This paper reports a new ratiometric probe for the detection of adenosine 5′-triphosphate (ATP) that is based on the binding-induced modulation of fluorescence resonance energy transfer (FRET) coupled with the aggregation-caused quenching (ACQ) sensing mechanism. The introduction of coumarin fluorophores as FRET donors into the side-chain of polythiophene (PT) as the FRET acceptor provides the ratiometric probe. Upon addition of ATP, the formation of a polymer/ATP complex leads to the conformational changes of the PT backbone from a random coil to the planar conformation and aggregation. As such, the ratiometric ATP detection can be achieved by taking advantage of spectral overlap changes to modulate the FRET efficiency from coumarin fluorophores to the PT backbone before and after the addition of ATP, coupled with ACQ. The probe exhibited a clear seesaw-type dual-emission signal change upon binding with strong affinity (Kapp = 3.12 × 104 M−1) to ATP in aqueous solution, whereas no obvious emission changes were observed with ADP, AMP or various other anions. The probe can also be utilized for naked-eye detection of ATP and real-time monitoring of the ATP hydrolysis reaction by apyrase under physiological pH conditions.

Polycondensation of perylene diimide (PDI) diamines with a 2,2′:6′,2′′-terpyridine (tpy)-containing dibromide gives a new fluorescent polymeric chemosensor (L) with good water solubility. L exhibits good selectivity for Fe3+ ions over a wide range of tested metal ions Ag+, K+, Na+, Fe2+, Cu2+, Al3+, Cr3+, Mn2+, Mg2+, Ni2+, Ca2+, Hg2+, Pd2+, Ba2+, Cd2+, Co2+ and Zn2+ in aqueous solution. The binding of Fe3+ to chemosensor L leads to significant emission bands at 548 nm and 591 nm, respectively, because the complexation of Fe3+ with the tpy moiety of L blocks the photoinduced electron transfer (PET) from tpy units to PDI units. A 1:2 stoichiometry was found for the complex formed by L and Fe3+ by Job's plot. The association constant (Ka) of Fe3+ binding in chemosensor L is 1.32 × 108 M−2. L can be used to detect Fe3+ over a wide pH range of 5.0–9.0. Moreover, by taking advantage of its instant fluorescence turn-on specific to Fe3+, L is used as a fluorescent probe to monitor the Fe3+/Fe2+ transition in the presence of reducing agents such as Na2S2O3 or ascorbic acid (Vc) in water. L can also work well in biological samples, which gives access to the detection of Fe3+ in an organism.

A sensitive fluorescent and colorimetric dual-modal probe for the detection of ATP has been developed based on a strategy of self-promoting aggregation of a cationic polythiophene derivative bearing anthracene groups in the side chain with a detection limit as low as 10−9 M.

In this paper, hexagonal bipyramids and X- and polycrystal-shaped twins of cholic acid are acquired through the acidic hydrolysis of its ester hydrogel. The growth mechanism is proposed on the basis of the hydrophobic swallowtail-shaped tetramers found in the single-crystal structure.

Herein, a new conjugated poly(pyridinium salt) derivative L was synthesized by ring-transmutation polymerization reaction for the purpose of sensitive and selective fluorescence sensing of DNA. Cationic L exhibits aggregation-induced emission (AIE) characteristics that is weakly emissive in solution but highly luminescent in the aggregate state. Based on its AIE activity, a fluorescence turn-on biosensor for calf thymus DNA (ctDNA) detection is developed, which shows excellent selectivity with a detection limit down to the 10−8 M−1 in CH3CN–phosphate buffer solution (PBS) (2 mM, pH 7.4) (v/v 1:1). Further, the interactions between L and ctDNA are carefully investigated by UV-vis absorption spectra, dynamic light scattering (DLS) measurements, thermal denaturation studies, circular dichroism (CD) measurements, as well as competing experiments with ethidium bromide (EB). More interestingly, L exhibits selective fluorescence enhancement induced by double-stranded DNA (dsDNA), therefore, L was also successfully utilized as fluorescent probe to follow the ctDNA cleavage process by bovine pancreatic deoxyribonuclease I (DNase I).

A new conjugated poly(pyridinium salt) derivative (P1) containing heterocyclic phenanthridine moieties in the main chain with tosylate counterions was prepared via a ring-transmutation polymerization reaction. Its chemical structure was established using NMR and FTIR spectra. Its number-average molecular weight (Mn) and polydispersity were 14 430 and 1.456, respectively, as determined by gel permeation chromatography (GPC). The interaction of P1 with calf thymus DNA (ctDNA) in an ethanol-Tris-HCl buffer (2 mm, pH 7.4) (v/v=1:1) was investigated by ultraviolet–visible, fluorescence, circular dichroism spectroscopy, and dynamic light scattering (DLS) measurements. The electrostatic attraction and intercalation interaction between P1 and ctDNA resulted in a significant fluorescence quenching of polymer P1 in the ethanol–Tris-HCl buffer, and the ratio of fluorescence intensity at 523 nm in the absence of ctDNA (F0) to that in the presence of ctDNA (Fi) was linearly proportional to the concentration of ctDNA within the range of 0–6.0 μm. Therefore, the conjugated polyelectrolyte is expected to be used as a new fluorescent probe for the label-free detection of DNA.

A series of N-isopropylacrylamide and methacrylate derivative random copolymers with various contents of cholic acid groups in the side chain are synthesized by free radical polymerization. These thermoresponsive random copolymers can organize themselves into large vesicles in water upon heating, accompanied by gradual phase transitions from transparent polymer solutions to turbid solutions and then to white hydrogels. The white vesicle hydrogels display non-elastic deformation and shrink. They can re-dissolve directly upon cooling. Further, X-ray diffraction results indicate the existence of crystalline regions on the vesicle membrane. Based on these results, the possible formation mechanism of the fiber-layer structures on the vesicle membrane is also discussed. It is noteworthy that the gel-forming temperatures of the resultant copolymers below 37 °C which indicate the vesicle gels may find applications as injectable implant systems for sustained drug delivery.

•Pd-catalysed oxidative C–H/C–H coupling reaction achieves the homopolymerization of thiazole derivatives.•Conjugated polythiazole derivatives exhibit interesting photoelectric properties.•This synthetic strategy is expected to be applied in direct oxidative C–H/C–H coupling polymerization of other heteroarenes.Pd-catalysed oxidative C–H/C–H coupling homopolymerization of thiazole derivatives with different numbers (n = 1–3) of thiophene as bridged units was described. It represents a facile and practical methodology to prepare thiazole-based conjugated polymers in excellent yields. Three conjugated polythiazole derivatives (P1–P3) were synthesized by utilization of ligand-free Pd(OAc)2 as a catalyst in the presence of Ag2CO3 and KOAc. Their chemical structure and molecular weights were established by 1H and 13C NMR, as well as size exclusion chromatography (SEC), respectively. Polymerization conditions including amounts of Pd(OAc)2 and oxidant, solvent medium and other catalysts were screened and optimized. Furthermore, the optical and electrical properties of the resulting polymers P1–P3 were investigated by UV-vis and fluorescent spectroscopy, as well as cyclic voltammetry, respectively, and the influence of the length of bridged units on the photoelectric properties of these polymers was also discussed. This synthetic strategy would be applied in direct oxidative C–H/C–H coupling polymerization of other heteroarenes to construct versatile π-conjugated polymers for optoelectronic applications.

A new, simple, mild, atom economical homopolymerization method through Pd-catalyzed oxidative C–H/C–H coupling was developed for the preparation of a series of 5-alkyl[3,4-c]thienopyrrole-4,6-dione-based conjugated polymers.

Cholic acid (CA) is a primary bile acid which possesses facial amphiphilicity and self-assembly ability. CA is slightly soluble in water, which makes it impossible to form the self-assembled structures spontaneously in aqueous solutions. To increase the water solubility, a cholic acid ester (CA-4EG) with a hydrophilic tail (tetraethyleneglycol, 4EG) was synthesized, which forms self-assembled structures in aqueous solutions. The self-assembled crystals of CA are obtained by acidic hydrolyzing the ester bond of CA-4EG. The rhombic hydrophobic tetramer structure units and fiber-layer structures are found in the self-assembled crystals of CA.

Herein, a new conjugated poly(pyridinium salt), poly{(4,4′-(1,4-phenylene)bis(2,6-diphenylpyridinium))-co-N-butyl-3,6-carbazolylene ditosylate} (Poly1), exhibits aggregation-induced emission (AIE) characteristics. It is weakly emissive in solution but highly luminescent in the aggregate state. A fluorescence turn-on biosensor for calf thymus DNA (ctDNA) detection and quantification is developed by taking advantage of complexation-induced aggregation of Poly1, which increases the polymer fluorescence in aqueous solution. It was found that the fluorescence intensity of Poly1 in ethanol–phosphate buffer solution (2 mM, pH 7.4) (v/v 1:1) was increased up to about 2.4 folds when the concentration of ctDNA increased from 0 to 95 μM along with the blue-shift of the emission peak from 604 to 586 nm. In the concentration range from 0 to 60 μM, the ratio of the increase in photoluminescent intensity at 604 nm in the presence of ctDNA (IctDNA – I0) to that in the absence of ctDNA (I0) is linearly proportional to the concentration of ctDNA with a correlation coefficient of 0.997. The detection limit was calculated to be of 1.2 μM based on the results of fluorescence titration.

A novel strategy to design a fluorescent chemosensor for OCl− which can be used over a pH span of 6–11 by integrating the reactive phenylhydrazo group within rhodamine 6G has been achieved. Upon the reaction with OCl−, a significant fluorescence enhancement was triggered with a detection limit down to the 10−9 M range.

Based on an oxidized irreversible ring-opening process of the spirolactam of rhodamine 6G to turn on the fluorescence pathway, a highly sensitive, selective fluorescent and easy accessible chemosensor for ClO− has been reported. Upon reaction of the chemosensor with ClO− ions, a fluorescent enhancement factor over 60-fold is observed. The chemosensor shows a remarkably high selectivity to discriminate between ClO− and other ROS, such as H2O2, TBHP etc., and a wide range of the environmentally and biologically relevant anions and metal ions. The oxidized irreversible ring-opening process of the chemosensor also triggers a visible colorimetric change from colorless to pink, leading to production of both “naked-eye” and fluorimetric detection of ClO− anion. The detection limit is estimated to be 2 × 10−8 M based on a signal-to-noise ratio of 3:1 method. The chemosensor can be used within a pH span of 6–11.5. The chemosensor also shows excellent performance in natural water samples.

A highly sensitive and selective fluorescent chemosensor SC1 for Ag+ based on a coumarin–Se2N chelating conjugate has been synthesized and characterized. Due to inhibiting a photoinduced electron transfer (PET) quenching pathway, a fluorescent enhancement factor of 4-fold is observed under the binding of the Ag+ cation to the chemosensor SC1 with a detection limit down to the 10−8 M range.

A novel water soluble Hg2+-selective chemosensor 1 with hemicyanine as fluorescent reporting group and NO2Se2 chelating unit as ion binding site was reported. Chemosensor 1 shows a specific Hg2+ selectivity and discrimination between Hg2+ and chemically similar ions in conjunction with a visible colorimetric change from red to colorless, potentially leading to both “naked-eye” and fluorometric detection of Hg2+ cations.

A novel strategy to design a fluorescent chemosensor for OCl− which can be used over a pH span of 6–11 by integrating the reactive phenylhydrazo group within rhodamine 6G has been achieved. Upon the reaction with OCl−, a significant fluorescence enhancement was triggered with a detection limit down to the 10−9 M range.

A new, simple, mild, atom economical homopolymerization method through Pd-catalyzed oxidative C–H/C–H coupling was developed for the preparation of a series of 5-alkyl[3,4-c]thienopyrrole-4,6-dione-based conjugated polymers.

A highly sensitive and selective fluorescent chemosensor SC1 for Ag+ based on a coumarin–Se2N chelating conjugate has been synthesized and characterized. Due to inhibiting a photoinduced electron transfer (PET) quenching pathway, a fluorescent enhancement factor of 4-fold is observed under the binding of the Ag+ cation to the chemosensor SC1 with a detection limit down to the 10−8 M range.

A novel water soluble Hg2+-selective chemosensor 1 with hemicyanine as fluorescent reporting group and NO2Se2 chelating unit as ion binding site was reported. Chemosensor 1 shows a specific Hg2+ selectivity and discrimination between Hg2+ and chemically similar ions in conjunction with a visible colorimetric change from red to colorless, potentially leading to both “naked-eye” and fluorometric detection of Hg2+ cations.

A sensitive fluorescent and colorimetric dual-modal probe for the detection of ATP has been developed based on a strategy of self-promoting aggregation of a cationic polythiophene derivative bearing anthracene groups in the side chain with a detection limit as low as 10−9 M.