Detection Of Toxic Metal Ions Research Articles

Nanostructured nitrogen doped diamond for the detection of toxic metal ions

This work demonstrates the applicability of one-dimensional nitrogen-doped diamond nanorods (N-DNRs) for the simultaneous electrochemical (EC) detection of Pb2+ and Cd2+ ions in an electrolyte solution. Well separated voltammetric peaks are observed for Pb2+ and Cd2+ ions using N-DNRs as a working electrode in square wave anodic stripping voltammetry measurements. Moreover, the cyclic voltammetry response of N-DNR electrodes towards the Fe(CN)6/4-/Fe(CN)6/3- redox reaction is better as compared to undoped DNR electrodes. This enhancement of EC performance in N-DNR electrodes is accounted by the increased amount of sp2 bonded nanographitic phases, enhancing the electrical conductivity at the grain boundary (GB) regions. These findings are supported by transmission electron microscopy and electron energy loss spectroscopy studies. Consequently, the GB defect induced N-DNRs exhibit better adsorption of metal ions, which makes such samples promising candidates for next generation EC sensing devices.

Study of selective sensing of Hg2+ ions by green synthesized silver nanoparticles suppressing the effect of Fe3+ ions

In this present study, we eliminate the strong interference effect of Fe3+ ions commonly observed in silver nanoparticles (AgNPs) based selective detection of toxic metal ions by localized surface plasmon resonances (LSPRs) of AgNPs. The photoinduced green crystalline silver nanoparticles (NPs) are synthesized using Allium sativum (garlic) extract. The bio ligands act as reducing as well as stabilizing agents and presence of ambient light source enhances the process of nanoparticles formations. The nanoparticles are well characterized by different measurement techniques (UV–vis, DLS-zeta sizer, XRD, TEM). The average particle size as calculated from TEM histogram study was found to be around 10 nm. The as synthesized nanoparticles are employed for selective and sensitive detection of Hg2+ showing excellent sensitivity with a lower detection limit of 2 μM. Fe3+ ions are also capable of oxidizing metallic Ag nanoparticles into ionic Ag+ in water medium and we are able to sense Fe3+ ions are by this green synthesized AgNPs. But the etching of Ag+ ions from AgNPs by Fe3+ ions are extremely quenched by the components of phosphate buffer medium. So the phosphate buffer medium provides good environment around AgNPs for selective and sensitive sensing of Hg2+ ions by lowering the localized surface plasmon resonances.

Bare indium tin oxide electrode for electrochemical sensing of toxic metal ion

In this communication, bare indium tin oxide (ITO) electrode has been proposed for electrochemical detection of toxic metal ions. Simultaneous detection of Pb2+, Cu2+ and Hg2+ was achieved using cyclic voltammetry. Further, the bare ITO was also subjected to differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) for sensing of Cu2+. The analytical parameters of the developed sensor established, that the simultaneous limit of detection (LOD) for Cu2+ was 0.15 ppm which is under the recommended values by World Health Organization and the United States Environment Protection Agency. DPV and EIS also resulted in a comparable LOD for Cu2+ using bare ITO electrode suggesting it to be a better alternative than modified electrodes.

A facile means for the improvement of sensing properties of metal-organic frameworks through control on the key synthesis variables

In this study, we investigated the optimal conditions for solvothermal-assisted synthesis of Eu-BDC-NH2 metal organic frameworks (MOFs) to improve their sensing capacity toward some selected target metal species. To this end, we focused on the interactive relationships between key synthesis variables (e.g., the relative molar ratios (and absolute amounts) of the reactants [EuCl3·6H2O vs. amino terephthalic acid (BDC-NH2)], temperature, and reaction duration). It was observed that different types of MOFs synthesized under diverse conditions consistently exhibited emission profiles of Eu3+. However, their luminescence properties were distinguished systematically by the synthesis conditions set for each sample group. The sensing potential of luminescent MOFs was explored for detection of toxic metal ions through two approaches, i.e., direct chemosensing and indirect biomolecule mediated sensing approach. In the former, the MOFs exhibited noticeable turn-off fluorescence behavior, especially with Hg2+ ions (i.e., a high Stern-Volmer quenching constant (Ksv) of 6.42 × 105 M−1 and limit of detection (LOD) of 0.007 M). In the latter, nanocomposites of MOFs-cyanocobalamin were characterized by a highly selective turn on fluorescence response towards Co2+ ions (Ksv = −6.25 × 103 M−1; LOD = 0.7 M). As such, the sensing capacity of these MOFs was distinguished efficiently by control of synthesis variables.

Constructed 3D hierarchical porous wool-ball-like NiO-loaded AlOOH electrode materials for the determination of toxic metal ions

The novel 3D hierarchical porous wool-ball-like NiO-loaded AlOOH hybrid (NiO/AlOOH-WB) was successfully fabricated through a facile hydrothermal approach followed in-situ growth of NiO nanoparticles (NPs) on AlOOH-WB support. Due to NiO NPs incorporated onto 3D AlOOH-WB surface, which not only increased electroactive area of the electrode but also showed the improved electron transfer rate examined by cyclic voltammetry (CV) and impedance analysis (EIS). NiO/AlOOH-WB/GCE displayed excellent electrochemical performance toward the simultaneous detection of thallium (Tl+), lead (Pb2+) and copper (Cu2+) ions. More importantly, compared with nano AlOOH wire clusters (WC) and nano leafs (LF), 3D hierarchical architecture AlOOH-WB showed excellent electrochemical activity toward targets due to the desirable structural properties. As-fabricated NiO/AlOOH-WB/GCE electrode revealed a higher selectivity and sensitivity towards Tl+, Pb2+ and Cu2+ with a low detection limit (S/N = 3) of 0.028, 0.025 and 0.030 μg/L and a broad linear range (0.1–100.0 μg/L). Furthermore, the fabricated sensor exhibited good stability, satisfactory reproducibility and good application prospect for the electrochemical detection of toxic metal ions individually and simultaneously.

A technique for highly sensitive detection of mercury ions using DNA-functionalized gold nanoparticles and resonators based on a resonance frequency shift

Mercury is widely used in various research and industrial areas. However, due to the ionization of mercury to the mercury ion, the influence of this ion on human health and the environment is cause for concern. Gold nanoparticles (AuNPs) are the most widely studied nanomaterial because of their unique optical, chemical, electrical, and catalytic properties and have attracted much interest regarding the applications to detection of toxic metal ions. In this paper, we propose a technique for detection of divalent mercury using AuNPs and Mercury-specific-oligonucleotide–conjugated resonators (MSOIRs). The detection technique is based on the measurement of a resonance frequency shift in the resonators that results from a specific interaction between the thymine–thymine base pair and mercury ion as well as the adsorption of AuNPs that act as a mass amplifier. Our proposed method can quantify mercury ions with the limit of detection of 100 pM, which is 10-fold better than that of the existing assays. Furthermore, MSOIR can detect mercury ions in real tap water. These results imply that the mercury-detecting sensor may be used to enhance drinking-water quality.

Facile one-step fabrication of a novel 3D honeycomb-like bismuth nanoparticles decorated N-doped carbon nanosheet frameworks: Ultrasensitive electrochemical sensing of heavy metal ions

A facile and low cost strategy for fabrication of a novel 3D honeycomb-like N-doped carbon nanosheet framework decorated with bismuth nanoparticles (3D Bi-NCNF) via co-pyrolysis of polyvinylpyrrolidone (PVP) and bismuth nitrate. As prepared 3D Bi-NCNF were characterized by a variety of techniques, i.e., field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, N2 adsorption-desorption analysis, thermogravimetric analysis and X-ray photoelectron spectroscopy. Newly designed 3D Bi-NCNF nanocomposite possess porous network structures, high specific surface area and high nitrogen content dopant acts as an electrode-modification material for selective and sensitive electrochemical sensors for the assay of Cd2+ and Pb2+ by square wave anodic stripping voltammetry (SWASV). Under optimized conditions, Bi-NCNF modified glassy carbon electrodes (GCEs) exhibited excellent electroanalytical performance for the simultaneous detection of Cd2+ and Pb2+, a wide linear response ranges of 1–120 μg L−1, with an ultralow detection limits of 0.02 and 0.03 μg L−1 (S/N = 3) were observed, respectively. Moreover, excellent repeatability, reproducibility and stability, and reliable assays in tap water samples were realized with constructed sensors. Therefore, this study provides a novel strategy for fabrication of metal nanoparticles decorated nitrogen-doped carbon-based frameworks materials, which could be utility for constructing sensitive electrochemical sensors in the convenient and rapid detection of toxic metal ions.

One-pot synthesis of Fe3O4@Chitosan-pSDCalix hybrid nanomaterial for the detection and removal of Hg2+ ion from aqueous media

New one pot mesoporous hybrid material containing iron nanoparticles fabricated with chitosan and p-sulfonato dansyl calix[4]arene composite (Fe3O4@Chitosan-pSDCalix) has been susccessfully synthesized. These mesoporous fluorescence iron nanoparticles were applied for the detection and removal of environmentally toxic Hg2+ ion from aqueous media. Different techniques were applied to confirm the preparation of Fe3O4@Chitosan-pSDCalix such as HRTEM, TGA/DTA, FTIR and XRD. Synthesized nanoparticles have average size of 17 nm with pore size of 0.19 nm as revealed from HRTEM images. Fluorescence study follow the photoinduced electron transfer process after addition of Hg2+ in the solution with decrease in intensity. Confocal microscope images were also acquired to confirm the presence of Hg2+ on nanoparticles. Adsorption study suggests that the removal of Hg2+ from aqueous media follows Langmuir adsorption isotherm. These studies suggest the synthesized Fe3O4@Chitosan-pSDCalix is an efficient hybrid material for the detection and removal of Hg2+ ion from aqueous media, and that it can also be used in biomolecules for the detection of toxic metal ions.

Colorimetric and fluorimetric detection of Hg2 + and Cr3 + by boronic acid conjugated rhodamine derivatives: Mechanistic aspects and their bio-imaging application in bacterial cells

Colorimetric and fluorimetric detection of toxic metal ions such as Hg2+ and Cr3+ has gained tremendous popularity over the conventional methods due to their operational simplicity, high selectivity, and speediness. Although numerous colorimetric and fluorescent receptors for Hg2+ or Cr3+ were reported in the literature, boronic acid-based receptors for these metal ions are rather scarce in the literature. Hence, in the present study dual function boronic acid conjugated rhodamine derivatives were developed, and their toxic metal ion detection abilities were studied by absorption, emission and visual detection methods. Absorption and emission spectral studies revealed that these derivatives displayed selectivity towards Hg2+, Cr3+ and Fe3+ among the other metal ions studied by forming new absorption band. Both the derivatives exhibited colorimetric response towards Hg2+ and Cr3+ by the change in color of the solution to pink and reddish pink with Fe3+. The detailed mechanism involved in the detection of Hg2+ was deduced by 1H NMR and ESI-MS studies. Further, these derivatives were used for fluorescence imaging of Hg2+ and Cr3+ in S. aureus bacterial cells. Thus the present manuscript demonstrated the use of boronic acid conjugated rhodamine derivatives as a dual function (colorimetric and fluorescent) probes and as imaging agents for Hg2+ and Cr3+, which are known for their toxic influence on bacterial cells.

A Simple and Highly Sensitive Thymine Sensor for Mercury Ion Detection Based on Surface Enhanced Raman Spectroscopy and the Mechanism Study.

Mercury ion (Hg2+) is recognized as one of the most toxic metal ions for the environment and for human health. Techniques utilized in the detection of Hg2+ are an important factor. Herein, a simple thymine was successfully employed as the surface enhanced Raman spectroscopy sensor for Hg2+ ion detection. The limit of detection (LOD) of the developed sensor is better than 0.1 nM (0.02 ppb). This sensor can also selectively distinguish Hg2+ ions over 7 types of alkali, heavy metal and transition-metal ions. Moreover, the LOD of the sensor can even achieve 1 ppb in practical application in the nature system, which is half the maximum allowable level (10 nM, 2 ppb) stipulated in the US Environmental Protection Agency standard. Further investigation of the thymine-Hg2+-thymine coordination mechanism provides a possible means of detecting other metal ions by replacing the metal ion-specific ligands. This work paves the way for the detection of toxic metal ions and environmental problems.

A simply synthesized biphenyl substituted piperidin‐4‐one for the fluorescence chemosensing of Cd2+

Ion-induced change in fluorescence is a straight-forward method for detection of toxic metal ions showing immediate response. Cadmium ions are toxic to the environment. We report in this paper a piperidine-4-one-based fluorescent chemosensor of Cd2+ ions, designed and synthesized by a simple method. The compound is characterized using infra-red (IR) and 1 H-NMR spectral techniques. The chemosensor showed Cd2+ ion selectivity and sensitivity in aqueous solution. The stoichiometry and the binding constants were determined using fluorescence spectroscopy. Piperidine-4-one shows a 1:1 stoichiometric binding to Cd2+ . The limit of detection of Cd2+ was reported.

A Novel Electrochemical Sensing Platform for the Simultaneous Trace Level Detection of Mercury, Cadmium and Copper

The present work is aimed at the development of highly sensitive electrochemical sensor based on immobilization of 1-phenyl-N-(pyridin-2-ylmethyl)ethanamine (PPE) on glassy carbon electrode (PPEGCE) for the simultaneous detection of toxic metal ions of mercury, cadmium and copper, employing electrochemical impedance spectroscopy differential pulse anodic stripping voltammetry and square wave anodic stripping voltammetry. We optimized several experimental parameters such as concentration of the modifier, pH, scan rate, number of cycles, accumulation time, deposition potential and supporting electrolytes for getting robust and intense signals of the analytes. The designed sensor showed nice voltammetric response in media of different pH, demonstrated good percentage recoveries and exhibited remarkable electrocatalytic activity. The results revealed the high sensitivity, stability and absolute discrimination ability of our designed sensor. A wide linear range with very low detection limits for the analytes as compared to reported methods revealed the applicability of our designed sensor as a preferred analytical tool. The limits of detection as low as 0.11, 0.18 and 0.13 nM were obtained for mercuric, cadmium and cupric ions using PPEGCE. These values are lower than the threshold concentration of our selected metal ions suggested toxic by World Health Organization (WHO) and Environmental Protection Agency (EPA). Thus, our results are expected to offer useful guidelines to the environmentalists and health stakeholders to apply measures for the protection of human and aquatic life from water toxins.

Ultrasensitive SERS Substrate Integrated with Uniform Subnanometer Scale “Hot Spots” Created by a Graphene Spacer for the Detection of Mercury Ions

Mercuric ion (Hg2+) is one of the most toxic and serious environment polluting heavy metal ions, which can be accumulated in human body through food chains and drinking water, and causes serious damage to human organs. Therefore, development of the efficient and sensitive method for detection of Hg2+ is very necessary. In this study, the high surface sensitivity and fingerprint information about the chemical structures based on surface‐enhanced Raman scattering (SERS) for sensing applications are taken advantage of. Au triangular nanoarrays/n‐layer graphene/Au nanoparticles sandwich structure with large‐area uniform subnanometer gaps are fabricated and used to detect Hg2+ in water via thymine–Hg2+–thymine coordination; the detection limit of Hg2+ is as low as 8.3 × 10−9m. Moreover, this SERS substrate is used to detect the Hg2+‐contaminated sandy soil and shows excellent performance. This study indicates the sandwich structure has a great potential in detection of toxic metal ions and environmental pollutants.

Fluorescence sensor array based on amino acid derived carbon dots for pattern-based detection of toxic metal ions

The development of convenient method for detection and identification of toxic metals ions is of great interest. In this work, we have developed a facile fluorescent sensor array based on luminescence carbon dots for detecting and differentiating a set of metal ions. Three kinds of nitrogen-doped carbon dots were synthesized by hydrothermal treatment of citric acid with three different amino acids (l-glycine, l-lysine and l-serine). These carbon dots had various surface states and thus exhibited diverse quenching responses to different metal ions. Six metal ions can be well distinguished at various concentrations (100, 50, 20 and 10μM). The discrimination accuracy of unknown samples was found to be 100% at a concentration as low as 10μM. In addition, the binary and ternary mixtures of three metal ions (Hg2+, Cu2+, Fe3+) could also be well recognized with this sensor array. This method is simple, label-free, and the sensor arrays could be obtained and expanded easily with large-scale and low-cost. It will broaden the application field of carbon dots sensors and give a new direction of developing sensitive array sensing systems.

SWASV performance toward heavy metal ions based on a high-activity and simple magnetic chitosan sensing nanomaterials

A high-activity, eco-friendly and inexpensive magnetic chitosan sensing nanomaterials were introduced for individual electrochemical detection toward Pb(II), Hg(II), Cu(II) and Cd(II) by square wave anodic stripping voltammetry (SWASV). The morphology and structure of Fe3O4-chitosan nanoparticles were characterized by TEM, XRD and FTIR respectively, and their electrochemical behavior based on the sensing materials modified glassy carbon electrode (GCE) was studied by cyclic voltammograms (CV) and electrochemical impedance spectra (EIS). Serving as a heavy metal ions sensor, the chitosan magnetic nanoparticles exhibited much more remarkable electrochemical response toward heavy metal ions. Especially, the introduction of chitosan significantly enhanced the SWASV performance toward Pb(II) with the high sensitivity of 50.6 μA/μM and LOD of 0.0422 μM, which was about 4.8 times than pure Fe3O4 nanoparticles. This result might be due to the strong charge-transfer interaction as well as the chelation and electrostatic interaction existence between Pb(II) and Fe3O4-chitosan unit, which will generate a high concentration region at electrode surface for efficient redox interaction between electrode and Pb(II). Furthermore, the Fe3O4-chitosan modified GCE offers good stability and potential practical applicability in the electrochemical determination of Pb(II). This work provides a potential simple and low cost material for electrochemical detection of toxic metal ions.

Continuous preparation of Fe3O4 nanoparticles through Impinging Stream-Rotating Packed Bed reactor and their electrochemistry detection toward heavy metal ions

We reported the continuous preparation and electrochemical behavior toward heavy metal ions of the Fe3O4 nanoparticles (Fe3O4 NPs). This Fe3O4 NPs were fabricated through a novel Impinging Stream-Rotating Packed Bed reactor with a high production rate of 2.23 kg/hour. The as-prepared Fe3O4 NPs were quasi-spherical with a mean diameter of about 10 nm and shown the characteristics of superparamagnetism with the saturated magnetization of 60.5 emu/g. The electrochemical characterization of the as-prepared Fe3O4 NPs toward heavy metal ions were evaluated using square wave anodic stripping voltammetry (SWASV) analysis. The results indicated that the modified electrode could be used to individual detection of Pb(II), Cu(II), Hg(II) and Cd(II). In particular, the modified electrode exhibited the selective detection toward Pb(II) with higher sensitivity of 14.9 μA/μM, while the response to Cu(II), Hg(II) and Cd(II) were negligible. Besides, the modified electrode shown good stability and potential practical applicability in the electrochemical determination of Pb(II). This above results offered a simple method for continuous preparation sensing materials in the application field of electrochemical detection of toxic metal ions through the technology of process intensification.

Palladium Nanoparticle Incorporated Porous Activated Carbon: Electrochemical Detection of Toxic Metal Ions.

A facile method has been developed for fabricating selective and sensitive electrochemical sensors for the detection of toxic metal ions, which invokes incorporation of palladium nanoparticles (Pd NPs) on porous activated carbons (PACs). The PACs, which were derived from waste biomass feedstock (fruit peels), possess desirable textural properties and porosities favorable for dispersion of Pd NPs (ca. 3-4 nm) on the graphitic PAC substrate. The Pd/PAC composite materials so fabricated were characterized by a variety of different techniques, such as X-ray diffraction, field-emission transmission electron microscopy, gas physisorption/chemisorption, thermogravimetric analysis, and Raman, Fourier-transform infrared, and X-ray photon spectroscopies. The Pd/PAC-modified glassy carbon electrodes (GCEs) were exploited as electrochemical sensors for the detection of toxic heavy metal ions, viz., Cd(2+), Pb(2+), Cu(2+), and Hg(2+), which showed superior performances for both individual as well as simultaneous detections. For simultaneous detection of Cd(2+), Pb(2+), Cu(2+), and Hg(2+), a linear response in the ion concentration range of 0.5-5.5, 0.5-8.9, 0.5-5.0, and 0.24-7.5 μM, with sensitivity of 66.7, 53.8, 41.1, and 50.3 μA μM(-1) cm(-2), and detection limit of 41, 50, 66, and 54 nM, respectively, was observed. Moreover, the Pd/PAC-modified GCEs also show perspective applications in detection of metal ions in real samples, as illustrated in this study for a milk sample.

Water Soluble Cationic Porphyrin Sensor for Detection of Hg2+, Pb2+, Cd2+, and Cu2+

Here we report the sensing properties of the aqueous solution ofmeso-tetra(N-methyl-4-pyridyl)porphine tetrachloride (1) for simultaneous detection of toxic metal ions by using UV-vis spectroscopy. Cationic porphyrin1displayed different electronic absorptions in UV-vis region upon interacting with Hg2+, Pb2+, Cd2+, and Cu2+ions in neutral water solution at room temperature. Quite interestingly, the porphyrin1showed that it can function as a single optical chemical sensor and/or metal ion receptor capable of detecting two or more toxic metal ions, particularly Hg2+, Pb2+, and Cd2+ions coexisting in a water sample. Porphyrin1in an aqueous solution provides a unique UV-vis sensing system for the determination of Cd2+in the presence of larger metal ions such as Hg2+, or Pb2+. Finally, the examination of the sensing properties of1demonstrated that it can operate as a Cu2+ion selective sensor via metal displacement from the1-Hg2+,1-Pb2+, and1-Cd2+.

Optical Interferometric Properties of Porous Anodic Alumina Nanostructures

Highly ordered porous anodic alumina nanostructures (PAA) with tunable pore properties have been prepared by electrochemical anodization. The PAA nanostructures were prepared in oxalic acid electrolyte at anelectrochemical potential of DC 40 V. The surface morphology of prepared PAA was examined using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results showed that the nanoporous structures have hexagonally arranged and highly ordered pore arrays with the pore diameters of about50 nm and interpore distance of 100 nm. The optical reflective interference spectroscopic properties of PAA were recorded in the wavelength range of 400 – 900 nm. The reflective spectra of PAA were used for the thickness measurements. It was observed that the pore properties of PAA varied with the applied voltage leading to changes in the interference pattern and in turn changes in the effective optical thickness (EOT) of the substrates. PAA having regular pore structure arrangement with optical reflective Interferometric spectroscopy find potential applications as reliable technique for optical biosensing, heavy and toxic metal ion detection for environmental control etc.

Highly selective monitoring of metals by using ion-imprinted polymers.

Ion imprinting technology is one of the most promising tools in separation and purification sciences because of its high selectivity, good stability, simplicity and low cost. It has been mainly used for selective removal, preconcentration, sensing and few miscellaneous fields. In this review article, recent methodologies in the synthesis of IIPs have been discussed. For several applications, different parameters of IIP including complexing and leaching agent, pH, relative selectivity coefficient, detection limit and adsorption capacity have been evaluated and an attempt has been made to generalize. Biomedical applications mostly include selective removal of toxic metals from human blood plasma and urine samples. Wastewater treatment involves selective removal of highly toxic metal ions like Hg(II), Pb(II), Cd(II), As(V), etc. Preconcentration covers recovery of economically important metal ions such as gold, silver, platinum and palladium. It also includes selective preconcentration of lanthanides and actinides. In sensing, various IIP-based sensors have been fabricated for detection of toxic metal ions. This review article includes almost all metal ions based on the ion-imprinted polymer. At the end, the future outlook section presents the discussion on the advancement, corresponding merits and the need of continued research in few specific areas. Graphical Abstract IIPs for the selective monitoring of metals.