Fabrication and growth mechanism of one-dimensional Heusler alloy nanostructures with different morphologies on anodic aluminum oxide template by magnetron sputtering

Heusler alloys are a kind of intermetallic compounds with highly-ordered arrangement of atoms. Many attractive functional materials have been developed in Heusler alloys. Due to the application requirements of materials in new-generation electronic devices and spintronics devices, one-dimensional nanostructured Heusler alloys with special functions are needed. In this work, it is proposed to grow one-dimensional Heusler alloy nanostructures (1D-HA-NSs) by magnetron sputtering plus anodic aluminum oxide (AAO) template. Nanowires with different shapes, amorphous-coated (AC) nanowires and nanotubes were successfully grown for several Heusler alloys. AC nanowires are the unique products of our method. Heusler alloy nanotubes are reported for the first time. The one-dimensional nanostructures grow on the surface of the AAO substrate rather than in the holes. The top of the pore wall is the nanostructure growth point, the shape of which determines the morphology of the nanostructures. A general growth mechanism model of one-dimensional nanostructures on AAO template was established and further confirmed by experimental observation.     

The Road Towards Planar Microbatteries and Micro‐Supercapacitors: From 2D to 3D Device Geometries

The rapid development and further modularization of miniaturized and self‐powered electronic systems have substantially stimulated the urgent demand for microscale electrochemical energy storage devices, e.g., microbatteries (MBs) and micro‐supercapacitors (MSCs). Recently, planar MBs and MSCs, composed of isolated thin‐film microelectrodes with extremely short ionic diffusion path and free of separator on a single substrate, have become particularly attractive because they can be directly integrated with microelectronic devices on the same side of one single substrate to act as a standalone microsized power source or complement miniaturized energy‐harvesting units. The development of and recent advances in planar MBs and MSCs from the fundamentals and design principle to the fabrication methods of 2D and 3D planar microdevices in both in‐plane and stacked geometries are highlighted. Additonally, a comprehensive analysis of the primary aspects that eventually affect the performance metrics of microscale energy storage devices, such as electrode materials, electrolyte, device architecture, and microfabrication techniques are presented. The technical challenges and prospective solutions for high‐energy‐density planar MBs and MSCs with multifunctionalities are proposed.     

Controllable fabrication of porous alumina templates for nanostructures synthesis

Porous alumina templates (AAO) has attracted significant interest due to the fact that they are readily fabricated through a simple procedure and are extremely popular templates in nanoscience studies. In this paper, the effects of different pore-widening treatments on the pore quality of the AAO templates were investigated. Results show that, through a highly controllable chemical pore-widening process at low temperature, different pore dimensions and diameters of the AAO templates can be easily achieved in a nanometer-scale way without changing the interpore distance. Combining with anodization voltage control, AAO templates with desired size distribution can be obtained, which will be extremely useful in template technology and masks for lithographic application. Also, silver nanorods/wires of different dimensions have been fabricated from above AAO templates after pore diameter adjustments. Such nanostructure materials hold high potential for electronics, optics, mechanics and sensing technology.     

Advances and perspectives on one-dimensional nanostructure electrode materials for potassium-ion batteries

Potassium-ion batteries (PIBs) have aroused considerable interest as a promising next-generation advanced large-scale energy storage system due to the abundant potassium resources and high safety. However, the K⁺ with large ionic radius brings restricted diffusion kinetics and severe volume expansion in electrode materials, resulting in inferior actual rate characteristics and rapid capacity fading. Designing electrode materials with one-dimensional (1D) nanostructure can effectively enhance various electrochemical properties due to the well-guided electron transfer pathways, short ionic diffusion channels and high specific surface areas. In this review, we summarize the recent research progress and achievements of 1D nanostructure electrode materials in PIBs, especially focusing on the development and application of cathode and anode materials. The nanostructure, synthetic methods, electrochemical performances and structure-performance correlation are discussed in detail. The advanced characterizations on the reaction mechanisms of 1D nanostructure electrode materials in PIBs are briefly summarized. Furthermore, the main future research directions of 1D nanostructure electrode materials are also predicted, hoping to accelerate their development into the practical PIBs market.     

直流电沉积法制备单晶Ag纳米棒阵列

在较低温条件下,采用直流电沉积法在AAO模板中成功制备出了大面积生长均匀的单晶Ag蚋米棒阵列.利用扫描电子显微镜(SEM),能谱仪(EDS),透射电子显微镜(TEM),选区电子衍射(SAED)和XRD等分析手段对样品进行形貌表征及成分分析.结果表明,阵列中的Ag纳米棒尺寸均匀,保持着良好的平行度,直径接近200nm,与AAO模板的孔径大小相当,且可以通过控制沉积时间来实现对Ag纳米棒长度的控制.     

Well-defined nanoarrays from an n-type organic perylene-diimide derivative for photoconductive devices

Well-defined one-dimensional (1D) perylene-diimide derivative (PDD) nanowire arrays were prepared via a simple electrophoretic deposition method by using anodic aluminum oxide (AAO) templates. The morphology of the as-deposited films was characterized by field emission scanning electron microscope and transmission electron microscopy. The highly ordered nanoarrays were free-standing after removing the AAO supports. Further studies revealed that the growth process of the nanowires in the AAO pores followed a 'bottom-up' growth model. A photoreceptor with PDD nanowire arrays as the charge generation layer was fabricated. It exhibited a better photoconductivity under light illumination when compared to that of its bulk counterpart. Our results suggested that electron-accepting PDD nanowire arrays can be used as a potential candidate for photoconduction devices, which would facilitate further exploration of new technological applications of the photoimaging process.     

图案化金属铜纳米线阵列的制备与表征

采用紫外线光刻技术与电化学沉积相结合的方法,成功制备了不同图案的铜纳米线阵列:一种是圆形图案;另一种是QDU图案.首先利用紫外线光刻技术在多孔阳极氧化铝模板(AAO)生成预设图案,以此作为"二次模板";再利用电化学方法将铜纳米线沉积到"二次模板"的开孔中.扫描电镜(SEM)测试结果表明,大面积、高规整的铜纳米线图案阵列各自独立地立在基底上, 同时,用电子能谱(EDS)分析了铜纳米线的化学成分.透射电镜(TEM)也探测到了铜纳米线的微结构.     

High‐Density Sb2Te3 Nanopillars Arrays by Templated,Bottom‐Up MOCVD Growth

Sb₂Te₃ exhibits several technologically relevant properties, such as high thermoelectric efficiency, topological insulator character, and phase change memory behavior. Improved performances are observed and novel effects are predicted for this and other chalcogenide alloys when synthetized in the form of high‐aspect‐ratio nanostructures. The ability to grow chalcogenide nanowires and nanopillars (NPs) with high crystal quality in a controlled fashion, in terms of their size and position, can boost the realization of novel thermoelectric, spintronic, and memory devices. Here, it is shown that highly dense arrays of ultrascaled Sb₂Te₃ NPs can be grown by metal organic chemical vapor deposition (MOCVD) on patterned substrates. In particular, crystalline Sb₂Te₃ NPs with a diameter of 20 nm and a height of 200 nm are obtained in Au‐functionalized, anodized aluminum oxide (AAO) templates with a pore density of ≈5 × 10¹⁰ cm^?2. Also, MOCVD growth of Sb₂Te₃ can be followed either by mechanical polishing and chemical etching to produce Sb₂Te₃ NPs arrays with planar surfaces or by chemical dissolution of the AAO templates to obtain freestanding Sb₂Te₃ NPs forests. The illustrated growth method can be further scaled to smaller pore sizes and employed for other MOCVD‐grown chalcogenide alloys and patterned substrates.     

ZnS nanostructure arrays: a developing material star

Semiconductor nanostructure arrays are of great scientific and technical interest because of the strong non-linear and electro-optic effects that occur due to carrier confinement in three dimensions. The use of such nanostructure arrays with tailored geometry, array density, and length-diameter-ratio as building blocks are expected to play a crucial role in future nanoscale devices. With the unique properties of a direct wide-bandgap semiconductor, such as the presence of polar surfaces, excellent transport properties, good thermal stability, and high electronic mobility, ZnS nanostructure arrays has been a developing material star. The research on ZnS nanostructure arrays has seen remarkable progress over the last five years due to the unique properties and important potential applications of nanostructure arrays, which are summarized here. Firstly, a survey of various methods to the synthesis of ZnS nanostructure arrays will be introduced. Next recent efforts on exploiting the unique properties and applications of ZnS nanostructure arrays are discussed. Potential future directions of this research field are also highlighted.     

ZnO纳米阵列的可控合成及其场发射特性

采用水热法在PS模板上制备了不同的ZnO纳米阵列,通过控制反应时间得到不同长径比的ZnO纳米阵列,真空场发射测试表明,使用PS模板的ZnO纳米阵列的场发射性能得到改善,主要因为长纳米棒与短纳米管交叉两层的阵列结构导致屏蔽效应减弱。较长反应时间制备的ZnO纳米棒具有较大的长径比,场发射较好。多次重复场发射测试发现,本实验制备的ZnO纳米棒阵列的场发射稳定性不是很好,还需进一步改善。     

Zinc Sulfide Nanostructure Arrays: ZnS Nanostructure Arrays: A Developing Material Star (Adv. Mater. 5/2011)

Semiconductor nanostructure arrays are of great scientific and technical interest because of the strong non‐linear and electro‐optic effects that occur due to carrier confinement in three dimensions. The use of such nanostructure arrays with tailored geometry, array density, and length‐diameter‐ratio as building blocks are expected to play a crucial role in future nanoscale devices. With the unique properties of a direct wide‐bandgap semiconductor, such as the presence of polar surfaces, excellent transport properties, good thermal stability, and high electronic mobility, ZnS nanostructure arrays has been a developing material star. The research on ZnS nanostructure arrays has seen remarkable progress over the last five years due to the unique properties and important potential applications of nanostructure arrays, which are summarized here. Firstly, a survey of various methods to the synthesis of ZnS nanostructure arrays will be introduced. Next recent efforts on exploiting the unique properties and applications of ZnS nanostructure arrays are discussed. Potential future directions of this research field are also highlighted.     

Fabrication of nanostructure and formation of nanocrystal for non-volatile memory

In this work, we have demonstrated that the nanocrystal created by combining the self-assembled block copolymer thin film with regular semiconductor processing can be applicable to non-volatile memory device with increased charge storage capacity over planar structures. Self-assembled block copolymer thin film for nanostructures with critical dimensions below photolithographic resolution limits has been used during all experiments. Nanoporous thin film from PS-b-PMMA diblock copolymer thin film with selective removal of PMMA domains was used to fabricate nanostructure and nanocrystal. We have also reported about surface morphologies and electrical properties of the nano-needle structure formed by RIE technique. The details of nanoscale pattern of the very uniform arrays using RIE are presented. We fabricated different surface structure of nanoscale using block copolymer. We also deposited Si-rich SiNx layer using ICP-CVD on the silicon surface of nanostructure. The deposited films were studied after annealing. PL studies demonstrated nanocrystal in Si-rich SiNx film on nanostructure of silicon.     

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.     

In situ growth of single-crystal TiO2 nanorod arrays on Ti substrate: Controllable synthesis and photoelectrochemical water splitting

Despite one-dimensional (1D) semiconductor nanostructure arrays attracting increasing attention due to their many advantages,highly ordered TiO2 nanorod arrays (TiO2 NR) are rarely grown in situ on Ti substrates.Herein,a feasible method to fabricate TiO2 NRs on Ti substrates by using a through-mask anodization process is reported.Self-ordered anodic aluminum oxide (AAO) overlaid on Ti substrate was used as a nanotemplate to induce the growth of TiO2 NRs.The NR length and diameter could be controlled by adjusting anodization parameters such as electrochemical anodization voltage,anodization time and temperature,and electrolyte composition.Furthermore,according to the proposed NR formation mechanism,the anodized Ti ions migrate and deposit in the AAO nanochannels to form Ti(OH)4 or amorphous TiO2 NRs under electric field,owing to the confinement effect of the template.Photoelectrochemical tests indicated that,after hydrogenation,the TiO2 NRs presented higher photocurrent density under simulated sunlight and visible light illuminations,suggesting their potential use in photoelectrochemical water splitting,photocatalysis,solar cells,and sensors.     

Synthesis and photocatalytic properties of BiOCl nanowire arrays

Bismuth oxychloride (BiOCl) nanowire arrays have been successfully prepared employing the Anodic Aluminum Oxide (AAO) template assisted sol-gel method. Nanowires of 100 nm diameter and length 2-6 μm, assembled in the porous of AAO templates, were formed. XRD and HRTEM results show that the nanowires are pure BiOCl polycrystal phase without Bi₂O₃ or BiCl₃. The photocatalytic activity of BiOCl nanowire arrays was investigated by the degradation of Rhodamine B dye solution under UV irradiation.     

Electro-codeposition synthesis and room temperature ferromagnetic anisotropy of high concentration Fe-doped ZnO nanowire arrays

Fe-doped ZnO dilute magnetic semiconductor (DMS) nanowire arrays were fabricated in anodic aluminum oxide (AAO) membranes using electro-codeposition followed by long-time anneal process. The morphology, chemical composition and crystal structure were characterized by field emission scanning electron microscope (FE-SEM), high resolution transmission electron microscope (HRTEM) equipped with an energy dispersive x-ray spectrometer, and X-ray diffraction (XRD) spectroscopy. The results prove that the Fe has been successfully doped in the lattice of ZnO nanowire arrays and the estimated Fe atomic ratio is around 22%. Micro-superconducting quantum interference device (SQUID) shows that the nanowire arrays exhibit room temperature (300 K) ferromagnetic and anisotropic ferromagnetic behavior which may be a consequence of the easy magnetization direction along the wire axes and magnetostatic interaction.     

Design of Architectures and Materials in In‐Plane Micro‐supercapacitors: Current Status and Future Challenges

The rapid development of integrated electronics and the boom in miniaturized and portable devices have increased the demand for miniaturized and on‐chip energy storage units. Currently thin‐film batteries or microsized batteries are commercially available for miniaturized devices. However, they still suffer from several limitations, such as short lifetime, low power density, and complex architecture, which limit their integration. Supercapacitors can surmount all these limitations. Particularly for micro‐supercapacitors with planar architectures, due to their unique design of the in‐plane electrode finger arrays, they possess the merits of easy fabrication and integration into on‐chip miniaturized electronics. Here, the focus is on the different strategies to design electrode finger arrays and the material engineering of in‐plane micro‐supercapacitors. It is expected that the advances in micro‐supercapacitors with in‐plane architectures will offer new opportunities for the miniaturization and integration of energy‐storage units for portable devices and on‐chip electronics.     

Emerging Porous Two-Dimensional Materials: Current Status,Existing Challenges,and Applications

Two-Dimensional (2D) materials have attracted immense attention in recent years. These materials have found their applications in various fields, such as catalysis, adsorption, energy storage, and sensing, as they exhibit excellent physical, chemical, electronic, photonic, and biological properties. Recently, researchers have focused on constructing porous structures on 2D materials. Various strategies, such as chemical etching and template-based methods, for the development of surface pores are reported, and the porous 2D materials fabricated over the years are used to develop supercapacitors and energy storage devices. Moreover, the lattice structure of the 2D materials can be modulated during the construction of porous structures to develop 2D materials that can be used in various fields such as lattice defects in 2D nanomaterials for enhancing biomedical performances. This review focuses on the recently developed chemical etching, solvent thermal synthesis, microwave combustion, and template methods that are used to fabricate porous 2D materials. The application prospects of the porous 2D materials are summarized. Finally, the key scientific challenges associated with developing porous 2D materials are presented to provide a platform for developing porous 2D materials.     

多孔阳极氧化铝膜在纳米功能材料制备中的应用

纳米材料具有一系列不同于块体材料的新异特性，在许多领域都有着广阔应用前景。阳极氧化铝膜具有独特的多孔结构，可作为制备各种纳米功能材料的模板，因而在纳米功能材料制备中占有重要地位。本文综述了多孔阳极氧化铝模板的结构特征、制作方法及由模板合成法制备的多种纳米功能材料的研究与应用现状，并介绍了模板及纳米功能材料的常用表征手段。     

Hierarchical Self-assembly of Well-Defined Louver-Like P-Doped Carbon Nitride Nanowire Arrays with Highly Effcient Hydrogen Evolution

Self-assembled nanostructure arrays integrating the advantages of the intrinsic characters of nanostructure as well as the array stability are appealing in advanced materials.However,the precise bottom-up synthesis of nanostructure arrays without templates or substrates is quite challenging because of the general occurrence of homogeneous nucleation and the difficult manipulation of noncovalent interactions.Herein,we first report the precisely manipulated synthesis of well-defined louver-like P-doped carbon nitride nanowire arrays(L-PCN)via a supramolecular self-assembly method by regulating the noncovalent interactions through hydrogen bond.With this strategy,CN nanowires align in the outer frame with the separation and spatial location achieving ultrastability and outstanding photoelectricity properties.Significantly,this self-assembly L-PCN exhibits a superior visible light-driven hydrogen evolution activity of 1872.9μmol h^−1 g^−1,rendering a^25.6-fold enhancement compared to bulk CN,and high photostability.Moreover,an apparent quantum efficiency of 6.93%is achieved for hydrogen evolution at 420±15 nm.The experimental results and first-principles calculations demonstrate that the remarkable enhancement of photocatalytic activity of L-PCN can be attributed to the synergetic effect of structural topology and dopant.These findings suggest that we are able to design particular hierarchical nanostructures with desirable performance using hydrogen-bond engineering.