A solution-phase process has been developed by CNM users from the University
of California at Riverside, working collaboratively with the Nanophotonics Group
at the Argonne National Laboratory,
for synthesizing stable multifunctional colloidal particles composed of a superparamagnetic
Fe3O4 core, a gold nanoshell, and a mesoporous silica outer layer.
The unique porous silica layer is produced by a surface-protected etching process.
TEM images showing the evolution of Au nanoshells after 12 cycles of seeded growth.
By tuning the pore structure of the silica networks through etching, the shape
and size of the gold nanoparticles can be controlled during the seeded growth,
as well as their interparticle plasmon coupling.
Controllable interparticle coupling enables “hot spots” for surface
enhanced Raman scattering.
The inclusion of responsive superparamagnetic Fe3O4 cores broadens the applications
to include magnetically guided delivery and magnetic resonance imaging. The
evolution from gold seeds to complete shells, and the corresponding change in
plasmon bands, can be precisely controlled by the number of growth cycles and
silica shell porosity.
More information: Q. Zhang, J. Ge, J. Goebl, Y. Hu, Y. Sun, and Y. Yin, Adv.
Mater., 22, 1905 (2010).