Core-shell nanoarchitectures: a strategy to improve the efficiency of luminescence resonance energy transfer

The development of core-shell nanoparticles has shown a wide range of new applications in the fields of chemistry, bioscience, and materials science because of their improved physical and chemical properties over their single-component counterparts. In the present work, we took the core-shell nanoarchitectures as an example to research the luminescence resonance energy transfer (LRET) process between a luminescent Tb3+ chelate, N,N,N(1),N(1)-[4'-phenyl-2,2':6',2'-terpyridine-6,6'-diyl]bis(methylenenitrilo)tetrakis(acetate)-Tb3+ (PTTA-Tb3+), and an organic dye, 5-carboxytetramethylrhodamine (CTMR). PTTA-Tb3+ and CTMR were chosen as the donor-acceptor pair of LRET in our model construction because of their effective spectral overlapping. The core-shell nanoparticles featuring a CTMR-SiO2 core surrounded by a concentric PTTA-Tb3+-SiO2 shell were prepared using a reverse microemulsion method. These nanoparticles are spherical, uniform in size, and highly photostable. The results of LRET experiments show that the sensitized emission lifetime of the acceptor in the nanoparticles is significantly prolonged (∼246 μs), which is attributed to the long emission lifetime of the Tb3+ chelate donor. According to the results of the steady-state and time-resolved luminescence spectroscopy, an energy transfer efficiency of ∼80% and a large Förster distance between the donor and the acceptor in the core-shell nanoparticles are calculated, respectively. The new core-shell nanoparticles with a high LRET efficiency and long Förster distance enable them to be promising optical probes for a variety of possible applications such as molecular imaging and multiplex signaling.