A review of synthetic methods for the production of upconverting lanthanide nanoparticles

Upconverting lanthanide nanoparticles overcome many of the problems associated with more traditionally used luminescent contrast agents, such as photobleaching, autofluorescence, cytotoxicity and phototoxicity. For this reason, they are an attractive choice for biomedical imaging applications, particularly for imaging in living tissues. The last decade has seen numerous improvements to these nanocrystals, but a comprehensive guide to the synthesis of upconverting lanthanide nanoparticles has not yet been written. Methods vary from paper to paper and from group to group, and results vary between research groups for each method. For this reason, development of these nanoparticles remains a significant endeavor for any research group interested in joining the field. In this review, we look at the varying synthetic methods employed over the last decade and detail methodology for a select few that have been favored in the field.