Core‐shell type dually fluorescent polymer nanoparticles for ratiometric pH‐sensing

The synthesis and pH‐sensing properties of fluorescent polymer nanoparticles (NPs) in the 20 nm diameter range with a sensitive dye covalently attached to the particle surface and a reference dye entrapped within the particle core are presented. Fluorescein‐functionalized NPs were readily obtained by conjugation of fluorescein isothiocyanate (FITC) to amine‐coated crosslinked polystyrene‐based nanoparticles prepared by microemulsion polymerization followed by postfunctionalization. This all water‐based method gave access to stable aqueous suspensions of pH‐sensing fluorescent NPs. The encapsulation of the insensitive reference fluorescent dye (1,9‐diphenylanthracene, DPA) was then conveniently achieved by soaking leading to dual fluorescent NPs containing about 20 DPA and 55 fluorescein, as deduced from spectroscopic analyses. This core‐shell type architecture maximizes the interactions of the sensing dye with the medium while protecting the reference dye. The variations of the ratio of the fluorescence emission intensities of the sensitive dye (fluorescein) to the reference dye (DPA) with pH show that the dual fluorescent NPs act as a ratiometric pH sensor with a measuring range between pH 4 and pH 8. This pH nanosensor was found to be fast, fully reversible, and robust without any leaching of dye over a long period of time. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6206–6213, 2008     

Naphthalimide-rhodamine based fluorescent probe for ratiometric sensing of cellular pH

The pH values of lysosomes in cancer cells is slightly lower than that in normal cells, which can be used to distinguish cancer cells from normal cells. According to this, a naphthalimide-rhodamine based fluorescent probe(hereafter referred to as RBN) with a pK_a of 4.20 was designed and synthesized for ratiometric sensing of cellular pH via fluorescence resonance energy transfer(FRET), which can respond to different pH precisely through ratiometric fluorescence intensity(Ⅰ_(577)/Ⅰ_(540)). RBN can be employed to distinguish cancer cells from normal cells on the basis of different fluorescent response, in particular, RBN showed excellent water solubility and low cell toxicity, all these are quite significant for potential application in cancer diagnose and therapy.     

Tunable fluorescent/phosphorescent platinum(II) porphyrin-fluorene copolymers for ratiometric dual emissive oxygen sensing

A series of new platinum(II) 5,15-bis(pentafluorophenyl)-10,20-bis(phenyl)porphyrin-9,9-dioctylfluorene copolymers, in which the relative intensities of the blue fluorescence and red phosphorescence can be easily tuned by the initial feed ratio of the two monomers or energy transfer between the fluorescent and phosphorescent units, have been designed and prepared for the application in ratiometric dual emissive oxygen sensing. To the best of our knowledge, this is the first example of a ratiometric oxygen sensor based on dual fluorescent/phosphorescent polymers or copolymers containing transition-metal complexes. It also provides an alternative and easy way to achieve dual emissive oxygen sensing.     

Core-shell fluorescent silica nanoparticles for sensing near-neutral pH values

pH-responsive fluorescent core-shell silica nanoparticles (SiNPs) were prepared by encapsulating the pH-sensitive fluorophore 8-hydroxypyrene-1,3, 6-trisulfonate into their silica shell via a facile reverse microemulsion method. The resulting SiNPs were characterized by SEM, TEM, fluorescence lifetime spectroscopy, photobleaching experiments, and photoluminescence. The core-shell structure endows the SiNPs with reduced photobleaching, excellent photostability, minimized solvatachromic shift, and increased fluorescence efficiency compared to the free fluorophore in aqueous solution. The dynamic range for sensing pH ranges from 5.5 to 9.0. The nanosensors show excellent stability, are highly reproducible, and enable rapid detection of pH. The results obtained with the SiNPs are in good agreement with data obtained with a glass electrode.

Thiazole sulfonamide based ratiometric fluorescent chemosensor with a large spectral shift for zinc sensing

A new thiazole sulfonamide (TTP, 1) based Zn²⁺ selective intrinsic chemosensor has been synthesized and investigated. The chemosensor shows a selective fluorescence enhancement (3.0 fold) with Zn²⁺ over biologically relevant cations (Ca²⁺, Mg²⁺, Na⁺, and K⁺) and biologically non-relevant cations (Cd²⁺) in an aqueous ethanol system. It produces an increase in the quantum yield and a longer emission wavelength shift (64 nm) on Zn²⁺ binding with the potential of a ratiometric assay.     

双量子点纳米复合物NO比率荧光探针的合成与应用

通过静电吸附作用,合成了CdSe@SiO_2-CdTe双量子点的纳米复合物.一氧化氮(NO)与CdTe量子点表面Cd离子结合形成Cd-NO复合物,引起CdTe量子点荧光猝灭,而不影响CdSe量子点的荧光.当NO浓度在0.1~2.2μmol/L之间变化时,该探针荧光强度比值I_(603)/I_(532)符合线性关系(R=-0.995 4),从而实现对NO的定量检测.     

Dual colored mesoporous silica nanoparticles with pH activable rhodamine-lactam for ratiometric sensing of lysosomal acidity

Alteration of lysosome acidity has been implicated in many biological events ranging from apoptosis to cancer metastasis, etc. Mesoporous silica nanoparticles doped with acid activable rhodamine-lactam and fluorescein isothiocyanate (FITC) were developed for ratiometric sensing of lysosomal pH changes in live cells with flow cytometry.     

Turn-on ratiometric fluorescent sensor for Pb detection

We report a ratiometric lead fluorescent sensor (LFS-1) with high affinity to Pb²⁺ that shows considerable selectivity over 12 other physiological related metal cations in aqueous media. Binding induces excimer formation, providing a highly sensitive ratiometric measure of lead concentrations.     

A ratiometric fluorescent probe with high sensitivity and selectivity for phosgene sensing in solution and gas

Phosgene has attracted wide attention because of its important applications and value in modern industry, agriculture, and other fields, though it easily leaks and is difficult to detect. In this work, we designed and synthesized a naphthalimide-based fluorescent probe, which is easy to prepare, stable, and able to discriminate between phosgene, acetyl chloride, oxalyl chloride, thionyl chloride, phosphorus oxychloride, and tosyl chloride. Our results indicate that the probe can react with phosgene selectively and sensitively, showing remarkable ratiometric fluorescence changes. Furthermore, the probe can be made into test strips, which can determine phosgene in air effectively. The present work provides a novel class of naphthalimide-based derivatives with potential application in phosgene sensing in real time simply and safely with further optimization.     

A colorimetric,ratiometric and water-soluble fluorescent probe for simultaneously sensing glutathione and cysteine/homocysteine

A chlorinated coumarin-aldehyde was developed as a colorimetric and ratiometric fluorescent probe for distinguishing glutathione (GSH), cystenine (Cys) and homocysteine (Hcy). The GSH-induced substitution-cyclization and Cys/Hcy-induced substitution-rearrangement cascades lead to the corresponding thiol-coumarin-iminium cation and amino-coumarin-aldehyde with distinct photophysical properties. The probe can be used to simultaneously detect GSH and Cys/Hcy by visual determination based on distinct different colors – red and pale-yellow in PBS buffer solution by two reaction sites. From the linear relationship of fluorescence intensity and biothiols concentrations, it was determined that the limits of detection for GSH, Hcy and Cys are 0.08, 0.09 and 0.18 μM, respectively. Furthermore, the probe was successfully used in living cell imaging with low cell toxicity.     

A versatile water soluble fluorescent probe for ratiometric sensing of Hg2+ and bovine serum albumin

A novel tetraazamacrocycle fluorescent sensor (6-(1-(dimethylamino)-5-naphthalene sulfonyl)-3,6,9,15-tetraazabicyclo[9.3.1] pentadeca-1(15),11,13-triene, 1) has been designed and prepared, which can be utilized for selective and ratiometric sensing of Hg(2+) and bovine serum albumin (BSA) with two different responsive modes in aqueous solution at physiological pH (50 mM Tris-HCl, pH 7.6). Above 0.5 ppb Hg(2+) can be discerned by coordination with 1 and the emission color changes enable 1 to be applied to a fast Hg(2+) test paper assay. Sensor 1 has also been demonstrated to be easily cell-penetrable and applicable for Hg(2+) imaging in living cells. Imaging of BSA in the gel using SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis) stained in the medium containing 1 verified that the binding of 1 and BSA was successful in the presence of nonprotein substances. The linear range of 1 towards BSA utilizing ratiometric fluorescent calibration via noncovalent interaction in solution is 0-100 μg mL(-1) with a detection limit of 1 μg mL(-1), and has been successfully employed to determine the albumin concentration in blood serum by means of ratiometric fluorescent measurements for the first time. Finally, sensor 1 behaves as a fluorescent molecular switch composed of triple logic gates upon chemical inputs of Hg(2+) and BSA, which potentially provides intelligent diagnostics for Hg(2+) contaminated serum on the nanoscale.     

A ratiometric fluorescent viscosity sensor

The development of a dual probe that provides ratiometric measurements of fluid viscosity is described. The design is based on coupling of a primary fluorophore with viscosity-independent fluorescence emission (blue unit) with a secondary fluorophore that exhibits viscosity-sensitive fluorescent emission quantum yield (red unit). Excitation of the secondary fluorophore can be achieved via Resonance Energy Transfer. The ratio of the fluorescence emission of these fluorophores provides an accurate, ratiometric measurement of solvent viscosity.     

A selective fluorescent ratiometric chemodosimeter for mercury ion

A selective fluorescent chemodosimeter for mercury ion based on the mercury-promoted intramolecular cyclic guanylation of thiourea connected on 1, 8-naphthalimide is described.     

A colorimetric and ratiometric fluorescent probe for palladium

A colorimetric and ratiometric fluorescent probe for the palladium species has been developed based on the Pd(0)-catalyzed cleavage of an allyoxycarbonyl group of amines under mild conditions. The probe displays a highly sensitive and selective response with significant changes in both color (from colorless to jade-green) and fluorescence (from blue to green), through the ICT process.     

Rare-earth ions coordination enhanced ratiometric fluorescent sensing platform for quantitative visual analysis of antibiotic residues in real samples

Levofloxacin (LVFX) as a representative drug of quinolone antibiotics is widely used in clinical, and its residues enriched in water bodies and sideline products seriously damage human health. It is imperative to develop a real-time/on-site sensing method for monitoring residual antibiotics. Here, we report a portable sensing platform by utilizing a composite fluorescent nanoprobe constructed by the cerium ions (Ce³⁺) coordination functionalized CdTe quantum dots (QDs) for the visual and quantitative detection of LVFX residues. This fluorescent probe provides a distinct color variation from red to green, which shows a good linear relationship to LVFX residues concentrations in the range of 0-6.0 µmol/L with a sensitive limit of detection (LOD) of 16.3 nmol/L. The smartphone platform with Color Analyzer App installed, which could accomplish quantified detection of LVFX in water, milk, and raw pork with a LOD of 27.9 nmol/L. The facile sensing method we proposed realizes rapid visualization of antibiotics residual in the environment and provides a practical application pathway in food safety and human health.     

Synthesis and characterization of new fluorescent nanoparticles

A novel kind of fluorescent nanoparticles（FNPs）has been prepared using a precipitation polymerization method.Methacrylic acid,trimethylolpropane trimethacrylate and azobisisobutyronitrile were used as functional-monomer,cross-linker and initiator, respectively.Compared with other fluorescent nanoparticles,the FNPs have the characteristics including low dye leakage and good photostability.The fluorescence microscopy imaging indicates that the FNPs can be used as fluorescent labels in bioanalysis.     

Benzimidazole-based ratiometric fluorescent receptor for selective recognition of acetate

A novel fluorescent receptor bearing benzimidazole moieties as recognition sites was synthesized. The recognition behaviour of the receptor towards various anions has been evaluated in CH₃CN. The receptor showed ratiometric fluorescent changes only with CH₃COO⁻, and it showed no significant response to any of other anions such as Cl⁻, Br⁻, I⁻, , , C₆H₅COO⁻ and .     

A ratiometric fluorescent core-shell nanoprobe for sensing and imaging of zinc(II) in living cell and zebrafish

A zinc(II)-responsive ratiometric fluorescent core-shell nanoprobe (referred to as QPNPs) is described. It consist of an optimized combination of an internal reference dye (TBAP) encapsulated in the core, and a Zn(II)-specific indicator dye (PEIQ) in the shell. The nanoprobe was synthesized via single-step graft copolymerization induced by tert-butyl hydroperoxide at 80 °C. QPNPs exhibit a well-defined core-shell nanostructure and well-resolved dual emissions after photoexcitation at 380 nm. After exposure to Zn(II), the QPNPs display a green fluorescence peaking at ~500 nm that increases with the concentration of Zn(II), while the pink fluorescence of the porphine-derived reference dye peaking at ~650 nm remains unchanged. This results in color change from pink to green and thus enables Zn(II) to be detected both spectroscopically and with bare eyes. Zn(II) can be quantified with a 3.1 nM detection limit. The core-shell structured nanoprobe was also applied to real-time imaging of Zn(II) in living HeLa cells and in zebrafish. This work establishes a reliable approach to synthesize ratiometric fluorescent nanoprobes. It enables such nanoprobes to be prepared also by those not skilled in nanomaterial synthesis.

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Graphical abstract A zinc(II)-responsive core-shell nanoprobe (referred to as QPNP) is synthesized via single-step graft copolymerization. Zn(II) can be quantitated with a 3.1 nM detection limit by the QPNPs through ratiometric fluorescence strategy (PEIQ as the Zn(II) indicator and TBAP as the reference dye).

     

A Zn2+-specific turn-on fluorescent probe for ratiometric sensing of pyrophosphate in both water and blood serum

A novel fluorescent sensor composed of a naphthalene functionalized tetraazamacrocycle ligand 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3-methyl naphthalene (1) and Zn(2+) has been designed and prepared, which can be utilized for selective and ratiometric sensing of pyrophosphate (PPi) over other phosphate-containing anions in aqueous solution at physiological pH. Notably, the water soluble 1 itself also exhibits a selective enhanced fluorescent response to Zn(2+), and the complex 1-Zn(2+) thus formed eventually fulfils the synergic Zn(2+) coordination-altered strategy with PPi. Furthermore, the ratiometric sensing of 1-Zn(2+) towards PPi performed well even in blood serum milieu. Finally, the sensor 1-Zn(2+) was successfully employed to monitor a real-time assay of inorganic pyrophosphatase (PPase) by means of ratiometric fluorescent measurements for the first time.