title: Formation, characterization, and stability of methaneselenolate monolayers on Au(111): an electrochemical high-resolution photoemission spectroscopy and DFT study.
abstract: We investigated the mechanism of formation and stability of self-assembled monolayers (SAMs) of methaneselenolate on Au(111) prepared by the immersion method in ethanolic solutions of dimethyl diselenide (DMDSe). The adsorbed species were characterized by electrochemical measurements and high-resolution photoelectron spectroscopy (HR-XPS). The importance of the headgroup on formation mechanism and the stability of the SAMs was addressed by comparatively studying methaneselenolate (MSe) and methanethiolate (MT) monolayers. Density Functional Theory (DFT) calculations were performed to identify the elementary reaction steps in the mechanisms of formation and decomposition of the monolayers. Reductive desorption and HR-XPS measurements indicated that a MSe monolayer is formed at short immersion times by the cleavage of the Se-Se bond of DMDSe. However, the monolayer decomposes at long immersion times at room temperature, as evidenced by the appearance of atomic Se on the surface. The decomposition is more pronounced for MSe than for MT monolayers. The MSe monolayer stability can be greatly improved by two modifications in the preparation method: immersion at low temperatures (-20 °C) and the addition of a reducing agent to the forming solution.
authors.affiliation: Departamento de Fisicoquímica and ‡Departamento de Matemática y Física, Instituto de Investigaciones en Fisicoquímica de Córdoba (INFIQC), Facultad de Ciencias Químicas, Universidad Nacional de Córdoba , 5000 Córdoba, Argentina.
authors.forename: F P
authors.initials: FP
authors.lastname: Cometto
authors.forename: C A
authors.initials: CA
authors.lastname: Calderón
authors.forename: M
authors.initials: M
authors.lastname: Morán
authors.forename: G
authors.initials: G
authors.lastname: Ruano
authors.forename: H
authors.initials: H
authors.lastname: Ascolani
authors.forename: G
authors.initials: G
authors.lastname: Zampieri
authors.forename: P
authors.initials: P
authors.lastname: Paredes-Olivera
authors.forename: E M
authors.initials: EM
authors.lastname: Patrito
mesh_terms: D000327:Adsorption; D055664:Electrochemical Techniques; D000431:Ethanol / Q000737:chemistry; D006046:Gold / Q000737:chemistry*; D016566:Organoselenium Compounds / Q000737:chemistry*; D056951:Photoelectron Spectroscopy; D011789:Quantum Theory; D012996:Solutions; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013499:Surface Properties; D013696:Temperature
chemical_list: D016566:Organoselenium Compounds; D012996:Solutions; D013438:Sulfhydryl Compounds; C005231:methylmercaptan; D000431:Ethanol; D006046:Gold