FESEM images of cellulose hydrolyzed by sulfuric acid for 90 min (a) bottom of suspension (b) top of suspension. Cellulose suspension was dried overnight in oven at 37°C to remove moisture. The resulting film was sputter coated with gold to prevent charging. FESEM accelerating voltage was 2 kV. Scale bar for (a) is 10 μm and for (b) is 100 nm.