Estudo computacional da adsorção de baicaleína em substratos de grafeno e ouro via DFT

Abstract

Flavonoids form an extensive category of secondary metabolites belonging to the polyphenol class, found in various plant species, such as Scutellaria baicalensis Georgi, a herbal medicine that contains the molecule baicalein (BCL), denoted by C 15 H 10 O , as the main bioactive compound used to aid in the treatment of diseases. A broad understanding of the effects of BCL in humans is essential, considering parameters such as appropriate dosage and potential effects associated with overdose. It is therefore necessary to develop and/or improve simple, miniaturized, low-cost and highly sensitive mechanisms for detecting BCL. This master’s thesis describes a theoretical study of the adsorption of baicalein on graphene and gold substrates via Density Functional Theory (DFT). The systems based on different graphene substrates and transition metal surfaces for the adsorption of BCL were: (i) pristine graphene (GRPR); (ii) graphene with monovacancy (GRMV); (iii) oxygen-doped graphene (GRDP); additionally, (iv) Au(111) surface (S1A). Initially, this study was based on the confection of systems in the isolated regime, in which the BCL, graphene and gold substrates were analyzed, followed by convergence tests. The confection of the isolated systems aims to incorporate an adequate surface area to accommodate the BCL in the adsorption process. After defining, optimizing via DFT and characterizing the isolated systems, composed of the adsorbate (BCL) and the substrates, we proceeded with the adsorption of BCL on the substrates via ab initio molecular dynamics (AIMD) simulations. From molecular adsorptions, it was possible to verify the behavior of changes related to the interaction at the atomistic level between molecule and substrate in order to obtain a set of adsorbed systems with greater stability in energetic terms. The values obtained for the adsorption and interaction energies are energetically favorable in relation to the combined systems. When verifying the main interaction behaviours, it should be noted that the type of bond acting on the adsorption of BCL on the GRPR, GRDP and S1A substrates is characterized by physisorption, with BCL interacting in parallel with the substrates. In contrast, the type of bond acting on the adsorption of BCL on the GRMV structure is defined by chemisorption, where the study molecule was adsorbed via chemical bonds. The analysis of BCL interaction and adsorption on the different substrates highlights the relevance of this study in combining structures and establishing detection mechanisms. Ultimately, the investigation of BCL adsorption on GRPR, GRMV, GRDP and S1A substrates contributes to the understanding of the molecular interaction at the atomistic level.