Tuning of synthesis conditions by thermal decomposition towards gadolinium-doped manganese carbonate nanoparticles with uniform size and high relaxivity

Abstract

Gd-doped MnCO₃ nanoparticles have been prepared by thermal decomposition of Mn-oleate with 20 mol% Gd-oleate at 310 °C. However, MnCO₃ tends to transform into MnO at a temperature above 300 °C. Developing thermal decomposition below 300 °C for the synthesis of MnCO₃ nanoparticles is therefore highly desirable. Herein, we tested the feasibility of the synthesis of Gd-doped MnCO₃ nanoparticles by the thermal decomposition method at a low temperature of 280–300 °C and explored the effects of several parameters on the phase and uniformity of particles. It was revealed that the Gd-doped MnCO₃ nanoparticles could be obtained only when the Gd doping concentration is within a range of 20–33 mol%, while the uniformity of the resulting Gd-doped MnCO₃ nanoparticles could be improved either by elevating the reaction temperature or prolonging the aging time. In addition, the formation mechanism of MnCO₃ nanoparticles with Gd doping was tentatively proposed based on the information acquired by thermogravimetric-gas chromatography-mass spectrometry. Moreover, the obtained uniform-sized Gd-doped MnCO₃ nanoparticles present high relaxivity and notable positive contrast enhancement towards brain glioma in mice.