Article

Structures of DNA-linked nanoparticle aggregates.

Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA.
The Journal of Physical Chemistry B (impact factor: 3.7). 07/2006; 110(25):12673-81. DOI:10.1021/jp062212+ pp.12673-81
Source: PubMed

ABSTRACT The room-temperature structure of DNA-linked gold nanoparticle aggregates is investigated using a combination of experiment and theory. The experiments involve extinction spectroscopy measurements and dynamic light scattering measurements of aggregates made using 60 and 80 nm gold particles and 30 base-pair DNA. The theoretical studies use calculated spectra for models of the aggregate structures to determine which structure matches the observations. These models include diffusion-limited cluster-cluster aggregation (DLCA), reaction-limited cluster-cluster aggregation (RLCA), and compact (nonfractal) cluster aggregation. The diameter of the nanoparticles used in the experiments is larger than has been considered previously, and this provides greater sensitivity of spectra to aggregate structure. We show that the best match between experiment and theory occurs for the RLCA fractal structures. This indicates that DNA hybridization takes place under irreversible conditions in the room-temperature aggregation. Some possible structural variations which might influence the result are considered, including the edge-to-edge distance between nanoparticles, variation in the diameter of the nanoparticles, underlying lattice structures of on-lattice compact clusters, and positional disorders in the lattice structures. We find that these variations do not change the conclusion that the room-temperature structure of the aggregates is fractal. We also examine the variation in extinction at 260 nm as temperature is increased, showing that the decrease in extinction at temperatures below the melting temperature is related to a morphological change from fractal toward compact structures.

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Keywords

30 base-pair DNA
 
80 nm gold particles
 
aggregate structure
 
aggregate structures
 
aggregates
 
compact structures
 
diffusion-limited cluster-cluster aggregation
 
DNA-linked gold nanoparticle aggregates
 
dynamic light scattering measurements
 
extinction spectroscopy measurements
 
lattice structures
 
on-lattice compact clusters
 
possible structural variations
 
provides greater sensitivity
 
reaction-limited cluster-cluster aggregation
 
RLCA fractal structures
 
room-temperature aggregation
 
room-temperature structure
 
structure matches
 
theoretical studies use
 

Sung Yong Park