(a)
(b)
(c)
(d)
(e)
(f)
Figure 4: XPS spectra of MAO and 100 μM-Zn samples. Ti 2p (a), O 1s (b), Ca 2p (c), and P 2p (d) of MAO sample; O 1s (e) and Zn 2p (f) of the 100 μM-Zn sample.