Oxygen-consumption-induced phosphorescence enhancement: both energy- and charge-involved mechanisms

Abstract

Oxygen consumption-induced room-temperature phosphorescence (RTP) enhancement phenomenon has been reported, but its underlying luminescence mechanism still remains less clear. It is generally accepted that the phosphorescence enhancement is primarily attributed to the conversion of triplet oxygen by triplet excitons to singlet oxygen during photo illumination. Herein, we have developed RTP materials by doping methyl indole-6-carboxylate and indole-6-carboxylic acid into polyvinyl alcohol (PVA) matrix. The as-prepared film materials emit blue phosphorescence with apparent oxygen-dependent phosphorescence enhancement phenomenon. In the methyl indole-6-carboxylate doping system, under continuous UV irradiation for 60 s, the doped film exhibited a phosphorescence afterglow of more than 12 s with a phosphorescence lifetime of 1.46 s. We propose two complementary oxygen-consumption mechanisms to enhance RTP, involving energy- (triplet quenching of the indole-based luminogens) and charge-related (singlet quenching) processes. By utilizing the phosphorescence enhancement property, the potential applications of the doped films in write-read-erase information storage and anti-counterfeiting have been demonstrated.