Packing Defects in Fatty Amine Self-Assembled Monolayers on Mica as Revealed from AFM Techniques

Author(s)

Benitez, Jose J. ; Heredia-Guerrero, Jose A. ; San-Miguel, Miguel A. ; Galloway, Heather C.

• Document type: Journal article
• Source: Journal of Physical Chemistry B; v. 122, n. 2, p. 7-pg., 2018-01-18.

Abstract

Self-assembled monolayers of n-octadecylamine (ODA-SAMs) on mica have been prepared and studied by contact and jumping mode atomic force microscopy (AFM). Adhesion and friction data show that the compactness of the monolayers spontaneously increases as they are allowed to ripen. Molecular packing can also be induced by the controlled mechanical perturbation exerted by the probe when getting into and out of contact intermittently. Under these conditions, defects and vacancies aggregate giving rise to detectable pinholes uniformly distributed in AFM images. Created pinhole density was found to decrease with ripening time, thus confirming the proposed spontaneous self-healing mechanism. Pinhole density is also suggested as a parameter characterizing the packing degree of ODA-SAMs, and it has been related to their tribological properties. Additionally, molecular dynamics simulations were used to corroborate the compatibility between the packing degree and the observed topography of ODA-SAMs on mica. (AU)

• FAPESP's process: 13/07296-2 - CDMF - Center for the Development of Functional Materials
• Grantee: Elson Longo da Silva
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC
• FAPESP's process: 15/19709-5 - Theoretical studies on the formation of metallic silver nanostructures by electronic irradiation in ternary metal oxides
• Grantee: Miguel Angel San Miguel Barrera
• Support Opportunities: Regular Research Grants