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Zhao E.,Hong Kong University of Science and Technology | Hong Y.,Institute for Advanced Study and Institute of Molecular Functional Materials | Chen S.,Hong Kong University of Science and Technology | Leung C.W.T.,Institute for Advanced Study and Institute of Molecular Functional Materials | And 7 more authors.
Advanced Healthcare Materials | Year: 2014

Long-term tracking of bacterial viability is of great importance for monitoring the viability change of bacteria under storage, evaluating disinfection efficiency, as well as for studying the pharmacokinetic and pharmacodynamic properties of antibacterials. Most of the conventional viability dyes, however, suffer from high toxicity and/or poor photostability, making them unsuitable for long-term studies. In this work, an aggregation-induced emission molecule, TPE-2BA, which can differentiate dead and living bacteria and serve as a highly fluorescent and photostable probe for long-term viability assay. TPE-2BA is a cell-impermeable DNA stain that binds to the groove of double-stranded DNA. Bacteria with compromised membrane open the access for TPE-2BA to reach DNA, endowing it with strong emission. The feasibility of using TPE-2BA for screening effective bactericides is also demonstrated. Plate count experiment reveals that TPE-2BA poses negligible toxicity to bacteria, indicating that it is an excellent probe for long-term bacterial viability assay. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chen B.,Hangzhou Normal University | Jiang Y.,Hong Kong University of Science and Technology | Chen L.,South China University of Technology | Nie H.,South China University of Technology | And 10 more authors.
Chemistry - A European Journal | Year: 2014

2,3,4,5-Tetraarylsiloles are a class of important luminogenic materials with efficient solid-state emission and excellent electron-transport capacity. However, those exhibiting outstanding electroluminescence properties are still rare. In this work, bulky 9,9-dimethylfluorenyl, 9,9-diphenylfluorenyl, and 9,9-spirobifluorenyl substituents were introduced into the 2,5-positions of silole rings. The resulting 2,5-difluorenyl-substituted siloles are thermally stable and have low-lying LUMO energy levels. Crystallographic analysis revealed that intramolecular π-π interactions are prone to form between 9,9-spirobifluorene units and phenyl rings at the 3,4-positions of the silole ring. In the solution state, these new siloles show weak blue and green emission bands, arising from the fluorenyl groups and silole rings with a certain extension of π conjugation, respectively. With increasing substituent volume, intramolecular rotation is decreased, and thus the emissions of the present siloles gradually improved and they showed higher fluorescence quantum yields (ΦF=2.5-5.4 %) than 2,3,4,5-tetraphenylsiloles. They are highly emissive in solid films, with dominant green to yellow emissions and good solid-state ΦF values (75-88 %). Efficient organic light-emitting diodes were fabricated by adopting them as host emitters and gave high luminance, current efficiency, and power efficiency of up to 44 100cd m -2, 18.3cd A-1, and 15.7lm W-1, respectively. Notably, a maximum external quantum efficiency of 5.5 % was achieved in an optimized device. © 2014 Wiley-VCH Verlag GmbH& Co. KGaA, Weinheim.

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