Scanning and Transmission Electron Microscopy (SEM and
TEM): For SEM characterization, a JEOL JSM 6335F microscope
operating at 5 kV was used. Each sample was dispersed into
butanol by means of ultrasonic stirring and a drop evaporated to
dryness on a bronze cylinder. In the case of TEM microscopy, a
Philips CM200 FEG electron microscope operating at 200 kV was
used. Samples were ultrasonically dispersed in butanol and then
dropped on a Cu grid covered with carbon. The thin sections of
cellulose–iron oxide composites were prepared by fixing samples
on an epoxy resin and foiled with quartz cuter in an ultramicrotome.
The particle size was estimated measuring the diameters
directly on the micrograph with an error of 0.2 nm. Image
analyses on micrographs were performed using Digital Micrograph
Computer Software.