Tuning the band structures of self-activated luminescence materials for white- emission and biological application.

The properties of the self-activated luminescence materials depend closely on the point defects, crystal size and even shape. Using first-principles calculation, we exploit the influence of oxygen vacancy on the band structure of monoclinic Y$_{2}$WO$_{6}$ . Then by controlling the calcining process and doping with some rare earth elements, strong green emission and also white-emission could be achieved under long-wavelength violet light irradiation. For graphitic- phase C$_{3}$N$_{4}$ (g-C$_{3}$N$_{4})$, bright blue emission was obtained by delamination of the bulk materials and reducing the crystal size. By further reducing the particle to about 5nm, water-dispersible g-C$_{3}$N$_{4}$ quantum dots were produced which show potential application as photodynamic therapy agent. The pH-sensitive emission of g-C$_{3}$N$_{4}$ deduces the high cytotoxicity to cancer cell and low cytotoxicity to the normal cell of g-C$_{3}$N$_{4}$-porphyrin.