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Direct Evidence of a Surface Quenching Effect on Size-Dependent Luminescence of Upconversion Nanoparticles


  • This study was supported in part by the National University of Singapore, the Singapore-MIT Alliance, and the A*STAR (Grant No. SERC-082-101-0026). We thank Q. Su, J. Xu, and L. Tan for their help in sample characterization.


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A series of Yb/Tm co-doped NaGdF4nanoparticles without or with a thin surface protection layer provide direct evidence of a surface quenching effect on size-dependent upconversion luminescence (see picture). The coating preserves the optical integrity of the nanoparticles (right-hand spectrum) and minimizes emission loss induced by surface quenching.