Synthesis of NIR Emitting Rare Earth Doped Fluorapatite Nanoparticles for Bioimaging Applications

Abstract

To synthesize biocompatible nanoparticles of FAp co-doped with Yb/Er and Nd/Yb for bioimaging applications. Yb/Er FAp and Nd/Yb FAp was synthesized using microwave assisted wet precipitation and hydrothermal method respectively. Trisodium citrate was used as an organic modifier for the synthesis and then subjected to heat treatment for optical activation. For optical studies, Yb/Er FAp system was excited at 980 nm and Nd/Yb FAp at 800 nm. In the case of Nd/Yb FAp the host matrix absorption and emission was observed, hence Nd/Yb was synthesized without citrate. On heat treatment of this for optical activation studies, when the Yb3+ concentration was increased to 10 mol%, the YbPO4 secondary phase was found to appear. Although, the Yb/Er FAp system resulted in large grain growth, no such grain growth was observed in Nd/Yb FAp and the grains were within the nano size regime even after heat treatment. Both the systems showed successful energy transfer from sensitizer to activator with a quantum yield of 74% for Yb/Er FAp and energy transfer efficiency of 71% for Nd/Yb FAp system. Both the samples were found to be cytocompatible and has the potential for using as probes for bioimaging applications.