Detection Of Multiple Metal Ions Research Articles

Detection of multiple metal ions exclusively at bilayer interface: Does the nature of the membranous aggregates affect the sensitivity?

A pyrenylated fluorogenic probe has been designed that can detect heavy metal pollutants exclusively at the bilayer interface. The compound, due to extensive self-aggregation, showed no interaction with metal ions in the bulk solution phase. However, effective, nanomolar level detection of multiple metal ions, such as Cu2+, Hg2+, and Ni2+, etc. was achieved exclusively in vesicular aggregates. The optical response towards metal ions, including selectivity and sensitivity, largely depends on the microenvironment around the probe molecules, governed by the nature of the bilayer membrane (polarity, order, interfacial hydration, etc). In zwitterionic membranes, like DPPC, Hg2+-induced fluorescence quenching was witnessed along with red-shifted emission maxima. On the contrary, turn-off responses along with blue-shifted in maxima were noted upon addition of both Cu2+ and Ni2+ ions in the anionic phospholipid vesicle, DPPA. Moreover, an improvement in sensitivity was witnessed when the probe was embedded into phospholipid vesicles with a fluid-like liquid crystalline phase. The larger mobility of the probe molecules on the bilayer membrane, resulting in ease of reorganization, might be the probable reason for this.

Photoswitchable Rhodamine‐Based Multianalyte Sensors for Metal Ion Detection

AbstractWe have developed three azobenzene‐core‐based molecular systems decorated with different numbers of rhodamine units as photoswitchable multianalyte sensors. Exploiting the ring‐opening of the spirolactam part of the rhodamine unit, the resulting fluorescence response, and modulation of it through the photoswitching of azobenzene by light, we utilized them in the detection of multiple metal ions (Fe3+, Fe2+, Sn2+ and Al3+). The binding sites, stoichiometry, binding constants, fluorescent lifetimes and limit of detection (LOD) for each probe have been deduced using appropriate spectroscopic techniques. The limit of detection (LOD) of 5 a, 5 b and 5 c for Fe3+ are found to be 4.2×10−7±7.8×10−9 M, 2.2×10−7±4.6×10−9 M and 1.2×10−7±4.6×10−9 M, respectively. The fluorescence response of the metal‐chelated complex can be manipulated effectively by employing the photoswitching ability of azobenzene that makes them useful as chemosensors for various individual metal ions.

Taking advance of isotropic-to-anisotropic morin-modified silver nanoparticles for simultaneous colorimetric sensing of trivalent chromium and iron ions

Taking into account colorimetric sensing purposes of silver nanoparticles (AgNPs), a convenient system for simultaneous detection of multiple metal ions has been more challenging and less exploited. In the present work, at the same condition (involving AgNPs and morin concentrations, pH and incubation time), morin-modified AgNPs were firstly applied to the simultaneous detection of Cr3+ and Fe3+ ions by naked eyes and ultraviolet-visible spectrophotometry. Furthermore, method validation was also carried out involving specification, selectivity, limits of detection and quantification. The colorimetric sensing mechanisms for such metal ions were admitted via an anisotropic growth of AgNPs, resulting in either larger aggregates due to a coordination complex (Cr3+ ion) or a smaller size due to a redox cycle (Fe3+ ion).

An amino-appended asymmetry salamo-type ratiometric fluorescent probe for efficient relay detection of B4O72−/HCHO in real samples

Development of fluorescent chemical sensors for ratiometric detection of multiple metal ions or anions are highly demanded, but there are still many challenges. Herein, an asymmetry salamo-type ratiometric fluorescent probe G1 were designed and synthesized for highly selective and sensitive detection of B4O72− and formaldehyde (HCHO). The introduction of B4O72− anion into salamo-type fluorescent probe solution induces a significant turn-off fluorescence behavior. Meanwhile, a strong fluorescence feature was again observed when HCHO was successively injected into the formed G1-B probe solution with turn-on style. 1H NMR titration and theoretical calculation proved that the B4O72- coordinates with phenolic oxygen and oxime nitrogen in fluorescent probe G1. B4O72− combination with probe G1 destroys the excited-state intramolecular proton transfer (ESIPT) process and causes fluorescence quenching effect. However, the addition of HCHO leads to a Cannizzaro disproportionation reaction occurred with the G1-B probe, resulting in the fluorescence recovery of the primitive probe molecule. Such probes have excellent selectivity and sensitivity for B4O72− and HCHO, in which the detection limit of sensor towards B4O72− and HCHO was 9.65×10−6 M and 4.66×10−11 M, respectively. Moreover, such sensor was successfully used for monitoring the concentration levels of B4O72− and HCHO in actual sample.

Detection of multiple metal ions in water with a fluorescence sensor based on carbon quantum dots assisted by stepwise prediction and machine learning

Detection of multiple metal ions in water with a fluorescence sensor based on carbon quantum dots assisted by stepwise prediction and machine learning

Carbon dot- and gold nanocluster-based three-channel fluorescence array sensor: Visual detection of multiple metal ions in complex samples

Heavy metal pollution has gradually become one of the most serious problems in global environmental pollution and can invade the environment, food, and medicine, eventually causing irreversible damage to the human body. Herein, we construct a multichannel visual fluorescence array sensor based on N-doped carbon dots (NCDs) and gold nanocluster (AuNCs). The sensor comprehensively considered the aggregation-induced enhanced fluorescence (AIE) effect of AuNCs, the electron transfer (ET) effect of NCDs, and the fluorescence resonance energy transfer (FRET) effect of AuNCs@NCDs. It was further combined with PLSDA and PLSR to realize rapid and accurate detection of multiple metal ions in tap water, traditional Chinese medicine (TCM), and soil. The LODs of Cd2+, Pb2+, and Hg2+ were 0.15 μmol/L, 0.20 μmol/L and 0.09 μmol/L, respectively. Simultaneously, we proposed an adjustable fluorescence spectral logic device to meet the different determination requirements towards heavy metals. The analysis result of metal ions can be directly achieved by the four output types, NOT (0, 0, 0), Cd2+ (1, 1, 0), Pb2+ (1, 0, 0) and Hg2+ (0, 0, 1). More interestingly, Cd2+ and Pb2+ can be removed by simple centrifugation or sedimentation, which can be observed through the Tyndall effect. Accordingly, we not only constructed the sensing method of multiple metal ions but also proposed a new strategy for future research on the migration of heavy metal ions from complex environments to TCM.

A molecular paradigm: “Plug-and-play” chemical sensing and crypto-steganography based on molecular recognition and selective response

Inspired by information processing and communication in nature based on molecular recognition and structural diversity, ongoing efforts aim to development of artificial molecular or nano-systems for sensing, logic computing, and even data storage and safety. However, due to their preparation/functionalization shortcomings (laborious and time-consuming), poor flexibility and compatibility, and limited paradigm, it is still a big challenge whether simple molecules can be used to achieve comprehensive and universal applications from sensing to information storage and protection. Herein, we for the first time demonstrated a molecular paradigm—computer-like “basic input output system (BIOS)” which can realize “plug-and-play” sensing, information encoding, molecular cryptography, and steganography based on a simple artificial molecule (p-nitrophenol, PNP). Based on its molecular recognition and inherent chemical identities, PNP was utilized for colorimetric detection of multiple metal ions (Hg2+, Fe3+, Al3+, Cr3+) and distinguishing their valence (like Cr3+/Cr6+, Fe3+/Fe2+). Interestingly, PNP can achieve the “plug-and-play” fluorescent expansion of detection channels by directly mixing with fluorescent molecules, indicating that PNP molecule can be served as a molecular BIOS with flexibility and compatibility. Impressively, the selectivity embedded in PNP-based BIOS sensing system can be developed as molecular-level double cryptographic steganography to encode, encrypt and hide specific information (like the content of classical literature). This research not only provides a basic idea for building a molecular paradigm with “plug-and-play” flexibility and compatibility, but also provides ideas for the use of molecular sensing and informatization to open up the digitalization of the molecular world.

Carbon Dot- and Gold Nanocluster-Based Three-Channel Fluorescence Array Sensor: Visual Detection of Multiple Metal Ions in Complex Samples

Carbon Dot- and Gold Nanocluster-Based Three-Channel Fluorescence Array Sensor: Visual Detection of Multiple Metal Ions in Complex Samples

Orange-Emissive Sulfur-Doped Organosilica Nanodots for Metal Ion/Glutathione Detection and Normal/Cancer Cell Identification

Developing a single nanosensor capable of detecting multiple metal ions or biomolecules remains a challenge. Here, we successfully developed a sensing platform for the efficient detection of various metal ions with orange-emissive sulfur-doped organosilica nanodots (S-OSiNDs). The S-OSiNDs were prepared via a one-pot solvothermal treatment of urea, citric acid, and bis[3-(triethoxysilyl)propyl]tetrasulfide in N,N-dimethylformamide. The as-prepared S-OSiNDs showed a turn-off fluorescence response toward multiple metal ions including Cu2+, Fe3+, [PdCl4]2–, Ag+, Hg2+, and Bi3+, realizing the rapid and sensitive detection with a very low detection limit of 0.6 nM (for Cu2+). In addition, the metal ion-induced fluorescence quenching of S-OSiNDs could be selectively restored by glutathione (GSH), exhibiting a sensitive GSH detection capability with low detection limits ranging from 0.03 to 0.2 μM. On the basis of the metal ion/GSH-triggered on–off–on regulation of the S-OSiNDs’ fluorescence, we successfully realized the detection of Cu2+, Fe3+, [PdCl4]2–, Ag+, Hg2+, and Bi3+ and achieved cancer/normal cell identification via fluorescence microscopic imaging. Overall, the S-OSiNDs may possess great potential for the detection of multiple metal ions in environmental monitoring and clinical diagnosis, and may also serve as a robust platform for cancer cell imaging and identification because of their capacity of highly sensitive sensing of GSH, which is overexpressed in many cancer cells. Furthermore, the present work also demonstrates that S-OSiNDs can be used for the facile synthesis of metal-incorporated nanoparticles, which we believe may find various applications in the future.

Simultaneous determination of polymetallic ions by ratio second derivative ultraviolet spectrophotometry

Zinc hydrometallurgy is the main zinc smelting process, and the wastewater after its production contains a variety of metal ions, which must be detected and strictly controlled in real time. Aiming at the problem that it is difficult to simultaneously detect multiple metal ions in zinc hydrometallurgy wastewater due to serious spectral overlap and low resolution, a ratio second derivative spectroscopy based on continuous wavelet transform is proposed for simultaneous detection of multiple metal ions. The continuous wavelet transform is found suitable for second order linear derivation to avoid distortion and noise drying. The ratio second derivative method is used to quickly screen out the characteristic wavelength of each metal ion to be detected, and establish a high-precision and low-error analysis model suitable for simultaneous detection of zinc, nickel, cobalt and copper. The linear detection ranges are 10–100 mg/L for zinc, 0.6–6.0 mg/L for nickel, 0.3–3.0 mg/L for cobalt and 0.5–5.0 mg/L for copper. The average relative deviation for zinc, nickel, cobalt and copper was 2.83%, 3.21%, 2.28% and 2.79%, respectively. The work reported here provides a new idea for ion detection of zinc smelting industrial wastewater based on ultraviolet visible spectroscopy, and lays a foundation for online detection of polymetallic ions.

Re-usable colorimetric polymeric gel for visual and facile detection of multiple metal ions

For fast and visual detection of multiple metal ions, herein, a re-usable colorimetric polymeric gel with spiropyran moiety was fabricated. Under ultraviolet light, the spiropyran (SP) moiety could isomerize into the colored merocyanine (MC) isomer and chelate with divalent metal ion (M2+) and form MC-M2+ complexes. Chelated with different metal ions (Ca2+, Co2+, Zn2+, and Cu2+ions), the UV–Vis spectra of the gels could display the specific colorimetric response. When the metal-ions chelated gel was irradiated with Vis light, ions dissociated from MC and released from gel due to the MC moiety isomerized to the SP form. Furthermore, after 7 cycles of alternative UV–Vis irradiations, the gel showed excellent reversible chelation/dissociation of metal ion. The competitive tendency of metal ions to chelate with gel was as following: Cu2+ > Co2+ ≈ Zn2+ > Ca2+, which was in accordance with the density functional theory modeling. Using ionoprinting technology, the gel could achieve repeatability simultaneous detection of multiple metal ions. The light-triggered metal ion chelation/dissociation capability of the gel could be harnessed to construct reusable onsite platform for visual, fast, easy detection of multiple metal ions.

Wearable Porous Au Smartsensors for On-Site Detection of Multiple Metal Ions.

Owing to advantages of miniaturization, convenient integration, flexibility, and real-time monitoring, wearable smartsensors have received numerous attention and greatly developed in various fields. However, there usually appears a contradiction between sensing behaviors and simple fabricated methods, seriously limiting on-site detection of actual samples. In this work, a porous Au-based smartsensor has been in situ prepared by combining screen printing technology and sacrificial template electrodeposition. Thanks to abundant active adsorption sites, multiple metal ions (Pb, Cu, and Hg) can be easily achieved on-site detection by this smart platform with a low limit of detection as well as high sensitivity, excellent selectivity, good stability, repeatability, and bending performance. Significantly, it also exhibits a reliable detective capability in actual liquid cosmetic samples with a portable cellphone, which identically corresponds to standard inductively coupled plasma-mass spectrometry (ICP--MS) evaluation. Therefore, this wearable smartsensor provides a promising platform for artificial intelligence application in future daily life.

Bovine Serum Albumin Protein-Based Liquid Crystal Biosensors for Optical Detection of Toxic Heavy Metals in Water.

A new methodology involving the use of Bovine Serum Albumin (BSA) as a probe and liquid crystal (LC) as a signal reporter for the detection of heavy metal ions in water at neutral pH was developed. BSA acted as a multi-dentate ligand for the detection of multiple metal ions. The LC sensor was fabricated by immobilizing 3 µg mL−1 BSA solution on dimethyloctadecyl-[3-(trimethoxysilyl)propyl]ammonium chloride (DMOAP)-coated glass slides. In the absence of heavy metal ions, a dark optical image was observed, while in their presence, a dark optical image turned to bright. The optical response was characterized by using a polarized optical microscope (POM). The BSA based LC sensor selectively detected toxic metal ions as compared to s block metal ions and ammonium ions in water. Moreover, the limit of detection was found to be very low (i.e., 1 nM) for the developed new biosensor in comparison to reported biosensors.

Calix[4]arene Derivative-Modified Glassy Carbon Electrode: A New Sensing Platform for Rapid, Simultaneous, and Picomolar Detection of Zn(II), Pb(II), As(III), and Hg(II).

The glassy carbon electrode was fabricated with multifunctional bis-triazole-appended calix[4]arene and then used for the simultaneous detection of Zn(II), Pb(II), As(III), and Hg(II). Before applying the square-wave anodic stripping voltammetry, the sensitivity and precision of the modified electrode was assured by optimizing various conditions such as the modifier concentration, pH of the solution, deposition potential, accumulation time, and supporting electrolytes. The modified glassy carbon electrode was found to be responsive up to picomolar limits for the aforementioned heavy metal ions, which is a concentration limit much lower than the threshold level permitted by the World Health Organization. Importantly, the designed sensing platform showed anti-interference ability, good stability, repeatability, reproducibility, and applicability for the detection of multiple metal ions. The detection limits obtained for Zn(II), Pb(II), As(III), and Hg(II) are 66.3, 14.6, 71.9, and 28.9 pM, respectively.

An adjustable dual-emission fluorescent metal-organic framework: Effective detection of multiple metal ions, nitro-based molecules and DMA.

A novel multifunctional Pb(II)-based MOF, [Pb1.5(DBPT)]2·(DMA)3(H2O)4 (1), with excellent chemical stability, was successfully assembled by connecting {Pb2O10} unit with a multi-topic polycarboxylate ligand of 3-(3,5-dicarboxylphenyl)-5-(4-carboxylphenyl)-1-H-1,2,4-triazole (H3DBPT). It exhibits dual fluorescence emissions at 380 nm (λex = 280 nm) and 540 nm (λex = 380 nm), respectively. Through the adjustable dual fluorescence emissions, it could act as a turn-off and turn-on switch for detecting N,N-dimethylacetamide (DMA) molecule. Moreover, Fe3+ ions exert luminescence quenching role on compound 1 at both excitation lengths in water, among which the quenching at λex = 280 nm is of high sensitivity (KSV = 1.2 × 105), and the quenching at λex = 380 nm is of wide-range. The sensing for metal ions of In3+, Zr4+, and Al3+ is also effective at λex = 280 nm, with the KSV constants of 1.6 × 105, 1.6 × 105, and 4.3 × 104, respectively. More importantly, a series of nitroaromatic compounds (TNP, 2,4,6-trinitrophenol; 4-NA, 4-nitroaniline; NB, nitrobenzene) and nitro-based drugs (MNZ, metronidazole; DMZ, dimetridazole) could be detected at both excitation lengths, demonstrating the advantage of broad range response of fluorescence sensing. Thanks to the excellent chemical stability and unusual dual emission luminescence properties for chemical detection of various metal ions, nitro-based molecules and DMA solvent, the Pb-based MOF reported in this work is, therefore, a very promising multi-response sensor.

Ultrasensitive Photoelectrochemical Detection of Multiple Metal Ions Based on Wavelength-Resolved Dual-Signal Output Triggered by Click Reaction.

In this work, a click reaction-triggered wavelength-resolved dual-signal output photoelectrochemical (PEC) biosensor with DNAzymes-assisted cleavage recycling amplification was proposed for sensitive triplex metal ions assay. Substantial DNA fragments azido-S1 and azido-S2, derived from the Pb2+ (target 1) and Mg2+ (target 2) dependent cleavage cycle of DNAzymes, respectively, were grafted efficiently on the same alkynyl-DNA (capture DNA) modified electrode via the Cu2+ (target 3) and ascorbic acid (AA) cocatalyzed click reaction, which thus could besubsequentlyused for immobilization of two different photoactive nanomaterials labeled with single DNA to generate distinguishing dual-signal output for simultaneouslysensitive detection of Pb2+ and Mg2+. Furthermore, the control variable method was used for detecting Cu2+ by altering the concentration of Cu2+ in the click reaction. Owing to the usage of the click reaction and target-converted signal amplifying strategy, the utilization rate of cycle output DNAs was largely increased, significantly improving the detection sensitivity of the proposed approach. As a result, low detection limits down to picomolar were acquired for the detection of Pb2+, Mg2+, and Cu2+, providing a versatile, efficient, and sensitive PEC method for multiple assays of various targets such as metal ions, small molecules, and tumor markers.

Nitrogen-doped carbon dots as fluorescence ON-OFF-ON sensor for parallel detection of copper(ii) and mercury(ii) ions in solutions as well as in filter paper-based microfluidic device.

Due to improper garbage disposal and rapid industrialization, concentrations of different metal ions are rising to toxic levels in natural water sources. Development of novel, selective and sensitive sensors for different metal ions is in high demand for rapid detection and remediation. Herein, we report nitrogen-doped carbon dots (NCDs) with high blue fluorescence, synthesized by a new one-step pyrolytic method using urea and ethylenediaminetetraacetic (EDTA) acid as precursors. The NCDs were used for parallel detection of Hg2+ and Cu2+ ions in aqueous medium through a fluorescence ON–OFF–ON process. The minimum detection limit for Hg2+ and Cu2+ were 6.2 nM and 2.304 nM, respectively, in aqueous medium, which is close to or below the allowed levels of Hg2+ and Cu2+ ions, i.e., 6 ppb and 2 ppm, respectively, in drinking water as per World Health Organisation (WHO). Hg2+ and Cu2+ ions were discriminated with vitamin C (ascorbic acid) and trisodium citrate by a fluorescence turn on process. A filter paper based microfluidic device loaded with NCDs, vitamin C and trisodium citrate was developed using candle wax channels on a filter paper as a proof of principle, projecting NCDs as a promising material for parallel detection of multiple metal ions. The device demonstrated herein is capable of detecting Hg2+ and Cu2+ ions up to 0.1 μM. This simple, low cost, disposable paper-based device will be very useful for rapid onsite analysis.

Three-way DNA junction based platform forultra-sensitive fluorometric detectionof multiple metal ions as exemplified for Cu(II), Mg(II) and Pb(II).

A DNA-based fluorometric method is described for simultaneous determination of multiple metal ions. It is based on recycling cleavage of hairpins by using a three-way DNA junction structure. Three DNA sequences containing a binding region and an enzyme-strand (E-DNA) region are hybridized to form a three-way DNA junction. The enzyme strand regions at the end of the DNA sequence binds to the substrate sequence (S-DNA) at the loop of the hairpin to form typical DNAzyme structures. In the presence of analyte metal ions, the DNAzyme structure thus formed cleaves the loop of hairpins. This is accompanied by a release of fluorescently labeled DNA fragments and by quenching of fluorescence. The detection limits are 35 pM for Cu(II), 2nM for Mg(II), and 8 pM for Pb(II). This method was successfully applied to the simultaneous determination of these ions in spiked human serum. Graphical abstract Schematic presentation of the recycling cleavage of hairpins by using a three-way DNA junction structure. It causes a release of fluorescently labeled DNA fragments and quenching of fluorescence. It was successfully applied to the simultaneous determination of Cu(II), Mg(II) and Pb(II) in spiked human serum.

Multifunctional fluorescent sensors for independent detection of multiple metal ions based on Ag nanoclusters

Selective and sensitive detection of multiple metal ions is significant for biological researches and environmental monitoring, because the abnormal metal ions levels have potential damage to the human body and environment. In this study, a fluorescent sensing platform based on Ag nanoclusters has been established for independent detection of Hg2+, Cu2+, and Fe3+ ions in a solution. The interference of the fluorescence induced by coexistent metal ions was removed by altering buffers with different pH and using different masking agents. Moreover, the detection mechanism is discussed in detail, which provides a valuable reference for the detection of heavy metal ions with metal nanomaterials. This sensor exhibits a high selectivity and sensitivity, and the linear ranges for Hg2+, Cu2+, and Fe3+ detection are 0.05-9, 0.05-18, and 0.1–18 μM with the corresponding detection limits of 12, 27, and 50 nM, respectively. Furthermore, this method was successfully used for analyzing the three metal ions in environmental and biological samples.

Rapid Enrichment and Sensitive Detection of Multiple Metal Ions Enabled by Macroporous Graphene Foam.

Nanomaterials have shown great promise in advancing biomedical and environmental analysis because of the unique properties originated from their ultrafine dimensions. In general, nanomaterials are separately applied to either enhance detection by producing strong signals upon target recognition or to specifically extract analytes taking advantage of their high specific surface area. Herein, we report a dual-functional nanomaterial-based platform that can simultaneously enrich and enable sensitive detection of multiple metal ions. The macroporous graphene foam (GF) we prepared displays abundant phosphate groups on the surface and can extract divalent metal ions via metal-phosphate coordination. The enriched metal ions then activate the metal-responsive DNAzymes and produce the fluorescently labeled single-stranded DNAs that are adsorbed and quenched by the GF. The resultant fluorescence reduction can be used for metal quantitation. The present work demonstrated duplexed detection of Pb2+ and Cu2+ using the Pb- and Cu-responsive DNAzymes, achieving a low detection limit of 50 pM and 0.6 nM, respectively. Successful quantification of Pb2+ and Cu2+ in human serum and river water were achieved with high metal recovery. Since the phosphate-decorated GF can enrich diverse types of divalent metal cations, this dual-functional GF-DNAzyme platform can serve as a simple and cost-effective tool for rapid and accurate metal quantification in determination of human metal exposure and inspection of environmental contamination.