Gaobin Zhang

Complex‐Formation‐Enhanced Fluorescence Quenching Effect for Efficient Detection of Picric Acid

Amine-functionalized α-cyanostilbene derivatives (Z)-2-(4-aminophenyl)-3-(4-butoxyphenyl)acrylonitrile (ABA) and (Z)-3-(4-butoxyphenyl)-2-[4-(butylamino)phenyl]acrylonitrile (BBA) were designed for specific recognition of picric acid (PA), an environmental and biological pollutant. The 1:1 host-guest complexes formed between the chemosensors and PA enhanced fluorescence quenching, thus leading to sensitive and selective detection in aqueous media and the solid phase.

Aggregation-induced emission enhancement and mechanofluorochromic properties of α-cyanostilbene functionalized tetraphenyl imidazole derivatives

Three tetraphenyl imidazole derivatives functionalized by an α-cyanostilbene unit (3a–3c) have been designed and synthesized. A combination of the representative aggregation-induced emission enhancement fluorophore and propeller sharp tetraphenyl imidazole unit in the same molecule achieved the integration of their function. 3a–3c emitted weakly in dilute organic solvents and showed an evident solvatochromic effect caused by strong intramolecular charge transfer (ICT), which has been confirmed by density functional theory (DFT) calculations. Meanwhile, in the solid state, they exhibited obvious fluorescence and stimuli-responsive emission. The main emission peak of compound 3a was red-shifted from 519 nm to 550 nm after grinding. The reason could be explained that the destruction of the crystalline structure leads to the planarization of molecular conformation or the increase of conjugation.

Multi-stimuli-responsive fluorescence of a highly emissive difluoroboron complex in both solution and solid states

A highly fluorescent emissive difluoroboron complex (TC) was designed, synthesized and characterized. The absolute fluorescence quantum yields of TC are 33.0% in the solid state and 26.0% in the solution state. The results of X-ray diffraction analysis demonstrate that the rigid structure, the intermolecular hydrogen bonding and the well-ordered as well as loose molecular packing are the major reasons for the high fluorescence emission. Moreover, the colors and fluorescence emission of TC can be switched by external stimuli including grinding and acids/bases. Powder X-ray diffraction (PXRD) investigation verifies that the crystalline–amorphous state transformation between the original and ground states might be attributed to the mechanochromic luminescence properties. The high fluorescence emission and multi-stimuli-responsive fluorescence properties reveal that TC can be used as rewritable information storage, security ink and a fluorescence indicator for acids/bases.

The self-aggregation of fluorophore-triphenylamine nanostructures with tunable luminescent properties: the effect of acidity and rare earth ions

A D–π–A type triphenylamine derivative 3-(4-(diphenylamino)phenyl)acrylic acid (abbreviated as L) is designed, synthesized and characterized by single crystal X-ray diffraction analysis. The self-aggregation of L nanostructures in different acidity aqueous solutions and/or under the guidance of rare earth (RE) ions is studied, along with the corresponding optical properties. In strong acidic conditions, L molecules self-assemble to form two dimensional nanostructures. While in neutral aqueous solutions, L tends to form nanorods. In the strong alkali environment, nanofibers were obtained. Moreover, in acidic conditions, the existence of Tm3+ induces the L molecules to self-aggregate into nanoplates. Flower-like six branched structures are observed when Yb3+ is used. The changed morphology leads to tunable linear optical properties.

High fluorescence of carbazole derivatives for bioimaging of endoplasmic reticulum and lysosome: the influence of molecular structure on optical properties and cell uptake

Three new carbazole derivatives (L1–L3) with different functional groups have been synthesized and characterized. L1 and L2 are connected through methylene unit to construct L3 with enhanced molecular distortion configuration. The compounds exhibit dependent aggregation-induced enhanced emission (AIEE) properties and cellar uptake region in HepG2 cells. It is demonstrated that L1 and L2 exhibit modest AIEE properties in THF–H2O mixtures, while L3 shows superior AIEE character with 13 times enhancement. This is because of the enhanced molecular distortion configuration of L3 and the related restriction of π–π stacking interactions between adjacent L3 molecules resulted from the introduction of methylene unit. Due to the unique structure of the compounds, the superior fluorescence emission of L1–L3 in aqueous media, further imaging studies demonstrated the suitability of probes L1–L3 for the biological applications in both human liver hepatocellular carcinoma cells (HepG2) and plant tissues of Arabidopsis seedlings. The imidazole unit in L2 leads selective target to lysosome of HepG2 cells through acid–base interactions, while L1 and L3 are inclined to act with endoplasmic reticulum.

Anion-controlled dimer distance induced unique solid-state fluorescence of cyano substituted styrene pyridinium

Molecular packing arrangements play a key role in dominating the photophysical properties of luminophores in aggregated state but fine control of the molecular packing is a great challenge. This article describes a unique cyano substituted styrene pyridinium with interesting solid-state fluorescence that can be finely tuned by simple change of counteranions. The dilute solutions of the organic salts (PyCl, PyNO3, PyOTs and PyPh4B) exhibit very weak fluorescence. The crystals of the organic salts (PyCl, PyNO3, and PyOTs) show much enhanced fluorescence compared with their dilute solutions. It is interesting that the emissions changed from bluish-green to deep-blue and fluorescence quantum yields increase from 2.5% to 13.1% with the increasing of steric hindrance of the anions from chloridion, nitrate, to p-toluenesulfonate. Crystal and DFT studies reveal that the enhanced fluorescence is ascribed to the formation of dimers and bigger anions induce larger molecular separation in dimers. Tetraphenylboron anion with very large steric hindrance impedes the formation of dimers and thus results in non-fluorescent salt (PyPh4B). Meanwhile, this unique dimeric packing endows the crystal of PyNO3 with anisotropic fluorescence.