Gradient Core-Shell Quantum Dots

Colloidal quantum dots with core-shell structures in which both components feature alloyed gradient compositions have been prepared by researchers in Israel (ACS Nano, DOI: 10.1021/nn101760t). By developing a synthesis method for preparing nanoparticles with two regions of varying composition, Georgy I. Maikov, Efrat Lifshitz, and coworkers at Technion—Israel Institute of Technology have devised a strategy for customizing the particles’ optical properties without varying their sizes, which is the standard way to customize those properties. The advance may prove useful in biological tagging, photovoltaics, and other size-dependent applications. The researchers say that samples consisting of PbSe/PbS cores and shells with radially varying compositions of Se and S are highly stable and exhibit enhanced and tunable optical properties compared with uniform-composition core-shell particles. For example, the particles display increased room-temperature photoluminescence quantum yields, tunable shifts in the optical absorption edge, and radiative lifetimes that can be customized by tailoring the shell width and composition.