Functionalized Au-Fe3O4 nanocomposites as a magnetic and colorimetric bimodal sensor for melamine

Au-Fe3O4 nanocomposites were synthesized and modified with l-(2-mercaptoethyl)-1,2,3,4,5,6-hexanhydro-s-triazine-2,4,6-trione (MTT) for the bimodal detection of melamine. The bimodal detection is based on the aggregation of Au-Fe3O4@MTT nanoparticles (NPs) from the dispersed state upon the formation of special triple hydrogen bonds between melamine and MTT. This phenomenon causes the red shift of the absorption peak and the increase of the spin-spin relaxation time (T2) of the water protons upon addition of melamine at different concentrations to an aqueous solution of Au-Fe3O4@MTT NPs. Furthermore, the dual-modal method exhibits a clear selectivity toward melamine.