaterials such as metal oxide, carbon materials, and conducting polymer have attracted much attention in the field of electrochemical sensors due to their good catalytic effect and stable performance. This review mainly introduces the construction of electrochemical sensors based on different nanomaterials, such as metallic nanomaterials, metal oxide nanomaterials, carbon nanomaterials, metal-organic frameworks, polymer nanomaterials, and other nanocomposites, and their application to the detection of natural antioxidants, including ascorbic acid, phenolic acids, flavonoid, tryptophan, citric acid, and other natural antioxidants. In the end, the limitations of the existing nano-sensing technology, the latest development trend, and the application prospect for various natural antioxidant substances are summarized and analyzed. We expect that this review will be helpful to researchers engaged in electrochemical sensors.

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

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.