Multifunctional magnetic-fluorescent Ni-doped ZnAl2O4 nanoparticles with second biological NIR window fluorescence

Abstract

Nanocrystals with combined properties of magnetic and fluorescence are considered as “multifunctional materials” or “smart materials” which have promising biological applications including dual-modal imaging, biological research, targeted drug delivery, clinical diagnostics and therapeutics. Utilizing a green hydrothermal method, magnetic nanocrystals Ni-doped ZnAl2O4 with broadband emission at ∼1200nm have been developed as a new type of multifunctional material. The obtained ultrasmall nanocrystals in sub-10nm range are more easily for body clearance and less toxicity in theory. Ni ions are demonstrated distribute homogeneously in +2 valance state, which provides ferromagnetism in the diamagnetic matrix of ZnAl2O4. Under the excitation of 670nm, the whole broad emission band centered at 1200nm fully covers the second near-infrared window (1.1–1.4μm). These ultrasmall Ni-doped ZnAl2O4 nanocrystals with magnetic-fluorescent multifunctionality open a door to more efficient and safer biological probes.