Preparação de pontos de carbono via irriadiação em micro-ondas doméstico: estudos das propriedades estruturais e fotofísicas.

Abstract

Carbon dots (PCs) are nanoparticles produced from carbon sources and have attracted great attention in recent years due to their photoluminescence properties, as well as biocompatibility, low cost in the synthetic route, and photostability. Currently, some studies are being developed with the objective of better understanding the structural and optical properties, since there are numerous methodologies for obtaining PCs, which directly influence the aforementioned properties. Therefore, in our work, we sought to evaluate the structural and optical properties using carbonaceous precursors such as o-phenylenediamine (OPDA) to obtain PCs-OPDA and 3,4-diaminobenzoic acid (3,4-DABA) to obtain PCs 3,4-DABA, in which they were submitted to the same synthetic route condition via irradiation in domestic microwaves. The PCs-OPDA and PCs 3,4-DABA were initially characterized in terms of their structural properties by spectroscopy in the Infrared (IR) region, inferring that the functional groups present on the surfaces of the synthesized PCs are different, Raman spectroscopy made it possible to discuss information on the graphitization of the carbon core of PCs, in which the results obtained showed incomplete carbon core, by powder X-ray diffraction (XRD) and thermogravimetric analysis (TGA), a character of polycrystalline PCs was obtained, indicating that the PCs in our work presented structures referring to the carbonized polymer dots (CPDs), in the atomic force microscopy (AFM) the sizes of the nanoparticles were in the order of 5.02 ± 1.03 nm for PCs-OPDA and 14.01 ± 1.21 nm for PCs 3,4-DABA. The optical properties were studied using ultra and visible violet (UV/Vis) spectroscopy and fluorescence spectroscopy, confirming the formation of CPDs, since the fluorescence emission presented a profile independent of the excitation wavelength for both the PCs. The emission is in the region of yellow for PCs-OPDA and green for PCs 3,4-DABA. Other studies on fluorescence emission were carried out, such as evaluation of fluorescence intensity as a function of pH, evaluation of the fluorescence region in solvatochromism, evaluation of fluorescence intensity about temperature, the quantum yield of fluorescence for PCs-OPDA was 17% and for PCs 3,4-DABA of 2.98% and the cell viability studies of the synthesized PCs showed cytotoxicity for B16F10 and A375 tumor lines in the study concentration range.