Coumarin based yellow emissive AIEE active probe: A colorimetric sensor for Cu and fluorescent sensor for picric acid.

A hydrazine derived ESIPT active Schiff base, 1-(8-methanylylidene-7-hydroxy-4-methyl-2H-chromen-2-one)-2-(2, 4-dihydroxybenzylidene) hydrazine, L was synthesized and characterized by elemental analysis and by various spectroscopic techniques. L exhibited a colourimetric response towards Cu ion by changing from colorless to yellow with relatively a little or no interference of other common metal ions. The probe also showed good response for the detection of Cu in real water samples. The H-aggregated L displayed AIEE property in acetonitrile/water mixture. The restriction of molecular motions endued the luminogen with a yellow fluorescence through ESIPT emission at 562 nm having relatively large Stock's shift of 205 nm. The scanning electron microscopic study was carried out to investigate the morphology of the nanoaggregate. The aggregated luminogen displayed it yellow emission in the pH range of 4-7 without affecting the intensity. The applicability of the probe for the detection of picric acid was also checked.