Synthesis of aqueous ferrofluids of ZnxFe3−xO4 nanoparticles by citric acid assisted hydrothermal-reduction route for magnetic hyperthermia applications

► We synthesized Zn substituted magnetite nanoparticles via hydrothermal-reduction route. ► We used citric acid as a reducing agent in this route. ► This route is a facile, low energy and environmental friendly method. ► The nanoparticles obtained by this route were superparamagnetic and stable in water. ► The calculated intrinsic loss power for the sample x=0.3 was 2.36 nH m2/kg.