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Synthesizing urea from nitrate and carbon dioxide through an electrocatalysis approach under ambient conditions is extraordinarily sustainable. However, this approach still lacks electrocatalysts developed with high catalytic efficiencies, which is a key challenge. Here, we report the high-efficiency electrocatalytic synthesis of urea using indium oxyhydroxide with oxygen vacancy defects, which enables selective C-N coupling toward standout electrocatalytic urea synthesis activity. Analysis by operando synchrotron radiation-Fourier transform infrared spectroscopy showcases that *CO2NH2 protonation is the potential-determining step for the overall urea formation process. As such, defect engineering is employed to lower the energy barrier for the protonation of the *CO2NH2 intermediate to accelerate urea synthesis. Consequently, the defect-engineered catalyst delivers a high Faradaic efficiency of 51.0%. In conjunction with an in-depth study on the catalytic mechanism, this design strategy may facilitate the exploration of advanced catalysts for electrochemical urea synthesis and other sustainable applications. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) C.Y. acknowledges funding supported by the National Natural Science Foundation of China (Grant 52101246) and the Fundamental Research Funds for the Central Universities (Grant 5710010721). Q.Y. acknowledges funding support from Singapore MOE AcRF Tier 1 Grant 2020-T1-001-031 and Singapore A*STAR project A19D9a0096. G.Y. acknowledges funding support from the Camille Dreyfus TeacherScholar Award and Welch Foundation Award F-1861. The authors acknowledge computing resources from the National Supercomputing Centre, Singapore. This work is also supported by the Users with Excellence program of Hefei Science Center of CAS (2020HSC-UE003) and the Fundamental Research Funds for the Central Universities (WK2310000099).

We herein report aqueous fabrication of well-defined Au@Cu2–xE (E = S, Se) core@shell dual plasmonic supraparticles (SPs) for multimodal imaging and tumor therapy at the in vivo level. By means of a modified self-limiting self-assembly based strategy, monodisperse core@shell dual plasmonic SPs, including spherical Au@Cu2–xS SPs, Au@Cu2–xSe SPs, and rod-like Au@Cu2–xS SPs, are reliably and eco-friendly fabricated in aqueous solution. Due to plasmonic coupling from the core and shell materials, the as-prepared hybrid products possess an extremely large extinction coefficient (9.32 L g–1 cm–1 for spherical Au@Cu2–xS SPs) at 808 nm, which endows their excellent photothermal effect. Furthermore, the hybrid core@shell SPs possess the properties of good biocompatibility, low nonspecific interactions, and high photothermal stability. So, they show favorable performances for photoacoustic imaging and X-ray computed tomography imaging as well as photothermal therapy of tumors, indicating their application potential...

Tailoring optical properties of artificial metamaterials, whose optical properties go beyond the limitations of conventional and naturally occurring materials, is of importance in fundamental research and has led to many important applications such as security imaging, invisible cloak, negative refraction, ultrasensitive sensing, and transformable and switchable optics. Herein, by precisely controlling the size, symmetry, and topology of alphabetical metamaterials with U, S, Y, H, U-bar, and V shapes, we have obtained highly tunable optical response covering visible-to-infrared (vis-NIR) optical frequency. In addition, we show a detailed study on the physical origin of resonance modes, plasmonic coupling, the dispersion of resonance modes, and the possibility of negative refraction. We have found that all the electronic and magnetic modes follow the dispersion of surface plasmon polaritons; thus, essentially they are electronic- and magnetic-surface-plasmon-polaritons-like (ESPP-like and MSPP-like) modes resulted from diffraction coupling between localized surface plasmon and freely propagating light. On the basis of the fill factor and formula of magnetism permeability, we predict that the alphabetical metamaterials should show the negative refraction capability in visible optical frequency. Furthermore, we have demonstrated the specific ultrasensitive surface enhanced Raman spectroscopy (SERS) sensing of monolayer molecules and femtomolar food contaminants by tuning their resonance to match the laser wavelength, or by tuning the laser wavelength to match the plasmon resonance of metamaterials. Our tunable alphabetical metamaterials provide a generic platform to study the electromagnetic properties of metamaterials and explore the novel applications in optical frequency.

We report a new strategy to pattern plasmonic nanoparticles into multiplexed one-dimensional arrays based on the spatially modulated electrostatic potential. The 32 nm Au nanoparticles can be simultaneously deposited on one chip with tunable interparticle distance by solely adjusting the width of the grooves. Furthermore, 32 and 13 nm Au nanoparticles can be selectively deposited in grooves of different widths on one chip. As a result, the surface plasmon absorption bands on the chip can be tuned depending on the interparticle distance or the particle size of multiplex 1D arrays, which could enhance the Raman scattering cross section of the adsorbed molecules and result in multiplex surface-enhanced Raman scattering (SERS) response on the chip. This strategy provides a general method to fabricate 1D multiplex arrays with different particle sizes and interparticle distances on one chip.

Near-field scanning optical microscopy images of solid wall, circular, and elliptical microscale corrals show standing wave patterns confined inside the structures with a wavelength close to that of the incident light. The patterns inside the corrals can be tuned by changing the size and material of the walls, the wavelength of incident light, and polarization direction for elliptical corrals. Finite-difference time-domain calculations of the corral structures agree with the experimental observations and reveal that the electric and magnetic field intensities are out of phase inside the corral. A theoretical modal analysis indicates that the fields inside the corrals can be attributed to p- and s-polarized waveguide modes, and that the superposition of the propagating and evanescent modes can explain the phase differences between the fields. These experimental and theoretical results demonstrate that electromagnetic fields on a dielectric surface can be controlled in a predictable manner.

We report a novel method for synthesizing silver-based nanodisk code (NDC) structures using on-wire lithography, where we employ milder synthetic and etching conditions than those used to synthesize the analogous gold structures. The silver structures exhibit stronger surface-enhanced Raman scattering signals than their Au counterparts at 633 and 532 nm excitation and, therefore, lead to lower limits of detection when used in the context of DNA-based detection assays. Finally, use of two enhancing nanostructured materials in one disk code dramatically increases the information storage density for encoding. For example, a disk code consisting of 5 gold disk pairs has 13 unique combinations of enhancing patterns, while one with 5 disk pairs that can be either gold or silver has 98.

This paper describes the fabrication of plasmonic focusing, free-standing rod−sheath hetero-nanostructures based on electrochemical templated synthesis and selective chemical etching. These hetero-nanostructures take advantage of plasmon interference together with field enhancements due to sharp junction structures to function as stand-alone SERS substrates containing Raman hot spots at the interface of the rod and sheath segments. This result is investigated with empirical and theoretical (discrete dipole approximation, DDA) methods, and we show how plasmon interference can be tuned by varying the sheath and rod lengths.