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Simultaneously tuning light absorption wavelength and absorbance is a critical challenge in photoelectric detection, mimic of photosynthesis, and simulation of photoreceptors in some animals' retinas. Here, highly ordered hexagonal nanostructured Si arrays are fabricated using monolayer colloid crystal templates. A quantitative relationship between geometric size and light absorption is unveiled in the Si arrays, namely double‐quarter‐wavelength resonance (DQWR). Based on the DQWR model, the absorption wavelength can be readily tuned from 200 to 2400 nm, and the absorbance can be enhanced from ≈80% to above 99% in the full spectrum. Due to the hemisphere‐shell structural feature of the Si arrays, excellent omnidirectional antireflective performance can also be realized. Most importantly, the outstanding antireflection performance of the nanostructures is independent of the substrate. The results not only have important implications for understanding the antireflective mechanism of the nanostructured arrays, but also endow the approach promising in diverse applications, including biomimicry, antireflective film, infrared imagery, and other optoelectronic devices. [ABSTRACT FROM AUTHOR]

Abstract Exploiting effective photocatalytic materials especially co-catalysts is an effective solution to enhance solar hydrogen generation. In this work, we firstly introduce FeSe as highly efficient co-catalyst on the surface of CdS nanoparticles for photocatalytic H 2 evolution under visible light irradiation. The optimized 2 wt% FeSe/CdS composite showed the highest photocatalytic H 2 evolution activity of 204.4 μL/h with an apparent quantum efficiency of 6.71% at 420 nm, which is about 7 times higher than that of pure CdS nanoparticles. More importantly, 2 wt% FeSe/CdS composite also exhibits higher photocatalytic activity than that of 2 wt% Pt/CdS composite under the same condition. The higher photocatalytic H 2 evolution property of FeSe/CdS composite is due to that the photo-generated electrons can be driven by the build-in field and transferred to the surface of FeSe causing electron-hole separation. This work may provide the potential applications of FeSe as a co-catalyst for photocatalytic H 2 evolution. Graphical abstract Image 1 Highlights • FeSe/CdS composites have been successfully synthesized. • The photocatalytic H 2 evolution activity of FeSe/CdS composite is about 7 times of pure CdS nanoparticles. • The photo-generated electrons can be driven by build-in field and transferred to the surface of FeSe. [ABSTRACT FROM AUTHOR]

A new porous material, alveolate Cu2−xSe microsheets, was synthesized through a simple one-step solvothermal process. The surface morphology and microstructure of the as-prepared Cu2−xSe were characterized by various techniques. It was found that the as-synthesized Cu2−xSe has hierarchical porosity composed of mesopores and macropores, and rich active surfaces of {111} facets. A noteworthy visible-light-responsive photocatalytic discoloration of Rhodamine B was observed for the as-developed alveolate Cu2−xSe microsheets. The superior photocatalytic properties demonstrated by the as-synthesized Cu2−xSe are mainly attributed to the highly accessible active surfaces of the {111} facets and the wider light absorption range resulting from its narrower band gap. [ABSTRACT FROM AUTHOR]

Solid-state electrical conducting materials can be roughly categorized as superconductors, conductors, and semiconductors, depending on their conducting carriers, resistance, and band structures. This research reports the discovery of super-semiconductors, whose resistivity is 3–10 orders of magnitude lower than conventional semiconductors at room temperature. In addition, there is a transition from a metal state to a super-semiconducting state at near room temperatures, which is accompanied by an increase in hole carrier density and the mobility increase in electrons. For the first time, a hole-dominated carrier metal is observed in nanostructured bimetallic arrays near room temperature, and no other special conditions are required. Such a behavior is due to the generation of hot electrons and holes induced by metal plasmon resonance in the infrared range in the nanostructured bimetallic arrays. Our research empowers metals with semiconductor features and paves the way to realize ultra-low-power metal-based semiconductor devices. [ABSTRACT FROM AUTHOR]

Quantitative identification of mixed-valence metal ions in solution by the distinctive fluorescence responses of graphene quantum dots. [Display omitted] • Quantitative mixed-valence state identification of Fe3+/Fe2+ solution by graphene quantum dots (GQDs). • The real-time monitoring of the dynamic changes in mixed-valence states triggered by the redox process was realized. • This method can be extended to other metal ions (Cr3+/Cr2+ or Cu2+/Cu+) and typically functionalised GQDs. • A universal and facile method for the quantitative mixed-valence state identification of metal ions in a solution. Quantitative identification of mixed-valence metal ions is essential for gaining deeper insights into critical chemical and biological processes in environmental science, chemical engineering, and biological systems. However, a simple approach of quantitative identification mixed-valence metal ions in solution has remained a challenge. In this study, we have experimentally observed a significant linear correlation (R2 = 0.99) between the concentration of high-valence metal ions (using iron ions as an example) and the fluorescence intensity of graphene quantum dots (GQDs). Utilizing the distinct fluorescence responses of GQDs to high-valence and low-valence metal ions, reliable quantitative detection of mixed-valence metal ions has been successfully achieved. Remarkably, we introduced real-time monitoring of mixed-valence metal ions, revealing a shift from a molar ratio of approximately 4.0 to 2.0. Density functional theory calculations have revealed significant differences in charge transfer between high-valence and low-valence states of metal ions adsorbed onto GQDs. Furthermore, the versatility of this method can extend to various types of GQDs and metal ions, highlighting its universal applicability. This work presents a simple, convenient, and cost-effective approach for quantitatively identifying mixed-valence metal ions in solution, offering a new avenue and opportunity for applications in biochemistry, environmental science, catalysis and materials science. [ABSTRACT FROM AUTHOR]

• The correlation between structures and the T c in FeSe-family is presented for the first time. • The distorted FeSe 4 tetrahedron plays an important role in understanding the superconductivity. • The electronic correlation and FS nesting between electron pockets are associated with distorted FeSe 4 tetrahedron. • The crystal structure of N 0.81(1) D 3.24(2) Fe 2 Se 2 is determined by neutron and x-ray powder diffraction. We demonstrate that unique cation, ND 4 (1−δ)+, exists between FeSe layers and induces a large distortion of the FeSe 4 tetrahedron in N 0.81(1) D 3.24(2) Fe 2 Se 2 by neutron and X-ray powder diffraction. The electronic correlations of the Fe 3d electrons and Fe d xy , d yz and d xz band widths could be tuned by changing the FeSe 4 tetrahedron distortion, revealing the importance of lattice distortion to the superconductivity of FeSe-based intercalates. [ABSTRACT FROM AUTHOR]

Graphene-based free-space optical modulators are usually enabled by shifting electrically the resonant frequency of a plasmonic or optical resonator. However, this resonance-shifting approach could lead to a potential loss of the on/off ratio, considering the fact that photodetectors always respond in a spectral range. Here, to modulate directly the amplitude of mid-infrared light, we propose a graphene-based modulator employing a graphene layer and a magnetic plasmonic array. With this novel design, the transmission intensity through the plasmonic array can be modulated in a direct manner without shifting the transmission peak. Magnetic plasmon resonance (MPR) accounts for the observed transmission, while Wood anomaly (WA) is utilized to fix the resonant position. The proposed modulator shows an excellent tolerance upon variation of structure parameters, with an insertion loss as low as 0.7 dB and a typical on/off ratio of 20, as well as a large modulation depth of 95%. This work offers a new route to design graphene-based optical modulators and may find applications in planar optics and the free-space optical (FSO) communication. [ABSTRACT FROM AUTHOR]

ZrO2‐whisker‐reinforced Ti(C,N)‐based cermets were designed and prepared via a vacuum hot‐pressing process. The ZrO2 whisker characteristics and the phase, microstructure and mechanical properties of the cermets were investigated, and the relevant toughening mechanisms were examined. The results indicate that the ZrO2 whiskers retain their morphology and significantly improve the mechanical properties of the cermets. The relative density and hardness decreased slightly with increasing ZrO2 whisker content. At a whisker content of 7.5 wt.%, the fracture toughness and flexural strength reached their maximum values of 7.825 MPa·m1/2 and 1094 MPa, respectively. This enhancement in the mechanical properties is due to stronger bonding between the interfaces through dimples, tearing ridges and whisker pull‐out, in addition to the inhibition of crack propagation via crack deflection, crack branching and crack bridging. [ABSTRACT FROM AUTHOR]

Abstract It is a fascinating question whether it exists and how to explore Co-based high-temperature superconductors, since Co is next to Fe and has just one more electron than Fe. Based on this, SrCo 2 As 2 has attracted great research interest due to its similar magnetic ground state to Fe-based superconductors. Here, we studied the electron doping effect of SrCo 2 As 2 by doping 2.5% Nd at the Sr sites. Our experimental results show that injecting electrons caused by this doping can induce it from paramagnetism to ferromagnetism. The first-principles calculation indicates that the density of states at the Fermi surface is high enough, which tends to be related to ferromagnetism. This work provides a general strategy for inducing ferromagnetism in Stoner paramagnetic systems. Graphical abstract Unlabelled Image Highlights • Injecting a small amount of electrons induces SrCo 2 As 2 from paramagnetism to ferromagnetism. • The first-principles calculations indicate that SrCo 2 As 2 should be in a critical state between paramagnetism and ferromagnetism. • The crystal structure of Sr 0.975 Nd 0.025 Co 2 As 2 is determined by Rietveld refinement method. • This work provides a general strategy for inducing ferromagnetism in Stoner paramagnetic systems. [ABSTRACT FROM AUTHOR]

The effective regulation of the absorption properties of Au nanosphere arrays, as well as effective enhancement of its SERS performance, are of great significance for its applications in the field of optical sensing. In this paper, the polyol synthesis method was used to fabricate monolayer and bilayer periodic Au nanosphere arrays, onto which monolayer graphene was coated, and the optical properties of the obtained composite structures were investigated. The results showed that the coverage of graphene enhances the absorption peak intensities of the monolayer and bilayer Au nanoarrays by up to 32.92%, and the resonance peaks were red-shifted by up to 17 nm. The Raman signals of graphene-covered monolayer and bilayer Au nanosphere composite arrays are 180 and 280 times stronger than that of pristine graphene, due to the combination of chemical enhancement and electromagnetic enhancement. And the detection sensitivity of R6G molecules by graphene-bilayer Au nanosphere composite arrays is 10−6 M. In addition, the staggered stacking of bilayer Au nanosphere arrays can provide more plasmonic hotspots, resulting in higher Raman intensity of the substrate. These results will pave the way for the fabrication of highly efficient SERS substrates by providing various promising candidates. After being covered by monolayer graphene sheets, the intensity of the plasmon resonance absorption peak of Au nanosphere arrays is enhanced and the peak positions are red-shifted. At the same time, the Raman signal strength of the composite arrays is stronger than the original arrays. [Display omitted] • Graphene-monolayer/bilayer Au nanosphere composite arrays were prepared by polyol synthesis and wet transferred method. • The absorption peak intensities of the composite arrays were enhanced by up to 32.92% compared to Au nanosphere arrays. • The Raman signals of the graphene-Au nanosphere composite arrays are 180-280 times stronger than that of pristine graphene. • The detection sensitivity of the graphene-bilayer Au nanosphere composite array for R6G molecules can reach 10−6 mol/L. [ABSTRACT FROM AUTHOR]

In this paper, ultra-fine Ti(C,N)–TiB 2 –Co cermets were prepared by reactive hot processing from the Co–Ti–C–BN system. Microstructure observation indicated that Co and TiB 2 uniformly distributed in the ultra-fine Ti(C,N) matrix. Carbon contents in the reactants had a great influence on the porosity and properties of synthesized cermets. In the range of 11.76–13.79 at.% carbon, dense samples were obtained. With increasing carbon contents, the relative density and hardness decreased due to the existence of residual carbon. The wear resistance of dense Ti(C,N)–TiB 2 –Co cermets were better than that of YT15 cemented carbide. In addition, the reaction process in the Co–Ti–C–BN system was explored by differential scanning calorimeter and X-ray diffraction. Results revealed that Ti(C,N) was synthesized through the solid solution of carbon into TiN, and the addition of Co to Ti–C–BN mixtures promoted the production of Ti(C,N) by the formation of Co–Ti liquid. [ABSTRACT FROM AUTHOR]

With the development of micro-nano optical technology, the fine and effective regulation of the optical properties of nano-arrays by adjusting their structures, sizes and morphologies has become a new research hotspot. In this work, a series of FeGa micro-nano spherical shell arrays with different diameters and thicknesses on polystyrene spheres (PS) templates using magnetron sputtering is synthesized. By applying an external magnetic field perpendicular to the FeGa arrays and adjusting its intensity, the efficient and reversible control of the intensities and positions of light peaks in the optical absorption spectra of the arrays is realized. Among them, the regulation of light absorption can reach ∼15%. Furthermore, the experimental results are in good agreement with the numerical simulation of the multi-physical field coupling analysis. These results will provide a method to control light absorption and contribute to the research and development of emerging optical devices. By adjusting the vertical external magnetic field, the intensities and positions of light peaks in the optical absorption spectra of the FeGa array can be adjusted reversibly and controllably. [Display omitted] • FeGa arrays have been successfully prepared by a combination of colloidal crystal templates and magnetron sputtering. • Adjusting the intensity of vertical external magnetic field can control the light absorption of FeGa arrays reversibly. • The modulation of light absorptivity can reach ∼15%. [ABSTRACT FROM AUTHOR]

• A series of BiVO 4 samples composited with NiSe 2 nanosheets were prepared through a facile solvothermal method. • The photocatalytic degradation rate of RhB of the optimized sample reaches 11 times higher than that of pure BiVO 4. • The Schottky junction derived from the discrepancy of work function accelerates the separation of photogenerated carriers. • The interaction at the interface reduces the band gap of BiVO 4. The rapid recombination of photogenerated carriers limits the photocatalytic activity of BiVO 4. Here, we grew NiSe 2 nanosheets on the surface of BiVO 4 through a facile solvothermal method to construct a Schottky junction. Due to the discrepancy of work function, electrons at the interface are transferred from BiVO 4 to NiSe 2 , thereby forming a built-in electric field. In virtue of the built-in electric field and the good conductivity of NiSe 2 , the photo-generated carriers can be quickly separated and transferred. In addition, the interaction at the interface reduces the band gap of BiVO 4 , which increases the absorption of visible light. These above benefits improve the photocatalytic performance. The photocatalytic reaction under visible light shows that the degradation rate of RhB for 9 mol% NiSe 2 composited BiVO 4 increases by 11 times compared with pure BiVO 4. The simplicity of the preparation method and the significantly improved performance show the enormous potential of NiSe 2 to be coupled with other semiconductor photocatalysts to improve their catalytic activity. [ABSTRACT FROM AUTHOR]

Lamellar MoS 2 has attracted widespread attention as a potential electrocatalytic HER (Hydrogen evolution reaction) catalyst. However, it is difficult to further improve its catalytic activity due to two major drawbacks: the limited number of active sites and its poor conductivity. Here, we adopt a one-step method utilizing an ultrafast pulsed laser treatment to produce multiple decorations on lamellar MoS 2 , where nanocrystallization and amorphization of lamellar MoS 2 are achieved simultaneously, along with an additional characteristic of atomic steps. Due to this special microstructure, laser-treated MoS 2 exhibits excellent electrocatalytic performance with a low overpotential and a small Tafel slope (217 mV @ 10 mA cm−2 and 74.5 mV dec−1, respectively), which is superior to that of untreated lamellar MoS 2 (461 mV @ 10 mA cm−2 and 142.6 mV dec−1, respectively). The MoS 2 prepared in this way has a high catalytic activity and a high stability, which indicates potential for electrocatalysis applications. • We proposed a one-step method using ultrafast pulsed laser treatment to enhance the HER performance of lamellar MoS 2. • We prepared ultra-small MoS 2 nanoparticles, amorphization, and atomic steps in situ on lamellar MoS 2. • The performance of treated MoS 2 is far superior to that of MoS 2 before laser treatment. [ABSTRACT FROM AUTHOR]