Preparation and characterization of poly(l-histidine)/poly(l-glutamic acid) multilayer on silicon with nanometer-sized surface structures

The specific design and modification of surfaces is of great interest, especially for functional surfaces and medical applications. In order to obtain films on a surface, the layer-by-layer deposition of polyelectrolytes represents a well-established methodology. The alternating deposition of poly(l-histidine) and poly(l-glutamic acid) results in a defined, continuous surface coating that was thoroughly characterized using X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, ellipsometry, X-ray reflectometry, atomic force microscopy, scanning electron microscopy, contact angle, and electrokinetic measurements. Surface charge, film growth, and final thickness were measured and cross-validated. Additionally, the chemical composition and distribution of polyelectrolytes in the layerstack were determined. Finally, the optical parameters were specified and the surface topography was visualized by several methods. These characterizations revealed a coating with embedded spheroids forming from the bottom layers. This rough surface formed by (PLH/PGA)8 was highly reproducible and might provide unique features for the design of tailored surfaces.

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► Poly(l-histidine) and poly(l-glutamic acid) form continuous coating.
► Film formation, thickness, and chemical composition show homogeneous distribution.
► Topography of coating is dominated by surface anchored, nanometer-sized spheroids.
► Comparatively thin coating of 20 nm thickness.
► Detailed investigation and coherent results of complementary measurement techniques.