Resumo:
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.
