Dopamine Adsorption on Rutile TiO₂(110): Geometry, Thermodynamics, and Core-Level Shifts from First Principles

Abstract

The modification of the rutile TiO2(110) surface with dopamine represents the best example of the functionalization of TiO2-based nanoparticles with catecholamines, which is of great interest for sunlight harvesting and drug delivery. However, there is little information on the dopamine–TiO2(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 TiO2(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 TiO2(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 TiO2(110) surface.

Composites with Immobilized Bioactive Spirulina on an Inorganic Substrate (Yellow Clay, Hydroxyapatite, SiO2, TiO2, ZnO)

“…According to the literature data, [46][47][48] the 110 face of the rutile surface is the most widespread thermodynamically. Therefore, it was chosen as the main one for adsorption of the Cyanidin 3,5-O-diglucoside molecule on the surface of titanium oxide.…”

Understanding the prototype catalyst TiO2 surface with the help of density functional theory calculation

“…Dopamine is found to adsorb dissociatively on the rutile TiO 2 (110) surface. 277 The deprotonated oxygens bind to Ti 5c , whereas protons move to the low-coordinated oxygens of the substrate. The adsorption process is highly exothermic at À2.90 eV and results in the formation of dopamine enolate species with bidentate coordination at the surface.…”

“…Dopamine is found to adsorb dissociatively on the rutile TiO 2 (110) surface 277 . The deprotonated oxygens bind to Ti 5c , whereas protons move to the low‐coordinated oxygens of the substrate.…”