Facile and quick formation of cellulose nanopaper with nanoparticles and its characterization.

Cellulose nanofibrils (CNF) is a suitable functional material as its lightweight, huge availability and biodegradable advantages. A direct-evaporation method was employed to prepare the CNF nanopapers with or without Fe3O4 and TiO2 nanoparticles (NPs) in the form of films, which is more facile and efficient in comparison with the methods of vacuum-filtration and cast drying. A combination of three-dimensional (3D) focal stacks and dual-energy imaging method was firstly used to characterize the CNF nanopapers embedded with Fe3O4 and TiO2 NPs, where the locations of the NPs can be clearly and exactly distinguished. Furthermore, the thickness, transparency, magnetism and tensile properties of the CNF nanopapers were characterized. This work shows a facile method for the preparation of CNF nanopapers with or without addition. More importantly, the combination of focal stacks and dual-energy imaging method offers a superior means of characterizing the spatial structures and 3D elemental visualization.