Near-infrared two-photon absorption upconversion of PbS/CdS quantum dots prepared by cation exchange method

Abstract Taking advantage of multi-photon absorption, the semiconductor quantum dots show great potential in the field of bio-logical fluorescence imaging. In this paper, PbS/CdS core-shell quantum dots with the band alignment adjustable from type-I to quasi-type II are prepared through the cation exchange method. The core-shell quantum dots exhibit bright broad-band visible/near-infrared upconversion emission upon the excitation of 1064 nm pulse laser, and the core-shell QDs hold a decay lifetime of hundreds of nanoseconds. These characteristics enable the present PbS/CdS core-shell quantum dots to be a promising candidate for biomedical fluorescence imaging.