A study to establishing the structural integrity of core−shell nanoparticles
Lanthanide – doped core – shell nanoparticles, such as NaYF4:Yb/Er@NaYF4, have attracted increasing attention for applications in photonics, photovoltaics, and biological imaging and therapeutics. When compared to conventional nanoparticles that suffer from extensive and uncontrollable dopant − dopant interactions in the host lattice, core–shell nanostructures allow for the rational integration of incompatible dopant ions and regulation of complex interplay of dopant interactions. Despite the rapid progress made on the synthesis and characterization of core–shell nanoparticles, the structural integrity against elemental migration across the core–shell interface still remains unknown.
Our study describes a new approach to detect the diffusion of dopant ions in core–shell nanostructures using Ce3+ and Tb3+ dopant ions as luminescent probes whose emission profile and luminescence lifetime are sensitive to the chemical environment. As designed, Ce3+ and Tb3+ ions were seperately doped into the core and shell layers of a NaYF4@NaYF4 core–shell nanoparticle to eliminate their mutual interactions.
We find that dopant ions in solution-synthesized core–shell nanoparticles are firmly confined in the designed locations because the Ce3+ emission in the nanoparticles is enssentially not affected by Tb3+. However, annealing at certain temperatures (greater than circa 350 OC) promotes diffusion of the dopant ions and leads to degradation of the integrity of the nanoparticles. Due to altered dopant interaction induced by the elemental diffusion, sharp peaks are superimposed on emission spectrum of Ce3+ and the Ce3+ lifetime is decreased as well.
These insights into core–shell nanostructures should enhance our ability to understand lanthanide-doped luminescent nanoparticles. The study also provides a general guideline to proper use of these nanomaterials in technological applications.
Establishing the Structural Integrity of Core-Shell Nanoparticles against Elemental Migration using Luminescent Lanthanide Probes.
Chen B, Peng D, Chen X, Qiao X, Fan X, Wang F
Angew Chem Int Ed Engl. 2015 Oct 19