Preparation and properties of magnetic fluorescent nanomaterials

Abstract

Nanostructure acquiring multiple functionalities is emerging as a promising example for future functional materials. Magnetofluorescent nanomaterials with rapid magnetic response and highly efficient luminescence reveal a great potential in practical applications, such as susceptive biosensor and targeted optical imaging. Taking the best use of magnetic properties and fluorescent properties of nanoparticles, a kind of nanocomposites was devised through assembling magnetic nanoparticles with fluorescent nanoparticles. To date, some strategies have been developed to build various hierarchical magnetofluorescent nanostructure by assembling quantum dots (QDs) and magnetic nanocrystals, such as encapsulation and one-pot synthesis. Herein, we prepared a kind of magnetofluorescent nanocomposites by a new method based on electrostatic interactions. On the basis of previous works, Fe3O4 nanoparticles performed good magnetic properties and the multishell quantum dots (CdSe/CdS/ZnS) showed excellent fluorescent properties. In our work, Fe3O4 magnetic nanoparticles were prepared through a high-temperature pyrolysis method and modified by coupling agent 3-aminopropyl triethoxysilane (APTES). After process of protonation, the surface of Fe3O4 magnetic nanoparticles was covered with a large number of positive charges. And the multishell quantum dots (CdSe/CdS/ZnS) which were prepared through layer-by-layer self-assembly method were modified by mercaptopropionic acid (MPA). Through deprotonation, the surface of the multishell quantum dots was covered with a lot of negative charges. Induced by intense electrostatic interactions, the modified Fe3O4 magnetic nanoparticles were assembled with the modified multishell quantum dots (CdSe/CdS/ZnS) into a type of magnetic fluorescent particles. For rigorous study, the particles were characterized by the means of Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), X-ray diffraction (XRD), fluorescence spectrophotometer and vibrating sample magnetometer (VSM). The FT-IR pattern and TEM figures confirmed the desirable core-shell nanostructure. The nanocomposites performed well crystallization from the XRD measurement as to the original nanocrystals. The results of fluorescence spectrophotometer and VSM confirmed the nanocomposites inherited both magnetic properties and fluorescent properties well. © 2013 Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences.