A sensitive probe for the detection of Zn(II) by time-resolved fluorescence

A new, highly sensitive fluorescent sensor for Zn(II) ion (a tris(2-pyridylmethyl)amine derivative) shows very strong binding and Zn(II) concentration-dependent biexponential time-resolved fluorescence (TRF) decay profiles that can be used for ratiometric estimates of Zn(II) concentrations. The ligand-metal complexes were characterized in solution by spectroscopic techniques and in the solid state by X-ray crystallography. The TRF studies revealed that the sensor aggregates in the absence of Zn(II) in a ligand concentration-dependent manner, a complication that is discerned by TRF but not by steady-state fluorescence ratiometric sensing techniques. It is shown that the same TRF methods are highly useful for monitoring Zn(II) concentrations in A549 epithelial lung cells in vitro and that the results were consistent with those in solution.     

Selective detection of mercury(II) and methylmercury(II) via coordination-induced emission of a small-molecule probe

Mercury is one of the major toxic pollutants and has many adverse effects on human health. The main mercury species in the environment or in living organisms are inorganic mercuric ion (Hg²⁺) and organic methylmercury (CH3Hg+). Detection of the two mercury ions is a particularly active topic in the molecular sensing field during the past decade. However, efficient sensors that can sensitively detect and discriminate the two species are rare. In this work, we adopt the concept of restriction of intramolecular rotations which is the basis of aggregation induced emission, and design a molecular probe with pyridyl group as the chelating unit and 1,8-naphthalimide as the fluorescent unit for the detection of both Hg²⁺ and CH₃Hg⁺. When the probe is free in solution, it exhibits weak fluorescence because free intramolecular rotations of the 1,8-naphthalimide moieties non-radiatively annihilate its excited state. However, upon coordination with Hg²⁺ or CH₃Hg⁺, the rotation of 1,8-naphthalimide moieties would be restricted due to the chelation between 1,8-naphthalimide and Hg²⁺ or CH₃Hg⁺, leading to significantly enhanced fluorescent emission. The response induced by Hg²⁺ is much stronger than CH₃Hg⁺; but for specific detection of CH₃Hg⁺, we introduced a T-rich DNA fragment which could completely mask Hg²⁺ in solution. Furthermore, we have employed the sensor for confocal imaging of Hg²⁺ and CH₃Hg⁺in immobilized cells. We expect the probe design tactics can be generally useful for sensing many other analytes.     

Separation and detection of angiotensin peptides by Cu(II) complexation and capillary electrophoresis with UV and electrochemical detection

The use of capillary electrophoresis (CE) with on-capillary Cu(II) complexation for the determination of angiotensin and its metabolites is described. The resulting copper-peptide complexes can be detected using either UV or electrochemical (EC) detection. Optimal reaction and separation conditions for the angiotensin peptides were first determined using CE with UV detection. With UV detection, the limit of detection (signal-to noise ratio S/N = 3) for native angiotensin II was 18 microM, while the limit of detection (LOD) obtained for the copper-angiotensin II complex is 2 microM. CE with EC detection was then evaluated, yielding significantly lower LODs--2 microM for native angiotensin II and 200 nM for the copper-angiotensin II complex. The addition of copper to the run buffer improved the separation and sensitivity for both CE-UV and CE-EC detection. The method was demonstrated by monitoring the conversion of angiotensin I to angiotensin II in plasma via angiotensin-converting enzyme (ACE) and subsequent inhibition of ACE by captopril.     

Coumarin-based tripodal chemosensor for selective detection of Cu(II) ion and resultant complex as anion probe through a Cu(II) displacement approach

In this paper, a novel tripodal fluorescent receptor based on naturally occurring coumarin was synthesized and its ionic recognition properties were fully investigated by spectroscopic techniques. As revealed by the results, tripodal 1 exhibits excellent selectivity toward copper(II) by forming a 1:1 complex with triazole N as the main binding sites. And the resulted 1·Cu²⁺ complex shows recognition ability toward H₂PO₄^? by metal displacement approach. The recognition mechanism was further investigated by computer calculation.     

A new bis(pyrenyl)azadiene-based probe for the colorimetric and fluorescent sensing of Cu(II) and Hg(II)

A novel colorimetric and fluorescent chemosensor 2, made up of two pyrene units connected by a 2-aza-1,3-butadiene ionophore, was designed and prepared for the selective detection of Cu²⁺ and Hg²⁺ in the presence of other metal cations. This molecular sensor exhibits substantial colour changes and fluorescence enhancement upon complexation with these metal cations in acetonitrile solutions, with detection limits in the order of 10⁻⁶ M. Job's plots revealed a 1:1 stoichiometry rationalized by theoretical DFT calculations.     

A novel method for Co(Ⅱ) and Cu(Ⅱ) analysis by capillary electrophoresis with chemiluminescence detection

Based on the fact that some metal ions can catalyze the chemiluminescence(CL)reaction of luminol with K_3Fe(CN)_6,a novel capillary electrophoresis CL method was developed for the determination of Co(Ⅱ)and Cu(Ⅱ).The separation was carried out with a 10 mmol/L sodium acetate solution containing 0.8 mmol/L luminol and 2.0 mmol/Lα-HIBA(adjusted to pH 4.8 by HAc solution).The post-capillary reagent was 2.0 mmol/L K_3Fe(CN)_6 which was adjusted to pH 13.0 by NaOH solution.Under the optimum conditions,the detection limits(S/N=3)for Co(Ⅱ)and Cu(Ⅱ)were 7.5×10~(-11)mol/L and 7.5×10~(-9)mol/L,with the linear range of 7.5×10~(-9)mol/L to 1.0×10~(-6)mol/L and 7.5×10~(-8)mol/L to 5.0×10~(-5)mol/L, respectively.     

A Novel Fluorescent Aminoacid Designed for Fluorometric Detection of Cu （Ⅱ）

A fluorescent aminoacid was designed for selective and sensitive detection of Cu(II) in aqueous solution. The designing of this Cu(II) fluorescent chemosensing molecule, N ± (1‐naphthyl). aminoacetic acid (NAA), was based on the binding of Cu(II) to aminoacetic acid and the novel charge transfer photophysics of 1‐aminonaphthalenes. The fluorescence of NAA was found quenched by Cu (II) and several other metal ions of similar electronic structure such as Co(II), Ni(II) and Zn(II). The quenching was shown to occur via electron transfer within the metal‐NAA complex, which required an optimal combination of high binding affinity and favorable redox properties of the components in the metal‐NAA complex and hence afforded selective fluorometric detection of Cu(II). The calibration graph obeyed Stern‐Volmer theory and was shown for Cu(II) over the range of 0–2.75 ± 10–⁴ mol/L. The quenching constant of Cu(II) was measured as 8.0 ± 10³ mol/L that was two orders of magnitude higher than those of Co(II), Ni(II) and Zn(II). The 3SD limit of detection for Cu(II) was 8.00 ± 10^?6 mol/L with a coefficient of variation of 1.65%. Linear range for quantitative detection of Cu(II) was 2.67 ± 10^?5‐2.75 ± 10^?4 mol/L. The method was applied to synthetic sample measurements which gave recoveries of 105%‐112%.     

Fluorescent Detection of Cu(Ⅱ) by Chitosan-based AIE Bioconjugate

Detection of Cu(Ⅱ) is very important in disease diagnose, biological system detection and environmental monitoring. Previously, we found that the product TPE-CS prepared by attaching the chromophores of tetraphenylethylene(TPE) to the chitosan(CS) chains showed excellent fluorescent properties. In this study, we tried to use TPE-CS for detecting Cu(Ⅱ) because of the stable complexation of CS with heavy metals and the luminosity mechanism of the Restriction of Intramolecular Rotations(RIR) for aggregation-induced emission(AIE)-active materials. The fluorescence intensity changed when TPE-CS was contacted with different metal ions, to be specific, no change for Na~+, slightly increase for Hg~(2+), Pb~(2+), Zn~(2+), Cd~(2+), Fe~(2+), Fe~(3+) due to the RIR caused by the complexation between CS and metal ions. However, for Cu~(2+), an obvious fluorescence decrease was observed because of the Photoinduced-Electron-Transfer(PET). Moreover, we found that the quenched FL intensity of TPE-CS was proportional to the concentration of Cu(Ⅱ) in the range of 5 μmol/L to 100 μmol/L, which provided a new way to quantitatively detect Cu(Ⅱ) . Besides, TPE-CS has excellent water-solubility as well as absorbability(the percentage of removal, R = 84%), which is an excellent detection probe and remover for Cu(Ⅱ) .     

Electrochemical detection of Cu(I) and Cu(II) in styrene media

A method is described to detect Cu(II) and Cu(I) added as bromide simultaneously in styrene solution containing tetrahexylammoniumperchloraat (THAP) as supporting electrolyte. It was found that Cu(II) and Cu(I) behave similarly in styrene and in aqueous solution. Reduction of Cu(II) and Cu(I) to metallic copper, as well as oxidation of Cu(I) to Cu(II) and the dissolution of a deposited metallic copper layer are observed. Ohmic drop problems were circumvented by adding THAP to the styrene solution and using ultramicro electrodes. The simultaneous detection of Cu(II) and Cu(I) is based on recording a cyclic voltammetric curve in a mixture of these compounds and calculating their concentration from the cathodic limiting current obtained at −0.80 V vs. RE and the anodic stripping peak corresponding to the dissolution of metallic copper. A detection limit of 2.0×10⁻⁴ mol l⁻¹ was obtained for both Cu(II) and Cu(I) and reproducible results were obtained concerning sensitivity and stability of the calibration curves.     

UV, VUV and soft X-ray photoabsorption of dimethyl ether by dipole (e,e) spectroscopies

Absolute UV and VUV photoabsorption oscillator strengths (cross-sections) for the valence shell discrete and continuum regions of dimethyl ether (CH₃OCH₃, DME) have been measured from 5 to 32 eV using high resolution (HR) (0.05 eV f.w.h.m.) dipole (e,e) spectroscopy. A wide-range spectrum, spanning the UV, VUV and soft X-ray regions, from 5 to 200 eV has also been obtained at low resolution (LR) (1 eV f.w.h.m.), and this has been used to determine the absolute oscillator strength scale by employing valence shell Thomas–Reiche–Kuhn (i.e., S(0)) sum-rule normalization. The presently reported HR and LR absolute photoabsorption oscillator strengths are compared with previously published data from direct photoabsorption measurements in those limited energy regions where such data are available. Evaluation of the S(−2) sum using the presently reported absolute differential photoabsorption oscillator strength data gives a static dipole polarizability for dimethyl ether in excellent agreement (within 0.5%) with previously reported polarizability values. Other dipole sums S(u), (u=−1,−3,−4,−5,−6,−8,−10), and logarithmic dipole sums L(u), (u=−1 to −6), are also determined from the presently reported absolute differential photoabsorption oscillator strength data using dipole sum rules.     

A ruthenium(II) complex based turn-on electrochemiluminescence probe for the detection of nitric oxide

Electrochemiluminescence (ECL) detection technique using bipyridine-ruthenium(II) complexes as probes is a highly sensitive and widely used method for the detection of various biological and bioactive molecules. In this work, the spectral, electrochemical and ECL properties of a chemically modified bipyridine-ruthenium(II) complex, [Ru(bpy)(2)(dabpy)](2+) (bpy: 2,2'-bipyridine; dabpy: 4-(3,4-diaminophenoxy)-2,2'-bipyridine), were investigated and compared with those of its nitric oxide (NO)-reaction derivative [Ru(bpy)(2)(T-bpy)](2+) (T-bpy: 4-triazolephenoxy-2,2'-bipyridine) and [Ru(bpy)(3)](2+). It was found that the ECL intensity of [Ru(bpy)(2)(dabpy)](2+) could be selectively and sensitively enhanced by NO due to the formation of [Ru(bpy)(2)(T-bpy)](2+) in the presence of tri-n-propylamine. By using [Ru(bpy)(2)(dabpy)](2+) as a probe, a sensitive and selective ECL method with a wide linear range (0.55 to 220.0 μM) and a low detection limit (0.28 μM) was established for the detection of NO in aqueous solutions and living cells. The results demonstrated the utility and advantages of the new ECL probe for the detection of NO in complicated biological samples.     

A simple click generated probe for highly selective sequential recognition of Cu(II) and pyrophosphate

A click generated quinoline derivative (1) has been synthesized and used as a fluorescent probe for sequential recognition of Cu²⁺ and pyrophosphate (PPi) in DMSO/H₂O (1:1, v/v, HEPES 20 mM, pH = 7.4) solution. Probe 1 displays high selectivity to Cu²⁺ ions, and the in-situ prepared probe 1-Cu²⁺ exhibits high selectivity toward pyrophosphate (PPi) with emission recovery of probe 1. Therefore, 1-Cu²⁺ complex can be applied as a fluorescence turn-on probe for PPi with high selectivity and sensitivity.     

A Fluorescent coumarinylalkyne probe for the selective detection of mercury(II) ion in water

A coumarin-based alkyne was developed as a fluorescent chemodosimeter for the selective detection of mercuric ion. It showed a high selectivity and sensitivity to mercury(II) ion over other metal ions in water.     

Synthesis,characterization and crystal structure of a chiral polymeric Cu(II) complex bridged by tartrate

A chiral metal-organic coordination polymer, [Cu(Tar)(2,2′-bipy) · 5H₂O] (1) (Tar = L-tartrate dianion, 2,2′-bipy = 2,2′-bipyridine), has been synthesized by hydrothermal reaction of Cu(OAc)₂, Na₂T (H₂T = 2,3-O-isopropylidene-L-tartaric acid) and 2,2′-bipyridine, and characterized by IR, UV–vis spectra, elemental analyses, TG-DTA, and single crystal X-ray diffraction. In the hydrothermal reaction, the protection group isopropylidene for tartaric acid was hydrolyzed. The crystal structure of the coordination polymer 1 shows that each tartrate chelates two Cu(II) ions at opposite ends using one carboxylate oxygen and one hydroxyl oxygen and each Cu(II) ion is chelated by two halves of tartrate dianions, forming coordination polymer chains. Distorted octahedral geometry around copper is completed by a chelating 2,2′-bipyridine molecule. The 2,2′-bipyridine groups in two of parallel 1-D chains are interwoven, constituting ladder-shaped double chains. Strong offset π–π stacking interactions with a face-to-face distance of 3.33 Å for pyridine rings are observed. All the lattice water molecules hydrogen-bond to each other or to the carbonyl oxygen of tartrate, forming a 3-D supramolecular structure.     

Novel chiral dimesogenic bidentate ligands and their Cu(II) and Pd(II) metal complexes

The synthesis and characterization of cholesterol-based dimesogenic bidentate ligands and their Cu(II) and Pd(II) metallomesogens are reported in detail. To understand structure-property relationships in these materials the terminal alkoxy chains and the central metal atom have been varied. Our studies reveal that chiral dimesogenic bidentate ligands with n -butyloxy chains exhibit smectic A (SmA), twist grain boundary and chiral nematic (N * ) mesophases while substitution with either n -decyloxy or 3,7-dimethyloctyloxy chains also show a ferroelectrically switchable chiral smectic C (SmC * ) mesophase. The metal complexes with n -butyloxy chains show only the SmA phase whereas higher chain length derivatives exhibit N * phase irrespective of the metal atom present. The ligands are thermally stable whereas their metal complexes, especially Pd(II) systems, seem to be heat sensitive. Spontaneous polarization, response time and tilt angle measurements have been carried out in the smectic C * phase of the two ligands.     

Novel chiral dimesogenic bidentate ligands and their Cu(II) and Pd(II) metal complexes

The synthesis and characterization of cholesterol-based dimesogenic bidentate ligands and their Cu(II) and Pd(II) metallomesogens are reported in detail. To understand structure-property relationships in these materials the terminal alkoxy chains and the central metal atom have been varied. Our studies reveal that chiral dimesogenic bidentate ligands with n-butyloxy chains exhibit smectic A (SmA), twist grain boundary and chiral nematic (N*) mesophases while substitution with either n -decyloxy or 3,7-dimethyloctyloxy chains also show a ferroelectrically switchable chiral smectic C (SmC*) mesophase. The metal complexes with n-butyloxy chains show only the SmA phase whereas higher chain length derivatives exhibit N* phase irrespective of the metal atom present. The ligands are thermally stable whereas their metal complexes, especially Pd(II) systems, seem to be heat sensitive. Spontaneous polarization, response time and tilt angle measurements have been carried out in the smectic C* phase of the two ligands.     

Electronic structure of intercalation compounds of molybdenum disulfide MMoS2 (M = Cu, Ag) studied by X-ray emission and X-ray photoelectron spectroscopies

Electronic structures of intercalation compounds of molybdenum disulfide in which the MoS2 layers alternate with layers formed by the metal atoms (Cu, Ag) were studied by X-ray emission and photoelectron spectroscopies. The character of participation of these or other valence states of atoms in the construction of occupied and unoccupied energy bands of the substances studied was considered on the basis of the X-ray spectra of various series.     

A colorimetric probe for the selective naked-eye detection of Pb(II) ions in aqueous media

A new colorimetric molecular probe based on a 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dye selectively binds Pb(II) ions in aqueous solutions, allowing for highly sensitive naked-eye detection.     

A new 1D chiral metal-organic coordination polymer constructed by Cu(II) with L-3-Cyanophenylalanine

A new 1D chiral metal-organic coordination polymer [Cu(Cphe)₂] · 3H₂O (I) (HCphe = L-3-Cyanophenylalanine) has been synthesized in an aqueous solution and characterized by elemental analysis, thermogravimetric analysis (TGA), X-ray powder diffraction (XRPD), infrared spectroscopy (IR) and single crystal X-ray diffraction. The X-ray diffraction analysis reveals that I crystallizes in the monoclinic space group P2₁. The adjacent copper(II) atoms are linked by Cphe ligands to form a 1D zigzag chain, which is further connected via strong hydrogen bonds to form a 3D supramolecular framework. The unit cell parameters for I are: a = 12.0201(8), b = 6.1495(4), c = 14.8576(10) Å, β = 94.1720(10)°, V = 1095.00(13) ų, and Z = 2.