Room temperature phosphorescence of heavy-atom-free indole carboxylic acid/polyacrylamide: Low cost, long lifetime and good luminescent efficiency

Functional organics doped polymers have displayed tunable room temperature phosphorescence (RTP), emerging as promising applications in optical information encryption and organic electronic devices. However, the present doped polymer systems confront a difficulty of constructing a low-cost heavy-atom-free doped systems with ultra-long RTP lifetime and high luminescent efficiency by a facile and environmental-friendly approach, which retards large-scale and commercialized applications. In this work, based on indole derivatives of high quantum efficiency and water-soluble polyacrylamide (PAM) of high H-bond capacity, several kinds of commercialized indole carboxylic acid (ICA), with different extended benzoic acid arms, were respectively combined with PAM based on intermolecular hydrogen bonding by water-promoted dispersion, thereby effectively retarding non-radiative transition. The average RTP lifetimes of 5-ICA/PAM-0.3% and IDCA/PAM-0.3% films could reach 1.997 and 0.992 s respectively at room temperature. Moreover, to adjust the positions of substituted carboxy groups, the luminescent colors can be tuned from blue to yellowish green. Anti-counterfeiting patterns can be facilely fabricated with ICA-doped PAM by environmental-friendly and low-cost screen printing and brush writing, which gives an insight into commercialized production for information security.