Kinetic description of metal nanocrystal oxidation: a combined theoretical and experimental approach for determining morphology and diffusion parameters in hollow nanoparticles by the nanoscale Kirkendall effect

Abstract

2014) Kinetic description of metal nanocrystal oxidation: a combined theoretical and experimental approach for determining morphology and diffusion parameters in hollow nanoparticles by the nanoscale Kirkendall effect, Philosophical Magazine, 94:30,[3487][3488][3489][3490][3491][3492][3493][3494][3495][3496][3497][3498][3499][3500][3501][3502][3503][3504][3505][3506] The oxidation of colloidal metal nanocrystals to form hollow shells via the nanoscale Kirkendall effect has been investigated using a combined theoretical and experimental approach. A generalized kinetic model for the formation of hollow nanoparticles describes the phenomenon and, unlike prior models, is applicable to any material system and accounts for the effect of surface energies. Phase diagrams of the ultimate oxidized nanoparticle morphology and the time to achieve complete oxidation are calculated, and are found to depend significantly upon consideration of surface energy effects that destabilize the initial formation of small voids. For the oxidation of Cu nanocrystals to Cu 2 O nanoparticles, we find that the diffusion coefficients dictate the morphological outcomes: the ratio of D oxygen in Cu2O to D Cu in Cu controls the void size, D Cu in Cu determines the time of oxidation and D Cu in Cu2O is largely irrelevant in the kinetics of oxidation. The kinetic model was used to fit experimental measurements of 11 nm diameter Cu nanocrystals oxidized in air from which temperature-dependent diffusivities of D oxygen in Cu2O ¼ 90 expðÀ43=R g T Þ nm 2 =s ð Þ and D Cu in Cu ¼ 6 expðÀ30=R g TÞ nm 2 =s ð Þ for 100 ≤ T ≤ 200°C were determined. In contrast to previous interpretations of the nanoscale Kirkendall effect in the Cu/Cu 2 O system, these results are obtained without any a priori assumptions about the relative magnitudes of D Cu in Cu and D Cu in Cu2O . The theoretical and experimental approaches presented here are broadly applicable to any nanoparticle system undergoing oxidation, and can be used to precisely control the final nanoparticle morphology for applications in catalysis or optical materials.

Heterodimers for in Situ Plasmonic Spectroscopy: Cu Nanoparticle Oxidation Kinetics, Kirkendall Effect, and Compensation in the Arrhenius Parameters

“…Inspecting SEM images ( Figure 3 b,c) of the same sample together with TEM micrographs obtained before and after identical oxidation treatment of a sample-analogue fabricated on a TEM membrane ( Figure 3 b,c—insets and Figure S1 ) reveals the formation of a central Kirkendall void during oxidation and a corresponding increase of the particle size ( Figure S1 ), in good agreement with earlier observations of the NKE. 4 , 9 , 14 , 30 …”

“… 26 Furthermore, the available oxidation studies focused on Cu nanoparticles indicate that they, in analogy with other metals, 2 , 6 , 27 , 28 often exhibit the so-called nanoscale Kirkendall effect (NKE), as a result of Cu-ions diffusing faster in the oxide compared with O-ions. 4 , 9 , 14 , 29 , 30 This results in the formation of a characteristic hollow oxide shell, with the amount of hollowness depending on the ratio between the diffusion rates of Cu- and O-ions, as well as on the oxide structure.…”

Fitting A Square Peg into A Round Hole: Shape Control in Phase Transfer of Cubic Gold Nanoparticles

“…A characteristic feature of gold nanoparticles is a surface plasmon resonance in the visible range of the light, which depends, amongst others, on the element, the size and shape of the metal core, [1–4] as well as the dielectric properties of the surrounding medium [5–9] . Besides, gold exhibits a relatively high chemical stability, which enables long storage of nanoparticle dispersions and is therefore crucial for most applications [10,11] .…”

Review on Theoretical Models of Void Evolution in Crystalline Particles

“…TEP was employed to investigate the void formation in metallic particles due to oxidation [112][113][114].…”