Optimized Model Surfaces for Advanced Atomic Force Microscopy Studies of Surface Nanobubbles.
The formation of self-assembled monolayers (SAMs) of binary mixtures of 16-mercaptohexadecanoic acid (MHDA) and 1-octadecanethiol (ODT) on ultraflat template-stripped gold (TSG) surfaces was systematically investigated to clarify the assembly behavior, composition, and degree of possible phase segregation in light of atomic force microscopy (AFM) studies of surface nanobubbles on these substrates. The data for SAMs on TSG were compared to those obtained by adsorption on rough evaporated gold, as reported in a previous study. Quartz crystal microbalance and surface plasmon resonance data acquired in situ on TSG indicate that similar to SAM formation on conventional evaporated gold substrates ODT and MHDA form monolayers and bilayers, respectively. The second layer on MHDA, whose formation is attributed to hydrogen bonding, can be easily removed by adequate rinsing with water. The favorable agreement of the grazing incidence reflection Fourier transform infrared (GIR FTIR) spectroscopy and contact angle data analyzed with the Israelachvili-Gee model suggests that the binary SAMs do not segregate laterally. This conclusion is fully validated by high-resolution friction force AFM observations down to a length scale of 8-10 nm, which is much smaller than the typical observed surface nanobubble radii. Finally, correspondingly functionalized TSG substrates are shown to be valuable supports for studying surface nanobubbles by AFM in water and for addressing the relation between surface functionality and nanobubble formation and properties.
Physical Chemistry I, Department of Chemistry and Biology, and Research Center of Micro and Nanochemistry and Engineering (Cμ), University of Siegen , Adolf-Reichwein-Strasse 2, 57076 Siegen, Germany.|Suzhou Key Laboratory of Macromolecular Design and Precision Synthesis, Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, College of Chemistry, Chemical Engineering and Materials Science, Soochow University , Suzhou 215123, China.
Bo
B
Song
Physical Chemistry I, Department of Chemistry and Biology, and Research Center of Micro and Nanochemistry and Engineering (Cμ), University of Siegen , Adolf-Reichwein-Strasse 2, 57076 Siegen, Germany.|Suzhou Key Laboratory of Macromolecular Design and Precision Synthesis, Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, College of Chemistry, Chemical Engineering and Materials Science, Soochow University , Suzhou 215123, China.
Yi
Y
Zhou
Physical Chemistry I, Department of Chemistry and Biology, and Research Center of Micro and Nanochemistry and Engineering (Cμ), University of Siegen , Adolf-Reichwein-Strasse 2, 57076 Siegen, Germany.
Holger
H
Schönherr