Synthesis of Gd-doped CuInS2 quantum dots exhibiting photoluminescence and high longitudinal relaxivity

•Gd-doped CuInS2 quantum dots were synthesized through a simple heat-up reaction.•Gd-doping slowed down the growth of CuInS2 quantum dots.•Gd-doping reduced the photoluminescence intensity of quantum dots slightly.•Gd-doping endowed quantum dots with high relaxivity.

Paramagnetic ions-doped quantum dots (QDs) are attractive dual-modal imaging agents for fluorescence and magnetic resonance imaging. In this work, we report the synthesis of water-soluble Gd-doped CuInS2 (CuInS2:Gd) QDs by incorporating paramagnetic Gd3+ ions into CuInS2 QDs in organic solvents and subsequent surfactant-assisted phase transfer. The Gd doping was realized through a simple heat-up reaction and the growth kinetics of Gd-doped CuInS2 QDs was discussed on the basis of the temporal evolution of the sizes and elemental compositions of the QDs. The effect of Gd doping on the photoluminescence properties of the QDs was also investigated. After encapsulation with polymer surfactants, the obtained water soluble CuInS2:Gd QDs exhibited excellent aqueous stability, ultra small size and a large longitudinal relaxivity (r1) of 12.84 mM−1 s−1, showing great promise as dual fluorescent-paramagnetic nanoprobes for bio-imaging applications.