Magnetic Control of the Manganese Photoluminescence in Fe₃O₄/ l -Cys ZnS:Mn Nanocomposites

We investigated the magnetic control of the Mn photoluminescence (PL) in iron oxide/l-cysteine-capped zinc sulfide (Fe3O4/l-cys ZnS:Mn) nanocomposites via temperature- and field-dependent PL intensity studies. Fe3O4/l-cys ZnS:Mn was synthesized following a wet chemical deposition route and then its physicochemical, morphological, and magnetic properties were characterized. X-ray diffraction analysis indicates the formation of a semiconducting composite material with coexisting phases with high crystalline quality and purity. Electron microscopy reveals that the surfaces of the nanoparticles are clean and smooth, sized between 15 and 30 nm, without any sheathed amorphous phase. Vibrating sample magnetometry and UV light excitation show a clear superparamagnetic behavior and an optical response of Fe3O4/l-cys ZnS:Mn, which revealed its bifunctional nature. Magnetoluminescent coupling at 1.0 T is seen in the form of PL suppression in Fe3O4/l-cys ZnS:Mn from low temperature (10 K) to room temperature, with a PL intensity drop of ∼5% at 10 K and a maximum drop of 10% at room temperature. This observation can be explained by restriction of the energy transfer to Mn orbitals through magnetic ordering and Jahn-Teller distortions. Fe3O4/l-cys ZnS:Mn shows promise as a bifunctional biocompatible compound that can be applied as a theranostic agent and a quantum computational element. A deeper understanding behind the magnetic control of the optical response in bifunctional materials brings forth new arenas in diagnostics and drug delivery.