Synthesis
and Internal Structure of Finite-Size DNA–Gold
Nanoparticle Assemblies
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Abstract
Spatially defined networks of 15
nm-sized DNA-functionalized gold
nanoparticles (DNA–AuNPs) were studied using dynamic light
scattering (DLS), small-angle X-ray scattering (SAXS), as well as
optical extinction spectroscopy (OES). We use a combination of these
techniques with Monte Carlo simulations of pair-distance distribution
function (PDDF) curves and generalized Mie theory simulations as well
as in situ-transmission electron microscopy (in situ-TEM) to analyze
the internal structure of the finite-size assemblies. The DLS data
show that monodisperse, spherical networks with hydrodynamic radii
of ca. 30 nm are found for reaction mixtures of complementarily functionalized
DNA–AuNPs between 1:15 and 1:20. Different interparticle distances
within these assemblies are identified and quantified. By controlling
the network morphology through selection of the reaction mixture,
center-shell geometries are obtained. The number of shell-AuNPs surrounding
each center-AuNP is determined from the SAXS data and Monte Carlo
simulations. This number is quantified to be ca. 10, with the exact
number depending on the linking DNA double strand. The optical spectra
of the networks are found to be consistent with the structural properties.
The structural information gained here enables a quantitative description
of optical and other physical properties, which is expected to prove
useful for the construction and application of such systems, for example,
in drug release, gene regulation, or external-stimuli-responsive materials