Functionalized Plasmonic−Fluorescent Nanoparticles for Imaging and Detection

Plasmonic−fluorescent composite nanoparticles are considered as unique, multifunctional nanoprobes for plasmon- and fluorescence-based imaging and detection. However, their synthesis is challenging due to fluorescence quenching of the fluorophore by plasmonic particles and most of the successful methods produce composite particles of large size (diameter > 50 nm), which limit their wider applications. Here we report 20−30 nm diameter plasmonic−fluorescent composite nanoparticles with reasonable fluorescence quantum yield (12−16%). These particles are composed of 3−6 nm diameter Au/Ag cores and fluorescein-incorporated polymeric shells. They have high water solubility, good colloidal stability, stable fluorescence properties, and are amenable in deriving various functional nanoprobes. Different functional nanoprobes are derived from these composites and successfully used for fluorescence-based cell labeling as well as plasmon-based detection applications.