Self-assembled monolayers test solution

Another approach in generating molecular insulating layers without the need of chemical conversion after deposition is the use of preliminarily modified molecules which can form dense self-assembled monolayers. To create dense self-assembled monolayers with sufficient robustness and insulating properties, a modified alkyltrichlorosilane with an aromatic end-group (18-phenoxyoctadecyl)tri-chlorosilane (PhO-OTS chemical structure Fig. 6.15a) was synthesized and tested [50]. The SAMs were created in a one-step process from vapor phase or solution. On self-assembly on a natively oxidized silicon surface the n-n interaction between the phenoxy end-groups of adjacent molecules creates an intermolecular top-link, leading to a more closely packed surface compared to monolayer than when linear end groups are used. 

If an enhancement of five to six orders of magnitude can be achieved routinely, TERS for small molecules, which are not in resonance with the laser line, is within reach. These molecules have cross sections of the order of (dff/dfJ) 10 cm sr and are barely seen as adlayers on smooth interfaces by normal Raman spectroscopy. To test this, benzenethiol was chosen, which assumes an essentially vertical orientation to the surface due to its thiol group. The adlayer preparation is quick and easy the adsorption occurs from an etha-nolic solution, and a self-assembled monolayer is formed on previously flame-annealed gold or platinum surfaces. Fig. 10.26 shows TERS spectra for benzenethiol at Au(llO) and Pt(llO) surfaces. The comparison of the spectra reveals the characteristic benzenethiol bands but with sHghtly different band positions and relative intensities for the two samples and a nearly 20-fold lower intensity level for benzenethiol at Pt(llO). The comparison of these data with SER spectra for... 

As an example of SAMs, eorrosion inhibition by self-assembled films formed by adipic acid (AA) molecules on caibon steel surfaces is discussed below. SAMs of AA were formed on iron oxide/caibon steel surfaces by the immersion coating method. The metal was immersed in an aqueous solution containing 60 ppm of Cl (to initiate the corrosion process and the formation of iron oxide) in the absence and presenee of adipic acid. The formation, uniformity, ordering and bonding of the monolayers accompUshed by the immersion method have been evaluated by FTIR and AFM. The electrochemical properties of the unmodified and modified caibon steel surfaces were characterized by polarization study and EIS analysis to test the abiUty of the monolayer to reduce the corrosion of the surface. 

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