Upconversion in rare-earth ions is a sequential multiphoton process that efficiently converts two or more low-energy photons, which are generally near infrared (NIR) light, to produce anti-Stokes emission of a higher energy photon (e.g., NIR, visible, ultraviolet) using continuous-wave (cw) diode laser excitation. Here, we show the engineering of novel, efficient, and biocompatible NIR_in-to-NIR_out upconversion nanoparticles for biomedical imaging with both excitation and emission being within the “optical transparency window” of tissues. The small animal whole-body imaging with exceptional contrast (signal-to-noise ratio of 310) was shown using BALB/c mice intravenously injected with aqueously dispersed nanoparticles. An imaging depth as deep as 3.2-cm was successfully demonstrated using thick animal tissue (pork) under cw laser excitation at 980 nm.

Date Published: 22 February 2013
PDF: 4 pages
Proc. SPIE 8588, Multiphoton Microscopy in the Biomedical Sciences XIII, 858814 (22 February 2013); doi: 10.1117/12.2000112

Published in SPIE Proceedings Vol. 8588:
Multiphoton Microscopy in the Biomedical Sciences XIII
Ammasi Periasamy; Karsten König; Peter T. C. So, Editor(s)