Upconversion nanophosphors provide new opportunities for bioapplications because of their stable optical property, increased light penetration depth in tissue, low toxicity, and reduced background scattering compared to conventional markers. First, the seminar will give a review of the recent progress of synthesis of rare-earth (erbium and ytterbium) doped upconversion nanophosphors by using combustion and in-solution thermolysis methods. Second, the particle morphology and the luminescence properties with infrared excitation are investigated. The correlations between the nanoparticle fluorescence, particle crystal structure, synthesis temperature, and precursor conditions are summarized. The dynamic dependence of particle luminescence time on particle size and phonon energy will be analyzed. The kinetic mechanism of the non-linear dependence of the luminescence intensity on the excitation power is discussed. Third, the ability of specific targeting of functionalized upconversion nanophosphors on surfaces coated by biotins will be demonstrated. Finally, the efficacy of photodynamic therapy by using upconversion nanophosphors on singlet oxygen production and lung cancer tissue growth are presented.