•A novel sensor for ultrasensitive detection of PA in aqueous media by dual mechanism.•The limit of detection of sensor 4 is as low as 0.57 ppb PA in aqueous media.•Sensor 4 can detect PA as highly sensitive as 11.46 ag cm−2 by contact mode.•It is practically applicable for sensing PA in real samples and vapor phase.A 2,6-dibenzimidazole-appended naphthalene derivative flanking with two N-alkyl chains (sensor 4) was designed and applied for highly sensitive detection of picric acid (PA) in aqueous media. Driven by the hydrophobicity of alkyl chain and π-π stacking effect of aryl, sensor 4 can undergo self-assembly to form an orderly rod-like structure in H2O/THF (v/v, 90/10) solution, as shown by the dynamic light scattering (DLS) and scanning electron microscopy (SEM) studies. Sensor 4 shows high selectivity and sensitivity toward PA over other nitroaromatic explosives. DFT calculations and 1H NMR, the time-correlated single photon counting (TCSPC) experiments confirm that the quenching mechanism is due to both electron and energy transfer from the electron-rich sensor 4 to the electron-deficient PA. Sensor 4 can detect as low as 0.57 ppb PA in aqueous media and 11.46 ag cm−2 PA by contact mode. Importantly, sensor 4 exhibits low interference against common solvents, metal ions and anions. Thus, it is practically applicable for sensing PA in real environmental samples and vapor phase.Download high-res image (238KB)Download full-size image

Here we report the facile synthesis of two triphenylethylene-modified pyrrolopyrrole aza-BODIPY dyes with an aggregation-enhanced emission feature. NIR-emitting nanoparticles with remarkable photostability properties and applications in bioimaging were generated due to their good dispersity in water and biocompatibility.

In this paper, a nitroolefin functionalized probe DPP-NO2 was designed and synthesized as a selective fluorescent probe for detection of hydrogen sulfide (H2S). The specific reduction reaction between the nitro group and H2S gave 800-fold fluorescence turn-on at 550 nm in the fluorescence emission spectrum, along with a 21 nm blue-shift from 506 nm to 485 nm in the absorption spectrum as well as a color change from pink to light yellow. In addition, high selectivity, fast response (3 minutes) and low detection limit of 5.2 nM of the probe DPP-NO2 for H2S detection was observed. What is more, through the fluorescence turn-on signal toward H2S in Hela cells, probe DPP-NO2 was successfully applied to monitor H2S in living Hela cells.

Two conjugates of tetraphenylethene (TPE) and diketopyrrolopyrrole (DPP) were synthesized and their fluorescence properties were investigated. Both DPP1 and DPP2 show intense fluorescence and large Stokes shifts in both solution and solid state. In dilute THF, DPP1 and DPP2 show emission peaks at 606 nm and 632 nm with a Φf value of 32% and 11%, respectively. However, the powder samples for DPP1 and DPP2 emit at 650 nm and 615 nm with a Φf value of 13% and 7%, respectively. Moreover, DPP2 shows remarkable selectivity and specificity toward CN− over other anions. The color changed from pink to colorless when CN− was added to DPP2 in THF. The maximum emission intensity at 632 nm is quenched 94.6%, which constitutes the fluorescence signature for cyanide detection. The detection limit is 0.3 μM using the fluorescence spectra changes, which is far lower than the WHO guideline of 1.9 μM.

A novel electron donor–acceptor polymer (N1) containing diketopyrrolopyrrole as an electron acceptor and triphenylamine as an electron donor has been designed and synthesized. N1 is shown to possess the remarkable dual properties of solvatochromism and aggregation-induced emission (AIE). Importantly, N1 is found to serve as a fluorescence indicator for the qualitative and quantitative detection of low-level water in THF. Moreover, the quaternization of N1 by CH3I gave ammonium-salt P1. A selective fluorescence turn-on probe for bovine serum albumin (BSA) detection and quantification is developed by taking advantage of the aggregating process of P1. It is found that the intrinsic weak fluorescence of P1 in DMSO/PBS (1:1, v/v) increases to 2.9-fold after the addition of 50 μM BSA through electrostatic complexation and hydrophobic interaction.

A water-soluble cationic conjugated polyelectrolyte (P1) containing fluorene, BODIPY and diacetylene moieties was synthesized and characterized. P1 showed two main absorption bands with maxima at 360 and 574 nm as well as fluorescence maxima at 648 nm due to the incorporation of BODIPY into the polymer backbone. Addition of CT DNA can quench the emission of P1 because of the formation of a P1/CT DNA complex, which was demonstrated by UV–vis spectra and dynamic light scattering (DLS) analyses. Cellular imaging results indicated P1 could be utilized as cellular imaging of HeLa cells, where red fluorescence was observed in the partial cytoplasm. Moreover, CCK-8 assay showed P1 had a low cytotoxicity.

•A new boron-dipyrromethene (BODIPY) derivative bearing a boronate group (1) had been designed and synthesized.•The addition of F− and CN− to 1 in THF solution induced a rapid color change from rose pink to indigo and faint pink, respectively.•The emission color of the 1 changed from red to indigo and green in presence of F− and CN−, respectively.•The preferential binding of cyanide occurs at the boron center of BODIPY core. On the other hand, fluoride binding occurs at the boron center of BODIPY core and boronate moiety.A new boron-dipyrromethene (BODIPY) derivative bearing a boronate group (1) had been designed and synthesized as a colorimetric and fluorescent chemosensor for F− and CN− with no interference from each other. The addition of F− and CN− to 1 in THF solution induced a rapid color change from rose pink to indigo and faint pink, respectively. At the same time, the emission color of the 1 changed from red to indigo and green in presence of F− and CN−, respectively. 19F and 1H NMR spectra indicated that the preferential binding of cyanide occurred at the boron center of BODIPY core. On the other hand, fluoride binding occurred at the boron center of BODIPY core and boronate moiety.A new boron-dipyrromethene (BODIPY) derivative bearing a boronate group (1) had been designed and synthesized as a colorimetric and fluorescent chemosensor for F− and CN− with no interference from each other.

•A conjugated polymer (P1) containing porphyrin, fluorene and phenylene moieties in the main chain and and mannose in the side chainshas been synthesized.•Addition of Con A resulted in the quenching of the poly(fluorene–phenylene) emission at 456 nm with simultaneous enhancement of porphyrin emission at 625 nm, exhibiting visual emission color change of P1 from blue to purple.•This FRET probe could be used to quantify Con A, providing a low LOD (6 × 10−12 M).•P1 was insensitive to nonspecific proteins and all of the anions.A conjugated polymer (P1) with pendant mannose linkages has been designed and synthesized, which is a highly efficient ratiometric probe for Concanavalin A (Con A) detection. P1 is doped with a low-bandgap fluorophore, porphyrin, which in conjunction with favorable spectral overlap between the poly(fluorene–phenylene) and porphyrin facilitates efficient FRET process in aqueous solutions in presence of Con A. UV/vis spectroscopy and dynamic light scattering studies indicate that P1 and Con A form into nanoparticles by carbohydrate–lectin interactions. Addition of Con A results in the quenching of the poly(fluorene–phenylene) emission at 456 nm with simultaneous enhancement of porphyrin emission at 625 nm, exhibiting visual emission color change from blue to purple. The intensity ratio of I625/I456 is enhanced 9.3-fold when the concentration of Con A reaches 10 μmol/L. Nonspecific proteins including bovine serum albumin (BSA), pepsin (Pep), lysozyme (Lys) show poor fluorescence response, thus highlighting the selectivity and sensitivity of the FRET-based sensing of Con A by P1. Moreover, P1 shows low cytotoxicity by CCK-8 assay, which makes its potential application as fluorescent agent for cellular imaging.An efficient ratiometric probe for Con A detection based on a mannose-substituted conjugated polymer (P1) through aggregation-enhanced FRET has been developed.

•A novel AIE-active diketopyrrolopyrrole (DPP) derivative containing anthranone and para-iodophenyl units (Monomer 1) is synthesized.•P1 based on Monomer 1 emits purple fluorescence with two emission peaks at 440 and 625 nm in DMSO and is AIE-inactive.•A fluorescence turn-on probe for bovine serum albumin (BSA) detection and quantification is developed by taking advantage of deaggregating process of P1.A novel AIE-active diketopyrrolopyrrole (DPP) derivative containing anthranone and para-iodophenyl units (Monomer 1) are synthesized. Due to the presence of polymerisable group, Monomer 1 can be polymerized with 2,7-diethynyl-9,9-bis[6′-(N,N-diethylamino)-octyl]fluorene to yield corresponding neutral polymer N1, where AIE-acitve DPP and ACQ-active fluorene units are linked together with a flexible alkyl spacer in main chain. N1 is transformed to its polyelectrolyte P1via ionization by CH3I. P1 emits purple fluorescence with two emission peaks at 440 and 625 nm in DMSO and is AIE-inactive due to its amphiphilic performance and the presence of ACQ-active fluorene unit. A fluorescence turn-on probe for bovine serum albumin (BSA) detection and quantification is developed by taking advantage of the deaggregating process of P1. It is found that the fluorescence intensity of P1 in DMSO/PBS buffer (v/v = 1/1) at 450 and 645 nm is increased by 2.94 and 2.11-fold when the concentration of BSA increased from 0 to 70 μM. In addition, P1 can be utilized as a fluorescent probe for cellular imaging of HeLa cells, where red fluorescence is observed in the cytoplasm. The CCK-8 assay shows that the cytotoxicity of P1 is low.Fluorescence “turn-on” detection of BSA based on the cationic poly(diketopyrrolopyrrole-co-ethynylfluorene) has been developed.

A new colorimetric probe 1 comprising a diketopyrrolopyrrole-based Michael receptor, which recognized cyanide anions with high selectivity, was designed and synthesized. Addition of CN− aqueous solution to 1 in THF resulted in a rapid color change from pink to light yellow together with a large blue shift from 530 to 487 nm, while other anions did not induce any significant color change. Furthermore, Michael addition of cyanide to 1 elicited 94% fluorescence quenching at 640 nm accompanied by appearance of a weak new emission at 560 nm, which constituted the fluorescence signature for cyanide detection. The detection limits were determined to be 0.75 μM using the fluorescence spectral changes, which were far lower than the WHO guideline of 1.9 μM. Moreover, 1-based test strips could successfully detect CN− in water solutions.

Two new diketopyrrolopyrrole (DPP)-based compounds were synthesized and their fluorescence properties were investigated. DPP1 containing two diethylamino groups possess a typical aggregation-induced emission (AIE) property. Namely, when fraction of water (fw, by volume) reaches 90%, the emission intensity is 13.7 times higher than that in THF. Owing to the AIE effect and chemical reactivity of diethylamino group towards H+ ions, DPP1 starts to aggregate at basic conditions (pH = 10.59). At a pH of 12.36, the emission intensity of DPP1 is 6.67-fold compared to that at pH 2.53, which indicates that DPP1 can work as a fluorescent pH sensor. On the other hand, DPP2 is an ammonium-salt containing compound and has no AIE phenomenon in solution, but shows emission enhancement in solid state and in the increasing viscosity system. DPP2 can interact strongly with BSA to amplify its emission with 7.65-fold fluorescence enhancement in presence of 100 μM BSA. Therefore, DPP2 is a fluorescent “turn on” biological probe for BSA detection. In addition, DPP2 can be utilized as a fluorescent probe for cellular imaging of HeLa cells, where red fluorescence is observed in the cytoplasm. The CCK-8 assay shows that the cytotoxicity of DPP2 is low.

A new BODIPY-containing conjugated polymer (P1) had been designed and synthesized as a colorimetric and fluorescent chemosensor for F− and CN−. The combination of advantages of both reaction based sensors and conjugated polymer sensors offered its highly sensitive and selective recognition of F− and CN− with no interference from each other. The addition of F− and CN− to P1 solution induced a rapid color change from purple to orange and faint yellow, respectively. At the same time, the emission color of the P1 solution changed from red to yellow and yellowish green in presence of F− and CN−, respectively. 11B, 19F and 1H NMR spectra indicated that addition of fluoride and cyanide result in a nucleophilic displacement to break a BN bond of P1. In addition, the cell imaging experiments demonstrated that P1 could be successfully applied as a bioimaging agent with good biocompatibility.Highly selective and sensitive detection of F− and CN− ions simultaneously by a reaction-based BODIPY-containing conjugated polymer (P1) has been developed.

Three novel coumarin-containing conjugated polyelectrolytes (P1–P3) containing coumarin, carbazole, fluorene and phenylene moieties were successfully synthesized by Suzuki coupling reaction. The narrow bandgap coumarin–carbazole units and the wide bandgap fluorene–phenylene units in P1–P3 might form energy donor–acceptor molecule architectures, in which coumarin–carbazole units serve as an acceptor of the fluorescent resonance energy transfer (FRET). The addition of calf thymus DNA resulted in efficient FRET from fluorene–phenylene (energy donor) to coumarin–carbazole (energy acceptor) unit for P1, which caused the solution fluorescent color to change from blue to light green. In addition, P1 can be utilized as a reliable fluorescent probe for cellular imaging of human adult skin fibroblast cells, where blue and green fluorescence were observed in the cytoplasm by use of different excitation wavelength. Subsequently, the water-soluble and fluorescent P1 were used as high sensitive DNA sensor and effective fluorescent cell labeling agents with dual emission pathways.

A new BODIPY-containing conjugated polymer (P1) had been designed and synthesized as a colorimetric and fluorescent chemosensor for F− and CN−. The combination of advantages of both reaction based sensors and conjugated polymer sensors offered its highly sensitive and selective recognition of F− and CN− with no interference from each other. The addition of F− and CN− to P1 solution induced a rapid color change from purple to orange and faint yellow, respectively. At the same time, the emission color of the P1 solution changed from red to yellow and yellowish green in presence of F− and CN−, respectively. 11B, 19F and 1H NMR spectra indicated that addition of fluoride and cyanide result in a nucleophilic displacement to break a BN bond of P1. In addition, the cell imaging experiments demonstrated that P1 could be successfully applied as a bioimaging agent with good biocompatibility.Highly selective and sensitive detection of F− and CN− ions simultaneously by a reaction-based BODIPY-containing conjugated polymer (P1) has been developed.Download high-res image (164KB)Download full-size image

Here we report the facile synthesis of two triphenylethylene-modified pyrrolopyrrole aza-BODIPY dyes with an aggregation-enhanced emission feature. NIR-emitting nanoparticles with remarkable photostability properties and applications in bioimaging were generated due to their good dispersity in water and biocompatibility.