In situ modification of three-dimensional polyphenylene dendrimer-templated CuO rice-shaped architectures with electron beam irradiation

In this study, the high-energy electron beam of the transmission electron microscope (TEM) is utilized as an external force to in situ modify the polyphenylene dendrimer (G2Td(COOH)₁₆) templated CuO rice-shaped architecture (RSA). By virtue of the nanoscale precision of this approach, the electron beam-modified RSA retains its rice shape while the internal primary CuO nanoparticles are converted to the Cu₂O nanoparticles with increased size. Detailed investigation using a time-lapse TEM technique reveals that such a modification process is mainly constituted by two stages, involving the arrangement of the primary CuO nanoparticles and the transformation of the primary CuO into Cu₂O nanoparticles. Within the modification process, the highenergy electron beam of TEM serves as the external driving force and energy resource to improve the orientation and increase the crystallinity of the single-phase CuO nanoparticles and subsequently transfer the nanoparticle phase from CuO to Cu₂O. This study highlights a facile in situ way to finely tune the nanoscale morphology and chemical composition of nanoparticles and nanoparticle-based assembled structures.