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A novel pyrazine hydrazone 1 has been designed and synthesized, which acts as a multiprobe for selective detection of Al3+, Mg2+, and Zn2+ in DMSO solution based on fluorescent enhancement with three different emission colors. The higher affinity of 1 toward Al3+ and Zn2+ compared with Mg2+ facilitates the establishment of a simple ratiometric fluorescent method for the detection of Al3+ and Zn2+ based on the 1 + Mg2+ system. Conversely, probe 1 selectively recognized Al3+ in DMSO-H2O cosolvent with a turn-on response, and the resultant 1 + Al3+ complex could determine F− via a fluorescence quenching signal. In addition, the probe is applied for imaging of Al3+ and F− in living cells.

A series of β-β directly linked Bodipy oligomers (D1, D2, D3 and T1) based on different monomers are synthesized and the crystal structures, photophysical properties, singlet oxygen (1O2) generation abilities, bioimaging and phototoxicity are investigated. Single-crystal X-ray analyses of D1 and D2 indicate the distorted orthogonal conformation of two linked Bodipy planes. In comparison with the meso-β analogues, the β-β dimers exhibit red-shifted spectroscopy bands, strong fluorescent emission but modest 1O2 quantum yields due to the distorted orthogonal structures and electron interaction, which is demonstrated by single-crystal analysis, spectroscopy measurements and quantum calculations. The fluorescence imaging and cytotoxicity assay results indicate that the unsubstituted D1 and D2 with excellent bioimaging performance alongside with obvious phototoxicity are promising candidates in the fields of cell imaging and photodynamic therapy.

A simple monocarbazone 1 derived from 2H-benzo[h]chromene-3-carbaldehyde and carbazide exhibited aggregation-induced ratiometric emission upon the addition of water to CH3OH solution (Δλem= 30 nm). Upon Cu2+ treatment, the fluorescence emission of 1 displayed a significant red shift in both CH3OH and H2O solutions. In addition, 1 can detect Hg2+ through the fluorescence quenching in H2O solution. The response mechanism to Cu2+ involved an intermolecular charge transfer coupled with a metal-induced assembly, whereas that to Hg2+ was probably due to a photo-induced electron transfer coupled with metal-induced assembly, which were thoroughly investigated by spectral methods and theoretical calculation. In addition, the sensor could successfully detect the corresponding ions in HeLa cells.

The interaction of Ligupurpuroside A with bovine serum albumin (BSA) has been investigated by fluorescence spectra, UV–vis absorption spectra, three-dimensional (3D) fluorescence spectra, synchronous fluorescence spectra and circular dichroism (CD) spectra along with a molecular docking method. The fluorescence experiments indicate that Ligupurpuroside A can quench the intrinsic fluorescence of BSA through a combined quenching way at the low concentration of Ligupurpuroside A, and a static quenching procedure at the high concentration. The thermodynamic analysis suggests that hydrogen bonds and van der Waals forces are the main forces between BSA and Ligupurpuroside A. According to the theory of Forster׳s non-radiation energy transfer, the binding distance between BSA and Ligupurpuroside A was calculated to be 2.73 nm, which implies that energy transfer occurs between BSA and Ligupurpuroside A. All these experimental results have been validated by the protein–ligand docking studies which show that Ligupurpuroside A binds to the residues located in the hydrophobic cavity on subdomain IIA of BSA. In addition, conformation change of BSA was observed from three-dimensional fluorescence spectra, synchronous fluorescence spectra and circular dichroism spectra under experimental conditions.

The emission spectra and decay processes of YGG:Cr at temperature range from 10 K to 300 K are studied. There are two fluorescence centres in YGG:Cr with higher impurity concentrations. Energy transfer between different centres is also observed.