294020.fig.004a
(a)
294020.fig.004b
(b)
294020.fig.004c
(c)
294020.fig.004d
(d)
Figure 4: Pore size distributions of mesoporous TiO2 microspheres prepared with different amounts of urea: (a) 8 mmol; (b) 12 mmol; (c) 16 mmol; (d) 20 mmol.