Structure of Mixed Self-Assembled Monolayers on Gold Nanoparticles at Three Different Arrangements

In this work, we performed atomistic simulations to study the structural properties of mixed self-assembled monolayers (SAM) of hydrophilic and hydrophobic alkylthiols, with two different chain lengths (C5 and C11), on gold nanoparticles (NPs) at three different arrangements, namely: random, patchy, and Janus domains. In particular, we report the effect of mixing of thiols with unequal carbon chain lengths (C5 and C11) at three different arrangements on the structural properties and hydration of SAMs. Our simulation study reveals that the arrangement of thiols having unequal carbon chains in mixed SAMs is a key parameter in deciding the hydrophilicity of the coated gold NPs. Thus, our findings suggest that the hydration of the SAMs-protected gold NPs is not only dependent on the molecular composition of the thiols, but also on the organization of their mixing. In addition, our results show that the bending of longer thiols, when these are mixed with shorter thiols, depends on the arrangement of thiols as well as the chemical nature of their terminal groups.