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Herein, α-cyanostilbene-based luminogen with an electron donor-π-electron acceptor (D-π-A) architecture was formylated into the salicylaldehyde-analogue luminogen, followed by the Schiff base reaction with phenylamine, a red-emitting luminogen was elaborately designed and successfully synthesized in a high yield of 89%. Its well-defined structure was confirmed by FT-IR, MALDI-TOF-MS, HR-MS and 1H/13C NMR technologies. Based on the synergistic mechanisms of aggregation-induced emission (AIE), excited-state intramolecular proton transfer (ESIPT) and intramolecular charge transfer (ICT), it enjoyed a red-fluorescence emission at 627 nm in THF/water mixtures (fw = 95%) and was used as a probe. Moreover, the TLC-based test strips loaded with the probe not only exhibited the reversible fluorescence response to amine/acid vapor but also showed sensitive and selective fluorescence response towards Cu2+. Furthermore, the fluorescence titration experiment between the probe and Cu2+ in THF/water mixtures (fw = 95%, pH = 7.4) revealed that the detection limit was 1.18 × 10-7 M and the binding constant was 1.59 × 105. Job's plot experiment and HR-MS analysis revealed the 2:1 binding stoichiometry of the probe with Cu2+. The method enabled real-time assessment for Cu2+ in real water samples. This study could offer insightful opinions on the development of long-wavelength emissive luminogens based on α-cyanostilbene. [ABSTRACT FROM AUTHOR]

Relying on the synchronic function of aggregation-induced emission (AIE) and excited-state intramolecular proton transfer (ESIPT) mechanisms, a novel fluorophore could emit red-fluorescence with a large Stokes' shift in aggregation state and be used as a sensor for highly selective and sensitive detection of Cu2+ in THF/water system (f w = 90%, pH = 7.4). [Display omitted] • A α-cyanostilbene-based sensor was synthesized by Schiff base reaction. • It could emit red-fluorescence with a large Stokes' shift of ca. 285 nm in solution and aggregation states. • It exhibited prominent "AIE + ESIPT" features in aggregation and solid states. • It possessed a specific sensing ability towards Cu2+ in aggregation and solid states. Through Schiff base reaction of the salicylaldehyde-like α-cyanostilbene derivative with benzophenone hydrazone, a novel fluorophore has been successfully obtained in high yield of 89% and fully characterized by standard spectroscopic techniques. Depending upon the synchronic function of aggregation-induced emission (AIE) and excited-state intramolecular proton transfer (ESIPT) mechanisms, this fluorophore emitted the fascinating red-fluorescence at 602 nm with a large Stokes' shift of 287 nm in aggregation state. This fluorophore as a sensor showed the highly selective and sensitive chelating ability towards Cu2+ in THF/water system (f w = 90%, pH = 7.4), which was confirmed by a prominent attenuation of red-fluorescence at 602 nm with the limit of detection (LOD) of 2.34 × 10-8 M due to the complexation of the sensor and Cu2+ with 2: 1 binding stoichiometry. The proposed recognition mechanism was supported by SEM images, HR-MS analysis, FT-IR and 1H NMR spectra. For applications, this sensor was successfully utilized to determine Cu2+ in environmental water samples. The silica gel test strip impregnated with this fluorophore was also employed for the on-site monitoring of Cu2+ under UV 365nm illumination, indicating its potential utility for visual detection of Cu2+ in solid state. Hence, this work provided a feasible strategy to construct long-wavelength intense fluorescence sensor for effective measurement of Cu2+ level in aggregation state as well as visual detection of Cu2+ in solid state. [ABSTRACT FROM AUTHOR]