| Autor: |
Cadmen N; Departamento de Química, Universidad Técnica Particular de Loja, San Cayetano Alto, Loja 1101608, Ecuador., Bustamante J; Departamento de Química, Universidad Técnica Particular de Loja, San Cayetano Alto, Loja 1101608, Ecuador., Rivera R; Departamento de Química, Universidad Técnica Particular de Loja, San Cayetano Alto, Loja 1101608, Ecuador., Torres FJ; Grupo de Química Computacional y Teórica (QCT-UR), Facultad de Ciencias Naturales, Universidad del Rosario, Bogotá 111221, Colombia.; Grupo de Química Computacional y Teórica (QCT-USFQ), Departamento de Ingeniería Química, Universidad San Francisco de Quito (USFQ), Quito 170901, Ecuador., Ontaneda J; Departamento de Química, Universidad Técnica Particular de Loja, San Cayetano Alto, Loja 1101608, Ecuador. |
| Abstrakt: |
The modification of the rutile TiO 2 (110) surface with dopamine represents the best example of the functionalization of TiO 2 -based nanoparticles with catecholamines, which is of great interest for sunlight harvesting and drug delivery. However, there is little information on the dopamine-TiO 2 (110) adsorption complex in terms of thermodynamic properties and structural parameters such as bond coordination and orientation of the terminal ethyl-amino group. Here, we report a density functional theory (DFT) investigation of dopamine adsorption on the TiO 2 (110) surface using the optB86b-vdW functional with a Hubbard-type correction to the Ti 3d orbitals, where U eff = 3 eV. Guided by available X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) data, our simulations identify enolate species with bidentate coordination at a submonolayer coverage, which are bonded to two neighboring 5-fold-coordinated Ti atoms at the TiO 2 (110) surface through both deprotonated oxygen atoms of the dopamine, i.e., in a bridging fashion. The process is highly exothermic, involving an adsorption energy of -2.90 eV. Calculated structural parameters suggest that the molecule sits approximately upright on the surface with the amino group interacting with the π-like orbitals of the aromatic ring, leading to a gauche-like configuration. The resulting NH···π hydrogen bond in this configuration can be broken by overcoming an energy barrier of 0.22 eV; in this way, the amino group rotation leads to an anti-like conformation, making this terminal group able to bind to other biomolecules. This mechanism is endothermic by 0.07 eV. Comparison of existing spectroscopic data with DFT modeling shows that our computational setup can reproduce most experimentally determined parameters such as tilt angles from NEXAFS and chemical shifts in XPS, which allows us to identify the preferred mode of adsorption of dopamine on the TiO 2 (110) surface.
Competing Interests: The authors declare no competing financial interest.
(© 2022 The Authors. Published by American Chemical Society.) |
