Applications of Highly Bright PbS Quantum Dots to Non-Invasive Near-Infrared Fluorescence Imaging in the Second Optical Window

Abstract

Near-infrared (NIR) fluorescence imaging in the wavelength of 1000–1400 nm (2nd-NIR optical window) is expected to offer better spatiotemporal deep-tissue imaging due to the lower autofluorescence and scattering than that in the 1st-NIR optical window (700–1000 nm). During the past decade considerable progress has been made in the development of NIR fluorescent materials that emit over 1000 nm for non-invasive fluorescence imaging. Although single-walled carbon nanotube (SWNT), rare-earth metal ion doped nanomaterials and silver sulfide (Ag2S) quantum dots (QDs) have been reported as fluorescent probes in the 2nd-NIR optical window, their fluorescence brightness is relatively low, with quantum yields (QY) less than 6%. To achieve deep-tissue imaging with high spatiotemporal resolution, we have developed fluorescent lead sulfide (PbS) QDs with high quantum yields (QY >10%) in the 2nd-NIR region. This paper summarize the synthesis of 2nd-NIR emitting PbS QDs and their applications to the non-invasive fluorescence imaging of lymph nodes, cerebral blood vessels, breast tumors, and phagocytic cells in mice.