Polyol-synthesized Zn_0.9Mn_0.1S nanoparticles as potential luminescent and magnetic bimodal imaging probes: synthesis, characterization, and toxicity study

We report here the synthesis, by the polyol method, of Mn-doped ZnS nanocrystals with the zinc blende structure. Phase transfer of the as-produced quantum dots from organic solvent into water was achieved by surface complexation with mercaptoacetate ligands. The magnetic and optical properties of the powders and aqueous colloids obtained were evaluated by SQUID magnetometry as well as electronic absorption and emission spectroscopies, to test their potential as magnetic and luminescent bimodal probes for medical imaging. With a 10 % concentration of Mn²⁺, the nanoparticles are paramagnetic at body temperature, and the aqueous colloids they form have high relaxivity with a r ₁ value of 20 mM⁻¹ s⁻¹ at 3 T. They are highly luminescent with a blue–green emission on 405-nm excitation. Viability assays and genotoxicity tests on Chinese hamster ovarian cells revealed neither acute cellular death, nor cell toxicity, nor damage to the nucleus after exposure for 24 h to particle doses of up to 100 μg mL⁻¹.