Energy Transfer and Confined Motion of Dyes Trapped in Semiconducting Conjugated Polymer Nanoparticles

This paper focuses on the spectroscopic studies on coumarin 153 (C153) dye encapsulated semiconducting [poly(N-vinylcarbazole) (PVK)] polymer nanoparticles using steady state and time-resolved spectroscopy. A significant blue shift (40 nm) and the enhancement of PL intensity of C153 dye are observed due to the encapsulation of C153 dye inside PVK nanoparticles. The quantum yield of encapsulated dye molecule increases with increasing the concentration of PVK, i.e., with size of the particle. The significant quenching (93%) of the PL spectrum and the shortening of the decay time of host PVK indicate the efficient energy transfer (82.5%) from PVK to C153 dye. The radiative decay rate of dye is found to increase with increasing the size of polymer nanoparticles indicating the increase of the refractive index inside polymer nanoparticle. The increase of lateral diffusion constant (D-L) and the decrease of diffusion coefficient for wobbling motion (D-w) of dye molecules with an increase in the size of polymer nanoparticles suggest the increase in microviscosity and rigidity of the system.