Nanocrystalline Cellulose Studied with a Conventional SEM

Abstract

Nanocrystalline cellulose has been successfully studied by conventional scanning electron microscopy (SEM, JSM-6510LA). Nanocrystalline cellulose was extracted from the natural fibers by the chemical treatments of alkalization and bleaching followed by acid hydrolysis. Alkalization and bleaching resulted in microfibril cellulose, whereas a mix of micro and nanocrystallines cellulose resulted from acid hydrolysis after bleaching. Nanocrystalline cellulose separated from microcrystalline with a centrifuge at a rotation speed of 7000 rpm and then dispersed in ethanol. Before SEM observation, nanocrystalline cellulose dispersed in ethanol was prepared on three different substrates; i.e. C-tape, Si-plate and C-coated Cu grid, and specimen surface was metallic coated. Crystallinity of the extracted cellulose was indicated from x-ray diffraction (XRD) analysis. SEM micrographs of nanocrystalline cellulose prepared on the C-coated grid showed the clearest morphologies. Crystalline cellulose nanowhiskers with length and width ranging between 300-600 nm and 40-60 nm, respectively, were clearly observed. SEM and transmission electron microscopy (TEM) images of the nanocrystalline cellulose were consistent. Dispersion time of nanocrystalline cellulose in ethanol was an important factor determining on the clarity of SEM/TEM micrograph. It is suggested that choosing a suitable sample preparation technique, conventional SEM is a powerful tool for the characterization of nanomaterials.