Seedless wet synthesis of copper-twinned nanocrystals

The wet synthesis of copper (Cu)-twinned nanostructures often requires the addition of noble metal seeds, as twinned Cu seeds are prone to oxidative etching, which inevitably introduces other metal species. In this study, a universal and seedless wet method is proposed for the synthesis of various Cu-twinned nanostructures, such as large Cu decahedrons (with sizes up to 300 nm), singly twinned Cu right bipyramids, and Cu nanorods. The amount of chloride ions (Cl-) and oleylamine and an optimal heating rate at the initial stage were proven to be crucial in this synthesis. Theoretical results revealed that the amount of Cl- could adjust the Gibbs free energy of Cu seeds by promoting the dissociation of oleylamine, which, in turn, determined the structure of thermodynamically favorable seeds based on the thermodynamic model. To the best of our knowledge, this is the first report on large Cu decahedrons and singly twinned Cu right bipyramids. Moreover, they both showed strong localized surface plasmon resonance in the near-infrared region. The photothermal conversion efficiency of large Cu decahedrons increased up to 52.9% upon 808 nm laser irradiation, which is the highest value ever reported for Cu nanocrystals. The optimal conditions for stablizing copper (Cu)-twinned seeds were carefully investigated. By tuning the amount of Cl- and oleylamine, different kinds of Cu-twinned nanostructures could be obtained by a universal seedless wet method.

Automated summary

A seedless wet method for the synthesis of copper twinned nanostructures has been proposed in this study, which successfully synthesized large copper decahedrons and singly twinned copper right bipyramids. Different kinds of copper twinned nanostructures could be obtained by adjusting the amount of chloride ions and oleylamine.