Evaluation of a Reduced Graphene Oxide-Sb Nanoparticles Electrochemical Sensor for the Detection of Cadmium and Lead in Chamomile Tea

Constructing Fe2O3 nanoparticles in nitrogen-doped carbon materials to enhance the electrochemical sensing performance of Pb2+ and Cd2

N-doped carbon materials are known for their high conductivity, rich N content, and high adsorption activity. When combined with Fe2O3 to form nanocomposites, they can improve the conductivity of Fe2O3 and cause significant changes in the electrochemical sensing interface with the influence of their unique electronic structure. In this work, N-doped carbon nanocomposites (Fe2O3@NCNPs-x) modified with Fe2O3 nanoparticles (Fe2O3 NPs) were synthesized by a simple emulsion polymerization method and carbonized under Ar at a high temperature. X-ray photoelectron spectroscopy indicated that compared with undoped Fe2O3 NPs, the π bond of Fe2O3@NCNPs-1.5 was negatively charged due to the lone pair of electrons near the N atom, acting as an electron donor that enhanced the interaction with HMIs and electron transport, therefore generating more active sites on the surface of Fe2O3@NCNPs-1.5. The obtained Fe2+/Fe3+ ratio was about two times higher than that of undoped Fe2O3 NPs (Fe2O3@NCNPs-1.5: Fe2+/Fe3+ = 1.24; Fe2O3 NPs: Fe2+/Fe3+ = 0.61). The surface oxygen vacancy (OV) concentration reached the maximum level (Fe2O3@NCNPs-1.5: OVs/O1s = 41.7%; Fe2O3 NPs: OVs/O1s = 22%). Fe2O3@NCNPs-1.5/GCE also showed enhanced electrochemical performance for detecting Pb2+ and Cd2+, with a limit of detection (LOD, S/N = 3) of 4.92 and 18.79 nM, respectively. Electrochemical adsorption tests suggested that Fe2O3@NCNPs-1.5/GCE had the strongest adsorption capacity for Pb2+ and Cd2+ in comparison with other modified electrodes, suggesting that different N contents led to different absorbability for heavy metal ions (HMIs). Therefore, when the metal oxide nanoparticles are loaded on compatible carriers, the jointly constructed nanocomposites can be used as the active materials for efficiently detecting HMIs, providing a new concept for designing highly active electrochemical sensors.

Reduced graphene oxide: Biofabrication and environmental applications

Green synthesis of high-quality reduced graphene oxide (rGO) from agro-industrial waste resources remains attractive owing to its outstanding environmental benefits. The remarkable properties of rGO include excellent morphology, uniform particle size, good optical properties, high conductivity, nontoxicity, and extraordinary chemical stability. Traditional methods for the synthesis of rGO nanomaterials involve several chemical reactions including oxidation, carbonization, toxic solvent, and pyrolysis which produce harmful byproducts. Green preparation of rGO is an emerging area of research in graphene technology which is cost-effective and sustainable in the procedure. Owing to the uniform particle rGO particle size, these smart nanomaterials have wide applicability, including in metal ions and pollutant sensing and adsorption, photocatalysis, optoelectrical devices, medical diagnosis, and drug delivery. Here we review the physicochemical properties of rGO, the biowaste sources and green methods of rGO synthesis, and the diverse applications of rGO, including in water purification and the biomedical fields. With this review, covering more than 200 research articles published on rGO in the last eight years ending in 2022, we aim to provide a quick guide for researchers seeking up-to-date information on the properties, production, and applicability of rGO, with special attention to rGO applications in water purification and the biomedical fields.

Simultaneous Quantitation of Lead and Cadmium on an EDTA-Reduced Graphene Oxide-Modified Glassy Carbon Electrode

Cadmium (Cd) and lead (Pb) are classified as category one toxicants. The provisional guideline values, according to the World Health Organization (WHO), for Cd and Pb are 3 and 10 ppb, respectively. An easy, quick, and cheap analytical technique is in demand for the determination of these toxic heavy metals in water. Hence, a novel electrochemical sensing platform is developed by modifying the glassy carbon electrode with ethylenediaminetetraacetic acid (EDTA)-functionalized reduced graphene oxide (ErGO) for the low-cost simultaneous quantitation of toxic heavy-metal ions, lead and cadmium, in real water samples. EDTA is grafted to the surface of graphene oxide, via amine linkage, and the oxygen functionality is reduced by a green agent, tyrosine. Various physical and electrochemical characterizations of the as-prepared electrocatalytic material were performed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), ζ-potential, ultraviolet diffuse reflectance spectroscopy (UV-DRS), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), etc. The glassy carbon electrode (GCE) is modified with ErGO by a simple drop-casting method for simultaneous metal-ion quantitation by differential pulse voltammetry (DPV). EDTA functionalization of graphene oxide and its further reduction using the green agent enhance the stability and sensitivity of the electrode substrate. The limits of detection for cadmium and lead ions calculated for ErGO/GCE are 1.02 and 2.52 ppb, while the limits of quantification for lead and cadmium ions are 3.41 and 8.4 ppb, and their sensitivities are 0.8 and 0.6 nA/ppb, respectively. Real river water contains 200.2 ± 0.38 ppb of Pb²⁺ ions (mean ± stdev, n = 3) by the DPV technique, which is validated by ICP-OES analysis.

Electrochemical Sensors and Biosensors for the Analysis of Tea Components: A Bibliometric Review

Tea is a popular beverage all around the world. Tea composition, quality monitoring, and tea identification have all been the subject of extensive research due to concerns about the nutritional value and safety of tea intake. In the last 2 decades, research into tea employing electrochemical biosensing technologies has received a lot of interest. Despite the fact that electrochemical biosensing is not yet the most widely utilized approach for tea analysis, it has emerged as a promising technology due to its high sensitivity, speed, and low cost. Through bibliometric analysis, we give a systematic survey of the literature on electrochemical analysis of tea from 1994 to 2021 in this study. Electrochemical analysis in the study of tea can be split into three distinct stages, according to the bibliometric analysis. After chromatographic separation of materials, electrochemical techniques were initially used only as a detection tool. Many key components of tea, including as tea polyphenols, gallic acid, caffeic acid, and others, have electrochemical activity, and their electrochemical behavior is being investigated. High-performance electrochemical sensors have steadily become a hot research issue as materials science, particularly nanomaterials, and has progressed. This review not only highlights these processes, but also analyzes and contrasts the relevant literature. This evaluation also provides future views in this area based on the bibliometric findings.

Simultaneous determination of cadmium(ii), lead(ii), copper(ii) and mercury(ii) using an electrode modified by N/S co-doped graphene

NSRG has superior sensitivity, selectivity, reproducibility, stability and practicality, exhibiting broad application prospects in the field of electrochemical sensing.

Colloidal chemical bottom-up synthesis routes of pnictogen (As, Sb, Bi) nanostructures with tailored properties and applications: a summary of the state of the art and main insights

Adjusting the colloidal chemistry synthetic parameters for pnictogen nanostructures leads to a fine control of their physical properties and the resulting performance in applications. Image adapted from Slidesgo.com.