NIR-to-NIR and NIR-to-blue light upconversion in stoichiometric NaYb(MO4)(2) (M = Mo, W)

作者：Perera S Sameera; Rabuffetti Federico A

来源：CrystEngComm, 2016, 18(31): 5818-5825.

DOI：10.1039/c6ce01118g

Polycrystalline NaYb(MoO4)(2) and NaYb(WO4)(2) exhibited NIR-to-NIR and NIR-to-blue light upconversion under 973 nm excitation. The emission spectra were dominated by a strong NIR (similar to 795 nm) band. Blue (similar to 475 nm), green (similar to 525 and 545 nm), and red (similar to 650 nm) bands were also observed. The origin of these bands was investigated using a combination of steady-state and time-dependent spectrofluorometry, elemental analysis, and Rietveld analysis of synchrotron X-ray diffraction data. The strong NIR emission at similar to 795 nm was assigned to two-photon upconversion from Yb3+-sensitized Tm3+, which was found to be present at trace levels (similar to 1 ppm) in both NaYb(MoO4)(2) and NaYb(WO4)(2). Due to the high efficiency of the energy-transfer from Yb3+ to Tm3+, the intensity of the NIR emission exhibited a linear dependence on the excitation power. Green and red bands were assigned to two-photon upconversion from Yb3+-sensitized Er3+, which was also found to be present at trace levels in both hosts (similar to 1 ppm). In the case of the blue emission, power-dependence and time-dependent spectrofluorometric studies favored cooperative luminescence of Yb3+-Yb3+ dimers, rather than three-photon upconversion from Yb3+-sensitized Tm3+. Local clustering of Yb3+ ions yielding Yb3+-Yb3+ dimers that interact cooperatively under NIR excitation was feasible considering (i) the intrinsic disorder of Na+ and Yb3+ over the same crystallographic site, and (ii) the shortest distance between two adjacent Yb3+ ions (similar to 3.81 angstrom). The significance of probing energy-transfer processes relevant to light absorption and emission in fully concentrated metalate hosts is highlighted.

• 出版日期2016