纳米空腔堆积的一维碳纳米结构的合成与表征

Quasi-periodically intermittent hollow-cavity-stacked one-dimensional carbon nanostructures were obtained by microwave plasma chemical vapor deposition from the mixture of CH₄ and N₂ on Fe/γ-Al₂O₃ catalyst. This structure was characterized by transmission electron microscope (TEM), high-resolution TEM and X-ray energy dispersive spectral analysis. The results indicate that the trace impurity of nitrogen might account mainly for the formation of these novel nanostructures. The structural units in these one-dimensional carbon nanostructures are full of nanocavities, which may be of potential importance in hydrogen storage.     

新颖的TiO2@C核壳结构纳米纤维阵列电极制备及其在电化学传感器中的应用

本文提出以金属钛为基底, 在丙酮蒸气和无催化剂条件下, 通过高温反应, 直接在金属钛片上一步合成出具有核壳结构的TiO2@C纳米纤维阵列. 由于TiO2@C纳米纤维阵列在金属钛片上分布均一, 与金属钛基底有良好的结合力和电接触性能, 可直接作为电化学传感器电极. 进一步的电化学检测表明, 该电极对铁氰化钾及多巴胺等物质有良好的电化学响应, 对多巴胺检测灵敏度高, 响应的线性范围为1.0×10-7~1.0×10-4 mol/L, 检测限达2.45×10-8 mol/L. 该电极有望在生物传感、环境分析及药物分析等领域发挥重要作用.     

竹节状纳米碳纤维的制备及嵌锂性能研究

以泡沫镍为催化剂,在600和700℃下,以CVD法热解乙炔气体制备大量的纳米碳纤维.随着制备温度增加,纳米碳纤维直径变小,竹节状含量减少, d002值减小,微晶片层平面Lc和La值增大,碳材料的可逆容量则下降.分别用透射电镜、 X射线衍射和拉曼光谱观察和测定了纳米碳纤维的形貌、微结构,发现在不同条件下生长的纳米碳纤维有不同的形貌和结构.对纳米碳纤维的电化学嵌锂性能的研究表明,纳米碳纤维的结构对其电化学嵌锂容量和充放电循环寿命起重要影响,制备温度越低,纳米碳纤维的石墨化程度越差,可逆嵌锂容量相应要高一些.     

金属基底上碳纳米管束的大面积制备

采用化学气相沉积法(CVD)，以二甲苯为碳源，二茂铁为催化剂，以沉积Al膜过渡层的不锈钢为基底，经过HF处理后，大面积合成了一种碳纳米管束状结构。使用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和拉曼光谱(Raman)对样品形貌和结构进行表征。结果显示：合成的碳纳米管束直径为15～25 μm，长度超过500 μm，每根管束由大量直径为30～80 nm的多壁碳纳米管组成，这些碳纳米管沿管束轴线方向密实排列并相互缠绕，预示着具有较强的机械强度。结合实验对其形成机制进行了初步探讨。     

碳包覆纳米金属颗粒的合成研究进展

碳包覆纳米金属颗粒是继富勒烯和碳纳米管之后的又一新型纳米碳材料,在许多领域具有广泛应用前景。本文综述了碳包覆纳米金属颗粒的合成方法,包括：电弧放电法、化学气相沉积法、热解法、液相浸渍炭化法和炭凝胶爆炸法等,简述了形成机理,总结了各自的优缺点,并指出将来的发展方向。     

活性炭上化学气相沉积法生长纳米碳纤维

利用流化床技术,以天然气为碳源,负载于活性炭上的纳米镍粒子为催化剂,在750 ℃下采用化学气相沉积法制备了气相生长纳米碳纤维(VGCNFs)/活性炭(AC)复合物。通过对样品进行XRD、激光拉曼光谱、扫描电镜和氮吸附检测,发现VGCNFs生长在活性炭的各个侧面上,以顶部生长模式为主,纤维的直径在40～120 nm之间,由于粗糙的纤维表面和石墨片层的翘曲而缺陷较多。VGCNFs/AC复合物与原料活性炭相比,BET比表面积从2 367 m²·g^-1降到了1 474     

减压化学气相沉积法制备规则螺旋状纳米碳管

以硅胶负载的Co纳米颗粒为催化剂,在低流量的减压体系中通过化学气相沉积法制备了规则螺旋状的纳米碳管.通过TEM和HRTEM研究了螺旋碳管的形貌、尺度分布以及管身、曲面和节点处的晶型;讨论了催化剂制备中pH值对催化剂的尺寸、规则程度和存在形态以致对螺旋碳管产量、管径厚度以及螺旋管的相对比例的影响;此外,还分析了反应压力对碳管生长的影响.     

化学气相沉积法制备氧化锡自组装纳米结构

采用化学气相沉积法在镀有5-10 nm厚金膜的SiO2衬底上, 通过控制生长条件, 实现了二氧化锡纳米结构的自组装生长, 成功制备出了莲花状和菊花状的二氧化锡自组装纳米结构. 利用扫描电子显微镜、X射线衍射等表征分析手段对样品的表面形貌、结构及成份进行表征和研究. 并在此基础上, 讨论了两种自组装纳米结构的生长机制.     

NaCl担载Fe催化裂解乙炔制备纳米碳材料

以水溶性NaCl担载Fe作催化剂,于400℃和420C下化学气相沉积法催化裂解乙炔进行了反应.通过X射线衍射仪、扫描电子显微镜和能谱分析仪对催化剂进行了表征,表征结果显示:活性组分Fe被分散成了粒径在10～40nm之间的纳米颗粒;通过扫描电子显微镜和高分辨透射电镜对产物进行了表征,表征结果显示:当裂解温度为400℃时,...     

催化剂对纳米聚团床法制备的纳米碳材料形貌的影响

 在纳米聚团床中用催化化学气相沉积法批量制备了碳纳米管，研\r\n究了过渡金属催化剂对碳纳米管形貌和产量的影响．实验结果表明，含\r\n铁催化剂的活性较低，产率较低，但产品质量较好；含镍催化剂的活性\r\n较高，产率较高，但产品质量较差；在钴催化剂作用下发现了一种新型\r\n的针状纳米碳材料．用含载体较少的铁催化剂可以得到纯度较高且微观\r\n结构较好的碳纳米管，但产率较低；不含任何载体的纯镍催化剂则不能\r\n得到碳纳米管．适宜的催化剂组成、催化剂活性点的均匀分布和裂解速\r\n度的控制等构成了纳米聚团床大批量制备碳纳米管技术的关键．     

螺旋纳米碳纤维的制备与表征

利用氢电弧等离子体法制备了纳米铜-镍合金作为催化剂,通过乙炔的催化热解制备了对称生长的螺旋纳米碳纤维.并用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和红外(IR)对其进行表征,发现在单个纳米铜-镍合金粒子上对称生长出两根螺旋纳米碳纤维,它们的旋向相反,但是具有相同的螺旋直径、螺旋长度和碳纤维直径,而且纳米铜-镍合金粒子也有各种不同的形状.此外,这两根对称生长的螺旋纳米碳纤维之间的夹角也不同,分别为60°,90°,110°和160°.IR结果表明,螺旋纳米碳纤维分子结构中既含有不饱和的CC双键,又含有饱和的-CH₂-和-CH₃-基团.然而,利用氢电弧等离子体法制备的纳米铜和纳米镍作为催化剂,催化热解乙炔,得到的产物均是直线型碳纤维.     

The Formation of Organogels and Helical Nanofibers from Simple Organic Salts

Simple organic salts based on aniline‐derived cations and D ‐tartrate anions formed organogels and helical nanofibers. The organic salt (p‐fluoroanilinium)(D ‐tartrate) was found to generate an organogel despite the absence of a hydrophobic alkyl chain, whereas (p‐iodoanilinium)(D ‐tartrate) formed helical nanofibers in braided ropelike structures through a rolling‐up process. The helicity of these nanofibers could be reversed by changing the growth solvent. The driving forces responsible for the formation of the nanofibers were determined to be 1D O?H???O^? hydrogen‐bonding interactions between D ‐tartrate anions and π stacking of anilinium cations, as well as steric hindrance between the hydrogen‐bonded chains.     

From Random Coil Polymers to Helical Structures Induced by Carbon Nanotubes and Supramolecular Interactions

A simple method is reported for the preparation of double‐helical structures through a series of achiral random and block copolymers poly(styrene‐co‐4‐vinylbenzyl triazolylmethyl methylthymine) (PS‐co‐PVBT) with various T units on the side chains through click reactions of poly(styrene‐co‐4‐vinylbenzyl azide) (PS‐co‐PVBN₃) with propargyl thymine (PT) and also the synthesis of the A‐appended pyrene derivative (A‐Py) through click chemistry. This double‐helical structure is observed from achiral random‐coil polystyrene (PS) main chains, stabilized through the combination of multiple A–T hydrogen bonds, and π–π stacking between pyrene units and single‐walled carbon nanotubes (SWCNTs).

     

Helical Graphitic Carbon Nitrides with Photocatalytic and Optical Activities

Graphitic carbon nitride can be imprinted with a twisted hexagonal rod‐like morphology by a nanocasting technique using chiral silicon dioxides as templates. The helical nanoarchitectures promote charge separation and mass transfer of carbon nitride semiconductors, enabling it to act as a more efficient photocatalyst for water splitting and CO₂ reduction than the pristine carbon nitride polymer. This is to our knowledge a unique example of chiral graphitic carbon nitride that features both left‐ and right‐handed helical nanostructures and exhibits unique optical activity to circularly polarized light at the semiconductor absorption edge as well as photoredox activity for solar‐to‐chemical conversion. Such helical nanostructured polymeric semiconductors are envisaged to hold great promise for a range of applications that rely on such semiconductor properties as well as chirality for photocatalysis, asymmetric catalysis, chiral recognition, nanotechnology, and chemical sensing.     

CVD Growth of Carbon Nanotubes and Nanofibers: Big Length and Constant Diameter

Summary: We report mass production of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) with relatively high length and aspect ratio. We synthesized carbon nanomaterials by chemical vapor deposition (CVD) of methane as the feeding gas on Fe/Mo nanoparticles that use alumina-aerogel support. Alumina-aerogel-supported Fe/Mo catalyst was prepared using sol-gel. Drying step performed using rotary evaporation and freeze-drying. CVD was performed using a quartz tube furnace. Samples were analyzed using scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Raman spectroscopy.     

Preparation of Single‐Handed Helical Carbon/Silica and Carbonaceous Nanotubes by Using 4,4′‐Biphenylene‐Bridged Polybissilsesquioxane

Single‐handed, helical, 4,4′‐biphenylene‐bridged polybissilsesquioxane nanotubes were prepared by using the self‐assemblies of a pair of chiral low‐molecular‐weight gelators as templates. Single‐handed, helical, carbon/silica nanotubes were obtained after carbonization of the self‐assemblies, and single‐handed helical carbonaceous nanotubes were then obtained by removal of silica with aqueous HF. Samples were characterized by using field‐emission SEM, TEM, X‐ray diffraction, thermogravimetric analysis, Raman spectroscopy, and circular dichroism. The polysilsesquioxane and carbonaceous structures exhibited optical activity. The walls of the carbon/silica and carbonaceous nanotubes were predominantly amorphous carbon. The surface area of the left‐handed, helical, carbonaceous nanotubes was 1439 m² g^?1, and such materials have potential applications as catalyst supports, chirality sensors, supercapacitor electrodes, and adsorbents.     

Hierarchy of Asymmetry in Chiral Supramolecular Polymers: Toward Functional,Helical Supramolecular Structures

The formation of helical structures through the supramolecular polymerization of a variety of self-assembling units is reviewed. These scaffolds are usually obtained by efficient transfer or amplification of chirality phenomena, in which the starting self-assembling molecules possess different elements of asymmetry, such as point or axial chirality. Relevant examples of helical supramolecular structures investigated under thermodynamic control are reviewed, and the helical outcome of remarkable examples of chiral entities obtained through kinetic control are also highlighted. Finally, selected examples of flexible macroscopic chirality and catalysis are described to illustrate the applicability of helical aggregates.