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971.
Writing with Fluid: Structuring Hydrogels with Micrometer Precision by AFM in Combination with Nanofluidics 下载免费PDF全文
Nicolas Helfricht Andreas Mark Marina Behr Andreas Bernet Hans‐Werner Schmidt Georg Papastavrou 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(31)
Hydrogels have many applications in biomedical surface modification and tissue engineering. However, the structuring of hydrogels after their formation represents still a major challenge, in particular due to their softness. Here, a novel approach is presented that is based on the combination of atomic force microscopy (AFM) and nanofluidics, also referred to as FluidFM technology. Its applicability is demonstrated for supramolecular hydrogel films that are prepared from low‐molecular weight hydrogelators, such as derivates of 1,3,5‐benzene tricarboxamides (BTAs). BTA films can be dissolved selectively by ejecting alkaline solution through the aperture of a hollow AFM‐cantilever connected to a nanofluidic controller. The AFM‐based force control is essential in preventing mechanical destruction of the hydrogels. The resulting “chemical writing” process is studied in detail and the influence of various parameters, such as applied pressure and time, is validated. It is demonstrated that the achievable structuring precision is primarily limited by diffusion and the aperture dimensions. Recently, various additive techniques have been presented to pattern hydrogels. The here‐presented subtractive approach can not only be applied to structure hydrogels from the large class of reversibly formed gels with superior resolution but would also allow for the selective loading of the hydrogels with active substances or nanoparticles. 相似文献
972.
Surface Energy and Surface Stability of Ag Nanocrystals at Elevated Temperatures and Their Dominance in Sublimation‐Induced Shape Evolution 下载免费PDF全文
Long‐Bing He Lei Zhang Xiao‐Dong Tan Lu‐Ping Tang Tao Xu Yi‐Long Zhou Zhan‐Yong Ren Yun Wang Chun‐Yu Teng Li‐Tao Sun Jian‐Feng Nie 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(27)
The surface energy and surface stability of Ag nanocrystals (NCs) are under debate because the measurable values of the surface energy are very inconsistent, and the indices of the observed thermally stable surfaces are apparently in conflict. To clarify this issue, a transmission electron microscope is used to investigate these problems in situ with elaborately designed carbon‐shell‐capsulated Ag NCs. It is demonstrated that the {111} surfaces are still thermally stable at elevated temperatures, and the victory of the formation of {110} surfaces over {111} surfaces on the Ag NCs during sublimation is due to the special crystal geometry. It is found that the Ag NCs behave as quasiliquids during sublimation, and the cubic NCs represent a featured shape evolution, which is codetermined by both the wetting equilibrium at the Ag–C interface and the relaxation of the system surface energy. Small Ag NCs (≈10 nm) no longer maintain the wetting equilibrium observed in larger Ag NCs, and the crystal orientations of ultrafine Ag NCs (≈6 nm) can rotate to achieve further shape relaxation. Using sublimation kinetics, the mean surface energy of Ag NCs at 1073 K is calculated to be 1.1–1.3 J m?2. 相似文献
973.
Jin‐Xuan Fan Di‐Wei Zheng Wen‐Wen Mei Si Chen Si‐Yi Chen Si‐Xue Cheng Xian‐Zheng Zhang 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(48)
As a characteristic trait of most tumor types, metastasis is the major cause of the death of patients. In this study, a photothermal agent based on gold nanorod is coated with metal (Gd3+)‐organic (polyphenol) network to realize combination therapy for metastatic tumors. This nanotheranostic system significantly enhances antitumor therapeutic effects in vitro and in vivo with the combination of photothermal therapy (PTT) and chemotherapy, also can remarkably prevent the invasion and metastasis due to the presence of polyphenol. After the treatment, an 81% decrease in primary tumor volumes and a 58% decrease in lung metastasis are observed. In addition, the good performance in magnetic resonance imaging, computerized tomography, and photothermal imaging of the nanotheranostic system can realize image‐guided therapy. The multifunctional nanotheranostic system will find a great potential in diagnosis and treatment integration in tumor treatments, and broaden the applications of PTT treatment. 相似文献
974.
How Effective is Plasmonic Enhancement of Colloidal Quantum Dots for Color‐Conversion Light‐Emitting Devices? 下载免费PDF全文
Hyun Chul Park Isnaeni Suhyun Gong Yong‐Hoon Cho 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(48)
Enhancing the fluorescence intensity of colloidal quantum dots (QDs) in case of color‐conversion type QD light‐emitting devices (LEDs) is very significant due to the large loss of QDs and their quantum yields during fabrication processes, such as patterning and spin‐coating, and can therefore improve cost‐effectiveness. Understanding the enhancement process is crucial for the design of metallic nanostructure substrates for enhancing the fluorescence of colloidal QDs. In this work, improved color conversion of colloidal green and red QDs coupled with aluminum (Al) and silver (Ag) nanodisk (ND) arrays designed by in‐depth systematic finite‐difference time domain simulations of excitation, spontaneous emission, and quantum efficiency enhancement is reported. Calculated results of the overall photoluminescence enhancement factor in the substrate of 500 × 500 µm2 size are 2.37‐fold and 2.82‐fold for Al ND‐green QD and Ag ND‐red QD structures, respectively. Experimental results are in good agreement, showing 2.26‐fold and 2.66‐fold enhancements for Al ND and Ag ND structures. Possible uses of plasmonics in cases such as white LED and total color conversion for possible display applications are discussed. The theoretical treatments and experiments shown in this work are a proof of principle for future studies of plasmonic enhancement of various light‐emitting materials. 相似文献
975.
Qidi Wang Chenglong Zhao Yaxiang Lu Yunming Li Yuheng Zheng Yuruo Qi Xiaohui Rong Liwei Jiang Xinguo Qi Yuanjun Shao Du Pan Baohua Li Yong‐Sheng Hu Liquan Chen 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(42)
Sodium–ion batteries (NIBs), due to the advantages of low cost and relatively high safety, have attracted widespread attention all over the world, making them a promising candidate for large‐scale energy storage systems. However, the inherent lower energy density to lithium–ion batteries is the issue that should be further investigated and optimized. Toward the grid‐level energy storage applications, designing and discovering appropriate anode materials for NIBs are of great concern. Although many efforts on the improvements and innovations are achieved, several challenges still limit the current requirements of the large‐scale application, including low energy/power densities, moderate cycle performance, and the low initial Coulombic efficiency. Advanced nanostructured strategies for anode materials can significantly improve ion or electron transport kinetic performance enhancing the electrochemical properties of battery systems. Herein, this Review intends to provide a comprehensive summary on the progress of nanostructured anode materials for NIBs, where representative examples and corresponding storage mechanisms are discussed. Meanwhile, the potential directions to obtain high‐performance anode materials of NIBs are also proposed, which provide references for the further development of advanced anode materials for NIBs. 相似文献
976.
977.
978.
Designing Metallic and Insulating Nanocrystal Heterostructures to Fabricate Highly Sensitive and Solution Processed Strain Gauges for Wearable Sensors 下载免费PDF全文
Woo Seok Lee Seung‐Wook Lee Hyungmok Joh Mingi Seong Haneun Kim Min Su Kang Ki‐Hyun Cho Yun‐Mo Sung Soong Ju Oh 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(47)
All‐solution processed, high‐performance wearable strain sensors are demonstrated using heterostructure nanocrystal (NC) solids. By incorporating insulating artificial atoms of CdSe quantum dot NCs into metallic artificial atoms of Au NC thin film matrix, metal–insulator heterostructures are designed. This hybrid structure results in a shift close to the percolation threshold, modifying the charge transport mechanism and enhancing sensitivity in accordance with the site percolation theory. The number of electrical pathways is also manipulated by creating nanocracks to further increase its sensitivity, inspired from the bond percolation theory. The combination of the two strategies achieves gauge factor up to 5045, the highest sensitivity recorded among NC‐based strain gauges. These strain sensors show high reliability, durability, frequency stability, and negligible hysteresis. The fundamental charge transport behavior of these NC solids is investigated and the combined site and bond percolation theory is developed to illuminate the origin of their enhanced sensitivity. Finally, all NC‐based and solution‐processed strain gauge sensor arrays are fabricated, which effectively measure the motion of each finger joint, the pulse of heart rate, and the movement of vocal cords of human. This work provides a pathway for designing low‐cost and high‐performance electronic skin or wearable devices. 相似文献
979.
980.
Takeo Uchida Keita Abe Yuma Endo Shosei Ichiseki Satoru Akita Shiyun Liu Sho Aradachi Masataka Saito Akihiko Fukuchi Taiyo Kikkawa Theo Dammaretz Ibuki Kawamata Yuki Suzuki Shin‐ichiro M. Nomura Satoshi Murata 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(41)
A new kind of the Vernier mechanism that is able to control the size of linear assembly of DNA origami nanostructures is proposed. The mechanism is realized by mechanical design of DNA origami, which consists of a hollow cylinder and a rotatable shaft in it connected through the same scaffold. This nanostructure stacks with each other by the shape complementarity at its top and bottom surfaces of the cylinder, while the number of stacking is limited by twisting angle of the shaft. Experiments have shown that the size distribution of multimeric assembly of the origami depends on the twisting angle of the shaft; the average lengths of the multimer are decamer, hexamer, and tetramer for 0°, 10°, and 20° twist, respectively. In summary, it is possible to affect the number of polymerization by adjusting the precise shape and movability of a molecular structure. 相似文献