Protein Amyloid Fibrils as Template for the Synthesis of Silica Nanofibers, and Their Use to Prepare Superhydrophobic, Lotus-Like Surfaces

In this work, amyloid fibrils are used as a template for the preparation of long silica fibers, with a variety of aspect ratios and surface roughness. Starting with beta-lactoglobulin fibrils with typical diameters of about 20 nm and a length of several micrometers, two different strategies are followed to grow silica: either in water at acidic pH values, or in ethanol-water mixtures under Stober conditions and an excellent control of both the thickness and the roughness of the silica layer has been achieved. Silica nanofibers with a thickness ranging from a few nanometers to hundreds of nanometers are prepared. As an application, the rough silica nanotubes are used to create superhydrophobic surfaces by mimicking the structure of the lotus leaf. The papillary structure of the lotus leaf is replicated by depositing 10 mu m colloidal particles in either a single colloidal crystal, or in a binary colloidal crystal made with smaller sub-micrometer particles. Then, silica nanofibers are deposited on the binary colloidal crystal surfaces through a layer-by-layer deposition procedure to replicate the nanoscale roughness provided by wax nanotubes. Upon hydrophobization of the silica nanotubes, the final surfaces are highly superhydrophobic, with a water contact angle of 165.5 degrees.