Cellulose nanowhiskers as one kind of renewable and biocompatible nanomaterials evoke much interest because its versatility in various applications. Herein, the sisal cellulose with ultrathin diameter 5–10 nm, high crystallinity 74% C6 carboxylate groups converted from primary hydroxyls were prepared via a 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)/NaBr/NaClO system selective oxidizat...