Void formation during early stages of passivation: Initial oxidation of iron nanoparticles at room temperature

Wang, C. M.; Baer, Donald R.; Thomas, L.; Amonette, J. E.; Antony, Jiji; Qiang, You; Duscher, Gerd

doi:10.1063/1.2130890

Cited by 256 publications

(293 citation statements)

References 37 publications

Supporting

Mentioning

264

Contrasting

Unclassified

Order By: Relevance

“…temperature. 8 This process can be accelerated by taking advantage of the exponential temperature dependence of the iron diffusivities. As a result, the reaction temperature and oxidation time allow to precisely tune the thickness of an initial oxide shell.…”

mentioning

confidence: 99%

“…These results are consistent with a previous study on the room-temperature oxidation of iron clusters supported on carbon grids. 8 The nanoscale Kirkendall effect was initially described for reactions of Co nanoparticles with oxygen, sulfur, and selenium. 10 Careful TEM investigation of cobalt nanoparticles oxidized with selenium revealed thin filamentous connections between the shell and the central metal particle.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Vacancy Coalescence during Oxidation of Iron Nanoparticles

et al. 2007

View full text Add to dashboard Cite

Supporting Information Available: Detailed synthesis and experimental procedures, UV-vis, XRD, and XAS of the iron/iron oxide nanoparticles, SQUID of the final iron oxide shells, histograms of the particle sizes, and analysis of the electron beam influence during TEM imaging and of the high-temperature oxidation of the particles in solution. This material is available free of charge via the Internet at

show abstract

mentioning

confidence: 99%

mentioning

confidence: 99%

Vacancy Coalescence during Oxidation of Iron Nanoparticles

et al. 2007

View full text Add to dashboard Cite

show abstract

“…This general methodology has since been extended by other groups to produce nanostructures with various compositions and shapes. [7][8][9][10] Galvanic replacement reactions have been demonstrated to also produce hollow nanostructures. Xia et al reported cases where a replacement reaction took place uniformly around Ag cubes of ~100 nm size, leading to formation of Au nanoboxes.…”

mentioning

confidence: 99%

Faceting of Nanocrystals during Chemical Transformation: From Solid Silver Spheres to Hollow Gold Octahedra

et al. 2006

View full text Add to dashboard Cite

Sustained progress in nanocrystal synthesis has enabled recent use of these materials as inorganic, macromolecular precursors that can be chemically transformed into new nanostructures. 1, 2 The literature now contains several cases with chemical transformations being accompanied by varying degrees of modification of properties, including crystal structure and particle shape. [3][4][5] As a recent example, we demonstrated that as-synthesized metallic nanocrystals yield, upon oxidation, nanostructures with modified morphologies such as hollow particles. 6 This morphological change derives from directional material flows due to differing diffusivities for the reacting atomic species, in a nanoscale version of the well-known Kirkendall Effect. This general methodology has since been extended by other groups to produce nanostructures with various compositions and shapes. [7][8][9][10] Galvanic replacement reactions have been demonstrated to also produce hollow nanostructures. Xia et al. reported cases where a replacement reaction took place uniformly around Ag cubes of ~100 nm size, leading to formation of Au nanoboxes. The exterior shape of the nanoboxes tends to largely reproduce that of the sacrificial Ag counterparts. 11-15 Here, we report that performing the same replacement reaction on silver nanocrystals that are an order of magnitude smaller leads to significant changes in the external morphology of the Au shells as the reaction proceeds, while still creating a central void in each particle. Specifically, single crystalline silver nanoscrystals with a spherical shape act in the presence of Au 3+ as precursors for formation of hollow Au nanocrystals with truncated octahedral shape. The growth of significantly faceted particles from spherical precursors is made possible by the enhanced role of surface effects in our smaller nanocrystals. Production of hollow Au nanocrystals with faceted geometry allows increased tunability of optical properties as the surface plasmon resonance spectra of a hollow metallic nanocrystal depends strongly not only on the shell thickness, but also on the detailed shape. 16,17 To produce Ag nanocrystals with reduced sizes and improved monodispersity, we performed the synthesis using a modification of the polyol process in an organic solvent and at high temperature. 6,18 The silver salt AgNO 3 was reduced by a long chain polyol such as 1,2-hexadecanediol using an organic solvent, o-dichlorobenzene (DCB). Oleylamine was present as a surfactant. Near instant formation of silver nanocrystals upon reaction was indicated by the originally colorless solution turning dark brown. The transformation of solid nanocrystals into hollow ones was performed through galvanic replacement by dropwise addition of gold (III) chloride solution to diluted silver colloidal solution until the solution changed in color from dark yellow to blue. In this reaction, oleylamine likely serves two purposes. First, it solubilizes the precursors AgNO 3 and AuCl 3 in DCB. Second, it acts as a surfactant that controls t...

show abstract

“…The AFM measurements are performed in tapping mode at ambient conditions and therefore include the effects of oxidation. 28 At 500°C, the NH 3 annealed Fe film (Figure 2b) shows smaller average island dimensions than for vacuum annealing (Figure 2a). Within the limits of the AFM analysis, annealing in NH 3 at 300°C results in cluster sizes (Figure 2c) similar to the distribution at 500°C (Figure 2b).…”

mentioning

confidence: 99%

Catalytic Chemical Vapor Deposition of Single-Wall Carbon Nanotubes at Low Temperatures

et al. 2006

View full text Add to dashboard Cite

We report surface-bound growth of single-wall carbon nanotubes (SWNTs) at temperatures as low as 350°C by catalytic chemical vapor deposition from undiluted C 2 H 2 . NH 3 or H 2 exposure critically facilitates the nanostructuring and activation of sub-nanometer Fe and Al/Fe/Al multilayer catalyst films prior to growth, enabling the SWNT nucleation at lower temperatures. We suggest that carbon nanotube growth is governed by the catalyst surface without the necessity of catalyst liquefaction.Carbon nanotubes (CNTs) have been a driving force for current advances in nanotechnology, both on an applied and on a fundamental level. Single-wall carbon nanotubes have shown the highest Young's modulus and highest axial thermal conductivity of any solid. Moreover, SWNTs have the highest current carrying capacity of any conductor, which makes them an attractive electronic, sensing, or heat sinking material for nano-electromechanical systems (NEMS) and future (hybrid) integrated circuitry. 1,2Defect-free SWNT synthesis is generally thought to require high temperatures (T). 3 This belief arises from the success of high-T deposition processes. Arc-discharge, laser ablation, and high-pressure CO conversion with inherent (local) temperatures in the order of 1000-4000°C have been optimized mainly for bulk CNT production. 3 For device fabrication, these techniques heavily rely on purification from other carbon allotropes and an indirect postgrowth assembly via stable suspensions. In comparison, catalytic chemical vapor deposition (CVD) allows selective, aligned CNT growth directly onto a substrate and thus presently is the only economically viable process for integrating CNTs into a device. 1,[4][5][6] This approach, however, exposes the substrate to the CNT growth temperature and atmosphere, which creates a need for less aggressive, low T processing conditions. Present back-end CMOS technology allows a maximum temperature of 400-450°C, the limit being set by the mechanical integrity of low dielectric constant intermetal dielectrics. 7 Thermal CVD of SWNTs has been reported at 550°C in furnace 8 and cold wall systems. 9 In situ environmental transmission electron microscopy (TEM) experiments show SWNT nucleation at 480°C. 10 Random-network FETs have been fabricated with SWNTs grown at 450°C by remote plasma-enhanced (PE) CVD.11 However, the high temperatures of bulk production techniques still dominate growth model considerations with the assumption that the catalyst cluster has to be liquefied and that the catalyst bulk is ratecontrolling.12,13 These considerations are also transferred to surface-bound CVD. 14 CNT growth below 500°C is not thought to be possible based on calculations of size-corrected melting points 14 and carbon saturation. 15In this Letter, we report SWNT growth at temperatures below 450°C by thermal CVD at cold wall conditions and demonstrate field effects in as-integrated SWNT FETs. We use evaporated thin catalyst films, which allow accurate patterning by standard lithography techniques and thus compa...

show abstract

Void formation during early stages of passivation: Initial oxidation of iron nanoparticles at room temperature

Cited by 256 publications

References 37 publications

Vacancy Coalescence during Oxidation of Iron Nanoparticles

Vacancy Coalescence during Oxidation of Iron Nanoparticles

Faceting of Nanocrystals during Chemical Transformation: From Solid Silver Spheres to Hollow Gold Octahedra

Catalytic Chemical Vapor Deposition of Single-Wall Carbon Nanotubes at Low Temperatures

Contact Info

Product

Resources

About