Single metallic particles and dimers of nanospheres have been used extensively for sensing, but dimers of particles provide attractive advantages because they exhibit multiple modes that can be tuned by the dimer geometry. Here, we employ correlative microscopy of single self-assembled dimers of gold nanorods to study their performance as refractometric sensors. The correlation between atomic force microscopy and single-particle white-light spectroscopy allows us to relate the measured sensitivity to numerical simulations taking into account the exact geometry of the construct. The sensitivity of the antibonding mode is in good agreement with simulations, whereas the bonding mode exhibits a reduced sensitivity related to the accessibility of the gap region between the particles. We find that the figure of merit is a trade-off between the resonance linewidth and its refractive index sensitivity, which depend in opposite ways on the interparticle angle. The presence of two narrow plasmon resonances in the visible to near-infrared wavelength regime makes nanorod dimers exciting candidates for multicolor and multiplexed sensing.

1.
K. A.
Willets
and
R. P.
van Duyne
, “
Localized surface plasmon resonance spectroscopy and sensing
,”
Annu. Rev. Phys. Chem.
58
,
267
297
(
2007
).
2.
A. B.
Taylor
and
P.
Zijlstra
, “
Single-molecule plasmon sensing: Current status and future prospects
,”
ACS Sens.
2
,
1103
1122
(
2017
).
3.
J. P.
Kottmann
,
O. J. F.
Martin
,
D. R.
Smith
, and
S.
Schultz
, “
Non-regularly shaped plasmon resonant nanoparticle as localized light source for near-field microscopy
,”
J. Microsc.
202
,
60
65
(
2001
).
4.
G. J.
Nusz
,
A. C.
Curry
,
S. M.
Marinakos
,
A.
Wax
, and
A.
Chilkoti
, “
Rational selection of gold nanorod geometry for label-free plasmonic biosensors
,”
ACS Nano
3
,
795
806
(
2009
).
5.
E. W. A.
Visser
,
M.
Horáček
, and
P.
Zijlstra
, “
Plasmon rulers as a probe for real-time microsecond conformational dynamics of single molecules
,”
Nano Lett.
18
,
7927
7934
(
2018
).
6.
C.
Lambertz
 et al., “
Single particle plasmon sensors as label-free technique to monitor MinDE protein wave propagation on membranes
,”
Nano Lett.
16
,
3540
3544
(
2016
).
7.
M. A.
Beuwer
,
M. W. J.
Prins
, and
P.
Zijlstra
, “
Stochastic protein interactions monitored by hundreds of single-molecule plasmonic biosensors
,”
Nano Lett.
15
,
3507
3511
(
2015
).
8.
I.
Ament
,
J.
Prasad
,
A.
Henkel
,
S.
Schmachtel
, and
C.
Sönnichsen
, “
Single unlabeled protein detection on individual plasmonic nanoparticles
,”
Nano Lett.
12
,
1092
1095
(
2012
).
9.
J.
Becker
,
A.
Trügler
,
A.
Jakab
,
U.
Hohenester
, and
C.
Sönnichsen
, “
The optimal aspect ratio of gold nanorods for plasmonic bio-sensing
,”
Plasmonics
5
,
161
167
(
2010
).
10.
H.
Chen
,
X.
Kou
,
Z.
Yang
,
W.
Ni
, and
J.
Wang
, “
Shape- and size-dependent refractive index sensitivity of gold nanoparticles
,”
Langmuir
24
,
5233
5237
(
2008
).
11.
M. A.
Beuwer
,
B.
van Hoof
, and
P.
Zijlstra
, “
Spatially resolved sensitivity of single-particle plasmon sensors
,”
J. Phys. Chem. C
122
,
4615
4621
(
2018
).
12.
E.
Prodan
,
C. J.
Radloff
,
N. J.
Halas
,
P.
Nordlander
, and
P.
Norlander
, “
A hybridization model for the plasmon response of complex nanostructures
,”
Science
302
,
419
422
(
2003
).
13.
P.
Nordlander
,
C.
Oubre
,
E.
Prodan
,
K.
Li
, and
M. I.
Stockman
, “
Plasmon hybridization in nanoparticle dimers
,”
Nano Lett.
4
,
899
903
(
2004
).
14.
J. I. L.
Chen
,
Y.
Chen
, and
D. S.
Ginger
, “
Plasmonic nanoparticle dimers for optical sensing of DNA in complex media
,”
J. Am. Chem. Soc.
132
,
9600
9601
(
2010
).
15.
J. H.
Yoon
,
F.
Selbach
,
L.
Schumacher
,
J.
Jose
, and
S.
Schlücker
, “
Surface plasmon coupling in dimers of gold nanoparticles: Experiment and theory for ideal (spherical) and nonideal (faceted) building blocks
,”
ACS Photonics
6
,
642
648
(
2019
).
16.
T.-J.
Yim
,
Y.
Wang
, and
X.
Zhang
, “
Synthesis of a gold nanoparticle dimer plasmonic resonator through two-phase-mediated functionalization
,”
Nanotechnology
19
,
435605
(
2008
).
17.
P. K.
Jain
and
M. A.
El-Sayed
, “
Universal scaling of plasmon coupling in metal nanostructures: Extension from particle pairs to nanoshells
,”
Nano Lett.
7
,
2854
2858
(
2007
).
18.
C.
Sönnichsen
,
B. M.
Reinhard
,
J.
Liphardt
, and
A. P.
Alivisatos
, “
A molecular ruler based on plasmon coupling of single gold and silver nanoparticles
,”
Nat. Biotechnol.
23
,
741
745
(
2005
).
19.
B. M.
Reinhard
,
M.
Siu
,
H.
Agarwal
,
A. P.
Alivisatos
, and
J.
Liphardt
, “
Calibration of dynamic molecular rulers based on plasmon coupling between gold nanoparticles
,”
Nano Lett.
5
,
2246
2252
(
2005
).
20.
C.
Tabor
,
R.
Murali
,
M.
Mahmoud
, and
M. A.
El-Sayed
, “
On the use of plasmonic nanoparticle pairs as a plasmon ruler: The dependence of the near-field dipole plasmon coupling on nanoparticle size and shape
,”
J. Phys. Chem. A
113
,
1946
1953
(
2009
).
21.
A.
Dhawan
,
S. J.
Norton
,
M. D.
Gerhold
, and
T.
Vo-Dinh
, “
Comparison of FDTD numerical computations and analytical multipole expansion method for plasmonics-active nanosphere dimers
,”
Opt. Express
17
,
9688
9703
(
2009
).
22.
S. S.
Aćimović
,
M. P.
Kreuzer
,
M. U.
González
, and
R.
Quidant
, “
Plasmon near-field coupling in metal dimers as a step toward single-molecule sensing
,”
ACS Nano
3
,
1231
1237
(
2009
).
23.
D.
Punj
 et al., “
Self-assembled nanoparticle dimer antennas for plasmonic-enhanced single-molecule fluorescence detection at micromolar concentrations
,”
ACS Photonics
2
,
1099
1107
(
2015
).
24.
V. V.
Thacker
 et al., “
DNA origami based assembly of gold nanoparticle dimers for surface-enhanced Raman scattering
,”
Nat. Commun.
5
,
3448
(
2014
).
25.
H.
Xu
,
E. J.
Bjerneld
,
M.
Käll
, and
L.
Börjesson
, “
Spectroscopy of single hemoglobin molecules by surface enhanced Raman scattering
,”
Phys. Rev. Lett.
83
,
4357
4360
(
1999
).
26.
T.
Zhang
,
N.
Gao
,
S.
Li
,
M. J.
Lang
, and
Q.-H.
Xu
, “
Single-particle spectroscopic study on fluorescence enhancement by plasmon coupled gold nanorod dimers assembled on DNA origami
,”
J. Phys. Chem. Lett.
6
,
2043
2049
(
2015
).
27.
J.
Wu
 et al., “
Angle-resolved plasmonic properties of single gold nanorod dimers
,”
Nano-Micro Lett.
6
,
372
380
(
2014
).
28.
A. M.
Funston
,
C.
Novo
,
T. J.
Davis
, and
P.
Mulvaney
, “
Plasmon coupling of gold nanorods at short distances and in different geometries
,”
Nano Lett.
9
,
1651
1658
(
2009
).
29.
M.
Garai
,
N.
Gao
, and
Q.-H.
Xu
, “
Single-particle spectroscopic studies on two-photon photoluminescence of coupled Au nanorod dimers
,”
J. Phys. Chem. C
122
,
23102
23110
(
2018
).
30.
L.-Y.
Wang
 et al., “
Circular differential scattering of single chiral self-assembled gold nanorod dimers
,”
ACS Photonics
2
,
1602
1610
(
2015
).
31.
W.
Ma
 et al., “
Chiral plasmonics of self-assembled nanorod dimers
,”
Sci. Rep.
3
,
1934
(
2013
).
32.
Z.
Sun
 et al., “
pH-controlled reversible assembly and disassembly of gold nanorods
,”
Small
4
,
1287
(
2008
).
33.
P.
Zijlstra
,
P. M. R.
Paulo
,
K.
Yu
,
Q.-H.
Xu
, and
M.
Orrit
, “
Chemical interface damping in single gold nanorods and its near elimination by tip-specific functionalization
,”
Angew. Chem.
51
,
8352
8355
(
2012
).
34.
X.
Hu
,
W.
Cheng
,
T.
Wang
,
E.
Wang
, and
S.
Dong
, “
Well-ordered end-to-end linkage of gold nanorods
,”
Nanotechnology
16
,
2164
2169
(
2005
).
35.
K. K.
Caswell
,
J. N.
Wilson
,
U. H. F.
Bunz
, and
C. J.
Murphy
, “
Preferential end-to-end assembly of gold nanorods by biotin–streptavidin connectors
,”
J. Am. Chem. Soc.
125
,
13914
13915
(
2003
).
36.
U.
Hohenester
and
A.
Trügler
, “
MNPBEM—A Matlab toolbox for the simulation of plasmonic nanoparticles
,”
Comput. Phys. Commun.
183
,
370
381
(
2012
).
37.
W.
Zhu
 et al., “
Quantum mechanical effects in plasmonic structures with subnanometre gaps
,”
Nat. Commun.
7
,
11495
(
2016
).
38.
L. S.
Slaughter
,
Y.
Wu
,
B. A.
Willingham
,
P.
Nordlander
, and
S.
Link
, “
Effects of symmetry breaking and conductive contact on the plasmon coupling in gold nanorod dimers
,”
ACS Nano
4
,
4657
4666
(
2010
).
39.
L.
Shao
 et al., “
Angle-and energy-resolved plasmon coupling in gold nanorod dimers
,”
ACS Nano
4
,
3053
3062
(
2010
).
40.
K. C.
Woo
 et al., “
Universal scaling and Fano resonance in the plasmon coupling between gold nanorods
,”
ACS Nano
5
,
5976
5986
(
2011
).
41.
F.
Koohyar
,
A. A.
Rostami
,
M. J.
Chaichi
, and
F.
Kiani
, “
Study on thermodynamic properties for binary systems of water + L-cysteine hydrochloride monohydrate, glycerol, and D-sorbitol at various temperatures
,”
J. Chem.
2013
,
601751
.
42.
X.
Wei
 et al., “
Surface plasmon coupling in end-to-end linked gold nanorod dimers and trimers
,”
Phys. Chem. Chem. Phys.
15
,
4258
4264
(
2013
).
43.
Y.
Cheng
,
M.
Wang
,
G.
Borghs
, and
H.
Chen
, “
Gold nanoparticle dimers for plasmon sensing
,”
Langmuir
27
,
7884
7891
(
2011
).
44.
T.
Kawawaki
,
H.
Zhang
,
H.
Nishi
,
P.
Mulvaney
, and
T.
Tatsuma
, “
Potential-scanning localized plasmon sensing with single and coupled gold nanorods
,”
J. Phys. Chem. Lett.
8
,
3637
3641
(
2017
).
45.
W.
Lee
and
D.
Kim
, “
Field-matter integral overlap to estimate the sensitivity of surface plasmon resonance biosensors
,”
J. Opt. Soc. Am. A
29
,
1367
(
2012
).
46.
P. M. R.
Paulo
 et al., “
Tip-specific functionalization of gold nanorods for plasmonic biosensing: Effect of linker chain length
,”
Langmuir
33
,
6503
6510
(
2017
).
47.
P.
Offermans
 et al., “
Universal scaling of the figure of merit of plasmonic sensors
,”
ACS Nano
5
,
5151
5157
(
2011
).
48.
P.
Tuersun
, “
Optimizing the figure of merit of gold nanoshell-based refractive index sensing
,”
Optik
127
,
250
253
(
2016
).
49.
S. M. E.
Peters
,
M. A.
Verheijen
,
M. W. J.
Prins
, and
P.
Zijlstra
, “
Strong reduction of spectral heterogeneity of gold bipyramids for single-particle and single-molecule plasmon sensing
,”
Nanotechnology
27
,
024001
(
2016
).
50.
J.-M.
Rye
 et al., “
Single gold bipyramids on a silanized substrate as robust plasmonic sensors for liquid environments
,”
Nanoscale
10
,
16094
16101
(
2018
).
51.
P. K.
Jain
and
M. A.
El-Sayed
, “
Noble metal nanoparticle pairs: Effect of medium for enhanced nanosensing
,”
Nano Lett.
8
,
4347
4352
(
2008
).
You do not currently have access to this content.