Fig. 1
TEM images of the folded a GO, b GO-POAA and c GO-chitosan. The size is up to 20 μm wide (inset: interlayer distance of 0.34 nm from the image of high-resolution TEM), which corresponds to the size fractions of d GO, e GO-POAA and f GO-chitosan. The AFM image of g GO on mica, and the height difference between two arrows (the GO and mica) is 1.2 nm, consistent with the thickness of a single of layer GO sheet. The one-layer thickness of h GO-POAA and i GO-chitosan respectively increase to 1.5 and 1.7 nm. The XRD analysis to analyze the crystallinity. After the calculation, the respective interlayer distance for j pristine graphite, GO, k GO-POAA, and GO-chitosan are 0.34, 0.84, 0.84 and 0.85 nm. Raman spectroscopy is used to further determine the crystallinity of l GO, m GO-POAA and n GO-chitosan. The D and G bands are attributed to the local defects/disorders and the sp2 graphitized structure. The ID/IG respective intensity ratios for GO, GO-POAA, and GO-chitosan are 0.83, 0.84 and 0.85. A larger ratio indicates more defects or disorders in a graphitized structure. XPS was used to examine the changes in the chemical states of o graphite and p GO. The deconvoluted C(1s) XPS spectra and fitted peaks: C–C/C=C for graphite, C–C/C=C, C–OH, C=O, and O–C–OH for GO. The C(1s) spectrum for graphite has no oxygen-contained functional groups, but that for GO exhibits these groups