DFT Study of Discrete Polyhedral Noble-Metal Nanostructures

Date
2019
Authors
Mullins, Sean
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Abstract

Recent intensive studies of gold nanostructures have concerned a variety of shapes - cages, rods, cubes, stars and tetra-helices - that were developed as the building blocks for novel functional materials. Among these, gold (Au) nano-cages (or -shells) and nano-rods (-wires) have gained special attention because of their promise for plasmon-based sensing, for catalysis, and for their enantioselectivity potential (biochemical separations). Determination of the detailed atomic and electronic structures is key to understanding size- and composition-dependent properties and evolutionary phenomena. In order to complement experimental structure-determinations, the theoretical investigation of low-energy atomic nanocages and nanorods is of fundamental importance for the predictive understanding of novel nanomaterials. In this work, I performed ab initio Density Functional Theory (DFT) calculations to systematically investigate the structural evolution and formation trends based on 60-atom Au nanocages and on finite ultra-thin noble-metal nanowires with different morphologies, diameter and length. Specifically, the stability study and fundamental properties of the novel and recently determined chiral-icosahedral Au60 nanoshell are presented. Structures based on the I-Au60 cage were proposed, and the results indicate this I-Au60 nanoshell is quite stable for it can be stabilized via different cores. For the case of the nanowires, I based structural models on detailed information collected, and generated 1D-repeated periodic patterns for analysis of atomic structure, comparative energetics, electronic density of states, and reciprocal space (structure factors), the latter being particularly useful for experimental comparison. This work should motivate the experimental synthesis of the I-Au60 nanoshell and I-Au60 shell-based nanostructures, as well as an alternative view on the growth mechanism of ultra-thin nanowires, where platonic solids act as building blocks.

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Physics and Astronomy