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

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  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]

2012

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

2011

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]

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

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]

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]

2010

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]

M. Zhang, X. Zhou, and Y. Fu, “Plasmonic resonance excited extinction spectra of cross-shaped Ag nanoparticles,” Plasmonics5(4), 355–361 (2010).
[CrossRef]

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]

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]

J. Zuloaga, E. Prodan, and P. Nordlander, “Quantum plasmonics: optical properties and tunability of metallic nanorods,” ACS Nano4(9), 5269–5276 (2010).
[CrossRef] [PubMed]

2009

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]

2008

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]

G. Gantzounis, N. Stefanou, and N. Papanikolaou, “Optical properties of periodic structures of metallic nanodisks,” Phys. Rev. B77(3), 035101 (2008).
[CrossRef]

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]

2006

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]

2005

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]

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]

2004

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

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]

2003

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]

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]

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]

2000

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]

1998

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]

R. A. Synowicki, “Spectroscopic ellipsometry characterization of indium tin oxide film microstructure and optical constants,” Thin Solid Films313–314, 394–397 (1998).
[CrossRef]

Aizpurua, J.

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]

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]

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]

Anker, J. N.

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]

Atwater, H. A.

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]

Aubard, J.

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]

Aussenegg, F. R.

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]

Bao, K.

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]

Batich, C.

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]

Bochterle, J.

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]

Borghs, G.

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]

Brandl, D. W.

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]

Brolo, A. G.

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]

Bryant, G. W.

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]

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]

Chung, P. Y.

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]

Djurišic, A. B.

Elazar, J. M.

El-Sayed, M. A.

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]

Fang, N.

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]

Félidj, N.

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]

Fu, Y.

M. Zhang, X. Zhou, and Y. Fu, “Plasmonic resonance excited extinction spectra of cross-shaped Ag nanoparticles,” Plasmonics5(4), 355–361 (2010).
[CrossRef]

Gantzounis, G.

G. Gantzounis, N. Stefanou, and N. Papanikolaou, “Optical properties of periodic structures of metallic nanodisks,” Phys. Rev. B77(3), 035101 (2008).
[CrossRef]

García de Abajo, F. J.

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]

Garcia-Etxarri, A.

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]

Gordon, R.

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]

Hafner, J. H.

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

Halas, N. J.

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]

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]

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]

Hall, W. P.

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]

Hanarp, P.

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]

Hao, E.

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

Harel, E.

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]

Hohenau, A.

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]

Jiang, P.

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]

Jones, A. C.

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]

Käll, M.

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]

Kavanagh, K. L.

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]

Kern, A. M.

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]

Kik, P. G.

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]

Koel, B. E.

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]

Krenn, J. R.

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]

Lagae, L.

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]

Lamy de la Chapelle, M.

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]

Laurent, G.

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]

Le, F.

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]

Leathem, B.

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]

Lee, H.

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]

Lee, P. T.

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]

Lévi, G.

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]

Li, Z. Y.

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]

Lin, J. W.

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]

Lin, T. H.

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]

Link, S.

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]

Lu, S. P.

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]

Lyandres, O.

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]

Maes, G.

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]

Maier, S. A.

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]

Majewski, M. L.

Martin, O. J. F.

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]

Mayer, K. M.

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

Meltzer, S.

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]

Mohamed, M. B.

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]

Neubrech, F.

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]

Nordlander, P.

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]

J. Zuloaga, E. Prodan, and P. Nordlander, “Quantum plasmonics: optical properties and tunability of metallic nanorods,” ACS Nano4(9), 5269–5276 (2010).
[CrossRef] [PubMed]

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]

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]

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]

Papanikolaou, N.

G. Gantzounis, N. Stefanou, and N. Papanikolaou, “Optical properties of periodic structures of metallic nanodisks,” Phys. Rev. B77(3), 035101 (2008).
[CrossRef]

Prodan, E.

J. Zuloaga, E. Prodan, and P. Nordlander, “Quantum plasmonics: optical properties and tunability of metallic nanorods,” ACS Nano4(9), 5269–5276 (2010).
[CrossRef] [PubMed]

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]

Pucci, A.

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]

Radloff, C.

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]

Rakic, A. D.

Rang, M.

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]

Raschke, M. B.

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]

Requicha, A. A. G.

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]

Reyes-Coronado, A.

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]

Sasaki, K.

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

Schatz, G. C.

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

Schultz, G.

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]

Shah, N. C.

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]

Shen, H.

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]

Stefanou, N.

G. Gantzounis, N. Stefanou, and N. Papanikolaou, “Optical properties of periodic structures of metallic nanodisks,” Phys. Rev. B77(3), 035101 (2008).
[CrossRef]

Sun, C.

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]

Sutherland, D. S.

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]

Synowicki, R. A.

R. A. Synowicki, “Spectroscopic ellipsometry characterization of indium tin oxide film microstructure and optical constants,” Thin Solid Films313–314, 394–397 (1998).
[CrossRef]

Tanaka, Y.

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

Tsai, C. Y.

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]

Van Dorpe, P.

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]

Van Duyne, R. P.

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]

Volkov, V.

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]

Wang, H.

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]

Weber, D.

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]

Wei, H.

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]

Wiley, B. J.

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]

Xia, Y.

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]

Xu, H.

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]

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]

Ye, J.

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]

Zhang, M.

M. Zhang, X. Zhou, and Y. Fu, “Plasmonic resonance excited extinction spectra of cross-shaped Ag nanoparticles,” Plasmonics5(4), 355–361 (2010).
[CrossRef]

Zhang, S.

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]

Zhang, X.

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]

Zhao, J.

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]

Zhou, F.

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]

Zhou, X.

M. Zhang, X. Zhou, and Y. Fu, “Plasmonic resonance excited extinction spectra of cross-shaped Ag nanoparticles,” Plasmonics5(4), 355–361 (2010).
[CrossRef]

Zuloaga, J.

J. Zuloaga, E. Prodan, and P. Nordlander, “Quantum plasmonics: optical properties and tunability of metallic nanorods,” ACS Nano4(9), 5269–5276 (2010).
[CrossRef] [PubMed]

ACS Nano

J. Zuloaga, E. Prodan, and P. Nordlander, “Quantum plasmonics: optical properties and tunability of metallic nanorods,” ACS Nano4(9), 5269–5276 (2010).
[CrossRef] [PubMed]

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]

Appl. Opt.

Appl. Phys. Lett.

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]

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]

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]

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

Chem. Phys. Lett.

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]

Chem. Rev.

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

J. Chem. Phys.

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

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]

Langmuir

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]

Nano Lett.

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]

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]

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]

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]

Nanotechnology

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]

Nat. Mater.

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]

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]

Phys. Rev. B

G. Gantzounis, N. Stefanou, and N. Papanikolaou, “Optical properties of periodic structures of metallic nanodisks,” Phys. Rev. B77(3), 035101 (2008).
[CrossRef]

Phys. Rev. Lett.

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]

Plasmonics

M. Zhang, X. Zhou, and Y. Fu, “Plasmonic resonance excited extinction spectra of cross-shaped Ag nanoparticles,” Plasmonics5(4), 355–361 (2010).
[CrossRef]

Science

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]

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]

Thin Solid Films

R. A. Synowicki, “Spectroscopic ellipsometry characterization of indium tin oxide film microstructure and optical constants,” Thin Solid Films313–314, 394–397 (1998).
[CrossRef]

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Figures (5)

Fig. 1
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.

Fig. 2
Fig. 2

(a) SEM images of gold ENRs with different aspect ratios within a range of 0.95−1.58. (b) Measured extinction spectra of gold ENR arrays with varied aspect ratio under longitudinal (top) and transverse polarizations (bottom).

Fig. 3
Fig. 3

Optical spectra of different nanostructures including gold ENH, END, and ENR with varied aspect ratio under (a) longitudinal and (b) transverse polarizations. Red arrows indicate that gold ENR exhibits disk- or hole-like optical properties under longitudinal or transverse polarization.

Fig. 4
Fig. 4

(a) Near-field intensity enhancement mapped on the top surface of gold ENR with the aspect ratio of 1.58 under longitudinal (left) and transverse (right) polarizations. (b) The field intensity enhancement at the inner and outer surfaces (denoted by the Pinner and Pouter) of gold ENR as a function of aspect ratio under different polarizations.

Fig. 5
Fig. 5

(a) Illustration of experimental procedure for biosensing including surface modification of gold ENR and BSA protein binding. (b) Normalized extinction spectra of longitudinal bonding mode in gold ENR array with R = 1.58 for each step of biosensing experiment. (c) Total LSPR wavelength shifts of longitudinal and transverse bonding modes induced by MUA modification and BSA binding as a function of aspect ratio of gold ENR.

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