(408a) Alkanethiol Self-Assembled Monolayers On Metal Nanoparticles: A Molecular Dynamics Simulation Study

Atomistic molecular dynamics(MD) simulations of self-assembled alkanethiol monolayers have been performed to understand the ligand shell organization of homoligand and mixed ligand surfactants around gold nanoparticle surfaces and on Au(111) surfaces. Mixtures of two different length surfactants on spherical surfaces form interesting striped structures¹, as was found earlier by STM measurement². This striped morphology is not system specific but the stripe thickness depends on various factors, including the repulsion between surfactants, long range electrostatic interaction, length difference between the two surfactants, and other system specific quantities. Our studies for homoligand systems show that at high temperature, molecules on spherical surfaces orient randomly with respect to the surface normal with a small tilt angle³. As the temperature decreases, the molecules order and adopt a larger tilt angle. At low temperature, the equilibrium conformation of homoligand surfactants on spherical surfaces obeys the crystallographic model⁴ whereas at high temperature, the continuous model⁵ is valid. We also discuss the dependence of the tilt angle on different parameters, such as temperature, nanoparticle size and molecular length. This work is supported by the National Science Foundation under CBET.

References:

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