Estudo teórico de nanotubos de carbeto de silício (SiC) como material promissor para formação de espécies reativas de oxigênio para combate ao SARS-COV-2

Abstract

Silicon Carbide Nanotubes (SiCNT) are the main focus of this work. The models were generated using algorithms written in shell bash and AWK programming languages. For model optimization, semi-empirical calculations were performed with the MOPAC 2016 package for HF and DFT, calculations were performed using B3LYP (Becke Three Parameter Hybrid Functionals, Lee-Yang-Parr), CAMB3LYP (Counterpoise Corrected for Adsorption Mode - Becke Three Parameter Hybrid Functionals, Lee- Yang-Parr) and B3PW91 (Becke 3-parameter Perdew-Wang 91) hybrid functionals and 3-21G, 6-21G, 6-31G and 6-311G basis. The band gap of the optimized structure was determined by the |HOMO - LUMO| difference, with the intention of determining the conductivity of the nanotube model and comparing it with experimental values. Structural optimization descriptors such as bond distance, diameter and length of the model were determined, in addition to quantum molecular descriptors such as global hardness, electronegativity, electrophilicity index, chemical softness and chemical potential. The dynamics of the interactions of SiCNT with H2O and 3O2 molecules were studied in this work and the calculations of the fractional electron transfer, the individual energy shifts of the donor and acceptor were calculated. The optimized SiCNT model was of the zig-zag type with formula Si48C48H16, tube diameter of 8.3 Å, length of 16.71 Å, Si - C bond length of 1.72 Å, the band gap determined by the HF method based on 6-311G presented a value of 2.67 eV and influenced the choice of the HF method, due to its proximity to the experimental value studied. The values of the molecular descriptors found were electron affinity of 1.96 eV, ionization energy of 4.37 eV, chemical potential of -3.165 eV, electronegativity of 3.165 eV, global hardness of 1.205 eV, electrophilicity index of 4.156 eV and softness of 0.830 eV. The analysis of these molecular description parameters indicated favorable characteristics for the structure to interact with water and oxygen molecules and generate functionalized species. The interaction between the H2O molecule model and the 3O2 molecule produced the SiCNT-OH-H, SiCNT-O2, SiCNT-O2H-OH radicals with favorable energy variations. Subsequently, molecular docking was calculated between the radical models and the SARS-CoV-2 Spike protein, presenting values of energy and affinity variations that make the proposed study valid.