![]() ![]() ![]() These materials could be used as potential nanophosphors for white light-emitting diodes (LEDs) applications. Based on the Commission Internationale d'Eclairage (CIE) coordinates calculations, only Dy 3+ and triple Ln 3+ doped YVO 4 samples have CIE coordinates close to the ideal white light values amongst the samples. This observation has been explained on the basis of their full width at half maximum of the emission peak. Interestingly, a significant difference in the asymmetric ratio of electric dipole allowed transition to magnetic dipole allowed transition was observed when different Ln 3+ ions are doped in the same host. This has been related to the energy transfer from Dy 3+ to Eu 3+ or Tm 3+. In case of triple doping (Ln 3+ = Eu 3+, Dy 3+ and Tm 3+), the emission of Dy 3+ is more than that of either Eu 3+ or Tm 3+. ![]() When annealed up to 900 ☌, both the luminescence intensity and the lifetime for silica coated systems increase significantly due to the loss of the silanol group, as well as the extent of reduction of surface non-radiative process at the core-shell formation. This has been attributed to the multi-phonon relaxation arising from high vibrational energy of the silanol group (3750 cm −1). The luminescence intensity and lifetime of those samples were less than those of their counterpart core samples. The silanol group (SiO–H) is present in silica coated samples (heated up to 500 ☌) and acts as luminescence quencher. Successful coating of the silica on the YVO 4:Ln 3+ core could be observed by transmission electron microscopy. Average crystallite sizes of YVO 4:Ln 3+ annealed at 500 and 900 ☌ are found to be ∼30 and ∼80 nm, respectively. Lanthanide ions (Ln 3+ = Eu 3+, Dy 3+, Tm 3+) doped YVO 4 and silica coated YVO 4:Ln 3+ (YVO 4:Ln 2) nanoparticles have been prepared by a microemulsion route using Cetyl trimethyl ammonium bromide (CTAB)/ n-butanol/ hexane/ water. ![]()
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