Broadband, site selective and time resolved photoluminescence spectroscopic studies of finely size-modulated Y_2O_3:Eu~(3+) phosphors synthesized by a complex based precursor solution method

摘要

Undoped and Eu~(3+)-doped cubic yttria (Y_2O_3) nanophosphors of good crystallinity, with selective particle sizes ranging between 6 and 37 nm and showing narrow size distributions, have been synthesized by a complex-based precursor solution method. The systematic size tuning has been evidenced by transmission electron microscopy, X-ray diffraction, and Raman scattering measurements. Furthermore, size-modulated properties of Eu~(3+) ions have been correlated with the local structure of Eu~(3+) ion in different sized Y_2O_3:Eu~(3+) nanophosphors by means of steady-state and time-resolved site-selective laser spectroscopies. Time-resolved site-selective excitation measurements performed in the ~7F_0 → ~5D_0 peaks of the Eu~(3+) ions at C_2 sites have allowed us to conclude that Eu~(3+) ions close to the nanocrystal surface experience a larger crystal field than those in the nanocrystal core. Under the site-selective excitation in the ~7F_0 → ~5D_0 peaks, energy transfer between the sites has also been observed.