Heat capacity measurements of two-dimensional self-assembled hexadecanethiol monolayers on polycrystalline gold

Abstract

The melting characteristics of hexadecanethiol two-dimensional self-assembled monolayers ( SAMs ) grown on polycrystalline Au surfaces are obtained via heat capacity measurements using nanocalorimetry at scanning rates of ∼ 30 000 ° C ∕ s . The analyzed amount of alkanethiol in the form of SAMs is typically in the 10 − 11 mol range. Melting occurs over a broad (full width on the half height ∼ 100 ° C ) temperature range with a melting temperature of about 70 ° C , if the alkanethiol is partially desorbed from the Au surface during thermal treatment. SAMs in their as-deposited state without desorption have melting temperatures above 100 ° C . The heat of fusion is about 20 kJ ∕ mol . Partial desorption of the alkanethiol is directly observed. The melting characteristics of three-dimensional SAMs on Au nanoparticles are comparable to earlier studies using conventional calorimetry.