Amplified Fluorescence by Hollow-Porous Plasmonic Assembly: A New Observation and Its Application in Multiwavelength Simultaneous Detection.

Surface plasmon coupled emission (SPCE) is a new analytical technique that provides increased and directional radiation based on the near-field interaction between fluorophores and surface plasmons but suffers from the limitation of insufficient sensitivity. The assembly of hollow-porous plasmonic nanoparticles could be the qualified candidate. After the introduction of gold nanocages (AuNCs), fluorescence signal enhancement was realized by factors over 150 and 600 compared with the normal SPCE and free space emission, respectively, with a fluorophore layer thickness of approximately 10 nm; hence, the unique enhancement of SPCE by the AuNCs effectively overcomes the signal quenching induced by resonance energy transfer (in normal SPCE). This enhancement was proven to be triggered by the superior wavelength match, the enhanced electromagnetic field, and new radiation channel and process induced by the AuNC assembly, which provides an opportunity to increase the detection sensitivity and establish an optimal plasmonic enhancement system. The amplified SPCE system was employed for multiwavelength simultaneous enhancement detection through the assembly of mixed hollow nanoparticles (AuNCs and gold nanoshells), which could broaden the application of SPCE in simultaneous sensing and imaging for multianalytes.