Vapor-solid-solid growth of crystalline silicon nanowires using anodic aluminum oxide template

Silicon nanowires (SiNWs) were grown at low temperatures close to metal silicon eutectic point on a silicon substrate using gold catalyst coupled with assistance of the aluminum anodic oxide template. Either a vapor-solid-solid (VSS) growth process below metal silicon eutectic temperature or a vapor-liquid-solid (VLS) process at slightly higher temperatures was observed. The transmission electron microscopy coupled with both the X-ray energy dispersive spectroscopy and the selected area electron diffraction was adopted to characterize the SiNWs. Although the mechanism triggering the VSS process is still not clear, both the geometric and morphological characteristics of the SiNWs grown by the VSS process are discussed and compared with the SiNWs grown by the VLS process. The VSS SiNWs have a much slower growth rate (less than 100 nm/h), a smaller and more uniform diameter (in the range of 15.22 nm) due to a much slower rate of silicon diffusion and much smaller amount of silicon (6.8 wt.%) dissolved in the solid nanocatalyst.     

铝基氧化铝模板制备Ag纳米线及其电化学性质

采用电沉积的方法,以减薄阻挡层后的铝基多孔阳极氧化铝(AAO)为模板,制备了银纳米线。采用场发射扫描电镜(FESEM)和X射线衍射(XRD)等检测手段对产物的形貌和结构进行了表征。实验结果表明,所得的银纳米线具有面心立方结构,长度超过4μm,平均直径60nm左右。将所制备的银纳米线制成电极,电化学性能测试表明,银纳米线具有良好的可逆性和较高的比电容,当电流密度为5mA/cm2时,单电极比容量达到1110F/g。机理分析表明,一维结构的Ag纳米线对于提高电化学电容器的综合性能具有重要意义。     

Preparation of polyaniline nanotubes array based on anodic aluminum oxide template

In this article, the highly ordered polyaniline (PANI) nanotubes array was prepared by in situ polymerization using anodic aluminum oxide (AAO) as template. Polymerization of aniline was confined in the one-dimensional nanochannel of AAO template. The aniline was adsorbed and polymerized preferentially on the pore walls of template. The structure of PANI nanotubes array was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), selected area electron diffraction (SAED) and dynamic force microscope (DFM). The results show that PANI nanotubes are synthesized successfully in the nanopores of template, the diameter and length of PANI nanotubes are closed to the pore diameter and thickness of AAO template, respectively, the arrangement of PANI nanotubes is very regular and uniform, the crystal form of PANI nanotubes is hexagonal, different from pseudo-orthorhombic crystal form of PANI bulk sample, and cell parameters a and b are 0.5008 nm. The change of crystal form is due to the confinement of AAO template, which makes the molecular chain of PANI arrange more ordered.     

Synthesis of single-crystalline silver sulfide nanowires by diffusion in porous anodic aluminium oxide template

Highly ordered single-crystalline silver sulfide (Ag₂S) nanowires have been successfully achieved directly using silver nitrate and thioacetamide (TAA) as the reactants, by diffusion in the channels of anodic aluminium oxide (AAO) membrane. The products have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). The results of the research show that the as-prepared Ag₂S nanowires are monodisperse with sizes of about 50 nm in diameter, closely corresponding to the pore size of the AAO membrane. Furthermore, its photoluminescence properties and the growth mechanism are also discussed.     

恒流法制备图案化的阳极氧化铝模板

采用紫外线光刻技术在铝片上生成预设图案,用恒流二次氧化法在图案化的铝片上生长AAO,以此模板制备了PS和Cu纳米线阵列.采用扫描电子显微镜(SEM)分析.结果表明,制备的图案是直径5μm的圆形组成,圆形图案中·心之间距离是10μm,每个圆中生长了均匀的AAO,孔径大约为60～80nm.     

阳极氧化铝模板上扩散聚合法制备聚苯胺纳米管(线)阵列

以多孔阳极氧化铝（AAO）为模板，利用扩散聚合法让苯胺单体溶液和氧化剂溶液在一维纳米孔道中相互扩散，在孔内形成聚苯胺（PANI）纳米管和纳米线阵列。利用SEM、TEM、IR和XRD等检测技术对阵列进行表征。结果表明，聚合反应优先发生在孔壁上，并沿孔壁逐层生长，直至形成实心的纳米线阵列。在孔径为60nm的AAO模板内，扩散聚合40min可形成聚苯胺纳米管阵列，2h后形成聚苯胺纳米线阵列；聚苯胺纳米管（线）中同时包含结晶相和无定型相结构。用二探针法测量PANI／AAO复合阵列电阻，计算出单根聚苯胺纳米线的电导率为21．4S／cm。此外，对扩散聚合过程中聚苯胺纳米管（线）阵列的形成原因进行了初步分析和探讨。     

Characterization of conjugated polymer/anodic aluminum oxide nanocomposites fabricated via template wetting

Solution-based template wetting is demonstrated as an effective means of producing semiconductor–insulator nanocomposites. The properties of such nanocomposites formed by incorporating two commonly investigated semiconducting polymers, poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene (MEH-PPV) and poly(3-hexylthiophene-2,5-diyl) (P3HT), along with their blend, into nanoporous aluminum oxide (AAO) are investigated electronically and spectroscopically. Significant improvement in hole mobility of amorphous MEH-PPV in a nanocomposite with AAO while such improvement is absent when the crystalline P3HT is utilized to fabricate the AAO nanocomposites. Spectral evidence indicates that increased molecular order is responsible for this observation. Carrier mobility intermediate to the homopolymer nanocomposites was observed in composites fabricated from an MEH-PPV:P3HT blend and an AAO membrane. Spectral evidence indicates that these two polymers phase segregate in the composite.     

多孔阳极氧化铝模板的动力学研究及发展趋势

最近多孔阳极氧化铝膜以其有序的孔排列、可控孔径和优良的结构形态在纳米材料研究中引起了广泛的关注。尽管关于AAO膜在纳米材料制备方面的报道很多，但氧化参数如何影响膜的形态和几何结构还未被系统的论述。主要是要寻找氧化参数与膜形态间的关系从而提高AAO膜的可控性和重现性。同时总结了AAO膜的基本特点和形成机理，并对AAO模板在纳米技术领域中的现状进行分析。     

Size-dependent field-emission characteristics of ZnO nanowires grown by porous anodic aluminum oxide templates assistance

The field-emission electrical properties of hydrothermally synthesized zinc-oxide nanowires grown on SiO₂-Si substrate are reported. Vertically aligned single-crystalline emitters with distinct length L and diameter D are realized by controlling the assisted growth of porous anodic aluminum oxide (AAO) templates. Field-emission measurement revealed that these field emitters exhibited controllable turn-on field E_to and the field enhancement factor β. Sample with feature size of L = 500 nm and D = 80 nm was prepared and then used as a basis for examining the size effect. Lower E_to and higher β were observed consistently for increasing the aspect ratio L/D. The enhanced properties of E_to = 1.48 V/μm and β up to 6100 are achieved for L/D = 53 (L = 1600 nm and D = 30 nm). Optimal characterizing parameters of E_to and β will be reached while pursuing extreme L/D practically. Factors such as the geometric limit of AAO template manufacture and the filling efficiency of ZnO into AAO pores will exert influence on the size-dependent effect.     

铝阳极氧化膜纳米孔阵列的微细结构

用电化学阳极氧化法制备了纳米多孔铝阳极氧化膜(AAO模板).采用原子力显微镜(AFM)测试AAO膜,研究了纳米孔阵列的形成机制.结果表明,在AAO膜的表面,除存在六方形的纳米孔阵列外,在孔端还存在六个微小的隆起,相邻的隆起之间彼此相连,看上去酷似一朵盛开的梅花,花的中心就是六方形纳米孔.二维AFM图像显示,以往用扫描电镜表征的纳米孔阵列,实际上是一幅排列整齐、并呈周期性变化的梅花阵列图案.膜背面阻挡层的AFM二维图像表明,膜胞呈六方形,且排列高度有序.膜胞密度为4.3×109/cm2,与孔密度基本一致.阻挡层的三维照片显示,膜胞的底部存在半球状突起,也呈现出规整的阵列图案.     

阳极氧化铝作为铝电解电容器阳极箔用的研究

采用直流电阳极氧化法在高纯铝箔上制备了多孔阳极氧化铝(AAO)膜,同时采用扫描电子显微镜(SEM)、循环伏安(CV)和电化学阻杭谱(EIS)等技术对AAO膜的表面形貌、厚度和比表面电容性质等进行了表征.结果表明,AAO膜由垂直于膜表面的、孔径在60～80nm之间的平行纳米孔道组成,膜的多孔层厚度约为20μm左右;AAO...     

Manipulation of crystalline orientation and optical absorption of Cu nanowire arrays embedded in anodic aluminum oxide templates

Cu nanowires (NWs) with controlled crystalline orientation were obtained via electrodeposition inside the nanochannels of anodic aluminum oxide templates. By adjusting electrolyte composition, the orientation of Cu NWs was manipulated between [100] and [110]. [100]- and [110]-oriented single-crystal Cu NWs were also achieved under lower electrodeposition voltages in sulfate electrolyte and citrite electrolyte, respectively. Optical absorption spectrum measurements reveal that the surface plasma resonance peak of the Cu NW arrays has an obvious blue-shift of 11 nm when the orientation of Cu NWs is turned from [100] to [110].     

Silver nanoparticles deposited on anodic aluminum oxide template using magnetron sputtering for surface-enhanced Raman scattering substrate

Low-cost and highly sensitive surface-enhanced Raman scattering (SERS) substrates have been fabricated by a simple anodizing process and a magnetron sputtering deposition. The substrates, which consist of silver nanoparticles embedded on anodic aluminum oxide (AAO) templates, are investigated by a scanning electron microscope and a confocal Raman spectroscopy. The SERS activities are demonstrated by Raman scattering from adsorbed solutions of methylene blue and pyridine on the SERS substrate surface. The most optimized SERS substrate contains the silver nanoparticles, with a size distribution of 10-30 nm, deposited on the AAO template. From a calculation, the SERS enhancement factor is as high as 8.5 × 10⁷, which suggests strong potentials for direct applications in the chemical detection and analyses.     

浸蚀多孔铝模板制备TiO2亲水薄膜材料

利用浸蚀多孔铝模板,涂覆TiO2溶胶和纳米粉组成的料浆,制得TiO2亲水性阵列薄膜。通过对此薄膜SEM及表面接触角分析,研究了聚乙二醇改性、存放时间、SiO2的添加等对其亲水性的影响。结果表明:浸蚀多孔铝模板制备的TiO2薄膜无需紫外光激发即表现出良好的亲水性,5s内可达到完全铺展;料浆中添加0.02～0.04g/mL聚乙二醇能一定程度上提高薄膜材料亲水性并减缓其亲水性的降低;添加纳米SiO2制备的TiO2/SiO2复合薄膜亲水性优于纯TiO2薄膜,经聚乙二醇改性后为超亲水性,超亲水性能在黑暗中维持5天。     

Indium oxide nanorods and nanowires on porous anodic alumina

We report indium oxide nanorods and nanowires with controllable microstructure deposited on porous anodic alumina membranes (PAAs). At the beginning of the deposition, indium oxide tends to nucleate on the top of PAAs, not at the bottom of PAAs' nanopores, and grows into nanorods. It is interesting that the indium oxide nanorods on the top of PAA just copy the topography of PAA, and form a new porous layer with the thickness of 40-50 nm. As the deposition goes on, the nanorods cannot maintain the ordered nanopore structure, and evolve into nanowire net. And the nanowires can stand upwards separately, and then fall down as the length goes up, forming an indium oxide entangled nanowires. The structure evolvement is discussed according to the field emission scanning electric microscope images.     

Infrared reflection-absorption spectra of anodic oxide films on aluminum

Infrared reflection spectra of anodic aluminum oxide films prepared in boric acid and natural oxide films on aluminum show a common absorption band in the 900–1000 cm^-1 range. This band is shown to be due to the longitudinal mode of the Al-O stretching vibration. In transmission spectra this absorption band is absent; instead one observes the corresponding transverse mode centered around 650 cm^-1.