971942.fig.004a
(a)
971942.fig.004b
(b)
971942.fig.004c
(c)
971942.fig.004d
(d)
Figure 4: SEM images of the bare SPE (a), MWNT-modified SPE (b), COOH-modified SPE (c), and AChE-ChOx-modified SPE (d).