LAUSR

Abstract Carbon may be an ideal surface-coating material on nanoparticles (NPs) for biomedical applications because carbon is biocompatible, nearly chemically inert, and photoluminescent in the visible region. In this research, the carbon-coated ultrasmall gadolinium oxide (Gd2O3@C) core-shell NPs (core = Gd2O3; shell = carbon) were synthesized in aqueous solution using a simple method. The ultrasmall Gd2O3@C NPs (davg = 3.1 nm; aavg = 18.9 nm) had excellent colloidal stability, very high r1 value (16.26 s−1 mM−1; r2/r1 = 1.48), and exhibited photoluminescence in the visible region. In vivo positive (i.e., T1) magnetic resonance images of high contrast indicated that the ultrasmall Gd2O3@C NPs should be a potential T1 magnetic resonance imaging (MRI) contrast agent. Additionally, strong fluorescence in the visible region was observed due to carbon coating on the NP surfaces, indicating that the ultrasmall Gd2O3@C NPs are eligible for use as a dual-modal imaging agent.