Figure 2: Surface properties of UCNT–MCE membranes.
(a) Raman and (b) XPS spectra of four different UCNT membranes used in the experiments: (i) pristine, (ii) acid modified, (iii) 5-min plasma-modified and (iv) 10-min plasma-modified membranes. Raman D, G and D’ peaks are labelled in a and XPS C 1 s and O 1 s peaks are labelled in b. Inset of a plots the D/G peak intensity ratio (ID/IG) of the four samples and inset of b plots the C/O peak intensity ratio (IC/IO). Top view: SEM image of (c) pristine and (d) plasma-modified (with 10-min plasma treatment) UCNT membranes. The insets of c and d are high-resolution TEM images of a typical single UCNT before and after plasma (10-min treatment), respectively. The lattice spacing between the two atomic layers is measured to be 0.34 nm. The typical wall numbers of the UCNT are about 10 to 12. Scale bars, 2 μm. Inset scale bars, 5 nm.
