Organic luminescent materials that can simultaneously achieve multimode mechanochromism and its water-vapor-induced recovery are desirable for practical applications but rarely reported. Herein, an amphiphilic compound, 4-(9H-carbazol-9-yl)-1-(2-hydroxyethyl)pyridin-1-ium bromide (CPAB), is designed by integrating a lipophilic aromatic unit and hydrophilic end in the molecular architecture. Self-recovered mechanochromism from brown to cyan is observed upon mechanical grinding in air. Comprehensive research by X-ray diffraction, infrared spectroscopy, and single-crystal analysis reveals that the photoluminescence switch originates from the variation in intermolecular hydrogen bonds and molecular packing mode. The amphiphilic nature of CPAB allows water molecules to enter the crystalline lattice, forming two polymorphs of the crystalline phase, namely CPAB-D and CPAB-W. The hydrosoluble CPAB exhibits excellent capability in probing the level 3 details of fingerprints because its lipophilic part can target the fatty acid residues of fingerprints, leading to strong aggregation-induced fluorescence. The research may inspire the design of latent fingerprint developers and application in forensics/anti-counterfeiting.

中文翻译：

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多刺激响应两亲性吡啶盐及其在潜在指纹 3 级细节可视化中的应用

可以同时实现多模机械致色及其水蒸气诱导恢复的有机发光材料在实际应用中是可取的，但很少有报道。在此，一种两亲性化合物 4-(9H-carbazol-9-yl)-1-(2-hydroxyethyl)pyridin-1-ium bromide (CPAB) 是通过在分子结构中整合亲脂性芳香单元和亲水端而设计的. 在空气中机械研磨时观察到从棕色到青色的自恢复机械变色。通过 X 射线衍射、红外光谱和单晶分析的综合研究表明，光致发光开关源于分子间氢键和分子堆积模式的变化。CPAB的两亲性允许水分子进入晶格，形成晶相的两种多晶型物，即 CPAB-D 和 CPAB-W。水溶性 CPAB 在探测指纹 3 级细节方面表现出优异的能力，因为它的亲脂性部分可以靶向指纹的脂肪酸残基，从而导致强烈的聚集诱导荧光。该研究可能会启发潜在指纹显影剂的设计和在取证/防伪中的应用。