Thermal coarsening of nanoporous gold: Melting or recrystallization

Hakamada, Masataka; Mabuchi, Mamoru

doi:10.1557/jmr.2009.0037

Cited by 52 publications

(50 citation statements)

References 23 publications

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“…In this process, selective removal of silver atoms from a silver-rich gold alloy, accompanied by surface diffusion of gold atoms at the metal-electrolyte interface, results in an open-cell structure with interconnected ligaments of tens of nanometers [22,23]. Alloy composition [24] and preparation approach, dealloying method [25][26][27], and post-processing techniques [28,29] all influence pore morphology, resulting in a wide range of possible pore and ligament sizes ranging from tens of nanometers [25] up to several hundred of nanometers [23]. When np-Au films are subjected to homogenous thermal treatment (such as in annealing furnaces), pore and ligament sizes increase in a uniform fashion across the entire sample due to enhanced diffusion of surface atoms [23].…”

Section: Template For Preparation Of Manuscripts For Nano Researchmentioning

confidence: 99%

Electrically tunable pore morphology in nanoporous gold thin films

Dorofeeva

Şeker

2015

Nano Res.

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Electrical current is used for tuning pore morphology of nanoporous gold thin films at significantly lower temperatures than previously reported via electrically-assisted mechanisms.This technique allows for precisely controlling the extent and location of pore coarsening and producing a wide range of distinct morphologies on a single substrate for high-throughput studies of structure-property relationships. ABSTRACTNanoporous gold (np-Au) is an emerging nanostructured material that exhibits many desirable properties, including high electrical and thermal conductivity, high surface area-to-volume ratio, tunable pore morphology, well-established surface-binding chemistry, and compatibility with microfabrication. These features made np-Au a popular material for fuel cells, optical and electrical biosensors, drug delivery vehicles, neural electrode coatings, and as a model system for nano-scale mechanics. In each application, np-Au morphology plays an essential role in the overall device operation. Therefore, precise control of morphology is necessary for attaining optimal device performance. Traditionally, thermal treatment in furnaces and on hot plates is used for obtaining np-Au with self-similar but coarser morphologies. However, this approach lacks the ability to create different morphologies on a single substrate and requires high temperatures (>250 °C) that are not compatible with most plastic substrates. Herein, we report electro-annealing as a method that for the first time makes it possible to control the extent and location of pore coarsening on a single substrate with one fast treatment step. In addition, the electro-annealing entails much lower temperatures (<150 °C) than traditional thermal treatment, putatively due to electrically-assisted phenomena that contribute to thermally-activated surface diffusion of gold atoms responsible for coarsening. Overall, this approach can be easily scaled up to display multiple pore morphologies on a single chip and therefore enable high-throughput screening of optimal nanostructures for specific applications.

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Section: Template For Preparation Of Manuscripts For Nano Researchmentioning

confidence: 99%

Electrically tunable pore morphology in nanoporous gold thin films

Dorofeeva

Şeker

2015

Nano Res.

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“…Dealloying variables such as the concentration of the acid, length of time in the acid solution, applied potential, and temperature of the etchant solution are particularly important [15]. Posttreatments include thermal and acid treatment [9,15,67,103]. One means to decrease pore size while keeping the ligament size nearly the same is via the electroless plating of gold into the internal surfaces of nanoporous gold [104,105].…”

Section: Specific Features Of Nanoporous Goldmentioning

confidence: 99%

Nanoporous Gold Electrodes and Their Applications in Analytical Chemistry

Collinson

2013

ISRN Analytical Chemistry

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Nanoporous gold prepared by dealloying Au:Ag alloys has recently become an attractive material in the field of analytical chemistry. This conductive material has an open, 3D porous framework consisting of nanosized pores and ligaments with surface areas that are 10s to 100s of times larger than planar gold of an equivalent geometric area. The high surface area coupled with an open pore network makes nanoporous gold an ideal support for the development of chemical sensors. Important attributes include conductivity, high surface area, ease of preparation and modification, tunable pore size, and a bicontinuous open pore network. In this paper, the fabrication, characterization, and applications of nanoporous gold in chemical sensing are reviewed specifically as they relate to the development of immunosensors, enzyme-based biosensors, DNA sensors, Raman sensors, and small molecule sensors.

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“…NPG exhibits an open-cell nanoscale network structure with a well-defined characteristic size of the metal phase, the so-called ligaments. These can be scaled ranging from as small as 5 nm up to 1 μm [17][18][19][20][21] so that NPG established as a model system for the investigation of nanoscale materials behavior.…”

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confidence: 99%

Nanoporous Gold by Alloy Corrosion: Method-Structure-Property Relationships

Graf

Roschning

Weißmüller

2017

J. Electrochem. Soc.

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Nanoporous gold (NPG) made by selective corrosion, or dealloying, serves as a model system for the investigation of electrochemical and mechanical properties of nanomaterials. While various dealloying protocols are in use, it is typically assumed that the structural characteristics are identical and independent of the preparation technique. Yet, reported properties such as strength, Young's modulus, or catalytic behavior can vary widely. Here, we compare the microstructure and the mechanical behavior of NPG structures prepared by three different synthesis protocols reported in the literature. We find that corrosion rates, the content of residual sacrificial metal, the average ligament size and the densification by shrinkage strongly depend on the synthesis protocol and show the consequences on the mechanical properties. NPG exhibits an open-cell nanoscale network structure with a well-defined characteristic size of the metal phase, the so-called ligaments. These can be scaled ranging from as small as 5 nm up to 1 μm 17-21 so that NPG established as a model system for the investigation of nanoscale materials behavior.Studies of the catalytic or mechanical behavior of NPG by different authors do not report consistent observations in all instances. The role of the residual sacrificial metal content as an origin for the remarkable catalytic activity (e.g. for CO oxidation) is under discussion. 22-25As another instance, reports on the mechanical strength and stiffness of nominally comparable structures disagree by up to one order of magnitude. 26,27 Therefore it is significant to note that a number of different dealloying protocols are applied within these studies. Conceivably, diverging observations on the material's behavior may be related to the impact of these protocols on the microstructure. Here, we explore this issue by comparing the microstructures of NPG made by three common preparation routes.The elementary steps of dealloying are the removal of atoms of the less noble element from the parent phase and the redistribution of the nobler element atoms on the crystal lattice by surface diffusion. 21This creates a network structure, typically with sizes between 5 and 20 nm. 28,29 When assuming complete removal of the less noble element from a parent alloy (e.g. Ag x Au 1-x which is composed of similarly sized atoms), the solid volume fraction, ϕ, of the porous structure will ideally agree with the atom fraction of the more noble element in the master alloy. Yet, the shrinkage during dealloying may reduce the external sample dimensions, thereby increasing ϕ.29 Structural coarsening begins during dealloying 28 and its rate is affected e.g. by the composition of the electrolyte, 30 additional alloy elements 31,32 or the temperature. 33 These observations emphasize that details of the dealloying process may have a substantial effect on the microstructure of the nanoporous material. Table I lists several synthesis protocols for NPG; these are often implicitly expected to result in similar structures. As the object of...

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Thermal coarsening of nanoporous gold: Melting or recrystallization

Cited by 52 publications

References 23 publications

Electrically tunable pore morphology in nanoporous gold thin films

Electrically tunable pore morphology in nanoporous gold thin films

Nanoporous Gold Electrodes and Their Applications in Analytical Chemistry

Nanoporous Gold by Alloy Corrosion: Method-Structure-Property Relationships

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