Surface morphology and stability of Langmuir-Blodgett mono- and multilayers of saturated fatty acids by scanning force microscopy

Abstract

The molecular architecture of Langmuir-Blodgett (LB) films of saturated fatty acids of different lengths transferred onto flat solid supports (mica, SiO, highly oriented pyrolytic graphite) was investigated with the scanning force microscope (SFM) under ambient conditions. Intrinsic defects in the LB monolayer have been used to measure the film thickness, which changes by an apparent increment of 0.2 nm per methylene group. The influence of different solid supports on monolayer morphology was determined. The investigations were extended to three-dimensional superstructures by deposition of successive monolayers. Reorganization of the bilayer in contact with the aqueous subphase forms regions with different thickness. Molecular resolution was achieved with the SFM on films with more than two layers. We have also determined unit cell parameters of the LB film surface of different fatty acid multilayers. The lattice constants did not change significantly, but the amplitude of the surface corrugations increases with the length of the aliphatic chain. Energetic contributions to monolayer stiffness are discussed. on solid substrates are not always free of defects (e.g. holes) even on a microscopic scale.4 The scanning force microscope,6 SFM, provides a new tool for studying a variety of surface phenomena on a molecular level. It has been

Investigations of pH-dependent domain structure of lead arachidate Langmuir-Blodgett films by means of x-ray specular and diffuse scattering and atomic force microscopy

“…As described, the AFM investigations of a 11 layer LB film of PbA 2 at a scan-length of 12 from surface analysis of approximately 100 nm each. This is surprisingly in the same order of magnitude of the XDS data.…”

“…3 Some authors point out 4-6 that the three-dimensional real structure of many LB systems prevents their further application in technology and industry. Vertical and lateral move-ments of the molecules during and after the transfer, 7-10 partial dewetting of areas at the solid support, [11][12][13] as well as transfer defects like deposition of X-and Y-type layers, 7,8,14,15 are mainly responsible for the formation of a three-dimensional disturbed film architecture. Generally, for Pb 2ϩ -salts of fatty acids on almost untilted herringbone structure has been observed.…”

Spontaneous Assembly in Organic Thin Films Spread on Aqueous Subphase: A Scanning Force Microscope (SFM) Study

“…We have noted that some of the systems expressed 3 x tim) o SUMMARY Mesoscopic structural investigations of LB films showing "collapse" or buildup of 3-D structures, phase separation, and contrast due to elasticity and friction have been made in the past.II.23. 24 We note several significant differences between this work and work by other groups. In the standard Langmuir-Blodgett technique, a film is spread on the aqueous subphase, then compressed in a controlled way until the pressure-area isotherm indicates that the molecules are being pushed showing two height levels.…”

Combination of fluorescence in situ hybridization and scanning force microscopy for the ultrastructural characterization of defined chromatin regions

“…The calibration is discussed in detail elsewhere. 29 Si tips with a radius of ϳ5 nm and a cantilever force con- stant of ϳ0.03 N/m ͑Ultralever, Park Scientific Instruments, Sunnyvale, CA͒ were used. Images of 512ϫ512 pixels were obtained at line scan rates of 5-7 Hz.…”