Bioinspired organic/inorganic hybrid one-dimensional photonic crystals (1DPCs) are prepared by alternating thin fi lms of titania and poly(2-hydroxyethyl methacrylate-co-glycidyl methacrylate) (PHEMA-co-PGMA) by spincoating, which is a simple, reproducible, and low-cost approach. Their optical properties are tuned by changing the number of layers, incident angles, and the thickness of the layers. The color of the 1DPCs can span the entire visible spectral range when the period or the refractive index is changed. Due to the response of PHEMA-co-PGMA to water vapor, the 1DPCs possess fast water-vapor responsiveness and reversible full-color switching. The color of the 1DPCs varies from blue to green, yellow, orange, and red under differing humidities, covering the whole visible range. At high water-vapor concentrations, the color of the 1DPCs rapidly changes from blue to red and comes back to the original state immediately after exposure to air; this behaviour is like that of some animals in nature. The repeatability of the reversible response of the 1DPCs to water vapor is perfect and can be repeated more than 100 times. The as-prepared 1DPCs successfully combine structural color and water-vapor sensitivity, which is promising for use as materials for colorful detection across the full color range.

In this paper, we report our recent work on preparing two-dimensional patterned microstructure arrays using three-dimensional colloidal crystals as templates, namely, colloidal crystal-assisted lithography. Two alternative processes are described and involved in colloidal crystal-assisted lithography. One is based upon imprinting the polymer films with three-dimensional silica colloidal crystals, and the other is based upon chemically depositing Ag microstructures on Au substrates covered by polymer colloidal crystals. By varying the experimental conditions in the colloidal crystal-assisted lithography process, we can intentionally control the morphologies of the resulting microstructures. The resultant Ag-coated Au substrates can be used as surface-enhanced Raman scattering substrates, and they would provide an ideal system for the mechanism study of surface-enhanced Raman scattering. We expect that colloidal crystal-assisted lithography will be a versatile approach which can be applied to patterning other materials such as functional molecules, polymers, oxides, and metals.

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Single-crystal LiKGdF5: Er3+, Tb3+ was synthesized by using hydrothermal techniques. After measuring luminescence and excitation spectra, we observed the up-converted green (, ) and red () emissions, as well as the weak blue emissions from Er3+ ions in the crystal. Analysis indicates that the blue up-conversion occurs via a sequential absorption of three photons. By assuming the ion is in a C2V instead of the actual C2 site, a crystal-field (cf) calculation has been performed on the reduced7FJ basis of the ground7F term of the Tb3+ ion. Excellent correlation was obtained between the experimental transition energies and the computed level structures. The cf parameter obtained is very well transferable to the Er3+ energy levels in LiKGdF5.

This paper partitions the arm current of MMC into uncontrollable current and controllable current. The former is determined by the load that can't be controlled by taking any control strategy. The later caused by the unbalanced total inserted voltage of three arms can be controlled by some improved algorithms. The conclusion based on the researching the essence of circulating current is reached that change the number of the inserted sub-modules in each phase can suppress the circulating current. Combined with the improved ladder wave modulation, a novel circulating current suppression strategy particularly for the inverter station is developed. The improved strategy can adapt to load changes and reduce the circulating current and output voltage THD of MMC ac terminals greatly without increasing any peripheral circuits. Finally, the simulation model of 100 submodules in each phase is constructed in MATLAB and the simulation results verify the correctness and effectiveness of the modified control algorithm.