Xiaoxiao Liu

Pure dark red emission (650–670nm) of NaYF4:Yb/Er upconversion nanoparticles (UCNPs) is achieved by manganese ions (Mn2+) doping. In addition, the Mn2+- doping can also control the crystalline phase and size of the resulting UCNPs simultaneously. Drug delivery studies suggest the promise of these UCNPs as drug carriers for intracellular drug delivery and eventually as a multifunctional nanoplatform for simultaneous diagnosis and therapy. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Lanthanide (Ln3+) doped Gd2O3 nanoparticles (NPs) have been prepared via a thermal treatment of gadolinium carbonate precursor, which was obtained by simple hydrothermal treatment of Gd(NO3)3 solution in the presence of urea and glycerol. The size of the nanoparticles could be fine tuned from 270 to 10 nm by varying the amount of glycerol, which acted as a chelating agent to control the size of the nanoparticles. Calcination of the gadolinium carbonate nanoparticles at 500 °C led to the formation of uniform Gd2O3 nanoparticles without any obvious morphology change. By doping the lanthanide ions (Yb, Er/Tm) into the Gd2O3 host matrix, these nanoparticles emitted strong upconversion (UC) fluorescence under 980 nm near infrared (NIR) excitation. Moreover, their emission colors could be tuned by simply changing either the co-dopant concentration or the dopant species. Water dispersibility was achieved by forming a silica layer on the surface of the Gd2O3 nanoparticles. The possibility of using these silica-coated upconversion nanoparticles for optical imaging in vitro/in vivo has been demonstrated. It was also shown that these Gd2O3 nanoparticles brightened the T1-weighted images and enhanced r1 relaxivity of water protons, which suggested they act as T1 contrast agents for magnetic resonance (MR) imaging. Thus, Gd2O3 nanoparticles doped with Ln3+ ions provide the dual modality of optical and magnetic resonance imaging.