Microwave-assisted one-step synthesis of water-soluble manganese-carbon nanodot clusters

Abstract

Using metal coordination to assemble carbon nanodots (CND) into clusters can enhance their photophysical properties for applications in sensing and biomedicine. Water-soluble clusters of CNDs are prepared by one-step microwave synthesis starting from ethylenediaminetetraacetic acid, ethylenediamine and MnCl₂·4H₂O as precursors. Transmission electron microscopy and powder X-Ray diffraction techniques indicate that the resulting clusters form spherical particles of 150 nm constituted by amorphous CNDs joined together with Mn ions in a laminar crystalline structure. The nanomaterial assemblies show remarkable fluorescence quantum yields (0.17–0.20) and magnetic resonance imaging capability (r₁ = 2.3-3.8 mM^–1.s^–1). In addition, they can be stabilized in aqueous solutions by phosphate ligands, providing a promising dual imaging platform for use in biological systems.

Using metal coordination to assemble carbon nanodots (CND) into clusters can enhance their photophysical properties for applications in sensing and biomedicine. Here, carboxylate groups on the surface of carbon nanodots serve as ligands for the coordination of manganese ions, enabling the assembly of optically and magnetically active CND clusters in a one-step microwave-assisted synthesis in water.