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Virtual Journal for Biomedical Optics

Virtual Journal for Biomedical Optics

| EXPLORING THE INTERFACE OF LIGHT AND BIOMEDICINE

  • Editors: Andrew Dunn and Anthony Durkin
  • Vol. 8, Iss. 7 — Aug. 1, 2013
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The aspect ratio effect on plasmonic properties and biosensing of bonding mode in gold elliptical nanoring arrays

Chia-Yang Tsai, Kai-Hao Chang, Che-Yao Wu, and Po-Tsung Lee  »View Author Affiliations


Optics Express, Vol. 21, Issue 12, pp. 14090-14096 (2013)
http://dx.doi.org/10.1364/OE.21.014090


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Abstract

We investigate both numerically and experimentally the optical properties and biosensing of gold elliptical nanoring (ENR) arrays with various aspect ratios. The gold ENR exhibits a strong localized surface plasmon bonding mode in near-infrared region, whose peak wavelength is red-shifted as increasing the aspect ratio under longitudinal and transverse polarizations. Furthermore, the disk- and hole-like optical properties for longitudinal and transverse modes are observed, which cause different behaviors in field intensity enhancement. For biomolecule sensing, we find that both modes show increased surface sensitivities when enlarging the aspect ratio of gold ENR.

© 2013 OSA

1. Introduction

Noble metal nanoparticles have unique optical properties arising from the excitation of localized surface plasmon resonance (LSPR) which produces a large local field enhancement. Such merit is currently attracting tremendous interest and important for a wide range of emerging applications, from chemical and biological sensing [1

1. J. N. Anker, W. P. Hall, O. Lyandres, N. C. Shah, J. Zhao, and R. P. Van Duyne, “Biosensing with plasmonic nanosensors,” Nat. Mater. 7(6), 442–453 (2008). [CrossRef] [PubMed]

,2

2. K. M. Mayer and J. H. Hafner, “Localized surface plasmon resonance sensors,” Chem. Rev. 111(6), 3828–3857 (2011). [CrossRef] [PubMed]

] to subwavelength waveguiding [3

3. S. A. Maier, P. G. Kik, H. A. Atwater, S. Meltzer, E. Harel, B. E. Koel, and A. A. G. Requicha, “Local detection of electromagnetic energy transport below the diffraction limit in metal nanoparticle plasmon waveguides,” Nat. Mater. 2(4), 229–232 (2003). [CrossRef] [PubMed]

] or imaging [4

4. N. Fang, H. Lee, C. Sun, and X. Zhang, “Sub-diffraction-limited optical imaging with a silver superlens,” Science 308(5721), 534–537 (2005). [CrossRef] [PubMed]

] and nanoparticle trapping [5

5. Y. Tanaka and K. Sasaki, “Efficient optical trapping using small arrays of plasmonic nanoblock pairs,” Appl. Phys. Lett. 100(2), 021102 (2012). [CrossRef]

]. In particular, the ability to generate high field enhancements is determined by the geometry of the nanoparticles [6

6. E. Hao and G. C. Schatz, “Electromagnetic fields around silver nanoparticles and dimers,” J. Chem. Phys. 120(1), 357–366 (2004). [CrossRef] [PubMed]

,7

7. A. M. Kern and O. J. F. Martin, “Excitation and reemission of molecules near realistic plasmonic nanostructures,” Nano Lett. 11(2), 482–487 (2011). [CrossRef] [PubMed]

]. Thereby the characteristics of a myriad of nanostructures including disks [8

8. G. Gantzounis, N. Stefanou, and N. Papanikolaou, “Optical properties of periodic structures of metallic nanodisks,” Phys. Rev. B 77(3), 035101 (2008). [CrossRef]

], triangles [9

9. M. Rang, A. C. Jones, F. Zhou, Z. Y. Li, B. J. Wiley, Y. Xia, and M. B. Raschke, “Optical near-field mapping of plasmonic nanoprisms,” Nano Lett. 8(10), 3357–3363 (2008). [CrossRef] [PubMed]

], cubes [10

10. S. Zhang, K. Bao, N. J. Halas, H. Xu, and P. Nordlander, “Substrate-induced Fano resonances of a plasmonic nanocube: a route to increased-sensitivity localized surface plasmon resonance sensors revealed,” Nano Lett. 11(4), 1657–1663 (2011). [CrossRef] [PubMed]

], crosses [11

11. M. Zhang, X. Zhou, and Y. Fu, “Plasmonic resonance excited extinction spectra of cross-shaped Ag nanoparticles,” Plasmonics 5(4), 355–361 (2010). [CrossRef]

], and pyramids [12

12. P. Y. Chung, T. H. Lin, G. Schultz, C. Batich, and P. Jiang, “Nanopyramid surface plasmon resonance sensors,” Appl. Phys. Lett. 96(26), 261108 (2010). [CrossRef] [PubMed]

] have been explored in recent years. Among various metal nanostructures, elliptical nanoring (ENR) is a hybrid nanoparticle geometry that offers the highly tunable plasmon resonances essentially arising from plasmon hybridization between an oval-shaped nanodisk and an elliptical nanohole. This hybridization results in two plasmonic modes which are the low-energy symmetric bonding mode and the high-energy asymmetric antibonding mode respectively [13

13. E. Prodan, C. Radloff, N. J. Halas, and P. Nordlander, “A hybridization model for the plasmon response of complex nanostructures,” Science 302(5644), 419–422 (2003). [CrossRef] [PubMed]

,14

14. J. Ye, P. Van Dorpe, L. Lagae, G. Maes, and G. Borghs, “Observation of plasmonic dipolar anti-bonding mode in silver nanoring structures,” Nanotechnology 20(46), 465203 (2009). [CrossRef] [PubMed]

]. Significantly, the bonding mode is beneficial to some applications since it exhibits enormous field enhancement around NR because of the symmetric charge distribution which can be regarded as a strong dipolar mode [15

15. J. Aizpurua, P. Hanarp, D. S. Sutherland, M. Käll, G. W. Bryant, and F. J. García de Abajo, “Optical properties of gold nanorings,” Phys. Rev. Lett. 90(5), 057401 (2003). [CrossRef] [PubMed]

]. Moreover, for such elongated structure, the longitudinal plasmon resonance provides strong near-field around the two extremities due to the lightning-rod effect [16

16. M. B. Mohamed, V. Volkov, S. Link, and M. A. El-Sayed, “The ‘lightning’ gold nanorods: fluorescence enhancement of over a million compared to the gold metal,” Chem. Phys. Lett. 317(6), 517–523 (2000). [CrossRef]

] and its intensity can be further enhanced by increasing the aspect ratio [17

17. J. Zuloaga, E. Prodan, and P. Nordlander, “Quantum plasmonics: optical properties and tunability of metallic nanorods,” ACS Nano 4(9), 5269–5276 (2010). [CrossRef] [PubMed]

]. These exceptional optical properties of gold ENR are expected to be exploitable for surface-enhanced Raman scattering (SERS) and biosensing.

In this study, we report the experimental and simulation results for the plasmonic properties of bonding mode in gold ENR arrays with different aspect ratios under both longitudinal and transverse polarizations. In addition, the aspect ratio effect on electric field intensity enhancement especially for the inner and outer surfaces of gold ENR is investigated. For biosensing, compared with the transverse bonding mode, we find that the longitudinal bonding mode shows the larger wavelength shift for gold ENR with the higher aspect ratio when applied to very local changes of refractive index as induced by the presence of few molecules. These results are important for the design of nanostructure-based LSPR biosensors for detecting biological interactions, such as antibody-antigen, biotin-streptavidin, and toxin-receptor interactions.

2. Device fabrication and characterization

The scheme of a square lattice gold ENR array with average ring width w, long-axis length lx, short-axis length ly, thickness t, periods along the long-axis direction px, and along the short-axis direction py is shown in Fig. 1(a)
Fig. 1 (a) Geometric depiction of gold ENRs arranged in a square array on an ITO glass substrate. (b) SEM picture of a fabricated gold ENR array with w = 150 nm, lx = 870 nm, ly = 550 nm, t = 50 nm, px = 2 μm, and py = 1 μm.
. The aspect ratio (R) is defined as the length of long-axis lx divided by that of short-axis ly. In our fabrication, gold ENR arrays were manufactured on commercial indium tin oxide (ITO) glass since conducting substrate can minimize charge accumulation during electron beam lithography (EBL). First, a 150 nm polymethylmethacrylate (PMMA) layer was spin-coated onto the ITO glass. Then the ENR patterns with dimensions of 150 × 150 μm2 and different aspect ratios were defined on the PMMA layer by EBL. After developing, the substrate was coated with a 50 nm gold thin film through thermal evaporation followed by a lift-off process. The thickness t, average ring width w, short-axis length ly, periods px and py of fabricated gold ENR arrays are fixed at 50, 150, 550, 2000, and 1000 nm. Figure 1(b) shows a top-view scanning electron microscope (SEM) image of a fabricated gold ENR array with the aspect ratio R of 1.58.

Optical extinction measurements were performed using upright transmission spectroscopy. Collimated white light from a stabilized halogen lamp passed through a polarizer and was focused on the sample by an objective lens (NA = 0.4) at normal incidence.

3. Biosensing properties

4. Summary

In summary, we studied the optical behavior and biosensing of gold ENR arrays with different aspect ratios. For the plasmonic properties, the bonding mode in gold ENR array shows apparent redshifts as increasing the aspect ratio under both polarizations. Furthermore, the disc- and hole-like optical properties of gold ENR for longitudinal and transverse polarizations are found, which exhibit stronger field intensity enhancements at the outer and inner gold ENR surfaces respectively. For biosensing performance of BSA binding, the surface sensitivity of bonding mode as a function of aspect ratio is investigated. The peak wavelength shifts of longitudinal and transverse bonding modes increase when enlarging the aspect ratio and we observe the maximum total wavelength shift of 35 nm of longitudinal bonding mode in gold ENR array with R = 1.58. This high surface sensitivity suggests that gold ENRs can serve as potential ultrasensitive biosensing elements for probing molecular interactions.

Acknowledgments

This work is supported by Taiwan’s National Science Council (NSC) under Contract Nos. NSC-101-2221-E-009-054-MY2 and NSC-100-2221-E-009-109-MY3. The authors would like to thank the help from Center for Nano Science and Technology (CNST) at National Chiao Tung University (NCTU), Taiwan.

References and links

1.

J. N. Anker, W. P. Hall, O. Lyandres, N. C. Shah, J. Zhao, and R. P. Van Duyne, “Biosensing with plasmonic nanosensors,” Nat. Mater. 7(6), 442–453 (2008). [CrossRef] [PubMed]

2.

K. M. Mayer and J. H. Hafner, “Localized surface plasmon resonance sensors,” Chem. Rev. 111(6), 3828–3857 (2011). [CrossRef] [PubMed]

3.

S. A. Maier, P. G. Kik, H. A. Atwater, S. Meltzer, E. Harel, B. E. Koel, and A. A. G. Requicha, “Local detection of electromagnetic energy transport below the diffraction limit in metal nanoparticle plasmon waveguides,” Nat. Mater. 2(4), 229–232 (2003). [CrossRef] [PubMed]

4.

N. Fang, H. Lee, C. Sun, and X. Zhang, “Sub-diffraction-limited optical imaging with a silver superlens,” Science 308(5721), 534–537 (2005). [CrossRef] [PubMed]

5.

Y. Tanaka and K. Sasaki, “Efficient optical trapping using small arrays of plasmonic nanoblock pairs,” Appl. Phys. Lett. 100(2), 021102 (2012). [CrossRef]

6.

E. Hao and G. C. Schatz, “Electromagnetic fields around silver nanoparticles and dimers,” J. Chem. Phys. 120(1), 357–366 (2004). [CrossRef] [PubMed]

7.

A. M. Kern and O. J. F. Martin, “Excitation and reemission of molecules near realistic plasmonic nanostructures,” Nano Lett. 11(2), 482–487 (2011). [CrossRef] [PubMed]

8.

G. Gantzounis, N. Stefanou, and N. Papanikolaou, “Optical properties of periodic structures of metallic nanodisks,” Phys. Rev. B 77(3), 035101 (2008). [CrossRef]

9.

M. Rang, A. C. Jones, F. Zhou, Z. Y. Li, B. J. Wiley, Y. Xia, and M. B. Raschke, “Optical near-field mapping of plasmonic nanoprisms,” Nano Lett. 8(10), 3357–3363 (2008). [CrossRef] [PubMed]

10.

S. Zhang, K. Bao, N. J. Halas, H. Xu, and P. Nordlander, “Substrate-induced Fano resonances of a plasmonic nanocube: a route to increased-sensitivity localized surface plasmon resonance sensors revealed,” Nano Lett. 11(4), 1657–1663 (2011). [CrossRef] [PubMed]

11.

M. Zhang, X. Zhou, and Y. Fu, “Plasmonic resonance excited extinction spectra of cross-shaped Ag nanoparticles,” Plasmonics 5(4), 355–361 (2010). [CrossRef]

12.

P. Y. Chung, T. H. Lin, G. Schultz, C. Batich, and P. Jiang, “Nanopyramid surface plasmon resonance sensors,” Appl. Phys. Lett. 96(26), 261108 (2010). [CrossRef] [PubMed]

13.

E. Prodan, C. Radloff, N. J. Halas, and P. Nordlander, “A hybridization model for the plasmon response of complex nanostructures,” Science 302(5644), 419–422 (2003). [CrossRef] [PubMed]

14.

J. Ye, P. Van Dorpe, L. Lagae, G. Maes, and G. Borghs, “Observation of plasmonic dipolar anti-bonding mode in silver nanoring structures,” Nanotechnology 20(46), 465203 (2009). [CrossRef] [PubMed]

15.

J. Aizpurua, P. Hanarp, D. S. Sutherland, M. Käll, G. W. Bryant, and F. J. García de Abajo, “Optical properties of gold nanorings,” Phys. Rev. Lett. 90(5), 057401 (2003). [CrossRef] [PubMed]

16.

M. B. Mohamed, V. Volkov, S. Link, and M. A. El-Sayed, “The ‘lightning’ gold nanorods: fluorescence enhancement of over a million compared to the gold metal,” Chem. Phys. Lett. 317(6), 517–523 (2000). [CrossRef]

17.

J. Zuloaga, E. Prodan, and P. Nordlander, “Quantum plasmonics: optical properties and tunability of metallic nanorods,” ACS Nano 4(9), 5269–5276 (2010). [CrossRef] [PubMed]

18.

C. Y. Tsai, S. P. Lu, J. W. Lin, and P. T. Lee, “High sensitivity plasmonic index sensor using slablike gold nanoring arrays,” Appl. Phys. Lett. 98(15), 153108 (2011). [CrossRef] [PubMed]

19.

H. Wei, A. Reyes-Coronado, P. Nordlander, J. Aizpurua, and H. Xu, “Multipolar plasmon resonances in individual Ag nanorice,” ACS Nano 4(5), 2649–2654 (2010). [CrossRef] [PubMed]

20.

A. D. Rakic, A. B. Djurišic, J. M. Elazar, and M. L. Majewski, “Optical properties of metallic films for vertical-cavity optoelectronic devices,” Appl. Opt. 37(22), 5271–5283 (1998). [CrossRef] [PubMed]

21.

R. A. Synowicki, “Spectroscopic ellipsometry characterization of indium tin oxide film microstructure and optical constants,” Thin Solid Films 313–314, 394–397 (1998). [CrossRef]

22.

F. Neubrech, A. Garcia-Etxarri, D. Weber, J. Bochterle, H. Shen, M. Lamy de la Chapelle, G. W. Bryant, J. Aizpurua, and A. Pucci, “Defect-induced activation of symmetry forbidden infrared resonances in individual metallic nanorods,” Appl. Phys. Lett. 96(21), 213111 (2010). [CrossRef]

23.

N. Félidj, G. Laurent, J. Aubard, G. Lévi, A. Hohenau, J. R. Krenn, and F. R. Aussenegg, “Grating-induced plasmon mode in gold nanoparticle arrays,” J. Chem. Phys. 123(22), 221103 (2005). [CrossRef] [PubMed]

24.

H. Wang, D. W. Brandl, F. Le, P. Nordlander, and N. J. Halas, “Nanorice: a hybrid plasmonic nanostructure,” Nano Lett. 6(4), 827–832 (2006). [CrossRef] [PubMed]

25.

A. G. Brolo, R. Gordon, B. Leathem, and K. L. Kavanagh, “Surface plasmon sensor based on the enhanced light transmission through arrays of nanoholes in gold films,” Langmuir 20(12), 4813–4815 (2004). [CrossRef] [PubMed]

OCIS Codes
(240.6680) Optics at surfaces : Surface plasmons
(280.4788) Remote sensing and sensors : Optical sensing and sensors

ToC Category:
Optics at Surfaces

History
Original Manuscript: March 29, 2013
Revised Manuscript: May 16, 2013
Manuscript Accepted: May 28, 2013
Published: June 5, 2013

Virtual Issues
Vol. 8, Iss. 7 Virtual Journal for Biomedical Optics

Citation
Chia-Yang Tsai, Kai-Hao Chang, Che-Yao Wu, and Po-Tsung Lee, "The aspect ratio effect on plasmonic properties and biosensing of bonding mode in gold elliptical nanoring arrays," Opt. Express 21, 14090-14096 (2013)
http://www.opticsinfobase.org/vjbo/abstract.cfm?URI=oe-21-12-14090


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References

  1. J. N. Anker, W. P. Hall, O. Lyandres, N. C. Shah, J. Zhao, and R. P. Van Duyne, “Biosensing with plasmonic nanosensors,” Nat. Mater.7(6), 442–453 (2008). [CrossRef] [PubMed]
  2. K. M. Mayer and J. H. Hafner, “Localized surface plasmon resonance sensors,” Chem. Rev.111(6), 3828–3857 (2011). [CrossRef] [PubMed]
  3. S. A. Maier, P. G. Kik, H. A. Atwater, S. Meltzer, E. Harel, B. E. Koel, and A. A. G. Requicha, “Local detection of electromagnetic energy transport below the diffraction limit in metal nanoparticle plasmon waveguides,” Nat. Mater.2(4), 229–232 (2003). [CrossRef] [PubMed]
  4. N. Fang, H. Lee, C. Sun, and X. Zhang, “Sub-diffraction-limited optical imaging with a silver superlens,” Science308(5721), 534–537 (2005). [CrossRef] [PubMed]
  5. Y. Tanaka and K. Sasaki, “Efficient optical trapping using small arrays of plasmonic nanoblock pairs,” Appl. Phys. Lett.100(2), 021102 (2012). [CrossRef]
  6. E. Hao and G. C. Schatz, “Electromagnetic fields around silver nanoparticles and dimers,” J. Chem. Phys.120(1), 357–366 (2004). [CrossRef] [PubMed]
  7. A. M. Kern and O. J. F. Martin, “Excitation and reemission of molecules near realistic plasmonic nanostructures,” Nano Lett.11(2), 482–487 (2011). [CrossRef] [PubMed]
  8. G. Gantzounis, N. Stefanou, and N. Papanikolaou, “Optical properties of periodic structures of metallic nanodisks,” Phys. Rev. B77(3), 035101 (2008). [CrossRef]
  9. M. Rang, A. C. Jones, F. Zhou, Z. Y. Li, B. J. Wiley, Y. Xia, and M. B. Raschke, “Optical near-field mapping of plasmonic nanoprisms,” Nano Lett.8(10), 3357–3363 (2008). [CrossRef] [PubMed]
  10. S. Zhang, K. Bao, N. J. Halas, H. Xu, and P. Nordlander, “Substrate-induced Fano resonances of a plasmonic nanocube: a route to increased-sensitivity localized surface plasmon resonance sensors revealed,” Nano Lett.11(4), 1657–1663 (2011). [CrossRef] [PubMed]
  11. M. Zhang, X. Zhou, and Y. Fu, “Plasmonic resonance excited extinction spectra of cross-shaped Ag nanoparticles,” Plasmonics5(4), 355–361 (2010). [CrossRef]
  12. P. Y. Chung, T. H. Lin, G. Schultz, C. Batich, and P. Jiang, “Nanopyramid surface plasmon resonance sensors,” Appl. Phys. Lett.96(26), 261108 (2010). [CrossRef] [PubMed]
  13. E. Prodan, C. Radloff, N. J. Halas, and P. Nordlander, “A hybridization model for the plasmon response of complex nanostructures,” Science302(5644), 419–422 (2003). [CrossRef] [PubMed]
  14. J. Ye, P. Van Dorpe, L. Lagae, G. Maes, and G. Borghs, “Observation of plasmonic dipolar anti-bonding mode in silver nanoring structures,” Nanotechnology20(46), 465203 (2009). [CrossRef] [PubMed]
  15. J. Aizpurua, P. Hanarp, D. S. Sutherland, M. Käll, G. W. Bryant, and F. J. García de Abajo, “Optical properties of gold nanorings,” Phys. Rev. Lett.90(5), 057401 (2003). [CrossRef] [PubMed]
  16. M. B. Mohamed, V. Volkov, S. Link, and M. A. El-Sayed, “The ‘lightning’ gold nanorods: fluorescence enhancement of over a million compared to the gold metal,” Chem. Phys. Lett.317(6), 517–523 (2000). [CrossRef]
  17. J. Zuloaga, E. Prodan, and P. Nordlander, “Quantum plasmonics: optical properties and tunability of metallic nanorods,” ACS Nano4(9), 5269–5276 (2010). [CrossRef] [PubMed]
  18. C. Y. Tsai, S. P. Lu, J. W. Lin, and P. T. Lee, “High sensitivity plasmonic index sensor using slablike gold nanoring arrays,” Appl. Phys. Lett.98(15), 153108 (2011). [CrossRef] [PubMed]
  19. H. Wei, A. Reyes-Coronado, P. Nordlander, J. Aizpurua, and H. Xu, “Multipolar plasmon resonances in individual Ag nanorice,” ACS Nano4(5), 2649–2654 (2010). [CrossRef] [PubMed]
  20. A. D. Rakic, A. B. Djurišic, J. M. Elazar, and M. L. Majewski, “Optical properties of metallic films for vertical-cavity optoelectronic devices,” Appl. Opt.37(22), 5271–5283 (1998). [CrossRef] [PubMed]
  21. R. A. Synowicki, “Spectroscopic ellipsometry characterization of indium tin oxide film microstructure and optical constants,” Thin Solid Films313–314, 394–397 (1998). [CrossRef]
  22. F. Neubrech, A. Garcia-Etxarri, D. Weber, J. Bochterle, H. Shen, M. Lamy de la Chapelle, G. W. Bryant, J. Aizpurua, and A. Pucci, “Defect-induced activation of symmetry forbidden infrared resonances in individual metallic nanorods,” Appl. Phys. Lett.96(21), 213111 (2010). [CrossRef]
  23. N. Félidj, G. Laurent, J. Aubard, G. Lévi, A. Hohenau, J. R. Krenn, and F. R. Aussenegg, “Grating-induced plasmon mode in gold nanoparticle arrays,” J. Chem. Phys.123(22), 221103 (2005). [CrossRef] [PubMed]
  24. H. Wang, D. W. Brandl, F. Le, P. Nordlander, and N. J. Halas, “Nanorice: a hybrid plasmonic nanostructure,” Nano Lett.6(4), 827–832 (2006). [CrossRef] [PubMed]
  25. A. G. Brolo, R. Gordon, B. Leathem, and K. L. Kavanagh, “Surface plasmon sensor based on the enhanced light transmission through arrays of nanoholes in gold films,” Langmuir20(12), 4813–4815 (2004). [CrossRef] [PubMed]

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