Non-Technical Abstract Metal nanoparticles are generally stabilized with an organic capping layer, forming an organic shell-metal core structure. The materials properties and functions are therefore largely determined by these two components. With support from the Solid State and Materials Chemistry Program in the Division of Materials Research, this research project is focused on the development of effective procedures for the preparation of a special class of nanoparticle materials where the organic ligands as well as the metal components may be independently incorporated into the nanoparticles in a spatially controlled manner. This provides a unique way to further manipulate the nanoparticle structures and properties. Neapolitan nanoparticles are used as the initial illustrating examples, analogous to a layered Neapolitan cake with structurally distinct organic/metal components at the two poles and at the equatorial ring. These nanoparticles may be used to prepare more complicated nanoparticle materials and structures, and for electrocatalytic reduction of oxygen, a critical reaction at fuel cell cathode. The research activities are intimately integrated with various educational efforts, from on-hands training of diverse student researchers including graduate students, undergraduate students and high-school students.
The specific aim of this research project is to develop effective protocols based on deliberate interfacial engineering for the preparation of Neapolitan nanoparticles with a tri-patchy structure not only of the organic capping layers but also of the metal cores. This is built upon the prior success of the PI's laboratory in the preparation of amphiphilic Janus nanoparticles. In the present research project the focus is on Neapolitan nanoparticles that exhibit distinctly different chemical functionalities at the two poles and on the equatorial ring of the nanoparticles. Concurrently, the original monometallic nanoparticle cores may be converted to bimetallic or even trimetallic ones by taking advantage of galvanic exchange reactions between the nanoparticles and metal-thiolate complexes, with the second and third metals also distributed asymmetrically on the nanoparticle cores. The ready and independent manipulation of both the organic capping layers and the metal cores into segregated patches may be exploited for further and more complicated chemical functionalization of the nanoparticles. The fundamental insights are anticipated to further advance our understanding of the mechanisms that control the organized assembly of nanostructured materials in general.
