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Wang, Zhanhua; Zhang, Junhu; Xie, Jing; Li, Chuang; Li, Yunfeng; Liang, Sen; Tian, Zhicheng; Wang, Tieqiang; Zhang, Hao; Li, Haibo; Xu, Weiqing; Yang, Bai
doi: 10.1002/adfm.201001195pmid: N/A
Bioinspired organic/inorganic hybrid one‐dimensional photonic crystals (1DPCs) are prepared by alternating thin films of titania and poly(2‐hydroxyethyl methacrylate‐co‐glycidyl methacrylate) (PHEMA‐co‐PGMA) by spin‐coating, 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.
Gao, Yun; Li, Jinzhu; Liu, Luqi; Ma, Wenjun; Zhou, Weiya; Xie, Sishen; Zhang, Zhong
doi: 10.1002/adfm.201001227pmid: N/A
High mechanical performances of macroscopic‐scale fibers hierarchically constructed with carbon nanotubes (CNTs) are attracting great interest in the materials community owing to their merits of light weight and multiple functionalities. However, from the viewpoint of structural design, many fundamental issues, for example, modulus, strength, and deformation mechanisms of such CNT fibers are not yet well understood. In this Full Paper, the axial compression of hierarchical CNT fibers embedded in epoxy is investigated with the assistance of in situ Raman spectroscopy. Experimental results reveal that the conspicuous stiffening and strengthening effects of embedded CNT fibers are dominated by the constituent CNTs within the fiber, and have not yet been observed for conventional carbon fibers. Moreover, hierarchically structured CNT fibers exhibit notable flexibility without permanent deformation and failure under large‐strain compression.
Zhou, Wei; Chen, Weimeng; Nai, Jianwei; Yin, PengGang; Chen, Chinping; Guo, Lin
doi: 10.1002/adfm.201001287pmid: N/A
Peapodlike Ni/Ni3S2 chains of about 30 nm in outer diameter, with Ni cores of 10–15 nm, can be synthesized by a sacrificial template route. The Ni3S2 shell exhibits paramagnetic properties with a mass susceptibility of χ ≈ 5 × 10−5 emu (gOe)−1, while the ferromagnetic Ni cores show a superparamagnetic behavior with a blocking temperature of TB ≈ 130 K. The shape anisotropy of the chainlike structure is determined as 5.0 × 104 J·m−3, which is larger than the bulk magnetocrystalline anisotropy by one order of magnitude. The demagnetization factor is determined as ΔN = 0.29. The sample provides an ideal structure for studying the magnetization reversal property by the chain‐of‐sphere model. The observations on the formation of the peapod structure verify a growth mechanism of the nanoscale Kirkendall effect. Based on the preparation of peapod chains, a series of nickel sulfide hollow chains with average diameters of 25, 50, and 100 nm are fabricated. In addition, the phase transition for hollow chains from Ni3S2 to NiS is studied.
Wu, Changzheng; Zhu, Haiou; Dai, Jun; Yan, Wensheng; Yang, Jinlong; Tian, Yangchao; Wei, Shiqiang; Xie, Yi
doi: 10.1002/adfm.201001179pmid: N/A
Magnetic nanoring structures are attractive for spintronic devices due to their unique attributes of well‐defined and reproducible magnetic states originating from their characteristic geometry. Almost all previous magnetic nanorings have been exclusively limited to traditional ferromagnetic materials, and a magnetic semiconductor (MSC) nanoring structure has been reported rarely during the past decades. Here, it is demonstrated that room‐temperature ferromagnetic Ag1.2V3O8 nanobelts and nanorings may be achieved by controlled oxidation of the V4+ precursors in an Ag+‐containing aqueous solution. The polarization‐induced self‐coiling of in situ formed Ag1.2V3O8 nanobelts is responsible for the formation of the perfectly circular nanoring geometry. The NEXAFS spectra and the density functional calculations clearly reveal that the electron transfer originates from the hybridization of the doped Ag+ and V4+ atoms, causing ordering of the magnetic moments that give rise to the intrinsic ferromagnetism of the Ag1.2V3O8 structure.
Alia, Shaun M.; Zhang, Gang; Kisailus, David; Li, Dongsheng; Gu, Shuang; Jensen, Kurt; Yan, Yushan
doi: 10.1002/adfm.201090095pmid: N/A
Porous platinum nanotubes (PtNTs) with a all thickness of 5 nm, an outer diameter of 60 nm, and a length of 5–20 μm are synthesized by galvanic displacement with silver nanowires, which are formed by the ethylene glycol reduction of silver nitrate. Oxygen reduction reaction (ORR) and durability experiments are conducted for PtNTs, Pt nanoparticles supported on carbon (Pt/C), and bulk polycrystalline Pt (BP‐Pt) electrocatalysts to evaluate their catalytic properties for use as cathode catalysts in proton exchange membrane fuel cells. PtNTs demonstrate improved mass and specific activity for ORR and durability to Pt/C. Following durability testing, PtNTs exhibit specific ORR activity approaching that of BP‐Pt. Catalyst activity for the methanol oxidation reaction (MOR) is characterized through cyclic voltammetry and chronoamperometry techniques to evaluate the materials for use as anode catalysts in direct methanol fuel cells. The PtNTs show improved specific activity for MOR and chronoamperometry characteristics over Pt/C and BP‐Pt catalysts.
Zhang, Ming‐Xi; Cui, Ran; Tian, Zhi‐Quan; Zhang, Zhi‐Ling; Pang, Dai‐Wen
doi: 10.1002/adfm.201001185pmid: N/A
By kinetically controlling a biomimetic reduction in a quasi‐biological system (an aqueous solution containing electrolyte, peptide, and coenzyme), water‐soluble, glutathione‐capped Au clusters with a mean diameter of 1.3 nm are successfully synthesized via a new route. Opportunities that facilitate the control of the reaction are created in such a quasi‐biological system. The relatively slow rate of the biomimetic reduction, the pH‐dependent reducibility of the reducing agent, and the favorable structure of the capping molecules conspire together for the realization of a kinetics‐controlled formation of the Au clusters under mild conditions. Compared to existing methods of synthesizing gold clusters by stoichiometrically controlling the molar ratio of the Au atoms and the ligands, our current method is based on slowing down the reduction of the Au precursors in the initial stage by adjusting the activity of the reducing agent in real time, instead of using a strong reducing agent such as NaBH4. This strategy of rationally utilizing biological or biomimetic processes with unique features to provide a beneficial complement to conventional chemical syntheses could open a new way for the sustainable development of nanotechnology.
doi: 10.1002/adfm.201001216pmid: N/A
A simple and flexiable route is presented to fabricate ordered micro/nanostructured porous films, based on a monolayer colloidal crystal template and solution dipping. In2O3 is chosen as a main model material to demonstrate the validity of the given fabrication strategy. It has been shown that the porous films with different microstructures, can be constructed directly on any desired substrate (with flat, curved, or even rough surface). The separately tunable sensitivity and response time in a large range and the gas sensing performances with both high sensitivity and fast response have been obtained only by controlling microstructures of the porous films. High stability, good reproducibility, and selectivity of the sensing performance have been achieved. Further, micro/nanostructured porous film sensors with desired sensing performances are designed and fabricated. This work could be important towards practical applications of micro/nanostructured porous‐film‐based sensors in the near future.
doi: 10.1002/adfm.201001208pmid: N/A
Construction and application of surfaces with switchable liquid–solid adhesion have generated worldwide interest during the past a few years. These surfaces are of great importance not only for fundamental research but for various practical applications in smart and fluid‐controllable devices. This Feature Article reviews several techniques that have been developed to switch the adhesion on liquid/solid interfaces, including tuning the surface chemical composition, tailoring the surface morphology, and applying external stimuli. Particular attention is paid to superhydrophobic surfaces with reversible switching between low‐ and high‐adhesion to water droplets in response to external stimuli. The dynamic behavior of water droplets on such surfaces can be controlled ranging from rolling to pinning state, while maintaining superhydrophobic states. In addition, smart adhesion in oil/water/solid system and platelet/water/solid system are also discussed, which is of importants for application in designing novel anti‐bioadhesion materials.
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