Processing Core/Alloy/Shell Nanoparticles: Tunable Optical Properties and Evidence for Self-Limiting Alloy Growth

Wu, Wenjie; Njoki, Peter N.; Han, Hyunjoo; Zhao, Hui; Schiff, E. A.; Lutz, Patrick; Solomon, Louis; Matthews, Seán; Maye, Mathew M.

doi:10.1021/jp201151m

Cited by 29 publications

(47 citation statements)

References 76 publications

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“…However when the size of the metal is comparable or smaller than the skin depth of microwave radiation, the energy of the electric field can pass through it and delivered to the substrate [39]. Our approach is based upon the annealing of the underlying Si substrate in a domestic microwave oven operating at 900 W, where ultrathin metal films (thinner or comparable to the skin depth and their percolation threshold [40]) have been grown.…”

Section: A Structural and Chemical Featuresmentioning

confidence: 99%

Self-assembled plasmonic templates produced by microwave annealing: applications to surface-enhanced Raman scattering

et al. 2015

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Perhaps the simplest method for creating metal nanoparticles on a substrate is by driving their selfassembly with the thermal annealing of a thin metal film. By properly tuning the annealing parameters one hopes to discover a recipe that allows the pre-determined design of the nanoparticle (NP) arrangement. However, thermal treatment is known for detrimental effects and is not really the manufacturer's route of choice when it comes to largescale applications. An alternative method is the use of microwave annealing, a method that has never been applied for metal processing, due to the high reflectance of microwave radiation at the surface of a metal. However, in this work we challenge the widely used nanostructuring methods by proving microwave's annealing ability to produce plasmonic templates, out of extremely thin metal films, by simply using a domestic microwave oven apparatus. We show that this process is generic and independent of the deposition method used for the metal and we further quantify the suitability of these plasmonic templates for use in surface-enhanced Raman scattering applications.

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Section: A Structural and Chemical Featuresmentioning

confidence: 99%

Self-assembled plasmonic templates produced by microwave annealing: applications to surface-enhanced Raman scattering

et al. 2015

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“…8c). 83 We can also consider that XPS showed a significant amount of Ni(acac) 2 remains unreacted in solution (inferred from the low%-compositions compared to feed ratios, Table 1), which suggests that galvanic exchange is the preferred route, since additional Ni(acac) 2 cannot exchange with the oxidized Fe 3 O 4 surface. To further test this, a control reaction was run that utilized the thermal decomposition of the zero-valent Ni(CO) 2 (PPh 3 ) 2 onto a-Fe.…”

Section: Resultsmentioning

confidence: 98%

The transformation of α-Fe nanoparticles into multi-domain FeNi–M₃O₄(M = Fe, Ni) heterostructures by galvanic exchange

et al. 2015

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In this work we describe a novel method to prepare multi-domain metal-metal oxide heterostructured nanoparticles (NPs). We investigated the ability of Ni(acac) 2 to undergo galvanic exchange with presynthesized metallic a-Fe NPs. Findings indicate that an asymmetric heterostructure emerges from the exchange, which is followed by rapid oxidation to form a NiFe-M 3 O 4 (M = Fe, Ni) alloy-oxide microstructure. Nucleation and growth was monitored using UV-vis and TEM, and crystal evolution, composition change, and oxidation states were measured by XRD and XPS respectively. Galvanic exchange and growth was studied by varying Ni : Fe molar feed ratios during synthesis. The findings indicate that at low Ni : Fe ratios, the NP forms multiple domains of oxides, whereas at higher ratios form regions with novel Ni-NiFe-M 3 O 4 interfaces. These new heterostructures were highly magnetic, and the extent of magnetization was proportional to composition and morphology, where NPs prepared at high Ni : Fe feed ratios resulted in decreased saturation magnetization and increased magnetic hysteresis. The nickel deposition and NP growth mechanism was considered as a combination of both galvanic exchange and reduction, and the observed rapid oxidation of the remaining a-Fe core was considered in light of electron density change at the heterostructures interfaces. Nanomaterials like these may find use as components in magnetic storage and spintronic devices, probes in biomedicine, additives in corrosion resistant coatings, and even as 3D printing inks.

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“…Surprisingly, the results of this analysis also showed a Pt 4f BE ≈ 72.4, 73.8, 75.19 and 77.7 eV corresponding to two 4f 7/2 and 4f 5/2 features each, strongly suggesting that both elemental and oxidized platinum species are present. 66,74 Unlike the Au/Pd-Pt system, the Au/Pd-Au had a smooth interface that could be in part due to the alloying of Au and Ag, and the lower affinity for Cl -. 73 It is important to note that the resolution of the XPS spectra were not optimized for analysis of oxidized species (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…[64][65][66][67][68] We hypothesized these NPs may be ideal substrates upon which to test the feasibility of combining heterostructure growth with galvanic exchange. [64][65][66][67][68] We hypothesized these NPs may be ideal substrates upon which to test the feasibility of combining heterostructure growth with galvanic exchange.…”

Section: Introductionmentioning

confidence: 99%

Heterostructured Au/Pd–M (M = Au, Pd, Pt) nanoparticles with compartmentalized composition, morphology, and electrocatalytic activity

2015

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The synthesis, processing, and galvanic exchange of three heterostructured nanoparticle systems is described. The surface accessibility and redox potential of a Au/Pd-Ag dumbbell nanoparticle, where a Au/Pd core/shell region, and a silver region make up the domains, was used to prepare the new nanostructures with controlled composition, morphology, and microstructure. Results indicate that the silver domain was particularly susceptible to galvanic displacement, and was exchanged to Au/Pd-M (M = Au, Pd, Pt). Interestingly, the dumbbell morphology remained after exchange, and the silver region was transformed to hollow, parachute, or concentric domains respectively. The morphology and microstructure change was visualized via TEM and HRTEM, and the composition changes were probed via STEM-EDS imaging and XPS. The electrocatalytic activity of the Au/Pd-M towards methanol oxidation was studied, with results indicating that the Au/Pd-Pt nanoparticles had high activity attributed to the porous nature of the platinum domains.

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Processing Core/Alloy/Shell Nanoparticles: Tunable Optical Properties and Evidence for Self-Limiting Alloy Growth

Cited by 29 publications

References 76 publications

Self-assembled plasmonic templates produced by microwave annealing: applications to surface-enhanced Raman scattering

Self-assembled plasmonic templates produced by microwave annealing: applications to surface-enhanced Raman scattering

The transformation of α-Fe nanoparticles into multi-domain FeNi–M₃O₄(M = Fe, Ni) heterostructures by galvanic exchange

Heterostructured Au/Pd–M (M = Au, Pd, Pt) nanoparticles with compartmentalized composition, morphology, and electrocatalytic activity

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Processing Core/Alloy/Shell Nanoparticles: Tunable Optical Properties and Evidence for Self-Limiting Alloy Growth

Cited by 29 publications

References 76 publications

Self-assembled plasmonic templates produced by microwave annealing: applications to surface-enhanced Raman scattering

Self-assembled plasmonic templates produced by microwave annealing: applications to surface-enhanced Raman scattering

The transformation of α-Fe nanoparticles into multi-domain FeNi–M3O4(M = Fe, Ni) heterostructures by galvanic exchange

Heterostructured Au/Pd–M (M = Au, Pd, Pt) nanoparticles with compartmentalized composition, morphology, and electrocatalytic activity

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The transformation of α-Fe nanoparticles into multi-domain FeNi–M₃O₄(M = Fe, Ni) heterostructures by galvanic exchange