| This thesis is experimental work on the thermal properties of alkanethiol self-assembled monolayers (SAMs) using nanocalorimetry technique.; The heat capacity measurement of two-dimensional (2D) hexadecanethiol (C16SH) SAMs on planar polycrystalline gold surface is first developed. It is found that the melting of SAMs 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 temperature above 100°C.; The chain length dependence of 2D SAMs is also studied. All of 2D CnSH (n=12, 14, 16, 18) SAMs show obvious melting transitions, both the melting peak temperature and the heat of fusion increase with the chain length. The melting peak temperature is much higher (up to ∼107°C for C18) than the melting temperature of bulk n-alkanethiol, but the heat of fusion is lower than that of bulk n-alkanethiol and n-alkane.; Three-dimensional (3D){09}C16HS{09}SAMs on chemically synthesized gold nanoparticles and thermally evaporated gold islands are studied to verify that the SAMs on single gold islands can also melt. 3D SAMs also exhibit broad melting transition, and the melting temperature is gold particle/island size dependent, and all the melting temperature larger than bulk C16SH but smaller than SAMs on 2D gold surface. The interdigitation effect for SAMs on thiol-stabilized nanoparticles is fully de-coupled in our SAMs on 3D thermally deposited gold islands.; Finally, some preliminary experiments on oligo(ethylene glycol) (OEG) terminated alkanethiols and 2D SAMs on silver substrate are also presented. |
