Measuring Quantum Efficiency of Organic Dyes Encapsulated in Dielectric NanoSpheres

ORAL

Abstract

We present results of a fluorescent quantum efficiency ($\Phi )$ study on the encapsulation of the near infrared dye indocyanine green (ICG) in calcium phosphate (CP) nanoparticles (dia$\sim $50 nm). The quantum efficiency ($\Phi $, described as the ratio of photons emitted to photons absorbed) provides a quantitative means of describing the fluorescence of an arbitrary molecule. However, standard quantum efficiency measurement techniques provide only $\Phi $ of the smallest fluorescing unit -- in the case of a nanoparticle suspension, the nanoparticle itself. This presents a problem in accurately describing the quantum efficiency of fluorophores embedded in a nanoparticle. We have developed a method to determine the quantum efficiency of the constituent fluorescent molecules embedded in such a nanoparticle, which provides a more meaningful comparison with the unencapsulated fluorophore. While applicable to generic systems, we present results obtained by our method for the ICG/CP nanoparticles in phosphate buffer solution, revealing a dramatic improvement in per-molecule $\Phi $ driven by encapsulation.

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Authors

  • Timothy Russin

    • Department of Physics, The Pennsylvania State University

  • Erhan Altinoglu

    • Department of Materials Science and Engeering, The Pennsylvania State University

  • James Adair

    • Department of Materials Science and Engeering, The Pennsylvania State University

  • Peter Eklund

    • Physics Department, Penn State University
    • Dept. of Physics, Penn State
    • Department of Physics, The Pennsylvania State University
    • Department of Physics, Department of Materials Science and Engeering, The Pennsylvania State University
    • Department of Physics, Department of Material Science and Engineering, Pennsylvania State University, University Park, PA 16802
    • Physics Department, Material Science \& Engineering Department
    • Department of Physics, Department of Material Sciece and Engineering, Pennsylvania State University
    • Department of Physics, Department of Materials Science \& Engineering and Materials Research Institute, Penn State University
    • Physics Department,Materials Science \& Engineering Department, Pennsylvania State University