Xiaofeng Yang

A differentially selective probe based on diketopyrrolopyrrole with fluorescence turn-on response to Fe3+, and dual-mode turn-on and ratiometric response to Au3+, and its application in living cell imaging

A diketopyrrolopyrrole-based probe DPP-PyR was able to recognize Fe(3+) and Au(3+) with fluorescent turn-on response via different emission modes with relatively low detection limit. Moreover, DPP-PyR exhibited preferential second mode of selectivity for Au(3+) as it ratiometrically displaced Fe(3+) from the [DPP-PyR+Fe(3+)] complex. Furthermore, the imaging experiments indicated that this probe was cell-permeable and could be used to detect Fe(3+) and Au(3+) ions within living cell. To the best of our knowledge, it was the first probe for detection Fe(3+) and Au (3+) at the same time ever reported.

A new diketopyrrolopyrrole-based probe for sensitive and selective detection of sulfite in aqueous solution

A new probe was synthesized by incorporating an α,β-unsaturated ketone to a diketopyrrolopyrrole fluorophore. The probe had exhibited a selective and sensitive response to the sulfite against other thirteen anions and biothiols (Cys, Hcy and GSH), through the nucleophilic addition of sulfite to the alkene of probe with the detection limit of 0.1 μM in HEPES (10 mM, pH 7.4) THF/H2O (1:1, v/v). Meanwhile, it could be easily observed that the probe for sulfite changed from pink to colorless by the naked eye, and from pink to blue under UV lamp after the sulfite was added for 20 min. The NMR and Mass spectral analysis demonstrated the expected addition of sulfite to the C=C bonds.

Novel fluorescent sensors based on benzimidazo[2,1-a]benz[de]isoquinoline-7-one-12-carboxylic acid for Cu2+

Fluorescent sensors of N-(4-methylpiperazin-1-yl)benzimidazo[2,1-a]benz[de]isoquinoline-7-one-12-carboxylamide (C1) and its corresponding quaternary ammonium salt (C2) were prepared. C1 showed 45-fold fluorescence turn-on response towards Cu2+ with a detection limit of 5.7 × 10−8 mol L−1 in acetonitrile–H2O (9:1) buffer solution and C2 showed 18-fold fluorescence enhancement towards Cu2+ with a detection limit of 3.4 × 10−7 mol L−1 in the same condition. The Cu2+ sensing of C1 and C2 were both based on the photoinduced electron transfer (PET) process. Such behaviors confirmed that the benzimidazo[2,1-a]benz[de]isoquinoline-7-one-12-carboxylic acid based C1 and C2 could be utilized as fluorescent sensors for Cu2+. The mechanism of fluorescence enhancement of C1 towards Cu2+ was verified by DFT/TDDFT calculation using Gaussian 03. In addition, an obvious color change was observed when an aqueous solution of C2 was treated with aqueous NaOH. Such behavior confirms that C2 could be used as a fluorescent OH− sensor in water.

Colorimetric and fluorogenic signalling of fluoride ions by diketopyrrolopyrrole-based chemosensor

A new colorimetric and on–off fluorescence sensor based on diketopyrrolopyrrole (DPP) was synthesized for detection of fluoride anion. The sensor displayed a rapid responsivity and high selectivity and sensitivity towards F− over other anions, and it also exhibited a very low detection limit of 4.07 × 10−8 M. The signaling process was confirmed by UV-vis, fluorescence measurements as well as 1H and 19F NMR spectroscopy. The experimental results revealed that the formation of anionic species from deprotonation of the hydrazone N–H moiety by fluoride ion was responsible for the spectral changes. Density function theory calculations were conducted to rationalize the optical response of the sensor.

Effects of substitution position on crystal packing, polymorphism and crystallization-induced emission of (9-anthryl)vinylstyrylbenzene isomers

Three (9-anthryl)vinylstyrylbenzene (ASB) position isomers were synthesized and compared. Substitution position affects temperature-induced polymorphism, crystal packing and crystallization-induced emission (CIE) properties. Different from 1,2-ASB and 1,4-ASB, 1,3-ASB undergoes a crystal-to-crystal phase transition upon heating. The crystal structure of a new phase (1,3-ASB-β) was successfully solved. Thus, the solid emission of 1,3-ASB could be tuned by polymorphism. In contrast, the solid emission of 1,4-ASB is controlled by its crystallinity. In the crystal structures of 1,2-ASB and 1,3-ASB-β, the adjacent interacting anthryls are inclined to adopt an edge-to-face configuration with C–H⋯π interactions. In contrast, the adjacent anthracene rings in the 1,4-ASB crystals are parallel to each other with π⋯π interactions. Furthermore, multiple intermolecular interaction modes such as C–H⋯π and H⋯H interactions coexist in the crystal structure of 1,4-ASB, which collectively results in a closer packing. Interestingly, 1,4-ASB displays CIE behaviour. In contrast, the emission of the other two isomers is quenched in the solid state. The effect of substitution position on the photophysical properties is systematically studied.

Highly sensitive detection of Hg2+ in aqueous solution using cationic polythiophene derivatives

Two novel water-soluble conjugated polymers poly{3-[1-(2-trimethylammoniumacetyl)piperidine-4-methylene]thiophene-2,5-diyl chloride} (PTAPT-Cl) and poly{3-[1-(2-trimethylammoniumbutyryl)piperidine-4-methylene] thiophene-2,5-diyl chloride} (PTBPT-Cl) have been synthesized via chemical oxidative polymerization and applied as a colorimetric and fluorometric probe for the detection of metal ions. Moreover, the fluorescence detection of metal ions using previously synthesized poly[N,N,N-trimethyl-4-(thiophen-3-ylmethylene)cyclohexanaminium chloride] (PTCA-Cl) and poly[3-(1,1′-dimethyl-4-piperidinemethylene)thiophene-2,5-diyl chloride] (PDPMT-Cl) was also investigated and discussed. All four conjugated polymers exhibited high sensitivity and selectivity to Hg2+ with a fluorescence “turn-off” mode at pH 3 in aqueous solutions. The best detection limit was as low as 10−9 M without interference from other common metal ions. Consequently, the distinctive quenching of the emission bands in the presence of various metal ions can lead to qualitative and quantitative Hg2+ detection in aqueous solution by a new approach using cationic polythiophene derivatives.

Extraction of U(VI) with N , N , N ′, N ′-tetraoctyl diglycolamide from nitric acid solution

The extraction of U(VI) from nitric acid solution with N,N,N′,N′-tetraoctyl diglycolamide (TODGA) has been investigated. The influence of diluents, nitric acid concentrations, TODGA concentration and salting-out agents on the extraction distribution ratio was studied. The extraction mechanism was established and the stoichiometry of the main extracted species was confirmed to be UO2(NO3)2·2TODGA. The extraction of UO22+ varies with the nature of diluents, sulfonated kerosene and dodecane gave high extraction distribution ratio.

Highly selective ratiometric fluorescent probe based on diketopyrrolopyrrole for Au3+: an experimental and theoretical study

A diketopyrrolopyrrole-based fluorescent probe 1 was explored as a ratiometric probe for selective detection of Au3+, with the detection limit of 18 nM. The probe displayed an absorption maximum at 528 nm and a strong red fluorescence at 610 nm. In the presence of Au3+, the absorption and emission band blueshifted to 488 and 555 nm, respectively. Correspondingly, the color of the probe solution changed from orange to flesh color, and the fluorescence changed from orange to yellow-green. NMR and HRMS spectral analysis demonstrated that the selective ratiometric fluorescence response of probe 1 with Au3+ involved a selective Au3+-mediated hydrolyzation and oxidization reactions using a catalytic amount of Au3+. In addition, the ratiometric response of probe 1 was rationalized by DFT and TDDFT calculations.

A diketopyrrolopyrrole-based fluorescence turn-on probe for the detection of Pb2+ in aqueous solution and living cells

A diketopyrrolopyrrole-based fluorescent probe DPP-HBT bearing a benzothiazole hydrazone motif exhibited an obvious fluorescent turn-on response toward Pb2+ ions with a low detection limit of 2.3 × 10−10 M in aqueous solution. Furthermore, the imaging experiments indicated that this probe was cell-permeable and could be used to detect Pb2+ ions within living cells.

Colorimetric chemosensors based on diketopyrrolopyrrole for selective and reversible recognition of fluoride ions

A series of colorimetric and reversible receptors for fluoride anions based on diketopyrrolopyrrole (DPP) were designed and synthesized successfully. The position of nitro substituent on the phenylhydrazide affected the alteration of photophysical properties to varying degrees. While the photoluminescence intensity of receptor 1 was weaker than that of receptor 2 and receptor 3 on account of the formation of intramolecular hydrogen bond deriving from oxygen atom of nitro substituent and hydrogen atom of hydrazide. The receptor 2 was a preferable chemosensor for responding fluoride anions. The fluorescence was quenched in the presence of fluoride anion resulted from the photo-induced electron transfer (PET) effect from the amide. The formation of deprotonation species, which produced by hydrazide NH moiety and F- was answerable for the spectral changes. Especially, the spectral and color responses of receptors could be switched back and forth successively by adding F- and HSO4- anions in DMSO solution. These receptors could response fluoride anion sensitively, visually and selectively in a manner of reversible with a low determination.