A highly selective fluorescent probe for pyrophosphate in aqueous solution

A new 4-amino-1,8-naphthalimide-based fluorescent chemosensor bearing a guanidiniocarbonyl pyrrole moiety has been synthesized. The sensor displays a selective fluorescent enhancement with pyrophosphate over ATP, ADP, AMP and other inorganic anions in aqueous solution.     

Investigation on sensing mechanism of a fluorescent probe for TNP detection in aqueous solution

In this paper, the synthesis and spectral properties of a fluorescent probe Nph-An for TNP detection has been introduced and its sensing mechanism has been studied with density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. For TNP detection in aqueous solution the probe shows high sensitivity, selectivity and efficiency. The theoretical results demonstrate that the excited-state intermolecular hydrogen bonding (HB) plays an important role for the TNP detection. In the excited state, the intermolecular HB between Nph-An and TNP is strengthened, and thus strongly facilitates the nonirradiative PET process to induce the fluorescence quenching. Whereas, the probe Nph-An emits strong fluorescence because of the intramolecular charge transfer (ICT) properties, which is confirmed by the solvatochromism effect. The calculated absorption spectra of Nph-An and Nph-An + TNP agree well with the experimental values and theoretical analysis provides a detailed and clear explanation of the sensing mechanism.     

Highly selective and sensitive near-infrared fluorescent sensors for cadmium in aqueous solution

On the basis of tricabocyanine, two near-infrared fluorescent sensors CYP-1 and CYP-2 have been designed and synthesized. Both of them can selectively and sensitively recognize Cd(2+) from other metal ions, especially the CYP-2, which can distinguish Cd(2+) in neutral buffer solution.     

An effective colorimetric and ratiometric fluorescent probe for bisulfite in aqueous solution

We have developed the first two-photon colorimetric and ratiometric fluorescent probe, BICO, for the detection of bisulfite (HSO₃⁻) in aqueous solution. The probe contains coumarin and benzimidazole moieties and can detect HSO₃⁻ based on the Michael addition reaction with a limit of detection 5.3 × 10⁻⁸ M in phosphate-buffered saline solution. The probe was used to detect bisulfite in tap water, sugar and dry white wine. Moreover, test strips were made and used easily. We successfully applied the probe to image living cells, using one-photon fluorescence imaging. BICO overcomes the limitations in sensitivity of previously reported probes and the solvation effect of bisulfite, which demonstrates its excellent value in practical application.     

A rhodamine-based Hg2+-selective fluorescent probe in aqueous solution

A new rhodamine-based Hg²⁺-selective fluorescent probe (I) was designed and synthesized. Compound I displays excellent selective and sensitive response to Hg²⁺ over other transition metal ions in neutral aqueous solutions. I itself is a colorless, nonfluorescent compound. Upon addition of Hg²⁺ to its solution, the thiosemicarbazide moiety of I undergoes an irreversible desulfurization reaction to form the corresponding 1,3,4-oxadiazole (II), a colorful and fluorescent product, causing instantaneous development of visible color and strong fluorescence emission. Based on this mechanism, a fluorogenic probe for Hg²⁺ was developed. The fluorescence increases linearly with the Hg²⁺ concentration up to 0.8 μmol L⁻¹ with the detection limit of 9.4 nmol L⁻ (3σ).     

A TCF-based colorimetric and fluorescent probe for palladium detection in an aqueous solution

A new fluorescent probe (TCF-AC) that contains 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) skeleton has been developed. Probe TCF-AC exhibits highly selective and sensitive detection toward Pd⁰ in EtOH/H₂O (1:1, v/v, PBS 20?mM, pH?=?7.4) solution with fluorescence “turn on” and colorimetric changes. The Pd⁰ detection by TCF-AC holds some advantages including good anti-interference ability, a relative large Stokes shift (>100?nm), and a low detection limit (7.05?×?10^?7?M). Cell imaging studies demonstrate that TCF-AC is applicable to detect Pd⁰ in living HeLa cells.     

Colorimetric and orange light-emitting fluorescent probe for pyrophosphate in water

A dual-mode probe based on a benzothiazolium hemicyanine chromophore was designed and synthesized for the detection of pyrophosphate (PPi) in water. The use of a fluorescent probe for colorimetric and long-wavelength fluorescence detection of PPi could be suitable for both rapid in-field and bioimaging experiments.     

Design of quinoline-based fluorescent probe for the ratiometric detection of cadmium in aqueous media

A new fluorescent probe,DQCd2,based on 4-piperidinoquinoline has been synthesized as a fluorescent probe for Cd²⁺.It can ratiometrically respond to Cd²⁺ in PBS buffer by a remarkable emission intensity enhancement（88-fold） and wavelength shift（70 nm）.     

A novel fluorescent distinguished probe for Cr (VI) in aqueous solution

Salicylaldehyde rhodamine B hydrazone (SRBH) was developed as a new spectrofluorimetric probe for the selective and sensitive detection of CrO₄²⁻ in acidic conditions. The proposed method was based on the special oxidation reaction between non-fluorescent SRBH by potassium dichromate to produce a highly fluorescent rhodamine B, as a product. Under the optimum conditions described, the fluorescence enhancement at 591 nm was good linearly related to the concentration of CrO₄²⁻ from 1.0 × 10⁻⁸ to 3.0 × 10⁻⁷ M (0.42–12.6 ng mL⁻¹) with a correlation coefficient of R² = 0.9989 (n = 10) and a detection limit of 1.5 × 10⁻⁹ M (0.063 ng mL⁻¹). The relative standard deviation (R.S.D.) was 2.0% (n = 6). The proposed method was also successfully applied to the determination of chromium (VI) in drinking water, river water and synthetic samples.     

Simultaneous use of multiple fluorescent reporter dyes for glucose sensing in aqueous solution

The simultaneous use of several fluorescent reporter dyes in a multicomponent boronic acid-based glucose sensing system is reported. In one application, two dyes with widely different emission wavelengths are used to report changes in glucose concentration. A third glucose-insensitive dye was then added to act as a reference dye and provide for a ratiometric correction to the two reporter dye signals. The inclusion of such a reference dye reduces errors arising from sources such as fluctuations in lamp intensity and sample dilution. The simultaneous use of multiple fluorescent reporter dyes     

Shape-selective sensing of lipids in aqueous solution by a designed fluorescent molecular tube

The design, synthesis, and recognition properties of two isomeric calixnaphthalene-type molecular tubes is described. The anti isomer showed strong fluorescence quenching upon titration with various simple lipid guests in water, in which the more hydrophobic guests associated with higher affinity. The syn isomer bound long straight-chain guests tightly with a similar fluorescence-quenching response. However, the syn isomer was more selective, giving an increase in fluorescence upon titration of guests which could not thread through the tube. Thus, the syn isomer is a selective fluorescent sensor for long straight-chain lipids.     

Fluorescent sensing of pyrophosphate and ATP in 100% aqueous solution using a fluorescein derivative and Mn

A new fluorescein derivative has been synthesized for the detection of pyrophosphate (PPi) and ATP in 100% aqueous solution. Chemosensor 1 in the presence of Mn²⁺ (2.5 equiv) displayed selective fluorescent enhancements with PPi and ATP at pH 7.4. among the anions examined. The association constant of 1 in the presence of Mn²⁺ with PPi and ATP was calculated as 4.2 × 10⁴ and 3.5 × 10⁴ M⁻¹.     

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.     

Two-photon fluorescent probe for cadmium imaging in cells

A novel two-photon excited fluorescent probe for cadmium (named as TPCd) was designed and synthesized utilizing a prodan (6-acetyl-2-methoxynaphthalene) derivative as the two-photon fluorophore and an o-phenylenediamine derivative as the Cd(2+) chelator, which possessed favorable photophysical properties and good water-solubility. The probe was designed with a photoinduced electron transfer (PET) mechanism and thus was weakly fluorescent itself. After binding with Cd(2+) which blocked the PET process, the fluorescence intensity of the probe was enhanced by up to 15-fold under one-photon excitation (OPE) and 27-fold under two-photon excitation (TPE), respectively. The two-photon action cross-section (Φδ) of the TPCd-Cd complex at 740 nm reached 109 GM compared to 3.6 GM for free TPCd, indicating the promising prospect of the probe in two-photon application. TPCd chelated Cd(2+) with 1 : 1 stoichiometry, and the apparent dissociation constant (K(d)) was 6.1 × 10(-5) M for the one-photon mode and 7.2 × 10(-5) M for the two-photon mode. The probe responded to Cd(2+) over a wide linear range from 0.1 to 30 μM with a detection limit of 0.04 μM. High selectivity of the probe towards Cd(2+) was acquired in Tris-HCl/sodium phosphate buffer. The probe was pH-independent in the biologically relevant pH range and non-toxic to living cells at reasonable concentration levels, warranting its in vivo applications. Through two-photon microscopy imaging, the probe was successfully applied to detect Cd(2+) uptake in living HepG2 cells.     

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.     

Cross-linking strategy for molecular recognition and fluorescent sensing of a multi-phosphorylated peptide in aqueous solution

In the research field of molecular recognition, selective recognition and sensing of phosphorylated protein surfaces is strongly desirable both for elucidation of protein-protein recognition at the molecular level and for regulation of signal transduction through protein surfaces. Here we describe a new strategy for molecular recognition of a multi-phosphorylated peptide using intrapeptide cross-linking on the basis of coordination chemistry. The present artificial receptor can selectively bind to doubly phosphorylated peptide through multiple-point interactions and fluorescently sense the binding event with an association constant of more than 106 M-1 in neutral aqueous solution.     

Quantum dot-based "turn-on" fluorescent probe for detection of zinc and cadmium ions in aqueous media

Health or environmental issue caused by abnormal level of metal ions like Zn²⁺ or Cd²⁺ is a worldwide concern. Developing an inexpensive and facile detection method for Zn²⁺ and Cd²⁺ is in urgent demand. Due to their super optical properties, fluorescent quantum dots (QDs) have been developed as a promising alternative for organic dyes in fluorescence analysis. In this study, a CdTe QDs-based sensitive and selective probe for Zn²⁺ and Cd²⁺ in aqueous media was reported. The proposed probe worked in fluorescence “turn-on” mode. The initial bright fluorescence of CdTe QDs was effectively quenched by sulfur anions (S²⁻). The presence of Zn²⁺ (or Cd²⁺) can “turn-on” the weak fluorescence of QDs quenched by S²⁻ due to the formation of ZnS (or CdS) passivation shell. Under optimal conditions, a good linear relationship between the fluorescence response and concentration of Zn²⁺ (or Cd²⁺) could be obtained in the range from 1.6 to 35 μM (1.3–25 μM for Cd²⁺). The limit of detection (LOD) for Zn²⁺ and Cd²⁺ were found to be 1.2 and 0.5 μM, respectively. Furthermore, the present probe exhibited a high selectivity for Zn²⁺ and Cd²⁺ over other metal ions and was successfully used in the detection of Zn²⁺ or Cd²⁺ in real water samples.     

Selective sensing of sulfate in aqueous solution using a fluorescent bis(cyclopeptide)

Fluorescence of a bis(cyclopeptide) in which two cyclohexapeptide moieties with alternating L-proline and 6-aminopicolinic acid subunits are attached to a 4,4'-bis(dimethylamino)biphenyl linker is quenched in 1:1 (v/v) water/methanol in the presence of sulfate. Of eight other anions tested, none produced a similar effect. This bis(cyclopeptide) allows the qualitative and quantitative detection of sulfate even in the presence of an excess of chloride anions. Calculations provided insight into the causes of fluorescence quenching and anion selectivity.     

A sensitive colorimetric and ratiometric fluorescent probe for mercury species in aqueous solution and living cells

A highly sensitive and selective fluorescent probe for inorganic and organic mercury species displays colorimetric and ratiometric response in a buffer solution via mercury promoted cleavage reaction. The probe is demonstrated to detect CH(3)HgCl in living cells.     

A new ESIPT-based fluorescent probe for highly selective and sensitive detection of HClO in aqueous solution

A new ESIPT-based fluorescent probe, PHC2, for the detection of hypochlorous acid has been rationally designed and developed. Endowed by the specific reaction between hypochlorous acid and phenyl azo group, PHC2 features high degree of selectivity and sensitivity for HClO with a low detection limit (13.2 nM) under physiological conditions in neutral aqueous solution.