= Solution
A useful net bookkeeping reaction for <thiol> <adsorption> is
$$
\mathrm{Au_{surface}+HS(CH_2)_nOH\longrightarrow
Au_{surface}{-}S(CH_2)_nOH+H_{ads}},
$$
with removal or reaction of the <hydrogen> depending on environment. Equivalently, a simplified overall balance can combine two <hydrogen> atoms into $\mathrm{H_2}$. \b[These balances identify sulfur anchoring; they are not a claim that one elementary <adsorption> step universally releases <hydrogen> gas.]
Molecules arrive at the interface, adsorb through sulfur, and reorganize laterally as coverage grows. Interactions between the chains favor packing and order, with the hydroxyl end groups facing outward. <Gold> surface structure, defects and <adsorption> conditions affect the final film.
\Image[/past-exam-of-the-mphil-in-micro-and-nanotechnology-enterprise-course-of-the-university-of-cambridge/2018/paper-1-sam-wetting.png]
{title=Original schematic of hydroxyl-terminated molecules anchored to gold and the through-liquid contact angle with interfacial-tension balance}
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