The structural blue color of a Morpho butterfly originates from the diffraction of light and interference effects due to the presence of the microstructures on the wing of the butterfly. Structural color on the surface of a damselfish reversibly changes between green and blue. Inspired by these creatures, we have been trying to prepare high-quality and functional structural color films. We describe our efforts in this Account. A useful technique to prepare such structural color films in colloidal solution is a "lifting" method, which allows us to quickly fabricate brilliant colloidal crystal films. The thicknesses of the films can be controlled by precisely adjusting the particle concentration and the lifting speed. Moreover, in order to prepare a complicated structure, we have used template methods. Indeed, we have successfully prepared the inverse structure of the wing of a Morpho butterfly with this technique. Initially, however, our structural color films had a whitish appearance due to the scattering of light by defects in the colloidal crystal film. Later, we were able to prepare a non-whitish structural color film by doping an appropriate dye in the colloidal particles to absorb the scattering light. In addition to the structural blue color, the wing of the Morpho butterfly has superhydrophobic properties. According to Wenzel's equation, the hydrophobic and hydrophilic properties are enhanced when the roughness of the hydrophobic and hydrophilic surface is increased, respectively. Based on this mechanism, we have successfully prepared structural color films with superhydrophobic properties, as well as with superhydrophilic properties. Another important property that can be seen in nature is tunable structural color, such as the color change that can be seen on the surface of a damselfish. In order to mimic such color change, we have developed several tunable structural color films. In particular, we have successfully prepared phototunable photonic crystals using photoresponsive azobenzene derivatives. In order to apply these structural color films, we developed a technique for patterning them by taking advantage of the wettability of the substrate surface. These materials can be used in the future for self-cleaning pigments and tunable photonic crystals.

Multiresponsive elastic poly(methyl methacrylate-butyl acrylate) (P(MMA-BA)) copolymer nanoparticles with controlled sizes are fabricated through a onestep method, which further serve as building blocks for the construction of multiresponsive films via self-assembly. Taking advantage of the relatively low glass transition temperature and the core-shell structure of the copoly mer nanoparticles, they possess the capacity to partially deform and fuse at room temperature under dry status, eventually resulting in the enhancement of the mechanical properties as well as the control of optical properties in the assembled ordered structures. The generated elastic films not only can control the concealment or exhibition of the designed color information, but also can rapidly respond to external stimuli such as the solvent, pH, and tensile force in a reversible fashion. These functional elastic copolymer nanoparticles have potential applications in dynamic color display, optical sensing, and anticounterfeiting.

Biochar, also known as black carbon, is a byproduct of biomass pyrolysis. As a low-cost, environmental-friendly material, biochar has the potential to replace more expensive synthesized carbon nanomaterials (e.g. carbon nanotubes) for use in future supercapacitors. To achieve high capacitance, biochar requires proper activation. A conventional approach involves mixing biochar with a strong base and baking at a high temperature. However, this process is time consuming and energy inefficient (requiring temperatures >900°C). This work demonstrates a low-temperature (<150°C) plasma treatment that efficiently activates a yellow pine biochar.Particularly, the effects of oxygen plasma on the biochar microstructure and supercapacitor characteristics are studied. Significant enhancement of the capacitance is achieved: 171.4 F g -1 for a 5-minute oxygen plasma activation, in comparison to 99.5 F g -1 for a conventional chemical activation and 60.4 F g -1 for untreated biochar. This enhancement of the charge storage capacity is attributed to the creation of a broad distribution in pore size and a larger surface area. The plasma activation mechanisms in terms of the evolution of the biochar surface and microstructure are further discussed.

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Here, we reported a strategy of using an eggshell membrane to produce hierarchically porous carbon as a low-cost substrate for synthesizing nano nickel oxide catalyst (C@NiO), which can effectively turn biowaste -urea into energy through an electrochemical approach. The interwoven carbon networks within NiO led to highly efficient urea oxidation due to the strong synergistic effect. The as-prepared electrode only needed 1.36 V versus reversible hydrogen electrode to realize high efficiency of 10 mA cm -2 in 1.0 M KOH with 0.33 M urea and delivered an even higher current density of 25 mA cm -2 at 1.46 V, which is smaller than that of the porous carbon and commercial Pt/C catalyst. Benefiting from theoretical calculations, Ni(III) active species and the porous carbon further enabled the electrocatalyst to effectively inhibit the "CO2 poisoning" of electrocatalysts, as well as ensuring its superior performance for urea oxidation.

It has been a challenge to use transition metal oxides as anode materials in Li-ion batteries due to their low electronic conductivity, poor rate capability and large volume change during charge/discharge processes. Here, we present the first demonstration of a unique self-recovery of capacity in transition metal oxide anodes. This was achieved by reducing tungsten trioxide (WO3) via the incorporation of urea, followed by annealing in a nitrogen environment. The reduced WO3 successfully self-retained the Li-ion cell capacity after undergoing a sharp decrease upon cycling. Significantly, the reduced WO3 also exhibited excellent rate capability. The reduced WO3 exhibited an interesting cycling phenomenon where the capacity was significantly self-recovered after an initial sharp decrease. The quick self-recoveries of 193.21%, 179.19% and 166.38% for the reduced WO3 were observed at the 15th (521.59/457.41 mA h g-1), 36th (538.49/536.61 mA h g-1) and 45th (555.39/555.39 mA h g-1) cycles respectively compared to their respective preceding discharge capacity. This unique self-recovery phenomenon can be attributed to the lithium plating and conversion reaction which might be due to the activation of oxygen vacancies that act as defects which make the WO3 electrode more electrochemically reactive with cycling. The reduced WO3 exhibited a superior electrochemical performance with 959.1/638.9 mA h g-1 (1st cycle) and 558.68/550.23 mA h g-1 (100th cycle) vs. pristine WO3 with 670.16/403.79 mA h g-1 (1st cycle) and 236.53/234.39 mA h g-1 (100th cycle) at a current density of 100 mA g-1.

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Colored beads: Monodisperse colloidal crystal beads with structural colors are used for multiplex immunoassay as encoded biomolecular supports. Mouse, rabbit, and human immunoglobulin G (IgG) are immobilized on blue, green, and red beads, respectively, and incubated with the analyte. The fluorescence peaks for the blue and green beads imply that the analyte contains tagged antimouse IgG and antirabbit IgG only (see picture).