3.2 SEM and TEM analysis
The morphology of the N doped TiO2 particles measured by SEM was given in Fig. 2A. Noticeably,
the sample was mainly composed of 8~13 nm spherical particles and presented the porous structures,
which was a little larger than the value determined by XRD analysis. That is because some aggregation
has occurred during the synthesis process. Meanwhile, TEM images of the N doped TiO2 sample were
also conducted and shown in Fig.2B. It could be observed that the sample consisted of a great deal of
small nano-particles and the crystallite size was about 6 nm in diameter, which was in accordance with
the crystallite sizes calculated from the XRD patterns. In addition, a slight agglomeration was also
observed.