Amplified two-photon brightness in organic multicomponent nanoparticles

In this study, we demonstrate how to easily obtain multicomponent fluorescent organic nanoparticles displaying an excitation energy-transfer cascade between the different molecular components. The use of an optically neutral polymer as a dopant helps to increase the colloidal stability of the water suspensions and to slow the loss of luminescence over time. In particular, core@shell@shell ternary nanoparticles are designed and investigated, providing strongly increased luminescence in the red spectral region. The two-photon brightness of the ternary nanoparticles is greatly enhanced with respect to that of the single-component nanoparticles. In addition, these ternary nanoparticles can be two-photon excited over a broad spectral range (from 600 nm to 1200 nm) inside the biological transparency window. This property, together with the good colloidal stability in aqueous suspension, suggests that these fully organic multicomponent nanosystems can be highly promising nanoprobes for use in bioimaging applications.