Magnetic nanocomposite with fluorescence enhancement effect based on amino acid coated-Fe3O4 functionalized with quantum dots

Abstract

Multifunctional nanoparticles with magnetic and fluorescent properties have high potential in different areas. A very attractive feature of these nanoparticles is that they can be controlled by an external magnetic field and monitored by fluorescence. For biological applications, the magnetic nanoparticles (MNPs) must be biocompatible and dispersible in water, which requires surface modification. This paper describes the synthesis of Fe3O4 MNPs modified with three amino acids (AA): L-Tryptophan (Trp), l-Phenylalanine (Phe) and l-Tyrosine (Tyr) by a co-precipitation method in a one-step reaction without the use of a spacer agent. The potential of AA as a robust anchor was assessed by binding mercaptopropionic acid (MPA)-coated CdTe quantum dots (QDs) to Fe3O4@AA nanoparticles, leading to a hybrid nanostructure with excellent fluorescent and magnetic properties. In particular, the Fe3O4@Trp@QDs nanocomposite showed a fluorescence enhancement effect due to Förster resonance energy transfer (FRET) from Trp as energy donor to CdTe@QDs as acceptor. The nanomaterials were characterized by high-resolution transmission electron microscopy (TEM), X-Ray diffraction (XRD), zeta potential, thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), Fourier-transform infrared (FT-IR), UV–visible, and fluorescence spectroscopy. The nanocomposite also presents high stability and good dispersibility in water. This nanomaterial may be potentially used in different biomedical and environmental applications.