Multilayer core-shell nanostructures for enhanced 808 nm responsive upconversion

Pressure-induced structural phase transition, irreversible amorphization and upconversion luminescence enhancement in Ln3+-codoped LiYF4 and LiLuF4

“…Lanthanide ions (Ln 3+ ) can generate high-energy UC PL by the successive absorption of multiple low-energy (usually near-infrared, NIR) excitation photons, realized through the ladder-like energy levels depending on their specific electronic configurations. 1–4 Yb 3+ ions are general sensitizers to absorb near-infrared photons (980 nm), while Er 3+ , Ho 3+ , and Tm 3+ are typical activators for UC PL ranging from near-infrared to visible and even ultraviolet regions. 5 Another essential ingredient for the constitution of upconverters is the host material, which offers a crystal lattice to accommodate activator and sensitizer ions at certain concentrations, determining the phonon energy, interionic distance, coordination numbers, and local crystallographic symmetry around the dopants.…”