Impact of Thermal Annealing on Facet-Directed Epitaxial and Decorated Nonepitaxial Pd-CsPbBr<sub>3</sub> Nanocrystal Heterostructures
Rakesh Kumar Behera, Narayan Pradhan
Abstract
Halide perovskite nanocrystals are the subject of in-depth research because of their bright color-tunable optical emissions. Synthesis of these nanocrystals and their phase stability in different halide compositions and reaction environments are also extensively studied. However, going beyond these nanocrystals, the chemistry of epitaxial growth of metallic crystals on selective facets of ionic crystals has not been largely established yet. For the formation of heteronucleations as well as retaining the epitaxial relation at the junction, a high reaction temperature remains a key factor. However, with an increase in temperature, there are possibilities for cross nucleations and also detachment of metal particles from the host. Keeping these in mind, herein, the thermal impacts on different structural combinations of Pd-CsPbBr 3 nanocrystal heterostructures are reported. Following the high-temperature reaction protocol, two types of heterostructures, facet-directive epitaxial and nonepitaxial decorated Pd-CsPbBr 3, are first obtained, and these are further explored to study the annealing impact. In these cases, smaller size Pd particles are first grown epitaxially and form a one-to-one heterostructure, and then with time, Pd cubes are observed to be decorated randomly. However, the formation and growth of Pd particles remained sensitive to both the reaction temperature and the time as these did not grow to beyond a certain size in the heterostructure, rather facilitated cross nucleation formation. This provides strong support that annealing does not hamper the epitaxial junction and it only helps the successive growth of nonepitaxially connected metal nanocrystals.