Special Issue "Nanoporous Gold and Other Related Materials"

A special issue of Nanomaterials (ISSN 2079-4991).

Deadline for manuscript submissions: closed (30 April 2018)

Special Issue Editor

Guest Editor
Prof. Dr. Keith J. Stine

Department of Chemistry and Biochemistry, University of Missouri – Saint Louis, Saint Louis, MO 63121
Website | E-Mail
Interests: surface modification; nanomaterials; porous materials; electrochemistry; microscopy; carbohydrates; lipids; biosensors

Special Issue Information

Dear Colleagues,

Nanoporous gold and other related nanoporous metals or porous nanoparticle assemblies have gained a great deal of attention in recent years due to their novel chemical, optical, and mechanical properties. Nanoporous gold has found application as a support for biomolecules for biosensor development, as a catalyst for oxidation of small molecules, as a material with plasmonic properties useful for optical sensing, as a matrix for controlled release, as a mechanical actuator, and in other areas. Many studies have focused on tuning the porosity of the material, and on studying the relationship between the porosity and the mechanical properties of the material. The material provides a high surface area on which formation of self-assembled monolayers can be performed to impart recognition properties for molecular binding or transport. Nanoporous gold is part of a group of materials known as nanoporous metals which are generally formed by dealloying processes. Nanoporous forms of metals other than gold also have interesting catalytic and optical properties. Related materials with porosity can be formed through the large-scale assembly of nanoparticles. This Special Issue is devoted to the preparation, characterization and application of these nanomaterials.

Prof. Dr. Keith J. Stine
Guest Editor

Manuscript Submission Information

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Keywords

  • nanoporous gold
  • nanoporous metal
  • dealloying
  • catalysis
  • biomolecule immobilization
  • chemical sensor
  • biosensor

Published Papers (8 papers)

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Research

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Open AccessCommunication A Microfluidic Platform to Study Astrocyte Adhesion on Nanoporous Gold Thin Films
Nanomaterials 2018, 8(7), 452; https://doi.org/10.3390/nano8070452
Received: 14 May 2018 / Revised: 14 June 2018 / Accepted: 16 June 2018 / Published: 21 June 2018
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Abstract
Nanoporous gold (np-Au) electrode coatings have shown improved neural electrophysiological recording fidelity in vitro, in part due to reduced surface coverage by astrocytes. This reduction in astrocytic spreading has been attributed to the influence of electrode nanostructure on focal adhesion (FA) formation. This
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Nanoporous gold (np-Au) electrode coatings have shown improved neural electrophysiological recording fidelity in vitro, in part due to reduced surface coverage by astrocytes. This reduction in astrocytic spreading has been attributed to the influence of electrode nanostructure on focal adhesion (FA) formation. This study describes the development and use of a microfluidic flow cell for imposing controllable hydrodynamic shear on astrocytes cultured on gold surfaces of different morphologies, in order to study the influence of nanostructure on astrocyte adhesion strength as a function of np-Au electrode morphology. Astrocyte detachment (a surrogate for adhesion strength) monotonically increased as feature size was reduced from planar surfaces to np-Au, demonstrating that adhesion strength is dependent on nanostructure. Putative mechanisms responsible for this nanostructure-driven detachment phenomenon are also discussed. Full article
(This article belongs to the Special Issue Nanoporous Gold and Other Related Materials)
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Open AccessArticle (9R)-9-Hydroxystearate-Functionalized Anticancer Ceramics Promote Loading of Silver Nanoparticles
Nanomaterials 2018, 8(6), 390; https://doi.org/10.3390/nano8060390
Received: 3 May 2018 / Revised: 25 May 2018 / Accepted: 29 May 2018 / Published: 31 May 2018
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Abstract
Functionalization of calcium phosphates for biomedical applications has been proposed as a strategy to enrich the good osteoinductive properties of these materials with specific therapeutic characteristics. Herein, we prepared and characterized hydroxyapatite nanocrystals functionalized with an anticancer agent, (9R)-9-hydroxystearate (HSA), and
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Functionalization of calcium phosphates for biomedical applications has been proposed as a strategy to enrich the good osteoinductive properties of these materials with specific therapeutic characteristics. Herein, we prepared and characterized hydroxyapatite nanocrystals functionalized with an anticancer agent, (9R)-9-hydroxystearate (HSA), and loaded with an antimicrobial agent, namely silver nanoparticles (AgNPs). Nanocrystals at two different contents of HSA, about 4 and 9 wt %, were prepared via direct synthesis in aqueous solution. Loading with the antibacterial agent was achieved through interaction with different volumes of AgNPs suspensions. The amount of loaded nanoparticles increases with the volume of the AgNPs suspension and with the hydroxystearate content of the nanocrystals, up to about 3.3 wt %. The structural, morphological, and hydrophobic properties of the composite materials depend on hydroxystearate content, whereas they are not affected by AgNPs loading. At variance, the values of zeta potential slightly increase with the content of AgNPs, which exhibit a sustained release in cell culture medium. Full article
(This article belongs to the Special Issue Nanoporous Gold and Other Related Materials)
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Open AccessArticle High Temperature Flow Behavior of Ultra-Strong Nanoporous Au assessed by Spherical Nanoindentation
Nanomaterials 2018, 8(6), 366; https://doi.org/10.3390/nano8060366
Received: 30 April 2018 / Revised: 18 May 2018 / Accepted: 18 May 2018 / Published: 24 May 2018
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Abstract
Nanoporous metals have attracted attention in various research fields in the past years since their unique microstructures make them favorable for catalytic, sensory or microelectronic applications. Moreover, the refinement of the ligaments down to the nanoscale leads to an exceptionally high strength. To
[...] Read more.
Nanoporous metals have attracted attention in various research fields in the past years since their unique microstructures make them favorable for catalytic, sensory or microelectronic applications. Moreover, the refinement of the ligaments down to the nanoscale leads to an exceptionally high strength. To guarantee a smooth implementation of nanoporous metals into modern devices their thermo-mechanical behavior must be properly understood. Within this study the mechanical flow properties of nanoporous Au were investigated at elevated temperatures up to 300 °C. In contrast to the conventional synthesis by dealloying of AuAg precursors, the present foam was fabricated via severe plastic deformation of an AuFe nanocomposite and subsequent selective etching of iron, resulting in Au ligaments consisting of nanocrystalline grains, while remaining Fe impurities excessively stabilize the microstructure. A recently developed spherical nanoindentation protocol was used to extract the stress-strain curves of nanoporous Au. A tremendous increase of yield strength due to ligament and grain refinement was observed, which is largely maintained at high temperatures. Reviewing literature will evidence that the combined nanocrystalline and nanoporous structure leads to remarkable mechanical properties. Furthermore, comparison to a previous Berkovich nanoindentation study outlines the conformity of different indentation techniques. Full article
(This article belongs to the Special Issue Nanoporous Gold and Other Related Materials)
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Open AccessArticle Electrically Guided DNA Immobilization and Multiplexed DNA Detection with Nanoporous Gold Electrodes
Nanomaterials 2018, 8(5), 351; https://doi.org/10.3390/nano8050351
Received: 2 May 2018 / Revised: 17 May 2018 / Accepted: 18 May 2018 / Published: 21 May 2018
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Abstract
Molecular diagnostics have significantly advanced the early detection of diseases, where the electrochemical sensing of biomarkers (e.g., DNA, RNA, proteins) using multiple electrode arrays (MEAs) has shown considerable promise. Nanostructuring the electrode surface results in higher surface coverage of capture probes and more
[...] Read more.
Molecular diagnostics have significantly advanced the early detection of diseases, where the electrochemical sensing of biomarkers (e.g., DNA, RNA, proteins) using multiple electrode arrays (MEAs) has shown considerable promise. Nanostructuring the electrode surface results in higher surface coverage of capture probes and more favorable orientation, as well as transport phenomena unique to nanoscale, ultimately leading to enhanced sensor performance. The central goal of this study is to investigate the influence of electrode nanostructure on electrically-guided immobilization of DNA probes for nucleic acid detection in a multiplexed format. To that end, we used nanoporous gold (np-Au) electrodes that reduced the limit of detection (LOD) for DNA targets by two orders of magnitude compared to their planar counterparts, where the LOD was further improved by an additional order of magnitude after reducing the electrode diameter. The reduced electrode diameter also made it possible to create a np-Au MEA encapsulated in a microfluidic channel. The electro-grafting reduced the necessary incubation time to immobilize DNA probes into the porous electrodes down to 10 min (25-fold reduction compared to passive immobilization) and allowed for grafting a different DNA probe sequence onto each electrode in the array. The resulting platform was successfully used for the multiplexed detection of three different biomarker genes relevant to breast cancer diagnosis. Full article
(This article belongs to the Special Issue Nanoporous Gold and Other Related Materials)
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Open AccessArticle Novel Gold Dendritic Nanoforests Combined with Titanium Nitride for Visible-Light-Enhanced Chemical Degradation
Nanomaterials 2018, 8(5), 282; https://doi.org/10.3390/nano8050282
Received: 14 February 2018 / Revised: 23 April 2018 / Accepted: 24 April 2018 / Published: 26 April 2018
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Abstract
In this study, gold dendritic nanoforests (Au DNFs)-titanium nitride (TiN) composite was firstly proposed for visible-light photodegradation of pollutants. A high-power impulse magnetron sputtering system was used to coat TiN films on silicon wafers, and a fluoride-assisted galvanic replacement reaction was applied to
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In this study, gold dendritic nanoforests (Au DNFs)-titanium nitride (TiN) composite was firstly proposed for visible-light photodegradation of pollutants. A high-power impulse magnetron sputtering system was used to coat TiN films on silicon wafers, and a fluoride-assisted galvanic replacement reaction was applied to deposit Au DNFs on TiN/Si substrates. Scanning electron microscope images and X-ray diffraction patterns of TiN/Si, Au DNFs/Si, and Au DNFs/TiN/Si samples verified that this synthesis process was accurately controlled. The average reflectance of Au DNFs/Si and Au DNFs/TiN/Si considerably declined to approximately 10%, because the broadband localized surface plasmon resonances of Au DNFs cause broadband absorbance and low reflectance. In photocatalytic performance, 90.66 ± 1.41% 4-nitrophenol was successfully degraded in 180 min by Au DNFs/TiN/Si under visible-light irradiation. Therefore, Au DNFs/TiN/Si has the chance to be a visible-light photocatalyst for photodegradation of pollutants. Full article
(This article belongs to the Special Issue Nanoporous Gold and Other Related Materials)
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Open AccessArticle Constructing Asymmetric Polyion Complex Vesicles via Template Assembling Strategy: Formulation Control and Tunable Permeability
Nanomaterials 2017, 7(11), 387; https://doi.org/10.3390/nano7110387
Received: 23 September 2017 / Revised: 27 October 2017 / Accepted: 8 November 2017 / Published: 13 November 2017
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Abstract
A strategy for constructing polyion complex vesicles (PICsomes) with asymmetric structure is described. Poly(methylacrylic acid)-block-poly(N-isopropylacrylamide) modified gold nanoparticles (PMAA-b-PNIPAm-@-Au NPs) were prepared and then assembled with poly(ethylene glycol)-block-poly[1-methyl-3-(2-methacryloyloxy propylimidazolium bromine)] (PEG-b-PMMPImB) via polyion
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A strategy for constructing polyion complex vesicles (PICsomes) with asymmetric structure is described. Poly(methylacrylic acid)-block-poly(N-isopropylacrylamide) modified gold nanoparticles (PMAA-b-PNIPAm-@-Au NPs) were prepared and then assembled with poly(ethylene glycol)-block-poly[1-methyl-3-(2-methacryloyloxy propylimidazolium bromine)] (PEG-b-PMMPImB) via polyion complex of PMMA and PMMPImB. After removing the Au NPs template, asymmetric PICsomes composed of a PNIPAm inner-shell, PIC wall, and PEG outer-corona were obtained. These PICsomes have low protein absorption and thermally tunable permeability, provided by the PEG outer-corona and the PNIPAm inner-shell, respectively. Moreover, PICsome size can be tailored by using templates of predetermined sizes. This novel strategy for constructing asymmetric PICsomes with well-defined properties and controllable size is valuable for applications such as drug delivery, catalysis and monitoring of chemical reactions, and biomimetics. Full article
(This article belongs to the Special Issue Nanoporous Gold and Other Related Materials)
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Open AccessArticle Controlling the Mechanical Properties of Bulk Metallic Glasses by Superficial Dealloyed Layer
Nanomaterials 2017, 7(11), 352; https://doi.org/10.3390/nano7110352
Received: 20 September 2017 / Revised: 19 October 2017 / Accepted: 23 October 2017 / Published: 27 October 2017
Cited by 1 | PDF Full-text (7188 KB) | HTML Full-text | XML Full-text
Abstract
Cu50Zr45Al5 bulk metallic glass (BMG) presents high fracture strength. For improving its plasticity and controlling its mechanical properties, superficial dealloying of the BMG was performed. A composite structure containing an inner rod-shaped Cu-Zr-Al amorphous core with high strength
[...] Read more.
Cu50Zr45Al5 bulk metallic glass (BMG) presents high fracture strength. For improving its plasticity and controlling its mechanical properties, superficial dealloying of the BMG was performed. A composite structure containing an inner rod-shaped Cu-Zr-Al amorphous core with high strength and an outer dealloyed nanoporous layer with high energy absorption capacity was obtained. The microstructures and mechanical properties of the composites were studied in detail. It was found, for the first time, that the mechanical properties of Cu50Zr45Al5 BMG can be controlled by adjusting the width of the buffer deformation zone in the dealloyed layer, which can be easily manipulated with different dealloying times. As a result, the compressive strength, compressive strain, and energy absorption capacity of the BMGs can be effectively modulated from 0.9 to 1.5 GPa, from 2.9% to 4.7%, and from 29.1 to 40.2 MJ/m3, respectively. The paper may open a door for developing important engineering materials with regulable and comprehensive performances. Full article
(This article belongs to the Special Issue Nanoporous Gold and Other Related Materials)
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Review

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Open AccessFeature PaperReview Preparation, Modification, Characterization, and Biosensing Application of Nanoporous Gold Using Electrochemical Techniques
Nanomaterials 2018, 8(3), 171; https://doi.org/10.3390/nano8030171
Received: 24 February 2018 / Revised: 13 March 2018 / Accepted: 13 March 2018 / Published: 16 March 2018
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Abstract
Nanoporous gold (np-Au), because of its high surface area-to-volume ratio, excellent conductivity, chemical inertness, physical stability, biocompatibility, easily tunable pores, and plasmonic properties, has attracted much interested in the field of nanotechnology. It has promising applications in the fields of catalysis, bio/chemical sensing,
[...] Read more.
Nanoporous gold (np-Au), because of its high surface area-to-volume ratio, excellent conductivity, chemical inertness, physical stability, biocompatibility, easily tunable pores, and plasmonic properties, has attracted much interested in the field of nanotechnology. It has promising applications in the fields of catalysis, bio/chemical sensing, drug delivery, biomolecules separation and purification, fuel cell development, surface-chemistry-driven actuation, and supercapacitor design. Many chemical and electrochemical procedures are known for the preparation of np-Au. Recently, researchers are focusing on easier and controlled ways to tune the pores and ligaments size of np-Au for its use in different applications. Electrochemical methods have good control over fine-tuning pore and ligament sizes. The np-Au electrodes that are prepared using electrochemical techniques are robust and are easier to handle for their use in electrochemical biosensing. Here, we review different electrochemical strategies for the preparation, post-modification, and characterization of np-Au along with the synergistic use of both electrochemistry and np-Au for applications in biosensing. Full article
(This article belongs to the Special Issue Nanoporous Gold and Other Related Materials)
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