Abstract
This paper reports on the enhancement of fluorescence that can result from the proximity of fluorophores to metallic nanoparticles (NPs). This plasmonic enhancement, which is a result of the localized surface plasmon resonance at the metal surface, can be exploited to improve the signal obtained from optical biochips and thereby lower the limits of detection. There are two distinct enhancement effects: an increase in the excitation of the fluorophore and an increase in its quantum efficiency. This study focuses on the first of these effects where the maximum enhancement occurs when the NP plasmon resonance wavelength coincides with the fluorophore absorption band. In this case, the excitation enhancement is proportional to the square of the amplitude of the electric field. The scale of the enhancement depends on many parameters, such as NP size and shape, metal type, and NP–fluorophore separation. A model system consisting of spherical gold/silver alloy NPs, surrounded by a silica spacer shell, to which is attached a fluorescent ruthenium dye, was chosen and the dependence of the fluorescence enhancement on NP diameter was investigated. Theoretical calculations, based on Mie theory, were carried out to predict the maximum possible enhancement factor for spherical NPs with a fixed composition and a range of diameters. Spherical NPs of the same composition were fabricated by chemical preparation techniques. The NPs were coated with a thin silica shell to overcome quenching effects and the dye was attached to the shell.
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References
Sokolov K, Chumanov G, Cotton TM (1998) Enhancement of molecular fluorescence near the surface of colloidal metal films. Anal Chem 70(18):3898–3905
Stich N, Gandhum A, Matushin V et al (2001) Nanofilms and nanoclusters: Energy sources driving fluorophores of biochip bound labels. J Nanosci Nanotechnol 1(4):397–405
Lakowicz JR, Malicka J, Gryczynski I et al (2003) Radiative decay engineering: the role of photonic mode density in biotechnology. Anal Biochem 36(14):R240–R249
Stranik O, McEvoy HM, McDonagh C et al (2005) Plasmonic enhancement of fluorescence for sensor applications. Sens Actuators B Chem 107(1):148–153
Lakowicz JR, Shen B, Gryczynski I (2001) Intrinsic fluorescence from DNA can be enhanced be metallic particles. Biochem Biophys Res Commun 286:875–879
Mie G (1908) Beitrage zur Optik trueber Medien speziell kolloidaler Metalloesungen. Ann Phys 25:377–445
Bohren CF, Huffman DR (1983) Absorption and scattering of light by small particles. Wiley, New York
Gaudry M, Lerme J, Cottancin E et al (2001) Optical properties of (AuxAg1-x)(n) clusters embedded in alumina: evolution with size and stoichiometry. Phys Rev B 64(8):art. no.-085407:1–7
Huang T, Murray RW (2002) Quenching of [Ru(bpy)3]2+ fluorescence by binding to Au nanoparticles. Langmuir 18:7077–7081
Watts RJ, Crosby GA (1971) Spectroscopic characterization of complexes of ruthenium and iridium with 4,4′-diphenyL2,2′-bipyridine and 4,7-diphenyl-1,lO-phenanthroline. J Am Chem Soc 93:318
Link S, Wang ZL, El-Sayed MA (1999) Alloy formation of gold–silver nanoparticles and the dependence of the plasmon absorption on their composition. J Phys Chem B 103(18):3529–3533
Turkevich J, Stevenson PC, J Hillier (1951) A study of the nucleation and growth processes in the synthesis of colloidal gold. Discuss Faraday Soc 11:55
Brown KR, Walter DG, Natan MJ (2000) Seeding of colloidal Au nanoparticle solutions. 2. Improved control of particle size and shape. Chem Mat 12(2):306–313
LizMarzan LM, Giersig M, Mulvaney P (1996) Synthesis of nanosized gold-silica core-shell particles. Langmuir 12(18):4329–4335
Santra S, Wang K, Topec R et al (2001) Development of novel dye doped silica nanoparticles for biomarker application. J Biomed Opt 6(2):160–166
Rendell D (1987) Fluorescence and phosphorescence. Wiley, New York
Wokaun A, Lutz HP, King AP et al (1983) Energy-transfer in surface enhanced luminescence. J Chem Phys 79(1):509–514
Weitz DA, Garoff S, Gersten JI et al (1983) The enhancement of Raman-scattering, resonance Raman-scattering, and fluorescence from molecules adsorbed on a rough silver surface. J Chem Phyf 78(9):5324–5338
Anger P, Bharadwaj P, Novotny L (2006) Enhancement and quenching of single-molecule fluorescence. Phys Rev Lett 96:113002
Mayer C, Stich N, Schalkhammer T et al (2001) Slide-format proteomic biochip based on surface-enhanced nanocluster-resonance. Fresenius J Anal Chem 371:238–245
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This material is based on works supported by Science Foundation Ireland under Grant No. 05/CE3/B754.
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Stranik, O., Nooney, R., McDonagh, C. et al. Optimization of Nanoparticle Size for Plasmonic Enhancement of Fluorescence. Plasmonics 2, 15–22 (2007). https://doi.org/10.1007/s11468-006-9020-9
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DOI: https://doi.org/10.1007/s11468-006-9020-9