A novel AIE-active imidazolium macrocyclic ratiometric fluorescence sensor for pyrophosphate anion.

An imidazolium bridged macrocyclophane was synthesized as a ratiometric fluorescence sensor with aggregation-induced emission (AIE) characteristic to detect pyrophosphate anion with high selectivity among various anions. In the presence of zinc ion, macrocyclophane can form aggregates through complexation with pyrophosphate anion and emit ratiometric fluorescence, resulting from an enhancement in its aggregate-state emission and a reduction in its monomer emission. This AIE-active macrocycle showed great potential as a ratiometric fluorescence receptor.

A Highly Efficient Fluorescent Sensor Based on AIEgen for Detection of Nitrophenolic Explosives.

The detection of nitrophenolic explosives is important in counterterrorism and environmental protection, but it is still a challenge to identify the nitroaromatic compounds among those with a similar structure. Herein, a simple tetraphenylethene (TPE) derivative with aggregation-induced emission (AIE) characteristics was synthesized and used as a fluorescent sensor for the detection of nitrophenolic explosives (2, 4, 6-trinitrophenol, TNP and 2, 4-dinitrophenol, DNP) in water solution and in a solid state with a high selectivity. Meanwhile, it was found that only hydroxyl containing nitrophenolic explosives caused obvious fluorescence quenching. The sensing mechanism was investigated by using fluorescence titration and 1H NMR spectra. This simple AIE-active probe can potentially be applied to the construction of portable detection devices for explosives.

Cu@Pd/C with Controllable Pd Dispersion as a Highly Efficient Catalyst for Hydrogen Evolution from Ammonia Borane.

A series of Cu@Pd/C with different Pd contents was prepared using the galvanic reduction method to disperse Pd on the surface of Cu nanoparticles on Cu/C. The dispersion of Pd was regulated by the Cu(I) on the surface, which was introduced by pulse oxidation. The Cu2O did not react during the galvanic reduction process and restricted the Pd atoms to a specific area. The pulse oxidation method was demonstrated to be an effective process to control the oxidization degree of Cu on Cu/C and then to govern the dispersion of Pd. The catalysts were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscope (HRTEM), high angular annular dark field scanning TEM (HAADF-STEM), energy-dispersive spectroscopy (EDS) mapping, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), auger electron spectroscopy (AES), and inductively coupled plasma optical emission spectrometer (ICP-OES), which were used to catalyze the hydrogen evolution from ammonia borane. The Cu@Pd/C had much higher activity than the PdCu/C, which was prepared by the impregnation method. The TOF increased as the Cu2O in Cu/C used for the preparation of Cu@Pd/C increased, and the maximum TOF was 465 molH2 min-1 molPd-1 at 298 K on Cu@Pd0.5/C-640 (0.5 wt % of Pd, 640 mL of air was pulsed during the preparation of Cu/C-640). The activity could be maintained in five continuous processes, showing the strong stability of the catalysts.

Author Correction: Chiral recognition and enantiomer excess determination based on emission wavelength change of AIEgen rotor.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Chiral recognition and enantiomer excess determination based on emission wavelength change of AIEgen rotor.

Chiral recognition, such as enantioselective interactions of enzyme with chiral agents, is one of the most important issues in the natural world. But artificial chiral receptors are much less efficient than natural ones. For tackling the chiral recognition and enantiomer excess (ee) analysis, up until now all the fluorescent receptors have been developed based on fluorescence intensity changes. Here we report that the chiral recognition of a large number of chiral carboxylic acids, including chiral agrochemicals 2,4-D, is carried out based on fluorescent colour changes rather than intensity changes of AIEgen rotors. Moreover, the fluorescence wavelength of the AIEgen rotor linearly changes with ee of the carboxylic acid, enabling the ee to be accurately measured with average absolute errors (AAE) of less than 2.8%. Theoretical calculation demonstrates that the wavelength change is ascribed to the rotation of the AIEgen rotor upon interaction with different enantiomers.

Facile Preparation of Pd/UiO-66-v for the Conversion of Furfuryl Alcohol to Tetrahydrofurfuryl Alcohol under Mild Conditions in Water.

The hydrogenation of furan ring in the biomass-derived furans is of great importance for the conversion of biomass to valuable chemicals. Fabrication of high activity and selectivity catalyst for this hydrogenation under mild conditions was one of the focuses of this research. In this manuscript, UiO-66-v, in which vinyl bonded to the benzene ring, was first prepared. Then, the uniformly distributed vinyl was used as the reductant for the preparation of Pd/UiO-66-v. The catalyst was characterized by X-ray diffraction, thermogravimetric, N2 physical adsorption/desorption, X-ray photoelectron spectroscopy, scanning electron microscope, transmission electron microscopy, energy dispersive spectrometer elemental mappings, and inductively coupled plasma atomic emission spectroscopy to find the Pd/UiO-66-v had a narrow palladium nanoparticles size of 3-5 nm and maintained the structure and thermal stability of UiO-66-v. The Pd/UiO-66-v was used for the hydrogenation of furfuryl alcohol to tetrahydrofurfuryl alcohol in water. 99% conversion of furfuryl alcohol was obtained with 90% selectivity to tetrahydrofurfuryl alcohol after reacted at 0.5 MPa H2, 303 K for 12 h. The Pd/UiO-66-v was proved to be effective for the hydrogenation of furan ring in furans and could be used for at least five times.

Monomer emission and aggregate emission of TPE derivatives in the presence of γ-cyclodextrin.

It was found for the first time that neutral amphiphilc tetraphenylethylene (TPE) derivatives showed an enhanced monomer emission and a decreased aggregate emission when they were included in the cavity of γ-cyclodextrin. This result provided a new insight into the aggregation-induced emission (AIE) effect.

Different morphologies of silica synthesized using organic templates from the same class of chiral compounds.

Rarely known round silica tubes with a hollow shell and square silica tubes, in addition to convenient hollow spheres, hollow spheres with a hole, and helical nanoribbons, could be synthesized using organic templates from the same class of organic compounds, arylacrylonitrile tartaric acids. A novel process of dissolving and re-assembling of template aggregates was the reason for forming a variety of morphologies of silica except square silica tubes which were directly controlled by template aggregates. The chirality of the template molecules played a key role in the formation mechanism of silica, in which not only the chirality of the silica nanoribbons but also the silica morphology could be controlled by the chirality of the template molecules.

Highly sensitive determination of enantiomeric composition of chiral acids based on aggregation-induced emission.

A new chiral tetraphenylethylene derivative with the AIE effect was synthesized and showed not only high enantioselectivity for a wide range of chiral acids but also a high sensitivity of 3.0 × 10(-6) M scale. The enantiomeric purity of chiral acids could be quantitatively determined by this chiral sensor.

Light-emitting property of simple AIE compounds in gel, suspension and precipitates, and application to quantitative determination of enantiomer composition.

It was found that simple AIE compounds could emit different intensity of fluorescence in gel, suspension and precipitates for the first time, which could be applied to fluorescence switches and quantitative determination of enantiomer composition.

Effect of carboxylic acid on micelles of a neutral amphiphilic dendro-calix[4]arene.

An amphiphilic calix[4]arene bearing branched 3,4,5-tris(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)benzamide groups at the upper rim was synthesized and could increase the solubility of naproxen and ibuprofen in water through hydrogen bonding and π-π stacking interactions. The interactions between amphiphilic calix[4]arene and carboxylic acids such as naproxen and ibuprofen could reverse the direction of the branched substituents and change the shape and size of calixarene micelles from solid to hollow or linear ones.

Highly enantioselective recognition of a wide range of carboxylic acids based on enantioselectively aggregation-induced emission.

A new chiral fluorescence receptor, designed to exploit aggregation-induced emission (AIE), exhibited not only an exceptionally high enantioselectivity but was also applicable to a wide range of chiral carboxylic acids. The fluorescence intensity ratio of two enantiomers ranged from 10 to 1.6 × 10(4) and could be used to determine the purity of the enantiomers.

Single-hole hollow nanospheres from enantioselective self-assembly of chiral AIE carboxylic acid and amine.

Phenylacrylonitrile tartaric acids have been found to enantioselectively self-assemble with an enantiomer of a chiral amine to form either nanofibers or nanospheres that exhibit aggregation-induced emission (AIE). The nanofibers exhibited stronger emission intensity and longer wavelengths of absorption and emission than the nanospheres because of increased π-π conjugation, an effect previously unseen in AIE. When the solvent consists of a mixture of water and THF rather than water and ethanol, the resultant nanospheres have holes. The holes are the result of the dissolution of defects and a decrease in the bending energy. This is in contrast to hole formation from solvents flowing out of the nanospheres, as previously seen. Through control of the water/THF ratio, the size of the holes in the nanospheres can be tuned. Nanospheres with a single hole displayed both higher uptake capacity and larger release speed of the drug naproxen than closed nanospheres. The ability to adjust fluorescent properties of AIE molecules through the preparation of organic single-hole hollow nanospheres has also been investigated along with the implications of the AIE mechanism.

Enantiomer analysis of chiral carboxylic acids by AIE molecules bearing optically pure aminol groups.

Pure enantiomers of carboxylic acids are a class of important biomolecules, chiral drugs, chiral reagents, etc. Analysis of the enantiomers usually needs expensive instrument or complex chiral receptors. However, to develop simple and reliable methods for the enantiomer analysis of acids is difficult. In this paper, chiral recognition of 2,3-dibenzoyltartaric acid and mandelic acid was first carried out by aggregation-induced emission molecules bearing optically pure aminol group, which was easily synthesized. The chiral recognition is not only seen by naked eyes but also measured by fluorophotometer. The difference of fluorescence intensity between the two enantiomers of the acids aroused by the aggregation-induced emission molecules was up to 598. The chiral recognition could be applied to quantitative analysis of enantiomer content of chiral acids. More chiral AIE amines need to be developed for enantiomer analysis of more carboxylic acids.