Detection Of Heavy Metals Research Articles

Enzyme-Programmed Self-Assembly of Nanoparticles.

Nanoparticles are a hot topic in the field of nanomaterial research due to their excellent physical and chemical properties. In recent years, DNA-directed nanoparticle self-assembly technology has been widely applied to the development of numerous complex nanoparticle superstructures. Due to the inherent stability and surface electric repulsion of nanoparticles, it is difficult to make nanoparticle superstructures respond to molecular signals in the external environment. In fact, enzyme-programmed molecular systems are developed to allow diverse functions, including logical operations, signal amplification, and dynamic assembly control. Therefore, combining enzyme-controlled DNA systems may endow nanoparticle assembly systems with more flexibility in program design, allowing them to respond to a variety of external signals. In this review, we summarize the basic principles of enzyme-controlled DNA/nanoparticle self-assembly and introduce its applications in heavy metal detection, gene expression, proteins inside living cells, cancer cell therapy, and drug delivery. With the continuous development of new nanoparticle materials and the increasing functionality of enzyme DNA circuits, enzyme-directed DNA/nanoparticle self-assembled probe technology is expected to see significant future development.

Eco-friendly and sustainable synthesis of carbon quantum dots from waste sulfuric acid of alkylation

Waste sulfuric acid of alkylation (WSAA) poses a challenge in industrial alkylation oil production due to its substantial yield and high treatment costs. This study introduces a novel hydrothermal method that ingeniously couples the treatment of WSAA with the synthesis of high-quality carbon quantum dots (CQDs), offering a cost-effective and controllable approach. Through this method, the particle size and surface functional groups of the resulting CQDs can be precisely regulated. The average particle size tunes from 17.97 nm to 2.42 nm via increasing the hydrothermal temperature, and nitrogen-containing groups can be introduced through adding nitrogen sources during hydrothermal process. The prepared CQDs exhibit notable performance in photocatalysis and heavy metal detection, such as CQDs modified graphite carbon nitride has improved photocatalytic degradation ability and Hg (II) detection ability. Additionally, the environmental impact of the proposed method is substantially minimized, demonstrating a smaller footprint on ecosystems compared to conventional industrial disposal processes. Moreover, the economic cost associated with the method is significantly reduced by approximately 48.4 %, further highlighting its efficiency. Utilizing WSAA as a raw material for CQDs not only facilitates the recycling and sustainable utilization of waste but also enables low-cost production of high-performance carbon materials, presenting a mutually beneficial approach.

First-Principles Insights into Highly Sensitive and Reusable MoS2 Monolayers for Heavy Metal Detection.

This study explores the potential of MoS2 monolayers as heavy metal sensors for As, Cd, Hg, and Pb using density functional theory (DFT) and Non-Equilibrium Green's Function (NEGF) simulations. Our findings reveal that As and Pb adsorption significantly alters the surface structure and electronic properties of MoS2, introducing impurity levels and reducing the band gap. Conversely, Cd and Hg exhibit weaker interactions with the MoS2 surface. The MoS2 monolayer sensors demonstrate exceptional sensitivity for all four target heavy metals, with values reaching 126,452.28% for As, 1862.67% for Cd, 427.71% for Hg, and 83,438.90% for Pb. Additionally, the sensors demonstrate selectivity for As and Pb through distinct response peaks at specific bias voltages. As and Pb adsorption also induces magnetism in the MoS2 system, potentially enabling magnetic sensing applications. The MoS2 monolayer's moderate adsorption energy facilitates rapid sensor recovery at room temperature for As, Hg, and Cd. Notably, Pb recovery time can be significantly reduced at elevated temperatures, highlighting the reusability of the sensor. These results underscore the potential of MoS2 monolayers as highly sensitive, selective, and regenerable sensors for real-time heavy metal detection.

Hydrogen-bond organic-framework-based electrochemical sensor for highly sensitive determination of trace cadmium ions in environmental and e-cigarette samples

BackgroundThe heavy metal ion Cd2+ is acutely toxic, and excessive concentrations can have adverse effects on human production and life, and even lead to significant public health risks and environmental impacts. There are several mature non-electrochemical methods for heavy metal detection, but these methods are characterized by high cost, which makes it difficult to be applied to the field for timely detection. Therefore, it is necessary to prepare a new electrochemical sensor that is environmentally friendly and capable of detecting Cd2+ in the environment quickly, easily and sensitively. ResultsIn this study, hydrogen-bonded organic frameworks (HOFs) were synthesized by a simple hydrothermal reaction. The prepared materials consisted of only C, N and O and had a thin lamellar structure. The HOFs were integrated into a novel electrochemical sensor to achieve accurate detection of Cd2+ ions in real aqueous environments by square wave anodic dissolution voltammetry. The sensor has a wide linear range and a detection limit as low as 0.13 μg/L. Several real water samples, such as tap water, lake water, and e-cigarette digest, were analyzed to simulate the working environment of the sensor, and the results showed that the recoveries of Cd2+ ranged from 95.75 % to 101.2 %. SignificanceWe pioneered the detection of heavy metal ions Cd2+ in e-cigarette digestate samples with the innovative use of HOFs as the sensor material, which demonstrated the potential application in electrochemical sensing with extremely low background current value and high sensitivity, providing new ideas for environmental monitoring and public health control.

Raw clay material-based modified carbon paste electrodes for sensitive heavy metal detection in drinking water

A new electrode based on carbon paste (CP) modified with natural clay was used for heavy metals detection. The investigation of the raw clay material (X-ray diffraction, infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, thermal analysis and particle size distribution) revealed different morpho-structural properties of the natural material. The electrochemical behaviour of the modified carbon paste electrode and its ability to detect heavy metals (Zn2+, Cd2+, and Cu2+) was studied by different electrochemical techniques like cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and square wave anodic stripping voltammetry (SWASV). Both electrochemical and analytical parameters of the investigated modified electrode recommend them as stable, sensitive and reproducible sensors for individual heavy metals detection.

New insight into multi-functional MOG@COP/SA beads for co-adsorption and mono-detection in CTC-Cr(Ⅵ) co-contamination system and efficient anti-counterfeiting

Co-contamination of antibiotics and heavy metals in water environment has provoked considerable toxicological concerns. Meantime, residue detection of heavy metals as well as national anti-counterfeiting safety also have driven attempts in wastewater treatment. In this paper, a core–shell hybrid MOG@COP is designed with behaviors superior to pristine components by combining a Zr-based metal–organic gel and a guanidine-based covalent organic polymer, for co-adsorption and mono-detection in chlortetracycline hydrochloride (CTC)-Cr(Ⅵ) co-contamination system and efficient anti-counterfeiting. In single/binary system, the adsorption capacities of CTC and Cr(Ⅵ) behave as 133.69 and 63.45 mg·g−1/181.82 and 64.47 mg·g−1, and the high sensitivity and low detection limit of Cr(Ⅵ) render as 1.46*105 M−1 and 0.20 μM/1.49*102 M−1 and 0.63 mM, respectively. In addition, to solve the powder shortcomings of easy agglomeration and difficult recycling, MOG@COP is fixed into sodium alginate (SA) matrix to fabricate MOG@COP/SA beads, yielding reinforced adsorption performance of CTC/Cr(Ⅵ) in both single system (152.91/92.25 mg·g−1) and binary system (174.83/75.30 mg·g−1). More importantly, a self-constructed adsorption-detection-anti-counterfeiting (ADA) platform is ingeniously developed with the MOG@COP/SA beads as the backfills for continuously processing CTC-Cr(Ⅵ) co-contaminated water, realizing real-time visualization of Cr(Ⅵ) adsorption process and optical anti-counterfeiting protection. In conclusion, this work is expected to not only trigger the reasonable design of the core–shell hybrid MOG@COP/SA beads with versatile performances of simultaneous luminescence monitor, capture and anti-counterfeiting, but also allow the original exploration for all-in-one platform.

Fingerprinting DNAzyme Cross-Reactivity for Pattern-Based Detection of Heavy Metals.

Heavy metal contamination in food and water is a major public health concern because heavy metals are toxic in minute amounts. DNAzyme sensors are emerging as a promising tool for rapid onsite detection of heavy metals, which can aid in minimizing exposure. However, DNAzyme activity toward its target metal is not absolute and has cross-reactivity with similar metals, which is a major challenge in the wide-scale application of DNAzyme sensors for environmental monitoring. To address this, we constructed a four DNAzyme array (17E, GR-5, EtNA, and NaA43) and used a pattern-based readout to improve sensor accuracy. We measured cross-reactivity between three metal cofactors (Pb2+, Ca2+, and Na+) and common interferents (Mg2+, Zn2+, Mn2+, UO22+, Li+, K+, and Ag+) and then used t-SNE analysis to identify and quantify the metal ion. We further showed that this method can be used for distinguishing mixtures of metals and detecting Pb2+ in environmental soil samples at micromolar concentrations.

Green modified electrode for sensitive simultaneous heavy metal ions electrodetection

The detection of heavy metals (HM) is of particular importance in terms of human health and environmental protection. Electrochemical sensors are usually limited by the interference of various cations that coexist in real samples. These shortcomings are usually solved by incorporating various particles into the electrode material, which represents another source of pollution, thus being unsustainable. In this study, it was demonstrated that the new investigated natural clay (nc), used without processing, and immobilized with chitosan (Chi) matrix on the surface of a GCE in order to obtain nc-Chi/GCE modified electrode can detect, separately and simultaneously, four heavy metals (i.e. Zn2+, Cd2+, Pb2+ and Cu2+). The electrochemical behavior of the new eco-friendly modified electrode and its capacity to detect heavy metals has been investigated by electrochemical impedance spectroscopy (EIS) and square wave anodic stripping voltammetry (SWASV). The obtained electroanalytical performances (i.e., a detection limit of 43.1 nM for Zn2+, 19.1 nM for Cd2+, 4.3 nM for Pb2+ and 57.3 nM for Cu2+) corroborated with the reproducibility and stability of the modified electrode successfully recommends it as a suited device for heavy metals ions detection. The nc-Chi/GCE modified electrode was validated by measurements performed in real samples of tap water.

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.

Simultaneous determination of lead and cadmium in water by metal oxide framework complex-modified glassy carbon electrodes

Lead (Pb) and cadmium (Cd) are pervasive environmental pollutants known for their significant biological toxicity. The traditional methods for detecting these ions often necessitate large-scale instruments and complex procedures. In contrast, electrochemical detection methods offer advantages such as rapidity, portability, and sensitivity, making them suitable for the simultaneous detection of heavy metals. Metal-organic frameworks (MOFs), characterized by their exceptional adsorption and enrichment capabilities for heavy metal ions, have shown promise in this regard. Nevertheless, the poor conductivity of most MOFs has limited their electrochemical applications. In this study, glassy carbon electrodes (GCEs) were modified using the MOF ZIF-8, in combination with a bismuth complex and carboxylated multi-walled carbon nanotubes, resulting in the fabrication of Bi@ZIF-8/CMWCNTs/GCE electrochemical sensors. Leveraging the porous nature and large specific surface area of ZIF-8, the lead and cadmium ion adsorption by bismuth akin to mercury, and the conductivity of carboxylated multi-walled carbon nanotubes, the sensor developed in this study exhibits excellent capability for simultaneous detection of lead and cadmium ions in water. Under optimized conditions, Pb2+ and Cd2+ showed good linear relationships with the peak current in the concentration range of 2.0–50.0 μg/L. In the concentration range studied, the regression equations for Pb2+ and Cd2+ were determined as follows: y = 0.2982x + 0.4553 (r = 0.9962) for Pb2+ and y = 0.3631x + 0.1242 (r = 0.9949) for Cd2+. The detection limits for Pb2+ and Cd2+ were 0.76 μg/L and 0.87 μg/L, respectively. The relative standard deviations (RSDs) for 50 μg/L mixed standard solution of Pb and Cd were 1.89 % and 1.23 %, respectively. Furthermore, the RSDs for the same modified electrode tested with 50 μg/L Pb2+ and Cd2+ mixed standard solution over seven consecutive days were 2.27 % and 1.42 %, respectively, under identical conditions. In practice, the lead and cadmium concentrations of a lake were found to range from 4.42 μg/L to 5.60 μg/L, while the lead and cadmium concentrations of effluent from a wastewater plant ranged from 11.83 μg/L to 14.49 μg/L. This research not only describes a new electrochemical platform for the simultaneous determination of lead and cadmium in water but also provides a new method for the simultaneous determination of lead and cadmium in water. This research is valuable for promoting the application of MOFs in the field of electrochemistry.

The Diversity of MOF Structures and Their Impact on Photoelectrochemical Sensors for Monitoring Environmental Pollution

The problem of environmental pollution is one of the most important in the modern world. Pollution causes an increase in human diseases, the extinction of many species of plants and animals, global warming, and many weather anomalies. One of the great challenges for scientists is the development of methods for monitoring and removing the emerging pollutants. This review focuses on Metal–Organic Frameworks (MOFs) and their use as working material to construct different types of sensors for application in environmental pollution monitoring. In particular, the detection of heavy metals (mercury, lead, and arsenic) and organic compounds (drugs, biomolecules, and pesticides) are considered. The collected data show that photoelectrochemical (PEC) sensors based on MOFs are the most fascinating materials due to various combinations (e.g., surface modification) and operational possibilities. PEC sensors achieve enormous sensitivity, which increases even to the pico level, making it the best tool in sensing applications. This review also highlights the main sensor challenges. Most of them are concerned with the possibility of reusing the sensor, its regeneration, and safe disposal. In addition, more attention should be paid to the sensor manufacturing process, which often uses toxic compounds, and research to eliminate them in favor of non-toxic compounds.

Quantitative and qualitative detection of target heavy metals using anti-interference colorimetric sensor Array combined with near-infrared spectroscopy

An anti-interference colorimetric sensor array (CSA) technique was developed for the qualitative and quantitative detection of target heavy metals in corn oil. This method involves a binding mechanism that triggers changes in atomic energy levels and visible color changes. A custom-built olfactory visualization device was employed to gather spectral data, revealing distinct CSA color difference patterns. Subsequently, three pattern recognition algorithms were used to create an identification model for the target heavy metals. The results showed that the ACO-KNN (Ant Colony Optimization-K-Nearest Neighbor) model outperformed the other models, achieving accuracy rates of 90.28% and 89.58% for the calibration and prediction sets, respectively. The ACO-PLS (Partial Least Square) model was more stable with the lowest root mean square error of prediction (RMSEP), which were 0.1730 and 0.1180, respectively. The limit of detection (LOD) and quantification (LOQ) of Pb and Hg were (0.3, 0.6, 1.1 and 2.2) x 10−3 mg/L, respectively.

Detection and effects of heavy metals in fish blood, water, sediment, food, and plants of different three farms in EL-Fayoum Governorate, Egypt

Detection and effects of heavy metals in fish blood, water, sediment, food, and plants of different three farms in EL-Fayoum Governorate, Egypt

Solid-State Fluorescent Organic Polymers for Visual Detection and Elimination of Heavy Metals in Water.

Selective sensing and removal of toxic heavy metals from water are highly essential since their presence poses significant health and environmental hazards. Herein, we designed and synthesized a novel fluorescent nonconjugated organic polymer by strategically incorporating two key functional groups, namely, a dansyl fluorophore and dithiocarbamate (DTC). Different characterization techniques, including 1H nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDAX), Fourier transform infrared (FTIR), and fluorescence spectroscopy, were performed to understand its structure and material properties. The quantum yield of 4.72% and its solid-state fluorescence indicate that it has potential for various applications in several technological and scientific domains. In this study, we investigated a specific application involving the detection and elimination of heavy metals from water. Interestingly, the presence of dansyl and DTC moieties demonstrated remarkable selectivity toward Cu2+, Co2+, Ni2+, Fe3+, and Fe2+ sensing, displaying distinct color changes specific to each metal. Cu2+ resulted in a yellow color, Co2+ showed a green color, Ni2+ displayed a pale yellowish-green color, and Fe2+/Fe3+ exhibited a brown color. The LOD (limit of detection) for each metal was obtained in the nanomolar range by using a fluorescence spectrometer and the micromolar range from UV-visible spectra: 13.27 nM and 0.518 μM for Cu2+, 8.27 nM and 0.581 μM for Co2+, 14.36 nM and 0.140 μM for Ni2+, 14.95 nM and 0.174 μM for Fe2+, and 15.54 nM and 0.33 μM for Fe3+. Moreover, the DTC functionality on its backbone facilitates effective interaction with the aforementioned heavy metals, subsequently removing them from water (except Fe2+ and Fe3+), validating its dual functionality as both an indicator and a purifier for heavy metals in water. The polymer exhibited a maximum adsorption capacity of 192.30 mg/g for Cu2+, 159.74 mg/g for Co2+, and 181.81 mg/g for Ni2+. Furthermore, this approach exhibits versatility in crafting fluorescent polymers with adjustable attributes that are suitable for a wide range of applications.

Cu@MOF core-shell aerogel: High enzyme-like activity for ultratrace colorimetric detection of Hg2+ ions

Achieving highly sensitive and selective detection of trace-level heavy metals while maintaining high portability and simplicity remains an intractable challenge. Herein, we report an efficient nanozyme-based colorimetric assay for Hg2+ ion analysis based on a facile design of Cu-based metal@MOF core-shell (Cu@MOF) aerogel. The Cu@MOF aerogel exhibits both aerogel properties (i.e., high porosity and large surface area) and core-shell features (i.e., metal-MOF interfaces). These features largely improve its peroxidase-like activity with a catalytic constant (Kcat) of 4.29×106 s−1, far surpassing the efficiency of both pure Cu aerogel and Cu-MOFs. The superior structure facilitates Hg-triggered amalgam at the metal-MOF interfaces upon exposure to Hg2+ ions, which readily improves the peroxidase-like activity. Consequently, a highly sensitive and selective colorimetric assay has been developed for Hg2+ analysis with a detection range of 10–3000 ng·L−1 and a detection limit as low as 9.33 ng·L−1. Furthermore, high portability and simplicity has been achieved by translating this assay into a flexible and affordable test strip by depositing the as-obtained Cu@MOF aerogel on filter paper. This work not only enables an accurate and convenient analysis of heavy metal ions, but also offers a novel direction for the development of cost-effective nanozyme assays.

Enhanced photocatalytic Cr(VI) degradation and real-time detection using dual-fluorescent quantum dot-infused polysulfone microspheres

Conventional methodologies for the detection and remediation of hexavalent chromium (Cr(VI)) are characterized by their complexity and financial burden, necessitating the pursuit of methodologies that are both efficacious and economical, with minimal environmental impact. Within this investigation, we report the fabrication of hollow polysulfone (PSF) microspheres, imbued with bifluorescent quantum dots and metal-organic frameworks, utilizing a Pickering emulsion paradigm to facilitate photolytic Cr(VI) degradation and consistent visual detection. Our results reveal that these engineered microspheres sustain an exceptional degradation efficiency exceeding 98 % for Cr(VI) over quintuple cycles, devoid of agitation, alongside pronounced fluorescence quenching indicative of a durable and recyclable sensing modality. The inherent low density and vacuous architecture of these spheres afford them buoyancy, augmenting their interaction with aqueous pollutants. Furthermore, the material exhibits a distinguished selectivity for Cr(VI), markedly eclipsing alternative metal ions in fluorescence suppression assays, validating its efficacy for heavy metal detection. The dual-functional attributes, coupled with their enduring stability and eco-friendly profile, position the CCUP microspheres at the forefront of water treatment innovation, potentially revolutionizing the real-time tracing of heavy metal pollutants.

Swift detection of heavy metals in water by encoded graphene–gold-metasurface sensor

Swift detection of heavy metals in water by encoded graphene–gold-metasurface sensor

Detection of available heavy metals in soil using gold nanoparticles-modified ion exchange membrane with laser-induced breakdown spectroscopy

The available heavy metals in soil can directly threaten food security and human health. However, traditional detection methods are often complicated and time-consuming. In this study, a novel method with nanoparticles-modified ion exchange membrane with laser-induced breakdown spectroscopy (NMIEM-LIBS) was proposed for the sensitive detection of available heavy metals in soil samples. Gold nanoparticles modified-ion exchange membrane was used to high-efficiency enrich lead (Pb) and cadmium (Cd) ions in soil solution and detected after separation. This method can realize the highly sensitive quantitative analysis of available Pb and Cd in soil, with the detection limits (LoDs) of 2.62 mg/kg and 0.24 mg/kg, respectively. Furthermore, the method was successfully applied to detect available Pb and Cd concentrations in three spiked soil samples, with recoveries of 87.02–115.79 % and 82.45–114.81 %, respectively. The developed method can provide a simple, rapid, and sensitive strategy for monitoring available heavy metals in environmental samples.

Simultaneous Hg2+ and Pb2+ detection in water samples using an electrochemical aptasensor with dual signal amplification by exonuclease III and metal-organic frameworks

Heavy metal pollution in the environment has become a significant global concern due to its detrimental effects on human health and the environment. In this study, we report an electrochemical aptasensor for the simultaneous detection of Hg2+ and Pb2+. Gold nanoflower/polyethyleneimine-reduced graphene oxide (AuNFs/PEI-rGO) was introduced on the surface of a gold electrode to improve sensing performance. The aptasensor is based on the formation of a T-Hg2+-T mismatch structure and specific cleavage of the Pb2+-dependent DNAzyme, resulting in a dual signal generated by the Exo III specific digestion of methylene blue (MB) labeled at the 3′ end of probe DNA-1 and the reduction of the substrate ascorbic acid (AA) catalyzed by the signal label. The decrease of MB signal and the increase of AA oxidation peak was used to indicate the content of Hg2+ and Pb2+, respectively, with detection limits of 0.11 pM (Hg2+) and 0.093 pM (Pb2+). The aptasensor was also used for detecting Hg2+ and Pb2+ in water samples with good recoveries. Overall, this electrochemical aptasensor shows promising potential for sensitive and selective detection of heavy metals in environmental samples.

Heavy Metal Detection and Removal by Composite Carbon Quantum Dots/Ionomer Membranes.

The combination of ion exchange membranes with carbon quantum dots (CQDs) is a promising field that could lead to significant advances in water treatment. Composite membranes formed by sulfonated poly(ether ether ketone) (SPEEK) with embedded CQDs were used for the detection and removal of heavy metal ions, such as lead and cadmium, from water. SPEEK is responsible for the capture of heavy metals based on the cation exchange mechanism, while CQDs detect their contamination by exhibiting changes in fluorescence. Water-insoluble "red" carbon quantum dots (rCQDs) were synthesized from p-phenylenediamine so that their photoluminescence was shifted from that of the polymer matrix. CQDs and the composites were characterized by several techniques: FTIR, Raman, UV/VIS, photoluminescence, XPS spectroscopies, and AFM microscopy. The heavy metal ion concentration was analyzed by inductively coupled plasma-optical emission spectroscopy (ICP-OES). The concentration ranges were 10.8-0.1 mM for Pb2+ and 10.0-0.27 mM for Cd2+. SPEEK/rCQDs showed a more pronounced turn-off effect for lead. The composite achieved 100% removal efficiency for lead and cadmium when the concentration was below a half of the ion exchange capacity of SPEEK. The regeneration of membranes in 1 M NaCl was also studied. A second order law was effective to describe the kinetics of the process.