Synthesis and Characterization of Chromium‐Doped Mesoporous Tungsten Oxide for Gas Sensing Applications

SBA‐15 (2D hexagonal structure) and KIT‐6 (3D cubic structure) silica materials are used as templates for the synthesis of two different crystalline mesoporous WO₃ replicas usable as NO₂ gas sensors. High‐resolution transmission electron microscopy (HRTEM) studies reveal that single‐crystal hexagonal rings set up the atomic morphology of the WO₃ KIT‐6 replica, whereas the SBA‐15 replica is composed of randomly oriented nanoparticles. A model capable of explaining the KIT‐6 replica mesostructure is described. A small amount of chromium is added to the WO₃ matrix in order to enhance sensor response. It is demonstrated that chromium does not form clusters, but well‐distributed centers. Pure WO₃ KIT‐6 replica displays a higher response rate as well as a lower response time to NO₂ gas than the SBA‐15 replica. This behavior is explained by taking into account that the KIT‐6 replica has a higher surface area as demonstrated by Brunauer–Emmett–Teller analyses and its mesostructure is fully maintained after the screen‐printing step involved in sensors preparation. The presence of chromium in the material results in a shorter response time and improved sensor response to the lowest NO₂ concentrations tested. Electrical differences related to mesostructure are reduced as a result of additive introduction.     

新型氧化铝空心球的制备及表征

以胶体碳球为模板, 廉价的硝酸铝为铝源, 成功制备出了新型的大小可控的氧化铝空心球. 通过透射电子显微镜(TEM)、扫描电子显微镜(SEM)、能量扩散X射线(EDX)、X射线粉末衍射(XRD)等手段对合成产品进行了表征, 并考察了不同合成条件对空心球形貌的影响. 实验结果表明, 合成的氧化铝空心球大小均一, 粒径及壁厚均可调节. 在该实验条件下, 硝酸铝浓度及吸附时间的改变对产品结果没有明显的影响, 而吸附温度的改变引起了产品表面光滑度及壁厚的改变.     

基于pH响应型微凝胶模板的二氧化锰空心球制备

以pH响应型微凝胶为模板制备出了二氧化锰空心球材料,并利用XRD、TGA、SEM、FT—IR和TEM等手段对其进行了表征．结果表明,通过调节KMn04的用量可以有效控制二氧化锰空心球的球壳厚度．对洗脱后上层清夜中的pH响应型微凝胶进一步研究发现,部分微凝胶呈现出非可逆的膨胀一收缩转变,这一现象主要是由于其内部的交联程度不高造成的．在对表征结果进行分析后提出了空心球结构的形成机理．     

以微凝胶模板合成P(AM-co-DMC)/SiO2杂化粒子

以聚(丙烯酰胺-co-甲基丙烯酰氧乙基三甲基氯化铵)[P(AM-co-DMC)]微凝胶为模板,TMOS为硅前驱体,中性水环境下合成了一系列P(AM-co-DMC)/SiO2有机-无机杂化粒子.对杂化粒子的大小、形态及表面形貌等进行研究,发现微凝胶对杂化粒子的形态和大小起主导作用,SiO2在模板上沉积,即使经过灼烧依然保持模板的形态;TMOS的用量对杂化粒子的性质也有重要影响——用量少时,得到的杂化粒子表面粗糙,增加用量会使表面变得光滑.杂化粒子经过灼烧后,表面会变得更加粗糙.     

模板合成H4PMo11VO40/聚苯胺纳米线列阵及其聚合机理探讨

在氧化铝模板中制备了HPA/PANI纳米线列阵,SEM、TEM表明列阵中纳米线直径约为80 nm;XRD与FT-IR证明形成了有效掺杂;单根纳米线的导电率为16.2 S.cm-1;材料的TG-DTA表明PANI纳米线材料有三步失重过程,失去吸附水过程,多酸失去结晶水和PANI结构持续分解过程,多酸结构分解过程;在氧化聚合过程中H4PMo11VO40即为质子酸又为氧化剂和掺杂剂;聚合反应采用自由基机理进行,掺杂反应发生在形成醌二亚胺式自由基正离子和双苯胺式自由基正离子和醌二亚胺式自由基正离子偶联聚合成链结构时.     

Growth of high-quality, uniform c-axis-oriented zinc oxide nano-wires on a-plane sapphire substrate with zinc oxide templates

High-quality, vertically aligned zinc oxide (ZnO) nano-wires were grown by the vapour-transport method on (1 1 2¯ 0) (a-plane) sapphire substrate covered by a uniform ZnO nano-crystalline seed layer which was deposited in a preceding growth step via simple chemical vapour deposition. A thin layer of close-packed nano-seeds with an average size of 12 nm was formed rapidly on the substrate by sublimation and thermal decomposition of zinc acetate dihydrate as the precursor at moderate temperatures and pressures. Subsequently, growth of ZnO nano-wires was performed by a carbo-thermal vapour-transport method yielding nano-wires with high reproducibility and homogeneity. The as-grown, c-axis-oriented nano-wires exhibit excellent luminescence properties and perfect alignment with respect to the substrate surface.     

Controlled synthesis of titanium nanochains using a template

Nanochains have unique properties due to their organized structures. We synthesized nanochains of titanium using crown ether as a template exploiting a simple sliding technique. The nanochains of Ti were formed with an average diameter of the sphere nodes around 80 nm separated by organic molecules with a space of 1–5 nm. The method developed here is the simplest reported to date. This process can be used for making nanostructures of different metallic materials. Trapping titanium ion particles is important to reduce the risk of the same material in the biomedical applications. The metallic nanochains are potentially applicable for making electronic and optical devices.     

Characterization of microporous aluminophosphate IST-1 using (1)H Lee-Goldburg techniques

The presence of two independent methylamine species in microporous aluminophosphate IST-1 (|(CH(3)NH(2))(4)(CH(3)NH(+)(3))(4)(OH(-))(4)|[Al(12)P(12)O(48)]) has been shown previously by synchrotron powder X-ray diffraction. One of these species, [N(1)-C(1)], links to a six-coordinated framework Al-atom [Al(1)], while the other methylamine [N(2)-C(2)] is protonated and hydrogen-bonded to three O-atoms [O(1), O(2) and O(12)]. We revisit the structure of IST-1 and report the complete assignment of the (1)H NMR spectra by combining X-ray data and high-resolution heteronuclear/homonuclear solid-state NMR techniques based on frequency-switched Lee-Goldburg homonuclear decoupling and (31)P-(31)P homonuclear recoupling. Careful analysis of the 2D (1)H-X homonuclear correlation (X=(1)H) and 2D heteronuclear correlation (X=(13)C, (31)P and (27)Al) spectra allowed the distinction of both methylamine species and the assignment of all (31)P and (13)C resonances. For the first time at a relatively high (9.4 T) magnetic field, symmetric doublet patterns have been observed in the (13)C spectra, caused by the influence of the (14)N second-order quadrupolar interaction.     

Simple fabrication of patterned gold nanoparticle arrays on functionalized block copolymer thin films

Patterned arrays of gold nanoparticles were fabricated using a simple dipping method that makes use of their specific interactions with nano-domains of carboxylic acid on a block copolymer template. Polystyrene-block-poly(tert-butyl acrylate) on the SU-8 photoresist pattern was selectively transformed to polystyrene-block-poly(acrylic acid). Au nanoparticles are selectively immobilized on the resulting carboxylic acid patterns to produce well-defined patterned Au nanoparticle arrays. This stable and robust template can be used to obtain any patterned nonaggregated metal or inorganic nanoparticle arrays.     

Morphological Control of Nanoporous Films by the Use of Functionalized Cyclodextrins as Porogens

Porous cyclic silsesquioxane (CSSQ) thin films containing nanopores (～ 2 nm) with low dielectric constant (k < 2.2), have been prepared by using various kinds of cyclodextrin (CD) derivatives as porogenic materials. The pore structure, including average pore size and interconnectivity, can be controlled by changing the functional groups of the cyclodextrin derivatives. The pore structure is found to be strongly related to the affinity of the functional groups between CD molecules. The electrical and mechanical properties of the porous thin films were monitored in order to determine the relationship between the pore structure and film properties. The mechanical properties of porous low‐k thin films (total porosity ～ 30 %) prepared with CD derivatives are found to be correlated with the pore interconnection length. The longer the deduced interconnection length in the thin film, the worse the mechanical properties (such as hardness and modulus) of the thin film, even though the porogen‐induced pore diameters are very small (～ 2 nm).