title: Electrochemical fabrication of surface chemical gradients in thiol self-assembled monolayers with tailored work-functions.
abstract: The studies on surface chemical gradients are constantly gaining interest both for fundamental studies and for technological implications in materials science, nanofluidics, dewetting, and biological systems. Here we report on a new approach that is very simple and very efficient, to fabricate surface chemical gradients of alkanethiols, which combines electrochemical desorption/partial readsorption, with the withdrawal of the surface from the solution. The gradient is then stabilized by adding a complementary thiol terminated with a hydroxyl group with a chain length comparable to desorbed thiols. This procedure allows us to fabricate a chemical gradient of the wetting properties and the substrate work-function along a few centimeters with a gradient slope higher than 5°/cm. Samples were characterized by cyclic voltammetry during desorption, static contact angle, XPS analysis, and Kelvin probe. Computer simulations based on the Dissipative Particle Dynamics methods were carried out considering a water droplet on a mixed SAM surface. The results help to rationalize the composition of the chemical gradient at different position on the Au surface.
authors.affiliation: Dipartimento di Scienze Fisiche e Chimiche, Università dell'Aquila , Via Vetoio 1, 67100 L'Aquila, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Fioravanti
authors.forename: Francesca
authors.initials: F
authors.lastname: Lugli
authors.forename: Denis
authors.initials: D
authors.lastname: Gentili
authors.forename: Vittoria
authors.initials: V
authors.lastname: Mucciante
authors.forename: Francesca
authors.initials: F
authors.lastname: Leonardi
authors.forename: Luca
authors.initials: L
authors.lastname: Pasquali
authors.forename: Andrea
authors.initials: A
authors.lastname: Liscio
authors.forename: Mauro
authors.initials: M
authors.lastname: Murgia
authors.forename: Francesco
authors.initials: F
authors.lastname: Zerbetto
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Cavallini
mesh_terms: D000327:Adsorption; D004563:Electrochemistry; D006046:Gold / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D013438:Sulfhydryl Compounds; D006046:Gold