A novel electrochemical sensor based on a glassy carbon electrode modified with dendrimer functionalized magnetic graphene oxide for simultaneous determination of trace Pb(II) and Cd(II)

Enhanced electrocatalytic activity in MOFs-derived 3D hollow NiCo-LDH nanocages decorated porous biochar for simultaneously ultra-sensitive electrochemical sensing of Cu2+ and Hg2

Layered double hydroxides (LDHs) have attracted significant attention due to their compositional and structural flexibility. However, it is challenging but meaningful to design and fabricate hierarchical mixed-dimensional LDHs with synergistic effects to increase the electrical conductivity of LDHs and promote the intrinsic activity. Herein, 3D hollow NiCo-LDH nanocages decorated porous biochar (3D NiCo-LDH/PBC) has been synthesized by using ZIF-67 as precursor, which was utilized for constructing electrochemical sensing platform to realize simultaneous determination of Cu2+ and Hg2+. The 3D NiCo-LDH/PBC possessed the characteristics of hollow material and three-dimensional porous material, revealing a larger surface area, more exposed active sites, and faster electron transfer, which is beneficial to enhancing its electrochemical performance. Consequently, the developed sensor displayed good performance for simultaneously detecting Cu2+ and Hg2+ with ultra-low limit of detection (LOD) of 0.03 μg L-1 and 0.03 μg L-1, respectively. The proposed sensor also demonstrated excellent stability, repeatability and reproducibility. Furthermore, the sensor can be successfully used for the electrochemical analysis of Cu2+ and Hg2+ in lake water sample with satisfactory recovery, which is of great feasibility for practical application.

Advances in functionalization and conjugation mechanisms of dendrimers with iron oxide magnetic nanoparticles

Iron oxide magnetic nanoparticles (MNPs) are crucial in various areas due to their unique magnetic properties. However, their practical use is often limited by instability and aggregation in aqueous solutions. This review explores the advanced technique of dendrimer functionalization to enhance MNP stability and expand their application potential. Dendrimers, with their symmetric and highly branched structure, effectively stabilize MNPs and provide tailored functional sites for specific applications. We summarize key synthetic modifications, focusing on the impacts of dendrimer size, surface chemistry, and the balance of chemical (e.g., coordination, anchoring) and physical (e.g., electrostatic, hydrophobic) interactions on nanocomposite properties. Current challenges such as dendrimer toxicity, control over dendrimer distribution on MNPs, and the need for biocompatibility are discussed, alongside potential solutions involving advanced characterization techniques. This review highlights significant opportunities in environmental, biomedical, and water treatment applications, stressing the necessity for ongoing research to fully leverage dendrimer-functionalized MNPs. Insights offered here aim to guide further development and application of these promising nanocomposites.

A highly stable electrochemical sensor with antifouling and antibacterial capabilities for mercury ion detection in seawater

The monitoring of heavy metal ions in ocean is crucial for environment protection and assessment of seawater quality. However, the detection of heavy metal ions in seawater with electrochemical sensors, especially for long-term monitoring, always faces challenges due to marine biofouling caused by the nonspecific adsorption of microbial and biomolecules. Herein, an electrochemical aptasensor, integrating both antifouling and antibacterial properties, was developed for the detection of Hg2+ in the ocean. In this electrochemical aptasensor, eco-friendly peptides with superior hydrophilicity served as anti-biofouling materials, preventing nonspecific adsorption on the sensing interface, while silver nanoparticles were employed to eliminate bacteria. Subsequently, a ferrocene-modified aptamer was employed for the specific recognition of Hg2+, leveraging the aptamer's ability to fold into a thymine-Hg2+-thymine (T-Hg2+-T) structure upon interaction, and bringing ferrocene nearer to the sensor surface, significantly amplifying the electrochemical response. The prepared electrochemical aptasensor significantly reduced the nonspecific adsorption in seawater while maintaining sensitive electrochemical response. Furthermore, the biosensor exhibited a linear response range of 0.01-100 nM with a detection limit of 2.30 pM, and realized the accurate monitoring of mercury ions in real marine environment. The research results offer new insights into the preparation of marine antifouling sensing devices, and it is expected that sensors with antifouling and antimicrobial capabilities will find broad applications in the monitoring of marine pollutants.

State-of-the-art nanosensors and kits for the detection of antibiotic residues in milk and dairy products

Antibiotic resistance is increasingly seen as a future concern, but antibiotics are still commonly used in animals, leading to their accumulation in humans through the food chain and posing health risks. The development of nanomaterials has opened up possibilities for creating new sensing strategies to detect antibiotic residues, resulting in the emergence of innovative nanobiosensors with different benefits like rapidity, simplicity, accuracy, sensitivity, specificity, and precision. Therefore, this comprehensive review provides pertinent and current insights into nanomaterials-based electrochemical/optical sensors for the detection of antibitic residues (ANBr) across milk and dairy products. Here, we first discuss the commonly used ANBs in real products, the significance of ANBr, and also their binding/biological properties. Then, we provide an overview of the role of using different nanomaterials on the development of advanced nanobiosensors like fluorescence-based, colorimetric, surface-enhanced Raman scattering, surface plasmon resonance, and several important electrochemical nanobiosensors relying on different kinds of electrodes. The enhancement of ANB electrochemical behavior for detection is also outlined, along with a concise overview of the utilization of (bio)recognition units. Ultimately, this paper offers a perspective on the future concepts of this research field and commercialized nanomaterial-based sensors to help upgrade the sensing techniques for ANBr in dairy products.

2,5-Thienylene-Strapped [26]Hexaphyrin as Multifunctional Chemosensor for Hg2+, Cu2+, and F- Ions

The sensing behavior of 2,5-thienylene-bridged tetrakis(2,6-dichlorophenyl)-[26]hexaphyrin (2) towards various metal ions and anions were investigated by UV-vis and fluorescence spectroscopies. Using this strapped hexaphyrin (2), the molecular sensor displayed highly selective and sensitive colorimetric responses to Cu2+ and Hg2+ in MeOH/THF. The spectral changes are distinctive enough in the visible region of the spectrum to enable naked-eye detection. The detection limits of Cu2+ and Hg2+ using this chemo-sensor in a mixed MeOH/THF solution were 1.978 and 1.283 μM, respectively, and 1.052 μM for F- in dichloromethane. Chemosensor 2,5-thienylene strapped [26]hexaphyrin (2) shows absorption responses both a 1 : 1 molecular ratio for 2 interacting with Cu2+ and Hg2+ and a 1 : 2 ratio between 2 and F- ions.

Recent advance of nanomaterials modified electrochemical sensors in the detection of heavy metal ions in food and water

As one of the main pollutants, heavy metal ions can accumulate in the human body and cause a cascade of damage. Electrochemical sensors provide great prospects for tracing heavy metal ions because of their properties of high sensitivity, low detection limits and fast response. Electrode surface modification materials play a key role in enhancing the performance of electrochemical sensors. Herein, we summarize in detail the recent work on electrochemical sensors modified by carbon nanomaterials (graphene and its derivatives, carbon nanofibers and carbon nanotubes), metal nanomaterials (gold, silver, bismuth and iron), complexes (MOFs, ZIFs and MXenes) and their composites for the detection of heavy metal ions (mainly include Cd(II), Hg(II), Pb(II), As(III), Cu(II) and Zn(II)) in food and water. The synthetic strategies, mechanisms, innovations, advantages, challenges and prospects of various electrode modification nanomaterials for the detection of heavy metal ions in food and water are discussed.

Electrochemical sensors modified with iron oxide nanoparticles/nanocomposites for voltammetric detection of Pb (II) in water: A review

Permissible limits of Pb2+ in drinking water are being reduced from 10 μgL-1 to 5 μgL-1, which calls for rapid, and highly reliable detection techniques. Electrochemical sensors have garnered attention in detection of heavy metal ions in environmental samples due to their ease of operation, low cost, and rapid detection responses. Selectivity, sensitivity and detection capabilities of these sensors, can be enhanced by modifying their working electrodes (WEs) with iron oxide nanoparticles (IONPs) and/or their composites. Therefore, this review is an in-depth analysis of the deployment of IONPs/nanocomposites in modification of electrochemical sensors for detection of Pb2+ in drinking water over the past decade. From the analyzed studies (n = 23), the optimal solution pH, deposition potential, and deposition time ranged between 3 and 5.6, -0.7 to -1.4 V vs Ag/AgCl, and 100-400 s, respectively. Majority of the studies employed square wave anodic stripping voltammetry (n = 16), in 0.1 M acetate buffer solution (n = 19) for detection of Pb2+. Limits of detection obtained (2.5 x 10-9 - 4.5 μg/L) were below the permissible levels which indicated good sensitivities of the modified electrodes. Despite the great performance of these modified electrodes, the primary source of IONPs has always been commercial iron-based salts in addition to the use of so many materials as modifying agents of these IONPs. This may limit reproducibility and sustainability of the WEs due to lengthy and costly preparation protocols. Steel and/or iron industrial wastes can be alternatively employed in generation of IONPs for modification of electrochemical sensors. Additionally, biomass-based activated carbons enriched with surface functional groups are also used in modification of bare IONPs, and subsequently bare electrodes. However, these two areas still need to be fully explored.

Development of a robust method for Cd(II) ions analysis using CeO2- and CeO2-Cu-BTC-based electrochemical sensors

Simple and sensitive electrochemical sensors were fabricated from cerium oxide (CeO2) and copper-benzene tricarboxylic acid-modified cerium oxide (CeO2-Cu-BTC) materials for differential pulse voltammetric analysis of toxic cadmium (Cd) ions in aqueous solutions. The materials were prepared by hydrothermal method and structurally characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy-dispersive X-ray (SEM-EDX), thermogravimetric analysis (TGA), and X-ray diffraction analysis (XRD). The CeO2-modified carbon paste electrode (CeCPE) and the CeO2-Cu-BTC-modified carbon paste electrode (CeBCPE) were electrochemically characterized by their cyclic voltammetry and electrochemical impedance study in standard K3[Fe(CN)6] single-electron redox process. Their electrochemical surface areas, electrode surface coverages, and charge transfer resistances were calculated to be 1.46 cm2, 2.338 × 10-5 mol∙cm-2, and 2790 Ω and 5.48 cm2, 2.476 × 10-5 mol∙cm-2, and 1254.65 Ω for CeCPE and CeBCPE, respectively. These fabricated electrodes were used as electrochemical sensors for cadmium ion estimation by optimizing the experimental parameters through differential pulse voltammetry. The optimized conditions included 10% modifier for CeCPE and 5% modifier for CeBCPE in 0.12 M HCl solution of pH 5 as supporting electrolyte at - 1.2 V deposition for 30 s in 0.01 to 10 mg L-1 linear cadmium solution range. Under these conditions, the limit of quantification (LOQ) of 0.368 mg L-1 and 0.005 mg L-1 was calculated for CeCPE and CeBCPE electrodes, respectively. The limit of detection (LOD) was calculated to be 0.121 mg L-1 and 0.002 mg L-1 for CeCPE and CeBCPE, respectively. All the experimental results indicated that electrodes fabricated from CeO2-Cu-BTC show better performance as compared to CeO2-based electrodes. Both these types of electrochemical sensors presented good repeatability and performance in the presence of interfering ions as well. From these findings, it can also be inferred that these electrochemical sensors can provide a simple and very sensitive method for approximation of toxic cadmium ions in aqueous solutions.

Application of Ag nanoparticles decorated on graphene nanosheets for electrochemical sensing of CEA as an important cancer biomarker

In this research, a novel biosensing platform is described based on graphene nano-sheets decorated with Ag nano-particles (GNSs@Ag NPs). The designed electrochemical aptasensor was employed to determine carcinoembryonic antigen (CEA), an important cancer biomarker. Inherently, aptasensing interfaces provide high sensitivity for CEA tumor marker because of the high specific surface area and excellent conductivity of the prepared GNSs@Ag NPs composite. The established assay demonstrated a wide linear range from 0.001 pg/mL to 10 pg/mL with a correlation coefficient of 0.9958 and low detection limit (DL) of 0.5 fg/mL based on S/N = 3 protocol. The derived biosensor illustrated acceptable selectivity towards common interfering species including HER2, VEGF, IgG, MUC1 and CFP10. In addition, the aptsensor showed good reproducibility and fast response time. The applicability of the suggested strategy in human serum samples was also examined and compared to the commercial enzyme-linked immunosorbent assay (ELISA). Based on the experimental data, it was found that the discussed sensing platform can be exerted in the monitoring of CEA in different cancers for early diagnosis.

An efficient pretreatment method based on AgNPs-doped SnO2 photocatalyst for the accurate detection of heavy metals in organic-rich water samples

Humic acid (HA), the primary composition of natural organic matter (NOM) widely distributed in water and soil, can complex with heavy metal ions (HMIs), i.e., Cd(II) and Pb(II) in this study, which deters the accurate detection of HMIs using square wave anodic stripping voltammetry (SWASV). Hence, in this study, an efficient pretreatment method was proposed to restore the electrochemical signal of Cd(II) and Pb(II) by breaking the complexation based on AgNPs-doped SnO2 photocatalyst combined with LP/UV irradiation. Optimization of the key parameters for electrochemical signal restoration including pH for photolysis, AgNPs doping rate, photocatalyst dosage and photolysis time were performed to further elevating the accuracy in the proposed pretreatment method over 96.9% for Cd(II) and Pb(II) in 15 min. The effect of different HA concentrations on SWASV signal of Cd(II) and Pb(II) was also investigated adopting the optimal parameters. Then, the UV-vis absorption spectra, crystal structure, and the morphology of AgNPs-doped SnO2 photocatalyst were investigated to excavate the reasons behind the most excellent AgNPs doping rate to SnO2 in signal restoration. Moreover, the behavior of HA degradation and transformation under LP/UV irradiation was studied to investigate the mechanism of electrochemical signal restoration. Finally, the feasibility of the proposed method was testified by comparing detection results with ICP-MS results using real water samples extracted from aquaculture water.

Recent advances in the modification of electrodes for trace metal analysis: a review

This review paper summarizes the research published in the last five years on using different compounds and/or materials as modifiers for electrodes employed in trace heavy metal analysis. The main groups of modifiers are identified, and their single or combined application on the surface of the electrodes is discussed. Nanomaterials, film-forming substances, and polymers are among the most used compounds employed mainly in the modification of glassy carbon, screen-printed, and carbon paste electrodes. Composites composed of several compounds and/or materials have also found growing interest in the development of modified electrodes. Environmentally friendly substances and natural products (mainly biopolymers and plant extracts) have continued to be included in the modification of electrodes for trace heavy metal analysis. The main analytical performance parameters of the modified electrodes as well as possible interferences affecting the determination of the target analytes, are discussed. Finally, a critical evaluation of the main findings from these studies and an outlook discussing possible improvements in this area of research are presented.

Employing Pd nanoparticles decorated on halloysite nanotube/carbon composite for electrochemical aptasensing of HER2 in breast cancer patients

An effective biosensing platform is described based on halloysite nanotube/carbon composite decorated with Pd nanoparticles (HNT/C@Pd NPs). A novel electrochemical aptasensor was designed using the proposed nano-platform to determine human epidermal growth factor receptor 2 (HER2), a breast cancer biomarker. Inherently, aptasensing interfaces provide high sensitivity and selectivity for tumor markers owing to the high specific surface area of HNT/C and good conductivity stems from deposition of Pd NPs into HNT/C composite. With a correlation coefficient of 0.996, the electrochemical aptasensor demonstrated a wide linear range from 0.03 ng/mL to 9 ng/mL. The limit of detection (LOD) of the established assay was 8 pg/mL based on S/N = 3 method. Further, the designed biosensor demonstrated acceptable selectivity, good reproducibility, and high stability. The applicability of the impedimetric sensor in human serum samples was also examined and compared to enzyme-linked immunosorbent assay (ELISA) assay (p-value >0.05). Based on the results, it was found that the proposed methodology can be used in quantification of breast cancer markers for early diagnosis and treatment.

Photo-assisted "co-movement catalysis": CoFe2O4/CNS heterojunction based portable electrochemical sensor for simultaneous detection of Pb2+ and Cd2+ in natural water

Heavy metal ions (HMIs) seriously threaten human health even under trace conditions. Therefore, accurate, efficient and simultaneous detection of multiple HMIs is of great significance. Here, a strategy of "co-movement catalysis" based on photo-assisted electrochemical catalysis is proposed by constructing a flexible electrochemical sensor with CoFe2O4/CNS heterojunction-modified nickel foam as the working electrode for simultaneous detection of HMIs. Regarding photo-assisted catalysis, CoFe2O4/CNS nanocomposites formed a p-n type heterojunction, effectively separating photo-generated electron-hole pairs and reducing photo-generated carriers' recombination rate, leading to the catalytic reaction of photogenerated electrons and holes with HMIs and atoms to improve the efficiency of preconcentration and stripping, further amplifying the electrochemical signal. Regarding electrochemical catalysis, the CoFe2O4 spinel contains variable valence transition metal ions Fe2+/Fe3+ and Co2+/Co3+, which can reduce and oxidize HMIs circularly, further enhancing the sensor's sensitivity. The portable sensor based on "co-movement catalysis" exhibited sensitive detection performance. The linear range is 0.100-10.0 μM for Pb2+ and 1.00-10.0 μM for Cd2+, with the detection limit of 0.0310 μM for Pb2+ and 0.219 μM for Cd2+, respectively. The recovery rate of the sensor to natural water samples is between 96% and 105%, which proves its development potential in environmental monitoring.

Bimodal interferences of Pb(II) induced by parallel deposition in Pb(II)-Cu(II) electrochemical detections: Voltammetric signals analysis combined with numerical simulations on transient interfacial phenomena

The perplexity of double peaks in Pb(II) detections has been a threat to the reliability of Pb(II) electroanalysis results for a long term. For the complexity of electrode interfaces, rare studies were taken on mechanisms of Pb(II) double peaks through interfacial kinetics. In this work, analyses on experimental signals and interfacial simulations were working together to reveal that the generation of Pb(II) double peaks in Pb(II)-Cu(II) systems is the deposition of Pb(II) on Cu deposits occurring in parallel. By applying anode stripping voltammetry and cyclic voltammetry, a parallel deposition reaction was found to influence the shape of Pb(II) peaks, and the existence of the second peak was controlled through the adjustment of experimental conditions. A kinetic model was built to reveal the interference of electroanalysis signals caused by a parallel deposition reaction and simulations based on the model were combined with experiments to illustrate that double peaks of Pb(II) were caused by the parallel deposition on Cu(II) deposits. This work proposes another insight of Pb(II) double peaks from macroscale kinetics and pays more attention on the dynamic procedure of electroanalysis interfaces, which makes the study on environmental electroanalysis interface phenomena more clear and is enlightening to develop efficient electrical methods for pollutant monitoring.

Impedimetric aptasensor based on MOF based composite for measuring of carcinoembryonic antigen as a tumor biomarker

In this research, gold nanoparticle (GNPs)-modified metal-organic framework/reduced graphene oxide (MOF(801)/rGO) hybrid was employed to design a new aptasensor for carcinoembryonic antigen (CEA) quantification in biological sample. The sensing ability of the electrode for CEA biomarker was examined with electrochemical impedance spectroscopy (EIS) and cyclic voltammetry procedures. Besides, CEA was electrochemically quantified by the EIS method. With respect to the high surface-to-volume ratio of MOF(801) and the good electron transfer ability of rGO, the proposed sensor displayed notable sensitivity and reliability in the CEA analysis. The derived electrode showed an appreciable detection limit of 0.8 pg L-1 using EIS protocol. In addition, the present aptasensor revealed diverse advantages including anti-interference property, wide linear range (0.0025-0.25 ng L-1), convenience and high efficiency toward CEA quantification. More importantly, the performance of the suggested assay remains unchanged in analysis of CEA in body fluids. The established assay demonstrates that the suggested biosensor is a promising device in clinical diagnosis.

Colorimetric sensor based on biogenic nanomaterials for high sensitive detection of hydrogen peroxide and multi-metals

Hydrogen peroxide (H2O2) and heavy metals, which are among the wastes of the industrial sector, become a threat to living things and the environment above certain concentrations. Therefore, the detection of both H2O2 and heavy metals with simple, low-cost, and fast analytical methods has gained great importance. The use of nanoparticles in colorimetric sensor technology for the detection of these analytes provides great advantages. In recent years, green synthesis of nanomaterials with products that can be considered biowaste is among the popular topics. In this study, silver/silver chloride nanoparticles (Ag@AgCl NPs) were synthesized using the green synthesis method as an eco-friendly and cheap method, the green algae extract was used as a reducing agent. The characterization of Ag@AgCl nanoparticles and green algae extract was carried out with several techniques such as Transmission Electron Microscopy (TEM), UV-Visible spectrometry (UV-Vis), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction patterns (XRD) methods were used for characterization. According to TEM analysis, the Ag@AgCl NPs typically spherical in form and range in size from 4 to 10 nm, and UV-vis showed the formation of surface plasmon resonance (SPR) of the Ag@AgCl between 400 and 450 nm. In addition, its activity as a colorimetric sensor for hydrogen peroxide (H2O2) and multi-metal detection was evaluated. Interestingly, Ag/AgCl NPs caused different color formations for 3 metals simultaneously in the sensor study for heavy metal detection, and Fe3+, Cu2+, and Cr6+ ions were detected. The R2 values for H2O2, Fe3+, Cu2+, and Cr6+ were 0.9360, 0.9961, 0.9787, and 0.9625 the limit of detection (LOD) was 43.75, 1.69, 3.18, and 5.05 ppb (ng/mL), respectively. It was determined that Ag@AgCl NPs have the potential to be used as a colorimetric sensor for the detection of H2O2 and heavy metals from wastewater.

A new formulation of Ni/Zn bi-metallic nanocomposite and evaluation of its applications for pollution removal, photocatalytic, electrochemical sensing, and anti-breast cancer

Nanocomposites have gained attention due to their variety of applications in different fields. In this research, we have reported a green synthesis of a bi-metallic nanocomposite of nickel and zinc using an aqueous extract of Citrus sinensis in the presence of chitosan (Ni/Zn@orange/chitosan). The nanocomposite was characterized using different techniques. We have examined various applications for Ni/Zn@orange/chitosan. The NPs were manufactured in spherical morphology with a particle range size of 17.34-90.51 nm. Ni/Zn@orange/chitosan showed an acceptable ability to remove dyes of Congo red and methyl orange from an aqueous solution after 80 min furthermore, it uptaking the drug mefenamic acid from a solution. Ni/Zn@orange/chitosan also exhibited great photocatalytic activity in synthesizing benzimidazole using benzyl alcohol and o-phenylenediamine. Ni/Zn@orange/chitosan was found as a potent electrochemical sensor to determine glucose. In the molecular and cellular section of the current research, the cells with composite nanoparticles were studied by MTT way about the anti-breast adenocarcinoma potentials malignant cell lines. The IC50 of composite nanoparticles were 320, 460, 328, 500, 325, 379, 350, and 396 μg/mL concering RBA, NMU, SK-BR-3, CAMA-1, MCF7, AU565, MDA-MB-468, and Hs 281.T breast adenocarcinoma cell lines, respectively. The results revealed the newly synthesized nanocomposite is a potent photocatalyst, dye pollution removal agent, and an acceptable new drug to treat breast cancer.

Nanohybrid of antimonene@Ti3C2Tx-based electrochemical aptasensor for lead detection

Lead ions (Pb2+), as one of many common heavy metallic environmental pollutants, can cause serious side-effects and result in chronic poisoning to people's health, so it is highly significant to monitor Pb2+ efficiently and sensitively. Here, we proposed an antimonene@Ti3C2Tx nanohybrid-based electrochemical aptamer sensor (aptasensor) for high sensitive Pb2+ determination. The sensing platform of nanohybrid was synthesized by ultrasonication, possessing the advantages of both antimonene and Ti3C2Tx, which not only can vastly enlarge the sensing signal of the proposed aptasensor, but also greatly simplified its manufacturing flow, because antimonene can strongly interact with aptamer through noncovalently bound. The surface morphology and microarchitecture of the nanohybrid were perused by several methods such as scanning electron microscope (SEM), energy-dispersive X-ray mapping spectroscopy (EDS), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and atomic force microscope (AFM). Under optimal empirical conditions, the proposed aptasensor exhibited a wide linear correlation of the current signals with the logarithm of CPb2+ (Log CPb2+) over the span from 1 × 10-12 to 1 × 10-7 M and provided a trace discernment limit of 3.3 × 10-13 M. Moreover, the constructed aptasensor displayed superior repeatability, great consistency, eminent selectivity, and beneficial reproducibility, implying its extreme potential application for water quality control and the environmental monitoring of Pb2+.

A strategy for As(III) determination based on ultrafine gold nanoparticles decorated on magnetic graphene oxide

In this work, a new dendrimer modified magnetic graphene oxide (GO) was used as a substrate for electrodeposition of Au nanoparticles. The modified magnetic electrode was employed for sensitive measuring of As(III) ion as a well-established human carcinogen. The prepared electrochemical device exhibits excellent activity towards As(III) detection using the square wave anodic stripping voltammetry (SWASV) protocol. At optimum conditions (deposition potential at -0.5 V for 100 s in 0.1 M acetate buffer with pH 5.0), a linear range from 1.0 to 125.0 μgL-1 with a low detection limit (calculated by S/N = 3) of 0.47 μg L-1 was obtained. In addition to the simplicity and sensitivity of the proposed sensor, its high selectivity against some major interfering agents, such as Cu(II) and Hg(II) makes it an appreciable sensing tool for the screening of As(III). In addition, the sensor revealed satisfactory results for detection of As(III) in different water samples, and the accuracy of obtained data were confirmed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) setup. Accounting for the high sensitivity, remarkable selectivity and good reproducibility, the established electrochemical strategy has great potential for analysis of As(III) in environmental matrices.

Electrochemical and Optical Sensors for Real-Time Detection of Nitrate in Water

The health and integrity of our water sources are vital for the existence of all forms of life. However, with the growth in population and anthropogenic activities, the quality of water is being impacted globally, particularly due to a widespread problem of nitrate contamination that poses numerous health risks. To address this issue, investigations into various detection methods for the development of in situ real-time monitoring devices have attracted the attention of many researchers. Among the most prominent detection methods are chromatography, colorimetry, electrochemistry, and spectroscopy. While all these methods have their pros and cons, electrochemical and optical methods have emerged as robust and efficient techniques that offer cost-effective, accurate, sensitive, and reliable measurements. This review provides an overview of techniques that are ideal for field-deployable nitrate sensing applications, with an emphasis on electrochemical and optical detection methods. It discusses the underlying principles, recent advances, and various measurement techniques. Additionally, the review explores the current developments in real-time nitrate sensors and discusses the challenges of real-time implementation.

Voltammetric sensing of Cd(II) at ZIF-8/GO modified electrode: Optimization and field measurements

In this work, a metal-organic framework/graphene oxide (MOF(ZIF-8)/GO) nanocomposite was utilized for the electroanalysis of trace level of Cd(II) after modification of a cheap graphite rod electrode (GRE). After closed circuit process on the modified electrode, the differential pulse anodic stripping voltammetry (DPASV) technique was used for measuring of Cd(II). In optimal conditions, the sensor showed a linear dependence of current with concentration range 0.1-30 ppb for Cd(II). Moreover, limit of detection 0.03 ppb were obtained. Besides good selectivity, the sensor also indicated good reproducibility (below 5%). Moreover, the sensor showed satisfactory sensing performance in river, dam and wastewater samples with recovery ranging from 97.2% to 102.4%. Additionally, possible interfering cations were examined, but no significant interference was found. For the detection of trace Cd(II) in real matrices, this sensor illustrated other good merits like high stability, rapidity and simplicity.

Application of Co3O4 nanocrystal/rGO for simultaneous electrochemical detection of cadmium and lead in environmental waters

Sensing of cadmium (Cd) and lead (Pb) in environmental samples is crucial for identifying potential health risks associated with exposure to these heavy metals as well as understanding the extent of heavy metal contamination in different environments and its impact on the ecosystem. The present study elucidates the development of a novel electrochemical sensor that can detect Cd (II) and Pb (II) ions simultaneously. This sensor is fabricated using reduced graphene oxide (rGO) and cobalt oxide nanocrystals (Co₃O₄ nanocrystals/rGO). The characterization of Co₃O₄ nanocrystals/rGO was done by using various analytical techniques. The incorporation of cobalt oxide nanocrystals with intense absorption properties results in an amplification of the electrochemical current generated on the surface of the sensor by heavy metals. This, when coupled with the unique properties of the GO layer, enables the identification of trace levels of Cd (II) and Pb (II) in the surrounding environment. The electrochemical testing parameters were meticulously optimized to obtain high sensitivity and selectivity. The Co₃O₄ nanocrystals/rGO sensor exhibited exceptional performance in detecting Cd (II) and Pb (II) within a concentration range of 0.1-450 ppb. Notably, the limits of detection (LOD) for Pb (II) and Cd (II) were found to be highly impressive at 0.034 ppb and 0.062 ppb, respectively. The Co₃O₄ nanocrystals/rGO sensor integrated with the SWASV method displayed notable resistance to interference and exhibited consistent reproducibility and stability. Therefore, the suggested sensor has the potential to serve as a technique for detecting both ions in aqueous samples using SWASV analysis.

An ultra-sensitive and selective electrochemical sensor based on GOCS composite and ion imprinted polymer for the rapid detection of Cd2+ in food samples

An ultra-sensitive and selective electrochemical sensor was proposed through the combination of carbon disulfide-functionalized graphene oxide (GOCS) composite with high conductivity and cadmium ion-imprinted polymer (IIP). Using pyrrole as the functional monomer and Cd²⁺ as the template ion, the IIP was formed by in situ electropolymerization on GOCS composite. Under the optimized experimental conditions, the sensor exhibited a good linear relationship in the range of 0.5-50 μg/L Cd²⁺ concentration, with the lowest detection limit of 0.23 μg/L. The sensor exhibited not only good selectivity for the determination of Cd²⁺, but also good repeatability with current response remaining 87.6 % after four cycles. Furthermore, the sensor exhibited similar sensing performance in lettuce, orange and peach with recovery ranging from 82.6 % to 110.63 %. This work is expected to provide an electrochemical sensor with excellent selectivity, good stability and sensitivity for the detection of trace amounts of Cd²⁺ in real samples.

Fabrication of S and O-incorporated graphitic carbon nitride linked poly(1,3,4-thiadiazole-2,5-dithiol) film for selective sensing of Hg2+ ions in water, fish, and crab samples

Screen-printed carbon electrodes (SPCE) were modified with sulfur and oxygen-incorporated graphitic carbon nitride (S, O-GCN) linked poly(1,3,4-thiadiazole-2,5-dithiol) film (PTD) through thioester linkage. The promising interaction between the Hg²⁺ and modified materials containing sulfur as well as oxygen through strong affinity was studied. This study was utilized for the electrochemical selective sensing of Hg²⁺ ions by differential pulse anodic stripping voltammetry (DPASV). After, optimizing the different experimental parameters, S, O-GCN@PTD-SPCE was used to improve the electrochemical signal of Hg²⁺ ions and achieved a concentration range of 0.05-390 nM with a detection limit of 13 pM. The real-world application of the electrode was studied in different water, fish, and crab samples and their obtained results were confirmed with Inductive Coupled Plasma - Optical Emission Spectroscopy (ICP-OES) studies. Additionally, this work established a facile and consistent technique for enhancing the electrochemical sensing of Hg²⁺ ions and discusses various promising applications in water and food quality analysis.

Optimization and analytical behavior of a morphine electrochemical sensor in environmental and biological samples based on graphite rod electrode using graphene/Co3O4 nanocomposite

In this research, a new sensor based on graphene/Co₃O₄ (Gr/Co₃O₄) nanocomposite was employed for electrochemically determination of morphine (MOR). The modifier was synthesized with a simple hydrothermal technique and well characterized using X-ray difraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) tools. The modified graphite rod electrode (GRE) was revealed a high electrochemical catalytic activity for the MOR oxidation and employed for the electroanalysis of trace MOR concentration by means of differential pulse voltammetry (DPV) technique. At the optimum experimental factors, the resulting sensor offered a good response for MOR in the concentration range of 0.5-100.0 μM with a detection limit of 80 nM. In addition, the modified electrode demonstrated an acceptable selectivity, stability and reproducibility. This assay was also provided a valid platform for the detection of MOR in environmental and biological samples with acceptable recoveries and RSD in the range of 97.2-102.8% and 1.7-3.4%, respectively. Taking to the simplicity, low cost and short analysis time, this approach is suggested for clinical, environmental and forensic testing of MOR.

Anthocyanin-induced color changes in bacterial cellulose nanofibers for the accurate and selective detection of Cu(II) in water samples

The environment and our health are negatively impacted by heavy metal ions, like Cu(II). The present study developed a green and effective metallochromic sensor that detects copper (Cu(II)) ions in solution and solid state using anthocyanin extract from black eggplant peels embedded in bacterial cellulose nanofibers (BCNF). Cu(II) is quantitatively detected by the sensing method with detection limits between 10-400 ppm and 20-300 ppm in solution and solid state, respectively. In the solution state, we depicted a sensor for Cu(II) ions in aqueous matrices in the pH range from 3.0 to 11.0, with the capability to produce a visual color change from brown to light blue and dark blue depending on the Cu(II) concentration. Additionally, BCNF-ANT film can act as a sensor for Cu(II) ions in the pH range of 4.0-8.0. Neutral pH was selected from the standpoint of high selectivity. It was found that visible color changed when Cu(II) concentration was increased. Bacterial cellulose nanofibers modified with anthocyanin were characterized with ATR-FTIR and FESEM. Various metal ions, including Pb²⁺, Co²⁺, Zn²⁺, Ni²⁺, Al³⁺, Ba²⁺, Hg²⁺, Mg²⁺, and Na⁺, were used to challenge the sensor to determine its selectivity. Anthocyanin solution and BCNF-ANT sheet were employed in the actual tap water sample successfully. The results also clarified that the various foreign ions did not significantly interfere with Cu(II) ions detection at optimum conditions. Compared to previously developed sensors, no electronic components, trained personnel, or sophisticated equipment were needed to apply the colorimetric sensor developed in this research. Cu(II) contamination in food matrices and water can be monitored on-site easily.

Efficient cobalt hydroxide nanosheets for enhanced electrochemical sensing of Hg (II) ion

A sensitive electrochemical device was suggested via the modification of a simple graphite rod electrode (GRE) with cobalt hydroxide (Co(OH)₂) nanosheets. After closed circuit process on the modified electrode, the anodic stripping voltammetry (ASV) technique was used for measuring of Hg(II). In optimal experimental conditions, the suggested assay depicted a linear response over a broad range in the range 0.25-30 μg L^-1, with the lowest detection limit of 0.07 μg L^-1. Besides good selectivity, the sensor also indicated excellent reproducibility with a relative standard deviation (RSD) value of 2.9%. Moreover, the Co(OH)₂-GRE showed satisfactory sensing performance in real water samples with appropriate recovery values (96.0-102.5%). Additionally, possible interfering cations were examined, but no significant interference was found. By taking some merits such high sensitivity, remarkable selectivity and good precision, this strategy is expected to provide an efficient protocol for the electrochemical measuring of toxic Hg(II) in environmental matrices.

Preparation of carbon quantum dots from ionic liquid modified biomass for the detection of Fe3+ and Pd2+ in environmental water

A new type of green carbon quantum dots (ILB-CQDs) was prepared by hydrothermal method using ionic liquid as a modifier and grape skin as carbon source, and was obtained from hydrogen-bonded lattice structure ionic liquid preparation, which makes the CQDs in a ring-like stable structure with a stability period of more than 90 day. There is also the catalytic effect of the ionic liquid on cellulose, which makes the prepared CQDs show good advantages, such as uniform particle size, high quantum yield (26.7%), and very good fluorescence performance. This is a smart material for the selective detection of Fe³⁺ and Pd²⁺. It has a detection limit of 0.001 nM for Fe³⁺ and 0.23 µM for Pd²⁺ in pure water. It has a detection limit of 3.2 nmol/L for Fe³⁺ and 0.36 µmol/L for Pd²⁺ in actual water, both of which meet the requirements of WHO drinking water standards. And there is to achieve more than 90% of water restoration effect.

Three-dimensional porous high boron-nitrogen-doped carbon for the ultrasensitive electrochemical detection of trace heavy metals in food samples

Exposure to even trace amounts of Cd(II) and Pb(II) in food can have serious effects on the human body. Therefore, the development of novel electrochemical sensors that can accurately detect the different toxicity levels of heavy metal ions in food is of great significance. Based on the principle of green chemistry, we propose a new type of boron and nitrogen co-doped carbon (BCN) material derived from a metal-organic framework material and study its synthesis, characterization, and heavy-metal ion detection ability. Under the optimum conditions, the BCN-modified glassy carbon electrode was studied using square-wave anodic stripping voltammetry, which showed good electrochemical responses to Cd(II) and Pb(II), with sensitivities as low as 0.459 and 0.509 μA/μM cm², respectively. The sensor was successfully used to detect Cd(II) and Pb(II) in Beta vulgaris var. cicla L samples, which is consistent with the results obtained using inductively coupled plasma-mass spectrometry. It also has a strong selectivity for complex samples. This study provides a novel approach for the detection of heavy metal ions in food and greatly expands the application of heteroatom-doped metal-free carbon materials in detection platforms.

Facile bio-fabrication of ZnO@AC nanoparticles from chitosan: Characterization, hydrogen generation, and photocatalytic properties

In this work, activated carbon-supported zinc oxide nanoparticles (ZnO@AC NPs) were studied using the thermal synthesis method. The activated carbon-supported zinc oxide catalyst was characterized by UV-Vis spectrometry techniques, Fourier Transform Infrared Spectrophotometer (FTIR), Transmissive electron microscopy (TEM), and X-ray diffraction (XRD) methods. XRD characterization measurements showed that the average size of the crystal NPs was 6.89 nm. According to the TEM analysis results, the nanoparticles' average size was 11.411 nm, and the particles had a spherical structure. The catalytic properties of the synthesized material were determined using the sodium borohydride methanolysis reaction. A kinetic study was performed regarding the effects of temperature, catalyst, and substrate concentration on the methanolysis reaction. Reusability experiments showed that the catalyst had excellent catalytic activity (85%), stability, and selectivity. As a result of the kinetic study, activation energy, enthalpy (ΔH), entropy (ΔS), and hydrogen production rate activation parameters were found to be 42.52 kJ/mol, 39.98 kJ/mol, -181.42 J/mol.K, 1257.69 mL/min. g, respectively. Also, the photocatalytic activity of ZnO@AC NPs was analyzed against Rhodamine B (RhB) dye, and the maximum degradation percentage was observed to be 76% at 120 min. This study aimed to develop the ZnO@AC NPs into an efficient photocatalyst to prevent industrial wastewater pollution and as a catalyst for hydrogen synthesis as an alternative energy source.

A novel phenanthridine and terpyridine based D-π-A fluorescent probe for the ratiometric detection of Cd2+ in environmental water samples and living cells

A "turn-on" Donor-π-Acceptor (D-π-A) containing phenanthridine-functionalized extended π-conjugate terpyridine, 5-(4'-([2,2':6',2''-terpyridin]-4'-yl)-[1,1'-biphenyl]4-yl)7,8,13,14-tetrahydrodibenzo [a, i] phenanthridine (TBTP) was synthesised. It shows strong selectivity for the detection of toxic Cd²⁺ without interference from other metal ions. In the presence of Cd²⁺, the absorption of the TBTP changes dramatically along with the fluorescent emission with the large Stokes shift of 6300 cm^-1. When the compound TBTP is exposed to UV light, its colour changes from blue to orange over the addition of Cd²⁺. Adding other transition metal ions has no effect. This is based on the mechanism of intramolecular charge transfer. The detection limit for Cd²⁺ was found to be around 1.181 × 10^-8 M. An investigation of the sensing mechanism includes job plot, NMR titration, DFT calculation, and HRMS analyses. Excitingly, the recognition of Cd²⁺ in CH₃CN: H₂O (8:2, v/v) medium is quantitative without interference from Zn^2+, which is a common interferent for Cd²⁺. Furthermore, the probe was used for detecting Cd²⁺ in real water samples and cell imaging in living cells was also performed.

Simple high-temperature annealing affords commercial carbon cloth with enhanced electrochemical performance for highly sensitive detection of imidacloprid

Imidacloprid (IDP) residue in modern agricultural production seriously endangers human health and environmental safety. The establishment of a rapid and efficient method for the detection of IDP residue can effectively prevent its harm to human health. Herein, we demonstrate the carbon cloth (CC) prepared by a high-temperature annealing strategy possesses enhanced electrochemical performance, which could be directly used in electrochemical IDP sensing. Annealed carbon cloth (ACC) is endowed with higher defects, rougher surfaces, more functional groups, more hydrophilic surface, and increased ion-accessible surface area. Furthermore, the ACC electrode shows superior electrocatalytic reduction activity towards IDP, possessing a wide linear range of 5-100 μM, a low detection limit of 0.04 μM, and high sensitivity of 35.58 μA mM^-1 cm^-2. Meanwhile, this sensor can be applied for sensing IDP in grapes and apples with a good recovery of 96.8-104.1%. Compared with other modified electrodes, the ACC electrode has the advantages of no binder, no complicated modification, excellent detection effect, low cost, and easy large-scale production. Consequently, this work designs a self-supporting metal-free electrode with high electrochemical performance, providing a new idea for the development of environmentally friendly IDP sensors.

Carbon-supported X-manganate (XNi, Zn, and Cu) nanocomposites for sensitive electrochemical detection of trace heavy metal ions

Heavy metal ion pollution has always been a stringent problem facing the global environment. Therefore, the detection of heavy metal ions has been extremely important and challenging. An efficient and simple method for the preparation of carbon-supported X-manganate (XNi, Zn, and Cu) nanocomposites was explored for the individual and simultaneous electrochemical detection of Pb(II) and Hg(II). The metallic salt solutions were mixed with graphene to form the precursors through a hydrothermal reaction, and calcined in the air to obtain the final products. The structure and morphology of the synthesized NiMn₂O₄-graphene (NMO-GR), ZnMn₂O₄-graphene (ZMO-GR), and CuMn₂O₄-graphene (CMO-GR) nanocomposites were characterized by various methods, and NMO-GR showed more excellent electrochemical performances by square wave anodic stripping voltammetry (SWASV) than ZMO-GR and CMO-GR. NMO-GR provided a large specific surface area, abundant reaction sites, and good electrical conductivity, thereby enhancing its electrochemical performance. The electrochemical sensor based on NMO-GR displayed the widest linear ranges (1.4-7.7 μM for Pb(II) and 0.7-6.7 μM for Hg(II)) and with the lowest detection limits (0.050 μM for Pb(II) and 0.027 μM for Hg(II)) than ZMO-GR and CMO-GR. This study offered a new way to simultaneously detect Pb(II) and Hg(II), and greatly expanded its application in the field of electrochemistry.

A review on magnetic sensors for monitoring of hazardous pollutants in water resources

Water resources have long been of interest to humans and have become a serious issue in all aspects of human life. The disposal of hazardous pollutants in water resources is one of the biggest global concerns and poses many risks to human health and aquatic life. Therefore, the control of hazardous pollutants in water resources plays an important role, when it comes to evaluating water quality. Due to low toxicity, good electrical conductivity, facile functionalization, and easy preparation, magnetic materials have become a good alternative in recent years to control hazardous pollutants in water resources. In the present study, the idea of using magnetic sensors in controlling and monitoring of pharmaceuticals, pesticides, heavy metals, and organic pollutants have been reviewed. The water pollutants in drinking water, groundwater, surface water, and seawater have been discussed. The toxicology of water hazardous pollutants has also been reviewed. Then, the magnetic materials were discussed as sensors for controlling and monitoring pollutants. Finally, future remarks and perspectives on magnetic nanosensors for controlling hazardous pollutants in water resources and environmental applications were explained.