Inert-Shell Effects on the Upconversion Dynamics of β-NaYF4:Yb,Er Nanomaterials

摘要

High-quality micron-size crystals of β-NaYF4:Yb~(3+), Er~(3+) are known to have NIR-to-visible upconversion (UC) quantum efficiency (QE) as high as 7% at moderate pump power densities.1 However, P-NaYF4: Yb~(3+), Er~(3+) nanocrystals exhibit more rapid UC dynamics with lower quantum efficiency.2 This is presumed to be due primarily to increased surface quenching effects for nanomaterials. Adding a passive shell of optically-inert un-doped material onto the core UC nanocrystals can effectively reduce the surface quenching. We have studied the optical properties of core and core-shell P-NaYF4:Yb~(3+), Er~(3+) UC nanocrystals and have shown that with sufficient shell thickness, the UC dynamics, and therefore presumably the QE, are similar to those in the bulk.EXPERIMENTAL METHODS