Size‐Dependent Room Temperature Oxidation of Tin Particles

Abstract

879wileyonlinelibrary.com www.particle-journal.com www.MaterialsViews.com Using transmission electron microscopy, the size-dependent room temperature oxidation of tin nanoparticles is studied. The oxide that forms during room temperature oxidation of Sn particles is amorphous SnO, and it retains this stoichiometry and structure over extended time periods. From the investigation of arrays of Sn nanoparticles with broad size distribution, under identical conditions, the Sn oxide thickness is evaluated as a function of size and oxidation time. The oxide thickness depends strongly on the size of the Sn nanoparticles, which is in excellent agreement with predictions for a Mott-Cabrera model corrected for a non-uniform electric fi eld. The results demonstrate the accelerated oxidation kinetics of nanoscale particles with high curvature, due to the amplifi ed electric fi eld at the interface to a continuously shrinking metal core.Here, we consider the room temperature oxidation of Sn nanoparticles, focusing in particular on possible nanoparticle size effects on the oxidation rate, as well as the structure and stoichiometry of the resulting oxide. Sn nanoparticles, invariably terminated by either SnO 2 or SnO following their exposure to air, are of interest for a wide range of applications, for example gas sensors, [ 4 ] optoelectronic devices and solar cells, [ 5 ] and Li-ion battery anodes. [ 6 ] Gas sensors often show an unwanted long-term drift in their sensing characteristics while operating in air near room temperature, generally attributed to oxygen diffusion into the oxide. [ 7 ] SnO 2 or Sn-SnO 2 core-shell nanostructures, produced by complete or partial oxidation of fi lms of Sn clusters, [ 8 ] Sn particles, [ 4a,b , 9 ] and nanowires, [ 7,10 ] provide high sensitivity [ 9,11 ] and fast response in gas sensing applications, [ 12 ] but are usually characterized by a large spread in sizes. [ 4a,b , 13 ] Hence, a size-dependent oxidation rate will give rise to non-uniform oxide thickness, which will impact the sensing characteristics. The thickness of a native Sn-oxide shell also critically affects the application of Sn nanoparticles as a Li-ion battery anode material, where the surface oxide causes a decrease in the reversible Li-ion capacity due to an irreversible fi rst-discharge reaction to Li 2 O. Naturally, possible size effects on the oxidation rate would be expected to be important in polydisperse Sn nanoparticle ensembles. [ 9,14 ] However, even precise colloidal synthesis protocols developed recently, capable of generating monodisperse Sn (or Sn-Sn oxide) nanocrystals with size spread below 10%, [ 6 ] may not be suffi cient to eliminate nonuniform oxides. Indeed, clear differences observed in the native oxide thickness for colloidal Sn particles at the low and high ends of a 10% size distribution [ 6 ] suggest the existence of very strongly size-dependent effects in the oxidation of Sn, which are important to applications in energy storage and others.Despite several decades of fundamental research ...

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“…45 Room temperature oxidation of Sn nanoparticles forms a Sn(II)-oxide shell. 43 Hence, we assign the Sn 3d 5/2 peak at B487 eV to Sn 2+ in both the Sn reference and AuSn, which is supported by a quantitative analysis of Sn 3d 5/2 and O 1s XPS spectra (see ESI †) that yields an Sn:O ratio close to 1 in the oxide. A major difference between AuSn and Sn lies in the evolution of oxidized Sn (Fig.…”

“…After extended air exposure Sn nanoparticles are covered by B5 nm oxide shells. 43 For AuSn, little additional oxidation is observed beyond a limiting oxide thickness of 1.5 to 2 nm. Hence, AuSn alloys are substantially more oxidation resistant than pure Sn.…”

Stable Self-Assembled Atomic-Switch Networks for Neuromorphic Applications

“…By controlling oxidation and humidity during NP deposition, nanoparticle coalescence is inhibited resulting in stochastic switching that is stable over several months. The atomic-wire formation in these oxidised nanostructures is very surprising and detailed modeling [63] of the atomistic mechanisms [39], [51], [52] in the presence of oxides [54], [55] is required, as is atomic scale modelling of the effect of humidity [53] on the oxidation process.…”

“…[53] Studies of oxidation of Sn in conditions similar to the present ones show that only partial surface oxides are formed. [54], [55] Ex-situ analysis of the present oxide-structure is obviously not feasible and so instead we have investigated in-situ the device stability over several weeks. Fig.…”

Understanding the Sn Loading Impact on the Performance of Mesoporous Carbon/Sn‐Based Nanocomposites in Li‐Ion Batteries

“…The amount of formed SnO 2 may be explained by two factors, i. e., the particle size and particle location in the carbon network. On one hand, the Sn crystallites size increases from 67 nm to 148 nm ( Table 2) when increasing the loading from 20 to 80 % and the oxidation tendency generally increases with the decrease of the particle/crystallite size, [25,31] However, starting with 60 % of loading, a slight increase of SnO 2 amount is observed (Table 2) and this may be probably related to the higher amount of agglomerated Sn particles situated on the carbon surface, therefore, not confined in carbon pores (Figure 2) and more exposed to oxidation.…”