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以廉价的椰壳为原料制备了高比表面积的多孔碳材料,然后在密闭的反应釜中以硝酸蒸汽对多孔碳材料进行了后处理,制备了亲水性更好的多孔碳材料。采用扫描透射电子显微镜(TEM)、物理吸附、X射线粉末衍射(XRD)、拉曼光谱(Raman)和接触角测试对材料的微观形貌、孔道结构、组成和亲水性进行了表征,探究了不同温度下硝酸蒸汽对多孔碳材料的形貌、结构的影响,并采用循环伏安法、恒电流充放电法和交流阻抗法考察了多孔碳材料的超级电容性能。结果表明,经过硝酸蒸汽处理后的多孔碳材料的比表面积和孔体积均有所降低,且随着处理温度的升高,降低得更加明显,而亲水性却越来越好。电化学测试结果表明,经过100℃硝酸蒸汽处理的多孔碳材料(CSC-100)具有最佳的超级电容性能。在以6 mol·L-1 KOH为电解液的三电极体系中,当电流密度为0.5 A·g-1时CSC-100的比电容可达452.9 F·g-1,而未经硝酸蒸汽处理的多孔碳材料(CSC)的比电容仅为350.4 F·g-1。电容贡献分析表明CSC-100良好的亲水性和表面官能团不仅提高了双电层电容,也提高了赝电容。 相似文献
3.
Ti2O3 thin films have been prepared through atomic layer deposition and subjected to electrical resistivity measurements as a function of temperature. The as-prepared films were stable for up to three weeks. In Ti2O3 thin films, the insulator-metal transition is observed at ∼80 K, with nearly 3–4 orders of magnitude change in resistivity. The anomalous increase in electrical resistivity in the films is in accordance with the two-band model. However, the energy interval between the bands depending on the crystallographic c/a ratio leads to a change in electrical resistivity as a function of temperature. 相似文献
4.
Supercapacitors (SCs) with high energy density and power density are a research hotspot. Herein, we report a flexible porous carbon membrane supercapacitor prepared by electrospinning polyacrylonitrile (PAN) with γ-cyclodextrin-MOF (γ-CD-MOF) and then carbonizing at 900 °C. BET results showed that the supercapacitor retained the skeleton of γ-CD, γ-CD-MOF and the pores formed by the spun-fibers, which were 0.73, 1.09 and 23–186 nm, respectively, showing a high specific surface area of 134.7 m2/g. The hierarchically porous structures ensure rapid charge transfer and ion diffusion, resulting in the PAN/γ-CD-MOF carbon electrode with a high capacity of 283.3 F/g. Moreover, the supercapacitor had a high energy density up to 17.5 Wh/kg and power density up to 6 kW/kg. Significantly, it showed excellent cycle stability with a capacitance retention of 97.5% after 6000 cycles. This work provides a supramolecular strategy to construct a flexible porous carbon membrane, which has potential for supercapacitor applications. 相似文献
5.
Cancer is a global issue and a serious threat to human health, one approach to treatment is starvation therapy. Recently, three-dimensional (3D) bioprinted tumor tissue models have been developed; however, whether 3D bioprinted models are good for in vitro study of starvation therapy is unclear. In this study, we studied the state of cells with serum-free medium in both 3D bioprinted scaffold and 2D cell cultures and found that 3D bioprinted cancer cells (3D cells) were more tolerant to serum starvation than 2D cells in terms of cell viability, cell proliferation, and M2 macrophage polarization. Moreover, the ratio of LC3II/I, an index of autophagy, increased much more in 3D cells, and 3D cells showed more autophagosomes than 2D cells after serum starvation, which indicated that the autophagy levels were higher in 3D cells. These results suggested that 3D cells are more tolerant to serum starvation than 2D cells, and autophagy may play an important role in this process. 相似文献
6.
在合作博弈的一般模型中总是假设所有联盟都能形成。不过,在实际中由于受到一些因素的制约,有些联盟是不能形成的。基于此,Myerson提出了具有图通讯结构的合作博弈。Myerson值和Position值是超图博弈上的两个重要分配规则。2005年,Slikker给出了在图博弈上Position值的公理化刻画。但超图博弈上Position值的公理化刻画一直悬而未决。本文通过引入 “赋权平衡超边贡献公理”,并结合经典的“分支有效性”,提出了超图博弈上赋权Position值的公理化刻画。作为推论,解决了超图博弈上Position值的公理化刻画问题。 相似文献
7.
Carotenoids are an essential component of cashew and can be used in pharmaceuticals, cosmetics, natural pigment, food additives, among other applications. The present work focuses on optimizing and comparing conventional and ultrasound-assisted extraction methods. Every optimization step took place with a 1:1 (w:w) mixture of yellow and red cashew apples lyophilized and ground in a cryogenic mill. A Simplex-centroid design was applied for both methods, and the solvents acetone, methanol, ethanol, and petroleum ether were evaluated. After choosing the extractor solvent, a central composite design was applied to optimize the sample mass (59–201 mg) and extraction time (6–34 min). The optimum conditions for the extractor solvent were 38% acetone, 30% ethanol, and 32% petroleum ether for CE and a mixture of 44% acetone and 56% methanol for UAE. The best experimental conditions for UAE were a sonication time of 19 min and a sample mass of 153 mg, while the CE was 23 min and 136 mg. Comparing red and yellow cashews, red cashews showed a higher carotenoid content in both methodologies. The UAE methodology was ca. 21% faster, presented a more straightforward composition of extracting solution, showed an average yield of superior carotenoid content in all samples compared to CE. Therefore, UAE has demonstrated a simple, efficient, fast, low-cost adjustment methodology and a reliable alternative for other applications involving these bioactive compounds in the studied or similar matrix. 相似文献
8.
Dibenzyl trisulfide (DTS) is a natural compound with potential cancer-preventive properties occurring in Petiveria alliacea L., an ethnomedicinal plant native to the Americas. Previous studies revealed its inhibitory activity toward cytochrome P450 (CYP)1 enzymes, key in the activation of environmental pollutants. Accordingly, the aim of this study was to design novel DTS analogues, aimed at improving not only inhibitory activity, but also specificity toward CYP1A1. This was achieved by targeting interactions with CYP1A1 residues of identified importance. Three-dimensional structures for the novel analogues were subjected to molecular docking with several CYP isoforms, before being ranked in terms of binding affinity to CYP1A1. With three hydrogen bond donors, two hydrogen bond acceptors, a molecular mass of 361 Da, and a log P of 3.72, the most promising DTS analogue obeys Lipinski's rule of five. Following synthesis and in vitro validation of its CYP1A1-inhibitory properties, this compound may be useful in future cancer-preventive approaches. 相似文献
9.
Luminescent characteristics of Tm3+/Tb3+/Eu3+ tri-doped Na5Y9F32 single crystals for white emission with high thermal stability 下载免费PDF全文
Lizhi Fang 《中国物理 B》2022,31(12):127802-127802
By using an improved Bridgman method, 0.3 mol% Tm$^{3+}/0.6$ mol% Tb$^{3+}/y$ mol% Eu$^{3+}$ ($y = 0$, 0.4, 0.6, 0.8) doped Na$_{5}$Y$_{9}$F$_{32}$ single crystals were prepared. The x-ray diffraction, excitation spectra, emission spectra and fluorescence decay curves were used to explore the crystal structure and optical performance of the obtained samples. When excited by 362 nm light, the cool white emission was realized by Na$_{5}$Y$_{9}$F$_{32}$ single crystal triply-doped with 0.3 mol% Tm$^{3+}/0.6$ mol% Tb$^{3+}/0.8$ mol% Eu$^{3+}$, in which the Commission Internationale de l'Eclairage (CIE) chromaticity coordinate was (0.2995, 0.3298) and the correlated color temperature (CCT) was 6586 K. The integrated normalized emission intensity of the tri-doped single crystal at 448 K could keep 62% of that at 298 K. The internal quantum yield (QY) was calculated to be $\sim 15.16$% by integrating spheres. These results suggested that the single crystals tri-doped with Tm$^{3+}$, Tb$^{3+}$ and Eu$^{3+}$ ions have a promising potential application for white light-emitting diodes (w-LEDs). 相似文献
10.
V-based kagome materials AV3Sb5 (A=K, Rb, Cs) have attracted much attention due to their novel properties such as unconventional superconductivity, giant anomalous Hall effect, charge density wave (CDW) and pair density wave. Except for the 2a0×2a0 CDW (charge density wave with in-plane 2×2 superlattice modulation) in AV3Sb5, an additional 1×4 (4a0) unidirectional stripe order has been observed at the Sb surface of RbV3Sb5 and CsV3Sb5. However, the stability and electronic nature of the 4a0 stripe order remain controversial and unclear. Here, by using low-temperature scanning tunneling microscopy/spectroscopy (STM/S), we systematically study the 4a0 stripe order on the Sb-terminated surface of CsV3Sb5. We find that the 4a0 stripe order is visible in a large energy range. The STM images with positive and negative bias show contrast inversion, which is the hallmark for the Peierls-type CDW. In addition, below the critical temperature about 60 K, the 4a0 stripe order keeps unaffected against the topmost Cs atoms, point defects, step edges and magnetic field up to 8 T. Our results provide experimental evidences on the existence of unidirectional CDW in CsV3Sb5. 相似文献