Morphology and Hydrophobicity of Humic Coatings on Glass as Studied by Atomic Force Microscopy (AFM) and Contact Angle Measurements

Abstract

In nature, many functional nanoarchitectures are self-assembled due to supramolecular interactions of natural organic matter and surfaces of mineral particles. However, direct evidence for molecular mechanisms responsible for these interactions is still missing. Here, we developed silanol derivatives of humic substances capable of self-assembling onto hydroxylated surfaces. By using humic substances from peat and coal and DNA array glass slides, we show that humic adlayers were homogeneous on macroscale, but separated into domains of nanosize in coal HS and submicro size in peat HS. The peat adlayers were characterized with larger roughness of 11 nm versus 5 nm for coal. Measurement of the contact angle showed that application of humic coatings leads to an increase in hydrophobicity of glass. It was shown that treatment of soil aggregates with silanol derivatives of humic acids increases water stability of the aggregates.