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

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 similar to30 000degreesC/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 similar to100degreesC) temperature range with a melting temperature of about 70degreesC, 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 100degreesC. 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. (C) 2004 American Institute of Physics.