Recent Progress in Morphology-Tuned Nanomaterials for the Electrochemical Detection of Heavy Metals

Development of an electrochemical sensor utilizing MWCNs-poly(2-aminothiophenol) @AgNPs nanocomposite for the simultaneous determination of Pb2+ and Cd2+ in food samples

This study focuses on the synthesis and characterization of the Multiwall Carbon Nanotubes-Poly(2-aminothiophenol) @silver nanoparticles nanocomposite (MWCNTs-PATP@AgNPs) using different analytical methods. The synthesized MWCNTs-PATP@AgNPs served as an electrocatalytic modifier, enabling the highly selective and sensitive detection of Pb2+ and Cd2+ ions at nanomolar levels using square wave anodic stripping voltammetry. The concentration of MWCNTs- PATP @AgNPs, the type and concentration of the electrolyte, the solution's pH, and the preconcentration conditions, were systematically optimized. A linear response was observed for Pb2+ and Cd2+ within the ranges of 0.5-60.0 nmolL-1 and 8.0-50.0 nmol L-1, respectively, with detection limits of 0.125 nmol L-1 for Pb2+ and 1.47 nmol L-1 for Cd2+. Furthermore, the MWCNTs-PATP@AgNPs sensor demonstrated the capability to selectively detect these target metals in the presence of various common interfering species. The sensor was effectively utilized for the detection of Pb2+ and Cd2+ ions across various real samples.

Synthesis of a triazine based COF and its application for the establishment of an electrochemical sensor for the simultaneous determination of Cd2+ and Pb2+ in edible specimens using Box-Behnken design

The study presented here describes the characterization and synthesis of a triazine-based covalent organic framework using different analytical procedures such as scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, cyclic voltammetry, Brunauer-Emmett-Teller analysis, and electrochemical impedance spectroscopy. The synthesized COF was then utilized as an electrocatalytic modifier for the selective and sensitive determination of Pb2+ and Cd2+ at nanomolar levels via square wave anodic stripping voltammetry. A Plackett-Burman design was employed to screen operational parameters influencing the sensitivity of the electroanalytical method, followed by optimization of the significant variables using Box-Behnken design. A linear response over 1.0-110.0 nmol L-1 and 5.0-300.0 nmol L-1 range for Pb2+ and Cd2+, with detection limits of 1.1 and 1.8 nmol L-1, respectively. Furthermore, the selectivity of the presented electrode over different species was evaluated with no significant interference found. The sensor was applied effectively to determine of Pb2+ and Cd2+ ions in samples.

Electrochemical detection of heavy metals in rice, milk and tap water using free-standing carbon felt electrodes

In this work, a carbon felt (CF) was utilized to fabricate electrochemical sensors for the simultaneous detection of Cd2+, Pb2+ and Hg2+. The working conditions of CF sensors including thermal activation, electrolytes, and enrichment potentials and times were systematically investigated. Under the optimal detection conditions, the resulting sensors showed good linearity in the concentration ranges of 3-10,000, 2-10,000 and 5-10,000 μg/L for the detection of Cd2+, Pb2+ and Hg2+, corresponding to the detection limits of 1, 0.5, and 1 μg/L, respectively. Meanwhile, the resulting electrochemical sensor demonstrates excellent reproducibility and anti-interference. In addition, the CF electrodes maintain good stability even after 180 days of storage at room temperature. In real water, rice and milk samples, the CF electrodes have been successfully utilized for the detection of Cd2+, Pb2+ and Hg2+ and the results were in agreement with those obtained from the inductively coupled plasma mass spectrometry.

Recent Advances in the Application of Bionanosensors for the Analysis of Heavy Metals in Aquatic Environments

Heavy-metal ions (HMIs) as a pollutant, if not properly processed, used, and disposed of, will not only have an influence on the ecological environment but also pose significant health hazards to humans, making them a primary factor that endangers human health and harms the environment. Heavy metals come from a variety of sources, the most common of which are agriculture, industry, and sewerage. As a result, there is an urgent demand for portable, low-cost, and effective analytical tools. Bionanosensors have been rapidly developed in recent years due to their advantages of speed, mobility, and high sensitivity. To accomplish effective HMI pollution control, it is important not only to precisely pinpoint the source and content of pollution but also to perform real-time and speedy in situ detection of its composition. This study summarizes heavy-metal-ion (HMI) sensing research advances over the last five years (2019-2023), describing and analyzing major examples of electrochemical and optical bionanosensors for Hg2+, Cu2+, Pb2+, Cd2+, Cr6+, and Zn2+.

Recent Advances on Electrochemical Sensors for Detection of Contaminants of Emerging Concern (CECs)

Contaminants of Emerging Concern (CECs), a new category of contaminants currently in the limelight, are a major issue of global concern. The pervasive nature of CECs and their harmful effects, such as cancer, reproductive disorders, neurotoxicity, etc., make the situation alarming. The perilous nature of CECs lies in the fact that even very small concentrations of CECs can cause great impacts on living beings. They also have a nature of bioaccumulation. Thus, there is a great need to have efficient sensors for the detection of CECs to ensure a safe living environment. Electrochemical sensors are an efficient platform for CEC detection as they are highly selective, sensitive, stable, reproducible, and prompt, and can detect very low concentrations of the analyte. Major classes of CECs are pharmaceuticals, illicit drugs, personal care products, endocrine disruptors, newly registered pesticides, and disinfection by-products. This review focusses on CECs, including their sources and pathways, health effects caused by them, and electrochemical sensors as reported in the literature under each category for the detection of major CECs.

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.