RESUMEN
Dimethyldodecylamine N-oxide (DDAO), a unique type of surfactant, shows high surface activity with two distinct energy states at the buried hydrophilic silica/aqueous solution interface studied by total internal reflection (TIR) Raman spectroscopy combined with ratiometric and kinetic analysis. Different from other types of surfactant, i.e., ionic and nonionic, the adsorption of DDAO demonstrates a specific critical surface aggregation concentration (csac) at 0.15 mM gives a complete surface coverage of 6.6 ± 0.3 µmol m-2, much lower than the bulk critical micellization concentration (cmc) at the same conditions (csac ≈ 0.072 cmc). A phase transition of adsorbed layers from liquid crystalline as the intermediate state to the disordered liquid phase is spectroscopically and energetically analyzed. The adsorption of DDAO on silica surfaces is described quantitatively in a potential energy curve.
RESUMEN
A simple imaging add-on utilizing the combination of a relay lens and an optical grating to a nulling ellipsometer for the purpose of imaging and correcting angular distortion is designed, built, and tested. Image contrast is achieved on a standardized silicon wafer, graphene transferred on silicon wafer, a self-assembled monolayer of 1-octadecanethiol on gold, and a 1:1 mixture of dilauroylphosphatidylcholine / distearoylphosphatidylcholine (DLPC/DSPC) on copper. The configuration used in this paper corrects the angular distortion and depth of focus with a spatial resolution of 4.38 µm in the laser's incident direction and 7.81 µm in the direction that is perpendicular to the incident plane together with 3 Å of normal resolution while still maintaining a large field of view of at least 720 µm × 550 µm in focus without executing any line scanning, post-image reconstruction, or specially customized objective method. Better resolution is possibly attained with higher NA optics.