synthesized from noble metals such as ruthenium, rhodium, palladium,
silver (Ag), osmium, iridium, platinum, and gold (Au) are attracting
increased attention by researchers around the world looking for advances
in such fields as biomedicine and catalysts.
from Argonne National Laboratory, the Illinois Institute of Technology,
and the University of South Carolina working at U.S. Department of
Energy (DOE) facilities at Argonne including the Advanced Photon Source
(APS), have been successful in synthesizing and characterizing
monodisperse gold-core silver-shell nanoparticles utilizing a
bio-template that has potential as a water soluble catalyst for
converting biomass such as dead trees, branches and tree stumps, yard
clippings, wood chips, and even municipal solid waste into fuels.
metals are attractive avenues for this research because, for one thing,
unlike base metals, they are corrosion-resistant when exposed to damp
core-shell catalysts, where one metal is at the center, i.e., the core,
and the second is at the surface, or the shell, provide distinctive
properties, often a better reactivity, because the core metal particle
could modify the lattice strain of the shell metal, which results in a
shift of the electronic band structure of the shell metal.
Such core-shell, nanometer-sized particles are being studied in most national labs and universities.
the field of bioinorganic chemistry, the use of protein cage templates
has been recently developed as a promising method for the synthesis of
uniform-size metal nanoparticle catalysts.
this research, the protein cage template is apoferritin (Apo), which is
the ferritin protein devoid of an iron core. This protein complex
consists of 24 identical subunits and has a spherical shape with an
outer diameter of 12 nm and an inner cavity of 8 nm, as shown in the
8-nm cavity can be used as the location for a “nanoreactor” in which to
synthesize the metal nanoparticles. The junction between the subunits
consists of 14 empty channels, each 3-4 Å in diameter. These serve as a
pathway between the exterior and interior of the protein core.
metal ions, which function as the nanoreactor, diffuse into the hollow
core of the Apo through these channels and subsequent reduction of metal
ions in the cavity leads to one metal particle per Apo ferritin.
the synthesis of core-shell nanoparticles has been proposed, to date
there has been no report of a successful synthesis of core-shell
nanoparticles inside Apo.
a recent publication in the Journal of Materials Chemistry, the
researchers in this study report for the first time synthesis of
water-soluble, Apo-encapsulated, Au-core Ag-shell nanoparticles smaller
than 5 nm in size and with a narrow size distribution, utilizing an
particles were characterized utilizing several research techniques:
small-angle x-ray scattering carried out at the X-ray Science Division
beamline 12-ID of the APS; extended x-ray absorption fine structure
measurements at the Materials Research Collaborative Access Team 10-ID
x-ray beamline, also at the APS; scanning transmission electron
microscopy done at the Argonne Electron Microscopy Center; scanning
electron microscopy at the Argonne Center for Nanoscale Materials; and
fast protein liquid chromatography performed at the University of South
carefully monitoring the amount of silver precursor, the researchers
were successful in controlling the Ag shell thickness from one layer to
method should lead the way for preparation of other core-shell
nanoparticles that might function as new, potentially high-performance
nanocatalysts for catalytic biofuel reactions in the future.
Such core-shell nanoparticles grown on a protein template can also be explored for future drug delivery systems.
Source: Argonne National Laboratory