Hindered gas bubble release and limited electron conducting process represent the major bottlenecks for large‐scale electrochemical water splitting. Both the desorption of bubbles and continuous ...electron transport are achievable on the surfaces of biomimetic catalytic materials by designing multiscale structural hierarchy. Inspired by the tubular structures of the deep‐sea sponges, an exceptionally active and binder‐free porous nickel tube arrays (PNTA) decorated with NiFe‐Zn2+‐pore nanosheets (NiFe‐PZn) are fabricated. The PNTA facilitate removal of bubbles and electron transfer in the oxygen evolution reaction by reproducing trunks of the sponges, and simultaneously, the NiFe‐PZn increase the number of catalytic active sites by simulating the sponge epidermis. With improved external mass transfer and interior electron transfer, the hierarchical NiFe‐PZn@PNTA electrode exhibits superior oxygen evolution reaction performance with an overpotential of 172 mV at 10 mA cm−2 (with a Tafel slope of 50 mV dec−1). Furthermore, this electrocatalytic system recorded excellent reaction stability over 360 h with a constant current density of 100 mA cm−2 at the potential of 1.52 V (versus RHE). This work provides a new strategy of designing hierarchical electrocatalysts for highly efficient water splitting.
Inspired by the deep‐sea sponges, a hierarchical electrode of porous nickel microtube arrays decorated with 2D NiFe‐Zn2+‐pore nanosheets is fabricated. It exhibits superior OER performance with an overpotential of 172 mV at 10 mA cm−2 and yields a current density of 100 mA cm−2 over 360 h at the potential of 1.52 V (versus RHE).
Soft skin layers on elastomeric substrates are demonstrated to support mechano‐responsive wrinkle patterns that do not exhibit cracking under applied strain. Soft fluoropolymer skin layers on ...pre‐strained poly(dimethylsiloxane) slabs achieved crack‐free surface wrinkling at high strain regimes not possible by using conventional stiff skin layers. A side‐by‐side comparison between the soft and hard skin layers after multiple cycles of stretching and releasing revealed that the soft skin layer enabled dynamic control over wrinkle topography without cracks or delamination. We systematically characterized the evolution of wrinkle wavelength, amplitude, and orientation as a function of tensile strain to resolve the crack‐free structural transformation. We demonstrated that wrinkled surfaces can guide water spreading along wrinkle orientation, and hence switchable, anisotropic wetting was realized.
Wrinkles without the worry: Soft fluoropolymer skin layers on elastomer substrates produced wrinkles that could undergo numerous stretch‐and‐release cycles without delamination or formation of cracks. A side‐by‐side comparison with conventional hard skin layers highlighted the integrity and robustness of wrinkles in a soft skin layer as well as their unique properties such as switchable anisotropic water spreading.
Electrocatalytic water splitting is crucial to generate clean hydrogen fuel, but implementation at an industrial scale remains limited due to dependence on expensive platinum (Pt)‐based ...electrocatalysts. Here, an all‐dry process to transform electrochemically inert bulk WS2 into a multidomain electrochemical catalyst that enables scalable and cost‐effective implementation of the hydrogen evolution reaction (HER) in water electrolysis is reported. Direct dry transfer of WS2 flakes to a gold thin film deposited on a silicon substrate provides a general platform to produce the working electrodes for HER with tunable charge transfer resistance. By treating the mechanically exfoliated WS2 with sequential Ar‐O2 plasma, mixed domains of WS2, WO3, and tungsten oxysulfide form on the surfaces of the flakes, which gives rise to a superior HER with much greater long‐term stability and steady‐state activity compared to Pt. Using density functional theory, ultraefficient atomic sites formed on the constituent nanodomains are identified, and the quantification of atomic‐scale reactivities and resulting HER activities fully support the experimental observations.
This paper reports an approach to maximize the electrocatalytic performance of mechanically exfoliated WS2 through sequential plasma treatments. This dry process can spatially tune the level of surface oxidation as well as the concentration of sulfur vacancies such that compositionally graded, mixed‐domain electrochemical catalysts induced hydrogen evolution reaction performance greater than platinum with high stability over centimeter‐scale areas.
This Perspective focuses on the design of hierarchical structures in deformable thin materials by patterning mechanical instabilities. Fabrication of three-dimensional (3D) structures with multiple ...length scalesstarting at the nanoscalecan result in on-demand surface functionalities from the modification of the mechanical, chemical, and optical properties of materials. Conventional top-down lithography, however, cannot achieve 3D patterns over large areas (>cm2). In contrast, a bottom-up approach based on controlling strain in layered nanomaterials conformally coated on polymeric substrates can produce multiscale structures in parallel. In-plane and out-of-plane structural hierarchies formed by conformal buckling show unique structure–function relationships. Programmable hierarchical surfaces offer prospects to tune global- and local-level characteristics of nanomaterials that will positively impact applications in nanomechanics, nanoelectronics, and nanophotonics.
This paper describes polymeric nanostructures with dynamically tunable wetting properties. Centimeter‐scale areas of monolithic nanoridges can be generated by strain relief of thermoplastic ...polyolefin films with fluoropolymer skin layers. Changing the amount of strain results in polyolefin ridges with aspect ratios greater than four with controlled feature densities. Surface chemistry and topography are demonstrated to be able to be tailored by SF6‐plasma etching to access multiple wetting states: Wenzel, Cassie–Baxter, and Cassie‐impregnating states. Reversible transitions among the wetting states can be realized in a programmable manner by cyclic stretching and reshrinking the patterned substrates without delamination and cracking.
Centimeter‐scale areas of monolithic nanoridges are generated by strain relief of polyolefin films with fluoropolymer skin layers. SF6‐plasma treatment can tailor the surface chemistry and topography of the nanostructures to access multiple wetting states, including Wenzel, Cassie–Baxter, and Cassie‐impregnating states. Reversible transitions between wetting states can be realized in a programmable manner by stretching and reshrinking the patterned substrate.
We report the design of three-dimensional (3D) hierarchical wrinkle substrates that can maintain their superhydrophobicity even after being repeatedly stretched. Monolithic poly(dimethysiloxane) ...with multiscale features showed wetting properties characteristic of static superhydrophobicity with water contact angles (>160°) and very low contact angle hysteresis (<5°). To examine how superhydrophobicity was maintained as the substrate was stretched, we investigated the dynamic wetting behavior of bouncing and splashing upon droplet impact with the surface. On hierarchical wrinkles consisting of three different length scales, superhydrophobic bouncing was observed. The substrate remained superhydrophobic up to 100% stretching with no structural defects after 1000 cycles of stretching and releasing. Stretchable superhydrophobicity was possible because of the monolithic nature of the hierarchical wrinkles as well as partial preservation of nanoscale structures under stretching.
This paper reports a robust and stretchable nanolaser platform that can preserve its high mode quality by exploiting hybrid quadrupole plasmons as an optical feedback mechanism. Increasing the size ...of metal nanoparticles in an array can introduce ultrasharp lattice plasmon resonances with out-of-plane charge oscillations that are tolerant to lateral strain. By patterning these nanoparticles onto an elastomeric slab surrounded by liquid gain, we realized reversible, tunable nanolasing with high strain sensitivity and no hysteresis. Our semiquantum modeling demonstrates that lasing build-up occurs at the hybrid quadrupole electromagnetic hot spots, which provides a route toward mechanical modulation of light-matter interactions on the nanoscale.
Programmable and reversible plasmon mode engineering Yang, Ankun; Hryn, Alexander J.; Bourgeois, Marc R. ...
Proceedings of the National Academy of Sciences - PNAS,
12/2016, Letnik:
113, Številka:
50
Journal Article
Recenzirano
Odprti dostop
Plasmonic nanostructures with enhanced localized optical fields as well as narrow linewidths have driven advances in numerous applications. However, the active engineering of ultranarrow resonances ...across the visible regime—and within a single system—has not yet been demonstrated. This paper describes how aluminum nanoparticle arrays embedded in an elastomeric slab may exhibit high-quality resonances with linewidths as narrow as 3 nm at wavelengths not accessible by conventional plasmonic materials. We exploited stretching to improve and tune simultaneously the optical response of as-fabricated nanoparticle arrays by shifting the diffraction mode relative to single-particle dipolar or quadrupolar resonances. This dynamic modulation of particle–particle spacing enabled either dipolar or quadrupolar lattice modes to be selectively accessed and individually optimized. Programmable plasmon modes offer a robust way to achieve real-time tunable materials for plasmon-enhanced molecular sensing and plasmonic nanolasers and opens new possibilities for integrating with flexible electronics.
Flat metasurfaces with subwavelength meta‐atoms can be designed to manipulate the electromagnetic parameters of incident light and enable unusual light–matter interactions. Although hydrogel‐based ...metasurfaces have the potential to control optical properties dynamically in response to environmental conditions, the pattern resolution of these surfaces has been limited to microscale features or larger, limiting capabilities at the nanoscale, and precluding effective use in metamaterials. This paper reports a general approach to developing tunable plasmonic metasurfaces with hydrogel meta‐atoms at the subwavelength scale. Periodic arrays of hydrogel nanodots with continuously tunable diameters are fabricated on silver substrates, resulting in humidity‐responsive surface plasmon polaritons (SPPs) at the nanostructure–metal interfaces. The peaks of the SPPs are controlled reversibly by absorbing or releasing water within the hydrogel matrix, the matrix‐generated plasmonic color rendering in the visible spectrum. This work demonstrates that metasurfaces designed with these spatially patterned nanodots of varying sizes benefit applications in anti‐counterfeiting and generate multicolored displays with single‐nanodot resolution. Furthermore, this work shows system versatility exhibited by broadband beam‐steering on a phase modulator consisting of hydrogel supercell units in which the size variations of constituent hydrogel nanostructures engineer the wavefront of reflected light from the metasurface.
This paper reports an approach for plasmonic metasurfaces with hydrogel meta‐atoms at the subwavelength scale. Periodic arrays of hydrogel nanodots with tunable diameters are fabricated on silver substrates, resulting in humidity‐responsive surface plasmon polaritons. This work demonstrates that metasurfaces designed with spatially patterned hydrogel nanodots of varying size distributions benefit applications in anti‐counterfeiting, multicolored displays, and a phase modulator.
This paper describes how a memory-based, sequential wrinkling process can transform flat polystyrene sheets into multiscale, three-dimensional hierarchical textures. Multiple cycles of ...plasma-mediated skin growth followed by directional strain relief of the substrate resulted in hierarchical architectures with characteristic generational (G) features. Independent control over wrinkle wavelength and wrinkle orientation for each G was achieved by tuning plasma treatment time and strain-relief direction for each cycle. Lotus-type superhydrophobicity was demonstrated on three-dimensional G1–G2–G3 hierarchical wrinkles as well as tunable superhydrophilicity on these same substrates after oxygen plasma. This materials system provides a general approach for nanomanufacturing based on bottom-up sequential wrinkling that will benefit a diverse range of applications and especially those that require large area (>cm2), multiscale, three-dimensional patterns.
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