Pure cellulose have been isolated from rice straw at 36% yield and hydrolyzed (64% H2SO4, 8.75 mL/g,
45 ◦C) for 30 and 45 min to cellulose nanocrystals (CNCs), i.e., CNC30 and CNC45, respectively. CNC45
was smaller (11.2 nm wide, 5.06 nm thick and 117 nm long) than CNC30 (30.7 nm wide, 5.95 nm thick
and 270 nm long). Freeze–drying of diluted CNC suspensions showed both assembled into long fibrous
structures: ultra-fine fibers (∼400 nm wide) from CNC45 and 1–2 m wide broad ribbons interspersed
with CNC clusters from CNC30. The self-assembled fibers from CNC30 and CNC45 were more highly
crystalline (86.0% and 91.2%, respectively) and contained larger crystallites (7.36 nm and 8.33 nm, respectively)thanricestrawcellulose(61.8%,4.42 nm).Theseself-assembledfibershadessentiallynonporousor
macroporous structures with the CNCs well aligned along the fiber axis. Furthermore, the self-assembled
ultra-fine fibers showed extraordinary structural stability, withstanding vigorous shaking and prolong
stirring in water.