Synthesis of Ultrathin MnS Shell on ZnS: Mn Nanorods by One‐Step Coating and Doping for MRI and Fluorescent Imaging

Multifunctional nanoprobes for bioimaging have attracted considerable interest in terms of their potential applications in clinical medicine and diagnosis. This article reports the fabrication of a new bifunctional nanoprobe, consisting of an ultrathin MnS shell coating on ZnS:Mn nanorods (NRs), for bioimaging in combination with fluorescence and magnetic resonance imaging (MRI) techniques. The prepared ZnS:Mn/MnS core–shell NRs show an orange emission at 587 nm in wavelength, suggesting they are well suited for fluorescent bio‐imaging due to their large Stokes shift. After surface modification, the obtained core–shell NRs show a very high relaxivity, 9.30 mM⁻¹s⁻¹ at 0.47 T, in aqueous solution. This value is much higher than most Mn‐based nanocrystal contrast agents reported before. The high relaxivity is strongly related to the ultrathin thickness of the MnS shell, as well as its one‐dimensional nanostructure. The prepared bifunctional nanoprobe also shows effective fluorescent imaging in vitro and MRI enhancement in vivo, which verifies its feasibility and effectiveness.