PVP-coated ultrasmall Nd-doped Gd2O2S nanoparticles for multimodal imaging

Rare-earth (RE) based inorganic nanoparticles (NPs) are emerging nanoprobes, which have been widely explored. Single RENPs as a contrast agent for multimodal bioimaging possess the ability to combine optical, ultrasonic, magnetic and electronic properties without signal interference. In this study, we present a versatile strategy for the synthesis of 15 kinds of ultrasmall rare-earth oxysulfide (RE2O2S) NPs with a size of 3-10 nm. PVP-coated Gd0.8Nd1.2O2S NPs with a size of 6 nm are synthesized through a ligand exchange method and their colloidal stability in culture medium is studied. We demonstrate that the as-prepared NPs are capable of being employed in both T1- and T2-weighted magnetic resonance, X-ray computed tomography, photoacoustic, ultrasound, and second near infrared fluorescence imaging. The results pave the way for bioapplications of ultrasmall RE2O2S NPs.