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Due to their broad applications in information technology, biochemical sensors, and optoelectronic devices, stimuli-responsive fluorescent materials (SRFMs) have gained significant attention. With their simple synthesis and modification, Schiff bases are considered promising candidates for SRFMs. However, realizing highly efficient luminescence with aggregation-induced emission (AIE) properties as well as stimuli responses is still challenging due to the lack of clear structure–property relationships. In this work, a general strategy for constructing efficient and red-emissive salicylaldehyde Schiff bases is proposed utilizing the triphenylamine (TPA) substitution strategy. Experimental results and theoretical calculations illustrate that all four isomers show a typical AIE effect of the keto-form emission upon photoexcitation and red fluorescence due to the charge-transfer transition from TPA on the salicylaldehyde unit to the keto unit. The single-crystal structure also demonstrates that the introduction of dual TPA leads to appropriate intermolecular interactions, resulting in high-intensity fluorescence. Moreover, with excellent acidochromic properties under both daylight and UV light conditions, p,p-2TPA is successfully applied in steganography and multi-scenario information decryption. This work not only realizes efficient and red-colored luminescence from a simple salicylaldehyde Schiff base skeleton but also provides a strategy for constructing SRFMs with AIE properties. [ABSTRACT FROM AUTHOR]

In the process of structural modal parameters identification under environmental excitation, the employed measured dynamic response signal is usually non-stationary and contains noise. As a novel signal analyzed method, symplectic geometry mode decomposition (SGMD) has been proven to be effective for dealing with non-stationary and noisy signals. However, the traditional SGMD may treat noise as modal information, which inevitably undermines the accuracy of modal identification. To overcome this problem, this paper proposes an optimized SGMD algorithm for structural modal parameter identification. First, the SGMD algorithm is refined with the Hankel matrix, Kurtosis theory, Pearson correlation coefficient, and energy entropy theory. Then, the natural frequencies and damping ratios are identified using the proposed method, which consists of the optimized SGMD algorithm, natural excitation technique (NExT), direct interpolating method, and curve-fitting function. Finally, the applicability of the proposed method under environmental excitation is investigated by two examples: a two-story frame structure and an 88-story office tower. The results demonstrate that the proposed method is effective for identifying the civil structural modal parameters from non-stationary dynamic responses. [ABSTRACT FROM AUTHOR]

Artificial aggregation‐induced emission luminogens (AIEgens) have flourished in bio‐applications with the development of synthetic chemistry, which however are plagued by issues like singularity in structures and non‐renewability. The unique structures and renewability of biomass moieties can compensate for these drawbacks, but their properties are hard to design and regulate due to their confined structures. Therefore, it appears to be a reasonable approach to derive AIEgens from abundant biomass (BioAIEgens), integrating the bilateral advantages of both synthetic and natural AIEgens. In this work, the blue‐violet emissive coumarin with its lactone structure serving as a rare natural acceptor, is utilized to construct donor‐π‐acceptor typed BioAIE isomers incorporating the propeller‐like and electron‐donating triphenylamine (TPA) unit. The results show that Cm‐p‐TPA undergoes charge transfer with its keto form, emitting red light at 600 nm, which can be applied to monitor Cu2+ concentration during mitophagy using fluorescence lifetime imaging microscopy because of the excellent biocompatibility, photostability, and specific recognition to Cu2+. This work not only demonstrates the feasibility of utilizing positional isomerization to modulate excited‐state evolutions and resultant optical properties, but also provides evidence for the rationality of constructing biologically‐active BioAIEgens via a biomass‐derivatization concept. [ABSTRACT FROM AUTHOR]

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Artificial aggregation-induced emission luminogens (AIEgens) have flourished in bio-applications with the development of synthetic chemistry, which however are plagued by issues like singularity in structures and non-renewability. The unique structures and renewability of biomass moieties can compensate for these drawbacks, but their properties are hard to design and regulate due to their confined structures. Therefore, it appears to be a reasonable approach to derive AIEgens from abundant biomass (BioAIEgens), integrating the bilateral advantages of both synthetic and natural AIEgens. In this work, the blue-violet emissive coumarin with its lactone structure serving as a rare natural acceptor, is utilized to construct donor-π-acceptor typed BioAIE isomers incorporating the propeller-like and electron-donating triphenylamine (TPA) unit. The results show that Cm-p-TPA undergoes charge transfer with its keto form, emitting red light at 600 nm, which can be applied to monitor Cu 2+ concentration during mitophagy using fluorescence lifetime imaging microscopy because of the excellent biocompatibility, photostability, and specific recognition to Cu 2+ . This work not only demonstrates the feasibility of utilizing positional isomerization to modulate excited-state evolutions and resultant optical properties, but also provides evidence for the rationality of constructing biologically-active BioAIEgens via a biomass-derivatization concept., (© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.)

Stimuli-responsive aggregation-induced emission (AIE) materials are highly sensitive and rapidly responsive to external signals, making them ideal solid materials for anti-counterfeiting encryption. However, the limited conformational and packing variations resulting from regio-isomerization with a single substituent restricts the stimuli-responsive behavior of these materials. In this work, several AIE-active regio-structural isomers based on the salicylaldehyde Schiff base scaffold have been straightforwardly obtained through multiple substitutions with bromide and triphenylamine moieties. Solvent-effect experiments demonstrate their different orders of charge-transfer and excited-state intramolecular proton transfer upon photoexcitation, indicating the regulation of excited-state processes via multi-site isomerization. These isomers also demonstrate mechanochromism and acidichromism, allowing for adjustable stimuli-responsive effects. As a demonstration, p -Br-TPA with both mechanochromism and acidichromism can be synergistically utilized for multi-level decryption. This study successfully regulates the evolution of excited states through multi-site isomerization, offering a general approach for achieving tunable stimuli-responsive properties in AIE-active salicylaldehyde Schiff bases toward multi-level decryption., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)