A new Cu-selective self-assembled fluorescent chemosensor based on thiacalix[4]arene

A new ON–OFF fluorescent chemosensor for Cu²⁺ ions was prepared through self-assembly inside Triton X-100 micelles of p-tert-butylthiacalix[4]arene (TCA) and perylene in water solution. This thiacalix[4]arene-based self-assembled fluorescent chemosensor could realize the direct sensing of Cu²⁺ ions in aqueous solution. Addition of Cu²⁺ ions could result in a quenching of the fluorescence emission of perylene inside the micelles, which is ascribed to intramicellar complex-fluorophore electron-transfer or energy-transfer effects induced by the complexation of TCA with the Cu²⁺ ions. Cu²⁺ ions can be detected selectively in the presence of other metal ions (Zn²⁺, Pb²⁺, Cd²⁺, Mn²⁺, Ni²⁺, Al³⁺, Na⁺, K⁺, Ca²⁺ and Mg²⁺) and its concentration in the submicromolar range can be almost linearly determined according to the fluorescence quenching.     

Selective chromogenic and fluorogenic signalling of Hg ions using a fluorescein-coumarin conjugate

A novel, Hg²⁺-selective chemosensor was prepared via Mannich reaction of dichlorofluorescein with piperazinyl-coumarin moiety. The dichlorofluorescein–coumarin derivative exhibited well-defined Hg²⁺-selective chromogenic behavior, indicated by a green to pink colour change in solution, as well as fluorogenic signalling. Significant changes in fluorescence of the dichlorofluorescein subunit were analyzed in reference to the rather constant coumarin emission as an internal standard yielding Hg²⁺ selectivity. The Hg²⁺ selectivity of the chemosensor was not appreciably affected by the presence of common coexisting alkali, alkaline earth, and transition metal ions. The detection limit of the dichlorofluorescein–coumarin conjugate for the determination of Hg²⁺ ions was 4.3 × 10⁻⁶ mol L⁻¹ and the conjugate dye could be used as a chemosensor for the analysis of Hg²⁺ ions in aqueous environments.     

Synthesis of a highly selective bis-rhodamine chemosensor for naked-eye detection of Cu ions and its application in bio-imaging

A bis-rhodamine based fluorescent chemosensor for naked-eye detection of Cu²⁺ with enhanced sensitivity as compared to mono-rhodamine derivative has been synthesized, and its selectivity for Cu²⁺ in the presence of other competitive metal ions (Li⁺, Na⁺, K⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺, Cr³⁺, Mn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Zn²⁺, Cd²⁺, Hg²⁺, and Pb²⁺), and application in bio-imaging are demonstrated.     

Synthesis of a highly selective bis-rhodamine chemosensor for naked-eye detection of Cu2+ ions and its application in bio-imaging

A bis-rhodamine based fluorescent chemosensor for naked-eye detection of Cu²⁺ with enhanced sensitivity as compared to mono-rhodamine derivative has been synthesized, and its selectivity for Cu²⁺ in the presence of other competitive metal ions (Li⁺, Na⁺, K⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺, Cr³⁺, Mn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Zn²⁺, Cd²⁺, Hg²⁺, and Pb²⁺), and application in bio-imaging are demonstrated.     

A highly selective chemosensor for Cu and Al in two different ways based on Salicylaldehyde Schiff

A novel, easily available colorimetric and fluorescent double-sensor 1 based on Salicylaldehyde bis-Schiff has been investigated in this work. The sensor exhibits highly selective and sensitive recognition toward Cu²⁺ in aqueous solution via a naked eye colour change from colourless to yellow and toward Al³⁺ via a significant fluorescent enhancement in ethanol over a wide range of tested metal ions. This represents the first reported Salicylaldehyde Schiff-based sensor capable of detecting both Cu²⁺ and Al³⁺ using two different modes.     

A benzothiazole-based semisquarylium dye suitable for highly selective Hg sensing in aqueous media

A novel semisquarylium dye was synthesized by the reaction between 3,4-dibutoxy-3-cyclobutene-1,2-dione and a benzothiazolium salt and its metal ion sensing properties were investigated using absorption and emission spectroscopy. These misquarylium exhibited high selectivity for Hg²⁺ ions, as compared with Ca²⁺, Pb²⁺, Al³⁺, Ce²⁺, Ba²⁺, Ni²⁺, Cd²⁺, Zn²⁺ and Mg²⁺ ions in DMSO/H₂O (9:1, v/v), which was attributed to the formation of a 2:1 BSQ:Hg²⁺ coordination complex, the formation of which was supported by the calculated geometry of the complex.     

A fluorescent color/intensity changed chemosensor for Fe by photo-induced electron transfer (PET) inhibition of fluoranthene derivative

A fluorescent color/intensity changed fluoranthene derivative chemosensor for Fe³⁺ has been prepared and confirmed by ¹H-NMR, ¹³C-NMR, HRMS, and crystal data, which displays a high selectivity and antidisturbance for Fe³⁺ among environmentally and biologically relevant metal ions. Fluorescence studies show that fluorescent emission peak blue shifts about 100 nm with fluorescent intensity enhancing 75-fold, indicating a Fe³⁺-selective dual-emission behavior. Further study demonstrates the detection limit on fluorescence response of the sensor to Fe³⁺ is down to 10⁻⁷ M range. The fluorescence signals of chemosensor can be restored with o-phenanthroline, showing the binding of chemosensor and Fe³⁺ is really chemically reversible.     

Thiacalixarenes with Sulfur Functionalities at Lower Rim: Heavy Metal Ion Binding in Solution and 2D-Confined Space

Sulfur-containing groups preorganized on macrocyclic scaffolds are well suited for liquid-phase complexation of soft metal ions; however, their binding potential was not extensively studied at the air–water interface, and the effect of thioether topology on metal ion binding mechanisms under various conditions was not considered. Herein, we report the interface receptor characteristics of topologically varied thiacalixarene thioethers (linear bis-(methylthio)ethoxy derivative L², O₂S₂-thiacrown-ether L³, and O₂S₂-bridged thiacalixtube L⁴). The study was conducted in bulk liquid phase and Langmuir monolayers. For all compounds, the highest liquid-phase extraction selectivity was revealed for Ag⁺ and Hg²⁺ ions vs. other soft metal ions. In thioether L² and thiacalixtube L⁴, metal ion binding was evidenced by a blue shift of the band at 303 nm (for Ag⁺ species) and the appearance of ligand-to-metal charge transfer bands at 330–340 nm (for Hg²⁺ species). Theoretical calculations for thioether L² and its Ag and Hg complexes are consistent with experimental data of UV/Vis, nuclear magnetic resonance (NMR) spectroscopy, and single-crystal X-ray diffractometry of Ag–thioether L² complexes and Hg–thiacalixtube L⁴ complex for the case of coordination around the metal center involving two alkyl sulfide groups (Hg²⁺) or sulfur atoms on the lower rim and bridging unit (Ag⁺). In thiacrown L³, Ag and Hg binding by alkyl sulfide groups was suggested from changes in NMR spectra upon the addition of corresponding salts. In spite of the low ability of the thioethers to form stable Langmuir monolayers on deionized water, one might argue that the monolayers significantly expand in the presence of Hg salts in the water subphase. Hg²⁺ ion uptake by the Langmuir–Blodgett (LB) films of ligand L³ was proved by X-ray photoelectron spectroscopy (XPS). Together, these results demonstrate the potential of sulfide groups on the calixarene platform as receptor unit towards Hg²⁺ ions, which could be useful in the development of Hg²⁺-selective water purification systems or thin-film sensor devices.     

A highly selective electrochemical biosensor for Hg using hemin as a redox indicator

A highly selective electrochemical biosensor for the detection of Hg²⁺ in aqueous solution has been developed. This sensor is based on the strong and specific binding of Hg²⁺ by two DNA thymine bases (T–Hg²⁺–T). The hemin worked as a redox indicator to generate a readable electrochemical signal. Short oligonucleotide strands containing 5 thymine (T₅) were used as probe. Thiolated T₅ strands were self-assembled through Au–S bonding on gold electrode. In the presence of Hg²⁺, the specific coordination between Hg²⁺ and thymine bases resulted in more stable and porous arrangement of oligonucleotide strands, so hemin could be adsorbed on the surface of gold electrode and produced an electrochemical signal, which was monitored by differential pulse voltammetry (DPV). The DPV showed a linear correlation between the signal and the concentration of Hg²⁺ over the range 0–2 μM (R² = 0.9983) with a detection limit of 50 nM. The length of probe DNA had no significant impact on the sensor performance. This electrochemical biosensor could be widely used for selective detection of Hg²⁺.     

Characterization of Copper–Cobalt Ores and Quantification of Cu2+, Co2+, Co3+, and Fe3+ in Aqueous Leachates Using UV/Visible Spectrophotometry

Ultraviolet/visible (UV/vis) spectroscopy was used to determine qualitatively and quantitatively Cu²⁺, Co²⁺, Co³⁺, and Fe³⁺ in oxidized Cu–Co ore leachates. The mineralogical and chemical characteristics of the three oxidized Cu–Co ore samples considered were determined using Fourier transform infrared spectroscopy (FTIR), X-ray powder diffractometry (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and X-ray fluorescence spectrometry (XRF). The results showed that Cu and Co in the samples were in the form of carrollite (Co₂CuS₄), malachite (Cu₂CO₃(OH)₂, and heterogenite (CoO(OH)). The samples contained (2.73% Cu and 0.19% Co), (2.82% Cu and 0.07% Co), and (0.03% Cu and 0.05% Co), respectively. Gangues were mainly constituted of quartz, goethite, and hematite. The ultraviolet/visible (UV/vis) results indicated that the wavelengths of absorbance of the metal ions in dilute ethylenediaminetetraacetic acid aqueous solution (pH ≈ 3.5) were Fe³⁺ (293 nm), Cu²⁺ (821 nm), Co³⁺ (344 nm), and Co²⁺ (512 nm). The molar concentrations of the metal ions obtained using the UV/vis method compared well with the results obtained using the atomic absorption spectroscopy (AAS) method. UV/vis spectroscopy was also used to monitor the conversion of Co³⁺ into Co²⁺ using different reducing agents. The results showed that the molar concentration of Co²⁺ in the aqueous solutions increased with the addition of reducing agents, of about 80.95% (copper foil), 61.22% (ferrous sulfate), and 20.35% (sodium sulfite), respectively.     

Conformation-switched chemosensor for selective detection of Hg2+ in aqueous media

A conformation flexible chemosensor for selective detection of Hg²⁺ in aqueous media was achieved by incorporating two well-known rhodamine-6G dyes and a ferrocene group within one molecule. Distinguished from the monosubstituted ferrocene derivative which is previously reported a lack of interaction with Hg²⁺, the title compound was characteristic of two-armed bidendate binding unit. The Hg²⁺ sensing behavior can be switched via the conformation flexibility. The 1:1 sensor/Hg²⁺ binding mode was proposed and supported by the titration experiment and ESI mass spectrum. The fluorescent sensor can display a highly selective response of fluorescence enhancement toward Hg²⁺ and detect the parts per billion (ppb) level of Hg²⁺ in aqueous environment.     

Rhodamine-based fluorescent sensor for mercury in buffer solution and living cells

A novel fluorescent sensor based on thiooxorhodamine B has been prepared to detect Hg²⁺ in aqueous buffer solution. It demonstrates high selectivity for sensing Hg²⁺ with about 383-fold enhancement in fluorescence emission intensity and micromolar sensitivity (K_d = 7.5 × 10⁻⁶ mol L⁻¹) in comparison with alkali and alkaline earth metal ions (K⁺, Na⁺, Mg²⁺, Ca²⁺) and other transition metal ions (Mn²⁺, Ni²⁺, Co²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Ag⁺, Pb²⁺, Cr³⁺, Fe³⁺). Meanwhile the distinct color changes and rapid switch-on fluorescence also provide ‘naked eyes’ detection for Hg²⁺ over a broad pH range. Moreover, such sensor is cell-permeable and can visualize the changes of intracellular mercury ions in living cells using fluorescence microscopy.     

Rhodamine-based fluorescent sensor for mercury in buffer solution and living cells

A novel fluorescent sensor based on thiooxorhodamine B has been prepared to detect Hg²⁺ in aqueous buffer solution. It demonstrates high selectivity for sensing Hg²⁺ with about 383-fold enhancement in fluorescence emission intensity and micromolar sensitivity (K_d = 7.5 × 10⁻⁶ mol L⁻¹) in comparison with alkali and alkaline earth metal ions (K⁺, Na⁺, Mg²⁺, Ca²⁺) and other transition metal ions (Mn²⁺, Ni²⁺, Co²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Ag⁺, Pb²⁺, Cr³⁺, Fe³⁺). Meanwhile the distinct color changes and rapid switch-on fluorescence also provide ‘naked eyes’ detection for Hg²⁺ over a broad pH range. Moreover, such sensor is cell-permeable and can visualize the changes of intracellular mercury ions in living cells using fluorescence microscopy.     

A polymer based fluorescent sensor for Zn detection and its application for constructing logic gates

A polymer-based fluorescent sensor was synthesized by polymerization of (S)-6,6′-dibutyl-3,3′-(di-5-salicylde-ethynyl)-2,2′-binaphthol (M-1) with (R,R)-1,2-diaminocyclohexane (M-2) via nucleophilic addition-elimination reaction. The responsive optical properties of the polymer on transition metal ions were investigated by fluorescence and UV-vis spectra. The polymer (1.0 × 10⁻⁵ mol/L in THF) could emit fluorescence at 550 nm and exhibit high selectivity for sensing Zn²⁺ with 36.1-fold fluorescence enhancement. Three logic gates were designed according to the different fluorescence responses of this polymer sensor to Zn²⁺ and Cu²⁺.     

Radiation Preparation of Conducting Nanocomposite Membrane Based on (Copper/Polyacrylic Acid/Poly Vinyl Alcohol) for Rapid Colorimetric Sensor of Mercury and Silver Ions

In this study, poly acrylic acid/poly vinyl alcohol capped copper as nanocomposite membrane Cu–(PAAc/PVA) has been prepared using gamma radiation. Aqueous solution of 0.2 mol Cu²⁺ ions chemically reduction using ascorbic acid and PAAc/PVA as stabilizer. Cu²⁺ ions could be deposited uniformly on the matrix network of PAAc/PVA membrane. The resulting Cu–(PAAc/PVA) nanocomposites membrane exhibited rapid colorimetric detection of mercury and silver ions associated with notable color changes of the membrane from yellow to pale gray and dark green, respectively. A novel label colorimetric sensor membrane Cu–(PAAc/PVA) has been developed for sensitive detection of Hg²⁺, Ag⁺ ions basis of the UV spectrophotometer data. A detection limit as low as 10^?5 and 10^?6 M of Hg²⁺ and Ag⁺ ions was achieved. This article proved that the Cu–(PAAc/PVA) nanocomposites membrane is exhibited excellent selectivity toward Hg²⁺, Ag⁺ ions. The advantages to the determination of Hg²⁺, Ag⁺ ions using Cu(PAAc/PVA) nanocomposite membrane is simple, low cost, rapid and easy observation by naked eye, the developed Cu–(PAAc/PVA) colorimetric membrane candidate for the detection of toxic Hg²⁺, Ag⁺ ions in environmental and biological samples. The particles size of synthesized Cu was performed using Transmission electron microscopy (TEM) indicates that Cu nanoparticles of size 8 nm are formed by green method. Absorption spectra of Cu nanoparticles deposited in PAAc/PVA at 591 nm confirm the capped of Cu nanoparticles inside PAAc/PVA matrices. The synthesized Cu nanocomposite has been found to be more AC conducting at low frequency than Hg and Ag nanoparticles. The increasing increase in conductivity of membrane can be correlated due to the formation of localized electronic states in polymer matrix due to insertion of Cu nanoparticles.     

Highly Sensitive Fluorescence Probe Based on Functional SBA-15 for Selective Detection of Hg<Superscript>2+</Superscript>

An inorganic–organic hybrid fluorescence chemosensor (DA/SBA-15) was prepared by covalent immobilization of a dansylamide derivative into the channels of mesoporous silica material SBA-15 via (3-aminopropyl)triethoxysilane (APTES) groups. The primary hexagonally ordered mesoporous structure of SBA-15 was preserved after the grafting procedure. Fluorescence characterization shows that the obtained inorganic–organic hybrid composite is highly selective and sensitive to Hg²⁺ detection, suggesting the possibility for real-time qualitative or quantitative detection of Hg²⁺ and the convenience for potential application in toxicology and environmental science.     

Synthesis,Characterization and Theoretical Calculations of a New Fluorescent Probe for Detection Cu2+

A novel rhodamine-based probe (RP1) was synthesized and characterized as a colorimetric chemosensor with high selectivity and sensitivity in biological systems toward Cu²⁺ over other cations tested. RP1 showed low detection limit for copper. The binding between RP1 and Cu²⁺ was confirmed to be stoichiometric. The recognition process was reversible. We also performed the density functional theory (DFT) calculation to have more understanding of structure, molecular and electronic.     

A fluorescein derivative FLTC as a chemosensor for Hg2 + and Ag+ and its application in living-cell imaging

FLTC was synthesized and used as a fluorescent chemosensor to detect Hg^2 +. It showed high selectivity toward Hg^2 + over many heavy metal ions in an ethanol–H₂O (3:2, v/v, HEPES buffer, 0.5 mM, pH 7.15) solution with a detection limit of 0.21 μM. After complexation with Hg^2 +, FLTC showed extremely high selectivity toward Ag⁺ with a detection limit of 0.009 μM. Therefore, detection of Hg^2 + and Ag⁺ could be realized using FLTC and the FLTC–Hg^2 + complex, respectively. Cytotoxicity assays and fluorescence microscopy analysis showed that FLTC could be used as a fluorescent probe to detect Hg^2 + and Ag⁺ in L-02 human liver cells.     

A novel rhodamine-based fluorescent and colorimetric “off-on” chemosensor and investigation of the recognizing behavior towards Fe

A novel rhodamine based probe has been synthesized as an “off-on” chemosensor for Fe³⁺. Upon coordination with Fe³⁺, the probe displayed good brightness and fluorescent enhancement. A linear relationship was observed to exist between the relative fluorescence intensity of this probe and the concentration of Fe³⁺ in the range of 5 μM-20 μM with a detection limit of 5 μM. It offered highly sensitive toward Fe³⁺ over other ions. The recognizing behaviors toward Fe³⁺ have been investigated both experimentally and computationally. It can be expected that Fe³⁺ coordinated with the N atom of thiazole moiety in the probe accompanied by the transferring of electrons of the phenylthiazole resulted in the opening of the spiro-ring.     

Chromogenic sensing of Cu(II) by imino linked thiacalix[4]arene in mixed aqueous environment

Thiacalix[4]arene based imino receptors 4–5 carrying azophenol appendage have been synthesized and studied for their binding abilities towards different metal ions (Li⁺, Na⁺, K⁺, Cd²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Ag⁺, Pb²⁺ and Hg²⁺). Receptor 4 showed selective chromogenic sensing for Cu²⁺ ions in mixed aqueous conditions (THF:H₂O, 9:1 v/v).