Electric field-assisted deposition of nanowires on carbon nanotubes for nanoelectronics and sensor applications

Manipulation and control of matter at the nanoscale and atomic scale levels are crucial for the success of nanoscale sensors and actuators. The ability to control and synthesize multilayer structures using carbon nanotubes that will enable the building of electronic devices within a nanotube is still in its infancy. In this paper, we present results on selective electric field-assisted deposition of metals on carbon nanotubes realizing metallic nanowire structures. Silver and platinum nanowires have been fabricated using this approach for their applications in chemical sensing as catalytic materials to sniff toxic agents and in the area of biomedical nanotechnology for construction of artificial muscles. Electric field-assisted deposition allows the deposition of metals with a high degree of selectivity on carbon nanotubes by manipulating the charges on the surface of the nanotubes and forming electrostatic double-layer supercapacitors. Deposition of metals primarily occurred due to electrochemical reduction, electrophoresis, and electro-osmosis inside the walls of the nanotube. SEM and TEM investigations revealed silver and platinum nanowires between 10 nm and 100 nm in diameter. The present technique is versatile and enables the fabrication of a host of different types of metallic and semiconducting nanowires using carbon nanotube templates for nanoelectronics and a myriad of sensor applications.     

GaN nanowires: CVD synthesis and properties

The growth of GaN nanowires from Ga and NH₃ sources in the flow of Ar carrier gas using a chemical vapor deposition (CVD) system was systematically studied. The substrates used were Si(111) and Si(100). Fabricated nanowires were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). We investigated the influence of growth temperature, catalyst used, Ga amount, and the ratio of Ar and NH₃ flow rates on the morphology and properties of GaN nanowires. We found that the best results were obtained for a growth temperature of 950 °C. Optimal catalysts were Au and metallic Ni, while the use of nickel nitrate was found to lead to formation of SiO_x nanowire bunches in addition to GaN nanowires. For the optimal temperature and catalyst used, the influence of the Ga to N ratio on the nanowire growth was studied. It was found that different types of nanostructures are observed in relatively Ga-rich and in relatively N-rich conditions. Growth mechanisms of different types of nanowires, including the stacked-cone nanowires and the microscale structures formed by lateral growth under N-rich conditions, are discussed.     

Biotemplated silica and titania nanowires: synthesis, characterization and potential applications

A simple biotemplating method for the synthesis of silica (SiO2) and titania (TiO2) nanowires was designed on a fibrillar protein (alpha-synuclein) template. The diameter of SiO2 and TiO2 nanowires could be varied, between 20-100 nm, by varying the processing conditions. The nanowires were characterized by energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS). Due to their high surface area and porosity, the nanowires were tested for potential applications in enzymatic biosensor design.     

碳量子点的合成、性质及其应用

碳量子点(CQDs,C-dots or CDs)是一种新型的碳纳米材料,尺寸在10nm以下,具有良好的水溶性、化学惰性、低毒性、易于功能化和抗光漂白性、光稳定性等优异性能,是碳纳米家族中的一颗闪亮的明星。自从2006年[1]报道了碳量子点(CQDs)明亮多彩的发光现象后,世界各地的研究小组开始对CQDs进行了深入的研究。最近几年的研究报道了各种方法制备的CQDs在生物医学、光催化、光电子、传感等领域中都有重要的应用价值。这篇综述主要总结了关于CQDs的最近的发展,介绍了CQDs的合成方法、表面修饰、掺杂、发光机理、光电性质以及在生物医学、光催化、光电子、传感等领域的应用。     

Ab initio vibrational and thermal properties of AlN nanowires under axial stress

The vibrational and thermal properties of small diameter AlN nanowires are investigated using first principles calculations. Upon applying external pressure, the nanowires suffer a stress induced phase transition from a würtzite (WZ) to a graphite-like (GL) phase. The thermal conductance displays a nearly identical behavior for all systems in the temperature regime governed by acoustical modes, while at higher temperatures the conductance is systematically enhanced for nanowires in the GL phase. The heat capacity points out the different phonon group velocities for the acoustical modes in the two structural configurations. Our DFT-based calculations are consistent with experimental data for bulk AlN, in terms of phonon spectrum and temperature dependent heat capacity in the large nanowire limit.     

Graphene-based materials: synthesis, characterization, properties, and applications

Graphene, a two-dimensional, single-layer sheet of sp(2) hybridized carbon atoms, has attracted tremendous attention and research interest, owing to its exceptional physical properties, such as high electronic conductivity, good thermal stability, and excellent mechanical strength. Other forms of graphene-related materials, including graphene oxide, reduced graphene oxide, and exfoliated graphite, have been reliably produced in large scale. The promising properties together with the ease of processibility and functionalization make graphene-based materials ideal candidates for incorporation into a variety of functional materials. Importantly, graphene and its derivatives have been explored in a wide range of applications, such as electronic and photonic devices, clean energy, and sensors. In this review, after a general introduction to graphene and its derivatives, the synthesis, characterization, properties, and applications of graphene-based materials are discussed.     

Interconnect and contact for nanoelectronics: Metallic TaSi2 nanowires

TaSi₂ nanowires have been synthesized on Si substrate by annealing FeSi₂ thin film and NiSi₂ films at 950 °C in an ambient containing Ta vapor whose length would be grown up to 13 μm. The metallic TaSi₂ nanowires exhibit excellent electrical properties with remarkable high failure current density of 3 × 10⁸ A cm^− 2. In addition, the growth mechanism is addressed in detail, The TaSi₂ nanowires are formed in three steps: segregation of Si atoms from the FeSi₂ thin film and NiSi₂ films underlayer to form Si base, growth of TaSi₂ nanodots on Si base, and elongation of TaSi₂ nanowire along the growth direction. This simple approach promises future applications in nanoelectronics and nano-optoelectronics.     

ZnO nanowires by pulsed laser vaporization: synthesis and properties

We report a new pulsed-laser vaporization (PLV) technique to synthesize nanowires of single-crystal ZnO having a wurtzite structure by using colloidal gold nanoparticles as seeding catalysts. The average diameter of the nanowires is approximately 13 nm, with a very narrow range of 7 to 25 nm. The nanowires are straight for the most part, with the axes parallel to the [0001] growth direction. Raman and photoluminescence spectra from the nanowires and bulk ZnO are similar except for a approximately 510 nm band in the nanowires due to oxygen vacancies. The bulk-like vibrational and electronic properties of the nanowires is due to the diameter being larger than the threshold below which quantum confinement-induced effects are expected.     

Polyurethane-maleamides for cardiovascular applications: synthesis and properties

Several polyurethane-maleamides (PUMAs) containing polyether or polycarbonate soft segments, and aromatic or aliphatic hard segments were synthesized by solution or bulk polymerization, using maleic acid (MA) or a mixture of MA and butanediol as chain extenders. Using this process, activated double bonds are introduced into the polymer chains and the base polyurethanes may undergo further modification via specific grafting, thus improving their tissue compatibility. PUMAs chemicophysical properties were evaluated by gel permeation chromatography (GPC), intrinsic viscosity analyses, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR) and tensile mechanical tests. Polycarbonate diol (PCU)-based PUMAs showed higher molecular weights than polyether diol (PEU)-based ones. The use of butanediol in mixture with maleic acid led to an increase of molecular weights. FT-IR confirmed the presence of the bands related to the amide groups and to the conjugated double bond, yet more evident for the polymer obtained in solution. The higher crystallinity shown by this polymer was also indicative of a better phase separation. All the PCU-PUMAs exhibited similar tensile properties with a higher stiffness than PEU-PUMAs. Among the PEU-PUMAs, the highest tensile properties were shown by the polymer obtained in solution, and by the one derived from a mixture of maleic acid and butanediol.     

Review on oxides of antimony nanoparticles: synthesis,properties, and applications

In this article, synthesis methods, properties, and applications of antimony oxide nanoparticles are reviewed. Oxides of antimony exist in three phases, namely antimony trioxide, antimony tetroxide, and antimony pentoxide. Physical and optical properties of these nanoparticles are reviewed and compared with their bulk forms. According to literature works, a total of eight synthesis methods have been used to produce these nanoparticles. The size, distribution, shape, and structure of the nanoparticles which are synthesized by different methods are compiled and compared. It is reported that the properties are strongly dependent on the synthesis methods. Advantages and disadvantages of each synthesis method are discussed and compared. Most literatures report on the optical and physical properties of the nanoparticles. Reports on the electrical properties are scarce. As the applications of these nanoparticles cover a wide range, several challenges must be overcome to use them well. These challenges are also being presented and explained in this article.     

Low dimensional silver nanostructures: synthesis, growth mechanism, properties and applications

This work presents a review of the recent advances on the low-dimensional (LD) silver nanostructures (e.g., one-dimensional nanorods and nanowires, and two-dimensional nanoplates and nanodisks). First, the methods, either physical or chemical, for the synthesis of silver LD nanostructures are introduced. Then, the use is discussed of advanced experimental techniques (e.g., transmission electron microscope, high-resolution transmission electron microscope, scanning electron microscope, atomic force microscope, ultraviolet-visible and Raman spectra) and theoretical techniques at different time and length scales from quantum mechanics (e.g., ab initio simulation and density function theory) to molecular dynamics method for understanding the principles of governing particle growth, as well as discrete dipolar approximate method for understanding the optical properties of different shapes and sizes of silver LD nanostructures. Subsequently, the functional applications of the LD silver nanostructures in different areas such optical, electronic, and sensing, particularly for those related to surface plasma resonance are summarized based on the recent findings. Finally, some perspectives and comments for future investigation of silver nanostructures are also briefly discussed.     

Self-assembled molecular nanowires of 6,13-Bis(methylthio)pentacene: growth, electrical properties, and applications

We demonstrate a comprehensive study of self-assembled molecular nanowire, including molecular design, one-dimensional crystal growth, resistivity measurement of individual wire, and application to a field-effect transistor. Appropriate molecular design and control of interfacial interactions lead to single crystalline wire growth with an extensive pi-stacking motif. Resistivity measurements of an individual molecular wire indicate that these structural features are advantageous for electrical transport. Finally, field-effect transistors with single- and double-wire channels were fabricated to give some indication of the potential application of the molecular wires.     

Sonochemical synthesis of platinum nanowires and their applications as electro-chemical actuators

We report the sonochemical synthesis of platinum nanowires on carbon nanotube templates and their application in electrochemical actuation. The fabrication of platinum nanowires was achieved by suspending well separated single wall carbon nanotubes in isopropyl alcohol and ultra-sonically agitating the solution in the presence of dihydrogen hexachloroplatinate. The platinum nanowires were further processed into micro and macro scale free standing sheets by vacuum filtration. An electrochemical cantilever actuator was constructed using the platinum nanowire sheet which actuated under electrical bias. Displacement of '3 mm was readily achieved when the electrical potential was swept at low voltages between -2 V and 2 V at a scan rate of 200 mV/s. The actuator showed the metallic actuation characteristics instead of that from carbon nanotubes. These results show the applicability of metallic nanomaterials for actuation technologies.     

One-dimensional 8-hydroxyquinoline metal complex nanomaterials: synthesis,optoelectronic properties,and applications

One-dimensional (1D) 8-hydroxyquinoline metal complex nanomaterials exhibit distinctive characteristics that differ from those of their bulk counterparts. Owing to their small size, shape anisotropy, unique structures, and novel properties, these organometallic 1D nanostructures are promising candidates for various devices. This review highlights current progress in the synthesis of 1D 8-hydroxyquinoline metal complex nanomaterials and summarizes their optoelectronic properties and applications. The mainly synthetic strategies are divided into three categories, which include vapor phase growth, solution phase growth, and self-assembly. Special attention is paid to the formation mechanisms and the control measures for 1D nanostructured 8-hydroxyquinoline metal complexes. Other new methods such as template-based synthesis and electrospinning are briefly described. Merits and shortcomings of each synthetic strategy are simply discussed. Then, a variety of optoelectronic properties including luminescence, field emission, charge transport, photoconductivity, and photo-switching properties are reviewed, and their applications in optoelectronic devices, field emission, and templates are also surveyed. In the end, concise conclusions are provided, and personal perspectives on future investigations of 1D 8-hydroxyquinoline metal complex nanomaterials are proposed.     

Nanowires: properties,applications and synthesis via porous anodic aluminium oxide template

Quasi one-dimensional nanowires possess unique electrical, electronic, thermoelectrical, optical, magnetic and chemical properties, which are different from that of their parent counterpart. The physical properties of nanowires are influenced by the morphology of the nanowires, diameter dependent band gap, carrier density of states etc. Nanowires hold lot of promises for different applications. Basic electronic devices like junction diodes, transistors, FETs and logic gates can be fabricated by using semiconductor and superlattice nanowires. Thermoelectric cooling system can be fabricated by using metallic nanowires. Semiconductor nanowire junctions can be used for different opto-electronic applications. Moreover, periodic arrays of magnetic nanowires hold high potential for recording media application. Nanowires are also potential candidates for sensor and bio-medical applications. In the present article, the physical and chemical properties of nanowires along with their probable applications in different fields have been reviewed in detail. The review also includes highlights of the synthesis of nanowires via porous anodic aluminium oxide template since the technique is simple, cost-effective and a low temperature technique.     

Perovskite oxide nanowires: synthesis, property and structural characterization

Perovskite oxide materials display a wide spectrum of functional properties, including switchable polarization, piezoelectricity, pyroelectricity, and non-linear dielectric behavior. These properties are indispensable for application in electronic devices such as non-volatile memories, sensors, microactuators, infrared detectors, microwave phase filters, and so on. Recent advances in science and technology of perovskite oxide materials have resulted in the feature sizes of perovskite oxides-based electronic devices entering into nanoscale dimensions. At nanoscale perovskite oxide materials exhibit a pronounced size effect manifesting itself in a significant deviation of the properties of low-dimensional structures from the bulk and film counterparts. In the last decade low-dimensional perovskite nanosized oxides have been received much attention because of their superior physical and chemical properties. Among them, perovskite oxide nanowires are especially attractive for nanoscience studies and nanotechnology applications. Compared to other low-dimensional perovskite oxide systems, perovskite oxide nanowires are not only used as the building blocks of future nanodevices, but also they offer fundamental scientific opportunities for investigating the intrinsic size effects of physical properties. In the recent years, much progress has been made both in synthesis and physical property testing of perovskite oxide nanowires, which have a profound impact on the nanoelectronics. In this work, an overview of the state of art in perovskite oxide nanowires is presented, which covers their synthesis, property, and structural characterization. In the first part, the recent literatures for fabricating perovskite oxide nanowires with promising features, are critically reviewed. The second part deals with the recent advances on the physical property testing of perovskite oxide nanowires. The third part summarizes the recent progress on microstructural characterizations of perovskite oxide nanowires, to improve their crystalline quality, morphology and uniformity. Finally, this review concludes with some perspectives and outlook on the future developments of perovskite oxide nanowires.     

Organic/inorganic thermoelectric composites electrochemical synthesis,properties, and applications

Organic/inorganic thermoelectric composites have played an important role in the development of new, green, and renewable energy sources with potential applications in efficient thermal management, flexible electronics, and bioelectronics. Electrochemical syntheses, including electropolymerization, electrochemical deposition, electrochemical doping, electrochemical post-processing, etc., require no addition of surfactants or oxidants, the products of which are easy to separate and purify, providing clean, efficient, and facile routes for the preparation of organic thermoelectric materials and their composites. In this review, the preparation, properties, and applications of organic/inorganic thermoelectric composites from electrochemical synthesis were reviewed in detail, offering a perspective on the recent advances in the field.

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Optical properties of laterally aligned Si nanowires for transparent electronics applications

We have investigated the optical properties of laterally aligned Si nanowire (SiNW) arrays in order to explore their potential applicability in transparent electronics. The SiNW array exhibited good optical transparency in the visible spectral range with a transmittance of ∼90% for a NW density of ∼20–25 per 10 μm. In addition, polarization-dependent measurements revealed a variation in transmittance in the range of 80%–95% depending on the angle between the polarization of incident light and the NW axis. Using the SiNWs, we demonstrated that transparent transistors exhibit good optical transparency (greater than 80%) and showed typical p-type SiNW transistor characteristics.