Solution-Phase Growth of Cu Nanowires with Aspect Ratios Greater Than 1000: Multiscale Theory

Abstract

Penta-twinned metal nanowires are finding widespread application in existing and emerging technologies. However, little is known about their growth mechanisms. We probe the origins of chloride- and alkylamine-mediated, solution-phase growth of penta-twinned Cu nanowires from first-principles using multiscale theory. Using quantum density functional theory (DFT) calculations, we characterize the binding and surface diffusion of Cu atoms on chlorine-covered Cu(100) and Cu(111) surfaces. We find stronger binding and slower diffusion of Cu atoms on chlorinated Cu(111) than on chlorinated Cu(100), which is a reversal of the trend for bare Cu surfaces. We also probe interfacet diffusion and find that this proceeds faster from Cu(100) to Cu(111) than the reverse. Using the DFT rates for hopping between individual sites at Ångstrom scales, we calculate coarse-grained, interfacet rates for nanowires of various lengthsup to hundreds of micrometersand diameters in the 10 nm range. We predict nanowires with aspect ratios of ∼100, based on surface diffusion alone. We also account for the influence of a self-assembled alkylamine layer that covers most of the {100} facets, but is absent or thin and disordered on the {111} facets and in an “end zone” near the {100}/{111} boundary. With an end zone, we predict a wide range of nanowire aspect ratios in the experimental ranges. Our work reveals the mechanisms by which a halidechloridepromotes the growth of high-aspect-ratio nanowires.

The influence of iodide on the solution-phase growth of Cu microplates: a multi-scale theoretical analysis from first principles

“…Moreover, plates can take on a variety of shapes during growth: from triangular and truncated triangular to round and hexagonal. Though the diffusion of Cu atoms is slower on I-covered Cu(111) than on the bare surface, 46 it is still relatively rapid and, as we showed in our absorbing Markov chain calculations, it is rapid enough to promote lateral growth of microplates with dimensions in the 1–10 micron range. Therefore, we conclude the adsorption of iodine on Cu surfaces favors the anisotropic growth of thin Cu plates by influencing on both seed formation and growth stages.…”

“…42,43 We used (and explained) this method in prior work. [44][45][46] Briey, we solve for the average time, considering all possible deposition sites, for a Cu atom deposited on a basal {111} facet to diffuse to a side facet. This involves constructing a Markov matrix to characterize the network of diffusion rates for site-to-site hops/exchanges.…”

Three-Step, Seed-Mediated Synthesis of Ultrathin AgNWs in Aqueous Solution

“…In this case, the established Ag 0 reduction rate for growing AgNRs is too higher than that for the growth of AgNWs at a less concentration of seed. Therefore, a lower reduction rate of Ag 0 might be able to satisfy the further longitudinal growth of AgNRs. , For this reason, HNO 3 was introduced into the AgNR seeding solution to lower the pH value and decrease the reaction kinetics for forming Ag 0 by attenuating the reducing capability of AA. To minimize the effects of other experimental conditions, the nominal concentrations of each chemical added are very close to those established in preparing AgNR seeds.…”

Asymmetric Interfacet Adatom Migration as a Mode of Anisotropic Nanocrystal Growth

“…In this case, asymmetry in adatom diffusion can be described by the Boltzmann factor e Δ/ k B T , where Δ = E down – E up . For bare fcc surfaces, Δ > 0 because they exhibit greater rates of {111}-to-{100} diffusion than the reverse. , However, modifications to bare fcc surfaces, such as by surface ligands and lattice strain, have been shown to influence surface dynamics. ,− XPS showed that our Au nanorods were not bare during solution-phase growth but covered, including sparsely with Cl (Figure S8a). Our experiments were then analogous to the solution-phase growth of Cl-covered pentatwinned nanorods composed of another fcc metal, Cu, for which DFT calculations predict that {100}-to-{111} interfacet diffusion predominates (Δ < 0) .…”

“…Our experiments were then analogous to the solution-phase growth of Cl-covered pentatwinned nanorods composed of another fcc metal, Cu, for which DFT calculations predict that {100}-to-{111} interfacet diffusion predominates (Δ < 0). 65 To examine if Cl controlled the extent of anisotropic growth or if it was supersaturation as indicated in Figure 3h,i, we replaced HCl with 160 equiv of HNO 3 in the growth formulation. This reaction yielded only nanodecahedra and low-AR nanorods as the pentatwinned products (Figure S35), with supersaturation dynamics comparable to the reaction with 40 equiv of HCl (Figure 3f); both results were consistent with the lesser influence of only H + when compared to that of both H + and Cl − to the supersaturation dynamics (Figure S6a).…”