FTIR-ATR measurements permit detailed structural analysis and in situ titration of carboxylate-terminated self-assembled monolayers. Both monomeric and dimeric/oligomeric acid groups are seen, and their acid-base behavior is directly monitored. Monomers that are hydrogen bonded only to surrounding water molecules have a pKa = 4.9, while the pKa for the aggregated molecules is 9.3.

Deposition of trichlorosilanes with ester groups at their remote termini provides a convenient entry to carboxylic acid‐bearing siloxane‐anchored self‐assembled monolayers. The de‐esterification of these esters has been optimized to minimize monolayer damage, and their quantitative re‐esterification provides clear evidence for the stability of these systems. Both the structure of the ester‐terminated monolayer and its de‐esterification/esterification chemistry can be easily monitored by FTIR‐ATR measurements. This spectroscopic tool, together with a liquid cell that enables IR spectra to be measured in an aqueous environment, enables a detailed structural analysis of the carboxylic acid‐bearing siloxane‐anchored self‐assembled monolayers and an assessment of their acid/base behavior (by in situ titration). The use of D2O instead of H2O for the in situ titration experiments also improves the available IR window. Both monomeric and dimeric/oligomeric acid groups are seen, and the relative ease of deprotonation of these various species can be directly monitored. Monomers of alkyl carboxylic acids that are hydrogen bonded only to surrounding water molecules have a pKa = 4.9, while the pKa for the aggregated molecules is 9.3. Similar behavior is seen for surface‐bound benzoic acids, where the two pKa values are 4.7 and 9.0. The influence of temperature on these structures and their chemistry has been explored to a limited extent as well. When the alkylcarboxylic acid system is cooled to 10 °C, the pKa value for the acid monomers is reduced from 4.9 to 4.5 and increases from 9.3 to 10.3 for the aggregates.

We show that, for molecules with particularly strong dipoles, their organization into a monomolecular layer can lead to depolarization, something that limits the range over which the substrate's work function can be changed. It appears that, with molecules, depolarization is achieved by changes in orientation and conformation, rather than by charge transfer to the substrate as is common for atomic layers.

Highly ordered ZnO crystals of 0.15 μm width and 0.5 μm length were grown on silicon wafers coated with a monolayer of SiCl3(CH2)11−O−C6H5 molecules. Various techniques (contact angle measurements, ellipsometry, ATR-FTIR) were employed for determining the quality of the monolayer coating. In addition, the bare and silane-coated Si wafers were studied by X-ray reflectivity (XR) and grazing-incidence diffraction (GID) using synchrotron radiation. The results obtained point to a possible relationship between the organization of the self-assembled monolayer (SAM) coating, the dipole moment of the headgroup, and the orientation of the ZnO crystals.