Metal Ion Sensors Research Articles

Highly sensitive determination of Co(II) ions in solutions by using modified silver nanoparticles

In this manuscript, we report the development of a rapid and facile optic sensor for highly sensitive and selective detection of cobalt ions (Co(II)). The detection strategy was based on the specific silver nanoparticle-glutathione interaction and later on secondary interaction of this structure with cysteine and Co(II) ion. The interaction of these structures creates a new absorption band in the UV region. The intensity change of this band can be correlated by Co(II) ion concentration. The addition of cysteine decreases the Surface Plasmon Resonance (SPR) of silver nanoparticles but does not provide quantitative information. The proposed method offers the advantage of improved sensitivity for detection of Co(II) ions in a very short time period. Co(II) ions create a unique absorption peak during the complex formation and this peak provides sensitive determination of this metal ion in existence of other metal ions. The peak is visible only after taking the first derivative of absorption spectra. Under the optimized conditions, the detection limit of the method is around 0.68μM. In addition, the synthesized silver nanoparticles (AgNPs) were characterized by atomic force microscopy (AFM). The proposed metal ion sensor provides a very facile and convenient way to determine the concentration of Co(II) ions in aqueous system.

A fluorescence sensor array based on perylene probe monomer-excimer emission transition for the highly efficient differential sensing of metal ions and drinking waters

A new type of sensor array is developed for the highly efficient differential sensing of metal ions and drinking waters. Two functionalized fluorescent perylene probes (Pery-1 and Pery-2) were employed. These probes could interact with metal ions via electrostatic and coordinate bonding interactions. As a result, the probe monomer fluorescence was quenched, and the appearance of distinct excimer emission was observed. Depending on the metal ion used, various degrees of quenching of probe monomer fluorescence, and the generation of excimer emission were observed. For example, quenching of monomer fluorescence was observed when Cu2+ and Fe3+ ions were tested. However, quenching of monomer fluorescence and generation of excimer fluorescence were both observed when Pb2+, Zn2+ and Al3+ ions were employed. And it was also observed that Ni2+, Mn2+ and Cr3+ ions interacted differently with Pery-1 and Pery-2. These differences formed the basis of the metal ion sensor array. The sensor array was used for differentiation of eleven metal ions, and it was also capable of discrimination of metal ions at different concentrations, as well as the discrimination of metal ion mixtures. The array was further successfully used for the distinction of drinking waters, different brands of commercial mineral water, and evaluation of the quality of drinking water. We envisage that the monomer and excimer emission transition of the perylene probe could be easily adopted for efficient sensor array development for various sensing applications.

Zeolitic imidazolate frameworks for use in electrochemical and optical chemical sensing and biosensing: a review.

This review (with 145 refs.) summarizes the progress that has been made in the use of zeolitic imidazolate frameworks in chemical sensing and biosensing. Zeolitic imidazolate frameworks (ZIFs) are a type of porous material with zeolite topological structure that combine the advantages of zeolite and traditional metal-organic frameworks. Owing to the structural flexibility of ZIFs, their pore sizes and surface functionalization can be reasonably designed. Following an introduction into the field of metal-organic frameworks and the zeolitic imidazolate framework (ZIF) subclass, a first large section covers the various kinds and properties of ZIFs. The next large section covers electrochemical sensors and assays (with subsections on methods for gases, electrochemiluminescence, electrochemical biomolecules). This is followed by main sections on ZIF-based colorimetric and luminescent sensors, with subsections on sensors for metal ions and anions, for gases, and for organic biomolecules. The last section covers SERS-based assays. Several tables are presented that give an overview on the wealth of methods and materials. A concluding section summarizes the current status, addresses current challenges, and gives an outlook on potential future trends. Graphical abstract In recent years, ZIFs and their composites have been widely used as probes in chemical sensing, and these probes have shown great advantages over other materials. This review describes the current progress on ZIFs toward electrochemical, luminescence, colorimetric, and SERS-based sensing applications, highlighting the different strategies for designing ZIFs and their composites and potential challenges in this field.

Optical fiber sensors for measurement of heavy metal ion concentration: A review

With the increasing of water pollution problems, detection of heavy metal ion concentration in water environment becomes significant. Optical fiber sensor, with its particular advantages of small-size, anti-electromagnetic interference, chemical inertness, remote and real-time monitoring ability, has become an ideal platform for detection of heavy metal ion concentration. In this paper, we briefly review the current research progress of heavy metal ion sensors based on optical fiber technology. Five main measurement methods are described, including optical absorbance method, fiber grating method, modal interference method, plasmonic method, and fluorescence method. The sensing mechanisms, sensing structures, sensing materials, and sensing characteristics of different kinds of measurement methods are introduced and summarized. Furthermore, the advantages and disadvantages of each measurement method are analyzed. Finally, the future development directions of optical fiber heavy metal ion sensors are also discussed.

MPA-CdTe quantum dots as "on-off-on" sensitive fluorescence probe to detect ascorbic acid via redox reaction.

Mercaptopropionic acid (MPA) capped CdTe quantum dots (MPA-CdTe QDs) were synthesized in aqueous medium by hydrothermal method, which modified by Fe3+ could be used as a fluorescent probe to detect ascorbic acid (AA). MPA-CdTe QDs fluorescence probe could be used as successive sensor for metal ions and AA with "on-off-on" process. The fluorescence of QDs was quenched after adding Fe3+ to MPA-CdTe QDs. Then, the fluorescence of the Fe3+@MPA-CdTe QDs can be sensitively turned on by AA to give an "on-off-on" fluorescence response according to the oxidation-reduction between Fe3+ and AA. There was a linear relationship between fluorescence intensity quenching value and the concentration of Fe3+ in the range of 2-10μM since Fe3+ sensitively reacted with CdTe QDs. The linear detection range for AA was 0.1-1μM with a limit of detection of 6.6nM. The principle is proved by fluorescence emission spectroscopy, nuclear magnetic resonance spectroscopy. The proposed method is successfully used to detect the AA in human plasma sample.

A stable zinc(II)-organic framework as rapid and multi-responsive luminescent sensor for metal ions in water

A very stable ZnII-organic framework, {[Zn(Titpe)0.5(bpodc)]·(H2O)3}n (1, Titpe = 1,1,2,2-tetrakis(4-(imidazol-1-yl)phenyl)ethane, bpodc = benzophenone-4,4-dicarboxylic acid), has been synthesized under hydrothermal conditions. Single-crystal X-ray analysis reveals that 1 crystallizes in the monoclinic system and P21/c space group. Its overall structure is a 3-D stacking with a porosity of 20.95% and a 4-c type topological network; it shows good stability in many solvents. Studies of the solution-phase detection of metal cations show that Fe3+ and Cr3+ ions can quench luminescent emission of 1. Fluorescence titration experiments show that 1 is more selective to Fe3+ (Ksv = 2.8 × 104 M−1) than Cr3+ (Ksv = 1.4 × 103 M−1). The solution-phase detection for anions by 1 also show high selectivity and sensitivity for Cr2O72– anions (Ksv = 1.2 × 104 M−1). With water stability and strong blue luminescence, 1 can potentially apply as a reversible multi-responsive luminescence sensor for Fe3+, Cr3+, and Cr2O72– in aqueous solutions.

Acid-Switchable DNAzyme Nanodevice for Imaging Multiple Metal Ions in Living Cells.

Metal-assisted deoxyribozyme catalysis (DNAzyme) has been a general platform for constructing highly sensitive and selective detection sensors of metal ions. However, the "always on" mode of the traditional DNAzyme sensors greatly limits their application in the visual analysis of endogenous metal ions in a complex physiological microenvironment. To overcome this obstacle, a smart acid-switchable DNAzyme nanodevice is designed to control the DNAzyme activity in living cells and achieve simultaneous visualization of metal ions (Zn2+ and Pb2+) in situ. This nanodevice is built on DNAzyme precursors (DPs) and acid-switchable DNA (SW-DNA), precisely responding to pH variations in the range of 4.5-7.0, and the state of the three-strand hybridization of DPs successfully renders the DNAzymes inactive before being transported into cells. Once the nanodevice is taken up into living cells, the SW-DNA will change the configuration from linear to triplex in the acidic intracellular compartments (lysosomes, pH ∼4.5 to 5.0) and then the strands hybridized with the SW-DNA are liberated and subsequently react with DPs to form the active DNAzyme, which can further realize multi-imaging of intracellular metal ions. Moreover, this strategy has broad prospects as a powerful platform for constructing various acid-switchable nanodevices for visual analysis of multiple biomolecules in living cells.

Universal preparation of cellulose-based colorimetric sensor for heavy metal ion detection

A simple and universal strategy was developed to prepare cellulose/dye composite film, as colorimetric sensor for heavy metal ions (HMIs) detection. After regenerating cellulose solution in ethanol, the regenerated films were further soaking in dye/ethanol solution followed by hot-pressing, to obtain cellulose/dye composite films. 1-(2-pyridylazo)-2-naphthol (PAN) was used as an example, and the resultant cellulose/PAN composite films (CPs) possessed robust mechanical property (tensile strength of 52.9 MPa), light transmittance, and thermodynamic stability. PAN distributed uniformly as nanoparticles of 30 nm on cellulose because of the interaction between N of azo group of PAN and cellulose. When used as colorimetric sensor for Zn2+ detection, the detection limit of CP was as low as 100 ppb, and the color change was distinguishable after testing with tap water. Moreover, two more dyes including 1-(2-thiazolylazo)-2-naphthol (TAN) and dithizone (Dith) were also immobilized successfully on cellulose, and the resultant films were effective colorimetric sensor for HMIs like Zn2+ and Cu2+. This work provided a facile and universal method to prepare cellulose-based colorimetric sensor or HMI detection, demonstrating great potential in water treatment and natural resources utilization.

Fabrication of Metallochromic Dye Functionalized Hydrogel for On-site, Fast, User-friendly Metal-ion Sensing Kit

Colorimetric sensor has been prepared for easy and simple detection of metal ion in aqueous solution. Metallochromic dyes which change color when combining certain metal ion are introduced to prepare colorimetric sensors. In order to introduce dye into hydrogel, metallochromic dyes are modified to acrylic monomer using esterification reaction. Dye functionalized hydrogels are prepared in the forms of bulk and porous using dye functionalized monomer and processed to manufacture user-friendly sensing kit. Porous hydrogel shows faster detecting time than that of bulk. The color change of sensing kit could be confirmed according to concentration of each metal and be tabulated using sensing kit of porous type. Fast and efficiently metal ion detecting ability is expected using the proper data-process of colors.

A facile synthetic route and dual function of network luminescent porous polyester and copolyester containing porphyrin moiety for metal ions sensor and dyes adsorption

Abstract In this work, A novel optical metal ion sensor microporous polyesters and copolyesters containing porphyrin moiety as a monomeric unit in the main chain were successfully prepared by the interfacial condensation polymerization from 5,10,15,20-Tetrakis(4-hydroxyphenyl) porphyrin (Por-OH) and 5,10,15,20-Tetrakis(4-hydroxy-3-methoxyphenyl) porphyrin (Por-V) with aliphatic and aromatic acid chlorides derivatives (such as; adipoyl chloride, and azobenzene-4,4′-dicarboxylic chloride, respectively). These polyesters and copolyesters are characterized by FT-IR, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction, UV–Visible absorbance, fluorescence emission, and SEM measurements. The results show that our novel compounds are amorphous, have good thermal stability with high char yield and possess peaks similar to the porphynoid structure that make them good metal ion sensors with different metals ions (such as; Zn+2, Cu+2, Ni+2, Co+2, and Fe+3). Also, they can be used as dye adsorbents in aqueous solution and displayed amazing adsorption and selectivity toward cationic dye methylene blue (MB) over anionic sunset yellow (SY) in the dye's mixture.

A fluorescent Zn(II)-organic framework for selective detection of Pb2+ and a protective effect in osteoarthritis treatment by reducing ROS accumulation and apoptosis in chondrocytes

By using the π-electron rich 4,4′-stilbenedicarboxylic acid (H2sda), a Zn(II)-bearing metal-organic framework with the chemical formula of [Zn3(sda)3(H2O)2](H2O)4 (1) has been prepared through the reaction of the 4,4′-stilbenedicarboxylic acid with Zn(NO3)2·6H2O in the component solvent of H2O and MeOH with aid of HBF4. Considering its intensive fluorescent emission, 1 was studied as a fluorescent sensor for metal ions in water, and the results reveal that 1 can be developed into an excellent Pb2+ sensor in water by utilizing luminescence quenching with a detection limit of 32.6 nm. In biological research, we explored the protective effect of 1 in OA rats. First, the DCFH-DA staining assay was utilized to detect the ROS levels in primary chondrocyte. Then, the Annexin V-FITC/PI was conducted for evaluating the apoptotic cells percentage after treatment with 1. The results from molecular docking software exhibited a possible mode of the compound binding to Bcl2, indicating a potential modulation mechanism.

Facile Synthesis of Protonated Carbon Nitride/Ti3C2Tx Nanocomposite for Simultaneous Detection of Pb2+ and Cd2+

A high-sensitivity electrochemical sensor for heavy metal ions (HMIs) was prepared by associating Ti3C2Tx with protonated carbon nitride (H–C3N4/Ti3C2Tx). Due to the electrostatic interaction, massive H–C3N4 was distributed on the surface of Ti3C2Tx and served as coating material. H–C3N4/Ti3C2Tx composite showed great conductivity derived from Ti3C2Tx, and H-C3N4 was with abundant electroactive deposition sites for the deposition of HMIs. In addition, the stability of H–C3N4/Ti3C2Tx composite was enhanced due to the protective H–C3N4 coating. The H–C3N4/Ti3C2Tx electrode exhibited remarkable sensitivities for the simultaneous detection of Cd2+ (0.05 ∼ 1.50 μM) and Pb2+ (0.05 ∼ 1.50 μM) and the detection limit of Cd2+ and Pb2+ were 0.001 and 0.0006 μM, respectively. Notably, sensor based on H–C3N4/Ti3C2Tx composite showed excellent selectivity for Cd2+ and Pb2+ in the presence of interfere ions and molecules (K+, Na+, Ca2+, Hg2+, Cr2+, Cu2+, Cl−, NO3−, PO4−, ascorbic acid, uric acid, acetaminophen, glucose and nicotinamide). Besides that, distinguished stability and reproductivity of H–C3N4/Ti3C2Tx electrode indicate that this sensor is promising for HMIs in wastewater and other commercial applications.

A water-soluble bithiophene with increased photoluminescence efficiency and metal recognition ability.

A new water-soluble tri-tert-butyl-bithiophenesulfonamide (α2-tbS) was synthesized and a comprehensive spectroscopic and photophysical study was undertaken in organic solvents and water at different pH values. In contrast to the behaviour found for the parent (and un-substituted) α,α'-bithiophene (α2), in which radiationless decay processes are the main excited-state deactivation channels, the tert-butylsulfonamide derivative presents a significant fluorescence quantum yield (φF) (ca. one order of magnitude higher than that of α2). The high φF allowed further exploring α2-tbS as a selective fluorimetric sensor for metal ions. A strong selectivity towards Cu(ii) is observed at neutral pH values, whereas at pH = 9.5 a strong quenching upon the addition of Hg(ii) is observed. An additional high sensitivity of 0.64 ± 0.02 ppm towards Cu(ii) was observed, well below 1.25 ppm (∼20 μM), the maximum value allowed in drinking water by the EPA.

Conjugated molecules for colourimetric and fluorimetric sensing of sodium and potassium

New alkali metal ion sensors showing ratiometric colourimetric and fluorimetric responses with high selectivity and low limits of detection.

A facile approach for the synthesis of carbon dots from Hibiscus sabdariffa & its application as bio-imaging agent and Cr (VI) sensor

An eco-friendly approach to yield fluorescent carbon dots (C-dots) from bio-precursors has received a fascinating impact on its application as heavy metal ions sensors & bio-imaging agent. The C-dots have been synthesised by hydrothermal method from Hibiscus sabdariffa and characterised by IR, TEM, UV and photo luminescent spectral studies. This approach is evident to be facile, cost-effective and non– toxic with unremitting water solubility. The blue luminescent C-dots formed reveals excitation and size dependent photo luminescent behaviour. The as-prepared C-dots have been applied to detect Cr (VI) ions in aqueous solution. Also, the cyto-toxicity and bio-imaging ability of the C-dots were examined using breast cancer cells (MDA-MB 231 cell lines). The studies affirmed low toxicity & excellent bio-imaging potentiality of the C-dots.

Triazatruxene-Rhodamine-Based Ratiometric Fluorescent Chemosensor for the Sensitive, Rapid Detection of Trivalent Metal Ions: Aluminium (III), Iron (III) and Chromium (III).

We investigated the ability of a novel triazatruxene-rhodamine-based (TAT-ROD) chemosensor to detect the trivalent metal ions aluminium (Al3+), iron (Fe3+) and chromium (Cr3+). Operating via the through-bond energy transfer (TBET) pathway, the chemosensor exhibited low detection limits of 23.0, 25.0 and 170.0nM for Al3+, Fe3+ and Cr3+, respectively, along with high sensitivity and selectivity during a brief period (<15s). The binding ratio of the chemosensor and trivalent metal ions achieved by Job's method was 3:1, and when we added ethylenediaminetetraacetic acid (EDTA), the sensing process reversed. Altogether, our TAT-ROD chemosensor marks the first triazatruxene-based colorimetric and fluorometric metal ion sensor reported in the literature.

On fluorescent sensing of metal ions using water extracts of Salvia officinalis

Sensing of metal ions using fluorometric tools has wide applications in chemical, biological and environmental analysis. Plant phytochemicals, like flavonoids, exhibit intense fluorescence upon excitation by UV light. Leaves sage (Salvia officinalis), which is rich in polyphenolic and flavonoids compounds, were extracted using Soxhlet and microwave-assisted extractors. The extraction methods led to variations in the phytochemical composition of the extracts, which in turn affected their interaction with metal ions. Despite the variations in the composition, both of the extracts gave high fluorescence emissions when excited at 365 nm. Variations in fluorescence emissions of the extracts were studied in upon addition of each metal ion; i.e., Li+, Na+, K+, Cs+, Be2+, Mg2+, Sr2+, Ba2+, Al3+, Tl3+, Ge4+, Sn4+, Pb2+, Sb3+, Bi3+, Se4+, Cu2+, Ag+, Zn2+, Cd2+, Ti4+, Cr3+, Cr6+, Mo6+, W6+, Mn2+, Fe3+, Ni2+, Co2+ and Pd2+. When they were added into the Soxhlet extract, some ions (Cr3+, Pb2+, Co2+) induced intense fluorescence and some (Ge4+, Mg2+, K+, Na+) ions quenched the fluorescence emission. As for microwave-assisted extract, the addition of Sr2+, Mg2+ and Co2+ ions enhanced the fluorescence emission of the extract, but Fe3+, Be2+ and Cs+ lowered the fluorescence intensity. However, the results of the study should be considered as introductory and further selectivity and sensitivity studies should be done for each extract if they are used for sensing of metal ions. Yet, this study demonstrated that sage extracts has a potential for fluorescent sensing of certain metal ions.

Functionalization of macrobicyclic amino cryptands with photoactive fluorophoric units for metal ion sensing application

In this report we discussed the photo physical properties of two hexaanthryl substituted cryptands, L1 and L2 respectively. Further, photophysical studies of L1 and L2 with different transition metal ions as an input are carried out to probe these molecules as metal ion sensors in solution.

Fabrication & Characterization of Simple Structure Self-Assembled Graphene Oxide Based Heavy Metal Ion Sensor

The simple structure and high robustness of heavy metal sensors were developed by implementing a GO/Au/FR4 Substrate configuration. In this study, the sensing characteristics of an in-house fabricated heavy-metal-ion sensor (HMS) with graphene oxide (GO) as the sensing element was presented. The HMS employed a three electrodes configuration architecture, while GO of various concentrations ranging from 0.1 to 1 mg/ml would serve as the sensing medium. The surface of the working electrode was decorated with GO through drop-casting technique. Several types of heavy metal ions such as lead (Pb), mercury (Hg), and cadmium (Cd) were used in this study. The concentration of each was prepared according to the maximum exposure limit imposed by the World Health Organization, with Pb (10 ppm), Hg (1 ppm), and Cd (5 ppm). The sensing performance was found to be proportionate to GO concentration when the sensor was exposed to 10 ppm of Pb. On selectivity test using 1 mg/ml of GO, the sensor exhibited superior sensitivity towards 10 ppm of Pb, ∼ 1666.6%; followed by 5 ppm of Cd, ∼512.8%, while 1 ppm of Hg being the least detected, ∼10.5%. This signified GO shows greater affinity towards Pb ions detection in comparison to others.

Functionalized graphene oxide GO-[imi-(CH2)2-NH2] as a high efficient material for electrochemical sensing of lead: Synthesis surface and electrochemical characterization

Recently, many efforts have been widely focused on developing heavy metal ion sensors, particularly Pb (II) sensing due to really dangerous effects towards environment and hygienic issues. To meet the highest productivity of that metal ion sensing, we incorporated functional group of imidazole-(CH2)2-NH2 on graphene oxide (GO- imi-(CH2)2-NH2) with large surface area and boosted conductivity. The structure of the as-synthesized GO- imi-(CH2)2-NH2 was characterized by commonly used techniques. The characterization results confirmed the successful synthesizing strategy of grafting functional GO-imi- (CH2)2-NH2-CPE surface with reliable Pb(II) sensor. According to ideal conditions, Pb(II) calibration diagram recorder linearly (−0.58 V), between the concentration range of 5.0–300.0 nM. High surface area and strong Pb(II) adsorption ability with welfare conductivity of modified electrode indicated good Pb(II) sensing with a detection limit of 0.30 nM. That electrode provided ease –NH2 groups incorporating to Pb (II) with a good reusability and reproducibility of 5 times and approximately 90%, respectively, Therefore, during the deposition process, Pb accumulation will be risen on the electrode surface. The Pb monitoring in aqueous media was developed through a thoroughly affordable and sensitive electrochemical sensing approach come up with this proposed sensor.