Síntese e caracterização de pontos quânticos de carbono a partir da pirólise da palha de milho e oxidação dos produtos

Abstract

This study aims to produce carbon dots (CDs) from corn husks using pyrolysis as the synthesis method. The corn husks were subjected to a temperature of 300 °C in a muffle furnace, with 3 mL of nitric acid (HNO₃) used as the oxidizing agent. Temperature and exposure time were key variables in the formation of CDs. Six samples were prepared with treatment durations of 1, 2, and 3 hours to analyze structural and optical changes. Characterization by Fourier-transform infrared spectroscopy (FTIR) indicated the presence of nitrogen-containing functional groups, confirming the carbonization of the material. Ultraviolet-visible (UV-Vis) absorption spectra showed bands between 270 and 340 nm related to π-π* transitions of C=C bonds in the graphitic structure, and a band around 350 nm associated with n-π* transitions of carbonyl (C=O) groups. Additionally, luminescence emission was observed when the samples were excited at specific wavelengths, with varying emission intensities—ranging from low 69 (u.a) to high 318 (u.a) depending on particle size and quantum confinement effects, which influence the optical behavior of the CDs.