Abstract
Some materials, in the presence of specific radiations, have the interesting ability to convert them into emitted photons, this phenomenon is called luminescence. Lanthanide ions exhibit luminescence due to the f-f transitions, what normally result in narrow emission bands that varies from the ultraviolet down to the infrared, giving them the capability to be exploit in a variety of applications, especially those for emission in the visible and infrared. Yet, the Ln3+ ions have an issue concerning the low molar absorptivity, explained by the Laporte´s and spin selection rules. To overcome this problem, high absorbing organic molecules are coordinated to the lanthanide ion, in especial, molecules containing oxygen and nitrogen atoms. In order to have high luminescence intensity, it is necessary high energy transference rates between the ligand and the central ion, what is called "antenna effect". The efficiency of this energy transfer is strongly dependent on the energy of the exited state of the lanthanide ion, and the triplet energy of the ligand, which can be modulated by changes in the molecular structure. Some classical classes of organic molecules used as ligands are the ²-diketones, carboxylic acids, porphyrins, cryptates, and the Schiff bases, which will be investigated in this work. Schiff bases are synthesized very easily and form stable coordination compounds. In this work, we will investigate the influence of the molecular structure of a series of Schiff bases, obtained via the condensation of salycilaldehyde and primary amines, with their triplet level energy, and how it will influence the europium quantum emission efficiency. Such compounds can be applied in several areas like OLED fabrication, aiming low energy consumption Light Converting Devices, and luminescent probes for biological imaging and detection of diseases. (AU)
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