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Ultra-thin cellulose microfibril fractions were extracted from spruce wood powder using combined delignification,TEMPO-catalyzed oxidation and sonication.Small-angle X-ray scattering analysis [1] of these microfibril fractions in a dilute aqueous suspension(concentration 0.077 wt%)revealed that their shape was in the form of nanostrip with 4 nm width and only about 0.5 nm thicknesses.These dimensions were further confirmed by TEM and AFM measurements.The 0.5 nm thickness implied that the nanostrip could contain only a single layer of cellulose chains.At a higher concentration(0.15 wt%),SAXS analysis indicated that these nanostrips aggregated into a layered structure.The X-ray diffraction of samples collected at different preparation stages suggested that microfibrils were delaminated along the(1 10)planes from the Iβ cellulose crystals.The degree of oxidation and solid-state 13C NMR characterizations indicated that in addition to the surface molecules,some inner molecules of microfibrils were also oxidized,facilitating the delamination into cellulose nanostrips(Figure 1).