CNCCellulose nanocrystals (CNC) were prepared by controlled acidhydrolysis of cotton fibers based on our previous studies (Wu, Lu,Xu, et al., 2014; Wu, Lu, Zhou, et al., 2014). Medical purified cotton(20 g) and sulfuric acid solution (350 mL, 64 wt%) were mixed at45◦C for 45 min with magnetic stirring. The suspension was diluted6 times to stop the hydrolysis immediately. Then, the suspension was dialyzed to remove residual acid and hydrolysate of cellulosein the suspension. The result was monitored by checking the neu-trality of the dialyzate. Finally, the suspension was sonicated for30 min at room temperature to disperse the aggregation. The solidcontent of the CNC suspension was measured 5 times and the meanvalue was calculated to be 0.63 ± 0.02 wt%.