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Recent developments in optofluidic-surface-enhanced Raman scattering systems: Design, assembly, and advantages

Published online by Cambridge University Press:  17 January 2011

Yin Yin
Affiliation:
Department of Physics, Southeast University, Nanjing 211189, China
Teng Qiu*
Affiliation:
Department of Physics, Southeast University, Nanjing 211189, China
Wenjun Zhang
Affiliation:
Department of Physics and Materials Science, City University of Hong Kong, Kowloon, Hong Kong
Paul K. Chu*
Affiliation:
Department of Physics and Materials Science, City University of Hong Kong, Kowloon, Hong Kong
*
a)Address all correspondence to these authors. e-mail: tqiu@seu.edu.cn
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Abstract

Surface-enhanced Raman scattering (SERS) coupled with micro- or nanofluidics integrated into optofluidic devices offer many advantages over conventional SERS conducted under static conditions. Higher reproducibility, larger intensity, as well as greater enhancement can be achieved by efficient mixing of analytes and SERS enhancers under a continuous flow. Progress and advances in the past 10 years, including the design of channels and efficient mixing conditions, assemblies of SERS substrates for optimal enhancement, and advantages of optofluidic-SERS analysis, are reviewed. Recent results show that optofluidic-SERS effectively overcomes many of the difficulties and limitations plaguing conventional SERS and the novel technique has enormous application potential.

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Reviews
Copyright
Copyright © Materials Research Society 2011

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References

REFERENCES

1.Smith, E. and Dent, G.: Modern Raman Spectroscopy-A Practical Approach (John Wiley & Sons Ltd., West Sussex, England, 2005).Google Scholar
2.Schrader, B.: Infrared and Raman Spectroscopy (VCH, Weinheim, Germany, 1995).CrossRefGoogle Scholar
3.Raman, C.V. and Krishnan, K.S.: A new type of secondary radiation. Nature 121, 501 (1928).CrossRefGoogle Scholar
4.Schmitt, M. and Popp, J.: Raman spectroscopy at the beginning of the twenty-first century. J. Raman Spectrosc. 37, 20 (2006).CrossRefGoogle Scholar
5.Fleischmann, M., Hendra, P.J., and McQuillan, A.J.: Raman spectra of pyridine adsorbed at a silver electrode. Chem. Phys. Lett. 26, 163 (1974).CrossRefGoogle Scholar
6.Huh, Y.S., Chung, A.J., and Erickson, D.: Surface enhanced Raman spectroscopy and its application to molecular and cellular analysis. Microfluid. Nanofluid. 6, 285 (2009).CrossRefGoogle Scholar
7.Jeanmaire, D.L. and Van Duyne, R.P.: Surface Raman spectroelectrochemistry. J. Electroanal. Chem. 84, 1 (1977).CrossRefGoogle Scholar
8.Chan, S., Kwon, S., Koo, T.W., Lee, L.P., and Berlin, A.A.: Surface-enhanced Raman scattering of small molecules from silver-coated silicon nanopores. Adv. Mater. 15, 1595 (2003).CrossRefGoogle Scholar
9.Doering, W.E. and Nie, S.: Spectroscopic tags using dye-embedded nanoparticies and surface-enhanced Raman scattering. Anal. Chem. 75, 6171 (2003).CrossRefGoogle Scholar
10.Mulvaney, S.P., Musick, M.D., Keating, C.D., and Natan, M.J.: Glass-coated, analyte-tagged nanoparticles: A new tagging system based on detection with surface-enhanced Raman scattering. Langmuir 19, 4784 (2003).CrossRefGoogle Scholar
11.Jana, N.R.: Silver coated gold nanoparticles as new surface enhanced Raman substrate at low analyte concentration. Analyst (Lond.) 128, 954 (2003).CrossRefGoogle Scholar
12.Kneipp, K., Kneipp, H., Itzkan, I., Dasari, R.R., and Feld, M.S.: Ultrasensitive chemical analysis by Raman spectroscopy. Chem. Rev. 99, 2957 (1999).CrossRefGoogle ScholarPubMed
13.Xu, Y., Wu, J., Sun, W., Tao, D., Yang, L., Song, Z., Weng, S., Xu, Z., Soloway, R.D., Xu, D., and Xu, G.: A new mechanism of Raman enhancement and its application. Chemistry 8, 5323 (2002).3.0.CO;2-E>CrossRefGoogle ScholarPubMed
14.Kambhampati, P., Campion, A., and Song, O.K.: Probing photoinduced charge transfer at atomically smooth metal surfaces using surface-enhanced Raman scattering. Phys. Status Solidi A: Appl. Res. 75, 233 (1999).3.0.CO;2-Y>CrossRefGoogle Scholar
15.Qiu, T., Zhang, W.J., and Chu, P.K.: Recent progress in fabrication of anisotropic nanostructures for surface-enhanced Raman spectroscopy. Recent Pat. Nanotechnol. 3, 10 (2009).CrossRefGoogle ScholarPubMed
16.Moskovits, M.: Surface enhanced spectroscopy. Rev. Mod. Phys. 57, 783 (1985).CrossRefGoogle Scholar
17.Moskovits, M.: Surface-enhanced Raman spectroscopy: A brief retrospective. J. Raman Spectrosc. 36, 485 (2005).CrossRefGoogle Scholar
18.Chen, L. and Choo, J.: Recent advances in surface-enhanced Raman scattering detection technology for microfluidic chips. Electrophoresis 29, 1815 (2008).CrossRefGoogle ScholarPubMed
19.Ni, J., Lipert, R.J., Dawson, G.B., and Porter, M.D.: Immunoassay readout method using extrinsic Raman labels adsorbed on immunogold colloids. Anal. Chem. 71, 4903 (1999).CrossRefGoogle ScholarPubMed
20.Kneipp, K., Wang, Y., and Kneipp, H.: Single molecule detection using surface-enhanced Raman scattering (SERS). Phys. Rev. Lett. 78, 1667 (1997).CrossRefGoogle Scholar
21.Kneipp, K., Kneipp, H., and Kartha, V.B.: Detection and identification of a single DNA base molecule using surface-enhanced Raman scattering (SERS). Phys. Rev. E: Stat. Phys., Plasmas, Fluids, Relat. Interdiscip. Top. 57, 6281 (1998).CrossRefGoogle Scholar
22.Nie, S. and Emory, R.S.: Probing single molecules and single nanoparticles by surface-enhanced Raman scattering. Science 275, 1102 (1997).CrossRefGoogle ScholarPubMed
23.Taylor, G.T., Sharma, S.K., and Mohanan, K.: Optimization of a flow-injection sampling system for quantitative-analysis of dilute aqueous-solutions using combined resonance and surface-enhanced Raman-spectroscopy (SERRS). Appl. Spectrosc. 44, 635 (1990).CrossRefGoogle Scholar
24.Laserna, J.J.: Combining fingerprinting capability with trace analytical detection: Surface-enhanced Raman spectrometry. Anal. Chim. Acta 283, 607 (1993).CrossRefGoogle Scholar
25.He, L., Natan, M.J., and Keating, C.D.: Surface-enhanced Raman scattering: A structure-specific detection method for capillary electrophoresis. Anal. Chem. 72, 5438 (2000).CrossRefGoogle ScholarPubMed
26.Walker, P.A., Morris, M.D., Burns, M.A., and Johnson, B.N.: Isotachophoretic separations on a microchip: Normal Raman spectroscopy detection. Anal. Chem. 70, 3766 (1998).CrossRefGoogle ScholarPubMed
27.Connatser, R.M., Cochran, M., Harrison, R.J., and Sepaniak, M.J.: Analytical optimization of nanocomposite surface-enhanced Raman spectroscopy/scattering detection in microfluidic separation devices. Electrophoresis 29, 1441 (2008).CrossRefGoogle ScholarPubMed
28.Dölle, A., Suhm, M.A., and Weingärtner, H.J.: Anisotropic molecular reorientation of liquid benzene revisited. A study using 13C magnetic relaxation through chemical shift anisotropy and spin rotation. J. Chem. Phys. 94, 3361 (1991).CrossRefGoogle Scholar
29.Kneipp, K., Kneipp, H., Manoharan, R., Hanlon, E.B., Itzkan, I., Dasari, R.R., and Feld, M.S.: Extremely large enhancement factors in surface-enhanced Raman scattering for molecules on colloidal gold clusters. Appl. Spectrosc. 52, 1493 (1998).CrossRefGoogle Scholar
30.Chehaidar, A., Carles, R., Zwick, A., Meunier, C., Cros, B., and Durand, J.: Chemical bonding analysis of a-SiC: H films by Raman spectroscopy. J. Non-Cryst. Solids 37, 169 (1994).Google Scholar
31.Ehlert, A. and Buettgenbach, S.: Automatic sensor system for groundwater monitoring network. Proc. SPIE 3857, 61 (1999).CrossRefGoogle Scholar
32.Psaltis, D., Quake, S.R., and Yang, C.: Developing optofluidic technology through the fusion of microfluidics and optics. Nature 442, 381 (2006).CrossRefGoogle ScholarPubMed
33.Berthod, A., Laserna, J.J., and Winefordner, J.D.: Surface enhanced Raman spectrometry on silver hydrosols studied by flow-injection analysis. Appl. Spectrosc. 41, 1137 (1987).CrossRefGoogle Scholar
34.Manz, A., Harrison, D.J., Verpoorte, E.M., Fettinger, J.C., Paulus, A., Lüdi, H., and Widmer, H.M.: Planar chips technology for miniaturization and integration of separation techniques into monitoring systems-capillary electrophoresis on a chip. J. Chromatog. 593, 253 (1992).CrossRefGoogle Scholar
35.Park, T., Lee, S., Seong, G.H., Choo, J., Lee, E.K., Kim, Y.S., Ji, W.H., Hwang, S.Y., Gweon, D.G., and Lee, S.: Highly sensitive signal detection of duplex dye-labelled DNA oligonucleotides in a PDMS microfluidic chip: Confocal surface-enhanced Raman spectroscopic study. Lab Chip 5, 437 (2005).CrossRefGoogle Scholar
36.Lee, P.C. and Meisel, D.: Adsorption and surface-enhanced Raman of dyes on silver and gold sols. J. Phys. Chem. 86, 3391 (1982).CrossRefGoogle Scholar
37.Leopold, N. and Lendl, B.: A new method for fast preparation of highly surface-enhanced Raman scattering (SERS) active silver colloids at room temperature by reduction of silver nitrate with hydroxylamine hydrochloride. J. Phys. Chem. B 107, 5723 (2003).CrossRefGoogle Scholar
38.Gunnarsson, L., Bjerneld, E.J., Xu, H., Petronis, S., Kasemo, B., and Käll, M.: Interparticle coupling effects in nanofabricated substrates for surface-enhanced Raman scattering. Appl. Phys. Lett. 78, 802 (2001).CrossRefGoogle Scholar
39.Dick, L.A., McFarland, A.D., Haynes, C.L., and Van Duyne, R.P.: 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, 853 (2002).CrossRefGoogle Scholar
40.Faulds, K., Graham, D., and Smith, W.E.: Evaluation of surface-enhanced resonance Raman scattering for quantitative DNA analysis. Anal. Chem. 76, 412 (2004).CrossRefGoogle ScholarPubMed
41.Wang, H., Levin, C.S., and Halas, N.J.: Nanosphere arrays with controlled sub-10-nm gaps as surface-enhanced Raman spectroscopy substrates. J. Am. Chem. Soc. 127, 14992 (2005).CrossRefGoogle ScholarPubMed
42.White, I.M., Oveys, H., and Fan, X.: Liquid core optical ring resonator sensors. Opt. Lett. 31, 1319 (2006).CrossRefGoogle ScholarPubMed
43.Docherty, F.T., Monaghan, P.B., Keir, R., Graham, D., Smith, W.E., and Cooper, J.M.: The first SERRS multiplexing from labelled oligonucleotides in a microfluidics lab-on-a-chip. Chem. Commun. 1, 118 (2004).CrossRefGoogle Scholar
44.White, I.M., Gohring, J., and Fan, X.: SERS-based detection in an optofluidic ring resonator platform. Opt. Express 15, 17434 (2007).CrossRefGoogle Scholar
45.Measor, P., Seballos, L., Yin, D., and Zhang, J.Z.: On-chip surface-enhanced Raman scattering detection using integrated liquid-core waveguides. Appl. Phys. Lett. 90, 211107 (2007).CrossRefGoogle Scholar
46.White, I.M., Shapova, S.I., Zhu, H., Suter, J.D., Lacey, S., Zhang, P., Oveys, H., Brewington, L., Gohring, J., and Fan, X.: Applications of the liquid core optical ring resonator platform. Proc. SPIE 6757, 675707 (2007).CrossRefGoogle Scholar
47.Huh, Y.S. and Erickson, D.: Aptamer based surface-enhanced Raman scattering detection of vasopressin using multilayer nanotube arrays. Biosens. Bioelectron. 25, 1240 (2010).CrossRefGoogle ScholarPubMed
48.Choi, D., Kang, T., Cho, H., Choi, Y., and Lee, L.P.: Additional amplifications of SERS via an optofluidic CD-based platform. Lab Chip 9, 239 (2009).CrossRefGoogle ScholarPubMed
49.Becker, H. and Gartner, C.: Polymer microfabrication methods for microfluidic analytical applications. Electrophoresis 21, 12 (2000).3.0.CO;2-7>CrossRefGoogle ScholarPubMed
50.Ng, J.M., Gitlin, I., Stroock, A.D., and Whitesides, G.M.: Components for integrated poly(dimethylsiloxane) microfluidic systems. Electrophoresis 23, 3461 (2002).3.0.CO;2-8>CrossRefGoogle ScholarPubMed
51.Becker, H. and Locascio, L.E.: Polymer microfluidic devices. Talanta 56, 267 (2002).CrossRefGoogle ScholarPubMed
52. deMello, A.J.: Control and detection of chemical reactions in microfluidic systems. Nature 442, 394 (2006).CrossRefGoogle ScholarPubMed
53.Sia, S.K. and Whitesides, G.M.: Microfluidic devices fabricated in poly(dimethylsiloxane) for biological studies. Electrophoresis 24, 3563 (2003).CrossRefGoogle ScholarPubMed
54.Ohnishi, N., Satoh, W., Morimoto, K., Fukuda, J., and Suzuki, H.: Automatic electrochemical sequential processing in a microsystem for urea detection. Sens. Actuators, B: Chem. 144, 146 (2010).CrossRefGoogle Scholar
55.Choban, E.R., Markoski, L.J., Wieckowski, A., and Kenis, P.J.A.: Microfluidic fuel cell based on laminar flow. J. Power Sources 128, 54 (2004).CrossRefGoogle Scholar
56.Kockmann, N., Kastner, J., and Woias, P.: Reactive particle precipitation in liquid microchannel flow. Chem. Eng. J. 135, 110 (2008).CrossRefGoogle Scholar
57.Lee, D., Lee, S., Seong, G.H., Choo, J., Lee, E.K., Gweon, D.G., and Lee, S.: Quantitative analysis of methyl parathion pesticides in a polydimethylsiloxane microfluidic channel using confocal surface-enhanced raman spectroscopy. Appl. Spectrosc. 60, 373 (2006).CrossRefGoogle Scholar
58.Quang, L.X., Lim, C., Seong, G.H., Choo, J., Dob, K.J., and Yoo, S.K.: A portable surface-enhanced Raman scattering sensor integrated with a lab-on-a-chip for field analysis. Lab Chip 8, 2214 (2008).CrossRefGoogle ScholarPubMed
59.Kim, D.J., Oh, H.J., Park, T.H., Choo, J.B., and Lee, S.H.: An easily integrative and efficient micromixer and its application to the spectroscopic detection of glucose-catalyst reactions. Analyst (Lond.) 130, 293 (2005).CrossRefGoogle Scholar
60.Liu, R.H., Yang, J., Pindera, M.Z., Athavale, M., and Grodzinski, P.: Bubble-induced acoustic micromixing. Lab Chip 2, 151 (2002).CrossRefGoogle ScholarPubMed
61.Oddy, M.H., Santiago, J.G., and Mikkelsen, J.C.: Electrokinetic instability micromixing. Anal. Chem. 73, 5822 (2001).CrossRefGoogle ScholarPubMed
62.Wang, Y., Chen, H., Dong, S., and Wang, E.: Surface-enhanced Raman scattering of silver-gold bimetallic nanostructures with hollow interiors. J. Chem. Phys. 125, 044710 (2006).CrossRefGoogle ScholarPubMed
63.Lee, S.H., Bantz, K.C., Lindquist, N.C., Oh, S.H., and Haynes, C.L.: Self-assembled plasmonic nanohole arrays. Langmuir 25, 13685 (2009).CrossRefGoogle ScholarPubMed
64.Luo, Z., Yang, W., Peng, A., Ma, Y., Fu, H., and Yao, J.: Net-like assembly of Au nanoparticles as a highly active substrate for surface-enhanced Raman and infrared spectroscopy. J. Phys. Chem. A 113, 2467 (2009).CrossRefGoogle ScholarPubMed
65.Kang, T., Yoon, I., Kim, J., Ihee, H., and Kim, B.: Au nanowire–Au nanoparticles conjugated system which provides micrometer size molecular sensors. Chemistry 16, 1351 (2010).CrossRefGoogle ScholarPubMed
66.Qiu, T., Wu, X.L., Shen, J.C., and Chu, P.K.: Silver nanocrystal superlattice coating for molecular sensing by surface-enhanced Raman spectroscopy. Appl. Phys. Lett. 89, 131914 (2006).CrossRefGoogle Scholar
67.Qiu, T., Zhang, W.J., Lang, X.Z., Zhou, Y.J., Cui, T.J., and Chu, P.K.: Controlled assembly of highly Raman-enhancing silver nanocap arrays templated by porous anodic alumina membranes. Small 5, 2333 (2009).CrossRefGoogle ScholarPubMed
68.Fan, M. and Brolo, A.G.: Silver nanoparticles self assembly as SERS substrates with near single molecule detection limit. Phys. Chem. Chem. Phys. 11, 7381 (2009).CrossRefGoogle ScholarPubMed
69.Ward, D.R., Grady, N.K., Levin, C.S., Halas, N.J., Wu, Y.P., Nordlander, P., and Natelson, D.: Electromigrated nanoscale gaps for surface-enhanced Raman spectroscopy. Nano Lett. 7, 1396 (2007).CrossRefGoogle ScholarPubMed
70.Min, Q., Santos, M.J.L., Girotto, E.M., Brolo, A.G., and Gordon, R.: Localized Raman enhancement from a double-hole nanostructure in a metal film. J. Phys. Chem. C 112, 15098 (2008).CrossRefGoogle Scholar
71.Sackmann, M., Bom, S., Balster, T., and Materny, A.: Nanostructured gold surfaces as reproducible substrates for surface-enhanced Raman spectroscopy. J. Raman Spectrosc. 38, 277 (2007).CrossRefGoogle Scholar
72.Nirode, W.F., Devault, G.L., Sepaniak, M.J., and Cole, R.O.: On-column surface-enhanced Raman spectroscopy detection in capillary electrophoresis using running buffers containing silver colloidal solutions. Anal. Chem. 72, 1866 (2000).CrossRefGoogle ScholarPubMed
73.Connatser, R.M., Cochran, M., Harrison, R.J., and Sepaniak, M.J.: Analytical optimization of nanocomposite surface-enhanced Raman spectroscopy/scattering detection in microfluidic separation devices. Electrophoresis 29, 1441 (2008).CrossRefGoogle ScholarPubMed
74.Smith, W.E., Faulds, K., and Graham, D.: Quantitative surface-enhanced resonance Raman spectroscopy for analysis. Top. Appl. Phys. 103, 381 (2006).CrossRefGoogle Scholar
75.Bell, S.E. and Sirimuthu, N.M.: Quantitative surface-enhanced Raman spectroscopy. Chem. Soc. Rev. 37, 1012 (2008).CrossRefGoogle ScholarPubMed
76.Ackermann, K.R., Henkel, T., and Popp, J.: Quantitative online detection of low-concentrated drugs via a SERS microfluidic system. ChemPhysChem 8, 2665 (2007).CrossRefGoogle Scholar
77.Tantra, R., Brown, R.J., and Milton, M.J.: Strategy to improve the reproducibility of colloidal SERS. J. Raman Spectrosc. 38, 1469 (2007).CrossRefGoogle Scholar
78.McLaughlin, C., MacMillan, D., McCardle, C., and Smith, W.E.: Quantitative analysis of mitoxantrone by surface-enhanced resonance Raman scattering. Anal. Chem. 74, 3160 (2002).CrossRefGoogle ScholarPubMed
79.Cialla, D., Hubner, U., Schneidewind, H., Moller, R., and Popp, J.: Probing innovative microfabricated substrates for their reproducible SERS activity. ChemPhysChem 9, 758 (2008).CrossRefGoogle ScholarPubMed
80.Canada, M.J.A., Medina, A.R., Frank, J., and Lendl, B.: Bead injection for surface enhanced Raman spectroscopy: Automated on-line monitoring of substrate generation and application in quantitative analysis. Analyst (Lond.) 127, 1365 (2002).CrossRefGoogle ScholarPubMed
81.Marz, A., Ackermann, K.R., Malsch, D., Bocklitz, T., and Popp, T.H.: Towards a quantitative SERS approach-online monitoring of analytes in a microfluidic system with isotope-edited internal standards. J. Biophoton. 2, 232 (2009).CrossRefGoogle Scholar
82.Jung, J.H., Choo, J., Kim, D.J., and Lee, S.: Quantitative determination of nicotine in a PDMS microfluidic channel using surface enhanced Raman spectroscopy. Bull. Korean Chem. Soc. 27, 277 (2006).Google Scholar
83.Lee, S., Choi, J., Chen, L., Park, B., Kyong, J.B., Seong, G.H., Choo, J., Lee, Y., Shin, K.H., Lee, E.K., Joo, S.W., and Lee, K.H.: Fast and sensitive trace analysis of malachite green using a surface-enhanced Raman microfluidic sensor. Anal. Chim. Acta 590, 139 (2007).CrossRefGoogle ScholarPubMed
84.Bose, B., Motiwale, L., and Rao, K.V.K.: DNA damage and G2/M arrest in Syrian hamster embryo cells during Malachite green exposure are associated with elevated phosphorylation of ERK1 and JNK1. Cancer Lett. 230, 260 (2005).CrossRefGoogle ScholarPubMed
85.Stammati, A., Nebbia, C., De Angelis, I., Albo, A.G., Carletti, M., Rebecchi, C., Zampaglioni, F., and Dacasto, M.: Effects of malachite green (MG) and its major metabolite, leucomalachite green (LMG), in two human cell lines. Toxicol. In Vitro 19, 853 (2005).CrossRefGoogle Scholar
86.Huebner, A., Srisa-Art, M., Holt, D., Abell, C., Hollfelder, F., deMello, A.J., and Edel, J.B.: Quantitative detection of protein expression in single cells using droplet microfluidics.: Chem. Commun. (Camb.) 12, 1218 (2007).CrossRefGoogle Scholar
87.Srisa-Art, M., deMello, A.J., and Edel, J.B.: High-throughput DNA droplet assays using picoliter reactor volumes. Anal. Chem. 79, 6682 (2007).CrossRefGoogle ScholarPubMed
88.Huebner, A., Sharma, S., Srisa-Art, M., Hollfelder, F., Edel, J.B., and deMello, A.J.: Microdroplets: A sea of applications? Lab Chip 8, 1244 (2008).CrossRefGoogle ScholarPubMed
89.Srisa-Art, M., Bonzani, I.C., Williams, A., Stevens, M.M., deMello, A.J., and Edel, J.B.: Identification of rare progenitor cells from human periosteal tissue using droplet microfluidics. Analyst (Lond.) 134, 2239 (2009).CrossRefGoogle ScholarPubMed
90.Srisa-Art, M., deMello, A.J., and Edel, J.B.: High-throughput confinement and detection of single DNA molecules in aqueous microdroplets. Chem. Commun. (Camb.) 43, 6548 (2009).CrossRefGoogle Scholar
91.Srisa-Art, M., Kang, D.K., Hong, J., Park, H., Leatherbarrow, R.J., Edel, J.B., Chang, S.I., and deMello, A.J.: Analysis of protein–protein interactions by using droplet-based microfluidics. ChemBioChem 10, 1605 (2009).CrossRefGoogle ScholarPubMed
92.Strehle, K.R., Cialla, D., Rosch, P., Henkel, T., Kohler, M., and Popp, J.: A reproducible surface-enhanced Raman spectroscopy approach: Online SERS measurements in a segmented microfluidic system. Anal. Chem. 79, 1542 (2007).CrossRefGoogle Scholar
93.Wang, G., Lim, C., Chen, L., Chon, H., Choo, J., Hong, J., and deMello, A.J.: Surface-enhanced Raman scattering in nanoliter droplets: Towards high-sensitivity detection of mercury (II) ions. Anal. Bioanal. Chem. 394, 1827 (2009).CrossRefGoogle ScholarPubMed
94.Blatchford, C.G., Campbell, J.R., and Creighton, J.A.: Plasma resonance-enhanced Raman-scattering by adsorbates on gold colloids: The effects of aggregation. Surf. Sci. 120, 435 (1982).CrossRefGoogle Scholar
95.Siiman, O., Bumm, L.A., Callaghan, R., Blatchford, C.G., and Kerker, M.: Surface-enhanced Raman scattering by citrate on colloidal silver. J. Phys. Chem. 87, 1014 (1983).CrossRefGoogle Scholar
96.Emory, S.R., Jensen, R.A., Wenda, T., Han, M., and Nie, S.M.: Re-examining the origins of spectral blinking in single-molecule and single-nanoparticle SERS. Faraday Discuss. 132, 249 (2006).CrossRefGoogle ScholarPubMed
97.McFarland, A.D., Young, M.A., Dieringer, J.A., and Van Duyne, R.P.: Wavelength-scanned surface-enhanced Raman excitation spectroscopy. J. Phys. Chem. B 109, 11279 (2005).CrossRefGoogle ScholarPubMed
98.Cyrankiewicz, M., Wybranowski, T., and Kruszewski, S.: Study of SERS efficiency of metallic colloidal systems. J. Phys.: Conf. Ser. 79, 012013 (2007).Google Scholar
99.Yang, Y., Matsubara, S., Nogamia, M., and Shi, J.: Controlling the aggregation behavior of gold nanoparticles. Mater. Sci. Eng., B 140, 172 (2007).CrossRefGoogle Scholar
100.Schwartzberg, A.M., Grant, C.D., Wolcott, A., Talley, C.E., Huser, T.R., Bogomolni, R., and Zhang, J.Z.: Unique gold nanoparticle aggregates as a highly active surface-enhanced Raman scattering substrate. J. Phys. Chem. B 108, 19191 (2004).CrossRefGoogle Scholar
101.Guingab, J.D., Lauly, B., Smith, B.W., Omenetto, N., and Winefordner, J.D.: Stability of silver colloids as substrate for surface enhanced Raman spectroscopy detection of dipicolinic acid. Talanta 74, 271 (2007).CrossRefGoogle ScholarPubMed
102.Busby, C.C. and Creighton, J.A.: Efficient gold and silver electrodes for surface enchanced Raman spectral studies of electrochemical systems: The behavior of pyridine and naphthalene adsorbed on roughened gold electrodes. J. Electroanal. Chem. 140, 379 (1982).CrossRefGoogle Scholar
103.Wang, M., Benford, M., Jing, N., Cote, G., and Kameoka, J.: Optofluidic device for ultra-sensitive detection of proteins using surface-enhanced Raman spectroscopy. Microfluid. Nanofluid. 6, 411 (2009).CrossRefGoogle Scholar
104.Huh, Y.S., Chung, A.J., Cordovez, B., and Erickson, D.: Enhanced on-chip SERS based biomolecular detection using electrokinetically active microwells. Lab Chip 9, 433 (2008).CrossRefGoogle ScholarPubMed
105.Tong, L., Righini, M., Gonzalez, M.U., Quidantb, R., and Käll, M.: Optical aggregation of metal nanoparticles in a microfluidic channel for surface-enhanced Raman scattering analysis. Lab Chip 9, 193 (2009).CrossRefGoogle Scholar
106.Lim, C., Hong, J., Chung, B.G., deMello, A.J., and Choo, J.: Optofluidic platforms based on surface-enhanced Raman scattering. Analyst (Lond.) 135, 837 (2010).CrossRefGoogle ScholarPubMed