Elaboração de filmes poliméricos contendo o luminóforo AMPYZCAD para dispositivos emissores de luz

Abstract

The main objective of this dissertation is to investigate the optical and spectroscopic properties of AMPYZCAD (cadmium acetate dihydrate and aminopyrazine), a substance that emits light in the blue region when excited by ultraviolet light. For this, AMPYZCAD was dissolved and mixed with PMMA (polymethyl methacrylate), which is another transparent polymer, with good properties for application in optics, and which has a transmittance greater than 92% in the visible region. The solution preparation process consisted of separately dissolving AMPYZCAD in ethanol and PMMA in acetonitrile. Then, the two solutions were mixed under magnetic stirring and heating at ~100°C. Next, thin films were deposited on flat sodalima glass slides, using the dip-coating technique; and on commercial LEDs (Light Emitting Diodes), using the same technique, with depositions carried out at a temperature of 100°C. The casting technique was also used for the deposition of films in glass beakers, which were then removed from the beakers, becoming independent thick films (bulks), without any substrate as a support – which in this work are called thick films. Optical characterizations of thin films showed that the transmittance with different concentrations of AMPYZCAD (1%; 5%; 10%; 20%; 30% by mass) was not less than 91% in the visible region. The greatest variation in transmittance was verified in the films that presented the highest number of layers, since films with 1; 5; 10; and 20 layers, with concentration of 10% AMPYZCAD, and the transmittance values of the 20 layers were 85%. The microscopy images showed dissolution of AMPYZCAD in the PMMA matrix, also having uniformity in the films. Photoluminescence measurements of the thick films were carried out under excitation at approximately 324 nm, and the emission peak was observed at approximately 397 nm. The collected Raman spectra are similar to the AMPYZCAD and PMMA data found in the literature, showing that the two compounds coexist in the samples. Xray diffraction technique showed the presence of AMPYZCAD crystalline in samples with concentrations above 10%, in less concentrated samples AMPYZCAD crystalline was not detected. The bare LEDs used emit in the ultraviolet regions, and after coating it was possible to verify an increase in emission closer to violet and blue, since AMPYZCAD is excited in the ultraviolet region. It is also possible to perceive a larger emission spectrum in some samples of LEDs, with AMPYZCAD film, thus representing an increase in the efficiency of these devices.