Reversible "off-on" fluorescent chemosensor for Hg2+ based on rhodamine derivative

A novel and simple fluorescent chemosensor based on rhodamine was designed and synthesized to detect Hg(2+) with high selectivity. The structure of chemosensor 1 was characterized by IR, (1)H NMR, and HRMS spectroscopies. Chemosensor 1 exhibited distinct fluorescent and colorimetric changes toward Hg(2+) in an ethanol/water (80/20, v/v) solution, which resulted in the formation of 1/Hg(2+) complex with the Hg(2+)-induced ring opening of the spirolactam ring in rhodamine. The reversibility of chemosensor 1 was verified through its spectral response toward Hg(2+) ions and TBAI (tetrabutylammonium iodide) titration experiments.     

A chromenoquinoline-based fluorescent off-on thiol probe for bioimaging

A new chromenoquinoline-based fluorescent off-on thiol probe 2 is reported. In aqueous buffer solutions at physiological pH, the probe exhibited 223-fold enhancement in fluorescence intensity by a Michael addition of cysteine to the maleimide appended to a chromenoquinoline. Cell permeability and live cell imaging of thiols are also demonstrated.     

Salicylimine-based fluorescent chemosensor for aluminum ions and application to bioimaging

In this study, an assay to quantify the presence of aluminum ions using a salicylimine-based receptor was developed utilizing turn-on fluorescence enhancement. Upon treatment with aluminum ions, the fluorescence of the sensor was enhanced at 510 nm due to formation of a 1:1 complex between the chemosensor and the aluminum ions at room temperature. As the concentration of Al(3+) was increased, the fluorescence gradually increased. Other metal ions, such as Na(+), Ag(+), K(+), Ca(2+), Mg(2+), Hg(2+), Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Pb(2+), Cr(3+), Fe(3+), and In(3+), had no such significant effect on the fluorescence. In addition, we show that the probe could be used to map intracellular Al(3+) distribution in live cells by confocal microscopy.     

Highly sensitive and selective colorimetric and off-on fluorescent probe for Cu(2+) based on rhodamine derivative

A new probe for Cu(2+) based on the Cu(2+)- induced reversible ring-opening mechanism of the rhodamine spirolactam was described. It displayed a highly selective and sensitive "turn-on" fluorescent and colorimetric response toward Cu(2+).     

一种大斯托克斯位移的红光发射荧光探针选择性检测次氯酸

设计、合成了一种基于巴比妥酸衍生物的具有 D-π-A结构的光学探针 3。该探针能够作为一种高度灵敏和选择性的次氯酸指示剂, 快速实现对次氯酸的比色和荧光信号(开-关)的双响应(约 15 s)。推测的响应机制是 ClO^-与 C=C之间发生了亲电加成和氧化裂解反应, 导致探针的 D-π-A 结构遭到破坏, 从而阻断了其分子内电荷转移(intramolecular charge transfer, ICT)进程。探针只需一步即可合成, 同时具有红光发射(628 nm)和较大的斯托克斯位移(158 nm), 检测限(limit of detection, LOD)低至14 nmol·L^-1。此外, 探针还表现出低细胞毒性, 并成功应用于活细胞成像。     

一种大斯托克斯位移的红光发射荧光探针选择性检测次氯酸

设计、合成了一种基于巴比妥酸衍生物的具有D-π-A结构的光学探针3。该探针能够作为一种高度灵敏和选择性的次氯酸指示剂,快速实现对次氯酸的比色和荧光信号(开-关)的双响应(约15 s)。推测的响应机制是ClO^-与C=C之间发生了亲电加成和氧化裂解反应,导致探针的D-π-A结构遭到破坏,从而阻断了其分子内电荷转移(intramolecular charge transfer,ICT)进程。探针只需一步即可合成,同时具有红光发射(628 nm)和较大的斯托克斯位移(158 nm),检测限(limit of detection,LOD)低至14 nmol·L^-1。此外,探针还表现出低细胞毒性,并成功应用于活细胞成像。     

Effectively selective fluorescent chemosensor for terephthalate

A novel fluorescent calix[8]arene-like chemosensor 1 was designed and synthesized for effectively selective recognition of terephthalate. The receptor enclosed and acted on the special guest by synergistic effects of cavity size, π-π stacking and hydrogen bonding interaction.     

Core-shell nanostructured molecular imprinting fluorescent chemosensor for selective detection of atrazine herbicide

To convert the binding events on molecularly imprinted polymers (MIPs) into physically detectable signals and to extract the templates completely are the great challenges in developing MIP-based sensors. In this paper, a core-shell nanostructure was employed in constructing the MIP chemosensor for the improvements of template extraction efficiency and imprinted sites accessibility. Vinyl-substituted zinc(II) protoporphyrin (ZnPP) was used as both fluorescent reporter and functional monomer to synthesize atrazine-imprinted polymer shell at silica nanoparticle cores. The template atrazine coordinates with the Lewis acid binding site Zn of ZnPP to form a complex for the molecular imprinting polymerization. These imprinted sites are located in polymer matrix of the thin shells (~8 nm), possessing better accessibility and lower mass-transfer resistance for the target molecules. The fluorescence properties of ZnPP around the imprinted sites will vary upon rebinding of atrazine to these imprinted sites, realizing the conversion of rebinding events into detectable signals by monitoring fluorescence spectra. This MIP probe showed a limit of detection (LOD) of about 1.8 μM for atrazine detection. The core-shell nanostructured MIP method not only improves the sensitivity, but also shows high selectivity for atrazine detection when compared with the non-molecular imprinted counterparts.     

A fluorescent and colorimetric chemosensor for selective detection of aluminum in aqueous solution

We have synthesized a new Schiff base 1, which detects Al³⁺ through fluorescence and naked eye in aqueous solution. The sensor 1 exhibited selective and sensitive recognition toward Al³⁺ via significant fluorescence enhancement (31-fold). Moreover, it showed a significant color change from colorless to yellow. The complex formation was proposed to be 1:1 ratio, based on the Job plot, ESI-mass spectrometry analysis, ¹H NMR titration, and IR analysis. The detection limit was 1.00 μM, which is below the WHO acceptable limit (1.85 μM) in drinking water. In addition, the sensor 1 could be recyclable simply through treatment with a proper reagent such as EDTA.     

A colorimetric and fluorescent turn-on chemosensor for Al and its application in bioimaging

The sensing properties of a boron dipyrromethene derivative 1 containing a N,N-(dimethylamino)styryl group at its α-position and an aniline moiety at meso-position were investigated by steady-state UV-vis absorption and fluorescence spectroscopy, which were found to exhibit wavelength ratiometric and large fluorescence enhancement in the presence of Al³⁺ with specific selectivity over other metal ions in aqueous media. Furthermore, confocal fluorescence microscopy experiments demonstrated that 1 could be used as a fluorescent probe for Al³⁺ in living cells.     

A highly selective fluorescent chemosensor for Fe (III) based on rhodamine 6G dyes derivative

A new fluorescent probe L based on the rhodamine 6G platforms for Fe³⁺ has been designed and synthesised. L showed excellent selectivity and high sensitivity for Fe³⁺ against other metal ions such as K⁺, Na⁺, Ag⁺, Cu²⁺, Co²⁺, Mg²⁺, Cd²⁺, Ni²⁺, Zn²⁺, Fe²⁺, Hg²⁺, Ce³⁺ and Y³⁺ in HEPES buffer (10 mM, pH 7.4)/CH₃CN (40:60, V/V). The distinct color change and the rapid emergence of fluorescence emission provided naked-eyes detection for Fe³⁺. The recognition mechanism of the probe toward Fe³⁺ was evaluated by Job’s plots, IR and ESI-MS. In order to further study their fluorescent properties, L + Fe³⁺ fluorescence lifetime was also measured. Moreover, the test strip results showed that these probes could act as a convenient and efficient Fe³⁺ test kit.     

A highly selective fluorescent probe for thiol bioimaging

A new fluorescent turn-on probe (3) for the selective sensing and bioimaging of thiols is reported. In aqueous buffer solutions at physiological pH, thiols cleave the 2,4-dinitrobenzenesulfonyl group to release the red-emissive donor-acceptor fluorophore (4). The probe displays excellent immunity to interference from nitrogen and oxygen nucleophiles and the imaging of thiols in living cells is demonstrated.     

Aminoxy-linked rhodamine hydroxamate as fluorescent chemosensor for Fe in aqueous media

A novel feric ion-selective rhodamine-based fluorescent chemosensor, which contains a bis-aminoxy chain moiety, has been developed. The multi-dentate binding site of rhodamine fluorophore shows selective detection of ferric iron over other biologically important metal ions in aqueous media and also shows 1:1 binding stoichiometry.     

A highly specific BODIPY-based fluorescent probe for the detection of hypochlorous acid

A fluorescent probe, HKOCl-1, has been successfully developed for the detection of hypochlorous acid on the basis of a specific reaction with p-methoxyphenol. The formation of HOCl has been successfully detected not only in an abiotic system but also in an enzymatic system (myeloperoxidase/H2O2/Cl(-) system) and in living macrophage cells upon stimulation. This new probe might be used as an efficient tool for probing the roles HOCl plays in biological systems.     

A highly selective fluorescent chemosensor for lead ions

A simple fluorescent chemosensor 1 exhibits a 40-fold fluorescence enhancement upon addition of lead ion and yet is insensitive to most of univalent and divalent metal ions. The high affinity of 1 toward Pb2+ presumably results from the cooperative binding behaviors of two potential metal binding sites: the dicarbonyl and the 15-monoazacrown-5 ether.     

A new selective phenanthroline-based fluorescent chemosensor for Co

An intramolecular charge transfer (ICT) chromophore 2-(2-pyridine)imidazo [4,5,f]-1,10-phenanthroline (1) has been synthesized and firstly used as a chemosensor with a reversible, ‘on-off’ sensing capability for biologically and environmentally significant Co²⁺ in DMF under buffered conditions. The experiment results also show that the response behavior of 1 to Co²⁺ is pH independent in range of pH 3.0-7.0 and show excellent selectivity for Co²⁺ over other cations.     

A fluorescent probe for copper and hypochlorite based on rhodamine hydrazide framework

A rhodamine derivative (1) was synthesized as a fluorescence turn-on probe for copper (Cu²⁺) and hypochlorite (ClO^?). The probe gave a fluorescence turn-on change at 587 nm with a color change from colorless to pink in the presence of Cu²⁺ or ClO^? ions in aqueous solution. It was found that the Cu²⁺ ion bound to 1 in a 1:1 stoichiometry and induced a spirolactam ring opening of the rhodamine moiety leading to a fluorescence turn-on, confirmed by Job’s plot, ESI-Mass, and ¹H NMR analyses. In the presence of ClO^? ion, probe 1 underwent a hypochlorite-mediated oxidation and hydrolysis to produce a ring-opened rhodamine B with a fluorescence enhancement. However, these changes were not monitored in case of other metal ions, anions, and reactive redox species. In addition, probe 1 can readily react with the ClO^? to provide a distinct fluorescence enhancement along with a pink color even in the presence of various competitive species.     

A novel colorimetric and fluorescent chemosensor: synthesis and selective detection for Cu and Hg

A novel two-channel metal ion sensor has been synthesized from macrocyclic dioxotetraamine and 1,8-naphthalimide derivative. The metal ion-selective signaling behaviors of the sensor were investigated. The sensor presented the selective coloration for Cu²⁺ and Hg²⁺ that can be detected by the naked-eye, respectively. Besides, the addition of Cu²⁺ and Hg²⁺ quenched the fluorescence of 1 obviously and the detection limit was found to be 3 × 10⁻⁷ M for Cu²⁺ and 7 × 10⁻⁷ M for Hg²⁺. This sensor can be utilized for the visual and spectroscopic detection of Cu²⁺ or Hg²⁺ in the presence of the other competing metal ions.     

A fluorescent chemosensor for wide-range pH detection

Simple polyamines, L1-L3, bearing anthracene and benzophenone units at the respective ends, behave as a fluorescent pH sensor applicable to wide-range pH detection.     

Calix[4]arene based selective fluorescent chemosensor for organic acid recognition

A novel calix[4]arene-based fluorescent chemosensor bearing a 2-aminopyridine moiety and a naphthalenic fluorophore was synthesized The chemical structure of the product was elucidated by FT-IR, MS-FAB, NMR and elemental analyses. Then, the properties and identification mechanism of the synthesized chemosensor were investigated. The results show that the chemosensor exhibits selective fluorescent quenching in the presence of aromatic organic acid in acetonitrile solution, and that the binding ability of the chemosensor with organic acid is in the order of p-cyanic-benzyl acid > p-chloric-benzyl acid > p-methoxyl-benzyl acid > benzyl acid. __________ Translated from Journal of South China University of Technology (Natural Science Edition), 2007, 35(4): 20–24 [译自: 华南理工大学学报(自然科学版)]