Abstract

Core–shell structured up-conversion luminescent and mesoporous NaYF4:Yb3+/Er3+@nSiO2@mSiO2 nanospheres were prepared by coating mesoporous SiO2 layers with different thicknesses on NaYF4:Yb3+/Er3+ nanoparticles via a simple two-step sol–gel process. The obtained sample shows a typical mesoporous structure and well-dispersed spherical morphology with a narrow size distribution. The nanospheres exhibit little cytotoxicity (via MTT assay), and ibuprofen (IBU) was used as a model drug to access the release properties of the system in detail. The amount of IBU adsorbed in mesoporous channels increases with the thickness of the ordered mesoporous silica shell coated on the NaYF4:Yb3+/Er3+ nanoparticles. The in vitro release study of IBU reveals a release profile in two steps: an initial diffusion-controlled release, followed by a slower release rate. Furthermore, upon excitation by a 980 nm near-infrared laser, the nanospheres emit green (2H11/2 and 4S3/2 → 4I15/2) and red (4F9/2 → 4I15/2) fluorescence of Er3+ ...

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