Pan et al. Nanoscale Research Letters 2011, 6:97 http://www.nanoscalereslett.com/content/6/1/97 Page 4 of 7 Figure 4 Calculated partial density states (PDOS). W (a), C (b) and (c) C, and N (d), (e) and (f) in W-functionalized g-C3N4-zz4. The Fermi level is shifted to 0 eV (dot-dash line). Figure 5 Calculated electronic structures of the Ti-functionalized g-C3N4-zz4. (a) spin-up and (b) spin-down band structures, (c) total density of states (TDOS), and (d) partial density of states (PDOS). The Fermi level is at 0 eV.