Abstract:

Upconversion nanoparticles are widely used in bioimaging and biomarkers because of their excellent penetration depth and strong luminescence. Mono dispersed core-shell structured NaYF₄:Yb@NaYF₄:Ho nanoparticles with sizes of about 50 nm were synthesized. It was found by spectral analysis that these nanoparticles emitted light centered at a wavelength of 650 nm under the 980 nm laser excitation. Further Nd³⁺ doping caused the NaYF₄:Yb@NaYF₄:Ho nanoparticles to emit strong red light under the 800 nm laser excitation. By analyzing the fluorescence spectra of the Nd³⁺ doped NaYF₄:Yb@NaYF₄:Ho nanoparticles with different structures, it was found that the emission intensity of the NaYF₄:Yb@NaYF₄:Ho, Nd nanoparticles was the strongest, indicating that doping Nd³⁺ ions into the shell layer of the NaYF₄:Yb@NaYF₄:Ho nanoparticles was optimal choice. Finally, the Nd³⁺ concentration of the NaYF₄:Yb³⁺50%@NaYF₄:Ho³⁺1%, Nd³⁺x% nanoparticles was optimized. The experimental results show that the optimized concentration of Nd³⁺ ions is 30%, the luminescence intensity of the NaYF₄: Yb³⁺50%@NaYF₄:Ho³⁺1%,Nd³⁺30% nanoparticles is strongest under an 800 nm laser excitation.

Key words: upconversion nanoparticles, Nd3+ dopant, core-shell structure