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Nanoflakes Co(OH) 2 porous films have been successfully electrochemical deposited on nickel foam substrate from cobalt nitrate dissolved in water and water-ethanol (1:1 volume ratio) solutions, respectively. Field emission scanning electron microscope (FESEM) studies indicate that the films electrodeposited from both solutions have nanoflakes porous structure. Cyclic voltammetry (CV) and galvanostaitc charge/discharge measurements show that the Co(OH) 2 films electrode deposited in water-ethanol solution has excellent electrochemical capacitance between a potential range of 0-0.4 V, and the maximum specific capacitance as high as 2369 F g -1 could be achieved in 2 M KOH solution at a charge-discharge current density of 2 A g -1 , suggesting its potential application in the electrode material for electrochemical capacitors. Meanwhile, the properties of the nanoflakes Co(OH) 2 porous films electrodeposited in water solution are also discussed for comparison.

The Pancharatnam–Berry (PB) phase, subject to geometric phase, is currently utilized to implement spin-dependent optical functions. Simultaneously achieving spin-multiplexing and varifocal performances via a single-cell-designed metasurface that purely relies on PB phases has been scarcely proposed due to the quite sophisticated degrees of freedom to be taken into account. Here, by virtue of pure PB phases composed of convex and concave phases, spin-multiplexing and varifocal metalenses based on a single-cell-designed approach are developed. The unit cell consists of Ge2Sb2Se4Te1 (GSST) nanopillar pairs setting on CaF2 substrate. By adopting the specified pure PB phases, the proposed metalenses can focus the left-handed and right-handed circularly polarized (LCP and RCP) incidences into different positions. By ingenious design, the Ge2Sb2Se4Te1-based unit cell can work like a half-wave plate at two wavelength bands depending on the Ge2Sb2Se4Te1 phase states, enabling the proposed metalenses phase-driven zoom focusing. Particularly, the unique phase transition of GSST empowers the proposed schemes with binary switching focusing merit and large switching contrast ratio. The new design strategy constitutes a novel avenue in designing spin-multiplexing and varifocal optical devices, showing great potential in imaging, optical storage and optical interconnections.

We experimentally investigate effects of W6+ occupying the sites of Sc3+ in the unit cell of Sc2W3O12 (Sc8W12O48) on the structure, vibration and thermal expansion. The composition and structure of the doped sample (Sc6W2)W12O48 ± δ (with two W6+ occupying two sites of Sc3+ in the unit cell of Sc8W12O48) are analyzed and identified by combining the x-ray photoelectron spectroscopy and the synchronous x-ray diffraction with first-principles calculations based on density functional theory. Results show that the crystal with even W6+ occupying even Sc3+ in the unit cell is stable and maintains the orthorhombic structure at room temperature. The structure of the doped sample is similar to that of Sc2W3O12, and with even W occupying even positions of Sc in the unit cell and constituting the WO6 octahedra. Raman analyses show that the doped sample possesses stronger W–O bonds and wider Raman linewidths than those of Sc2W3O12. The sample doped with W also exhibits intrinsic negative thermal expansion in the measured range of 150 K–650 K.

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