Self-assembled monolayers surface modification

M. Buck reviews in great depth the literature on self-assembled monolayers (SAMs) of thiols on gold, a classic means of surface modification. The wide variety of functional groups that is provided by synthetic chemists makes thiol-SAMs an exciting playground for applications where the gap between two worlds, the inorganic and the organic, needs to be closed. Examples are molecular electronics and biochemistry. 

Mrksich and co-workers developed a MALDI-based assay scheme making use of a target surface modification by self-assembled monolayers (SAMs) [22]. This combination of SAMs and MALDI is predominantly called SAMDI (selfassembled monolayers for MALDI). For SAMDI, a self-assembled monolayer with reactive end groups is used in order to covalently bind enzyme substrates to a surface. To... 

Amylose brushes (a layer consisting of polymer chains dangling in a solvent with one end attached to a surface is frequently referred to as a polymer brush) on spherical and planar surfaces can have several advantageous uses, such as detoxification of surfaces etc. The modification of surfaces with thin polymer films is widely used to tailor surface properties such as wettability, biocompatibility, corrosion resistance, and friction [142-144]. The advantage of polymer brushes over other surface modification methods like self-assembled monolayers is their mechanical and chemical robustness, coupled with a high degree of synthetic flexibility towards the introduction of a variety of functional groups. 

A recent study by DePalma and Tillman [ 10] also demonstrates the potential of surface modification by self-assembled monolayers of low surface energy fiuoroalkyl-containing silanes. Fatty acids, amines and alcohols have long been known to adsorb as monomolecular films on metals. Silane coupling agents have featured strongly in new studies to develop more robust films, covalently bound together and to the metal substrate. 

More recent efforts focused on surface modification of conductive polymers by the SECM, fabrication, and characterization of microstructures. Mandler et al. developed an approach for the formation of a 2D conducting polymer on top of an insulating layer. This approach, based on electrostatically binding a monomer (anilinium ions) to a negatively charged self-assembled monolayer of co-mercaptodecanesulfonate [MDS, HS(CH2)ioS03 ] followed by its electrochemical polymerization. The polyanion monolayer exhibited the properties similar to those of a thin polymer film [167]. 

Similar methods to the formation of hydrophobic self-assembled monolayers (SAMs), as described in the previous section, were used with chemical modification to prepare surfaces with different functionality, such as alkenes or hydro-xylated surfaces. This approach was used by Thirtle et al. [67], where the adsorption of a series on nonionic surfactants from C12E5 to C16E6 onto surfaces... 

Figure 3.11 shows the chemical deposition process of GOx enzyme assembled 2-mercaptoethanol on gold that was previously modified by cobalt tetracarboxylic acid chloride phthalocyanine self-assembled monolayer gold. Electrochemical biosensor was introduced in the following steps pretreatment hydrolysis functionalized surface -> enzyme modification. Shervedani and his coworkers reported a similar... 

The formation of self-assembled monolayers is a powerful tool for surface modification, and it is useful when we need to control surface hydrophilic-ity or prepare fimctional electrodes, for example. Surface modification with belts composed of monolayers of various hydrophihcities can yield surfaces with hydrophilicity gradients. liquid droplets can move across such surfaces against gravity due to favorable interactions with the monolayer surface (Fig. 4.38). 

Common to many of these studies is that selectivity, where it has been examined at all, has only been reported between the template and species of quite different charge or polarity. It is difficult in such cases to attribute selectivity to the geometry of the gate sites rather than changes in the bulk properties of the electrode surface. Gate sites in self-assembled monolayers provide a simple method for the modification of sensor surfaces. However, the degree of selectivity obtainable in this way. 

This section describes the methods which we have been used for preparing substrates for SERS measurements. All of the described methods employed commercially available gold NS from Nanospectra Biosciences Inc (Houston, TX). Modification of particle surfaces was accomplished by forming a self-assembled monolayer of molecules of interest [12]. 

In light of these constraints, an effective chemical modification for anti-stiction treatments involves the application of a molecular film to the micromachine surface. This is most often accomplished through a process known as self-assembled monolayer (SAM) deposition.f Self-assembled monolayers are molecular films that spontaneously form on a (usually pretreated) surface upon exposure to a reactive precursor molecule. SAM precursors generally consist of three main parts a terminal group, a backbone, and a head group. Fig. 3 shows these parts on a model SAM... 

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