Upconversion Processes In Rare Earth Doped Fluoride Nanoparticles

Erbium-Ytterbium and thulium-ytterbium codoped nanoparticles systems are investigated for high efficiency upconversion. The near infrared to visible upconversion from two different excitation wavelengths (1550 nm and 980 nm) are of ideal for biomedical applications such as sensing, bioimaging, and photodynamic therapy(PDT) because of the  low absorption and scattering by tissues in this regime. Of particular interest are upconverting nanoparticles which have nearly singular upconversion emission in the visible or near-infrared as this allows for multiplexing in sensing and imaging as well as optimization of energy transfer in PDT.  Various transition metal-based fluoride hosts doped with the upconverting rare earth ions were synthesized and then compared spectroscopically and morphologically.