Plexcitonic nanorattles for ultra-efficient SERS detection

In this work, we prepare plexcitonic nanoparticles composed by plasmonic nanoparticles, Au@Ag@mSiO2 nanorattles, and J-aggregates of TDBC cyanine dye to be used as ultra-efficient SERS-tags. The methodology used here allowed us to improve the colloidal stability of the plexcitonic nanoparticles. The optical properties have been characterised by UV-vis-NIR and Surface-Enhanced Raman Scattering (SERS) spectroscopies. Besides, finite-difference time-domain (FDTD) calculations revealed that the electromagnetic field is strongly confined into the J-aggregate deposited over the surface of the plasmonic nanoparticle at wavelengths near the upper plexciton. However, for the lower plexciton mode, the electromagnetic field decays through the J-aggregate/water interface. In summary, the plexcitonic nanoparticles showed high SERS efficiency for 532 nm and 633 nm laser lines, even reaching single-nanoparticle detection. The results obtained showed us the significance of strong coupling effect which might lead new possibilities for ultrasensitive biosensing and bioimaging.