FTIR spectra of CGF and PFOTES-CGF are shown in Fig. S2 (Supporting information). The main components of CGF include holocellulose (mixture of cellulose and hemicellulose), lignin, and extractives in various amounts and chemical compositions, and accordingly, CGF has been identified as a natural lignocellulosic fiber. As mirrored in its FTIR spectrum, a broad absorption band located at 3348 cm-1 is assigned to the characteristic stretching vibration of -OH in cellulose; the other three important absorption bands at 1727, 1367 and 1236 cm-1 are ascribed to the presence of carbonyl bonds originated from C=O ester; the absorption band at 1031 cm-1 is associated with the polysaccharides [32]. After PFOTES treatment, there appears no significant differences in characteristic absorption bands, though some changes in its surface morphology have been noted. This is closely correlated to the fact that only a small amount of PFOTES is attached on CGF surface, as further evidenced by EDS results (Fig. S3, Supporting information).