Efficient modulation of upconversion luminescence in NaErF4-based core–shell nanocrystals

Efficient modulation of upconversion luminescence in heavily-doped core–shell nanocrystals by the tuning of [F]/[RE] ratio during synthesis.

A facile aqueous synthesis strategy for hexagonal phase NaGdF4 nanorods

A facile aqueous synthesis method is explored to synthesize hydrophilic β-NaGdF₄ nanorods at 60 °C.

Enhanced Red Emission in Er3+-Sensitized NaLuF4 Upconversion Crystals via Energy Trapping

Luminescence efficiency of trivalent lanthanide-doped upconversion (UC) materials is significantly limited by luminescence concentration quenching. In this work, red UC emission is dramatically enhanced in Er³⁺-sensitized NaLuF₄ UC crystals through energy trapping under multiple excitation wavelengths. Cross-relaxation quenching and the energy migration to internal lattice defects are simultaneously suppressed by confining the excitation energy in the Er³⁺ activator after introducing the Tm³⁺ or Ho³⁺ energy trapping center. The enhanced red UC emission (Er³⁺: 660 nm) mainly comes from the effective excitation energy confinement by Tm³⁺ and Ho³⁺ trapping centers through an easy energy transfer between Er³⁺ and Tm³⁺/Ho³⁺: ⁴I_11/2 (Er³⁺) → ³H₅ (Tm³⁺) → ⁴I_13/2 (Er³⁺) and ⁴I_11/2 (Er³⁺) → ⁵I₆ (Ho³⁺) → ⁴I_13/2 (Er³⁺). It is found that the confining efficiency of excitation energy in Er³⁺-sensitized NaLuF₄ crystals is higher than that in Yb³⁺/Er³⁺ cosensitized NaLuF₄ crystals, and the luminescence efficiency of Er³⁺-sensitized NaLuF₄ crystals is much higher than that of Er³⁺-based host sensitization UC crystals (NaErF₄). Moreover, Er³⁺-sensitized UC particles can be efficiently excited by three different wavelengths (808, 980, and 1532 nm), indicating huge advantages for applications in bioimaging, anticounterfeiting, and solar cells.

A facile route to the controlled synthesis of β-NaLuF4:Ln3+ (Ln = Eu, Tb, Dy, Sm, Tm, Ho) phosphors and their tunable luminescence properties

Highly uniform and monodisperse β-NaLuF₄:Ln³⁺ (Ln = Eu, Tb, Dy, Sm, Tm, Ho) hexagonal prisms have been synthesized via a facile two-step hydrothermal method without any organic surfactants.

Morphology/dimensionality induced tunable upconversion luminescence of BiOCl:Yb3+/Er3+ nano/microcrystals: intense single-band red emission and underlying mechanisms

Different morphologies of BiOCl:Yb³⁺/Er³⁺ nano/microcrystals have been synthesized via solvothermal method, and the dependence of UC luminescence performance on morphology/dimension have been explored.

Facile synthesis and emission enhancement in NaLuF4 upconversion nano/micro-crystals via Y3+ doping

A series of Y³⁺-absent/doped NaLuF₄:Yb³⁺, Tm³⁺ nano/micro-crystals were prepared via a hydrothermal process with the assistance of citric acid. Cubic nanospheres, hexagonal microdisks, and hexagonal microprisms can be achieved by simply adjusting the reaction temperature. The effect of Y³⁺ doping on the morphology and upconversion (UC) emission of the as-prepared samples were systematically investigated. Compared to their Y³⁺-free counterpart, the integrated spectral intensities in the range of 445-495 nm from α-, β-, and α/β-mixed NaLuF₄:Yb³⁺, Tm³⁺ crystals with 40 mol% Y³⁺ doping are increased by 9.7, 4.4, and 24.3 times, respectively; red UC luminescence intensities in the range of 630-725 nm are enhanced by 4.6, 2.4, and 24.9 times, respectively. It is proposed that the increased UC emission intensity is mainly ascribed to the deformation of crystal lattice, due to the electron cloud distortion in host lattice after Y³⁺ doping. This paper provides a facile route to achieve nano/micro-structures with intense UC luminescence, which may have potential applications in optoelectronic devices.

Simultaneous phase and size manipulation in NaYF4:Er3+/Yb3+ upconverting nanoparticles for a non-invasion optical thermometer

A series of Er³⁺/Yb³⁺-codoped NaYF₄ upconverting nanoparticles were synthesized via a hydrothermal method.