Cyclodextrin-based nano-carrier for intelligent delivery of dopamine in a self-healable anti-corrosion coating

Abstract

In the present work, the dopamine (DOP) performance was improved by encapsulation into a novel amphiphilic beta-cyclodextrin (β-CD) nano-carrier. The inclusion complexes (β-CD-DOP) structure was identified by Ultraviolet-visible spectroscopy (UV-Vis), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction analysis (XRD), Raman, and thermal gravimetric analysis (TGA) techniques. TGA assessments confirmed about 33% of DOP encapsulation in the β-CD cavity. The Electrochemical impedance spectroscopy (EIS) measurements in the solution (NaCl) phase after introducing β-CD-DOP have demonstrated 85% of corrosion attack retardation after 5 h iron exposure to 3.5% NaCl electrolyte. The samples were then analyzed via different morphological/elemental approaches, i.e., Field-Emission Scanning Electron Microscopy (FE-SEM), contact angle, Grazing incidence X-Ray diffraction (GIXRD), and Energy-dispersive X-ray spectroscopy (EDS)/Mapping. The self-healing mechanism after introducing β-CD-DOP into the SiC was investigated by EIS. Results confirmed the film resistance enhancement from 5540 Ω.cm2 to 10,900 Ω.cm2 after 1 h steel exposure, affirming a considerable self-healing degree after β-CD-DOP inclusion. The silane-based coating (SiC) defected zone morphology was studied by EDS/Mapping and FE-SEM techniques. Besides, notable resistance enhancement of the intact SiC has (from 13,032 Ω.cm2 to 16,231 Ω.cm2) demonstrated that most of the coating diffusion pathways were blocked by inclusion complexes, which could reduce the electrolyte/ion diffusion. Through Dispersion-corrected density functional theory (DFT-D) based explorations, the inclusion capacity of DOP inside the β-CD was investigated. The adsorption of DOP and β-CD/DOP on the steel substrate was proved by MC/MD calculations.