Publications by authors named "Gilles R Bourret"

19 Publications

  • Page 1 of 1

Large-Scale Synthesis of Highly Uniform Silicon Nanowire Arrays Using Metal-Assisted Chemical Etching.

Chem Mater 2020 Nov 26;32(21):9425-9434. Epub 2020 Oct 26.

Department of Chemistry and Physics of Materials, University of Salzburg, Jakob Haringer Strasse 2A, A-5020 Salzburg, Austria.

The combination of metal-assisted chemical etching (MACE) with colloidal lithography has emerged as a simple and cost-effective approach to nanostructure silicon. It is especially efficient at synthesizing Si micro- and nanowire arrays using a catalytic metal mesh, which sinks into the silicon substrate during the etching process. The approach provides a precise control over the array geometry, without requiring expensive nanopatterning techniques. Although MACE is a high-throughput solution-based approach, achieving large-scale homogeneity can be challenging because of the instability of the metal catalyst when the experimental parameters are not set appropriately. Such instabilities can lead to metal film fracture, significantly damaging the substrate and thus compromising the nanowire array quality. Here, we report on the critical parameters that influence the stability of the metal catalyst layer for achieving large-scale homogeneous MACE: etchant composition, metal film thickness, adhesion layer thickness, nanowire diameter and pitch, metal film coverage, Si/Au/etchant interface length, and crystalline quality of the colloidal template (grain size and defects). Our results investigate the origin of the catalyst film fracture and reveal that MACE experiments should be optimized for each Si wire array geometry by keeping the etch rate below a certain threshold. We show that the Si/Au/etchant interface length also affects the etch rate and should thus be considered when optimizing the MACE experimental parameters. Finally, our results demonstrate that colloidal templates with small grain sizes (i.e., <100 μm) can yield significant problems during the pattern transfer because of a high density of defects at the grain boundaries that negatively affects the metal film stability. As such, this work provides guidelines for the large-scale synthesis of Si micro- and nanowire arrays MACE, relevant for both new and experienced researchers working with MACE.
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http://dx.doi.org/10.1021/acs.chemmater.0c03593DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7659364PMC
November 2020

Spatioselective Deposition of Passivating and Electrocatalytic Layers on Silicon Nanowire Arrays.

ACS Appl Mater Interfaces 2020 Nov 10;12(47):52581-52587. Epub 2020 Nov 10.

Department of Chemistry and Physics of Materials, University of Salzburg, Jakob-Haringer Strasse 2A, Salzburg A-5020, Austria.

Metal-silicon nanowire array photoelectrodes provide a promising architecture for water-splitting because they can afford high catalyst loading and decouple charge separation from the light absorption process. To further improve and understand these hybrid nanowire photoelectrodes, control of the catalyst amount and location within the wire array is required. Such a level of control is currently synthetically challenging to achieve. Here, we report the synthesis of cm-sized hybrid silicon nanowire arrays with electrocatalytically active Ni-Mo and Pt patches placed at defined vertical locations within the individual nanowires. Our method is based on a modified three-dimensional electrochemical axial lithography (3DEAL), which combines metal-assisted chemical etching (MACE) to produce Si nanowires with spatially defined SiO protection layers to selectively cover and uncover specific areas within the nanowire arrays. This spatioselective SiO passivation yields nanowire arrays with well-defined exposed Si surfaces, with feature sizes down to 100 nm in the axial direction. Subsequent electrodeposition directs the growth of the metal catalysts at the exposed silicon surfaces. As a proof of concept, we report photoelectrocatalytic activity of the deposited catalysts for the hydrogen evolution reaction on p-type Si nanowire photocathodes. This demonstrates the functionality of these hybrid metal/Si nanowire arrays patterned via 3DEAL, which paves the way for investigations of the influence of three-dimensional geometrical parameters on the conversion efficiency of nanostructured photoelectrodes interfaced with metal catalysts.
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http://dx.doi.org/10.1021/acsami.0c14013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7705884PMC
November 2020

Morphology-Graded Silicon Nanowire Arrays via Chemical Etching: Engineering Optical Properties at the Nanoscale and Macroscale.

ACS Appl Mater Interfaces 2020 Mar 4;12(11):13140-13147. Epub 2020 Mar 4.

Department of Chemistry and Physics of Materials, University of Salzburg, Jakob Haringer Strasse 2A, A-5020 Salzburg, Austria.

We report on a quick, simple, and cost-effective solution-phase approach to prepare centimeter-sized morphology-graded vertically aligned Si nanowire arrays. Gradients in the nanowire diameter and shape are encoded through the macroscale substrate via a "dip-etching" approach, where the substrate is removed from a KOH etching solution at a constant rate, while morphological control at the nanowire level is achieved via sequential metal-assisted chemical etching and KOH etching steps. This combined approach provides control over light absorption and reflection within the nanowire arrays at both the macroscale and nanoscale, as shown by UV-vis spectroscopy and numerical three-dimensional finite-difference time-domain simulations. Macroscale morphology gradients yield arrays with gradually changing optical properties. Nanoscale morphology control is demonstrated by synthesizing arrays of bisegmented nanowires, where the nanowires are composed of two distinct segments with independently controlled lengths and diameters. Such nanowires are important to tailor light-matter interactions in functional devices, especially by maximizing light absorption at specific wavelengths and locations within the nanowires.
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http://dx.doi.org/10.1021/acsami.9b21466DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7082793PMC
March 2020

Three-Dimensional Electrochemical Axial Lithography on Si Micro- and Nanowire Arrays.

Nano Lett 2018 11 25;18(11):7343-7349. Epub 2018 Oct 25.

Department of Chemistry and Physics of Materials , University of Salzburg , Jakob Haringer Strasse 2A , A-5020 Salzburg , Austria.

A templated electrochemical technique for patterning macroscopic arrays of single-crystalline Si micro- and nanowires with feature dimensions down to 5 nm is reported. This technique, termed three-dimensional electrochemical axial lithography (3DEAL), allows the design and parallel fabrication of hybrid silicon nanowire arrays decorated with complex metal nano-ring architectures in a flexible and modular approach. While conventional templated approaches are based on the direct replication of a template, our method can be used to perform high-resolution lithography on pre-existing nanostructures. This is made possible by the synthesis of a porous template with tunable dimensions that guides the deposition of well-defined metallic shells around the Si wires. The synthesis of a variety of ring architectures composed of different metals (Au, Ag, Fe, and Ni) with controlled sequence, height, and position along the wire is demonstrated for both straight and kinked wires. We observe a strong enhancement of the Raman signal for arrays of Si nanowires decorated with multiple gold rings due to the plasmonic hot spots created in these tailored architectures. The uniformity of the fabrication method is evidenced by a homogeneous increase in the Raman signal throughout the macroscopic sample. This demonstrates the reliability of the method for engineering plasmonic fields in three dimensions within Si wire arrays.
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http://dx.doi.org/10.1021/acs.nanolett.8b03608DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6238956PMC
November 2018

Investigation of Mass-Produced Substrates for Reproducible Surface-Enhanced Raman Scattering Measurements over Large Areas.

ACS Appl Mater Interfaces 2017 Aug 24;9(30):25445-25454. Epub 2017 Jul 24.

Department of Chemistry and Physics of Materials, University of Salzburg , Jakob-Haringer-Strasse 2a, 5020 Salzburg, Austria.

Surface-enhanced Raman scattering (SERS) is a versatile spectroscopic technique that suffers from reproducibility issues and usually requires complex substrate fabrication processes. In this article, we report the use of a simple mass production technology based on Blu-ray disc manufacturing technology to prepare large area SERS substrates (∼40 mm) with a high degree of homogeneity (±7% variation in Raman signal) and enhancement factor of ∼6 × 10. An industrial high throughput injection molding process was used to generate periodic microstructured polymer substrates coated with a thin Ag film. A short chemical etching step produces a highly dense layer of Ag nanoparticles at the polymer surface, which leads to a large and reproducible Raman signal. Finite difference time domain simulations and cathodoluminescence mapping experiments suggest that the sample microstructure is responsible for the generation of SERS active nanostructures around the microwells. Comparison with commercial SERS substrates demonstrates the validity of our method to prepare cost-efficient, reliable, and sensitive SERS substrates.
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http://dx.doi.org/10.1021/acsami.7b06002DOI Listing
August 2017

Enzyme adsorption-induced activity changes: a quantitative study on TiO model agglomerates.

J Nanobiotechnology 2017 Jul 21;15(1):55. Epub 2017 Jul 21.

Department of Chemistry and Physics of Materials, Paris Lodron University of Salzburg, Jakob-Haringer-Strasse 2a, 5020, Salzburg, Austria.

Background: Activity retention upon enzyme adsorption on inorganic nanostructures depends on different system parameters such as structure and composition of the support, composition of the medium as well as enzyme loading. Qualitative and quantitative characterization work, which aims at an elucidation of the microscopic details governing enzymatic activity, requires well-defined model systems.

Results: Vapor phase-grown and thermally processed anatase TiO nanoparticle powders were transformed into aqueous particle dispersions and characterized by dynamic light scattering and laser Doppler electrophoresis. Addition of β-galactosidase (β-gal) to these dispersions leads to complete enzyme adsorption and the generation of β-gal/TiO heteroaggregates. For low enzyme loadings (~4% of the theoretical monolayer coverage) we observed a dramatic activity loss in enzymatic activity by a factor of 60-100 in comparison to that of the free enzyme in solution. Parallel ATR-IR-spectroscopic characterization of β-gal/TiO heteroaggregates reveals an adsorption-induced decrease of the β-sheet content and the formation of random structures leading to the deterioration of the active site.

Conclusions: The study underlines that robust qualitative and quantitative statements about enzyme adsorption and activity retention require the use of model systems such as anatase TiO nanoparticle agglomerates featuring well-defined structural and compositional properties.
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http://dx.doi.org/10.1186/s12951-017-0283-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5521066PMC
July 2017

Confined Etching within 2D and 3D Colloidal Crystals for Tunable Nanostructured Templates: Local Environment Matters.

ACS Appl Mater Interfaces 2017 Feb 17;9(4):3931-3939. Epub 2017 Jan 17.

Department of Chemistry and Physics of Materials, University of Salzburg , Hellbrunner Straße 34/III, A-5020 Salzburg, Austria.

We report the isotropic etching of 2D and 3D polystyrene (PS) nanosphere hcp arrays using a benchtop O radio frequency plasma cleaner. Unexpectedly, this slow isotropic etching allows tuning of both particle diameter and shape. Due to a suppressed etching rate at the point of contact between the PS particles originating from their arrangement in 2D and 3D crystals, the spherical PS templates are converted into polyhedral structures with well-defined hexagonal cross sections in directions parallel and normal to the crystal c-axis. Additionally, we found that particles located at the edge (surface) of the hcp 2D (3D) crystals showed increased etch rates compared to those of the particles within the crystals. This indicates that 2D and 3D order affect how nanostructures chemically interact with their surroundings. This work also shows that the morphology of nanostructures periodically arranged in 2D and 3D supercrystals can be modified via gas-phase etching and programmed by the superlattice symmetry. To show the potential applications of this approach, we demonstrate the lithographic transfer of the PS template hexagonal cross section into Si substrates to generate Si nanowires with well-defined hexagonal cross sections using a combination of nanosphere lithography and metal-assisted chemical etching.
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http://dx.doi.org/10.1021/acsami.6b14226DOI Listing
February 2017

Hydroxylation Induced Alignment of Metal Oxide Nanocubes.

Angew Chem Int Ed Engl 2017 01 22;56(5):1407-1410. Epub 2016 Dec 22.

Department of Chemistry and Physics of Materials, Paris Lodron University of Salzburg, Hellbrunnerstrasse 34/III, 5020, Salzburg, Austria.

Water vapor is ubiquitous under ambient conditions and may alter the shape of nanoparticles. How to utilize water adsorption for nanomaterial functionality and structure formation, however, is a yet unexplored field. Herein, we report the use of water vapor to induce the self-organization of MgO nanocubes into regularly staggered one-dimensional structures. This transformation evolves via an initial alignment of the MgO cubes, the formation of intermediate elongated Mg(OH) structures, and their reconversion into MgO cubes arranged in staggered structures. Ab initio DFT modelling identifies surface-energy changes associated with the cube surface hydration and hydroxylation to promote the uncommon staggered stacked assembly of the cubes. This first observation of metal oxide nanoparticle self-organization occurring outside a bulk solution may pave novel routes for inducing texture in ceramics and represents a great test-bed for new surface-science concepts.
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http://dx.doi.org/10.1002/anie.201608538DOI Listing
January 2017

Modification of Charge Trapping at Particle/Particle Interfaces by Electrochemical Hydrogen Doping of Nanocrystalline TiO.

J Am Chem Soc 2016 12 29;138(49):15956-15964. Epub 2016 Nov 29.

Department of Physics, University of York , Heslington, York YO10 5DD, United Kingdom.

Particle/particle interfaces play a crucial role in the functionality and performance of nanocrystalline materials such as mesoporous metal oxide electrodes. Defects at these interfaces are known to impede charge separation via slow-down of transport and increase of charge recombination, but can be passivated via electrochemical doping (i.e., incorporation of electron/proton pairs), leading to transient but large enhancement of photoelectrode performance. Although this process is technologically very relevant, it is still poorly understood. Here we report on the electrochemical characterization and the theoretical modeling of electron traps in nanocrystalline rutile TiO films. Significant changes in the electrochemical response of porous films consisting of a random network of TiO particles are observed upon the electrochemical accumulation of electron/proton pairs. The reversible shift of a capacitive peak in the voltammetric profile of the electrode is assigned to an energetic modification of trap states at particle/particle interfaces. This hypothesis is supported by first-principles theoretical calculations on a TiO grain boundary, providing a simple model for particle/particle interfaces. In particular, it is shown how protons readily segregate to the grain boundary (being up to 0.6 eV more stable than in the TiO bulk), modifying its structure and electron-trapping properties. The presence of hydrogen at the grain boundary increases the average depth of traps while at the same time reducing their number compared to the undoped situation. This provides an explanation for the transient enhancement of the photoelectrocatalytic activity toward methanol photooxidation which is observed following electrochemical hydrogen doping of rutile TiO nanoparticle electrodes.
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http://dx.doi.org/10.1021/jacs.6b08636DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5193466PMC
December 2016

Hydration of magnesia cubes: a helium ion microscopy study.

Beilstein J Nanotechnol 2016 29;7:302-9. Epub 2016 Feb 29.

Department of Chemistry and Physics of Materials, University of Salzburg, Hellbrunnerstrasse 34/ III, A-5020 Salzburg, Austria.

Physisorbed water originating from exposure to the ambient can have a strong impact on the structure and chemistry of oxide nanomaterials. The effect can be particularly pronounced when these oxides are in physical contact with a solid substrate such as the ones used for immobilization to perform electron or ion microscopy imaging. We used helium ion microscopy (HIM) and investigated morphological changes of vapor-phase-grown MgO cubes after vacuum annealing and pressing into foils of soft and high purity indium. The indium foils were either used as obtained or, for reference, subjected to vacuum drying. After four days of storage in the vacuum chamber of the microscope and at a base pressure of p < 10(-7) mbar, we observed on these cubic particles the attack of residual physisorbed water molecules from the indium substrate. As a result, thin magnesium hydroxide layers spontaneously grew, giving rise to characteristic volume expansion effects, which depended on the size of the particles. Rounding of the originally sharp cube edges leads to a significant loss of the morphological definition specific to the MgO cubes. Comparison of different regions within one sample before and after exposure to liquid water reveals different transformation processes, such as the formation of Mg(OH)2 shells that act as diffusion barriers for MgO dissolution or the evolution of brucite nanosheets organized in characteristic flower-like microstructures. The findings underline the significant metastability of nanomaterials under both ambient and high-vacuum conditions and show the dramatic effect of ubiquitous water films during storage and characterization of oxide nanomaterials.
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http://dx.doi.org/10.3762/bjnano.7.28DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4901542PMC
June 2016

Solution-Dispersible Metal Nanorings with Deliberately Controllable Compositions and Architectural Parameters for Tunable Plasmonic Response.

Nano Lett 2015 Aug 2;15(8):5273-8. Epub 2015 Jul 2.

†Department of Materials Science and Engineering, ‡Department of Chemical and Biological Engineering, and §Department of Chemistry, and International Institute for Nanotechnology, Northwestern University, Evanston, Illinois 60208, United States.

We report a template-based technique for the preparation of solution-dispersible nanorings composed of Au, Ag, Pt, Ni, and Pd with control over outer diameter (60-400 nm), inner diameter (25-230 nm), and height (40 nm to a few microns). Systematic and independent control of these parameters enables fine-tuning of the three characteristic localized surface plasmon resonance modes of Au nanorings and the resulting solution-based extinction spectra from the visible to the near-infrared. This synthetic approach provides a new pathway for solution-based investigations of surfaces with negative curvature.
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http://dx.doi.org/10.1021/acs.nanolett.5b01594DOI Listing
August 2015

Coaxial lithography.

Nat Nanotechnol 2015 Apr 23;10(4):319-24. Epub 2015 Mar 23.

1] Department of Materials Science and Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA [2] International Institute for Nanotechnology, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA [3] Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA.

The optical and electrical properties of heterogeneous nanowires are profoundly related to their composition and nanoscale architecture. However, the intrinsic constraints of conventional synthetic and lithographic techniques have limited the types of multi-compositional nanowire that can be created and studied in the laboratory. Here, we report a high-throughput technique that can be used to prepare coaxial nanowires with sub-10 nm control over the architectural parameters in both axial and radial dimensions. The method, termed coaxial lithography (COAL), relies on templated electrochemical synthesis and can create coaxial nanowires composed of combinations of metals, metal oxides, metal chalcogenides and conjugated polymers. To illustrate the possibilities of the technique, a core/shell semiconductor nanowire with an embedded plasmonic nanoring was synthesized--a structure that cannot be prepared by any previously known method--and its plasmon-excitation-dependent optoelectronic properties were characterized.
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http://dx.doi.org/10.1038/nnano.2015.33DOI Listing
April 2015

Hybrid semiconductor core-shell nanowires with tunable plasmonic nanoantennas.

Adv Mater 2013 Aug 1;25(32):4515-20. Epub 2013 Jul 1.

Department of Materials Science and Engineering, Northwestern University, 2220 Campus Drive, Evanston, IL 60208, USA.

Multi-segmented nanowires with optically active hybrid core-shell regions are fabricated between two metal nanoantennas. These nanowires generate significant photocurrent under illumination and are solution-dispersible.
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http://dx.doi.org/10.1002/adma.201301367DOI Listing
August 2013

Long-range plasmophore rulers.

Nano Lett 2013 May 17;13(5):2270-5. Epub 2013 Apr 17.

Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA.

Using on-wire lithography, we studied the emission properties of nanostructures made of a polythiophene disk separated by fixed nanoscopic distances from a plasmonic gold nanorod. The intense plasmonic field generated by the nanorod modifies the shape of the polythiophene emission spectrum, and the strong distance dependence of this modulation forms the basis for a new type of "plasmophore ruler". Simulations using the discrete dipole approximation (DDA) quantitatively support our experimental results. Importantly, this plasmophore ruler is independent of signal intensity and is effective up to 100 nm, which is more than two times larger than any reported value for rulers based on photoluminescence processes.
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http://dx.doi.org/10.1021/nl400884jDOI Listing
May 2013

Dispersible surface-enhanced Raman scattering nanosheets.

Adv Mater 2012 Nov 5;24(45):6065-70. Epub 2012 Sep 5.

Department of Chemistry and Engineering, Northwestern University, Evanston, IL 60208, USA.

Ultrathin and flexible silica nanosheets, synthesized with gold nanorod dimers embedded uniformly throughout, can be dispersed in solution and deposited onto arbitrary surfaces. These novel materials conform and maintain the as-synthesized density of dimers, allowing them to be used reliably in labeling and detection applications.
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http://dx.doi.org/10.1002/adma.201202845DOI Listing
November 2012

Facile phase transfer of large, water-soluble metal nanoparticles to nonpolar solvents.

Langmuir 2012 Feb 27;28(5):2909-13. Epub 2012 Jan 27.

Department of Chemistry and Centre for Self-Assembled Chemical Structures, McGill University, 801 Sherbrooke Street West, Montreal, Quebec, Canada H3A 2K6.

The facile phase-transfer of large, water-soluble metal nanoparticles to nonpolar solvent is reported here. Thiol-terminated polystyrene (PS-SH) is ligand-exchanged onto water-soluble metal nanoparticles in single-phase acetone/water mixtures, generating a precipitate. The solvent is then removed and the particles are redissolved in nonpolar solvent. This approach is demonstrated for nanoparticles of different metal (Au and Ag), size (3 to >100 nm), shape (spheres, rods, and wires, etc.), and leaving ligand (citrate, cetyltrimethylammonium bromide, poly(vinylpyrrolidone), and 4-dimethylaminopyridine. The resulting PS-SH-stabilized nanoparticles maintain their initial size and shape, and are highly stable. They are soluble in various organic solvents (toluene, benzene, chloroform, dichloromethane, and tetrahydrofuran), and can be readily dried, purified, and re-dissolved. This method makes possible the utilization of a full range of existing nanoparticle cores in nonpolar solvents with a single ligand. It provides access to numerous nanomaterials that cannot be obtained through direct synthesis in nonpolar solvent, and is expected to be of significant value in a number of applications.
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http://dx.doi.org/10.1021/la2038894DOI Listing
February 2012

Electrochemical synthesis of Ag(0)/A2S heterojunctions templated on pre-formed Ag2S nanowires.

Nanoscale 2011 Apr 16;3(4):1838-44. Epub 2011 Mar 16.

Department of Chemistry, McGill University and Center for Self-Assembled Chemical Structures, 801 Sherbrooke Street West, H3A 2K6, Montreal, Canada.

Hybrid metal/ionic conductor nanostructures are of considerable interest due to their potential use as resistive switches, and are envisioned as the next generation of memory devices. We present here the electrochemical conversion of ionic and semi-conducting Ag(2)S nanowires (NW) into a range of hybrid nanostructures. Partial electrochemical reduction of Au/Ag(2)S NW/Au junctions allows one to form Ag(0) NW/Ag(2)S NW and Ag(0) NW/Ag(2)S NW/Ag(0) NW heterojunctions. Control over the quantity of Ag(0) NW within the junctions is presented along with its influence on the conductivity of the junctions. We demonstrate the use of this technique to make functional Au/Ag(0) NW/Ag(2)S NW/Au resistive switches.
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http://dx.doi.org/10.1039/c0nr00886aDOI Listing
April 2011

Potential controlled electrochemical conversion of AgCN and Cu(OH)2 nanofibers into metal nanoparticles, nanoprisms, nanofibers, and porous networks.

ACS Appl Mater Interfaces 2010 Dec 1;2(12):3745-58. Epub 2010 Dec 1.

Department of Chemistry and Center for Self-Assembled Chemical Structures (CSACS), McGill University, 801 Sherbrooke Street W, Montreal, Quebec H3A 2K6, Canada.

Nanowires are expected to provide considerable advances in the use of smaller and more efficient sensing, electronic, and photovoltaic devices. Good electrical connections of the nanowires within devices can, however, be problematic. We present here a new method that takes advantage of the available large-scale and reproducible wet-chemical syntheses of non-zero-valent anisotropic nanomaterials. The electrochemical reduction of preformed solid AgCN and Cu(OH)2 nanofibers (NFs) on surfaces allows one to form metallic nanostructures that are integrated in electrical junctions with excellent electrical contacts. Some fundamental aspects of the electrochemical reduction of AgCN NF are presented, including their redox potential and propagation of the metal boundary formed during the electrochemical reduction process. The clear connection between native (unreduced) AgCN NF and reduced Ag0 nanostructures is shown. The reduction potential, the nature of the supporting substrate (conductive vs insulating), and the size of the original fibers strongly influence the morphology and dimensions of the Ag0 nanostructures thus produced. A number of different Ag0 nanostructures are electrosynthesized, including nanoprisms, nanoparticles (NPs), and NFs, made from the aggregation of nanoprisms and NPs, and continuous fibers, whose width is tunable between 90 and 500 nm. We report the formation of excellent electrical contact via the electrochemical reduction of metal/Mz+ NF/metal junctions. This technique is simple, fast, and applicable to other materials such as Cu(OH)2 NF. It allows for the formation of electrically connected metallic networks with new interesting geometries, which could be applied to a form of electrochemical welding.
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http://dx.doi.org/10.1021/am100924cDOI Listing
December 2010

1D Cu(OH)(2) nanomaterial synthesis templated in water microdroplets.

J Am Chem Soc 2010 May;132(19):6657-9

Department of Chemistry, McGill University and Center for Self-Assembled Chemical Structure (CSACS), 801 Sherbrooke Street West, Montreal, Quebec, H3A 2K6, Canada.

For many applications, micro- and nanostructured materials show a strong correlation between their geometry and their function. We report here the interfacial precipitation of a copper/alkylamine complex to form Cu(OH)(2) nanofibers in a two-phase system (H(2)O/CH(2)Cl(2)). Their aggregation results in porous microbeads. This mesoscale aggregation is due to the formation of a water-in-oil (W/O) emulsion. The fibers formed at the H(2)O/CH(2)Cl(2) interface adsorb on the water droplet surface leading to spherical networks of Cu(OH)(2) fibers. Our preparation technique is rapid (less than 1 h) and benefits from the simplicity and the tunability of emulsions.To our knowledge, this is the first demonstration of the in situ synthesis of 1D nanostructures that self-assemble at both the surface and the inside of emulsion droplets. We report the successful control over the chemical nature of the synthesized material, its size, and morphology at both the mesoscale (completely hollow versus porous) and the nanoscale (nanoribbons versus nanofibers) by the addition of a short chain alcohol. The transformation of these materials into porous CuO spheres has several potential applications, including a demonstrated sensitive response to visible light (measured photocurrent/dark current ratio of 2.22).
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http://dx.doi.org/10.1021/ja101579vDOI Listing
May 2010