OSA's Digital Library

Virtual Journal for Biomedical Optics

Virtual Journal for Biomedical Optics

| EXPLORING THE INTERFACE OF LIGHT AND BIOMEDICINE

  • Editor: Gregory W. Faris
  • Vol. 4, Iss. 10 — Oct. 2, 2009
« Show journal navigation

Revealing the spatial distribution of the site enhancement for the surface enhanced Raman scattering on the regular nanoparticle arrays

Fan-Ching Chien, Wen Yen Huang, Jau-Ye Shiu, Chiung Wen Kuo, and Peilin Chen  »View Author Affiliations


Optics Express, Vol. 17, Issue 16, pp. 13974-13981 (2009)
http://dx.doi.org/10.1364/OE.17.013974


View Full Text Article

Acrobat PDF (2235 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

The spatial distribution of the site enhancement for the surface-enhanced Raman scattering (SERS) on the regular nanoparticle arrays has been investigated by the confocal Raman microscopy. It was found that the spatial distribution of the Raman signals on the well-ordered nanoparticle arrays was very inhomogeneous and concentrated on the defects of the nanoparticle arrays. The SERS signals were also observed to depend on the thickness of silver film and the defect density. It has been demonstrated that the number of SERS active sites can be increased ten folds by trimming the size of nanoparticles using oxygen plasma.

© 2009 OSA

1. Introduction

The plasmonic-enhanced metallic nanostructured substrates, which are capable of inducing localized surface plasmons (LSPs), have drawn a lot research attentions lately, because of their potential applications in optoelectronic devices, plasmonic crystals, nanolithography, subwavelength imaging and biomolecular detection [1–5

1. E. Ozbay, “Plasmonics: merging photonics and electronics at nanoscale dimensions,” Science 311(5758), 189–193 (2006). [CrossRef] [PubMed]

]. Through various lithographic or synthetic approaches, the size, the shape, the compositions and the inter-particle spacing of the metallic nanostructures could be engineered to specifically enhance a local electromagnetic (EM) field of LSPs allowing ultra-sensitive detection [4–6

4. 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]

]. Among the LSP based chemical- and bio-sensing techniques, the surface enhanced Raman scattering (SERS) has long been used to investigate the structural information of molecules adsorbed on the surfaces [7–9

7. T. Vo-Dinh, “Surface-enhanced Raman spectroscopy using metallic nanostructures,” Trends Analyt. Chem. 17(8–9), 557–582 (1998). [CrossRef]

]. However, the cross section of Raman scattering is extremely small (typically about 10-28 - 10-30 cm2/molecule). Only those molecules adsorbed on the noble metals, such as gold and silver, are enhanced both electromagnetically and chemically to produce reasonable Raman signal for analytically purpose [5

5. M. E. Stewart, C. R. Anderton, L. B. Thompson, J. Maria, S. K. Gray, J. A. Rogers, and R. G. Nuzzo, “Nanostructured plasmonic sensors,” Chem. Rev. 108(2), 494–521 (2008). [CrossRef] [PubMed]

, 10

10. Z. Q. Tian, B. Ren, and D. Y. Wu, “Surface-enhanced Raman scattering: from noble to transition metals and from rough surfaces to ordered nanostructures,” J. Phys. Chem. B 106(37), 9463–9483 (2002). [CrossRef]

]. SERS technique was not used in the ultra-sensitive detection until the discovery of the unusual large Raman cross sections for the molecules adsorbed on the aggregates of nanoparticles [11

11. S. Nie and S. R. Emory, “Probing single molecules and single nanoparticles by surface-enhanced Raman scattering,” Science 275(5303), 1102–1106 (1997). [CrossRef] [PubMed]

, 12

12. K. Kneipp, Y. Wang, H. Kneipp, L. T. Perelman, I. Itzkan, R. R. Dasari, and M. S. Feld, “Single molecule detection using surface-enhanced Raman scattering (SERS),” Phys. Rev. Lett. 78(9), 1667–1670 (1997). [CrossRef]

]. It has been claimed that the cross section of Raman scattering could be enhanced up to 1014 on the so-called “hot-spots”. Later studies have suggested that the molecules in the junctions between nanoparticles, whose separation was about 1 nm, could exhibit unusual large Raman cross section allowing single molecular detection through the excitation of LSPs [13

13. A. M. Michaels, J. Jiang, and L. E. Brus, “Ag nanocrystal junctions as the site for surface-enhanced Raman scattering of single rhodamine 6G molecules,” J. Phys. Chem. B 104(50), 11965–11971 (2000). [CrossRef]

]. Since the discovery of the single molecule SERS (SM-SERS), a lot of research efforts have been focused on the development of ultra-sensitive chemical- and bio-sensors based on such “hot-spots” concept [5

5. M. E. Stewart, C. R. Anderton, L. B. Thompson, J. Maria, S. K. Gray, J. A. Rogers, and R. G. Nuzzo, “Nanostructured plasmonic sensors,” Chem. Rev. 108(2), 494–521 (2008). [CrossRef] [PubMed]

, 9

9. K. Kneipp, H. Kneipp, and J. Kneipp, “Surface-enhanced Raman scattering in local optical fields of silver and gold nanoaggregates-from single-molecule Raman spectroscopy to ultrasensitive probing in live cells,” Acc. Chem. Res. 39(7), 443–450 (2006). [CrossRef] [PubMed]

, 14

14. M. J. Banholzer, J. E. Millstone, L. Qin, and C. A. Mirkin, “Rationally designed nanostructures for surface-enhanced Raman spectroscopy,” Chem. Soc. Rev. 37(5), 885–897 (2008). [CrossRef] [PubMed]

]. However, such “hot-spots” are rare in the SERS substrates, because the field enhancement is very sensitive to the relative position of the molecules in the “hot-spots” [15

15. N. P. W. Pieczonka and R. F. Aroca, “Single molecule analysis by surfaced-enhanced Raman scattering,” Chem. Soc. Rev. 37(5), 946–954 (2008). [CrossRef] [PubMed]

], which makes it very difficult to fabricate a reproducible SERS substrate for ultra-sensitive detection.

In the past few years, many lithographic approaches have been utilized to fabricate periodic particle array to obtain reproducible SERS active substrates with optimal SERS signal [5

5. M. E. Stewart, C. R. Anderton, L. B. Thompson, J. Maria, S. K. Gray, J. A. Rogers, and R. G. Nuzzo, “Nanostructured plasmonic sensors,” Chem. Rev. 108(2), 494–521 (2008). [CrossRef] [PubMed]

, 16

16. J. J. Baumberg, T. A. Kelf, Y. Sugawara, S. Cintra, M. E. Abdelsalam, P. N. Bartlett, and A. E. Russell, “Angle-resolved surface-enhanced Raman scattering on metallic nanostructured plasmonic crystals,” Nano Lett. 5(11), 2262–2267 (2005). [CrossRef] [PubMed]

, 17

17. N. Felidj, J. Aubard, G. Levi, J. R. Krenn, A. Hohenau, G. Schider, A. Leitner, and F. R. Aussenegg, “Optimized surface-enhanced Raman scattering on gold nanoparticle arrays,” Appl. Phys. Lett. 82(18), 3095–3097 (2003). [CrossRef]

]. Among these techniques, nanosphere lithography developed by Van Duyne et al [18

18. L. A. Dick, A. D. McFarland, C. L. Haynes, and R. P. Van Duyne, “Metal film over nanosphere (MFON) electrodes for surface-enhanced Raman spectroscopy (SERS): improvements in surface nanostructure stability and suppression of irreversible loss,” J. Phys. Chem. B 106(4), 853–860 (2002). [CrossRef]

] has been very successful in preparing reliable SERS active substrates. It has been demonstrated that the silver film over nanosphere (AgFON) substrates were capable of providing reproducible Raman signal allowing rapid detection of glucose and anthrax [19

19. X. Zhang, M. A. Young, O. Lyandres, and R. P. Van Duyne, “Rapid detection of an anthrax biomarker by surface-enhanced Raman spectroscopy,” J. Am. Chem. Soc. 127(12), 4484–4489 (2005). [CrossRef] [PubMed]

, 20

20. C. R. Yonzon, C. L. Haynes, X. Zhang, J. T. Walsh, and R. P. Van Duyne, “Glucose sensing using near-infrared surface-enhanced Raman spectroscopy: gold surfaces, 10-Day stability, and improved accuracy,” Anal. Chem. 76, 78–85 (2004). [CrossRef]

]. However, in a recent photochemical hole burning (PHB) study, it was reported that the site enhancement distribution for benzenethiol molecules on the AgFON substrates was highly inhomogeneous [21

21. Y. Fang, N.-H. Seong, and D. D. Dlott, “Measurement of the distribution of site enhancements in surface-enhanced Raman scattering,” Science 321(5887), 388–392 (2008). [CrossRef] [PubMed]

]. It was observed that only a small fraction (63 ppm) of molecules on the surfaces contributed to 24% of the overall SERS signals. It is counterintuitive to imagine that the distribution of the site enhancement on such type of regular nanostructures could be so inhomogeneous while providing reproducible SERS signal. Where are the locations of the “hot-spots” in the regular nanoparticle arrays? Can we increase the number of the “hot spots” in the regular nanoparticle arrays? The answers to these questions may lead us to design an optimal SERS substrate, which can produce strong and reliable SERS signal for ultrasensitive detection. To explore these questions, it requires the investigation of the spatial distribution of these “hot spots” and the topographic information around them. So far, the best spatially resolved Raman images were obtained by tip-enhanced Raman scatting, which has been demonstrated capable of measuring single molecular Raman scattering with 10 nanometer resolution [22

22. E. Bailo and V. Deckert, “Tip-enhanced Raman scattering,” Chem. Soc. Rev. 37(5), 921–930 (2008). [CrossRef] [PubMed]

]. However, the presence of the tip induces additional enhancement contribution, which may distort the enhancement site distribution on the nanostructured surfaces. An alternative approach to reveal the spatial distribution of Raman signal is the confocal Raman microscopy (CRM), which is capable of mapping the Raman signal with sub-wavelength spatial resolution. When the CRM is combined with high resolution microscopic tools such as atomic force microscopy (AFM) or scanning electron microscopy (SEM), both optical and topographic information of the nanostructured samples can be obtained on the same area. In this article, we report the investigation of the spatial distribution of the SERS site enhancement on the AgFON substrates by a combination of CRM, AFM and SEM, and the design of an optimal SERS substrate for rapid chemical and bio-sensing.

2. Experimental section

To measure the spatial distribution of the site enhancement on the AgFON substrates, the AgFON substrates were prepared following the procedure described previously [18

18. L. A. Dick, A. D. McFarland, C. L. Haynes, and R. P. Van Duyne, “Metal film over nanosphere (MFON) electrodes for surface-enhanced Raman spectroscopy (SERS): improvements in surface nanostructure stability and suppression of irreversible loss,” J. Phys. Chem. B 106(4), 853–860 (2002). [CrossRef]

]. In short, monolayers of 300 nm close packed polystyrene nanoparticles (Bang’s Lab) coated with 150 nm thin silver film were used in this experiment. A combined CRM and AFM (alpha 300, WITec Instruments Corp., Germany) was used to record the SERS images and the topographic images of the AgFON substrates. The wavelength of the excitation laser (Ar+ laser, Melles Griot, U.S.) was 488 nm and the laser power was around 19 μW. A 100X objective (Nikon) with a numerical aperture of 0.9 was used to focus the laser beam into a 0.4 μm spot and the Raman signal was collected through a 25 μm fiber. To eliminate the complication in measuring the enhancement factor, a monolayer of benzenethiol (Aldrich), which is known to exhibit minimum chemical and resonance enhancement at the laser wavelength [21

21. Y. Fang, N.-H. Seong, and D. D. Dlott, “Measurement of the distribution of site enhancements in surface-enhanced Raman scattering,” Science 321(5887), 388–392 (2008). [CrossRef] [PubMed]

], was prepared by dipping the AgFON substrates into 10-4 M benzenethiol ethanol solution for 4 hours. To compare the Raman spectra, the intensity of Raman signals from different samples were normalized to 0.2 s, which was used in the Raman imaging experiment.

3. Results and discussion

Fig. 1. (a) Raman spectra of benzenethiol molecules from neat liquid and AgFON surface. Black spectrum is the Raman spectrum from neat benzenethiol liquid. Exposure time 100 s. Red line is an averaged Raman spectrum on the AgFON substrate over 10 × 10 μm area (150×150 pixel). Exposure time: 0.2 s. A typical Raman spectrum on the hot site with an enchantment factor of 108 is depicted in blue line. Exposure time 0.2 s. (b) SERS image of the 1575 cm-1 peak for benzenthiol from the 300 nm AgFON substrate. Bar: 2 μm. (c) AFM image of the AgFON substrate. Bar: 2 μm. (d) Distribution of the measured SERS enhancement factor log(∣E∣4).

The contribution to the overall SERS intensity from various sites is listed in Table 1. As we can see from the Table 1, the maximum measured enhancement was around 2 × 109, which was one order of magnitude less than those measured in PHB measurement (4 × 1010) [21

21. Y. Fang, N.-H. Seong, and D. D. Dlott, “Measurement of the distribution of site enhancements in surface-enhanced Raman scattering,” Science 321(5887), 388–392 (2008). [CrossRef] [PubMed]

]. The spatial distribution for the site enhancement was also very inhomogeneous where the hot-sites (with a enhancement factor larger than 108) only occupied less than 0.3% of the scanned area, however, they contributed to 27.5% of the overall SERS signal. One reasonable explanation for the lower maximum observed enhancement factor is that the population of such hot site is very rare. Therefore, the chance for finding such hot site in a 10 × 10 μm2 area is very low. Another reason for the lower enhancement factor at the hottest site may be due to normalization. Since the spatial resolution for our measurement was about 0.4 μm, we could not distinguish how many molecules contributed to the Raman signal within the detection spot. Therefore, an average number of 3 × 106 beneznethiol molecules in this area was used to calculate the enhancement factor. It is know that there are only a few molecules present in the hottest spot. If that is the case, the observed enhancement factors for the hottest sites could be several orders of magnitude larger than the number listed in Table 1.

Table 1. Distribution of the enhancement factors for benzenethiol molecules on the 300 nm AgFON substrate.

table-icon
View This Table

Fig. 2. (a), (c) Confocal Raman images of benzenethiol on the silver film over isolated nanospheres (460 nm) and a line of close-contacted nanospheres. (b), (d) SEM images of the nanosphere in the same area. Scale bar 500 nm in (a) and 1 μm in (b)(c)(d). (e), (f) Cross-sectional SEM image of silver film over nanospheres. Bar: 500 nm.
Fig. 3. The measured SERS intensity for the 1575 cm-1 peak on the 460 nm AgFON substrates as a function of film thickness.
Fig. 4. The calculated SERS enhancement distribution log(∣E∣4) around the nanosphere for different polarizations. (a) The simulated model of the single nanosphere. (b) TE mode. (c) TM mode and (d) Enlarged view of field at the edge.

Knowing that the SERS signals are concentrated on the edges of the nanoparticles where the nanoparticles are not in close contact, it should be possible to increase the SERS signal by producing non-contacted nanoparticle arrays. One simple approach to produce such type of nanoparticle arrays is to trim the contacting edge of polystyrene nanoparticles by oxygen plasma. It has been shown that such process can be used to produce size tunable nanopillar arrays [24

24. C. W. Kuo, K. H. Wei, C. H. Lin, J. Y. Shiu, and P. Chen, “Nanofluidic system for the studies of single DNA molecules,” Electrophoresis 29(14), 2931–2938 (2008). [PubMed]

]. Shown in Fig. 5 are the SERS and SEM images of the size trimmed nanoparticle arrays. The diameters of the polystyrene nanoparticles were reduced from 460 nm to 360 nm and 300 nm. These results clearly demonstrated that the area percentage of the SERS signal with enhancement factor larger than 106 can be increased from around 10% to about 90% of the overall area. When compared with the conventional 460 nm AgFON substrates, the SERS intensity on size trimmed nanoparticle array with optimal silver film thickness was improved by ten times. Our result indicates that it is possible to fabricate reproducible substrates with optimal SERS signal by controlling the silver film thickness and the defect density.

Fig. 5. (a), (c) The SERS images of the 1575 cm-1 peak for benzenethiol on the 300 nm and 360 nm size trimmed nanoparticle array substrates, respectively. (b), (d) the SEM images of the nanoparticle array substrates. Bar: 2 μm.

4. Conclusions

In summary, we have investigated the spatial distribution of the Raman site enhancement on the AgFON substrates. It was observed that the site enhancements were highly inhomogeneous on the AgFON substrates. When the SERS images were combined with AFM and SEM images, it was found that the hot sites were located on the defects between close packed nanoparticles. Further study revealed that the hot sites were formed in the gaps between the edges of the silver films over the nanoparticles and on the surrounding flat area. As a result of geometric consideration, the maximum Raman signal can be obtained by controlling the film thickness and the defect density. Our results clear demonstrate that it is necessary to investigate the spatial distribution of the Raman scattering and the topographic information on the nanostructured surfaces for fabricating reproducible SERS substrates with optimal signal.

Acknowledgments

This research was supported, in part, by National Science Council, Taiwan under contract 97-2628-M-001-010-MY3 and Academia Sinica Research Project on Nano Science and Technology.

References and links

1.

E. Ozbay, “Plasmonics: merging photonics and electronics at nanoscale dimensions,” Science 311(5758), 189–193 (2006). [CrossRef] [PubMed]

2.

X. Zhang and Z. Liu, “Superlenses to overcome the diffraction limit,” Nat. Mater. 7(6), 435–441 (2008). [CrossRef] [PubMed]

3.

S. Lal, S. Link, and N. J. Halas, “Nano-optics from sensing to waveguiding,” Nat. Photonics 1(11), 641–648 (2007). [CrossRef]

4.

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]

5.

M. E. Stewart, C. R. Anderton, L. B. Thompson, J. Maria, S. K. Gray, J. A. Rogers, and R. G. Nuzzo, “Nanostructured plasmonic sensors,” Chem. Rev. 108(2), 494–521 (2008). [CrossRef] [PubMed]

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.

T. Vo-Dinh, “Surface-enhanced Raman spectroscopy using metallic nanostructures,” Trends Analyt. Chem. 17(8–9), 557–582 (1998). [CrossRef]

8.

K. Kneipp, H. Kneipp, I. Itzkan, R. R. Dasari, and M. S. Feld, “Ultrasensitive chemical analysis by Raman spectroscopy,” Chem. Rev. 99(10), 2957–2976 (1999). [CrossRef]

9.

K. Kneipp, H. Kneipp, and J. Kneipp, “Surface-enhanced Raman scattering in local optical fields of silver and gold nanoaggregates-from single-molecule Raman spectroscopy to ultrasensitive probing in live cells,” Acc. Chem. Res. 39(7), 443–450 (2006). [CrossRef] [PubMed]

10.

Z. Q. Tian, B. Ren, and D. Y. Wu, “Surface-enhanced Raman scattering: from noble to transition metals and from rough surfaces to ordered nanostructures,” J. Phys. Chem. B 106(37), 9463–9483 (2002). [CrossRef]

11.

S. Nie and S. R. Emory, “Probing single molecules and single nanoparticles by surface-enhanced Raman scattering,” Science 275(5303), 1102–1106 (1997). [CrossRef] [PubMed]

12.

K. Kneipp, Y. Wang, H. Kneipp, L. T. Perelman, I. Itzkan, R. R. Dasari, and M. S. Feld, “Single molecule detection using surface-enhanced Raman scattering (SERS),” Phys. Rev. Lett. 78(9), 1667–1670 (1997). [CrossRef]

13.

A. M. Michaels, J. Jiang, and L. E. Brus, “Ag nanocrystal junctions as the site for surface-enhanced Raman scattering of single rhodamine 6G molecules,” J. Phys. Chem. B 104(50), 11965–11971 (2000). [CrossRef]

14.

M. J. Banholzer, J. E. Millstone, L. Qin, and C. A. Mirkin, “Rationally designed nanostructures for surface-enhanced Raman spectroscopy,” Chem. Soc. Rev. 37(5), 885–897 (2008). [CrossRef] [PubMed]

15.

N. P. W. Pieczonka and R. F. Aroca, “Single molecule analysis by surfaced-enhanced Raman scattering,” Chem. Soc. Rev. 37(5), 946–954 (2008). [CrossRef] [PubMed]

16.

J. J. Baumberg, T. A. Kelf, Y. Sugawara, S. Cintra, M. E. Abdelsalam, P. N. Bartlett, and A. E. Russell, “Angle-resolved surface-enhanced Raman scattering on metallic nanostructured plasmonic crystals,” Nano Lett. 5(11), 2262–2267 (2005). [CrossRef] [PubMed]

17.

N. Felidj, J. Aubard, G. Levi, J. R. Krenn, A. Hohenau, G. Schider, A. Leitner, and F. R. Aussenegg, “Optimized surface-enhanced Raman scattering on gold nanoparticle arrays,” Appl. Phys. Lett. 82(18), 3095–3097 (2003). [CrossRef]

18.

L. A. Dick, A. D. McFarland, C. L. Haynes, and R. P. Van Duyne, “Metal film over nanosphere (MFON) electrodes for surface-enhanced Raman spectroscopy (SERS): improvements in surface nanostructure stability and suppression of irreversible loss,” J. Phys. Chem. B 106(4), 853–860 (2002). [CrossRef]

19.

X. Zhang, M. A. Young, O. Lyandres, and R. P. Van Duyne, “Rapid detection of an anthrax biomarker by surface-enhanced Raman spectroscopy,” J. Am. Chem. Soc. 127(12), 4484–4489 (2005). [CrossRef] [PubMed]

20.

C. R. Yonzon, C. L. Haynes, X. Zhang, J. T. Walsh, and R. P. Van Duyne, “Glucose sensing using near-infrared surface-enhanced Raman spectroscopy: gold surfaces, 10-Day stability, and improved accuracy,” Anal. Chem. 76, 78–85 (2004). [CrossRef]

21.

Y. Fang, N.-H. Seong, and D. D. Dlott, “Measurement of the distribution of site enhancements in surface-enhanced Raman scattering,” Science 321(5887), 388–392 (2008). [CrossRef] [PubMed]

22.

E. Bailo and V. Deckert, “Tip-enhanced Raman scattering,” Chem. Soc. Rev. 37(5), 921–930 (2008). [CrossRef] [PubMed]

23.

A. D. McFarland, M. A. Young, J. A. Dieringer, and R. P. Van Duyne, “Wavelength-scanned surface-enhanced Raman excitation spectroscopy,” J. Phys. Chem. B 109(22), 11279–11285 (2005). [CrossRef]

24.

C. W. Kuo, K. H. Wei, C. H. Lin, J. Y. Shiu, and P. Chen, “Nanofluidic system for the studies of single DNA molecules,” Electrophoresis 29(14), 2931–2938 (2008). [PubMed]

OCIS Codes
(170.5660) Medical optics and biotechnology : Raman spectroscopy
(240.6680) Optics at surfaces : Surface plasmons
(180.5655) Microscopy : Raman microscopy
(240.6695) Optics at surfaces : Surface-enhanced Raman scattering

ToC Category:
Optics at Surfaces

History
Original Manuscript: June 2, 2009
Revised Manuscript: July 23, 2009
Manuscript Accepted: July 23, 2009
Published: August 3, 2009

Virtual Issues
Vol. 4, Iss. 10 Virtual Journal for Biomedical Optics

Citation
Fan-Ching Chien, Wen Yen Huang, Jau-Ye Shiu, Chiung Wen Kuo, and Peilin Chen, "Revealing the spatial distribution of the site enhancement for the surface enhanced Raman scattering on the regular nanoparticle arrays," Opt. Express 17, 13974-13981 (2009)
http://www.opticsinfobase.org/vjbo/abstract.cfm?URI=oe-17-16-13974


Sort:  Author  |  Year  |  Journal  |  Reset  

References

  1. E. Ozbay, “Plasmonics: merging photonics and electronics at nanoscale dimensions,” Science 311(5758), 189–193 (2006). [CrossRef] [PubMed]
  2. X. Zhang and Z. Liu, “Superlenses to overcome the diffraction limit,” Nat. Mater. 7(6), 435–441 (2008). [CrossRef] [PubMed]
  3. S. Lal, S. Link, and N. J. Halas, “Nano-optics from sensing to waveguiding,” Nat. Photonics 1(11), 641–648 (2007). [CrossRef]
  4. 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]
  5. M. E. Stewart, C. R. Anderton, L. B. Thompson, J. Maria, S. K. Gray, J. A. Rogers, and R. G. Nuzzo, “Nanostructured plasmonic sensors,” Chem. Rev. 108(2), 494–521 (2008). [CrossRef] [PubMed]
  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. T. Vo-Dinh, “Surface-enhanced Raman spectroscopy using metallic nanostructures,” Trends Analyt. Chem. 17(8-9), 557–582 (1998). [CrossRef]
  8. K. Kneipp, H. Kneipp, I. Itzkan, R. R. Dasari, and M. S. Feld, “Ultrasensitive chemical analysis by Raman spectroscopy,” Chem. Rev. 99(10), 2957–2976 (1999). [CrossRef]
  9. K. Kneipp, H. Kneipp, and J. Kneipp, “Surface-enhanced Raman scattering in local optical fields of silver and gold nanoaggregates-from single-molecule Raman spectroscopy to ultrasensitive probing in live cells,” Acc. Chem. Res. 39(7), 443–450 (2006). [CrossRef] [PubMed]
  10. Z. Q. Tian, B. Ren, and D. Y. Wu, “Surface-enhanced Raman scattering: from noble to transition metals and from rough surfaces to ordered nanostructures,” J. Phys. Chem. B 106(37), 9463–9483 (2002). [CrossRef]
  11. S. Nie and S. R. Emory, “Probing single molecules and single nanoparticles by surface-enhanced Raman scattering,” Science 275(5303), 1102–1106 (1997). [CrossRef] [PubMed]
  12. K. Kneipp, Y. Wang, H. Kneipp, L. T. Perelman, I. Itzkan, R. R. Dasari, and M. S. Feld, “Single molecule detection using surface-enhanced Raman scattering (SERS),” Phys. Rev. Lett. 78(9), 1667–1670 (1997). [CrossRef]
  13. A. M. Michaels, J. Jiang, and L. E. Brus, “Ag nanocrystal junctions as the site for surface-enhanced Raman scattering of single rhodamine 6G molecules,” J. Phys. Chem. B 104(50), 11965–11971 (2000). [CrossRef]
  14. M. J. Banholzer, J. E. Millstone, L. Qin, and C. A. Mirkin, “Rationally designed nanostructures for surface-enhanced Raman spectroscopy,” Chem. Soc. Rev. 37(5), 885–897 (2008). [CrossRef] [PubMed]
  15. N. P. W. Pieczonka and R. F. Aroca, “Single molecule analysis by surfaced-enhanced Raman scattering,” Chem. Soc. Rev. 37(5), 946–954 (2008). [CrossRef] [PubMed]
  16. J. J. Baumberg, T. A. Kelf, Y. Sugawara, S. Cintra, M. E. Abdelsalam, P. N. Bartlett, and A. E. Russell, “Angle-resolved surface-enhanced Raman scattering on metallic nanostructured plasmonic crystals,” Nano Lett. 5(11), 2262–2267 (2005). [CrossRef] [PubMed]
  17. N. Felidj, J. Aubard, G. Levi, J. R. Krenn, A. Hohenau, G. Schider, A. Leitner, and F. R. Aussenegg, “Optimized surface-enhanced Raman scattering on gold nanoparticle arrays,” Appl. Phys. Lett. 82(18), 3095–3097 (2003). [CrossRef]
  18. L. A. Dick, A. D. McFarland, C. L. Haynes, and R. P. Van Duyne, “Metal film over nanosphere (MFON) electrodes for surface-enhanced Raman spectroscopy (SERS): improvements in surface nanostructure stability and suppression of irreversible loss,” J. Phys. Chem. B 106(4), 853–860 (2002). [CrossRef]
  19. X. Zhang, M. A. Young, O. Lyandres, and R. P. Van Duyne, “Rapid detection of an anthrax biomarker by surface-enhanced Raman spectroscopy,” J. Am. Chem. Soc. 127(12), 4484–4489 (2005). [CrossRef] [PubMed]
  20. C. R. Yonzon, C. L. Haynes, X. Zhang, J. T. Walsh, and R. P. Van Duyne, “Glucose sensing using near-infrared surface-enhanced Raman spectroscopy: gold surfaces, 10-Day stability, and improved accuracy,” Anal. Chem. 76, 78–85 (2004). [CrossRef]
  21. Y. Fang, N.-H. Seong, and D. D. Dlott, “Measurement of the distribution of site enhancements in surface-enhanced Raman scattering,” Science 321(5887), 388–392 (2008). [CrossRef] [PubMed]
  22. E. Bailo and V. Deckert, “Tip-enhanced Raman scattering,” Chem. Soc. Rev. 37(5), 921–930 (2008). [CrossRef] [PubMed]
  23. A. D. McFarland, M. A. Young, J. A. Dieringer, and R. P. Van Duyne, “Wavelength-scanned surface-enhanced Raman excitation spectroscopy,” J. Phys. Chem. B 109(22), 11279–11285 (2005). [CrossRef]
  24. C. W. Kuo, K. H. Wei, C. H. Lin, J. Y. Shiu, and P. Chen, “Nanofluidic system for the studies of single DNA molecules,” Electrophoresis 29(14), 2931–2938 (2008). [PubMed]

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.


« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited