Experimental and Quantum-Chemical Investigation of Cysteamine as a Capping Ligand for Magnetite Nanoparticles

Cysteamine is a remarkable antioxidant and radioprotector useful in complementary therapies in oncology, as well as for coating metallic nanoparticles for wastewater treatment for the removal of dyes and heavy metals and for photovoltaic cells. We performed a computational study on its chemical reactivity and synthesized magnetite nanoparticles stabilized with cysteamine (MNP@cys) in aqueous suspension. The MNP@cys nanoparticles showed typical crystallization by X-ray diffraction analysis, as anticipated by TEM-SAED analysis, where electron diffraction planes were highlighted. The lattice parameter was 0.8384 nm, the interplanar spacing was 0.2527 nm and the crystallite size was 9.8 nm. The attachment of cysteamine to the surface of the nanoparticles was demonstrated by Raman spectrophotometry and SEM-EDS analysis, which confirmed the good reactivity of cysteamine resulting from quantum chemical simulation. TEM analysis revealed magnetite nanoparticles with a characteristic diameter of approximately 13 nm. Room-temperature VSM measurements indicated very low coercivity and weak hysteresis, consistent with superparamagnetic-like behavior, and yielded an estimated effective magnetic diameter of approximately 10 nm. All these physicochemical characteristics contributed to a good stabilization in an aqueous environment, which is necessary for biomedical applications.