Abstract
Infrared-to-visible upconversion phosphors, erbium ion-doped Y2O3 (Y2O3:Er) nanoparticles (YNP) were synthesized by homogeneous precipitation method. Since the charge on the YNP surface is positive under physiological conditions, the YNP surface was electrostatically PEGylated using a negatively charged poly(ethylene glycol)-b-poly(acrylic acid) (PEG-b-PAAc). The surface charge on PEGylated YNP (PEG-YNP) was effectively shielded by the ads or bed PEG-b-PAAc. The dispersion stability of the YNP was significantly increased by PEGylation. For example, the PEG-YNP dispersed over 1 week under physiological conditions, which is probably due to the steric repulsion by PEG chains on the YNP surface. Using bovine serum albumin (BSA) as a model antigen, protein-installed YNP was prepared. Both BSA and PEG-b-PAAc were added to YNP solution to co-immobilize on the YNP surface (PEG/BSA-YNP). The PEG/BSA-YNP thus prepared specifically recognized anti-BSA antibody and emitted strong upconversion luminescence by near-infrared excitation. The obtained PEG-YNP is promising as a high performance near-infrared bioimaging materials.
