The oriented attachment of small nanoparticles (NPs) is recognized as an important mechanism involved in the growth of inorganic nanocrystals. However, non-oriented attachment of dissimilar NPs has been rarely observed in dispersion. This communication reports a welding phenomenon occurred directly between as-synthesized dispersions of single-component Au and chalcogenide NPs, which leads to the formation of asymmetric Au-chalcogenide hybrid NPs (HNPs). The welding of dissimilar NPs in dispersion is mainly driven by the ligand desorption-induced conformal contact between NPs and the diffusion of Au into chalcogenide NPs. The welding process can occur between NPs with distinct shapes or different capping agents or in different solvent media. A two-step assembly-welding mechanism is proposed for this process, based on our in situ electron spin resonance measurements and ab initio molecular dynamics simulation. The understanding of NP welding in dispersion may lead to the development of unconventional synthetic tools for the fabrication of hybrid nanostructures with diverse applications.

Bottom-up fabrication of such arrays with specific orientation of nanoparticles remains a challenge. In this paper, we report an immobilized seed-mediated growth strategy for the fabrication of two-dimensional (2D) arrays of mono- and bimetallic polyhedral nanocrystals with well-defined shapes and orientations on a substrate. This method relies on the controlled solution-phase deposition of metals (i.e., Au and Pd) on a selectively exposed surface of self-assembled seed nanoparticles that are immobilized on a substrate through collapsed polymer brushes. By using this approach, we demonstrated the preparation of various 2D arrays of shaped Au nanocrystals and Au core/Pd shell nanocrystals with asymmetric geometry of two halves and controlled orientations with respect to the substrate. The shape evolution of seeds to final nanocrystals was systematically monitored and evaluated by electron microscopic imaging. Our study suggests that the shape and orientation of nanocrystals within arrays is determined by the preferential orientation of assembled seed nanoparticles on the substrate and controllable deposition of metals on exposed crystal facets of immobilized seeds. The synthetic approach we developed presents an important addition to current tools for the fabrication of substrate-supported functional nanostructures.

Professional development in chemistry doctoral programs has traditionally relied on the skills and opportunities embedded within the requirements of the Ph.D. program being sufficient for employment. As a result, little emphasis is usually placed on career planning and exploration within the doctoral curriculum. Additionally, the support provided in finding employment after graduation can vary largely depending on individual advisors, departments, and university resources. Although the resources provided by individual departments for chemistry doctoral students may appear sufficient, this article discusses the establishment and implementation of a peer-supported professional-development initiative (PSPDI): a nondepartmentally initiated program created by doctoral students for doctoral students to provide opportunities for professional development and career resources. The implementation of a PSPDI and the benefits a peer-supported program are discussed, along with other details that may be relevant for programs looking to implement or enhance existing doctoral professional-development programs.