NSF Nanoscale Science and Engineering Grantees Conference, Dec 3-6, 2007
Grant # : 0609362
NIRT: GOALI: Self Assembly at Photonic and Electronic Scales
NSF NIRT (or NSEC) Grant 0609362
Stuart Lindsay, Hao Yan, Rudy Diaz, Devens Gust
Arizona State University
This project addresses two issues critical to manufacturing at the nano- and meso-scales:
(1) Can self-assembled DNA scaffolds1-8 be used to self-assemble complex photonic and
electronic structures? (2) Can parts of the scaffold itself be used as active components of such
assemblies?
Self-assembled DNA nanostructures based on Watson-Crick base-pairing (and the assembly of
three-way junctions) are made simply by mixing together component DNA sequences and
annealing the mix. Large (mm-scale) arrays of nanometer-scale motifs have been reported.
Such arrays can be made addressable, and can incorporate chemical function and optical
elements, opening up new possibilities for building electronic, photonic and chemical devices.
Designed appropriately, the cost of arrays that cover surfaces can be quite small, perhaps a few
dollars per square meter of surface covered. The project focuses on renewable energy. The
scaffolds could position quantum dots, photonic antennas, catalysts for light-driven hydrogen
generation or conducting polymers for rationally-designed photovoltaics. One type of array will
incorporate antenna structures that concentrate light on molecules that separate charge. The goal
is to absorb all incident sunlight in just a monolayer of dye molecules, which would greatly
simplify the design of molecular photovoltaic devices.
To obtain complex asymmetric and
aperiodic DNA nanoarchitectures, we
are using nucleated self-assembly of
short DNA oligomers around a long
scaffold strand. The idea is to use many
short “helper strands” to fold a
continuous single stranded genomic
DNA into a predetermined pattern.
The process is illustrated in Fig. 1
(top). One of our probe-bearing
structures is shown in the AFM images
in Fig. 1 (bottom). This is a flat sheet Fig. 1. Top: the self-assembly of rectangular shaped DNA array
DNA “Origami” using single stranded M13 genome DNA and
of folded M13 DNA (7.4kb) displaying through
> 200 short helper strands. Bottom: DNA Origami displaying “ASU”.
“ASU”, made from about 60 protruding
dumb-bell bulges of double-helical DNA (14 base pairs). Assembly is evidently so cooperative
that the yield is essentially 100%, despite the complexity of the structure. One zoom-in image of
the arrays is shown in Fig. 1B.
The construction of self-assembled
photonic device relies on using
rationally
designed
DNA
nanoscaffold
to
self-assemble
metallic nanoparticles (NPs) into
multicomponent
nanostructures
Fig. 2. Demonstrating self-assembled arrays of 5 nm gold nanoparticles on
the origami template shown in Figure 3. Probes were positioned to capture 1
with precisely controlled spatial
(A), 2 (B) or 3(C) particles.
NSF Nanoscale Science and Engineering Grantees Conference, Dec 3-6, 2007
Grant # : 0609362
arrangement of the inter-particle
distances. This is builds on our
process for self-assembling fully
addressable DNA nanoarrays and
labeling any specific desirable
positions with Au NPs and proteins at
sub nm precision. NPs can be placed
anywhere on such arrays. A proof-ofprinciple experiment shown in Fig. 2
illustrates that singly DNA strandlabeled gold NPs can be placed at
desired spots on an Origami DNA
arrays (5 nm Au NPs are used in this
example). Simulations show that
silver NPs will be required in order to
reduce the electron scattering losses
Fig. 3: (a) Design of a finite-sized linear array DNA scaffold to be used as a photonic
testbed. (b) TEM of the array decorated with Au NPs. (c) Monodisprse Ag NPs.
Fig. 4: Predicted cross section as a function of the distance between spheres. At large separations, the single particle plasmon
peak redshifts a little, but, as the particles come close to touching, a new “antenna mode” arises (arrow) and the “single particle”
plasmon takes on the characteristics of a plasmon in a rod-like particle.
in the NP in order to get the desired field enhancement for efficient absorption of light by a
molecular monolayer. Accordingly, we have synthesized monodisperse Ag NPs with diameters
of 26 nm, and these will be used in place of Au when we have developed the appropriate
attachment chemistries. Our first array will be a simple linear structure, in order to make direct
contact with simulations (see below) the design of which is shown in Figure 3a. SEM images of
this array, decorated with Au NPs are shown in Fig. 3b. An SEM image of the 26 nm diameter
Ag NPs is shown in Fig. 3c.
Simulations (Figure 4) indicate that very large field enhancements (many tens of times,
corresponding to a factor of more than a thousand in intensity) can be obtained when particles
couple to produce resonant antenna modes. These occur when particles just touch, or are very
close to touching. As particles overlap, these ‘antenna modes’ revert to the standard plasmon
modes on a rod (a rod because joined spheres eventually form a rod as the overlap is increased).
NSF Nanoscale Science and Engineering Grantees Conference, Dec 3-6, 2007
Grant # : 0609362
A third thrust of the project consists of designing and testing the molecules that will be
used to convert the high-intensity optical field to electricity. Figure 5 shows (a) the molecular
dyad we are presently studying. Figure 5b
shows a histogram of the current
distribution when a gold probe is pulled
away from an ITO surface to which the
dyads are attached by means of the
carboxyl terminus. The gold presumably
interacts with the pyridine on the other side
of the dyad (Figure 5a) so that a peak in the
conductance corresponds to the single
molecule conductance of this molecule as
attached to an ITO electrode.
The
measured conductance (of ca. 2.4 nS)
indicates that a good electronic contact was
made to the ITO by the carboxyl terminus.
Contact:
Stuart Lindsay
Biodesign Institute
Arizona State University
Tempe, AZ 85287-5601
480 965 4691
Stuart.Lindsay@asu.edu
Fig. 5: (a) The molecular dyad used for generating separated charge from
incident light. Note the [pyridine termination on the left and the carboxyl
termination on the right. (b) Histogram of currents measured in a break
junction experiment. The peak at ca. 1 nA probably corresponds to the dyad
conductance (of ca. 2.4 nS).
References
[1]K. Lund, Y. Liu, S. Lindsay and H. Yan, Self-assembling molecular pegboard, J. Am. Chem. Soc., 2005. 126:
17606-17607.
[2] J. Sharma, R. Chhabra, Y. Liu, Y. Ke and H. Yan, DNA-Templated Self-Assembly of Two-Dimensional and
Periodical Gold Nanoparticle Arrays, Angew. Chem. Int. Ed., 2006. 45: 730-735.
[3] S.H. Park, P. Yin, Y. Liu, J. Reif, T.H. LaBean and H. Yan, Programmable DNA Self-assemblies for Nanoscale
Organization of Ligands and Proteins, Nano Lett., 2005. 5: 729-731.
[4] H.Y. Li, S.H. Park, J.H. Reif, T.H. LaBean and H. Yan, DNA-templated self-assembly of protein and
nanoparticle linear arrays, J. Am. Chem. Soc., 2004. 126: 418-419.
[5] Y. Liu, Y. Ke and H. Yan, Self-assembly of symmetric finite size DNA nanoarrays, 2005. 127: 17140-17141.
[6] J. Zhang, Y. Liu, Y. Ke and H. Yan, Periodic Square-Like Gold Nanoparticle Arrays Templated by SelfAssembled 2D DNA Nanogrids on a Surface, Nano Lett., 2006. 6: 248 -251.
[7] C. Lin, E. Katilius, Y. Liu and H. Yan, Self-assembled Signaling Aptamer Nanoarrays for Protein Detection,
Angew. Chem. Int. Ed., 2006. 45: 5296-5301.
[8] B.A.R. Williams, K. Lund, Y. Liu, H. Yan and J.C. Chaput, Self-assembled peptide nanoarrays: An approach to
studying protein-protein interactions, Angew. Chem. Int. Ed., 2007. 46: 3051-3054.