Watching lanthanide nanoparticles one at a time: characterization of their photoluminescence dynamics at the single nanoparticle level.

Lanthanide nanoparticles (LnNPs) feature sharp emission lines together with millisecond emission lifetimes which make them promising luminescent probes for biosensing and bioimaging. Although LnNPs are attracting much interest, their photoluminescence properties at the single nanoparticle level remain largely unexplored. Here, we employ fluorescence correlation spectroscopy (FCS) and photoluminescence burst analysis to investigate the photodynamics of Sm- and Eu-based LnNPs with single nanoparticle sensitivity and microsecond resolution.

Three species multiplexing of fluorescent dyes and gold nanoclusters recovered with fluorescence lifetime correlation spectroscopy.

Biosensor applications often require the simultaneous detection of multiple analytes, with a clear need to go beyond the traditional multiplexing relying on distinct fluorescent dyes across the visible spectrum. Fluorescence lifetime correlation spectroscopy (FLCS) is a powerful approach taking advantage of the fluorescence lifetime information to separate the contributions of different fluorescent species with overlapping emission spectra. However, so far FLCS detection has been demonstrated only on binary mixtures of two fluorescent dyes, limiting its multiplexing capabilities.