Chapter 3 Nanophosphors: From Rare Earth Activated Multicolor-Tuning to New Efficient White Light Sources

Nanophosphors-Based White Light Sources

“…On the other hand, as the emission features of REs can be due to d-f transitions too, host-dependent energy-shifts of the RE emissions can be observed. Since the excited states of RE elements can have L–S coupling and J mixing, a single 2S+1 L J multiplet can describe the excited states of REs sensitive to the host crystal and yield host-dependent emission of RE centers [16]. Therefore, in nanophosphors, dopant-ligand distance and site symmetry may influence the emission from the excited states of RE dopants due to modified J–L coupling and J mixing effects with respect to the lower energy levels [16].…”

“…Since the excited states of RE elements can have L–S coupling and J mixing, a single 2S+1 L J multiplet can describe the excited states of REs sensitive to the host crystal and yield host-dependent emission of RE centers [16]. Therefore, in nanophosphors, dopant-ligand distance and site symmetry may influence the emission from the excited states of RE dopants due to modified J–L coupling and J mixing effects with respect to the lower energy levels [16]. Moreover, changes in the emission efficiency can be induced by dopant-related symmetry breaking in the host material, that can be more effective because of site distortion favored by both the choice of dopant and surface lowered coordination [16].…”

“…It is worth stressing that the peculiar spectroscopy of the nanophosphors does not result from quantum size effects which dominate the emission spectra of semiconductor quantum dots. Instead, the active role is played by size-scale, doping, site symmetry, phase of the crystalline matrix, dopant-ligand distance and strength of the coordination, as well as influence of the surfaces [16].…”

“…While keeping in mind this purpose and in order to make the readership of this review contribution open to non-specialist readers, we clearly indicate nomenclature and provide self-consistent knowledge of basic concepts, definitions, and spectroscopic mechanisms mentioned throughout the paper. For more informative fundamental knowledge, we suggest a preliminary reading of Reference [16] to the reader new to the field of the spectroscopy of phosphors.…”

Photoluminescence and Energy Transfer in Double- and Triple-Lanthanide-Doped YVO4 Nanoparticles

“…represents a unique optical system, in which the luminescent properties can be tuned in a wide range by controlling the energy transfer between ions of different types through adjusting the composition and structure of the material. Such sophisticated optical systems can find applications in different fields, including ultrabroadband optical devices [ 1 , 2 , 3 ], microthermometry [ 4 , 5 , 6 ], bioimaging [ 7 , 8 , 9 , 10 ], and the production of light-emitting flexible materials [ 11 , 12 , 13 ].…”