Monitoring Of Heavy Metal Ions Research Articles

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.

Intellectualized Visualization of Single-Particle Raman Spectra for Sensitive Detection and Simultaneous Multianalysis of Heavy Metal Ions.

Easy-to-use, reliable, and real-time methods for detecting heavy metal ion contamination are urgently required, which is a primary concern for water pollution control and human health. However, present methods for this aim are still unable to achieve simultaneous multianalysis for complex real sample detection. Herein, an intellectualized vision-based single-nanoparticle Raman imaging strategy combined with ion-responsive functional nucleic acids (FNAs) was proposed to address these issues. We reported a correspondence between the concentration of the analytes and the density of particles (DOP) of specifically captured nanoparticles to achieve sensitive detection and simultaneous multianalysis of heavy metal ions. The specific detection of Pb2+ (Hg2+) was obtained with a detection linear range from 100 pM to 100 nM (from 500 fM to 100 nM) and limit of detections low to 1 pM (100 fM), with the advantages of good specificity, excellent homogeneity, and reproducibility. Furthermore, the differentiation of different heavy metal ions (Pb2+/Hg2+) was achieved, i.e., the simultaneous multianalysis, based on Raman imaging of the single particle and intelligent machine vision method. Finally, the Raman imaging assay was utilized for real sample analysis, and it provided a powerful and reliable tool for detecting trace Pb2+/Hg2+ in real water samples and facilitated the portable on-site monitoring of heavy metal ions.

Self-Powered Robotic Sensor for Remote and Real-Time Monitoring of Heavy Metal Ions

In the recent years, heavy metal pollution has tremendously increased worldwide due to natural as well as anthropogenic reasons. Heavy metals accumulate in the human body through drinking water and food, ultimately causing irreversible damage to the body. For most of the heavy metals, the World Health Organization (WHO) has set permissible limits from 0.003-3 ppm in drinking water, above which it is contaminated. In addition, chemical threats remain a major global concern for sampling and sensing factors in unsafe environments. Therefore, robotic hand-based chemical sensing platforms that can monitor hazardous pollutants in the real environment are essential. Although robotic hand-based chemical sensors show great potential to substantially prevent humans from chemical threats in the environment, applications are often limited by the requirement of high-power consumption. In this study, we have fabricated a self-powered triboelectric nanosensor, which is integrated with a robot platform with wireless transmission capability, to detect heavy metal ions in the environment through a rapid onsite detection mechanism. In this regard, a copper electrode modified by an ion selective membrane (ISM) is used as a solid triboelectric material and is integrated with a robotic hand. Since the ionophore selectively binds to the corresponding ions, the solid-liquid TENS could detect Cr6+, Pb2+, and As3+ ions at a wide range of concentrations by the periodic contact and separate motion of the sensor probe to lead (Pb2+), arsenic (As3+) and chromium (Cr6+) solutions. This realization of direct integration of self-powered sensors with robotics provides low-cost and automated chemical sensing mechanisms. It can be applied to various environments for on-site detection of hazardous analytes and security. Finally, a real time remote monitoring system allows the presentation of the environmental monitoring data on mobile devices and enables remote real-time monitoring of the hazardous pollutants.

Ion-Imprinted Polymeric Materials for Selective Adsorption of Heavy Metal Ions from Aqueous Solution.

The introduction of selective recognition sites toward certain heavy metal ions (HMIs) is a great challenge, which has a major role when the separation of species with similar physicochemical features is considered. In this context, ion-imprinted polymers (IIPs) developed based on the principle of molecular imprinting methodology, have emerged as an innovative solution. Recent advances in IIPs have shown that they exhibit higher selectivity coefficients than non-imprinted ones, which could support a large range of environmental applications starting from extraction and monitoring of HMIs to their detection and quantification. This review will emphasize the application of IIPs for selective removal of transition metal ions (including HMIs, precious metal ions, radionuclides, and rare earth metal ions) from aqueous solution by critically analyzing the most relevant literature studies from the last decade. In the first part of this review, the chemical components of IIPs, the main ion-imprinting technologies as well as the characterization methods used to evaluate the binding properties are briefly presented. In the second part, synthesis parameters, adsorption performance, and a descriptive analysis of solid phase extraction of heavy metal ions by various IIPs are provided.

A Near-Infrared Plasmonic Sensor Based on Wedge Fiber-Optic for Ultra-Sensitive Hg Detection

The growing number of serious diseases caused by ever-increasing heavy metal ions pollution have necessitated the use of ion sensors in healthcare and environment monitoring systems. Even with low concentrations heavy metal ions can cause significant harm, so ultra-sensitive on-site and label-free monitoring of heavy metal ions is of great importance. In this work, a simple, portable and high sensitivity optical fiber surface plasmon resonance (SPR) sensor is demonstrated for the detection of Hg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> . On the basis of the investigation of the effects of different incident angles, the optical fiber sensor adopts wedged tip probe with a 75° incident angle. The plasmonic sensor exhibits a superior refractive index bulk sensitivity of up to 13830 nm/RIU in near-infrared band, which is a further step in ultrasensitive sensing detection, compared with the traditional optical fiber SPR sensors. In addition, we validate the optical fiber sensor's performance for Hg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> sensing. By self-assembling monolayer of 1,6-Hexanedithiol (HDT) on the sensing surface, the Au-coated fiber-optic probe is modified to capture Hg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> . The lowest detection limit is found to be 0.324 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathbf{ug}/\mathbf{mL}$</tex-math></inline-formula> for the near-infrared band and the sensitivity can reach up to 0.22 nm/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$({\mathbf{ug}/\mathbf{mL}})$</tex-math></inline-formula> . The experimental results show the excellent promise for our sensor in applications of environmental monitoring due to high sensitivity, selectivity and low-cost.

A Highly Sensitive Electrochemical Sensor for Cd2+ Detection Based on Prussian Blue-PEDOT-Loaded Laser-Scribed Graphene-Modified Glassy Carbon Electrode

Heavy metal ion pollution has had a serious influence on human health and the environment. Therefore, the monitoring of heavy metal ions is of great practical significance. In this work, we describe the development of an electrochemical sensor to detect cadmium (Cd2+) using a Prussian blue (PB), poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT)-loaded laser-scribed graphene (LSG) nanocomposite-modified glassy carbon electrode (GCE). In this nanocomposite material, we successfully brought together the advantages of an extraordinarily large surface area. The accumulation of PB nanoparticles results in an efficient electrochemical sensor with high sensitivity and selectivity and fast detection ability, developed for the trace-level detection of Cd2+. Electrochemical features were explored via cyclic voltammetry (CV), whereas the stripping voltammetry behavior of modified electrodes was analyzed by utilizing differential pulse voltammetry. Compared with bare GCE, the LSG/PB-PEDOT/GCE modified electrode greatly increased the anodic stripping peak currents of Cd2+. Under the optimized conditions, the direct and facile detection of Cd2+ was achieved with a wide linear range (1 nM–10 µM) and a low LOD (0.85 nM).

Cholesteric Liquid Crystal Photonic Hydrogel Films Immobilized with Urease Used for the Detection of Hg2+

Mercury ion is one of the most widespread heavy metal contaminants which can accumulate in the body through multiple channels, posing a detrimental impact on human health. We demonstrate a simple and low-cost method for the detection of Hg2+ assisted by a cholesteric liquid crystal photonic hydrogel (polyacrylic acid (PAA)) film with immobilized urease (CLC-PAAurease film). In the absence of Hg2+, a significant change in color and an obvious red shift in the reflected light wavelength of the prepared film were observed, since urease can hydrolyze urea to produce NH3, resulting in an increasing pH value of the microenvironment of CLC-PAAurease film. Hg2+ can inhibit the activity of urease so that the color change of the film is not obvious, corresponding to a relatively small variation of the reflected light wavelength. Therefore, Hg2+ can be quantitatively detected by measuring the displacement of the reflected light wavelength of the film. The detection limit of Hg2+ is about 10 nM. This approach has a good application prospect in the monitoring of heavy metal ions in environmental water resources.

A fully integrated fast scan cyclic voltammetry electrochemical method: Improvements in reaction kinetics and signal stability for specific Ag(I) and Hg(II) analysis

• A fully integrated FSCV electrochemical method is developed. • This proposed method is to improve reaction kinetics and signal stability. • TdT-yielded DNAs can be used to construct electrode substrate favorably. • The platform is suited for Ag(I) and Hg(II) analysis well. • The method is conducive to the development of the real-time detection device. Inspired by the urgent need to detect trace heavy metal ions in various real samples, we construct a unique electrochemical biosensing method for heavy metal ions Ag(I) and Hg(II) analysis in this work. The biosensor is constructed by using terminal deoxynucleotidyl transferase (TdT) to catalyze the addition of dCTP and dTTP in 3′-OH end of original DNAs, thus producing enough long DNAs. This unique DNAs have a strong affinity to Ag(I) and Hg(II), and C-Ag(I)-C and T-Hg(II)-T structures occurs at the electrode surface. Meanwhile, the introduction of fast-scanning cyclic voltammetry (FSCV) can achieve the stable signal output all the while, where the reaction kinetics are superior to the diffusion kinetics, resulting in a significant improvement on reaction kinetics and signal stability. Based on it, simple detection of Ag(I) or Hg(II) is demonstrated powerfully with good detection limit (3 × 10 −14 M or 3 × 10 −15 M, S/N = 3); additionally, simultaneous detection of Ag(I) and Hg(II) is achieved with negligible interference. Furthermore, the proposed method has been also applied for some DNA electronic computing logic gates by designing simple or multiple inputs and output favorably. Based on these, the FSCV method has potential applications for the monitoring of heavy metal ions in real sample analysis.

Ti3C2-MXene@N-doped carbon heterostructure-based electrochemical sensor for simultaneous detection of heavy metals

High-resolution electrochemical sensors with excellent sensitivity and selectivity are urgently needed for simultaneous monitoring of heavy metal ions (HMIs) in the environment. In this study, a nitrogen-doped carbon-coated Ti3C2-MXene heterostructure (Ti3C2@N-C)-based electrochemical sensor was developed for simultaneously determining (Cd2+) and (Pb2+) in seawater and tap water via square wave anodic stripping voltammetry (SWASV). The sensor exhibits excellent performance with a low limit of detection (LOD) (Cd2+ 2.55 nM, Pb2+ 1.10 nM), as well as excellent selectivity in the presence of interfering ions (Zn2+, Fe3+, Fe2+, Co2+, Ni2+, Mn2+, Cu+, Cu2+, and K+) and high resolution for simultaneous detection of Cd2+ and Pb2+. The N-C and Ti3C2-MXene heterostructure improves the conductivity of the composites by accelerating the electron transfer. The nitrogen-doping in Ti3C2@N-C provides adsorbent sites for electrons to coordinate with HMIs. Due to the heterostructure and the coordination by nitrogen, the interface charge transfer is enhanced and the number of selective adsorption sites is increased, improving the metals determination performance. This study proposes a new strategy for improving the electrochemical characteristics of Ti3C2-MXene by using heterostructure and nitrogen-doping effect, and develops a highly sensitive sensor for selective and simultaneous determination of HMIs.

In situ fabrication of urchin-like Cu@carbon nanoneedles based aptasensor for ultrasensitive recognition of trace mercury ion

Mercury ion (Hg2+) is a strong toxic heavy ion that causes severe damages to the environment and readily accumulates in the food chain. However, it remains a major challenge to realize a sensitive and precise recognition of Hg2+ with a trace concentration for early identifying the pollution source. In this work, a novel electrochemical aptasensor was designed to achieve an ultrasensitive and quantitative detection of trace Hg2+, relying on an urchin-like architecture of Cu@carbon nanoneedles (Cu@CNNs) as the electroactive probe. This specific nanostructure was in-situ constructed through a controllable pyrolysis process, serving as a signal magnifier and DNA loading platform owing to its outstanding electrocatalysis and large specific surface areas. Meanwhile, an exonuclease III-assisted cycling amplification strategy was designed to efficiently amplify the signal strength of trace Hg2+via the consecutive release of report probes in nicking reaction. This as-prepared Hg2+ aptasensor exhibited an ultralow detection limit of 3.7 fM (7 × 10−6 ppm) and a wide linear range from 10 fM to 10 μM, together with the satisfactory stability and reusability for assay in real water samples. It is highly expected that this Cu@CNNs based aptasensor will have tremendous potentials in the early warning and efficient pollution monitoring of heavy metal ions.

Novel nano-engineered environmental sensor based on polymelamine/graphitic-carbon nitride nanohybrid material for sensitive and simultaneous monitoring of toxic heavy metals

Heavy metal ions (HMIs) pollution is always a serious issue worldwide. Therefore, monitoring HMIs in environmental water is an important and challenging step to ensure environmental health and human safety. In this study, we spotlight an effortless, single-step in-situ electrochemical polymerization deposition technique to fabricate a novel, low-cost, efficient, nano-engineered poly(melamine)/graphitic-carbon nitride nanonetwork (PM/g-C3N4) modified screen-printed carbon electrode (SPE) for sensitive, selective, and simultaneous electrochemical monitoring of toxic HMIs in environmental waters. g-C3N4 nanomaterial was prepared using melamine as a precursor via pyrolysis technique. As-prepared g-C3N4 and melamine monomer were electrochemically in-situ polymerized/deposited over pre-anodized SPE (ASPE) using cyclic voltammetry technique. XRD, XPS, and SEM were engaged to characterize the developed electrode. The fabricated PM/g-C3N4/ASPE was applied as an environmental sensor to selective and simultaneous electrochemical detection of Pb2+ and Cd2+ ions using differential pulse voltammetry technique. The developed sensor displayed excellent selectivity and sensitivity towards Pb2+ and Cd2+ with limit of detections of 0.008 µM and 0.02 µM, respectively. The fabricated PM/g-C3N4/ASPE sensor exhibits superior stability, repeatability, good anti-interference, and applicability for recognition of Pb2+ and Cd2+ ions in real water samples. These results proved that developed environmental sensor is low-cost, efficient, practical platform for rapid, selective, simultaneous monitoring of HMIs in the environment.

A green path to extract carbon quantum dots by coconut water: Another fluorescent probe towards Fe3+ ions

In recent years, carbon quantum dots (CQDs) have been of great enthrallment in the fluorescent probe field. Carbon precursors with interesting physicochemical properties may be derived from natural sources. In this research, for the first time, coconut water has been used as a source of carbon to prepare blue fluorescent CQDs without any modification and functionalization. The preparation of CQDs is very simple and cost-effective, when compared with other conventional techniques. The reaction parameters temperature and pH were varied to obtain monodispersed spherical CQDs with an average grain size of ∼5nm. The CQDs exhibit blue emission with a wavelength of 487nm with an excitation wavelength of 390nm and are used for Fe3+ ions detection. Fe3+ ions have been observed to quench the fluorescence intensity of the CQDs than other heavy metals. In the presence of Fe3+ ions, the fluorescent CQDs are quenched due to the interaction of CQDs and Fe3+ ions. A spectroscopic result shows that Fe3+ ions can be observed within a concentration of 0–700μM, as well as the detection limit is 0.30μM. The CQDs provide a unique pathway for potential application in the environmental monitoring of heavy metal ions.

On-site low-power sensing nodes for distributed monitoring of heavy metal ions in water

Heavy metal pollution in water environments poses a great threat to public health and to the ecological environment due to its high toxicity and non-degradability. However, many existing detection methods require laboratory-based bulky instruments and time-consuming manual operations. Although some on-site systems exist, they are difficult to deploy on a large scale owing to their large size and high cost. Here, we report a sensing node featuring low power consumption and low cost, achieved by integrating microsensor, microfluidic, and electronic modules into a compact size for automatic and scalable heavy metal pollution monitoring. Digital microfluidic and electrochemical sensing modules are integrated on a chip, thereby combining the procedures of sample pretreatment, electrochemical sensing, and waste removal for automatic and continuous monitoring. The feasibility of the platform is demonstrated by Pb2+ detection in tap water. With a 3500 mA·h battery, the compact sensing node could work for several years in principle. There is scope for further improvements to the system in terms of wider functionality and reductions in size, power consumption, and cost. The sensing node presented here is a strong candidate for distributed monitoring of water quality as an Internet-of-Things application.

A 3D origami paper-based analytical device combined with PVC membrane for colorimetric assay of heavy metal ions: Application to determination of Cu(II) in water samples

Microfluidic paper-based analytical devices (μPADs) as a potentially powerful analytical platform have recently gained significant attention for on-site monitoring of heavy metal ions, which are one of the most significant environmental concern because of non-degradability and high toxicity. The commonly applied μPADs suffers from some defects, such as heterogeneous deposition of reagent, resulting in poor detection limits and low sensitivity. So, in this work, a three-dimensional origami μPAD combined with PVC Membrane was developed, which can manage problems of movement of colored products or leaching out the dye and leading to color heterogeneity in the detection zones. Furthermore, a waste layer was added to μPAD for loading of more amounts of the analyte, which results in improvement of detection limit. As a proof of concept, the μPAD was used for the analysis of Cu2+ ion. For this purpose, pyrocatechol violet and chrome azurol S as colorimetric reagents were doped into PVC membrane and injected in the detection zone. The proposed μPAD was presented good linearity in the ranges of 5.0–1400.0 and 5.0–200.0 mg L−1, and the limits of detections of 1.7 and 1.9 mg L−1 in presence of chrome azurol S and pyrocatechol violet, respectively.

Functionalized Electrospun Nanofibers as a Versatile Platform for Colorimetric Detection of Heavy Metal Ions in Water: A Review.

The increasing heavy metal pollution in the aquatic ecosystem mainly driven by industrial activities has raised severe concerns over human and environmental health that apparently necessitate the design and development of ideal strategies for the effective monitoring of heavy metals. In this regard, colorimetric detection provides excellent opportunities for the easy monitoring of heavy metal ions, and especially, corresponding solid-state sensors enable potential opportunities for their applicability in real-world monitoring. As a result of the significant interest originating from their simplicity, exceptional characteristics, and applicability, the electrospun nanofiber-based colorimetric detection of heavy metal ions has undergone radical developments in the recent decade. This review illustrates the range of various approaches and functional molecules employed in the fabrication of electrospun nanofibers intended for the colorimetric detection of various metal ions in water. We highlight relevant investigations on the fabrication of functionalized electrospun nanofibers encompassing different approaches and functional molecules along with their sensing performance. Furthermore, we discuss upcoming prospectus and future opportunities in the exploration of designing electrospun nanofiber-based colorimetric sensors for real-world applications.

Electrochemical Plasmonic Fiber-optic Sensors for Ultra-Sensitive Heavy Metal Detection

Real-time and high-sensitivity monitoring of heavy metal ions in solution is of great significance in environmental monitoring. The traditional electrochemical methods suffer from electrochemical noise and environmental interferences for heavy metal trace detection. To address these issues, we propose a novel electrochemical surface plasmon resonance (EC-SPR) optical fiber sensor. The sensor comprises a tilted fiber Bragg grating imprinted in a commercial single-mode fiber and coated with a nanoscale gold film for high-efficiency SPR excitation. The gold-coated optical fiber serves as a working electrode, performing the dual functions of anodic stripping voltammetry and SPR optical sensing. We demonstrate detection of Pb2+ as an example of a typical heavy metal ion. We show a stable and reproducible correlation between the real-time ion deposition–stripping cycles and the optical transmission of the optical fiber, with a limit of detection of 10−10 M and a dynamic range of nearly five orders of magnitude. Moreover, by taking derivative of the SPR amplitude change, we can clearly identify the peak stripping potential of the detected ions, and therefore, realize specific ion identification. The method proposed is inherently immune to temperature cross-talk because the core mode is temperature dependent but insensitive to the surrounding media. The proposed EC-SPR fiber-optic sensor has the advantages of compact size, flexible shape, and remote operation capability, thereby, opening the way for other opportunities for electrochemical monitoring in various hard-to-reach locations and remote environments.

Electroanalytical detection of heavy metals using metallophthalocyanine and silica-coated iron oxide composites

The monitoring of heavy metal ions particularly in water is important in safeguarding the environment and humans from the toxic effects these metal ions pose. This work describes the synthesis, characterization and electrocatalytic properties of silica-coated iron oxide nanoparticles (Si-NP) in the presence of cobalt or iron phthalocyanines (MPc) for heavy metal (HM) detection. TEM, XRD, XPS and VSM confirmed the successful synthesis of Si-NP with an average diameter of 12.07 nm. The electrochemical sensing properties of MPc/Si-NP-modified glassy carbon electrodes (GCE) were assessed for HM detection. Differential pulse anodic stripping voltammetry (DPASV) studies indicated detection limits that compared positively with the literature. The FePc/Si-NP composite showed the lowest detection limits (S/N = 3) of 3.66, 11.56, 2.28, 4.54 μg L−1 for arsenic (As), cadmium (Cd), mercury (Hg) and lead (Pb), respectively. A linear working range of 10–100 μg L−1 was obtained for As3+, Hg2+ and Pb2+ ions while it was between 20 and 100 μg L−1 for Cd2+ ions. Both composites displayed reproducible signals for the simultaneous detection of the HMs for ten consecutive scans. These composites offer a cheap and simplistic sensing device for HM analysis.

Paper-Based Sensor Chip for Heavy Metal Ion Detection by SWSV.

Heavy metal ion pollution problems have had a terrible influence on human health and the environment. Therefore, the monitoring of heavy metal ions is of great practical significance. In this paper, an electrochemical three-electrode system was fabricated and integrated on nitrocellulose membrane (NC) by the use of magnetron sputtering technology, which exhibited a uniform arrangement of porous structure without further film modification. This paper-based sensor chip was used for Cu2+ detection by square-wave stripping voltammetry (SWSV). Within the ranges of 5–200 μg·L−1 and 200–1000 μg·L−1, it showed good linearity of 99.58% and 98.87%, respectively. The limit of detection was 2 μg·L−1. On the basis of satisfying the detection requirements (10 μg·L−1), the integrated sensor was small in size and inexpensive in cost. Zn2+, Cd2+, Pb2+ and Bi3+ were also detected by this paper-based sensor chip with good linearity.

A simplified electrochemical instrument equipped with automated flow-injection system and network communication technology for remote online monitoring of heavy metal ions

Fully automated electrochemical measuring equipment was designed in this work for online monitoring of heavy metal ions in water. Compared with the commercial instrument already available, the equipment was simplified with four common electrochemical methods: cyclic voltammetry (CV), linear sweep voltammetry (LSV), differential pulse voltammetry (DPV), and square wave voltammetry (SWV). In the monitor, a series of operations for the detection, i.e., sampling and dispensing of the sample, addition of relevant chemicals, acquisition and transmission of the measured data, were fully automated. The monitoring was effective and convenient in combination with the internet of things. To demonstrate the performance of the instrument, a comparison was made with commercial electrochemical analyzer and a well coincidence was gained in laboratory. Finally, online monitoring was also applied in real environment and the accuracy of the instrument was confirmed compared with standard analytical method.

DNA Modified Fe3O4@Au Magnetic Nanoparticles as Selective Probes for Simultaneous Detection of Heavy Metal Ions.

Driven by the urgent need to detect trace heavy metal ions in various real water samples, this article demonstrates for the first time an electrochemical biosensor based on DNA modified Fe3O4@Au magnetic nanoparticles (NPs). Three DNA probes are designed to contain certain mismatched base pairs. One is thiolated and modified on the surface of Fe3O4@Au NPs (DNA 1). The other two probes (DNA 2 and 3) are labeled with two independent electrochemical species. Stable structures of cytosine-Ag+-cytosine and thymine-Hg2+-thymine formed in the presence of Ag+ and Hg2+ can assist the hybridization of DNA 1/DNA 2 and DNA 1/DNA 3, which locate corresponding electrochemical species onto the surface of the magnetic NPs. The achieved nanocomposites are then used as selective electrochemical probes for the detection of heavy metal ions by recording the square wave voltammetry signals. Simultaneous detection of Ag+ and Hg2+ is demonstrated without significant interference, and their individual high sensitivities are fundamentally preserved, which meet the requirements of U.S. Environmental Protection Agency (USEPA). Furthermore, the proposed method has been challenged by various real water samples. The results confirm the DNA modified magnetic NPs based sensing method may have potential applications for the monitoring of heavy metal ions in real sample analysis.