Long-lived emission at room temperature of harmane dispersed in poly (acrylic acid)-poly (vinyl alcohol) polymer network

Harmane (1-methyl-9-H-pyrido-[3,4-b]-indol) was dispersed in poly (acrylic acid)-poly (vinyl alcohol) polymer network (PAA-PVA) from aqueous solution. The equilibrium between monoprotoned and neutral forms of the harmane was monitored using absorption and emission spectra. In PAA-PVA polymer network this equilibrium was shifted towards monoprotoned form due to free carboxy l groups which becomes the network of an abundant proton source. Moreover, the emission decay measurements with harmane into PVA-PAA polymer network i n the dry state showed a non-expected long-lived excited state with maximum emission band at 490 nm and decay time of 2.9 s at room temperature. (C) 1 999 Elsevier Science B.V. All rights reserved.