Abstract
The non-fluorescent Schiff base compound C1 (N'-((4′-ethyl-3-hydroxy-[1,1′-biphenyl]-4-yl)methylene)furan-2-carbohydrazide) in organic solvent (e.g., THF) was found to produce yellow-green fluorescence emission upon addition of H2O, and granular-shaped aggregates in a THF/H2O mixed solution formed and exhibited obvious aggregation-induced emission (AIE). Especially its keto fluorescence band intensified dramatically, while the enol emission band remained almost unchanged. Hence, a change in fluorescence from no emission of light to emission of bright yellow-green light under a UV lamp was observed with the naked eye. In contrast, the reference compound C2 (N'-((4′-ethyl-3-methoxy-[1,1′-biphenyl]-4-yl)methylene)furan-2-carbohydrazide) showed no intensified fluorescence emission under the same experimental conditions. These results indicated the significant role played by intramolecular H-bonding in the formation of the C1 aggregates and the AIE process.
Highlights
There has been considerable interest recently in uorescent materials because of their various applications in organic lightemitting diodes (OLEDs), uorescence-based sensors, and biological cell imaging
A great deal of effort has been put into studying the optical properties of molecules displaying excited-state intramolecular proton transfer (ESIPT) with aggregation-induced emission (AIE).[12,13,14]
An X-ray diffraction (XRD) pattern of powder C1 displayed intense diffraction peaks, while the reference C2 yielded no obvious diffraction peaks (Fig. S1, Electronic supplementary information (ESI)†); these results suggested the formation of a crystalline state and a harmonious arrangement by C1 molecules in the solid state
Summary
There has been considerable interest recently in uorescent materials because of their various applications in organic lightemitting diodes (OLEDs), uorescence-based sensors, and biological cell imaging. Dyes with aggregation-induced emission (AIE) properties have attracted intense research interest as a novel class of optical materials due to their molecular structures being much easier to modify and tune than the structures of CDs.[6,7] AIE dyes are rotor-type molecules that have been reported to present weak uorescence in pure organic solutions but strong uorescence in the aggregated state.[8,9] These observations have been attributed to the free motion of the rotor aCollege of Materials and Chemical Engineering, Chongqing University of Arts and Sciences, Chongqing, China, 402160.
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