3,4-Dimethoxytropolone

In the title compound, C(16)H(12)FIO(3)S, the 4-fluoro-phenyl ring makes a dihedral angle of 72.31 (6)° with the mean plane of the benzofuran fragment. In the crystal, mol-ecules are linked by weak C-H⋯O hydrogen bonds, and by an I⋯I contact [3.7764 (3) Å]. The crystal structure also exhibits a weak C-I⋯π [3.901 (3) Å] inter-action and a slipped π-π inter-action between the furan and benzene rings of neighbouring mol-ecules [centroid-centroid distance = 3.845 (3), inter-planar distance = 3.555 (3) and slippage = 1.465 (3) Å].

A series of praseodymium (Pr3+ ) ion activated Sr3 Gd(1-x) (PO4 )3 :xPr3+ (0 ≤ x ≤ 2.0 mol%) phosphors were prepared and their structural, compositional and luminescence properties were investigated. The X-ray diffraction profiles indicate that the studied phosphors crystallized into body centred cubic structure and the Pr3+ ions have no influence on Sr3 Gd(PO4 )3 phase. The high-resolution scanning electron microscopy images show the agglomeration of particles that are inter-connected and form irregular shape Sr3 Gd(PO4 )3 structures. The excitation transitions corresponding to Pr3+ :3 H4 → 3 P2,1,0 transitions at 445, 471 and 483 nm, respectively, matched well with the emission of blue-light-emitting diode (LED) chip. The emission spectra show strong reddish-orange luminescence through 1 D2 → 3 H4 transition when excited at 445 nm blue wavelength. The synthesized phosphors have the potential to be used as reddish-orange lighting devices.

Yb3+/Er3+/Tm3+- and Yb3+/Er3+/Tm3+/Ho3+-dopedα-NiMoO4nanoparticles were synthesized using a microwave hydrothermal method and studied for white-light emission under 980 nm laser diode excitation. White upconversion (UC) light was successfully obtained with the appropriate control of blue, green, and red emissions by successfully tuning the Er3+and Ho3+concentrations in Yb3+/Er3+/Tm3+- and Yb3+/Er3+/Tm3+/Ho3+-dopedα-NiMoO4, respectively. In addition, the white color emission was shown by the CIE chromaticity coordinates of samples. The energy transfer mechanisms are explained in detail based on the emission spectra and pump power density-dependent UC luminescence intensity in rare earth (Yb3+/Er3+/Tm3+and Yb3+/Er3+/Tm3+/Ho3+)-dopedα-NiMoO4nanoparticles. The results indicate that Yb3+/Er3+/Tm3+- and Yb3+/Er3+/Tm3+/Ho3+-dopedα-NiMoO4nanoparticles can be good candidates for white-light devices.