RESUMO
An aggregation-induced emission (AIE) active Schiff base L was obtained by reacting pyridoxal and 2-hydroxy-1-naphthaldehyde with p-phenylenediamine in two simple steps. The colorimetric, UV/VIS and fluorescence studies of L revealed that the yellow emissive L (λem =540â nm, λex =450â nm) in pure DMSO turned to a red-emissive L, when the poor solvent fraction (HEPES buffer, 10â mM, pHâ 7.4) was increased above 50 % in DMSO. The SEM and DLS results indicated the formation of self-aggregates of L that restricted the intramolecular motion and promoted the excited state intramolecular proton transfer (ESIPT) process. The cations sensing ability of the AIEgen L was explored in HEPES buffer (5 % DMSO, 10â mM, pHâ 7.4), where Cu2+ selectively quenched the fluorescence at 608â nm due to the chelation-enhanced fluorescence quenching (CHEQ) effect with an estimated sensitivity limit of 0.9â µM. Subsequently, the inâ situ formed AIEgen L-Cu2+ complex was applied for the cascade detection of glutathione (GSH), cysteine (Cys) and homocysteine (Hcy). The decomplexation of Cu2+ from the AIEgen L-Cu2+ by GSH, Cys and Hcy restored the quenched fluorescence emission of AIEgen L at 608â nm. With this Cu2+ displacement approach, the concentration of Cys, Hcy and GSH can be detected down to 2.8â µM, 3.12â µM and 2.0â µM, respectively. The practical utility of AIEgen L and AIEgen L-Cu2+ was examined by monitoring the selective analytes in real environmental and biological samples, and also applied successfully for the cell imaging applications.