近场拉曼光谱在纳米结构表征中的应用

近场拉曼光谱是近场光学领域中的新型技术,因其可对纳米结构进行光谱表征而备受科学研究者的关注。文章从光学的角度简述了将近场光学与拉曼光谱相结合成为近场拉曼光谱的原理,介绍了近场拉曼光谱技术的优势,详细阐述了近场拉曼光谱在单壁碳纳米管、生物样品、热电晶体、染料分子等纳米结构表征中的应用,展现了近场拉曼光谱技术广阔的应用前景。

Ni-Cr-Al纳米复合镀层的制备及结构表征

采用复合电沉积技术,通过向Ni电镀液中加入一定量的Cr和Al纳米粒子制备了一种新型Ni-Cr-Al纳米复合镀层,作为比较,同时制备了Cr和Al微米粒子复合的镀层。研究了镀层中粒子尺寸对复合量的影响和镀层的微观结构。在相同的工艺参数下,纳米粒子由于在阴极的吸附少,因此较微米粒子难沉积。结构分析表明,该镀层具有纳米结构,即纳米Cr、Al粒子均匀分布于纳米Ni基体中。

高活性碳纳米管阴极组合件的研制(英文)

应用两亲软化学法,将纳米铂有效地分散在多层碳纳米管阵列(ACNT)表面,使其得以修饰,形成了高活性的阴极催化材料,用于制备结构膜阴极组合件(MEA)。对MEA进行的形态学和电化学测试,证明可以大大改善质子交换膜燃料电池(PEMFC)的纳米结构和电化学性能。该种阴极催化材料除了表面均匀及高活性之外,还表现出比目前设计出的PEMFC高出约6倍的输出功率,在一定电位下的氧气中可以达到900 mW·cm-2,而贵金属铂搭载量则显著降低至0.14～0.19 mg·cm-2。实验结果表明,由于碳纳米管阵列的厌水性保证了电极性能的稳定性,从而为提高PEMFC电池的长期稳定性及降低成本提供了一条新的解决思路,具有一定的学术研究价值和经济应用价值。

Synthesis and Characterization of ZnO Bicrystalline Nanosheets Grown via Ag-Au Alloy Catalyst

ZnO bicrystalline nanosheets have been synthesized by using Ax=AU1-x alloy catalyst via the vapor transport and condensation method at 650 ℃. High resolution transmission electron microscopy characterization reveals a twin boundary with {01-13} plane existing in the bicrystalline. A series of control experiments show that both AgxAu1-x alloy catalyst and high supersaturation of Zn vapor are prerequisites for the formation of ZnO bicrystalline nanosheet. Moreover, it is found that the density of ZnO bicrytalline nanosheets can be tuned through varying the ratio of Ag to Au in the alloy catalyst. The result demonstrates that new complicated nanostructures can be produced controllably with appropriate alloy catalyst.

Direct identification of the carbonate intermediate during water-gas shift reaction at Pt-NiO interfaces using surface-enhanced Raman spectroscopy

Noble metal-reducible oxide interfaces have been regarded as one of the most active sites for water-gas shift reaction.However,the molecular reaction mechanism of water-gas shift reaction at these interfaces still remains unclear.Herein,water-gas shift reaction at Pt-NiO interfaces has been in-situ explored using surface-enhanced Raman spectroscopy by construction of Au@Pt@NiO nanostructures.Direct Raman spectroscopic evidence demonstrates that water-gas shift reaction at Pt-NiO interfaces proceeds via an associative mechanism with the carbonate species as a key intermediate.The carbonate species is generated through the reaction of adsorbed CO with gaseous water,and its decomposition is a slow step in water-gas shift reaction.Moreover,the Pt-NiO interfaces would promote the formation of this carbonate intermediate,thus leading to a higher activity compared with pure Pt.This spectral information deepens the fundamental understanding of the reaction mechanism of water-gas shift reaction,which would promote the design of more efficient catalysts.

Synthesis and Characterization of MgSb2O6 Trirutile-Type in Low Presence Concentrations of Ethylenediamine

The nanoparticles MgSb206 with trirutile-type structure were prepared by colloidal method using ethylanediamine （0.5 and 0.75 mL）, following a calcination at 800 ℃. After, those powders were analyzed by x-ray obtaining a tetragonal structure with cell parameters, a = 4.64 A and c = 9.25 A and special group P42/mnm. Using a scanning electron microscopy were analyzed the powders calcined at 800 ℃, showing the formation of micro-plates, micro-rods, nanoparticles and morphology as rice grains. Employing a transmission electron microscopy, were found nanostructures hexagonal shaped with sizes of- 33.6 nm （0.5 mL） and 28.6 nm （0.75 mL）.

Nanomagnetic CoPt truncated octahedrons:facile synthesis,superior electrocatalytic activity and stability for methanol oxidation

Nanomagnetic CoPt truncated octahedral nanoparticles （TONPs） were successfully synthesised through a facile one-pot strategy. These single crystal CoPt TONPs with an average size of about 8 nm exhibit excellent electrocatalytic performance of both activity and stability for methanol oxidation reaction （MOR）. The mass and specific activities of CoPt TONPs is 8 and 6 times higher than that of standard commercial Pt/C, respectively. After accelerated durability test （ADT）, the loss of electrochemical surface area （ECSA） for CoPt TONPs is only 18.5%, which is significantly less than that of commercial Pt/C （68.2%）, indicating that CoPt TONPs possess much better stability than commercial Pt/C in the prolonged operation. The Curie temperature of CoPt TONPs down to 8 nm is as high as 350 K with weak ferromagntism at room temperature （RT）, which is greatly valuable for recycling in the eletrocatalytic applications.

Synthesis and TEM structural characterization of C60-flattened carbon nanotube nanopeapods

A fully flattened carbon nanotube （FNT）, a graphene nanoribbon （GNR） analogue, provides a hollow space at edges for endohedral doping. Due to the unique shape of the hollow space of FNTs, novel types of low-dimensional arrangements of atoms and molecules can be obtained through endohedral doping into FNTs, which provides a new type of nanopeapods. FNT-based nanopeapods have been synthesized through endohedral doping of C60, and their structural characterization with transmission electron microscopy （TEM） performed. The doping of C60 into the inner hollow space of FNTs has been carried out via the gas-phase filling method, where open-ended FNTs are sealed in a glass ampoule and heated at 723-773 K for two days. TEM observations show that most of the encapsulated C60 molecules align as single molecular chains along the edges of FNTs and that some of the C60 forms two-dimensional close-packed structures inside FNTs.

Structure characterization,magnetic and photoluminescence properties of Mn doped ZnS nanocrystalline

Wurzite ZnS:Mn nanorods are synthesized via a solvothermal method by using ethylenediamine and water as mixed solvent.The diameters of the nanorods increase and the lengths decrease with the Mn concentration.High resolution transmission electron microscopic images illustrate that a few cubic ZnS:Mn nanoparticles arise along with hexagonal nanorods on high Mn concentration.The samples set off yellow-orange emission at 590 nm,characteristic of 4 T→ 6 A 1 transition of Mn 2+ at T d symmetry in ZnS.Electron spin resonance spectrum of the nanorods shows that high Mn concentrations produce a broad envelope,whereas six-line hyperfine appears for lower Mn concentrations.These results together with the magnetization curves indicate that all the ZnS:Mn samples are paramagnetic even down to 4 K,which suggests that the ZnS:Mn is not suitable for dilute magnetic semiconductor.

Occurrence, Structure and Mineral Phases of Nanoparticles in an Anthrosol

Soils contain various kinds of crystalline to amorphous solid particles with at least one dimension in the nanoscale （〈 100 nm）. These nanoparticles contribute greatly to dynamic soil processes such as soil genesis, trace element cycling, contaminant transport, and chemical reaction. The nano-sized fraction of an Anthrosol was obtained to determine the occurrence, chemical composition, structure, and mineral phases of nanoparticles using high-resolution transmission electron microscopy （HRTEM） equipped with an energy-dispersive X-ray spectroscopy. Selected area electron diffraction or the fast Fourier transform of high-resolution images was used in structural characterization of the nanoparticles with HRTEM. Two nanoscale mineral types, i.e., mineral nanoparticles and nanomi- nerals, were observed in the Anthrosol. Mineral nanoparticles in soil included well crystalline aluminumsilicate nanosheets, nanorods, and nanoparticles. Nanosheets with a length of 120-150 nm and a width of about 10-20 nm were identified as chlorite/vermiculite series. The presence of clear lattice fringe spacing in HRTEM image of nanoparticles indicated that mineral nanoparticles had a relatively good crystallinity. The nanomineral ferrihydrite also existed in the Anthrosol. The HRTEM images and the particle size distribution histogram suggested that these ferrihydrite nanoparticles were quite homogeneous, and had a narrow size distribution range （1-7 nm） with a mean diameter of 3.6 4- 1.6 nm. Our HRTEM observation indicated that mineral nanoparticles and nanominerals were common and widely distributed in Anthrosols. HRTEM and selected area diffraction or lattice fringe spacing characterization provided further proofs to the structure of nanoparticles formed in soil.