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