Arrays of NiCo2S4 nanotubes on nickel foam were prepared by means of a two‐step method, and were directly applied as a binder‐free supercapacitor electrode. Such a binder‐free method enables intimate contact between the current collector and the active materials, and can effectively improve ion and charge transportation. As a result, the electrochemical performances of supercapacitors can be improved. The as‐prepared NiCo2S4 nanotubes/Ni foam electrode shows a high specific capacitance (738 F g−1 at 4 A g−1), excellent rate capability (78 % capacitance retention at 32 A g−1), and good cycling stability (retention capacity of 93.4 % after 4000 cycles), which suggests its promising application for electrochemical capacitors.

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We propose and investigate a photonic crystal fiber (PCF) refractive index sensor with triangular lattice and four large-size channels based on surface plasmon resonance. In such sensor, two gold wires obtained by chemical reaction are filled in two air holes between the upper and lower channels. Numerical results show that the refractive indexes of the analytes can be detected from 1.30 to 1.79. It's a very broad detection range that is rarely seen in the field of photonic crystal fiber sensor based on surface plasmon resonance. The average sensitivity of this photonic crystal fiber could be 100 nm/refractive index unit (RIU) in the dynamic index range from 1.30 to 1.63. In the range from 1.63 to 1.79, the highest sensitivity could reach to 3233 nm/RIU. The ability to integrate four largesize microfluidic channels for efficient analyte flow in is attractive for the development of integrated highly sensitive PCF-SPR sensors.