Metal atoms dispersed on the oxide supports constitute a large category of single-atom catalysts. In this review, oxide supported single-atom catalysts are discussed about their synthetic procedures, characterizations, and reaction mechanism in thermocatalysis, such as water–gas shift reaction, selective oxidation/hydrogenation, and coupling reactions. Some typical oxide materials, including ferric oxide, cerium oxide, titanium dioxide, aluminum oxide, and so on, are intentionally mentioned for the unique roles as supports in anchoring metal atoms and taking part in the catalytic reactions. The interactions between metal atoms and oxide supports are summarized to give a picture on how to stabilize the atomic metal centers, and rationally tune the geometric structures and electronic states of single atoms. Furthermore, several directions in fabricating single-atom catalysts with improved performance are proposed on the basis of state-of-the-art understanding in metal-oxide interactions.

Single-atom catalysts (SACs) have demonstrated superior catalytic performance in numerous heterogeneous reactions. However, producing thermally stable SACs, especially in a simple and scalable way, remains a formidable challenge. Here, we report the synthesis of Ru SACs from commercial RuO 2 powders by physical mixing of sub-micron RuO 2 aggregates with a MgAl 1.2 Fe 0.8 O 4 spinel. Atomically dispersed Ru is confirmed by aberration-corrected scanning transmission electron microscopy and X-ray absorption spectroscopy. Detailed studies reveal that the dispersion process does not arise from a gas atom trapping mechanism, but rather from anti-Ostwald ripening promoted by a strong covalent metalsupport interaction. This synthetic strategy is simple and amenable to the large-scale manufacture of thermally stable SACs for industrial applications.

In 1860s, Gustav Kirchhoff proposed his famous law of thermal radiation, setting a fundamental contradiction between the infrared reflection and thermal radiation. Here, for the first time an ultrathin plasmonic metasurface is proposed to simultaneously produce ultralow specular reflection and infrared emission across a broad spectrum and wide incident angle range by combining the low emission nature of metal and the photonic spin-orbit interaction in spatially inhomogeneous structures. As a proof-of-concept, a phase gradient metasurface composed of sub-wavelength metal gratings is designed and experimentally characterized in the infrared atmosphere window of 8-14 µm, demonstrating an ultralow specular reflectivity and infrared emissivity below 0.1. Furthermore, it is demonstrated that infrared illusion could be generated by the metasurface, enabling not only invisibility for thermal and laser detection, but also multifunctionalities for potential applications. This technology is also scalable across a wide range of electromagnetic spectrum and provides a feasible alternative for surface coating.

Poor aspect profiles of plasmonic lithography patterns are suffering from evanescent waves' scattering loss in metal films and decaying exposure in photoresist. To address this issue, we experimentally report plasmonic cavity lens to enhance aspect profile and resolution of plasmonic lithography. The profile depth of half-pitch (hp) 32 nm resist patterns is experimentally improved up to 23 nm, exceeding in the reported sub-10 nm photoresist depth. The resist patterns are then transferred to bottom resist patterns with 80 nm depth using hard-mask technology and etching steps. The resolution of plasmonic cavity lens up to hp 22 nm is experimentally demonstrated. The enhancement of the aspect profile and resolution is mainly attributed to evanescent waves amplifying from the bottom silver layer and scattering loss reduction with smooth silver films in plasmonic cavity lens. Further, theoretical near-field exposure model is utilized to evaluate aspect profile with plasmonic cavity lens and well illustrates the experimental results.

CommuniCation(1 of 6) 1600829 and immune to bleach, thus hold great potentials in display, [6,7] anticounterfeiting technology, [19] etc.Structural colors are typically produced by diffractive gratings (with or without guided mode resonance (GMR)), [20][21][22] Fabry-Pérot cavity, [18] photonic crystals (PCs), [23,24] plasmonics, [1,[25][26][27] etc. Dynamic color tuning is a very important and fascinating direction in the field of structural colorations, because of its possible applications in stealthy, anticounterfeiting and displaying techniques. The resonant wavelengths of filters based on GMR effect are very sharp, resulting in high purity and brightness colors. Dynamic tuning of the GMR can be achieved by adopting the index-tunable materials as the waveguide layers. However, the possible color tuning gamut might be limited without the large index changes. Alternatively, the interferometric modulator display, a type of Fabry-Pérot cavity, can achieve the dynamic tunability of spectra via gap changing of the cavity controlled by the microelectromechanical system. This can produce a continuously varying color in the whole visible range, [18] but the strategy requires a complex controlling system, which is unfavorable for optoelectronic integration. The PCs can also provide dynamically tunable capability of the resonant wavelengths with the change of refractive indices of dielectrics in PC structures. [23,24] Plasmonics is known to offer a platform for transformative applications in optical frequency. [28][29][30][31] Nevertheless, plasmon in conventional nanoscale metallic systems cannot easily support the dynamical tunability because of the rigid structures or devices, except when it is composed of some certain materials or compound structures with tunable properties, such as optoelectronic or electrochemical materials, graphene, etc. [32][33][34][35][36] Herein, we propose and demonstrate a method to create actively tunable structural color based on tensile substrate, [37][38][39][40] i.e., polydimethylsiloxane (PDMS). PDMS, one of the most widely used silicon-based organic polymer, is particularly known for its unusual properties, [41] such as inert, nontoxic, and nonflammable. Taking advantage of the viscoelastic [42] and chemical stable [43] properties, elastic deformations (e.g., tension) of PDMS can be easily occurred under the external force. Therefore, the period of the structure on PDMS will change simultaneously, which causes the dynamic tuning of the surface plasmon resonance (SPR) wavelength, as the phase-matching condition changes. Moreover, compared to the previous dielectric-PDMS composed

By utilizing a reflective plasmonic slab, it is demonstrated numerically and experimentally in this paper deep sub-wavelength imaging lithography for nano characters with about 50 nm line width and dense lines with 32 nm half pitch resolution (about 1/12 wavelength). Compared with the control experiment without reflective plasmonic slab, resolution and fidelity of imaged resist patterns are remarkably improved especially for isolated nano features. Further numerical simulations show that near field optical proximity corrections help to improve imaging fidelity of two dimensional nano patterns.

Nanofabrication technology with high-resolution, high-throughput and low-cost is essential for the development of nanoplasmonic and nanophotonic devices. At present, most metasurfaces are fabricated in a point by point writing manner with electron beam lithography or a focused ion beam, which imposes a serious cost barrier with respect to practical applications. Near field optical lithography, seemingly providing a high-resolution and low-cost way, however, suffers from the ultra shallow depth and poor fidelity of obtained photoresist patterns due to the exponential decay feature of evanescent waves. Here, we propose a method of surface plasmonic imaging lithography by introducing a reflective plasmonic lens to amplify and compensate evanescent waves, resulting in the production of nano resist patterns with high fidelity, contrast and enhanced depth beyond that usually obtained by near field optical lithography. As examples, a discrete and anisotropically arrayed nano-slots mask pattern with different orientations and a size of 40 nm × 120 nm could be imaged in photoresist and transferred successfully onto a metal layer through an etching process. Evidence for the pattern quality is given by virtue of the fabricated metasurface lens devices showing good focusing performance in experiments. It is believed that this method provides a parallel, low-cost, high-throughput and large-area nanofabrication route for fabricating nanostructures of holograms, vortex phase plates, bio-sensors and solar cells etc.

Abstract:Structural colors emerge when a particular wavelength range is filtered out from a broadband light source. It is regarded as a valuable platform for color display and digital imaging due to the benefits of environmental friendliness, higher visibility, and durability. However, current devices capable of generating colors are all based on direct transmission or reflection. Material loss, thick configuration, and the lack of tunability hinder their transition to practical applications. In this paper, a novel mechanism that generates high-purity colors by photon spin restoration on ultrashallow plasmonic grating is proposed. We fabricated the sample by interference lithography and experimentally observed full color display, tunable color logo imaging, and chromatic sensing. The unique combination of high efficiency, highpurity colors, tunable chromatic display, ultrathin structure, and friendliness for fabrication makes this design an easy way to bridge the gap between theoretical investigations and daily-life applications.