Synthesis of NaYF_(4):20% Yb^(3+),2% Er^(3+),2% Ce^(3+)@NaYF_(4) nanorods and their size dependent uptake efficiency under flow condition

Lanthanide doped fluorescent nanoparticles have gained considerable attention in biomedical applications.However,the low uptake efficiency of nanoparticles by cells has limited their applications.In this work,we demonstrate how the uptake efficiency is affected by the size of nanoparticles under flow conditions.Using the same size NaYF_(4):20%Yb^(3+),2%Er^(3+),2%Ce^(3+)(the contents of rare earths elements are in molar fraction)nanoparticles as core,NaYF_(4):20%Yb^(3+),2%Er^(3+),2%Ce^(3+)@NaYF_(4) core-shell structured nanorods(NRs)with different sizes of 60-224 nm were synthesized by thermal decomposition and hot injection method.Under excitation at 980 nm,a strong upconversion green emission(541 nm,^(2)H_(11/2)→^(4) I_(15/2) of Er^(3+))is observed for all samples.The emission intensity for each size nanorod was calibrated and is found to depend on the width of NRs.Under flow conditions,the nanorods with 96 nm show a maximum uptake efficiency by endothelial cells.This work demonstrates the importance of optimizing the size for improving the uptake efficiency of lanthanide-doped nanoparticles.