Blue emission-dominated NaYbF4@NaYF4:2%Ho@NaYF4 upconversion nanoparticles for detecting ascorbic acid

Abstract

The blue emission-dominated NaYbF₄@NaYF₄:2%Ho@NaYF₄ (CSS) upconversion nanoparticles (UCNPs) were designed to detect ascorbic acid (AA). The blue emission of CSS was increased, ∼34 and ∼8 times higher than that of NaYF₄:2%Ho@NaYbF₄@NaYF₄ (CSS (I)) and NaYbF₄@NaYF₄:20%Yb,2%Ho@ NaYF₄ (CSS (II)), respectively. The dominant blue emission of CSS might be attributed to three aspects: (1) the protected NaYbF₄ core for high near-infrared absorption, (2) the spatial separation of Yb³⁺ and Ho³⁺ preventing back energy transfer, and (3) their inert shell inhibiting surface quenching. It is worth noting that the fluorescence resonance energy transfer (FRET) of the CSS (donor) to MnO₂ nanosheets (acceptor) was developed to trace AA. The detection limit is 0.75 μM and the detection range is 0.5–100 μM. In summary, our work not only explored the blue emission mechanism of Ho³⁺, but also constructed a CSS/MnO₂-based nanosensing platform for the rapid and sensitive detection of AA. The blue emission of Ho³⁺ has promising applications in the field of sensing and detection.