A Reversible and Highly Selective Fluorescent Sensor for Mercury(II) Using Poly(thiophene)s that Contain Thymine Moieties

Summary: A reversible and highly selective assay method has been developed to detect mercury(II ) (Hg²⁺) ions using a conjugated polymer (CP). The transduction mechanism is based on Hg²⁺‐mediated interpolymer π‐stacking aggregation, which results in the fluorescence self‐quenching of the CP. CPs that contain thymine moieties, poly[3‐(N‐thymin‐1‐ylacetyl)ethylamine‐thiophene] (PTT), have been synthesized and characterized. In the absence of Hg²⁺ ions, the PTT chains remain separated from each other and the CP exhibits strong fluorescence emission. Upon adding Hg²⁺ ions, the formation of interpolymer π‐stacking aggregation induced by specific thymine–Hg–thymine interactions results in the fluorescence quenching of PTT. Distinguishing aspects of this assay include the signal amplification of CPs and the specific binding of Hg²⁺ ions to thymine‐thymine (T–T) base pairs.

The binding of Hg²⁺ ions causes the separate conducting polymer chains to aggregate with subsequent fluorescence self‐quenching.     

Synthesis of a novel poly(para‐phenylene ethynylene) for highly selective and sensitive sensing mercury (II) ions

A new poly(p‐phenylene ethynylene) derivative with pendant 2,2′‐bipyridyl groups and glycol units (PPE‐bipy) has been prepared, and its metal ion sensing properties were investigated. The polymer of PPE‐bipy exhibited high selectivity for Hg²⁺ as compared with Li⁺, Na⁺, K⁺, Ba²⁺, Ca²⁺, Mg²⁺, Al³⁺, Mn²⁺, Ag⁺, Zn²⁺, Pb²⁺, Ni²⁺, Cd²⁺, Cu²⁺, Co,²⁺ and Fe³⁺ in THF/EtOH (1:1, v/v) solution. The fluorescence of PPE‐bipy was efficiently quenched by Hg²⁺ ions, and the detection limit was found to be 8.0 nM in a THF/EtOH (1:1, v/v) solvent system. PPE‐bipy also showed a selective chromogenic behavior toward Hg²⁺ ions by changing the color of the solution from slight yellow to colorless, which can be detected with the naked eye. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1998–2007, 2008     

Highly Selective Anionic Counterion‐based Fluorescent Sensor for Hg2+ by Grafted Conjugated Polyelectrolytes

Grafted conjugated polyelectrolytes were synthesized for the first time and characterized. The polymers demonstrated properties of a convenient and efficient protocol for creating Hg²⁺ sensors. The unique character of the new material comes from an anionic counterion nature with no external cofactors, and imparts high selectivity and fast detection for mercury ion in a fluorescence probe. The concept may be potentially applied to create new sensors for monitoring other ions.

     

Synthesis of a Fluorescent Polymer Bearing Covalently Linked Thienylene Moieties and Rhodamine for Efficient Sensing

A novel conjugated polymer (RB‐PPETE) of poly[p‐(phenylene ethynylene)‐alt‐(thienylene ethynylene)] (PPETE) bearing covalently linked thienylene rings and Rhodamine B units has been synthesized and successfully used to detect metal ions. The Rhodamine B exists as a lactone, which is colorless and non‐fluorescent. Hg²⁺ ions can induce the Rhodamine group to form a ring‐opened state. The fluorescence resonance energy transfer (FRET) was demonstrated in the polymer, and in the presence of Hg²⁺ ions the excitation energy along the backbone of the conjugated polymer is transferred to the energy acceptor (Rhodamine B), which leads to a visual color change of the solution from slight yellow to orange. Meanwhile, this new system shows outstanding Hg²⁺‐selective FRET off–on type fluoroionophoric properties among the representative metal ions in tetrahydrofuran.

     

基于T-T碱基错配的荧光传感器特异性检测汞离子

在本文中,我们研制了一种基于T-T碱基错配特异性键合汞离子的荧光传感器用于汞离子的检测。该传感器由两条分别标记了荧光基团（F）和淬灭基团（Q）的DNA探针组成,并且含有两对用于结合汞离子的T-T错配碱基。当汞离子存在时,两条探针之间形成T-Hg2+-T结构,作用力增强,从而拉近了荧光基团与淬灭基团之间的距离,发生能量转移,使荧光信号在一定程度上被淬灭。在优化的条件下,我们使用该传感器对汞离子进行检测,动力学响应范围为50nM到1000nM,线性相关方程为y= 5281.13 - 1650.56 lg[Hg2+] ( R2 = 0.985),检测下限为79nM。此外,我们还考察了该传感器的选择性,当用其它干扰离子（浓度都为1.0µM）代替待测离子进行实验时,没有发生明显的荧光淬灭,说明该传感器具有较高的选择性。该传感器的构建为汞离子的检测提供了一条快速、简便的新途径。     

Highly Water‐Soluble,Fluorescent, Conjugated Fluorene‐Based Glycopolymers with Poly(ethylene glycol)‐Tethered Spacers for Sensitive Detection of Escherichia coli

Know your bacteria! Two fluorene‐based, conjugated polymers with oligo(ethylene glycol)‐ and poly(ethylene glycol)‐tethered spacers have been prepared by the Suzuki coupling polymerization reactions. β‐Glucose and α‐mannose residues were covalently attached to the conjugated polymers by post‐polymerization functionalization with thiol‐functionalized carbohydrates under basic conditions. Investigations on their use as biosensing materials for the detection of Escherichia coli are reported (see figure).

     

Novel Water‐Soluble Poly(m‐benzamide)s: Precision Synthesis and Thermosensitivity in Aqueous Solution

Summary: Chain‐growth polycondensations of 3‐aminobenzoic acid methyl esters 1a and 1b , bearing a tri‐ or tetra(ethylene glycol) methyl ether unit on the amino group, respectively, were carried out with lithium hexamethyldisilazide (LiHMDS) as a base and phenyl 4‐methylbenzoate ( 2 ) as an initiator in THF at 0 °C. The poly(m‐benzamide)s obtained in the presence of N,N,N′,N′‐tetramethylethylenediamine (TMEDA) possessed narrow molecular weight distributions ( < 1.2) with molecular weights that were determined by the feed ratios of [ 1 ]₀/[ 2 ]₀. Poly 1a and poly 1b were each soluble in water and exhibited a lower critical solution temperature (LCST) in water. Furthermore, the phase separation in water depended on the length of the oligo(ethylene glycol) side chain and on the molecular weight and molecular weight distribution of poly 1 .

Thermally sensitive water‐soluble poly(m‐benzamide)s.     

Highly Sensitive Electrochemiluminescence Detection of Mercury(II) Ions Based on DNA‐Linked Luminol‐Au NPs Superstructure

A novel highly sensitive electrochemiluminescence (ECL) detection protocol for mercury(II) ions was developed. Based on the strong and stable thymine? thymine mismatches complexes coordination chemistry, mercury(II) ions can specifically bind to a designed DNA strand, leading to the release of the complimentary DNA strand. The released DNA strand was then captured by magnetic beads modified with specific DNA, and then through the formation of DNA‐linked luminol‐Au nanoparticles (NPs) superstructure, a specific ECL system for mercury(II) ions was developed. Using 3‐aminopropyl‐triethoxysilane as an effective enhancer, the ECL system can detect Hg²⁺ ion within a linear range from 2.0×10^?10 mol L^?1 to 2.0×10^?8 M, with a detection limit as low as 1.05×10^?10 M (3σ). Moreover, this ECL system is highly specific for Hg²⁺, without interference from other commonly coexisted metal ions, and it can be used for the analysis of real samples.     

Synthesis and Application of a Full Water‐Soluble and Red‐Emitting Chemosensor Based on Phenoxazinium for Copper(II) Ions

A phenoxazinium‐based chemosensor ( 1 ) bearing di(2‐picolyl)amine unit was successfully synthesized. The result shows that it is a red‐emitting and full water‐soluble chemosensor for the selective detection of Cu²⁺ in pure water. The fluorescence on‐off mechanism was studied by ab initio calculations. To confirm the suitability of 1 for biological applications, it was employed in the fluorescence detection of the intracellular Cu²⁺ with cultured KB cells. The results indicated that 1 had good membrane permeability and could be useful for the fluorescence microscopic imaging.     

All Solid State Nickel(II)‐Selective Potentiometric Sensor Based on an Upper Rim Substituted Calixarene

A new ionophore, i.e. p‐(2‐thiazolazo)calix[4]arene ( I ) has been explored for its selective behavior towards Ni(II) ions. A poly(vinyl chloride) based membrane containing ( I ) as an electroactive material along with sodiumtetraphenylborate (NaTPB), and nitrophenyloctyl ether in the ratio 10 : 100 : 3 : 150 (I:PVC:NaTPB:NPOE) (w/w) was used to fabricate an all solid state nickel(II)‐selective sensor. The developed sensor exhibited a working concentration range of 1.0×10^?6–1.0×10^?1 M, with a Nernstian slope of 28.9±1.0 mV/decade of activity and a response time of 10–15 s. This sensor shows a detection limit of 9.0×10^?7 M. Its potential response remains unaffected of pH in the range 3.0–7.6, and the cell assembly could be used successfully in partially nonaqueous medium (up to 10 % v/v) without any significant change in the slope value or the working concentration range. The sensor worked satisfactorily for about ten weeks and exhibited excellent selectivity over a number of mono‐, bi‐, and tri‐valent cations including alkali, alkaline earth metal, and transition metal ions. It could be used as an indicator electrode for the end point determination in the potentiometric titration of nickel ions against ethylenediaminetetraacetic acid (EDTA) as well as for the determination of nickel ion concentration in real samples.     

New Water‐Soluble Cationic Poly(p‐phenylenevinylene) Derivative: the Interaction with DNA and Selective Fluorescence Enhancement Induced by ssDNA

A new cationic cyano‐substituted poly(p‐phenylenevinylene) (N‐CNPPV) is synthesized by Knoevenagel condensation. The water‐soluble polymer shows different emission spectra in different solvents and displays unique fluorescent behaviors in the mixed solvents of water and THF. The new polymer can form a complex with ssDNA by adopting a more planar conformation, exhibiting red shift of emission wavelength and enhancement of fluorescence intensity. By investigating the fluorescent response of N‐CNPPV to various surfactants, we demonstrate that the hydrophobic interaction and electrostatic interaction result in the selective response of N‐CNPPV to ssDNA. This is the first report on selective fluorescence enhancement of conjugated polyelectrolyte induced by ssDNA.     

Synthesis of N,N,N-4,4＂-Di-（4-methylphenyl）-2,2＇：6＇,2＂- terpyridine-N,N,N-tris（isothiocyanato） Ruthenium（Ⅱ） and Application to Colorimetric Hg^2＋ Sensor

A terpyridine derivative DPTP [di-（4-methylphenyl）-2,2＇：6＇,2＂-terpyridine] was conveniently synthesized from 2-bromopyridine via halogen-dance reaction, Kharash coupling and Stille coupling reaction. Then its corresponding ruthenium complex Ru-DPTP [N,N,N-4,4＇＇-di-（4-methy,phenyl）-2,2＇：6＇,2＂-terpyridine-N,N,N-tris（is,-thi,cyanat,）- ruthenium（H） ammonium] was obtained and fully characterized by IR, UV-Vis, ESI MS and elemental analysis. The MLCT absorption band of Ru-DPTP was blue-shifted from 570 to 500 nm upon addition of Hg^2＋. Among a series of surveyed metal ions, the complex showed a unique recognition to Hg^2＋, indicating that it can be used as a selective colorimetric sensor for Hg^2＋.     

A Stimuli‐Responsive Nanogel‐Based Sensitive and Selective Fluorescent Sensor for Cr3+ with Thermo‐Induced Tunable Detection Sensitivity

Stimuli‐responsive poly(N‐isopropylacrylamide) nanogel with covalently labeled rhodamine B urea derivatives (P(NIPAM‐co‐RhBUA)) is utilized as a sensitive fluorescent probe for Cr³⁺ in aqueous solution, and its thermo‐induced tunable detection capacity is investigated. At 20 °C, non‐fluorescent nanogel can selectively bind with Cr³⁺ over some other metal ions, leading to prominent fluorescence OFF–ON switching due to the recognition of RhBUA with Cr³⁺. Upon heating above the phase transition temperature, enhanced fluorescence intensity is observed (≈61‐fold increase at 45 °C) for the nanogel in the presence of Cr³⁺, accompanied with an improved detection sensitivity, which suggest that hydrophobic microenvironment generated in the collapsed nanogel plays an active role for their detection performance.

     

Facile Iron‐Mediated AGET ATRP for Water‐Soluble Poly(ethylene glycol) Monomethyl Ether Methacrylate in Water

An environmentally friendly iron catalyst system was successfully developed in water for the AGET ATRP (activator generated by electron transfer for atom transfer radical polymerization) of water‐soluble monomer poly(ethylene glycol) monomethyl ether methacrylate (PEGMA) for the first time. A kinetic study indicated that the polymerization was a living/controlled process in which molecular weight increased linearly with monomer conversion. A lower molecular weight distribution ( / < 1.5) was maintained. The nontoxic and biocompatible characteristics of the iron catalyst facilitate its mediated polymerization to be used in the preparation of functional polymer materials for biomedical use.     

A Cationic Water‐Soluble Poly(p‐phenylenevinylene) Derivative: Highly Sensitive Biosensor for Iron‐Sulfur Protein Detection

Summary: A new water‐soluble cationic ammonium‐functionalized poly(p‐phenylenevinylene) (PPV‐NEtMe) was successfully synthesized and exhibited high sensitivity (K_sv = 6.9 × 10⁷ M ⁻¹) on rubredoxin, a type of anionic iron‐sulfur (Fe‐S) proteins. Further investigation showed that the biosensitivity of the cationic conjugated polymer is strongly dependent on the nature of the buffer solution and the concentration of the conjugated polymer used in the analyses.

The schematic diagram of anionic rubredoxin detected by PPV‐NEtMe.     

A Water‐Stable Uranyl Organic Framework as a Highly Selective and Sensitive Bifunctional Luminescent Probe for Fe3+ and Tetracycline Hydrochloride

A new coordination polymer (H₂bpy)_0.5?[(UO₂)_1.5(ipa)₂(H₂O)] ( 1 ) (H₂ipa=isophthalic acid, bpy=4,4′‐bipyridine) was synthesized by hydrothermal condition. It was characterized by IR spectroscopy, elemental analysis, TG‐DTA analysis, and powder X‐ray diffraction. Analysis of single‐crystal X‐ray diffraction results showed that the title compound exhibited a double chain bridged by the different uranyl ions and ipa^2? ligands. Through the hydrogen bond interactions and π???π stacking interactions, the double chains were assembled into the three‐dimensional supramolecular framework. Furthermore, the compound can be used as a promising bifunctional luminescence sensor for detecting and identifying Fe³⁺ and tetracycline hydrochloride antibiotic molecules with high selectivity and sensitivity in aqueous solutions. Moreover, the luminescent sensing mechanisms for different analytes were proposed. Moreover, the electronic properties of title compound were explored by density functional theory (DFT) calculations. The sensor system has been successfully applied for the detection of Fe³⁺ and tetracycline hydrochloride with high recovery percentages and low relative standard deviation in real river water samples.     

Ru(Ⅱ) Bipyridyl Complex and TiO2 Nanocomposite Based Biomolecule-free Photoelectrochemical Sensor for Highly Selective Determination of Ultra-trace Hg^2+ in Aqueous Systems

A biomolecule-free photoelectrochemical(PEC) probe(denoted as Ru-1) was designed, synthesized and coupled with TiO2 nanoparticles(NPs) for the highly sensitive and selective PEC detection of Hg^2+, a model analyte with hypertoxicity to both human health and ecosystem. The probe Ru-1 was designed with Ru(Ⅱ) bipyridyl complex as the chromophore, thiocyanate ligand as the recognition unit, and carboxylate group as the linkage site to connect Ru-1 to TiO2 nanoparticles. Under irradiation, Ru-1 shows strong affinity to TiO2 and good photophysical properties of strong visible light absorption, slow electron-hole(e-h^+) recombination, and fast photoelectron injection to TiO2 nanoparticles via the bridge of 4-(2,2-bipyridin)-4-yl-thiophene moiety. However, the specific coordination of Hg^2+ with Ru-1 via the thiol moiety in the thiocyanate enlarges the band gap of tlie complex and reduces the photocurrent significantly. The synergistic interaction between TiO2 nanoparticles and the Ru-1 complex led to a selective PEC sensing strategy for Hg^2+ detection. Detectable linear ranges from 10^-12 g/mL to 10^-7 g/mL and from 10^-7g/mL to 10^-3 g/mL were obtained without the interference from possibly co-existed metal ions. The good analytical performances indicate the chemical probe based biomolecule-free PEC platform may offer a new route for the detection of biologically and environmentally important small molecules.     

Highly Selective Ratiometric Fluorescent Sensor for La(III) Ion Based on a New Schiff's Base

Abstract

A new fluorescent sensor containing (1-[({2-[2-(2-hydroxy-1-naphtyl)-3-(2-{[(E)-1-(2-hydroxy-1-naphtyl)methylidene]amino}ethyl)-1-imidazolidinyl]ethyl}imino)methyl]-2-naphthol) (L) was synthesized for detecting La(III) ratiometrically. Complexation between compound L and La(III) with high selectivity gives rise to a great red shift from 430 to 522 nm in the emission spectra. In acetonitrile, the red shift of fluorescent emission upon lanthanium binding is due to the formation of a 1:1 metal–ligand complex. The fluorescent probe exhibits high selectivity over other common metal ions and mono-, di-, and trivalent cations, which indicates good selectivity for La(III) ions over a large number of interfering cations.     

A New Luminescent Ruthenium(II) Polypyridine‐derived Dipicolylamine Complex as a Sensor for Cu2+ Ions

A chemo‐sensor [Ru(bpy)₂(bpy‐DPF)](PF₆)₂ ( 1 ) (bpy=2,2′‐bipyridine, bpy‐DPF=2,2′‐bipyridyl‐4,4′‐bis(N,N‐di(2‐picolyl))formylamide) for Cu²⁺ using di(2‐picolyl)amine (DPA) as the recognition group and a ruthenium(II) complex as the reporting group was synthesized and characterized successfully. It demonstrates a high selectivity and efficient signaling behavior only for Cu²⁺ with obvious red‐shifted MLCT (metal‐to‐ligand charge transfer transitions) absorptions and dramatic fluorescence quenching compared with Zn²⁺ and other metal ions.