科研之友
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摘要
Rare earth doped NaYF4 nanocrystals have received intensive attention in recent years because of their unique luminescence properties as a result of their very low phonon energy. However, their luminescence is largely limited by the low optical absorption of rare earth ions. This paper presents a novel strategy to prepare highly dispersible and strongly luminescent Eu3+ doped alpha-NaYF4 (alpha-NaYF4:Eu3+) nanocrystals, which can be intensely excited via multi-channel optical absorption. Highly dispersible alpha-NaYF4:Eu3+ nanocrystals are synthesized using a solvothermal method, and they are coated with a SiO2 layer to form the alpha-NaYF4:Eu3+@SiO2 core-shell nanostructures. These alpha-NaYF4:Eu3+@SiO2 core-shell nanostructures are thermally annealed and the SiO2 shell is then removed to obtain the annealed alpha-NaYF4:Eu3+ nanocrystals with strong O2--> Eu3+ charge transfer excitation. Luminescence of the alpha-NaYF4:Eu3+ nanocrystals is further enhanced by energy transfer of organic ligands after forming a type of inorganic-organic hybrid nanostructure. This strategy is also useful for developing other types of dispersible and strongly luminescent nanocrystals.
