Abstract
Noble-metal nanoparticles labeled with fluorescent molecules are used in a
variety of applications requiring the measurement of size and diffusion properties
of single nanoprobes. We have successfully used intrinsic surface-plasmon-induced
photoluminescence (SPPL) signatures of monodispersed bare gold and silver
nanoparticles in water to detect and measure their precise diffusion coefficient,
concentration and hydrodynamic radius by fluorescence correlation spectroscopy
(FCS). Measurement of the effective hydrodynamic radius confirms particle size to be
80 ± 8 and 64 ± 14 nm for gold and silver, respectively, which is in excellent
agreement with scanning electron microscopic measurements made on the same
particles. Detection of bare gold and silver nanoparticles at the single-molecule
level with moderately high value of “per particle brightness” (PPB) confirms those
particles to be used as fluorescent probes in biological research and in different
medical and biotechnology applications where fluorescence detection plays a vital
role. Additionally, these results demonstrate an alternative method for measuring
hydrodynamic properties, particularly the size-distribution of bare noble-metal
nanoparticles in solution using data-fitting algorithm for FCS based on the maximum
entropy method (MEMFCS).
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