Fast and facile size selection processing for high quality cellulose nanowhiskers

Cellulose nanowhiskers (CNWs) are appealing natural materials with a broad range of applications in nanoscience. The hydrolysis of the amorphous regions is a kinetic-controlled process in which the natural fibers undergo degradation at strong acidic conditions. Therefore, as-prepared samples of CNWs are constituted of particles with broad varieties of length and diameter. In fact, the majority of cellulose particles are microcrystalline. For more precise and specific applications, a further purification process of as-synthesized CNWs is required. This purification process must lead to more uniform nanoparticles. Herein, we report a purification protocol based exclusively on successive centrifugation steps. Cotton fibers were used as a cellulose source and the four-step centrifugation protocol applied for purification. Dynamic light scattering and transmission electron microscope techniques were used to verify the changes in the selection process. The initial sample was composed of particles between 50 and 2000 nm. After the four-step purification process, more than 90% of purified particles size ranged from 150 to 400 nm with a net yield of 54%.