非晶Co及CoP纳米阵列的制备及研究

采用交流电化学沉积法,在多孔阳极氧化铝(AAO)模板孔洞中成功制备出直径50nm的Co纳米线阵列.采用透射电子显微镜(TEM)和选区电子衍射(SAED)观察了样品的微观形貌结构.结果显示,阵列中纳米线均匀有序,形状各向异性较大,其晶体结构为非晶.在沉积Co纳米线阵列的电解液中添加一定的还原剂(NaH2PO2·H2O),制备出非晶CoP纳米阵列,由TEM观察可知,阵列形貌发生变化,沉积产物为离散的纳米粒子而非纳米线.探讨了交流电沉积纳米阵列的生长机理.     

简单蚀刻法制备具有可控高度的金属纳米线阵列

采用多孔阳极氧化铝(AAO)作为模板,运用电化学沉积法在模板的微孔中组装金属Ni纳米线,然后用磷铬酸蚀刻表层AAO模板,暴露出规整有序、具有可控长度的Ni纳米线阵列.分别用SEM、TEM与SAED对Ni纳米线阵列进行了表征.研究了蚀刻时间与AAO模板质量的减少及暴露出来的Ni纳米线阵列长度之间的关系.结果表明,磷铬酸是较NaOH溶液更为温和有效的AAO模板蚀刻剂,通过控制模板溶解时间,可以实现对裸露于AAO模板外纳米线长度的精细有效控制.该蚀刻方法普遍适用于以AAO为模板所制得的准一维纳米阵列结构.     

多孔氧化铝模板制备有序纳米阵列及复合体系的特殊性能

由多孔阳极氧化铝模板制备有序纳米阵列因量子化具有各种特殊性能,准一维的电子输运环境使其磁阻随磁场变化有极值出现,表面缺陷的增加使其光致发光增强,纳米线阵列对各个方向透过光的损耗不通而具有偏振性,磁性能方面具有强烈的各向异性等.简要介绍了纳米阵列复合有序多孔氧化铝的性质,并展望了多孔氧化铝制备纳米晶的应用前景.     

大规模制备Ni纳米线阵列及其磁学特性研究

在多孔氧化铝模板的纳米孔洞中,利用直流电化学沉积的方法成功地制备了高度有序的磁性金属Ni纳米线阵列.利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射仪(XRD)和物理性质测量系统(PPMS)对样品的形貌、晶体结构和磁学性能进行了表征测试.SEM和TEM观察结果显示,Ni纳米线均匀地生长在氧化铝模板的孔洞中,直径约为300nm,其表面非常光滑.XRD结果显示,生长的Ni纳米线为fcc结构.磁测量结果表明,与体材料相比,Ni纳米线展现出增强的矫顽力和剩磁比,并且表现出较强的磁各向异性,其居里温度约为627K,与块体Ni的居里温度相当,说明在较高温度下,纳米线仍可呈现铁磁特性.     

金属有序纳米孔道阵列模板合成法

评述了采用母板复型法合成金属有序纳米孔道阵列模板合成方法、金属模板的特点及应用的研究进展.用于合成金属模板的母板有:多孔阳极氧化铝、径迹刻蚀高分子聚合物、具有纳米孔道的玻璃及氧化锌晶体阵列等,金属模板的金属沉积方法有化学镀、电镀、物理气相沉积法等.由于金属模板具有金属特性,在纳米阵列材料组装、电极制备及过滤膜制备领域具有重要应用前景,研究直接制备金属模板的方法是一个很有发展前途的方向.     

CdS纳米线阵列光致发光的研究

用直流电沉积法在多孔氧化铝模板中制备了高度有序的CdS纳米线阵列,SEM和XRD的观察和测量表明,CdS纳米线尺寸均匀、排列规整,具有六方纤锌矿结构,Cd和S的化学计量比为11.CdS纳米线阵列的光致发光测量显示,激发波长为325nm时,CdS纳米线阵列在450nm处有一强的PL峰,在484nm处还有一肩峰.对其光致发光机理进行了分析.     

合成和表征NiFe2O4纳米线阵列

采用真空灌注结合溶胶-凝胶和氧化铝模板法,在多孔氧化铝模板中制备了平均直径为50 nm的NiFe2O4纳米线阵列.X射线衍射结果显示所制备的纳米线是纯相的NiFe2O4纳米线,透射电镜和电子衍射的结果显示已制备的纳米线是多晶的且表面光滑,场发射扫描电镜图片显示纳米线是大面积且平行有序的、纳米线的长度和所用的氧化铝模板的厚度相当.磁测量的结果显示此纳米线阵列有形状各向异性,同块状材料相比矫顽力有所增强.对纳米线的生长机理做了简单的讨论.     

多孔氧化铝模板合成有序纳米结构材料的研究进展

模板法制备纳米结构是20世纪90年代中期发展起来的一种靠自组装构筑纳米结构的新工艺,在有序纳米结构的合成中有着广泛的应用.从多孔氧化铝模板独特的纳米孔结构出发,讨论了近年来该模板在纳米点、纳米线、纳米管、纳米异质节等纳米结构合成中的具体方法及应用,并展望了其发展前景.     

电化学组装一维纳米线阵列p型Bi2Te3温差电材料

：对p型Bi2Te3温差电材料的电沉积过程进行了研究，分析了添加剂对电沉积过程的影响．在此基础上，以孔径为50nm的阳极氧化铝多孔膜为模板，采用直流电沉积技术，在氧化铝多孔模板的纳米级微孔内电化学组装出了P型Bi2Te3纳米线阵列温差电材料，性能研究表明，p型Bi2Te3纳米线阵列的温差电性能远远超过具有相同组成的块状温差电材料。     

氧化铝模板制备ZnO纳米有序阵列及其光致发光性能研究

介绍了在多孔氧化铝模板(AAM)中沉积Zn阵列后将其加热氧化,得到单晶六角纤锌矿结构的ZnO／AAM纳米线有序阵列体系。研究了不同的氧化温度对Zn向ZnO转化和ZnO纳米阵列光致发光性能的影响。     

Room-temperature synthesis of high-density CuS nanowire arrays by a simple paired cell

High-density CuS nanoparticle nanowire (NPNW) arrays were successfully synthesized at room temperature by a simple paired cell method. The as-prepared nanowire arrays were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). The results indicate that the nanowire diameter is dependent on the pore size of the used ordered porous anodic alumina (OPAA) template and larger than the corresponding pore diameter of the template due to the corrosion effect of Na2S solution on the template. The nanowire is composed of CuS nanoparticles with hexagonal structure. When the reaction time is long enough, the nanowire is solid and composed of nearly spherical CuS nanoparticles. When the reaction time is short, only middle part of the nanowire is solid and composed of nearly spherical CuS nanoparticles, however, the tops are hollow and mainly composed of flake-like nanoparticles. The formation mechanism of CuS nanoparticle nanowires was proposed to be a heterogeneous nucleation, coalescence, aggregation and filling process.     

Synthesis of dense, single-crystalline CrO2 nanowire arrays using AAO template-assisted chemical vapor deposition

High-density, vertically aligned CrO(2) nanowire arrays were obtained via atmospheric-pressure CVD assisted by AAO templates. The CrO(2) nanowire arrays show remarkably enhanced coercivity compared with CrO(2) films or bulk. It was found that the length of the nanowires is greatly influenced by the pore diameter of the AAO template used. The growth mechanism and the pore size dependence of the CrO(2) nanowire arrays are discussed. The present method provides a useful approach for the synthesis of CrO(2) nanowire arrays. Such highly ordered nanowire arrays within an AAO template may have important applications in ultrahigh-density perpendicular magnetic recording devices and the mass production of spintronic nanodevices.     

Large-scale, reliable and robust SERS-active nanowire substrates prepared using porous alumina templates

nanowire arrays for surface-enhanced Raman scattering applications. These nanowire films were synthesized via electrodeposition using porous alumina templates of varying order, thickness and pore diameters. Mechanical polishing has been shown to be a very effective method to prepare nanowire arrays with monodisperse length over comprehensively large dimensions. On the other hand, a convenient synthesis route has been suggested that allows the formation of nanoparticle rrays using very thin and/or large area porous alumina films. It is reckoned that even films with the smallest obtainable pore sizes can be utilized to prepare large area, fine nanoparticle arrays. Such arrays may also find use in other areas, such as solar cells and electrochemistry. Preliminary Raman experiments indicated that the nanowire/nanoparticle arrays are indeed surface-enhanced Raman scattering-active. Finally, the potentials offered by the reported processing methods for fabricating substrates with predictable and high Raman amplifications are discussed.     

Characterization of ordered Cu2O nanowire arrays prepared by heat treated Cu/PAM composite

Cu nanowire arrays were synthesized via a porous alumina membrane (PAM) template with a high aspect ratio, uniform pore size (120–140 nm), and ordered pore arrangement. The Cu₂O nanowire arrays were prepared from the oxidization of Cu metal nanowire arrays. The electrochemical deposition potential of Cu metal nanowires (?180 mV vs. SCE) was determined from X-ray diffraction (XRD) patterns. The microstructure and chemical composition of Cu nanowire arrays were characterized using field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), and X-ray diffraction (XRD). Results indicate that the Cu/Cu₂O nanowire arrays assembled into the nanochannel of the porous alumina template with diameters of 120–140 nm. The valence of copper was controlled by the porous alumina template during the annealing process. Copper nanowires transformed to the Cu₂O phase with the space limitation of the PAM template. Single-crystal Cu₂O nanowire arrays were also obtained under the template embedded.     

Electrodeposition and magnetic properties of ternary Fe-Co-Ni alloy nanowire arrays with high squareness ratio

Highly-ordered ternary Fe-Co-Ni alloy nanowire arrays with diameters of about 50 nm have been fabricated by alternating current (AC) electrodeposition into the nanochannels of porous anodic aluminum oxide templates. SEM and TEM results indicate that the alloy nanowires are highly ordered. XRD and HRTEM results show that the ternary FeCoNi alloy nanowires are polycrystalline, with HCP-FCC dual phase structure. Magnetic measurements demonstrate that the ternary alloy nanowire arrays have an obvious magnetic anisotropy with an easy magnetization direction being parallel to the nanowire arrays. Along the easy magnetization direction, the coercivity (H _c ) and squareness ratio (S) increase as the annealing temperature increases, and reach a maximum level (H _c = 1337 Oe, S = 0.96) at 300 °C.     

Study on the structures and magnetic properties of Ni, Co-Al2O3 electrodeposited nanowire arrays

We report on the direct electrodeposition of nickel and cobalt nanowire arrays within the nanopores of ordered porous alumina films prepared by a two-step anodization. SEM and TEM images reveal that the pore arrays are regularly arranged throughout the alumina film. X-ray diffraction and TEM analysis show that the nickel and cobalt nanowires are single crystalline with highly preferential orientation. The aspect ratio of nanowires is over 300. M-H hysteresis loops determined by VSM indicate that the nanowire arrays obtained possess obvious magnetic anisotropy. Because of proper square ratio and coercivity the nanowire arrays of nickel seem to be more suitable candidates for perpendicular magnetic recording medium than those of cobalt.     

Ordered ZnO/AZO/PAM nanowire arrays prepared by seed-layer-assisted electrochemical deposition

An Al-doped ZnO (AZO) seed layer is prepared on the back side of a porous alumina membrane (PAM) substrate by spin coating followed by annealing in a vacuum at 400 °C. Zinc oxide in ordered arrays mediated by a high aspect ratio and an ordered pore array of AZO/PAM is synthesized. The ZnO nanowire array is prepared via a 3-electrode electrochemical deposition process using ZnSO₄ and H₂O₂ solutions at a potential of − 1 V (versus saturated calomel electrode) and temperatures of 65 and 80 °C. The microstructure and chemical composition of the AZO seed layer and ZnO/AZO/PAM nanowire arrays are characterized by field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), and energy-dispersive X-ray spectroscopy (EDS). Results indicate that the ZnO/AZO/PAM nanowire arrays were assembled in the nanochannel of the porous alumina template with diameters of 110–140 nm. The crystallinity of the ZnO nanowires depends on the AZO seed layer during the annealing process. The nucleation and growth process of ZnO/AZO/PAM nanowires are interpreted by the seed-layer-assisted growth mechanism.     

Template-based fabrication of nanowire-nanotube hybrid arrays

The fabrication and structure characterization of ordered nanowire-nanotube hybrid arrays embedded in porous anodic aluminum oxide (AAO) membranes are reported. Arrays of TiO(2) nanotubes were first deposited into the pores of AAO membranes by a sol-gel technique. Co?nanowires were then electrochemically deposited into the TiO(2) nanotubes to form the nanowire-nanotube hybrid arrays. Scanning electron microscopy and transmission electron microscopy measurements showed a high nanowire filling factor and a clean interface between the Co nanowire and the TiO(2) nanotube. Application of these hybrids to the fabrication of ordered nanowire arrays with highly controllable geometric parameters is discussed.     

Fabrication of Two Types of Ordered InP Nanowire Arrays on a Single Anodic Aluminum Oxide Template and Its Application in Solar Cells

Two types of ordered InP nanowire arrays have been prepared on the same anodic aluminum oxide template by a template-assisted metallo-organic chemical vapor deposition technique.When using template with an appropriate pore size,free-standing wires on the template surface and highly ordered wires in the nanochannels of the same template can be simultaneously achieved.The highly ordered InP nanowire arrays in the nanochannels serve as an n-type semiconductor to assemble the p-n heterojunction solar cell with p-type Cu_2O.Such a Cu_2O/lnP p-n heterojunction solar cell possesses a power conversion efficiency of 1.55%.     

Conformal anodic oxidation of aluminum thin films

Membrane-based synthesis, also called template synthesis, is a very general approach used to prepare arrays of nanomaterials with monodispersed geometrical features. The most commonly used porous templates are track-etched polycarbonate and porous anodic alumina membranes. Common to all these templates is the fact that the pores are perpendicular to the surface of the membrane. Here, a novel approach is presented, where the pores are synthesized parallel to the surface of the membrane. For the first time, the anodic oxidation of an aluminum thin film is performed laterally, i.e., parallel to the surface of the substrate, instead of perpendicular as usually done. For low anodic oxidation voltages (between 3 and 5 V) we obtain highly regular and ordered pore arrays, at least over a few hundred nanometers length, with a minimum pore size of approximately 3 to 4 nm. With such porous alumina structures, the controlled in-plane organization of arrays of template-grown nanowires and carbon nanotubes for reproducible device fabrication should be much easier.