This work investigated the properties of a four-component molecular ensemble, in which a carbazole (CBz) donor and a benzothiadiazole (BTD) acceptor are connected through a phenylthiophene (PT) bridge. The multiple...

A carbon quantum dot-based chitosan hydrogel was prepared in this work as a fluorescence sensor for the selective sensing of Hg 2+ ions. Among the eight tested metal ions, the prepared hydrogel exhibited remarkable sensing selectivity and sensitivity toward Hg 2+ . The results demonstrated that a prominent fluorescence quenching at 450 nm was observed in the presence of Hg 2+ with a linear response range of 0–100.0 nM and an estimated limit of detection of 9.07 nM. The as-prepared hydrogel demonstrates pH-dependent fluorescence intensity and sensitivity. The highest fluorescence intensity and sensitivity were obtained under pH 5.0. The excellent sensing selectivity could be attributed to a strong interaction between the hydrogel film and Hg 2+ ions to form complexes, which provokes an effective electron transfer for fluorescence quenching. Results from density functional theory (DFT) calculation confirm that the interaction energies (ΔIE) of the hydrogel with three toxic metal ions (Hg 2+ , Cd 2+ , and Pb 2+ ) are in the following order: Hg 2+ > Cd 2+ > Pb 2+ .

Two structural isomers of (9 H -pyreno[4,5- d ]imidazol-10-yl)-benzaldehyde, with para and meta substitution patterns, were synthesized by condensation of 4,5-pyrenedione with terephthalaldehyde and isophthalaldehyde, respectively. These new pyrenoimidazole derivatives were characterized by single-crystal X-ray crystallography, UV–vis absorption spectroscopy, fluorescence spectroscopy, and cyclic voltammetry to elucidate their structural, solid-state packing, and electronic properties. Interactions of these compounds with fluoride anions in polar organic solvents (acetone and dimethyl sulfoxide) were investigated by NMR, UV–vis, and fluorescence techniques in conjunction with density functional theory calculations. UV–vis analysis showed that the binding of the two pyrenoimidazolyl benzaldehydes with fluoride anions resulted in significant colorimetric responses, while fluorescence studies showed that the para -pyrenoimidazolyl benzaldehyde behaved as an intramolecular charge transfer fluorescent probe, exhibiting ratiometric sensing performance to efficiently detect and quantify fluoride anions at the sub-millimolar level.

Pyrene-4,5-dione and pyrene-4,5,9,10-tetraone are K-region oxidized derivatives of pyrene, which show interesting structural and electronic properties as well as useful application in organic electronic and optoelectronic devices. The single-crystal structures of pyrene and pyrene-4,5-dione have been published, but the crystallographic data of pyrene-4,5,9,10-tetraone has not. In this work, the single-crystal structure of pyrene-4,5,9,10-tetraone has been clearly elucidated for the first time, and the detailed crystallographic properties were analyzed and discussed in comparison with those of pyrene and pyrene-4,5-dione. Various noncovalent interactions taking place within the supramolecular assemblies that exist in the crystal packing of these compounds were studied by Hirshfeld surface analysis and density functional theory (DFT) calculations. Our joint experimental and computational analyses provide fundamental understanding of the electron density properties, interaction energies, and frontier molecular orbital (FMO) properties for these pyrene systems and establish correlations of these properties with diverse supramolecular assembling motifs.

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