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8/10/2019 SPIE 2007 Bidault
1/16
SPIE26 August 2007
Local enhanced fields in DNA
templated plasmonic molecules
Sbastien Bidault and Albert PolmanCenter for NanophotonicsFOM Institute AMOLF
20nm
8/10/2019 SPIE 2007 Bidault
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Local fields in gold nanostructures
550nm 550nm
20Au
20
20
n=1.5 n=1.5Ienh
I
enh
Processes are increased between closely-packed particles and lead
to SERS from single molecules. Can this be optimized by relevantnanostructure engineering ??
Plasmon resonances in gold particles : high local fields (SERS,sensing) and increase of radiative decay rates (luminescenceenhancement)
8/10/2019 SPIE 2007 Bidault
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Optimizing nano-lenses and -antennas
Li, Stockman
& Bergman,PRL 2003
L. Rogobete etal, Opt. Lett.2007
Coupling particles ofdifferent sizes and invarious geometries allowstuning of local enhanced
fields and polarizationdependence
Combining strong localfields and high scatteringcross-sections leads tooptimized nanoantennas
Problems : reproducible
fabrication and placementof analyte or luminescentcenter
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SPIE26 August 2007
Why DNA templated self-assembly ?
J. Zheng et al, Nanolett. 06
P. W. K. Rothemund, Nature 06
J. Seelig et al, Nanolett. 07
Are short interparticledistances possible ?
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SPIE26 August 2007
Reproducible synthesis of close-packed NPs
Method: Programmed hybridization of DNA strands attached (C6 thiol)to passivated (BSPP) gold particles (A.P. Alivisatos et al,Nature 1996, D. Zanchet et al, J. Phys. Chem. B 2002)
Head to tail orhead to headhybridizations
are possible
Au + HSSS
+
Analyte can be introduced by further modification of DNA backbone:direct covalent binding or recognition site
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SPIE26 August 2007
Electrophoretic purification
18
5
100bases~30nm
50bases~15nm
Electrophoretic separation of Au particles covalentlyattached to known number of DNA molecules
1885
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SPIE26 August 2007
Electrophoretic purification
8
8
8
100bases~30nm
50bases~
15nm
Electrophoretic separation of Au particles covalentlyattached to known number of DNA molecules
185
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Head to tail example: dimer of 18nm gold
0 10 20 30 40 50 60 700
2
4
6
8
10
1214
16
18
18100bp~33nm
On ~500 particles:85% dimers10% single particles5% larger aggregates %o
fdimers
Center to center distance (nm)
aggregates
52nm
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SPIE26 August 2007
Head to head hybridization
Head to head hybridization brings interparticledistance down to a few nanometers
100nm100nm75%
200nm
55%
5
8
5
8
5
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SPIE26 August 2007
Plasmon mode coupling
Nanostructure size ~ /30: hybridization picture applicable
n=1.5
570nm
8 5
Eenh
n=1.5
530nm
8 5
Eenh
+-+ - + -+ -
+- +-
Longitudinal mode
Transverse mode
Energy
+-
+-
+
-
+
-
+ -+ -
+-+-
+-+-+-
85
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SPIE26 August 2007
Using two DNA sequences
60%
Small interparticledistance (1nm)enables x40 fieldenhancement
n=1.5
18
600nm
8 5
Eenh100nm100nm
5
8
18
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SPIE26 August 2007
Cooperative plasmon coupling
Eenh
Eenh
n=1.5570nm
n=1.5600nm
Cooperative couplingslightly increases field
enhancement (factor 2on intensity)
18 8 5
8 518 8
Eenh
n=1.5590nm
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SPIE26 August 2007
400 450 500 550 600 650 700
0.0
0.2
0.4
0.6
0.8
Opticald
ensity
Wavelength (nm)
35nm
Dimer
Trimer
Towards optical characterization
Extinction spectra in water
Groupings of 35nm Au NPsare obtained after surfaceligand exchange (thio-PEGinstead of BSPP)
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SPIE26 August 2007
500 1000 1500 2000 2500 30000
250
500
750
1000
1250
1500
CCDcounts/30s
W avenumber (cm-1
)
Preliminary results of SERS measurements
Confocal SERS spectra of 460MW thiolatedPEG on Au with 532nm illumination
500 1000 1500 2000 2500 30000
250
500
750
CCDCounts/3
0s
W avenumber (cm-1
)
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Conclusions and perspectives
DNA hybridization allows nanometer-scale distances between goldparticles of different sizes
Plasmon mode coupling in free-standing nanostructure:plasmonic molecule with intensity enhancement reaching 3
orders of magnitude
Enhancement of Raman scatteringis being investigated
Synthesis of nanostructures with aRaman scatterer on the hot-spot isunder way
SCy3
k l d
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Acknowledgements
Synthesis
Ron ZuckermannMelike Firat
Shelley ClaridgeSassan SheikholeslamiPaul Alivisatos
TEM measurements
Hans Meeldijk