Abstract

The use of red light or near-infrared radiation as a luminescent probe for in vivo bio imaging is crucial in order to restrict the strong absorption of short-wavelength light below 600 nm in tissue. It is demonstrated that the emission color of Yb/Ho codoped NaYF₄ nanoparticles can be tuned from green to red by incorporating Ce³⁺ ions. However, compared with that of the NaYF₄:Yb/Ho nanoparticles, the photoluminescence intensity of the Ce³⁺-tridoped NaYF₄:Yb/Ho nanoparticles is drastically reduced. In this work, Ce³⁺-incorporated core/shell NaYF₄:Yb³⁺50%@NaYF₄:Ho³⁺0.5% nanoparticles are prepared. A strong red emission and a high-intensity ratio between the red emission and green emission are obtained in these upconversion nanoparticles. The emission intensity increases by a factor higher than 120 when compared with that of the NaYF₄:Yb/Ho/Ce nanoparticles. This result indicates that the Ce³⁺ incorporation into the NaYF₄:Yb/Ho nanoparticles promotes a strong quenching effect and reduces the emission intensity; however, the quenching effect can be significantly reduced by incorporating the Ce³⁺ ions into the core/shell NaYF₄:Yb³⁺50%@NaYF₄:Ho³⁺0.5% nanoparticles. A theoretical model is proposed to explain the presence of the quenching effect in the NaYF₄:Yb/Ho/Ce nanoparticles, demonstrating that the quenching is mainly related to the interaction between the Yb³⁺ and Ce³⁺ ions.

© 2016 Chinese Laser Press

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