Dye Encapsulation in Fluorescent Core–Shell Silica Nanoparticles as Probed by Fluorescence Correlation Spectroscopy

Journal Article · Tue Mar 05 04:00:00 EST 2019 · Journal of Physical Chemistry. C

DOI:https://doi.org/10.1021/acs.jpcc.9b00297· OSTI ID:1593725

Kohle, Ferdinand F. E. ^[1]; Hinckley, Joshua A. ^[2]; Wiesner, Ulrich B. ^[2]

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1. Cornell Univ., Ithaca, NY (United States); Cornell University
2. Cornell Univ., Ithaca, NY (United States)

Synthetic advances in the formation of ultrasmall (<10 nm) fluorescent poly(ethylene glycol)-coated (PEGylated) core–shell silica nanoparticles (SNPs), enabling improved particle size and surface chemical property control, have led to successful clinical translation of SNPs as diagnostic probes in oncology. Despite the success of such probes, details of the dye incorporation and resulting silica architecture are still poorly understood. Here, we employ afterpulse-corrected fluorescence correlation spectroscopy (FCS) to monitor fast fluorescence fluctuations (lag times <10^–5 s) of the negatively charged cyanine dye Cy5 as a probe to study such details for dye encapsulation in 5 nm silica cores of PEGylated core–shell SNPs (C dots). Upon deposition of additional silica shells over the silica core, we find that the amplitude of photoinduced cis–trans isomerization decreases, suggesting that the Cy5 dyes are located near or on the surface of the original SNP cores. In combination with time-correlated fluorescence decay measurements, we deduce radiative and nonradiative rates of the Cy5 dye in these particles. Finally, results demonstrate that FCS is a well-suited tool to investigate aspects of the photophysics of fluorescent nanoparticles, and that conformational changes of cyanine dyes like Cy5 are excellent indicators for the local dye environment within ultrasmall SNPs.

• Research Organization: Cornell Univ., Ithaca, NY (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF); National Institutes of Health (NIH)
• Grant/Contract Number: SC0010560
• OSTI ID: 1593725
• Journal Information: Journal of Physical Chemistry. C, Journal Name: Journal of Physical Chemistry. C Journal Issue: 15 Vol. 123; ISSN 1932-7447
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
dyes and pigments
fluorescence
fluorescence spectroscopy
nanoparticles silica