Polyamine@silica hybrid nanograss: biomimetic fabrication, structure characterization and surface functionalization

This is a report on the controlled generation of a polyamine@silica hybrid nanograss surface on arbitrary substrates. A very simple biomimetic silica mineralization reaction (i.e., ambient temperature and neutral aqueous medium conditioned hydrolytic polycondensation of alkoxy silane) performed on a self-assembled, nanostructured linear polyethyleneimine (LPEI) matrix allowed the production of nanostructured silica films with specific surface morphologies. It was found that the well-defined and densely arrayed nanograss surface of hybrid LPEI@silica could be achieved by adjusting the crystallization time of LPEI on the substrates, silica deposition time and LPEI concentrations. Comparative studies indicated that the LPEI with a linear backbone is important for nanograss formation due to its specific crystalline nature. By using a polystyrene substrate with tunable surface chemistry, we have confirmed that an efficient molecular-level interaction of LPEI with substrates is important for creation of a high-quality and continuous silica nanograss film. The combined studies from XRD, XPS and zeta potential supported that the crystalline, self-assembled and nanostructured LPEI layer on the substrate serves as catalyst-active and biomimetic template for site-selective silica mineralization to give the polyamine@silica nanograss. Moreover, by modifying the nanograss surface with a fluorocarbon compound, we are able to create a super-liquid-repellent surface, which shows the contact angle of > 179 degrees, 149.6 degrees and 147.3 degrees for water, 1 : 1 water-ethanol in volume (gamma = 24.7 mN M-1) and inkjet ink (gamma = 24.0 mN M-1), respectively. Our nanograss surface has potential applications for liquid transferring, self-cleaning, microfluid devices, sensing and cell engineering.