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Quantitative evaluation of perfluorinated alkanethiol molecular order on gold surfaces.
Gamble, Lara J; Radford, David; Grainger, David W; Castner, David G.
Afiliação
  • Gamble LJ; Department of Bioengineering, National ESCA and Surface Analysis Center for Biomedical Problems, Box 351653 Seattle, Washington 98195-1653.
  • Radford D; Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872.
  • Grainger DW; Department of Molecular Pharmaceutics, Health Sciences, University of Utah, Salt Lake City, Utah 84112.
  • Castner DG; Department of Biomedical Engineering, University of Utah, Salt Lake City, Utah 84112.
Biointerphases ; 18(3)2023 05 01.
Article em En | MEDLINE | ID: mdl-37306557
Self-assembled monolayers (SAMs) of perfluoroalkanethiols [CF3(CF2)xCH2CH2SH (x = 3, 5, 7, and 9)] on gold were characterized by x-ray photoelectron spectroscopy (XPS), near edge x-ray absorption fine structure (NEXAFS), and static time-of-flight secondary ion mass spectrometry (ToF-SIMS). Perfluoroalkanethiols of several chain lengths were synthesized using a known hydride reduction method for transforming commercially available perfluoroalkyliodides to corresponding perfluoroalkanethiols. This strategy provides improved product yields compared to other known routes based on hydrolysis from the common thioacetyl perfluoroalkyl intermediate. Angle-dependent XPS analysis revealed that CF3(CF2)xCH2CH2SH (x = 5, 7, and 9; F6, F8, and F10, respectively) SAMs on gold exhibited significant enrichment of the terminal CF3 group at the outer monolayer surface with the sulfur present as a metal-bound thiolate located at the monolayer-gold interface. XPS of the CF3(CF2)3CH2CH2SH (F4) monolayer revealed a thin film with a significant (>50%) amount of hydrocarbon contamination consistent with poorly organized monolayers, while the longest thiol (F10) showed XPS signals attributed to substantial ordering and anisotropy. ToF-SIMS spectra from all four SAMs contained molecular ions representative of the particular perfluorinated thiol used to prepare the monolayer. NEXAFS methods were used to determine degrees of ordering and average tilt for molecules comprising monolayers. The SAMs prepared from the longest (F10) thiols exhibited the highest degree of ordering with the molecular axis nearly perpendicular to the gold surface. The degree of ordering decreased significantly with decreasing length of the perfluorocarbon tail.
Assuntos

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Fluorocarbonos / Ouro Idioma: En Revista: Biointerphases Ano de publicação: 2023 Tipo de documento: Article

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Fluorocarbonos / Ouro Idioma: En Revista: Biointerphases Ano de publicação: 2023 Tipo de documento: Article