New Dialkyldithiophosphinic Acid Self-Assembled Monolayers (SAMs): Influence of Gold Substrate Morphology on Adsorbate Binding and SAM Structure

We report the fabrication and characterization of new self-assembled monolayers (SAMs) formed from dihexadecyldithiophosphinic acid [(C16)2DTPA] molecules on gold substrates. In these SAMs, the ability of the (C16)2DTPA headgroup to chelate to the gold surface depends on the morphology of the gold substrate. Gold substrates fabricated by electron-beam evaporation (As-Dep gold) consist of ∼50-nm grains separated by deep grain boundaries (∼10 nm). These grain boundaries inhibit the chelation of (C16)2DTPA adsorbates to the surface, producing SAMs in which there is a mixture of monodentate and bidentate adsorbates. In contrast, gold substrates produced by template stripping (TS gold) consist of larger grains (∼200–500 nm) with shallower grain boundaries (