Robustly anchored thin films provide a general approach for manipulating the properties of interfaces. These films—often with molecular-scale thicknesses—can express a two-dimensional sheet of controlled chemical functionality, expressing differences in molecular structure or chemical composition, or sites of chemical reactivity. We have employed self-assembled monolayers to produce dense surfaces of methyl groups that reveal how subtle orientational differences in their local structure can generate visible differences in their wetting behavior. These variations can be related to energetics between polar and non-polar phases. The energetics of adsorption to a surface from solution can relatedly be modulated by compositional variations in polar (ethylene glycol chained) and non-polar (alkyl chained) constituencies. Here, dfferences in non-specific protein interactions with a surface can be tailored systematically using robustly anchored mixed molecular films of these groups and explained by measurements of surface energetics. Competing influences of surface composition and its hydrophilicity, and protein activity as affected by solution ionic strength, reveal protein-dependent responses to conditions that make allow tunability in the mobile and stationary phases to effect a particular protein separation. In these and many other applications, surface attachment plays a key role for modulating and controlling interfacial properties. We present methods for covalently grafting anchors to silicon surface via robust silicon-carbon bonds where the product of reaction incorporate sites for further chemistry. Specifically, reactions to prime the surface for second-step azide-alkyne click reactions or surface-initiated living atom-transfer radical polymerization (SI-ATRP) open new means for making surface attachments or tailoring surface properties. On porous silicon supports, these reactions provide opportunities for sensing, where surface modification plays key roles for generating stable substrates, achieving surfaces that avoid fouling, and providing avenues for attachment of capture agents, all of which are needed to be effective.
