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Copyright WILEY-VCH Verlag GmbH & Co. KGaA, 69469 Weinheim, Germany, 2017.
Supporting Information
for Small, DOI: 10.1002/smll.201700600
Multifunctional Hyperbolic Nanogroove Metasurface for
Submolecular Detection
Li Jiang, Shuwen Zeng, Zhengji Xu, Qingling Ouyang, Dao-
Hua Zhang, Peter Han Joo Chong, Philippe Coquet, Sailing
He,* and Ken-Tye Yong*
1
Copyright WILEY-VCH Verlag GmbH & Co. KGaA, 69469 Weinheim, Germany, 2017.
Supporting Information
Multifunctional Hyperbolic Nanogroove Metasurface for Sub-molecular
Detection
Li Jiang, † Shuwen Zeng, † Zhengji Xu, † Qingling Ouyang, Dao-Hua Zhang, Peter Han Joo
Chong, Philippe Coquet, Sailing He,* and Ken-Tye Yong*
† These authors contributed equally to this work
* Corresponding author
1. Materials
1.1 Glycerol solutions
Glycerol (99%) was purchased from Sigma-Aldrich. Deionized (DI) water was used to dilute
glycerol solution with various mass concentrations of 0.05%, 0.1%, 0.5%, 1%, 2%, 2.5%, 3%,
5% and 10%. The refractive index of the diluted glycerol solutions were measured by the
abbe refractometer (2WAJ). DI water to the 10% glycerol solution had the refractive index
ranging from 1.3326 to 1.3451.
1.2 Bovine Serum Albumin (BSA) solutions
BSA (98%) was purchased from Sigma-Aldrich. DI water was used to prepare the BSA
solution with various molar concentrations of 0.1 aM, 1 aM, 1 fM, 1pM, 1nM and 1µM.
1.3 Streptavidin solutions
Streptavidin ( ≥13 units/mg protein) was purchased from Sigma-Aldrich. The phosphate
buffered saline (PBS) buffer was used to prepare the streptavidin solution with molar
concentration of 1µM.
1.4 Biotin solutions
Biotin ( 99%) was purchased from Sigma-Aldrich. The phosphate buffered saline (PBS)
buffer was used to prepare the biotin solution with molar concentration of 1 aM, 1 fM, 1pM,
1nM and 1µM.
2
1.5 Hyperbolic nanogroove metasurface
The nanogroove patterns were fabricated by carving into the gold thin film using focused ion
beam (FIB) techinique. The gold thin film (20 mm×20 mm×50 nm) deposited on a SF11 glass
substrate was customized from Platypus Technologies Inc. with low RMS roughness and low
loss performance. The entire nanogroove substrate contains six patches of groove arrays (245
µm×142 µm) and a coupling grating (50 µm×50 µm). Each patch area is 46 µm×46 µm. The
periodicity and width of the nanogrooves are 150 nm and 30 nm. The height of the
nanogroove is 20 nm and the continuous gold thickness between the prism and the
nanogroove is 30 nm.
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2. Supplementary Figures
Figure S1. The effective permittivity of the nanogroove metasurface in the x- and y-
directions with different widths at various frequency. (a) The real part and (b) imaginary part
of the effective permittivity in the x-direction. The wavelength of the epsilon-near-pole
resonance showing the red shift with the decreasing of the groove widths. (c) The real part
and (d) imaginary part of the effective permittivity in the y-direction. The wavelength of the
epsilon-neat-zero effect showing red shift with the increasing of the groove widths.
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Figure S2. Simulation of surface plasmon polaritons propagation along the nanogroove
metasurface. The grating was used to couple the light from the free space to the in-plane
surface waves. The groove nanostructure could propagate the surface plasmon polaritons and
confine the plasmon modes on the ridges.
Figrue S3. The hyperbolic isofrequency surface of the nanogroove metasurface at the
wavelength of 632.8 nm. The values of ɛx and ɛy are around 22 and -12.
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Figure S4. Experimental reflectance curves of the (a) continuous gold thin film and (b)
groove nanostructure with respect to the incident angle. The minimum reflectance occurred at
the surface plasmon resonance condition and the related incident angle was fixed as the
resonance angle.
Figure S5. Simulation results for the nanogroove hyperbolic metasurface with the width 30
nm and period 150 nm. (a) Reflectance curve with respect to the incident angle. The minimum
reflectance corresponding to the surface plasmon resonance angle. (b) The enhanced norm
electric field distributions on the groove surface at the resonance condition. The surface
plasmon polaritons were confined on the groove ridges. The enhanced electric field
distributions of Ex (c) and Ey (d) on the groove surface at the resonance condition.
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Figure S6. Simulated reflectance curves for the nanogroove metasurfaces with different
groove widths but the same periods. The red circles marking the surface plasmon resonance
angle corresponding to the minimum reflectance with the sample solution of DI water. The
insets showing the enhanced electric field distributions at the resonance condition. The
resonance angle of the reflectance curve from (a) to (i) decreasing gradually with the widths
increasing from 20 nm to 100 nm.
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Figure S7. Optical schematic diagram for measuring phase change of the reflected light
induced by SPR effect.
Figure S8. Optical schematic diagram for measuring differential GH shift between TM-
polarized light beam and TE-polarized light beam induced by SPR effect.
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Figure S9. Experimental differential phase change curves of the continuous gold thin film
with respect to refractive index change of sample solutions.
Figure S10. The binding process of 1µM streptavidin molecules functionalized on the groove
metasurface.
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Figure S11. The comparison results of the kinetic binding events between BSA, biotin-
streptavidin and biotin molecules onto hyperbolic nanogroove metasurface.
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3. Detection limit determination
3.1 Detection limit estimation for BSA molecules
For the hyperbolic nanogroove metasurface-based plasmonic sensor, BSA solutions with
different molar concentrations of 0.1 aM, 1 aM, 1fM, 1 pM, 1 nM and 1 µM were respectively
measured. The differential GH shift of 3 µm is obtained for 0.1 aM BSA solution (blue curve
in Figure 4c). The noise limit of the lateral position sensor (Thorlabs, PDP90A) is about 2.5
µm at the wavelength of 632.8 nm with the detected light power of 20 µW. Thus, the
detection limit of BSA molecules can be estimated as 0.1 aM. The volume of the reaction
chamber is 1.5 cm×1.5 cm×0.22 cm and the area of the illuminated spot is 1 mm2. As a result,
the 0.1 aM BSA solution corresponds to 0.13 BSA molecules in the illuminated area (0.13
BSA/mm2), assuming that all molecules are bound to the sensing surface.
3.2 Detection limit estimation for biotin molecules
For the hyperbolic nanogroove metasurface based plasmonic sensor, biotin solutions with
different molar concentrations of 1 aM, 1 fM, 1 pM, 1 nM and 1µM were respectively
measured. For the 1 aM biotin solution, the change in different GH shift is not observable
(green curve in Figure 4d). For the 1 fM biotin solution, a differential GH shift about 7 µm is
measured (pink curve in Figure 4d). Based on the calibration of the lateral position sensor
(Thorlabs, PDP90A), the noise limit is about 2.5 µm at the wavelength of 632.8 nm with the
detected light power of 20 µW. Therefore, the detection limit can be estimated below 1 fM for
biotin molecules.
