Alcançando fosforescência em condição ambiente para moléculas puramente orgânicas

Abstract

In this study, the photophysical properties of two organic molecules, named KSH 03- 13 and KSH 05-09, were investigated. These molecules consist of two fused heterocyclic aromatic rings. One of the rings is pyridine (an aromatic ring containing a nitrogen atom), and the other is carbazole (a bicyclic aromatic compound containing a nitrogen atom in the central ring). The structures of the molecules are fully conjugated, and they are isomers of each other. The samples were prepared in solutions of Tetrahydrofuran (THF), Dichloromethane (DCM), toluene, and chloroform, and in films of Polymethylmethacrylate (PMMA), Poly(acrylic acid) (PAA), zeonex, Polyvinylidene Fluoride (PVDF), and Poly(methacrylic acid) (PMAA). Optical characterization was conducted using conventional techniques such as optical absorption, photoluminescence, and quantum emission efficiency. Additionally, we employed a more advanced time-resolved technique, such as time-resolved fluorescence, using a system based on time-correlated single-photon counting and an intensified charge-coupled device (iCCD) camera to detect phosphorescent emission. Optical measurements were carried out at different temperatures and with varying excitation laser powers. Based on the experimental results, we demonstrated room-temperature phosphorescence in both organic molecules incorporated into PAA and PMMA matrices. We found that room-temperature phosphorescence (RTP) is based on the rigid environment formed between the polymer matrix and the organic molecule. This environment is constructed through hydrogen bonds that suppress non-radiative energy loss and also partially protect against oxygen quenching of the excited triplet state. In addition to the photophysical characterization, we present naked-eye images of both materials showing room-temperature phosphorescence.