Detection Of Heavy Metal Ions Research Articles

Green Synthesis of Biomass‐Based Fluorescent Carbon Dots for the detection and adsorption of Fe (III)

AbstractFluorescent carbon dots (CDs) derived from natural biomass have attracted considerable attention due to the superior characteristics of low‐cost, large‐scale, renewability, and excellent biocompatibility. In this work, novel orange‐red fluorescent carbon dots (N‐CDs) were successfully designed and prepared via hydrothermal method by using Peony seed residue and o‐phenylenediamine as precursors. The obtained N‐CDs exhibited good aqueous solubility, outstanding fluorescence properties, and high photostability. Moreover, the fluorescence intensity of N‐CDs at 594 nm exhibited a linear change towards Fe3+ in the range of 0.0–50.0 μM, and the detection limit was 20 nM. For fast and efficient Fe3+ sensing, two kinds of solid‐phase fluorogenic test strips and nanofibrous film composited with N‐CDs were fabricated. Furthermore, solid phase materials composited PVDF with N‐CDs (N‐CDs@PVDF) demonstrated outstanding properties in simultaneous Fe3+ adsorption and detection, providing an integrative solution for the detection and decontamination of heavy metal ions

Multiple fluorescence polymer dots-based differential array sensors for highly efficient heavy metal ions detection

Water pollution caused by harmful heavy metal ions (HMIs) can significantly impact aquatic ecosystems and pose a high risk to human health. In this work, equipped with ultra-high fluorescence brightness, efficient energy transfer, and environmentally friendly performance, polymer dots (Pdots) were employed to construct a pattern recognition fluorescent HMIs detection platform. A single-channel unary Pdots differential sensing array was first developed to identify multiple HMIs with 100% classification accuracy. Then an "all-in-one" multiple Förster resonance energy transfer (FRET) Pdots differential sensing platform was constructed to discriminate HMIs in the artificial polluted water samples and actual water samples, exhibiting high classification accuracy in distinguishing HMIs. The proposed strategy leverages the compounded cumulative differential variation of diverse sensing channels for analytes, which is anticipated to find extensive applications in other fields for detection purposes.

Computational Studies and Fluorescent Turn‐off Sensing of Biologically Important Cu2+ Ion in Irrigation Water by Schiff Base

AbstractNumerous chemosensors have been reported for the detection of heavy metal ions in drinking water or in biological system pertaining to health concerns. Here, in the present study we have focused on synthesis of simple, efficient chemosensors for one of such ion i. e. Cu2+ due to its prevalent importance. Chemosensor (3) has been synthesized from sulfanilamide and nitro‐benzaldehyde which was further characterized with various analyses such as 1H NMR, 13C NMR, FT‐IR and mass spectrometry. The absorbance and emission studies results showed that sensor (3) has profound sensitivity and selectivity for Cu2+ ions in aqueous medium by quenching the emission intensity of the same at 335 nm. Whereas the complexation of sensor (3) with Cu2+ ion produced the change in color from pale yellow to green, in semi aqueous medium with gradual addition of Cu2+. The sensor was also tested against various water samples and found to generate 100.4 % recovery from irrigation water sample. Further computational analyses were performed to verify the sensing mechanism and also different global quantities such as electron affinity (A), ionisation potential (I), electronegativity (χ), global softness (S), hardness (η), and electrophilicity (ψ) were calculated.

Recent Aptamer-Based Biosensors for Cd2+ Detection.

Cd2+, a major environmental pollutant, is heavily toxic to human health. Many traditional techniques are high-cost and complicated; thus, developing a simple, sensitive, convenient, and cheap monitoring approach is necessary. The aptamer can be obtained from a novel method called SELEX, which is widely used as a DNA biosensor for its easy acquisition and high affinity of the target, especially for heavy metal ions detection, such as Cd2+. In recent years, highly stable Cd2+ aptamer oligonucleotides (CAOs) were observed, and electrochemical, fluorescent, and colorimetric biosensors based on aptamers have been designed to monitor Cd2+. In addition, the monitoring sensitivity of aptamer-based biosensors is improved with signal amplification mechanisms such as hybridization chain reactions and enzyme-free methods. This paper reviews approaches to building biosensors for inspecting Cd2+ by electrochemical, fluorescent, and colorimetric methods. Finally, many practical applications of sensors and their implications for humans and the environment are discussed.

Electrochemical sensor based on Bi/Bi2O3 doped porous carbon composite derived from Bi-MOFs for Pb2+ sensitive detection

It is of great significance to develop electrochemical sensors based on novel functional nanomaterials for heavy metal ions detection. In this work, a novel Bi/Bi2O3 co-doped porous carbon composite (Bi/Bi2O3@C) was prepared by simple carbonization of bismuth-based metal-organic frameworks (Bi-MOFs). The micromorphology, internal structure, crystal and elemental composition, specific surface area and porous structure of the composite were characterized by SEM, TEM, XRD, XPS, and BET. Further, a sensitive electrochemical sensor for Pb2+ detection was constructed by modifying Bi/Bi2O3@C on the surface of the glassy carbon electrode (GCE) based on the square wave anodic stripping voltammetric (SWASV). The different factors affecting the analytical performance were optimized systematically, such as material modification concentration, deposition time, deposition potential, and pH value. Under optimized conditions, the proposed sensor exhibited a wide linear range from 37.5nM to 2.0μM with a low detection limit of 6.3nM. Meanwhile, the proposed sensor showed good stability, acceptable reproducibility, and satisfactory selectivity. The reliability of the as-proposed sensor was confirmed by the ICP-MS method for Pb2+ detection in different samples.

L-Cysteine functionalized coral-like Ag doped MnO2 nanostructures for the real-time electrochemical detection of lead and cadmium ions

In this report, L-Cysteine functionalized Ag@MnO2 nanocomposite was prepared for selective, rapid, and instantaneous electrochemical sensing of heavy metal ions (HMIs). Hydrothermal method was employed to synthesize L-Cysteine functionalized Ag@MnO2 nanocomposites. The composition and morphology of L-Cys/Ag@MnO2 were characterized by advanced techniques such as XRD, FTIR, UV-Vis and FESEM analysis. XRD spectra confirmed the synthesis of tetragonal L-Cys/Ag@MnO2, while FESEM confirmed the formation of coral like nanostructures. Coral like L-Cys/Ag@MnO2 with sufficient open pores provided high surface area and large number of active sites for sensing of HMIs. The electrochemical parameters were optimized i.e., pH effect, deposition potential, deposition time, and impact of interfering species to enhance HMIs detection. Under optimized conditions, the designed sensor exhibited high sensitivity towards the solution of both Cd+2 and Pb+2 ions over a wide range from 0.1 μM to 0.005 μM of Cd+2 and Pb+2, respectively with LOD = 0.052 nM for Pb+2 and 0.065 nM for Cd+2. The developed sensor's practical applicability was also tested in tap water. Due to the high conductivity, synergistic effect, and high electron transfer kinetics of the prepared material, as designed sensor can be utilized for sensing other toxic metal ions in real samples.

A pH-mediated field amplification sample stacking technique based on portable microchip electrophoresis heavy metal ion detection system.

We built a portable microchip electrophoresis heavy metal ion detection system and proposed a pH-mediated field amplified sample stacking (pH-mediated FASS) online preconcentration method. The pH-mediated FASS focuses and stacks heavy metal cations by controlling electrophoretic mobilities with a pH change between the analyte and the background electrolyte (BGE) in solution to improve the detection sensitivity of the system. We optimized and adjusted sample matrix solution (SMS) ratios and pH to create concentration and pH gradients for SMS and BGE. Furthermore, we optimize the microchannel width to improve the preconcentration effect further. The system and method analyzed soil leachates polluted with heavy metals and separated Pb2+ and Cd2+ within 90s, obtaining their levels at 58.01mg/L and 4.91mg/L with sensitivity enhancement factors (SEF) of 26.40 and 43.73. Compared with inductively coupled plasma atomic emission spectrometry (ICP-AES), the detection error of the system was less than 8.80%.

CeO2 quantum dots decorated g-C3N4 nanosheets: A potential scaffold for fluorescence sensing of heavy metals and visible-light driven photocatalyst

Herein, we report the synthesis of g-C3N4/CeO2 heterostructure using a facile co-precipitation method. The as-synthesized g-C3N4/CeO2 heterostructure was examined by several techniques in order to understand the morphology, thermal, structural, optical and compositional properties. A strong interfacial contact was observed between g-C3N4 nanosheets and CeO2 quantum dots (QDs) as CeO2 QDs were deposited on g-C3N4 nanosheets with slight agglomeration. The as-synthesized heterostructure was successfully applied as a probe for the fluorescence sensing of heavy transition metals (Cu(II), Hg(II) and Ag(I)) and a visible light active photocatalyst for the decomposition of tetracycline (TC) in an aqueous phase. The g-C3N4/CeO2 heterostructure exhibited remarkable selectivity towards the sensing of Cu(II), Hg(II) and Ag(I) heavy metal ions because of strong binding affinity of these metal ions towards nitrogen and oxygen containing functional moieties present in g-C3N4/CeO2 heterostructure. Furthermore, a good linearity was observed between the relative FL intensity and concentration of Cu(II), Hg(II) and Ag(I) ions with detection limit estimated to be 26.2 µM, 17.5 µM and 14.9 µM, respectively. The high selectivity for these ions was due to their strong binding affinity towards nitrogen and oxygen containing functional groups in g-C3N4/CeO2 heterostructure. Moreover, the removal efficiency of 77.95% was acquired for degradation of tetracycline in 160 min using g-C3N4/CeO2 heterostructure under optimized conditions. The photocatalytic results of the heterostructure could be accredited to the reduction in the recombination of excited carriers across the interface of the heterojunction. Therefore, the present work provides an effective strategy for the preparation of fluorescent photocatalytic materials that can be utilized for the FL detection of harmful heavy metal ions as well as degradation of pollutants in an aqueous phase.

Water-soluble anionic N-confused porphyrin for sensitive and selective detection of heavy metal pollutants in aqueous environment.

Efficient detection and quantification of metal ions in real time and in a cost-effective manner is a critical step in combating the increasing danger of heavy metal contamination of our biosphere. The potential of water-soluble anionic derivative of N-confused tetraphenylporphyrin (WS-NCTPP) has been investigated for quantitative detection of heavy metal ions. The results show that the photophysical properties of WS-NCTPP differ significantly in the presence of four metal ions, namely Hg(II), Zn(II), Co(II) and Cu(II). The variation in the spectral behaviour is driven by the formation of 1:1 complexes with all the four cations with varied degree of complexation. The selectivity of the sensing is studied through interference studies, indicating maximum selectivity for Hg(II) cations. Computational studies of the structural features of the metal complexes with WS-NCTPP help in establishing the geometry and binding interactions between the metal ions and the porphyrin nucleus. The results demonstrate the promising potential of the NCTPP probe which should be utilized for detection of heavy metal ions, especially mercury, in the near future.

An efficient self-made paper-based carbon electrode for electrochemical detection of heavy metal ions

An efficient self-made paper-based carbon electrode for electrochemical detection of heavy metal ions

Engineering carbon dots with a 18-crown-6 for the fluorescence detection of cadmium ions

Carbon dots (CDs) with their bright photoluminescence represent a platform for the development of analytical sensors. In the context of sensing applications, there has been great interest in developing CD-based sensing platform for the detection of heavy metal ions in aqueous samples. Compared to other metals, the sensing of cadmium (II) ions using carbon dots-based system has been poorly investigated. This work details the use of CDs as fluorescent probes for the sensitive detection of cadmium (II) ions. We demonstrate that the rational engineering of the surface of the CDs though the post-synthetic modification with a crown ether increases the selectivity toward the analyte via the formation of a metal-crown complex. Using this sensor, Cd2+ ions could be determined in the range from 1.0 to120 µM with 0.05 µM as a detection limit. The hybrid material shows high selectivity for cadmium ions over other ions and was validated by determination of Cd+2 in (spiked) water samples to underpin its practicability.

Unbiased and Signal-Weakening Photoelectrochemical Hexavalent Chromium Sensing via a CuO Film Photocathode.

Photoelectrochemical (PEC) sensors show great potential for the detection of heavy metal ions because of their low background noise, high sensitivity, and ease of integration. However, the detection limit is relatively high for hexavalent chromium (Cr(VI)) monitoring in addition to the requirement of an external bias. Herein, a CuO film is readily synthesized as the photoactive material via reactive sputtering and thermal annealing in the construction of a PEC sensing photocathode for Cr(VI) monitoring. A different mechanism (i.e., Signal-Weakening PEC sensing) is confirmed by examining the electrochemical impedance and photocurrent response of different CuO film photoelectrodes prepared with the same conditions in contact with various solutions containing concentration-varying Cr(VI) for different durations. The detection of Cr(VI) is successfully achieved with the Signal-Weakening PEC response; a drop of photocathode signal with an increasing Cr(VI) concentration from the steric hindrance effect of the in situ formed Cr(OH)3 precipitates. The photocurrent of the optimized CuO film photocathode linearly declines as the concentration of Cr(VI) increases from 0.08 to 20 µM, with a detection limit down to 2.8 nM (Signal/Noise = 3) and a fitted sensitivity of 4.22 µA·μM-1. Moreover, this proposed sensing route shows operation simplicity, satisfactory selectivity, and reproducibility.

Advances in Portable Heavy Metal Ion Sensors.

Heavy metal ions, one of the major pollutants in the environment, exhibit non-degradable and bio-chain accumulation characteristics, seriously damage the environment, and threaten human health. Traditional heavy metal ion detection methods often require complex and expensive instruments, professional operation, tedious sample preparation, high requirements for laboratory conditions, and operator professionalism, and they cannot be widely used in the field for real-time and rapid detection. Therefore, developing portable, highly sensitive, selective, and economical sensors is necessary for the detection of toxic metal ions in the field. This paper presents portable sensing based on optical and electrochemical methods for the in situ detection of trace heavy metal ions. Progress in research on portable sensor devices based on fluorescence, colorimetric, portable surface Raman enhancement, plasmon resonance, and various electrical parameter analysis principles is highlighted, and the characteristics of the detection limits, linear detection ranges, and stability of the various sensing methods are analyzed. Accordingly, this review provides a reference for the design of portable heavy metal ion sensing.

Carbon quantum dots: synthesis and applications as turn-off fluorescence sensors for detection of Co2+ ions in water and eco-friendly catalysts for treatment of wastewater

Carbon quantum dots (CQDs) are a new generation of QDs that have unique and interesting optical and structural properties. Fluorescence methods are useful, simple, and rapid for the detection of heavy metal ions in water, which has attracted great attention. In this research, a simple and rapid fluorescence method for the detection of cobalt (Co2+) ions in water is introduced. CQDs were synthesized by using pistachio as a precursor for the first time by a hydrothermal method. The QDs were characterized by structural analyses including x-ray diffraction, tunneling and scanning microscopies, energy-dispersive x-ray spectroscopy, infrared spectroscopy, BET surface area measurements, zeta potential measurements, and Raman spectroscopy. The Raman spectroscopy results showed a 3.54 value for the G/D ratio and this result confirmed that synthesized CQDs possess a graphitic crystalline structure. Zeta potential measurements confirmed the presence of a negative surface charge, resulting in high stability. These CQDs had blue photoemission with a broad PL peak between 300 to 600 nm. TEM images showed that CQDs are spherical with diameters of ∼7 nm. Their photocatalytic activities were studied with different dyes under both sun and UV light. Methylene blue had better degradation by the CQDs than methylene orange and Rhodamine B. The scavenger results indicate that radicals play a key role in the photocatalytic degradation of methylene blue under UV irradiation.

Tree-based machine learning models assisted fluorescent sensor array for detection of metal ions based on silver nanocluster probe

The growing concern over heavy metal pollution and its impact on the environment and human health has led to a proliferation of research on the detection and differentiation of heavy metal ions. A novel fluorescent sensor array utilizing only one single Ag-nanoclusters (Ag NCs) was developed for the efficient detection of six metal ions. The Ag NCs probe was prepared by using poly(methyl vinyl ether-alt-maleic acid) (PMVEM) as the ligand and has different fluorescence properties in water and dimethyl sulfoxide (DMSO). The interaction between metal ions and Ag NCs resulted in a characteristic fluorescence variation pattern which was subsequently analyzed using various tree-based machine learning models. We have compared different combinations of classification models and pre-processing methods of which the K-Nearest Neighbors Classifier with the first five linear discriminants has the highest accuracy. Through the integration of concentration models within a tree-based pipeline optimization framework, six unique concentration regression models were selected for each metal ion. In addition, the developed sensor array could identify metal ions in binary mixtures. And it still kept high accuracy for the classification of six target metal ions in river water. In conclusion, the proposed framework was found to be effective in the detection of heavy metal ions in environmental samples, thus providing a promising approach for addressing heavy metal pollution.

Enhanced Goos-Hänchen Shift of SPR Sensor with TMDCs and Doped PANI/Chitosan Composites for Heavy Metal Ions Detection in Aquatic Environment

A novel surface plasmon resonance (SPR) sensor with transition metal dichalcogenides (TMDCs) and polyaniline (PANI)/chitosan composite for detection of heavy metal ions in an aquatic environment is proposed and analyzed. A novel Goos-Hänchen (GH) shift sensing scheme based on TMDCs and PANI/chitosan structure is proposed. The theory shows that the GH shift can be significantly enhanced in the SPR structure silver (Ag), TMDCs, and PANI/chitosan heterostructures. The refractive index of Cu2+ ion is 1.3516, and the maximum GH shift of the hybrid structure of Ag-MoSe2-PANI/chitosan is−2067 λ at resonance angle 69.19° with MoSe2 4 layers and PANI/chitosan 123 nm. When different Cu2+ ion concentrations are added into the sample layer, the refractive index of the sample and GH shift of the SPR sensor will change. The maximum sensitivity of 2.425 × 106 λ/RIU is obtained by Ag-WSe2-PANI/chitosan structure, which is 463.42 times higher than the traditional SPR Ag film and 112.84 times higher than Ag-PANI/chitosan structure. Therefore, the configuration with GH shift provides a new development direction for the detection of heavy metal ions in an aquatic environment.

Amino-Functionalized Hierarchical Porous Carbon Derived from Zeolitic Imidazolate Frameworks for Ultrasensitive Electrochemical Sensing of Heavy Metals in Water

Electrochemical sensing provides a feasible avenue to monitor heavy metal ions (HMIs) in water, whereas the construction of highly sensitive and selective sensors remains challenging. Herein, we fabricated a novel amino-functionalized hierarchical porous carbon by the template-engaged method using ZIF-8 as the precursor and polystyrene sphere as the template, followed by carbonization and controllable chemical grafting of amino groups for efficient electrochemical detection of HMIs in water. The amino-functionalized hierarchical porous carbon features an ultrathin carbon framework with a high graphitization degree, excellent conductivity, unique macro-, meso-, and microporous architecture, and rich amino groups. As a result, the sensor exhibits prominent electrochemical performance with significantly low limits of detection for individual HMIs (i.e., 0.93 nM for Pb2+, 2.9 nM for Cu2+, and 1.2 nM for Hg2+) and simultaneous detection of HMIs (i.e., 0.62 nM for Pb2+, 1.8 nM for Cu2+, and 0.85 nM for Hg2+), which are superior to most reported sensors in the literature. Moreover, the sensor displays excellent anti-interference ability, repeatability, and stability for HMI detection in actual water samples.

The Mn-Doped CsPbCl3 Perovskite Nanocrystals as a Photoluminescent Probe for Copper Ions Detection

Trace detection of toxic heavy metal ions is a hot topic in the sensing research area, especially in the organic phase using inorganic fluorescent colloidal nanocrystals. We report Mn-doped CsPbCl3 perovskite nanocrystals (PNCs), which were synthesized via the hot-injection method, as a fluorescent probe for the detection of copper ions in hexane. The introduction of Mn altered the emission peak, and lower the toxicity of the probe material. The photoluminescence (PL) intensity of Mn-doped CsPbCl3 PNCs is significantly quenched after contact with the [Formula: see text] solution. The mechanism of Cu quenching is electron transfer, which is experimentally proved by analyzing the PL spectrum, absorption spectrum and PL decay lifetime. The sensor in solution shape and solid shape is both prepared and their detection range from 10 nM to 500 [Formula: see text]M. The limit of detection in a low concentration area reaches 10 nM, showing great potential in sensing applications. This work expands the wavelength area of the [Formula: see text] detection probe by perovskite nanocrystals, and also improves the properties of probe material in optical performance, low toxicity, and stability.

A novel electrochemical sensor based on sodium alginate‐decorated single‐walled carbon nanotubes for the direct electrocatalysis of heavy metals ions

AbstractIn recent years, the presence of heavy metal ions in food chains and water poses serious environmental and human health problems. Therefore, there has been a pressing need for fast simple, sensitive, and accurate methods for their detection. In this study a novel electrochemical sensor based on alginate sodium biopolymer decorating single‐walled carbon nanotubes was elaborated for the detection of trace level of heavy metal ions. Different brown algae were used to extract sodium alginate, with Cystoseira being the most common. Due to its high extraction yield and high mannuronate/guluronate (M/G) ratio, Compress a brown algae was chosen to disperse with single‐walled carbon nanotubes. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy were monitored to investigate each surface modification. Differential pulse anodic stripping voltammetry (DPASV) was used to follow the electrochemical heavy metal ions determination. Moreover, the performance of the optimized heavy metal ions sensor in terms of sensitivity, linear range, limit of detection, and reproducibility was investigated. The detection limits were found to be 0.1, 31, and 1 nM for Pb2+, Cd2+, and Cu2+, respectively. The results reported in this work showed good stability, high sensitivity, and appealing inter‐electrode repeatability. Finally, lead detection in tap water was carried out. The metrological performance of the present sensor makes it a good alternative for heavy metal ions detection.

Electrochemistry of Rhodanine Derivatives as Model for New Colorimetric and Electrochemical Azulene Sensors for the Detection of Heavy Metal Ions

Rhodanine (R) is a heterocycle having complexing properties for heavy metal (HM) ions. Considering the similar electron-donating character of diethylaminobenzene and azulene, electrochemical characterization of (Z)-5-(azulen-1-ylmethylene)-2-thioxo-thiazolidin-4-one (R1) and 5-(4 diethylamino-benzylidene)-2-thioxo-thiazolidin-4-one (R2) was performed to establish their common features. Chemically modified electrodes based on R1 and R2 were compared for HM recognition. Evidence for the formation of films was provided by scanning and controlled potential electrolysis, and HM recognition experiments were performed using their films. Parallel studies for analysis of HMs by complexation in solution were performed by UV-Vis. The analogy between R1 and R2 created the premise for easier selection of compounds for certain applications. The performance of the chemically modified electrodes was evaluated as detection limits for HMs. The azulene monomer (R1) proved to be the best candidate for Pb(II) detection, being about eight times more sensitive than R2. However, in solution, R2 proved to be a good choice for optical measurements, having a higher absorption coefficient. These results support the two ligands having different behaviors in homogeneous and heterogeneous systems.