the light-responsive properties also have excellent adaptability to the environment. [7] Under the inspiration of these controllable optical properties, a variety of advanced material systems have been proposed significantly. [7,8] However, researchers were simply concentrated in a specific waveband due to the great difficulty to achieve the compatibility of multispectral properties, which greatly hinders advance science and the application fields expanding of novel photonic materials. For example, in order to avoid the detection of microwave radar, infrared detector, and visual observation, the stealth materials on military armament have been separately developed during microwave, infrared, and visible light range; [9][10][11] but the above stealth properties were difficult to be compatible in one weapon, thus, the problem of perfect stealth (stealth during full wavebands) is still not solved to date. Moreover, the material degradation by ultraviolet (UV) radiation also needs to be settled urgently because the weapons are exposed to sunlight all year round. Although metamaterials (MMs) researchers have conducted multibands studies, [12] such as optically transparent microwave absorbing materials, [13] multispectral absorption MMs, [14] and multibands resonators, [15] etc., only two or three bands were involved, and the multibands compatibility has not been deeply explored. When devices worked in real environments, dust particles accumulated on its surface over time, which would have an adverse effect on its light manipulation performance. In order to avoid this problem, it is desirable to integrate a self-cleaning ability induced by hydrophobic property of material into the equipment. [16] In this context, a hierarchical structure model of moth compound eye that might manipulate multibands EMWs was found here, as shown in Figure 1a. [17,18] This is a noctuid moth living in Heilongjiang Province of China; the hierarchical and sub-wavelength structures that are arranged in a highly ordered array of its eye surface could suppress the reflection of light to avoid detection by nocturnal predators and to see clearly in darkness, which is based on rigorous coupled wave analysis (RCWA) and finite difference time domain (FDTD) methods, [19] as well as relative research on moth eye model. [18,20] This feature makes the moth-eye model one of the most effective antireflective structures in nature. Although various photonic devices inspired by natural materials have been developed, there is no research focusing on multibands adaptability, whichis not conducive to the advancement of materials science. Herein, inspired by the moth eye surface model, state-of-the-art hierarchical metamaterials (MMs) used as tunable devices in multispectral electromagnetic-waves (EMWs) frequency range, from microwave to ultraviolet (UV), are designed and prepared. Experimentally, the robust broad bandwidth of microwave absorption greater than 90% (reflection loss (RL) < −10 dB) covering almost entire X and Ku bands (8.04-17.88 GHz) under a de...

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Lignin, a byproduct from the chemical processing of lignocellulosic biomass, is a polyphenolic compound that has potential as a partial phenol substitute in phenolic adhesive formulations. In this study, HBr and HI were used as reagents to demethylate an alkali lignin (AL) to increase its hydroxyl content and thereby enhance its reactivity for the preparation of phenolic resins. Analyses by FT-IR, 1H-NMR and 2D-NMR(HSQC) demonstrated both a decrease in methoxyl groups and an increase in hydroxyl groups for each demethylated lignin (DL). In addition, the molar amounts of phenolic hydroxyls, determined by 1H-NMR, increased to 0.67 mmol/g for the HI-DL, and 0.64 mmol/g for the HBr-DL, from 0.52 mmol/g for the AL. These results showed that HI, a stronger nucleophilic reagent than HBr, provided a higher degree of AL demethylation. Lignin-containing resins, prepared by copolymerization, met the bonding strength standard for exterior plywood with DL used to replace as much as 50 wt.% of phenol. The increased hydroxyl contents resulting from the lignin demethylations also imparted faster cure times for the lignin-containing resins and lower formaldehyde emissions. Altogether, the stronger nucleophilicity of HI, compared to HBr, impacted the degree of lignin demethylation, and carried through to measurable differences the thermal properties and performance of the lignin-containing PF resins.

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Carbon nanotube (CNT)-based Li batteries have attracted wide attention because of their high capacity, high cyclability and high energy density and are believed to be one of the most promising electrochemical energy storage systems. In CNT-based Li batteries, the main interaction between the Li(+) ions and the CNT is the cation-π interaction. However, up to now, it is still not clear how this interaction affects the storage characteristics of CNT-based Li batteries. Here, using density functional theory (DFT) calculations, we report a highly favorable impact of cation-π interactions on the cell voltage of CNT-based Li batteries. Considering both Li(+)-π interaction and Li-π interaction, we show that cell voltage enhances with the increase of the CNT diameter. In addition, when the Li(+) ion adsorbs on the external wall, the cell voltage is larger than that when it adsorbs on the internal wall. This suggests that CNTs with a large diameter and a low array density are more advantageous to enhance storage performance of CNT-based Li batteries. Compared with Li(+) ions on the (4,4) CNT internal wall, the cell voltage of Li(+) on the (10,10) CNT external wall is 0.55 V higher, which indicates an improvement of about 38%. These results will be helpful for the design of more efficient CNT-based Li batteries.

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In this study, a lignin-based polyacid catalyst was synthesized via two steps to enhance water resistance of urea–formaldehyde (UF) resins. The first steps involved a hydroxymethylation reaction to increase the hydroxyl content in lignin. Then, hydroxymethylated lignins were reacted with maleic anhydride to form maleated lignin-based polyacids. The acid groups were expected to function as acid catalysts to catalyze the curing process of UF resin. In order to elucidate the structural variation, 3-methoxy-4-hydroxyphenylpropane as a typical guaiacol lignin structural unit was used as a model compound to observe the hydroxymethylation and the reaction with maleic anhydride analyzed by 1H and 13C NMR. After the structural analysis of synthesized lignin-based polyacid by FTIR and 13C NMR, it was used to produce UF resin as an adhesive in plywood and medium density fiberboard (MDF) production, respectively. The results showed that when the addition of lignin-based polyacid was 5% in plywood, it could effectively improve the water resistance of UF resins as compared to commercial additive NH4Cl. It also exhibited a lower formaldehyde emission. Like plywood, lignin-based catalysts used in medium density fiberboard production could not only maintain the mechanical properties, but also inhibit the water adsorption of fiberboards.