Introducing open films of nanosized cellulose - Atomic force microscopy and quantification of morphology

A method for preparing open, sub-monolayer cellulose films on a silicon substrate is introduced, and the open films were quantified using the three-dimensional information from atomic force microscopy (AFM) height images. The preparation method is based on spin coating low concentrations of trimethylsilyl cellulose (TMSC) on silicon and hydrolysing the TMSC to cellulose using a vapour phase acid hydrolysis. AFM showed that the surfaces consist of nanosized cellulose patches which are roughly 50-100 nm long, 20 nm wide, and 1 nm high. The volume of the cellulose patches was quantified. Examination of the cross section of the cellulose patches revealed that the exaggeration of the lateral dimensions by the AFM tip is small enough to account for a mere ±2% error in the volume quantification. Pilot experiments showed that the volume of the cellulose was largely restored in a wetting/drying cycle but the morphology changed considerably. Because of their small size, the cellulose patches provide a novel approach for interpretation on the molecular architecture of cellulose.