Polymeric Rulers: Distance-Dependent Emission Behaviors of Fluorophores on Flat Gold Surfaces and Bioassay Platforms Using Plasmonic Fluorescence Enhancement

Authors

  • Young Shik Chi,

    1. Department of Chemistry and School of Molecular Science (BK21) KAIST, Daejeon 305-701 (Korea)
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  • Hye Ryung Byon,

    1. Department of Chemistry Pohang University of Science and Technology (POSTECH) San 31, Hyoja-Dong, Nam-Gu, Pohang 790-784 (Korea)
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  • Bong Soo Lee,

    1. Department of Chemistry and School of Molecular Science (BK21) KAIST, Daejeon 305-701 (Korea)
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  • Bokyung Kong,

    1. Department of Chemistry and School of Molecular Science (BK21) KAIST, Daejeon 305-701 (Korea)
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  • Hee Cheul Choi,

    Corresponding author
    1. Department of Chemistry Pohang University of Science and Technology (POSTECH) San 31, Hyoja-Dong, Nam-Gu, Pohang 790-784 (Korea)
    • Department of Chemistry Pohang University of Science and Technology (POSTECH) San 31, Hyoja-Dong, Nam-Gu, Pohang 790-784 (Korea).
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  • Insung S. Choi

    Corresponding author
    1. Department of Chemistry and School of Molecular Science (BK21) KAIST, Daejeon 305-701 (Korea)
    2. Department of Bio and Brain Engineering Department of Chemical and Biomolecular Engineering KAIST, Daejeon 305-701 (Korea)
    • Department of Chemistry and School of Molecular Science (BK21) KAIST, Daejeon 305-701 (Korea).
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  • This work was supported by a Korea Research Foundation Grant funded by the Korean Government (MOEHRD, Basic Research Promotion Fund) (KRF-2005-070-C00078). The FTIR spectrophotometer was purchased by a research fund from the Center for Molecular Design and Synthesis. HRB and HCC thank the Nano/Bio Science & Technology Program of MOST (2008-00979) for financial support. Supporting Information is available online from Wiley InterScience or from the author.

Abstract

In this paper, we introduce the concept of a “polymeric ruler” for investigating distance-dependent emission behaviors of fluorophores, namely the quenching or enhancement of fluorescence, on flat Au surfaces in the range of 5 to ∼100 nm, which has not previously been easily accessible. The polymeric ruler is constructed by a highly controllable surface-initiated atom transfer radical polymerization of oligo(ethylene glycol)methacrylate (OEGMA), and the obtained thicknesses of the poly(OEGMA) (pOEGMA) layers range from ∼5 to ∼80 nm. The quenching or enhancement of fluorescence is found to be dependent upon the distance between fluorophores and the Au surface. In brief, fluorescence quenching occurs at distances within about 15 nm from the Au surface, and surface-enhanced fluorescence is observed at tens of nanometers beyond the range of quenching with the maximum enhancement at about 40–50 nm. The obtained information on the distance-dependent surface-enhanced fluorescence is applied to the construction of highly sensitive bioassay platforms: the use of the 50 nm thick pOEGMA layer lowers the detection limit up to 1 pM.

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