Luminescência de Carbon Dots derivados de Cloreto de Dansil: efeitos térmicos e geração de oxigênio reativo

Abstract

Carbon dots constitute a new class of carbon-based nanomaterials that have been the subject of an increasing number of researches since its discovery in 2004. Presented as an alternative to the use of metallic and inorganic nanostructures, its uorescent properties, biocompatibility and low production cost allow its use in several areas. In the present study, a hydrothermal synthetic method was used to produce carbon dots derived from 5 - (dimethylamino) naphthalene- 1 -sulfonyl (Dansil Chloride) co-doped with Nitrogen and Sulfur. Through morphological characterization, it was possible to identify the core crystalline structure and the functional groups attached to the surface of the nanoparticle. Spectroscopy revealed an excitation-dependent uorescence for wavelengths greater than 400 nm. Investigating the behavior of the emission of the material under temperature change, a thermal dependence was identied, characterized by an increase in the intensity of the emission in response to the increase in temperature; this behavior points to a reverse intersystem crossing between the excited states of the material, promoting a thermally activated uorescence. The absolute thermal sensitivity was determined as 1.04ºC−1 and the absolute sensitivity exhibited an increase from 0.45ºC−1 to 0.55ºC−1 in the temperature range 20oC − 60oC. The possibility of applying this structure as a raciometric thermal sensor was investigated through the continuous thermal variation in heating and cooling cycles. Additionally, the quantum yield of singlet oxygen generation by carbon dots was studied in order to propose its use in techniques such as Photodynamic therapy. The yield was measured with the aid of the 1,3-diphenylisobenzofuran (DPBF), as the oxygen scavenger, and Methylene Blue (MB), as a reference dye, investigating the absorption spectrum of DPBF when in the presence of PCs or MB under continuous laser irradiation at 532 nm.