Metallic Nanostructures Research Articles

Employing Electrochemical Potential Cycling to Controlling Surface to Volume Ratio of Nanoporous Gold and Photoelectron Injection into Electrolyte

Nanoporous metals made by alloy corrosion are bicountinuous porous networks that possess nanoscale ligaments and pores and thus a large surface-to-volume ratio. Their ligament and pore size can be tuned between a few nanometers and several microns via thermal annealing [1], which makes them attractive material systems for a variety of applications, including catalysis, sensing, and energy storage. In particular, dealloying-derived nanoporous metals, present novel opportunities for exploring the impact of surfaces on electro-photocatalytic activity of metallic nanostructures [2]. Yet, achieving the ligament and pore sizes in the dealloyed metallic networks below 10 nm, which is especially crucial for understanding an efficient electrochemical charge transfer, is challenging so far.In this study, we demonstrate a successful fabrication of nanoporous gold (npAu) thin films via electrochemical dealloying with the ligament size down below 10 nm on quartz substrate. We study the material by means of in situ photoelectrochemical setup while simultaneously varying the electrode potential in 0.5 M H2SO4 electrolyte. To probe the size effect on the photocurrent response, we exploit cyclic voltammetry (CV) in order to promote coarsening of the ligaments of npAu networks. By varying a number of CV cycles, we were able to induce subtle changes in the ligament size, therefore modifying the surface-to-volume ratio of the nanoporous metals at the lower limit of the nanoscale.Our results show that this approach provides an excellent foundation for future optical investigations of surface effects on the internal quantum efficiency of high-surface area metallic photoelectrodes.Our study demonstrates that modifying the surface-to-volume ratio of the sample by electrochemistry allows us to control the hot electron generation and injection processes in nanoscale plasmonic systems. Moreover, the internal quantum efficiency of the npAu network photoelectrode is significantly influenced by the size of its ligaments. In contrast to prior findings that suggested efficiency would level off with decreasing ligament size [3], we have observed a continuous nonlinear increase in quantum efficiency as the ligament size decreased from 16 to 8 nm. This result is attributed to the increase in absorption by the electrons colliding with the surface (Landau damping) and increase of emission of this electrons into the electrolyte due to possibility of multiple collisions with the surface.

Charged-Particle-Irradiated Tin Oxyhydroxide Nanoparticle Anodes for Lithium-Ion Batteries

Metal oxyhydroxides have been promising ceramic materials in miscellaneous electrochemical fields due to their multiple redox states, interlayer conductivity, and structural stability as well as electrocatalytic activity. When applied to anode active materials for secondary batteries, particularly lithium-ion batteries, metal oxyhydroxides have a much larger theoretical capacity than that of commercial graphite by conversion and/or alloying reactions with lithium ions rather than intercalation. However, the inevitable volume variation of metal oxyhydroxides during battery operation impinges other primary components in anode materials such as binders and conducting agents, leading to pulverizing the anode materials. Moreover, metal oxyhydroxides are not electrically conductive so much that electrochemical reactions cannot be facilitated efficiently during cycling. Accordingly, many efforts, for example, nanostructuring, constructing hierarchical configurations or hollow structures, and hybridization with carbonaceous materials, have been attempted to overcome the limitations of metal oxyhydroxide anode active materials. In addition, crystal defects in anode materials are greatly helpful to promote electrochemical activity by tuning electronic and chemical properties. Hydrogen annealing, plasma treatment, and chemical reduction method are common approaches to inducing a large number of defects in materials, but they are generally employed at high temperatures or under controlled-pressure circumstances. Therefore, we deploy charged particle irradiation to generate numerous defects in the metal oxyhydroxide anode materials. Incident charged particles interact with a lot of atoms in the anode materials, causing atomic displacement. As a result of the displacement, diverse kinds of defects are produced, which change the electronic and chemical structures of the anode materials. Charged particle irradiation introduces a high density of defects and selective defect types for short time at room temperature. Amorphization is also induced by charged particle irradiation, which is beneficial to improve the electrochemical performance of metal oxyhydroxide anode materials. Herein, we first synthesize tin oxyhydroxide nanoparticles (SnOOH NPs), one of the potential anode active materials using simple nanostructuring, via an electrochemical route, anodization. Anodization is a very fast and concise process to obtain nanostructured metal oxides as well as NPs. Electrodes with SnOOH NPs are irradiated with various charged particles including electrons, protons, helium ions, nitrogen ions, and argon ions, and the irradiation effects are investigated. SnOOH NP anodes irradiated with each type of charged particle show different electrochemical performances from each other, but all of the irradiated SnOOH NP anodes exhibit enhanced discharge capacity or cycle life compared with a pristine SnOOH NP anode. Plausible mechanisms of the irradiation effects depending on charged particles are also proposed. Charged particle irradiation can be utilized for not only metal oxyhydroxides but any kind of ceramic materials in diverse applications including lithium-ion batteries. Figure 1

(Invited) Metal Oxide Mixed Sulphide of Controlled Crystal Structure As Catalysts for Two-Electron Water Oxidation

Conventional catalysts based on noble metals (Pt, Ru) are often used for production of oxygen during water electrolysis in four-electron pathway as they can decrease gas evolution overpotential. Another possible valuable product from water oxidation is hydrogen peroxide obtained via two-electron process. Currently, transition metal oxides, are readily employed to catalyse this reaction. Although they display certain activity, it is still not satisfactory for mass production of H2O2, therefore further optimisations are needed. We suggest in this work, in addition to typical nanostructure modifications of metal oxides (MoO2) such as doping or structural engineering, an application of transition metal dichalcogenides (MoS2). Consequently, the oxide is partially replaced by sulphur. The selection of molybdenum as a centre atom ensures sufficient electrical conductivity of material as an electrode active layer. This combination is intended to provide the benefits thanks to layered materials of tuned interlayer spacing as well as controlled number of active sites. It enables selective adsorption of intermediate products of water oxidation (O∗, OH∗, and OOH∗), and therefore increased preference towards two-electron pathway.Various chemical approaches are considered to synthesize this material, especially hydrothermal treatment in autoclave and high-temperature sintering of precursors. The catalytic activity of the nanostructured metal oxide is further enhanced by its deposition on conductive high surface area support made of carbon/graphite particles of strictly defined textural parameters and surface chemistry. The final composite is obtained using hydrophobic binders (PVDF and PTFE) to form the electrode and improve the catalyst stability. The measurements are carried out in flow electrolyser unit with an alkaline electrolyte. The amount of produced H2O2, H2 as well as quantity and quality of evolved gases are assessed in terms of faradaic efficiency, pressure and overvoltage measurements.

Circular dichroism of pseudo-two-dimensional metal nanostructures: Rotational symmetry and reciprocity.

Circular dichroism (CD) spectra for pseudo-two-dimensional chiral nanomaterials were systematically investigated and analyzed in relation to the rotational symmetry of the nanomaterials. Theoretically, an ideal two-dimensional chiral matter is CD inactive for light incident normal to the plane if it possesses threefold or higher rotational symmetry. If the matter has two- or onefold rotational symmetry, it should exhibit CD activity, and the CD signal measured from the back side of the matter is expected to be inverted from that measured from the front side. For pseudo-two-dimensional chiral gold nanostructures fabricated on glass substrates using electron beam lithography, matter with fourfold rotational symmetry is found to be CD active, even when special care is taken to ensure that the optical environments for the front and back sides of the sample are equivalent. In this case, the CD signal measured from the back side is found to be almost exactly the same as that measured from the front side. It is revealed that the observed chiro-optical behavior arises from three-dimensional chiral characteristics due to differences in the surface shape between the front and back sides of the structures. For matter that is two- or onefold rotationally symmetric, the CD signal measured from the back side is not coincident with that from the front side. For certain wavelength regions, the CD signals measured from the front side and back side are observed to be similar, while at other wavelengths, the inverted component of the CD signals is found to dominate. The observed CD spectral behavior for reciprocal optical measurement configurations is considered to be determined by a balance between the in-plane isotropic and anisotropic components of the chiral permittivity.

Enhancement of Metal Nanostructure Deposition on Silicon Laser-Induced Periodic Surface Structures by Galvanic Replacement.

We report a chemically motivated, single-step method to enhance metal deposition onto silicon laser-induced periodic surface structures (LIPSSs) using reactive laser ablation in liquid (RLAL). Galvanic replacement (GR) reactions were used in conjunction with RLAL (GR-RLAL) to promote the deposition of Au and Cu nanostructures onto a Si LIPSS. To increase the deposition of Au, sacrificial metals Cu, Fe, and Zn were used; Fe and Zn also enhanced the deposition of Cu. We show that the deposited metal content, surface morphology, and metal crystallite size can be tuned based on the difference in electrochemical potentials of the deposited and sacrificial metal. Compared to the Au and Cu reference samples, GR more than doubled the metal content on the LIPSS and reduced metal crystallite sizes by up to 20%. The ability to tune the metal content and crystalline domain size simultaneously makes GR-RLAL a potentially useful approach in the manufacturing of functional metal-LIPSS materials such as surface-enhanced Raman spectroscopy substrates.

Tuning the Electrochemical Performance of Multiple Phased Selenides@C/MXene Composites via Controllable Synthesis of Multivariate Metal‐Organic Frameworks

AbstractMetal‐organic frameworks (MOFs) are excellent precursors for electrode materials preparations. Synergistic effects may exist between different metal centers in multivariate MOFs, making them often more effective than single‐metal MOFs. Herein, we propose an atom economic mechanochemical method to realize the efficient component regulation of target multivariate MOFs. Moreover, by combining the synthesis of multivariate MOFs and exfoliating MXene, multivariate MOF/MXene composites can be obtained via a one‐step strategy. A further selenization process can derive them into selenides@C/MXene composites. These derived composites contain multiple nanostructured metal selenides embedded in multi‐heteroatom doped carbon matrix. For these composites, abundant heterojunction structures are formed, which can build internal self‐built electric field and enhance the reaction kinetics effectively for sodium‐ion storage. More importantly, the electrochemical performance of NCMS@C/MX composites can be optimized due to the intrinsic characteristics of the containing metal selenides. Overall, experimental results demonstrate the universality of this solvent‐free synthesis route for controllable preparation of high‐performance selenides@C/MXene electrode materials. It provides a feasible and environmentally friendly method to adjust metal ratios for optimal energy storage performance. We hope this research inspires optimization strategies for high‐performance electrode materials and leads to the development of energy storage materials with more rational structures and better performance.

Normal Incidence Excitation of Out-of-Plane Lattice Resonances in Bipartite Arrays of Metallic Nanostructures.

As a result of their coherent interaction, two-dimensional periodic arrays of metallic nanostructures support collective modes commonly known as lattice resonances. Among them, out-of-plane lattice resonances, for which the nanostructures are polarized in the direction perpendicular to the array, are particularly interesting since their unique configuration minimizes radiative losses. Consequently, these modes present extremely high quality factors and field enhancements that make them ideal for a wide range of applications. However, for the same reasons, their excitation is very challenging and has only been achieved at oblique incidence, which adds a layer of complexity to experiments and poses some limitations on their usage. Here, we present an approach to excite out-of-plane lattice resonances in bipartite arrays under normal incidence. Our method is based on exploiting the electric-magnetic coupling between the nanostructures, which has been traditionally neglected in the characterization of arrays made of metallic nanostructures. Using a rigorous coupled dipole model, we demonstrate that this coupling provides a general mechanism to excite out-of-plane lattice resonances under normal incidence conditions. We complete our study with a comprehensive analysis of a potential implementation of our results using an array of nanodisks with the inclusion of a substrate and a coating. This work provides an efficient approach for the excitation of out-of-plane lattice resonances at normal incidence, thus paving the way for the leverage of the extraordinary properties of these optical modes in a wide range of applications.

Engineering the Inhomogeneity of Metal-Insulator-Semiconductor Junctions for Photoelectrochemical Methanol Oxidation.

Si-based inhomogeneous metal-insulator-semiconductor (MIS) junctions with a discontinuous metal nanostructure on the Si/insulator layer are expected to be efficient photoelectrodes for solar energy conversion. However, the formation of a metal nanostructure with an optimized arrangement on semiconductors for efficient charge carrier collection is still a big challenge. Herein, we report a method for the in situ formation of an n-Si inhomogeneous MIS junction with well-dispersed metal nanocontacts through a self-assembly process during photoelectrochemical (PEC) methanol oxidation. The photovoltage shows a strong dependence on the inhomogeneity of the n-Si MIS junction, which can be precisely tuned by the applied electrode potential and operation time. The appropriate inhomogeneity of the Schottky junction as well as the high barrier regions induced by the metal oxide/(oxy)hydroxide layer synergistically produces a large photovoltage of 500 mV for the n-Si inhomogeneous MIS junction. Finally, the n-Si-based photoanode is coupled with a CO2-to-formate reaction to realize the production of formate at both electrodes, resulting in a high faradic efficiency (FE) of 86 and 93% for anode and cathode reactions at an operational current of 30 mA/cm2, respectively. These findings provide important insights into the design of highly efficient inhomogeneous MIS junctions through an in situ self-assembly route for solar energy conversion and storage.

Multi-biomarker combination detection system for diagnosis and classification of dry eye disease by imaging of a multi-channel metasurface

Dry eye disease (DED) is one of the most common ocular surface diseases, characterized by unstable tear film and ocular inflammation, affecting hundreds of millions of people worldwide. Currently, the clinical diagnosis of DED mainly relies on physical methods such as optical microscopy and ocular surface interferometric imaging, but classifying DED is still difficult. Here, we propose a compact and portable immune detection system based on the direct imaging of a nanophotonic metasurface with gradient geometry, for fast and ultra-sensitive detection of multiple biomarkers (i.e. Matrix metalloproteinase-9 (MMP-9), Lipocalin-1 (LCN-1), Lactoferrin (LTF)) in tears for the diagnosis and classification of DED. This centimeter-scale concentric nanophotonic metasurface, which consists of millions of unique metallic nanostructures, was fabricated through a cost-effective nanoimprint lithography (NIL) process. The immune detection system based on the antibody-modified metasurface shows favorable detection selectivity, an ultra-high sensitivity (3350 pixels/Refractive Index Unit (RIU)) and low limit of detection (LOD) (0.3 ng/mL for MMP-9, 1 ng/mL for LTF, and 0.5 ng/mL for LCN-1). Further clinical sampling and detection results demonstrated that this multi-biomarker detection system enabled accurate determination and symptom classification of DED, manifesting high correlation and consistency with clinical diagnosis results. The advantages such as low sample consumption, one-step detection, simple operation, and simultaneous detection of multiple biomarkers make the platform promising for screening and detecting a broader range of biomarker combinations in clinical practice.

FeNi alloys encapsulated with N-doped porous carbon nanotubes as highly efficient and durable CO2 reduction electrocatalyst

The development of highly efficient, cost-effective, and robustly stable electrocatalysts for CO2 reduction remains a significant challenge. In this study, a promising CO2 reduction electrocatalyst composed of nanostructured transition metal alloys (i.e., FeNi, FeCo, or CoNi) nanoparticles encapsulated on N-doped porous carbon material is reported. Among the different compositions, FeNi@N-CNTs-1100 exhibited the most efficient CO2ER activity and exceptional stability. It demonstrated a high CO Faradaic efficiency of over 90 % in a wide potential range (–0.47 to –0.97 V (vs. RHE)), with a CO partial current density of 20.18 mA cm−2 at –0.97 V (vs. RHE). Notably, it achieved a long-term stability of 35 h at –0.77 V (vs. RHE) in an H-cell with 0.5 M KHCO3 electrolyte. Various characterization techniques and designed experiments revealed that FeNi@N-CNTs-1100 exhibited enhanced intrinsic catalytic activity and CO selectivity due to optimized *COOH adsorption and *CO desorption compared to the other catalysts studied.

Controlled Stepwise Wet Etching of Polycrystalline Mo Nanowires

AbstractWith the persistent downscaling of integrated circuits, molybdenum (Mo) is currently considered a potential replacement for copper (Cu) as a material for metal interconnects. However, fabricating metal nanostructures with critical dimensions of the order of 10 nm and below is challenging. This is because the very high density of grain boundaries (GBs) results in highly non‐uniform surface profiles during direct wet etching. Moreover, wet etching of Mo with conventional aqueous solutions is problematic, as products of Mo oxidation have different solubility in water, which leads to increased surface roughness. Here, a process is shown for achieving a stable and uniform soluble surface layer of Mo oxide by wet oxidation with H2O2 dissolved in IPA at −20 °C. The oxide layer is then selectively dissolved, and by repeating the oxidation and dissolution multiple times, a uniform etch profile is demonstrated with a fine control over the metal recess. Ultimately, this presents a method of precise and uniform wet etching for Mo and other metals needed to fabricate complex nanostructures that are critical in developing next‐generation electronic devices.

DNA Origami-Based Letterpress Printing of Gold Nanostructures with Predesigned Morphologies.

Creating customizable metallic nanostructures in a simple and controllable manner has been a long-standing goal in nanoscience. In this study, we use DNA origami as a letterpress printing plate and gold nanoparticles as ink to produce predesigned gold nanostructures. The letterpress plate is reusable, enabling the repetitive production of predesigned gold nanostructures. Furthermore, by modifying the DNA origami letterpress plate on magnetic beads, we can simplify the printing processes. We have successfully printed gold nanoparticle dimers, trimers, straight and quadrilateral tetramers, and other nanostructures. Our approach improves the flexibility and stability of metallic nanostructures, simplifying both their design and their operation. It promises universal applicability in the fabrication of metamaterials, biosensors, and surface plasma nanooptics.

Advances in three dimensional metal enhanced fluorescence based biosensors using metal nanomaterial and nano-patterned surfaces.

Metal enhanced fluorescence (MEF) is a phenomenon that increases fluorescence signal through placement of metal near a fluorophore. For biosensing applications, MEF-based biosensors are becoming increasingly popular as it enables highly sensitive detection of molecules, important for early diagnosis. The structure and size of the metal influence the optical properties through enhancing the fluorophore photostability and light absorption and emission. In recent years, many metal nanostructures have been fabricated and examined for their effectiveness in developing MEF-based biosensors. This review focuses on the latest applications of three-dimensional nanostructures and nano-patterned surfaces used to develop and improve fluorescence sensing via MEF. Current reviews mostly discussed the applications of two dimensional MEF and metal-nanoparticles-based MEF with a focus on fabrication of nanoparticles and metal substrates. In this article, we focused more on the effect of the metal nanostructure and size on MEF and then provided an in-depth summary of the performance of the state-of-the-art three dimensional MEF-based biosensors. While more work is needed to demonstrate applicability for complex samples, it is evident that with the use of metal nanoparticles and three dimensional nano-patterns, the assay sensitivity of fluorescence-based detection can be greatly improved, making it suitable for use in early disease diagnostics.

Oxidation-induced superelasticity in metallic glass nanotubes.

Although metallic nanostructures have been attracting tremendous research interest in nanoscience and nanotechnologies, it is known that environmental attacks, such as surface oxidation, can easily initiate cracking on the surface of metals, thus deteriorating their overall functional/structural properties1-3. In sharp contrast, here we report that severely oxidized metallic glass nanotubes can attain an ultrahigh recoverable elastic strain of up to ~14% at room temperature, which outperform bulk metallic glasses, metallic glass nanowires and many other superelastic metals hitherto reported. Through in situ experiments and atomistic simulations, we reveal that the physical mechanisms underpinning the observed superelasticity can be attributed to the formation of a percolating oxide network in metallic glass nanotubes, which not only restricts atomic-scale plastic events during loading but also leads to the recovery of elastic rigidity on unloading. Our discovery implies that oxidation in low-dimensional metallic glasses can result in unique properties for applications in nanodevices.

Adsorption behavior of pyridaben on silver surface and detection of pyridaben residues in apple

It is widely accepted that the sensitivity of SERS is mainly manipulated by the interactions between analyte molecules and metallic nanostructures. Herein, the adsorption behavior of pyridaben on silver surface was investigated systematically by DFT simulation and SERS verification for the first time. The adsorption site and ideal adsorption model of pyridaben were predicted by the simulate parameters of pyridaben, pyridaben-Ag3, pyridaben-Ag4, and pyridaben-Ag6 obtained by DFT calculation, and the enhancement mechanism of Raman characteristic peaks was analyzed by comparing the Raman spectra of pyridaben and pyridaben-Ag4 complex. The results showed that pyridaben was mainly vertically adsorbed on silver surface through the S atom of pyridaben. The adsorption model of pyridaben-Ag4 complex was more stable, and SERS enhancement effect of pyridaben originated from the charge transfer effect between pyridaben molecule and Ag4 cluster. Further, the potential practical application of the adsorption behavior study was evaluated by residue detection of pyridaben in apple. The method showed low LOD of 0.08 mg/kg, the linear range was 0.10–10.00 mg/kg, recovery ranged from 79.71 % to 113.98 %, and RSD was less than 16.16 %. These results promoted the application of SERS technology in pesticides residue detection.

Methanol steam reforming for hydrogen production driven by an atomically precise Cu catalyst

Plasmon-induced hot-electron transfer from metal nanostructures is being intensely pursed in current photocatalytic research, however it remains elusive whether molecular-like metal clusters with excitonic behavior can be used as light-harvesting materials in solar energy utilization such as photocatalytic methanol steam reforming. In this work, we report an atomically precise Cu13 cluster protected by dual ligands of thiolate and phosphine that can be viewed as the assembly of one top Cu atom and three Cu4 tetrahedra. The Cu13H10(SR)3(PR’3)7 (SR = 2,4-dichlorobenzenethiol, PR’3 = P(4-FC6H4)3) cluster can give rise to highly efficient light-driven activity for methanol steam reforming toward H2 production.

Switchable rotation of metal nanostructures in an intensity chirality-invariant focus field.

Light-induced rotation is a fundamental motion form that is of great significance for flexible and multifunctional manipulation modes. However, current optical rotation by a single optical field is mostly unidirectional, where switchable rotation manipulation is still challenging. To address this issue, we demonstrate a switchable rotation of non-spherical nanostructures within a single optical focus field. Interestingly, the intensity of the focus field is chiral invariant. The rotation switch is a result of the energy flux reversal in front and behind the focal plane. We quantitatively analyze the optical force exerted on a metal nanorod at different planes, as well as the surrounding energy flux. Our experimental results indicate that the direct switchover of rotational motion is achievable by adjusting the relative position of the nanostructure to the focal plane. This result enriches the basic motion mode of micro-manipulation and is expected to create potential opportunities in many application fields, such as biological cytology and optical micromachining.

Boosting the Plasmon-Mediated Electrochemical Oxidation of p-Aminothiophenol with p-Hydroxythiophenol as Molecular Cocatalyst.

Plasmon-mediated electrochemistry is an emerging area of interest in which the electrochemical reactions are enhanced by employing metal nanostructures possessing localized surface plasmon resonance (LSPR). However, the reaction efficacy is still far below its theoretical limit due to the ultrafast relaxation of LSPR-generated hot carriers. Herein, we introduce p-hydroxythiophenol (PHTP) as a molecular cocatalyst to significantly improve the reaction efficacy in plasmon-mediated electrochemical oxidation of p-aminothiophenol (PATP) on gold nanoparticles. Using electrochemical techniques, in situ Raman spectroscopy, and theoretical calculations, we elucidate that the presence of PHTP improves the hot hole-mediated electrochemical oxidation of PATP by 2-fold through the trapping of plasmon-mediated hot electrons. In addition, the selectivity of PATP oxidation could also be modulated by the introduction of PHTP cocatalyst. This tactic of employing molecular cocatalyst can be drawn out to endorse various plasmonic electrochemical reactions because of its simple protocol, high efficiency, and high selectivity.

Maximizing Roughness Factors in Oxide-Derived Copper Coatings through Electrodeposition Parameters for Enhanced Electrocatalytic Performance

The pursuit of novel techniques for obtaining dispersed copper-based catalysts is crucial in addressing environmental issues like decarbonization. One method for producing nanostructured metals involves the reduction of their oxides, a technique that has found widespread use in CO2 electroreduction. Currently, the intrinsic activities of oxide-derived copper electrocatalysts produced via different routes cannot be compared effectively due to the lack of information on electrochemically active surface area values, despite the availability of electrochemical methods that enable estimation of surface roughness for highly dispersed copper coatings. In this study, we aim to explore the potential of oxide-derived copper to achieve a high electrochemically active surface area by examining samples obtained from acetic and lactic acid deposition solutions. Our results revealed that Cu2O oxides had distinct morphologies depending on the electrodeposition solution used; acetate series samples were dense films with a columnar structure, while electrodeposition from lactic acid yielded a fine-grained, porous coating. The roughness factors of the electroreduced films followed linear relationships with the deposition charge, with significantly different slopes between the two solutions. Notably, a high roughness factor of 650 was achieved for samples deposited from lactic acid solution, which represents one of the highest estimates of electrochemically active surface area for oxide-derived copper catalysts. Our results highlight the importance of controlling the microstructure of the electrodeposited oxide electrocatalysts to maximize surface roughness.

Scalable Printing of Metal Nanostructures through Superluminescent Light Projection.

Direct printing of metallic nanostructures is highly desirable but current techniques cannot achieve nanoscale resolutions or are too expensive and slow. Photoreduction of solvated metal ions into metallic nanoparticles is an attractive strategy because it is faster than deposition-based techniques. However, it is still limited by the resolution versus cost tradeoff because sub-diffraction printing of nanostructures requires high-intensity light from expensive femtosecond lasers. Here, this tradeoff is overcome by leveraging the spatial and temporal coherence properties of low-intensity diode-based superluminescent light. The superluminescent light projection (SLP) technique is presented to rapidly print sub-diffraction nanostructures, as small as 210nm and at periods as small as 300nm, with light that is a billion times less intense than femtosecond lasers. Printing of arbitrarily complex 2D nanostructured silver patterns over 30µm×80µm areas in 500ms time scales is demonstrated. The post-annealed nanostructures exhibit an electrical conductivity up to 1/12th that of bulk silver. SLP is up to 480 times faster and 35 times less expensive than printing with femtosecond lasers. Therefore, it transforms nanoscale metal printing into a scalable format, thereby significantly enhancing the transition of nano-enabled devices from research laboratories into real-world applications.