294020.fig.002a
(a)
294020.fig.002b
(b)
294020.fig.002c
(c)
294020.fig.002d
(d)
294020.fig.002e
(e)
294020.fig.002f
(f)
294020.fig.002g
(g)
294020.fig.002h
(h)
Figure 2: SEM images of mesoporous TiO2 microspheres prepared with different amounts of urea: (a) 8 mmol; (b) 12 mmol; (c) 16 mmol; (d) 20 mmol.