Fluorescent Sensor For Cu2 Research Articles

Fluorescent sensor of copper(II) ions based on PMBA microtubes with 4-methoxy-1,8-naphthalimide groups

In this article, a high performances hydrophilic tubular fluorescent sensor for Cu(II) detection was fabricated via immobilizing fluorophore 4-methoxy-1,8-naphthalimide groups on poly(N, N′-methylene bisacrylamide) (PMBA) microtubes. The modified polymer microtubes were characterized fully by SEM, FT-IR, EDS mapping, fluorescence microscope and fluorescence spectrometer. This fluorescent sensor displayed high fluorescence emission intensity at 457 nm under irradiation, and exhibited an obvious selective quenching effect in the presence of Cu(II) alone or with a variety of other cations in aqueous solution. Based on the fluorescence intensities before and after quenching, the concentration of Cu(II) could be calculated accurately. Moreover, the fluorescent sensor could be regenerated using ethylene diamine tetraacetic acid (EDTA) as the chelating agent. The regenerated sensor could be reused for many times without performance deteriorate. The mechanism of quenching and regenerating, and the role of the tubes were discussed.

A Fluorescent Sensor for Cu2+ Ion with High Selectivity and Sensitivity Based on ICT and PET.

A novel fluorescent sensor (L) based on 1,8-naphthalic anhydride has been developed which can selectively detect Cu2+ in CH3CN medium over other metal ions at 408nm in the fluorescence spectra. When Cu2+ was added into L, L showed fluorescent turn-off by coordinating with Cu2+. A fresh absorption band was found at the position of 290nm as was a red-shifted absorption band from 356nm to 376nm in UV-vis spectra which might be attributed to the intramolecular charge transfer (ICT). Meanwhile, L-Cu2+ showed fluorescence quenching via photoinduced electron transfer (PET). The complexation ratio was proposed to be 1:1 which was determined by Job's plot, fluorescence titration and 1H NMR titration. The detection limit was 9.1 × 10-8mol·L-1, a satisfying level to detect Cu2+ in the micromolar scale. Corresponding molecular geometries, orbital energies and electron contributions of sensor L were calculated by the DMol3 program package using the density functional theory.

Aqueously synthesized color-tunable quaternary Cu-In-Zn-S quantum dots for Cu(II) detection via mild and rapid cation exchange

Non-cadimum photoluminescent I−III−VI semiconductor nanocrystals have attracted increasing attention due to their low toxicity, extraordinary optical and electronic properties. Herein, water-soluble quaternary Cu-In-Zn-S quantum dots (CIZS QDs) with tunable emission from 535 nm to 645 nm were successfully synthesized via ecofriendly one-pot aqueous method. The full width at half-maximum (FWHM) of the emissions are about 68 nm–88 nm, which are rather narrow among Cu-based semiconductors and preferred to facilitate improving color purity. The photoluminescence of water-soluble QDs was enhanced by ZnS coating with the absolute quantum yield (QY) up to 30.8%. Further, a novel fluorescent sensor for Cu2+ detection was developed based on the alteration of intrinsic optical properties of the CIZS/ZnS QDs after cation exchange at room temperature within 10 min, presenting a linear range of 0.020–20 μM and a detection limit down to 6.7 nM. Mechanism studies revealed that the QDs served as the template for cation exchange, through UV–vis absorption and fluorescence spectra in combination with the chemical composition and time-resolved photoluminescence decay analysis. Ions interference experiments demonstrated the good selectivity of the QDs towards Cu2+ and the sensor showed comparable accuracy to ICP-AES method as well as good performance in real sample detection, manifesting the reliability of the current strategy for sensing Cu2+ mildly and rapidly.

A reversible fluorescence “ON–OFF–ON” sensor for sequential detection of F− and Cu2+ ions and its application as a molecular-scale logic device and security keypad lock

A new azoimine receptor, R1, was synthesized by Schiff base condensation of 4-(4-butylphenyl) azophenol and 2,6-diaminopyridine and acts as a colorimetric and fluorometric chemosensor for F− and also toward Cu2+ ions in aqueous environment. UV–Vis absorption and fluorescent emission spectra were employed to study the sensing process. Emission study was performed to examine the dual sensing ability of the obtained probe with sequential addition of F− followed by Cu2+ and vice versa. The receptor is an efficient “ON–OFF” fluorescent probe for the fluoride ion. Also, R1 + F− operated as an “OFF–ON” fluorescent sensor for Cu2+ ions. Considering emission intensity and absorption wavelength for F− and Cu2+ ions, a molecular system was developed with the ability to mimic the functions of XNOR logic gating on the molecular level. In addition, R1 behaved as a molecular security keypad lock with F− and Cu2+ inputs. The keypad lock operation is particularly important, as the output of the system depends not only on the proper combination but also on the order of input signals, creating the correct password that can be used to “open” this molecular keypad lock through strong fluorescence emission at 460 nm.

A ratiometric fluorescent sensor for tracking Cu(I) fluctuation in endoplasmic reticulum

A two-photon ratiometric fluorescent sensor for Cu+ in endoplasmic reticulum (ER), CNSB , was developed via coumarin/ASBD integration based on FRET mechanism. In solution, CNSB shows reversible, highly-specific ratiometric response to Cu+. Moreover, CNSB exhibits suitable K d value, suggesting the possibility of detecting Cu+ in the living cells. The probe can enter the MCF-7 cells easily and specifically locates in the ER. The highly specific ratiometric response of CNSB toward Cu+ in MCF-7 cells provides the sensor the capacity to visualize both exogenous and endogenous Cu+ in the ER via fluorescence imaging. Next, CNSB was utilized to detect the fluctuation and distribution of Cu+ under ER stress in MCF-7 cells, which confirmed directly the relationship between Cu+ enhancement and ER stress. Meanwhile, the two-photon ability of coumarin facilitated the sensor to visualize Cu+ fluctuation via two-photon fluorescence imaging. In addition, the spatial distribution of Cu+ in the heart slice of the 14-day-old rat was demonstrated using CNSB . This study demonstrates the promising potential of CNSB in clarifying the Cu+-dependent signaling in the ER stress-related diseases.

A fast, highly selective and sensitive colorimetric and fluorescent sensor for Cu2+ and its application in real water and food samples.

A new oligothiophene functionalized Schiff base sensor 3TDC has been successfully designed and synthesized. Sensor 3TDC exhibited "naked-eye" colorimetric and selective "on-off" fluorescence response toward Cu2+ with high selectivity and sensitivity within a wide pH range. The binding ratio of the sensor 3TDC and Cu2+ was determined to be 1:1 through fluorescence titration, Job's plot, 1H NMR titration, FTIR and DFT studies. The detection limit is calculated to be as low as 2.81 × 10-8 M, which is much lower than the allowable level of Cu2+ in drinking water set by U.S. Environmental Protection Agency (~20 μM) and the World Health Organization (~30 μM). The binding constant (Ka) of Cu2+ to sensor 3TDC was found to be 2.52 × 104 M-1. Sensor 3TDC for Cu2+ detection exhibited fast fluorescence response within 30 s and high anti-interference performance. Moreover, sensor 3TDC could be used as an effective fluorescent sensor for detecting Cu2+ ions in various real water and food samples with good accuracy and high precision.

Natural Peptide Probe Screened for High-Performance Fluorescent Sensing of Copper Ion: Especially Sensitivity, Rapidity, and Environment-Friendliness

Copper, one of the most important metal elements, has been a new favorite in research areas. However, the Cu2+ detection strategy with high-efficient and biocompatibility maintains importance. Here, we made effort to develop a new sensor with above advantages for Cu2+ detection. By virtue of rich coordination sites (amidogen and carboxyl) and fluorescence property of aromatic amino acids that which are also essential for living organism, monomers and combinations of them are designed to interact with Cu2+, attractively, the short peptide of tryptophane–phenylalanine (Trp–Phe) held stronger fluorescence emission and displayed much more significant response to Cu2+ than other molecules; thus, Trp–Phe was screened as a new fluorescent sensor for Cu2+ detection. It had a rapid response to the target ion via a coordination-mediated PET effect, the signal change reached the maximum within 10 s; cell proliferation experiments verified that the screened peptide had excellent biocompatibility, implying that it had...

N,N-Bis(2-pyridylmethyl)amine-Based Truxene Derivative as a Highly Sensitive Fluorescence Sensor for Cu2+ and Ni2+ Ion

<i>N</i>,<i>N</i>-Bis(2-pyridylmethyl)amine-Based Truxene Derivative as a Highly Sensitive Fluorescence Sensor for Cu²⁺ and Ni²⁺ Ion

Sequential detection of Cu2+ and cysteine using an imidazole‐based chemosensor in aqueous solution

A highly substituted imidazole‐based colorimetric and fluorogenic chemosensor, 2‐methoxy‐4‐(4,5‐diphenyl‐1H‐imidazol‐2‐yl)phenol (L), for the detection of Cu2+ ion and subsequent colorimetric detection of an amino acid, cysteine, was investigated. L exhibited a distinct color change from colorless to red in the presence of Cu2+ in an aqueous medium. The L‐Cu2+ complex can also be used to detect cysteine by the naked eye over a series of amino acids. The receptor L behaves as a highly selective colorimetric and fluorescent sensor for Cu2+ ions at concentrations as low as 4.33 and 2.25 μM, respectively. These values are much less compared to the WHO recommended limit of 30 μM for Cu2+ in drinking water. From Job's plot and the ESI‐MS spectrum, a 1:1 stoichiometric complex between L and Cu2+ ions can readily be reckoned. This binding was also substantiated by the EPR spectrum and magnetic susceptibility measurements. Additionally, the binding of L with Cu2+ ions was also manifested in the detection of B16F10 cells. This was substantiated through fluorescence microscopy. The spectrum of the L‐Cu2+ entity was also attempted to reproduce theoretically. The probable structure of this was also propounded through Density Functional Theory.

Nitrogen and phosphorus co-doped carbon dots derived from lily bulbs for copper ion sensing and cell imaging

A straightforward, rapid, and environmentally-friendly technique was developed for the synthesis of nitrogen and phosphorus co-doped fluorescent carbon dots (CDs) with the use of lily bulbs (LB) as raw materials. The as-synthesized LB-CDs showed high stability in aqueous solution and high fluorescence with a quantum yield (QY) of 17.6%. The LB-CDs were then used as a fluorescence sensor for Cu2+ ion detection based on the Cu2+-ion-stimulated fluorescence quenching of LB-CDs. The synthesized LB-CDs demonstrated exceptional selectivity and sensitivity to Cu2+ ions, with a limit of detection of 12.8 nM and a linear detection range of 0.05–2.0 μM. The synthesized LB-CDs were also applied for the detection of Cu2+ ions in real water samples. Moreover, the LB-CDs exhibited low cytotoxicity, which is suitable for fluorescence-based analysis and cell imaging.

A novel jointly colorimetric and fluorescent sensor for Cu2+ recognition and its complex for sensing S2− by a Cu2+ displacement approach in aqueous media

In this work, a simple and easily synthesized Schiff-based derivative colorimetric and fluorescent sensor (1), 4-dimethylamino-benzoic acid (2-imidazole formaldehyde)-hydrazide, was obtained for the detection of Cu2+ and S2−. The compound 1 exhibited dual spectral responses to Cu2+, that is, vivid color change and fluorescence enhancement in the presence of Cu2+. The detection limits were valued as 0.46 μM and 15 nM according to absorption and fluorescent response, respectively. Both of them are below the World Health Organization (WHO) guidelines for drinking water (31.5 μM). In addition, the ensemble (1-Cu2+) selectively and sensitively detected a low concentration of S2−. As the addition of S2− instantly removed Cu2+ from the ensemble (1-Cu2+) resulting in a color change from yellow to colorless and a “turn-off” fluorescent response. The detection limit for S2− was estimated as 0.12 μM (from fluorescent method) and 0.68 μM (from absorption method), respectively, each of which was also lower than the maximum allowable level of S2− (15 μM) in drinking water defined by the WHO. The binding process was confirmed via UV–vis absorption, fluorescence measurements, 1H NMR, mass spectroscopy and density functional theory calculation. What's more, successful practical application of test paper is used to inspect the S2− which means the convenient and rapid assay in real samples can be achieved.

A selective fluorescent sensor for Cu(II) ion in ethanol and acetone based on BODIPY

A selective fluorescent sensor for Cu(II) ion in ethanol and acetone based on boradiazaindacene (BODIPY) has been studied. The selectivity towards Cu(II) ion is good over Ag(I), Cd(II), Fe(III), Hg(II), Ni(II), Pb(II), and Zn(II) ions, only Fe(III), Hg(II) and Ni(II) ions showed a slight interference. The solution showed strong fluorescence intensity after addition of triethanolamine, indicating that the Sensor 1-Cu(II) complex could be reversed by triethanolamine.

Colourimetric and fluorimetric metal ion chemosensor based on a benzimidazole functionalised Schiff base

Herein we present the interaction of benzimidazole based Schiff base 1 with different metal ions studied by absorption and fluorescence spectroscopies and computational modelling. Compound 1 exhibits changes in spectroscopic properties upon chelation with specific metal ions. Its strong absorption band at 425 nm is significantly red shifted (Δλ = 30 nm) only upon the complexation with Al3+, an effect observable by a naked eye as a colour change from light- to dark-yellow. Of the metal ions investigated, only Al3+ caused any increase in the fluorescence intensity of 1. All other metal ions, including K(I), Na(I), Ag(I), Li(I), Zn(II), Co(II) and Hg(II), showed a negligible fluorescence response, while Cu(II) and Fe(III) significantly decreased the fluorescence intensity. Therefore, system 1 is a promising colourimetric sensor for Al3+, and a fluorescence sensor for Cu2+ and Fe3+ ions. Computational analysis revealed that 1 is unionized in ethanol solution, while it becomes di-deprotonated to 12– upon the complexation with Al3+. This changes the electronic structure of 1 and leaves no acidic hydrogen atoms to allow the ESIPT process. On the other hand, the presence of monovalent metal cations induces only mono-deprotonation to 1–, which turns out to be an insufficient electronic change to be spotted in the recorded spectra.

Dansyl Based "Turn-On" Fluorescent Sensor for Cu2+ Ion Detection and the Application to Living Cell Imaging.

A new "turn-on" fluorescent chemosensor based on dansyl derivative was prepared for Cu2+ ion sensing. Hydroxyl, imine and azomethine groups in Schiff base derived compound 1 were deliberately introduced for facilitating the binding of Cu2+ ion. Of screen metal ions, compound 1 showed a high degree of selectivity toward Cu2+ ion. Other interfering metal ions did not affect the fluorescence intensity of compound 1, except Hg2+ and Fe3+ ions exhibited a significant degree of fluorescence quenching. Upon binding of Cu2+ ion, compound 1 displayed a chelation enhanced fluorescence (CHEF) resulting in increasing of the fluorescence intensity. The molecular optimized geometry indicated the binding ratio between compound 1 and Cu2+ ion at 1:1 with the binding constant of 1.68 × 10- 7 M- 1. The optimized condition for sensing ability of compound 1 with a detection limit of 5 × 10- 7 M was found at the physiological pH 7.2 with the excitation wavelength of 366nm. Due to no cytotoxicity and good photophysical properties, compound 1 was extended its application for the detection of Cu2+ ion in Vero cells. Compound 1 could be potentially used as an intracellular fluorescent chemosensor for tracking Cu2+ ion. Graphical Abstract.

Synthesis of green fluorescent carbon quantum dots using waste polyolefins residue for Cu2+ ion sensing and live cell imaging

The residue obtained from the pyrolysis of waste polyolefins, has been used for preparation of highly green-visual fluorescent carbon quantum dots (CQDs) by a simple one step hydrothermal approach consisting of ultrasonic-assisted chemical oxidation. These CQDs were characterized by UV–vis absorption spectroscopy, fluorescence spectroscopy, TEM, XRD, and FTIR. The CQDs possessed high stability in aqueous solution and exhibited strong fluorescence with quantum yield of 4.84%. The use of these CQDs as a fluorescent sensor for Cu2+ ions detection has been explored. The synthesized CQDs have excellent selectivity and sensitivity towards Cu2+ ions with a limit of detection (LOD) 6.33nM and linear detection range of 1–8.0μM. These CQDs have also shown their utility for analysis of real water samples and have the potential to use for triple negative breast cancer cells (MDA-MB 468 cells) imaging.

A new Schiff base as a turn‐off fluorescent sensor for Cu2+ and its photophysical properties

A new Schiff base receptor 1 was synthesized and its photophysical properties were investigated by absorption, emission and excitation techniques. Furthermore, its chromogenic and fluorogenic sensing abilities towards various metal ions were examined. Receptor 1 selectively detects Cu2+ ion through fluorescence quenching and detection was not inhibited in the presence of other metal ions. From fluorescence titration, the limit of detection of receptor 1 as a fluorescent 'turn-off' sensor for the analysis of Cu2+ was estimated to be 0.35μM.

An acac-BODIPY dye as a reversible “ON-OFF-ON” fluorescent sensor for Cu2+ and S2- ions based on displacement approach

An ON-OFF-ON type BODIPY-based fluorescent sensor bearing acetylacetone (acac) moiety was synthesized and characterized. The molecule revealed ON-OFF type fluorescence behaviour with high selectivity toward Cu2+ ion without any interference from other cations. Once combined with Cu2+, it displayed high specificity for S2- anion with in situ recovery of the quenched fluorescence, based on the displacement approach. DFT studies of the dye and its Cu2+ complex indicated an efficient relocation of electron charge density from dye to Cu2+ in LUMO rationalizing the selective quenching of dye fluorescence upon association with Cu2+ ion. The acac-conjugated BODIPY dye was also effective to detect the designated ions in live cells.

Coumarin Based Highly Selective "off-on-off" Type Novel Fluorescent Sensor for Cu2+ and S2- in Aqueous Solution.

Solvent free synthesis of 6,7-dihydroxy-3-(3-chlorophenyl) coumarin (CFHC) was designed and obtained by the interaction of 2-(2,4,5-trimethoxyphenyl)-1-(3-chlorophenyl)acrylonitrile with pyridinium hydrochloride in the presence of silica gel by using microwave irradiation. The characterization of CFHC was confirmed by FT-IR, 1H, 13C, 13C-APT and 2D HETCOR spectroscopy methods. The optical behavior of CFHC towards metal ions was investigated by UV-visible and fluorescence spectroscopy. CFHC showed "on-off" type fluorescence response towards Cu2+ with high selectivity in aqueous solution (CH3CN/H2O, 9/1, v/v). Once binding with Cu2+, CFHC-Cu2+ complex also displayed high selectivity for sulfide, resulting in "off-on" type sensing of sulfide anion. Graphical abstract Visual fluorescence changes upon addition of various metal ions (5.0 eq.) to CFHC in CH3CN/H2O (90:10, v/v) under UV excitation (365 nm).

A colorimetric and fluorescent sensor for Cu2+ and F− based on a diarylethene with a 1,8-naphthalimide Schiff base unit

A new photochromic diarylethene with a 1,8-naphthalimide Schiff base unit has been synthesized, which exhibited typical photochromism and fluorescent switching properties by photoirradiation with high selectivity to Cu2+ and F−. With Cu2+, the diarylethene color changed from greenish yellow to colorless with a decrease in fluorescence intensity at 542nm. And a binding constant of 3.13×104Lmol−1 for the diarylethene-Cu2+ complex was calculated from the Benesi-Hildebrand plot. In the presence of F−, absorption of the diarylethene showed redshift with a color change from greenish yellow to blue.

Naked-eye fluorescent sensor for Cu(II) based on indole conjugate BODIPY dye

A novel on/off fluorescent indole/BODIPY-based Cu2+ chemosensor (3) was synthesized by Knoevenagel condensation of BODIPY derivative 1 with 2-methyl-indole-3-carbaldehyde 2. The identity of compound 3 was confirmed by 1H NMR, 13C NMR, FT-IR, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and single crystal X-ray diffraction techniques. Fluorescent chemosensor (3) is found to be highly selective and sensitive for detection of Cu2+ with a color change from purple to yellow. The optical sensor features for the Cu2+ complex of 3 were investigated by UV–Vis and fluorescence spectroscopy. The addition of Cu2+ caused quenching of fluorescence intensity and the detection limit was calculated to be 0.124μM. Also, the stoichiometry ratio of 3+Cu2+ was obtained 2:1 by Job’s plot. Live cell image, flow cytometry and cytotoxic properties of compound 3 were examined.