Gilles R. Bourret

• PhD in Chemistry, McGill University
• Professor (Associate) at University of Salzburg

The increasing vulnerability of microchips to counterfeiting poses a significant threat to nations, companies, and the general public. Creating a unique “fingerprint” on each chip using intrinsic manufacturing variations can significantly prevent the number of fraudulent chips. Since Si‐based semiconductor fabrication processes are now flawless dow...

We report the synthesis of vertically aligned silicon nanowire (VA-SiNW) oligomer arrays coated with Au nanoparticle (NP) monolayers via a combination of colloidal lithography, metal-assisted chemical etching, and directed NP assembly. Arrays of SiNW monomers (i.e., isolated NWs), dimers, and tetramers are synthesized, decorated with AuNPs, and tes...

We report the use of thermal dewetting to structure gold-based catalytic etching masks for metal-assisted chemical etching (MACE). The approach involves low-temperature dewetting of metal films to generate metal holey meshes with tunable morphologies. Combined with MACE, dewetting-assisted patterning is a simple, benchtop route to synthesize Si nan...

The fate of photogenerated charges within ferroelectric metal oxides is key for photocatalytic applications. The authors study the contributions of i) tetragonal distortion, responsible for spontaneous polarization, and ii) point defects, on charge separation and recombination within BaTiO3 (BTO) nanocrystals of cubic and tetragonal structure. Elec...

EELS, SERS and electromagnetic simulations demonstrate large E-field enhancements at Rh segments located in the gap region of AuRh_Au nanorod heterodimers.

Gold nanoparticle/silicon composites are canonical substrates for sensing applications because of their geometry-dependent physicochemical properties and high sensing activity via surface-enhanced Raman spectroscopy (SERS). The self-assembly of gold nanoparticles (AuNPs) synthesized via wet-chemistry on functionalized flat silicon (Si) and vertical...

Thanks to their tunable and strong interaction with light, plasmonic nanostructures have been investigated for a wide range of applications. In most cases, controlling the electric field enhancement at the metal surface is crucial. This can be achieved by controlling the metal nanostructure size, shape, and location in three dimensions, which is sy...

A variety of multisegmented nanorods (NRs) composed of dense Au and porous Rh and Ru segments with lengths controlled down to ca. 10 nm are synthesized within porous anodic aluminum oxide membranes. Despite the high Rh and Ru porosity (i.e., ∼40%), the porous metal segments are able to efficiently couple with the longitudinal localized surface plas...

Vertically aligned silicon nanowire (VA-SiNW) arrays can significantly enhance light absorption and reduce light reflection for efficient light trapping. VA-SiNW arrays thus have the potential to improve solar cell design by providing reduced front-face reflection while allowing the fabrication of thin, flexible, and efficient silicon-based solar c...

Developing simple, inexpensive, and environmentally benign approaches to integrate morphologically well-defined nanoscale building blocks into larger high surface area materials is a key challenge in materials design and processing. In this work, we investigate the fundamental surface phenomena between MgO and water (both adsorption and desorption)...

The combination of metal-assisted chemical etching (MACE) and colloidal lithography allows for the affordable, large-scale and high-throughput synthesis of silicon nanowire (SiNW) arrays. However, many geometric parameters of these arrays are coupled and cannot be addressed individually using colloidal lithography. Despite recent advancements towar...

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 i...

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 prov...

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...

Ambient water condenses readily on metal oxides, which can lead to water film formation and water-mediated reactions at the oxide surface. Similar to bulk water, thin water films with thicknesses below 10 molecular layers can modify the oxide surface chemical reactivity and stability. However, due to the confinement of mass transport at the oxide s...

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 comple...

Colloidal lithography is a cost-efficient method to produce large-scale nanostructured arrays on surfaces. Typically, colloidal particles are assembled into hexagonal close-packed monolayers at liquid interfaces and deposited onto a solid substrate. Many applications, however, require non close-packed monolayers, which are more difficult to fabrica...

Measuring the dimensions and number density of nanoparticles dispersed in a solid matrix is usually accomplished via transmission electron microscopy (TEM) which suffers from high cost, low throughput, and small analytical volume. In comparison, scanning backscattered electron microscopy is inexpensive, requires little sample preparation, and allow...

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 mm²...

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...

In the automotive industry Al-Mg-Si alloys are often chosen for high strength extruded profiles. However, the production of such profiles can be challenging for high alloy contents. Among several processing steps, the homogenization heat treatment before extrusion is readily accessible to modifications to improve high temperature formability. In th...

We report the isotropic etching of 2D and 3D polystyrene (PS) nanosphere hcp arrays using a benchtop O2 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 2...

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 st...

Wasserdampf kann die Form und Anordnung von Nanopartikeln entscheidend beeinflussen. Inwieweit dies für die Steuerung der Struktur und Eigenschaften von Nanomaterialien nutzbar ist, wurde bislang allerdings kaum erforscht. Hier wird über die durch Wasserdampf ausgelöste Selbstorganisation von MgO-Nanowürfeln in regelmäßig versetzte eindimensionale...

As part of an ongoing effort to develop novel, highly active and stable Pt-free catalysts for the oxygen reduction reaction (ORR), we here report the synthesis, structural characteristics and electrochemical/electrocatalytic properties of novel core-shell composite materials, consisting of a spherical nitrided carbon core and a tantalum (oxy)nitrid...

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. incorp...

Characterization of Mg-Si precipitates is crucial for optimizing the homogenization heat treatment of Al-Mg-Si alloys. Although sample preparation is key for high quality scanning electron microscopy imaging, most common methods lead to dealloying of Mg-Si precipitates. In this article we systematically evaluate different sample preparation methods...

Aluminium extrudate used for safety parts in cars need to exhibit high yield strength and ductility, a combination that is not easily achieved. In this work, the mechanical properties and microstructure of profiles with a yield strength greater than 280MPa achieved by two different artificial ageing treatments were studied. Profiles from one of the...

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 i...

The most frequently studied functionalities of porous WO3 particle systems - namely their electrochromic and photocatalytic properties - are intimately related with the wanted or unwanted action of defects in the material. Here we report on the generation and action of three types of defects in WO3 electrodes: solid/solid interfaces between adjacen...

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...

The optical and electrical properties of heterogeneous nanowires are profoundly related to their composition and nanoscale architecture1, 2, 3, 4, 5, 6, 7. 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....

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.

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 form...

T. Ozel and G. R. Bourret equally contributed to his work

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.

We describe x-ray photon correlation spectroscopy (XPCS) experiments tracking the motion of gold nanoparticles within solutions of high-molecular-weight polystyrene. Over displacements from nanometers to tens of nanometers, the particles undergo subdiffusive motion that is dictated by the temporal evolution of the entangled polymer mesh in the imme...

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 solven...

The facile fabrication of free-standing conductive Au(0) and Ag(0) nanostructured monoliths via the chemical reduction of sheets composed respectively of AuCl(n-butylamine) nanofibers and aggregated AgCl nanocubes is reported. This preparation can be performed on a large scale (hundreds of milligrams) with high yield (>74%). The product sheets have...

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 reduc...

This Thesis presents the synthesis of novel 1D, 2D, and 3D Ag(I) and Cu(II) nanostructures and their use as sacrificial templates to make functional nanomaterials. New soft template methods were developed for the synthesis of AgCN and Cu(OH)2 nanostructures. Polymeric organic nanotubes were successfully used to synthesize AgCN nanowires, while the...

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 synthes...

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...

A template-based method for the fabrication of silver cyanide and polymer composite nanowires is described. Poly(styrene-alt-maleic anhydride) forms nanotubes in aqueous solution and acts as a template, guiding the growth of silver cyanide into long nanowires. The structures obtained can grow to several tens of micrometers in length and their diame...

X-ray photon correlation spectroscopy is employed to investigate the motion of dilute suspensions of gold nanoparticles in low-molecular-weight polystyrene melts. At high temperatures, the observed motion is diffusive, with a rate that follows a Vogel-Fulcher temperature dependence. Closer to the glass transition temperature Tg, diffusion is supers...

We report x-ray photon correlation spectroscopy (XPCS) experiments to investigate the motion of nanoscale gold particles within polystyrene (PS) melts of molecular weight between 2K and 48K g/mol. The particles, with radius of approximately 2 nm, are dispersed in a highly dilute concentration (volume fraction 0.0004) and are functionalized with PS...

This Thesis presents the synthesis of novel 1D, 2D, and 3D Ag(I) and Cu(II) nanostructures and their use as sacrificial templates to make functional nanomaterials. New soft template methods were developed for the synthesis of AgCN and Cu(OH)2 nanostructures. Polymeric organic nanotubes were successfully used to synthesize AgCN nanowires, while the...