Polymer/carbon nanotube (CNT) composites are expected to have good processability characteristics of the polymer and excellent functional properties of the CNTs. The critical challenge, however, is how to enhance dispersion and alignment of CNTs in the matrix. Here, we review recent progress and advances that have been made on: (a) dispersion of CNTs in a polymer matrix, including optimum blending, in situ polymerization and chemical functionalization; and (b) alignment of CNTs in the matrix enhanced by ex situ techniques, force and magnetic fields, electrospinning and liquid crystalline phase-induced methods. In addition, discussions on mechanical, thermal, electrical, electrochemical, optical and super-hydrophobic properties; and applications of polymer/CNT composites are included. Enhanced dispersion and alignment of CNTs in the polymer matrix will promote and extend the applications and developments of polymer/CNT nanocomposites.

Dispersion and alignment of carbon nanotubes in polymer matrix: A review

It is estimated that the world will need to double its energy supply by 2050. Nanotechnology has opened up new frontiers in materials science and engineering to meet this challenge by creating new materials, particularly carbon nanomaterials, for efficient energy conversion and storage. Comparing to conventional energy materials, carbon nanomaterials possess unique size-/surface-dependent (e.g., morphological, electrical, optical, and mechanical) properties useful for enhancing the energy-conversion and storage performances. During the past 25 years or so, therefore, considerable efforts have been made to utilize the unique properties of carbon nanomaterials, including fullerenes, carbon nanotubes, and graphene, as energy materials, and tremendous progress has been achieved in developing high-performance energy conversion (e.g., solar cells and fuel cells) and storage (e.g., supercapacitors and batteries) devices. This article reviews progress in the research and development of carbon nanomaterials during the past twenty years or so for advanced energy conversion and storage, along with some discussions on challenges and perspectives in this exciting field.

Carbon Nanomaterials for Advanced Energy Conversion and Storage

From diagnosis of life-threatening diseases to detection of biological agents in warfare or terrorist attacks, biosensors are becoming a critical part of modern life. Many recent biosensors have incorporated carbon nanotubes as sensing elements, while a growing body of work has begun to do the same with the emergent nanomaterial graphene, which is effectively an unrolled nanotube. With this widespread use of carbon nanomaterials in biosensors, it is timely to assess how this trend is contributing to the science and applications of biosensors. This Review explores these issues by presenting the latest advances in electrochemical, electrical, and optical biosensors that use carbon nanotubes and graphene, and critically compares the performance of the two carbon allotropes in this application. Ultimately, carbon nanomaterials, although still to meet key challenges in fabrication and handling, have a bright future as biosensors.

Carbon Nanomaterials in Biosensors: Should You Use Nanotubes or Graphene?

Gas sensors operate by a variety of fundamentally different mechanisms1,2,3,4,5,6,7,8,9,10,11,12,13,14. Ionization sensors13,14 work by fingerprinting the ionization characteristics of distinct gases, but they are limited by their huge, bulky architecture, high power consumption and risky high-voltage operation. Here we report the fabrication and successful testing of ionization microsensors featuring the electrical breakdown of a range of gases and gas mixtures at carbon nanotube tips. The sharp tips of nanotubes generate very high electric fields at relatively low voltages, lowering breakdown voltages several-fold in comparison to traditional electrodes, and thereby enabling compact, battery-powered and safe operation of such sensors. The sensors show good sensitivity and selectivity, and are unaffected by extraneous factors such as temperature, humidity, and gas flow. As such, the devices offer several practical advantages over previously reported nanotube sensor systems15,16,17. The simple, low-cost, sensors described here could be deployed for a variety of applications, such as environmental monitoring, sensing in chemical processing plants, and gas detection for counter-terrorism.

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Miniaturized gas ionization sensors using carbon nanotubes

▪ Abstract This account reviews the discovery, synthesis, properties, and the latest research advances of carbon nanotubes developed over the past 12 years. Because of their remarkable electronic and mechanical properties, carbon nanotubes are unique and exciting. The field has been developed rapidly, and the number of publications per year is increasing almost exponentially. Various technological applications are likely to arise using nanotubes for fabrication of flat panel displays, gas storage devices, toxic gas sensors, Li+ batteries, robust and lightweight composites, conducting paints, electronic nanodevices, etc. Further experimental and theoretical research is still necessary so that novel technologies will become a reality in the early twenty-first century.

Science and Technology of the Twenty-First Century: Synthesis, Properties, and Applications of Carbon Nanotubes

Cunning refinements help to customize the architecture of nanotube structures. Nanoscale structures need to be arranged into well-defined configurations in order to build integrated systems. Here we use a chemical-vapour deposition method with gas-phase catalyst delivery to direct the assembly of carbon nanotubes in a variety of predetermined orientations onto silicon/silica substrates, building them into one-, two- and three-dimensional arrangements. The preference of nanotubes to grow selectively on and normal to silica surfaces forces them to inherit the lithographically machined template topography of their substrates, allowing the sites of nucleation and the direction of growth to be controlled.

Microfabrication technology: Organized assembly of carbon nanotubes

Controllable assembly of ordered nanoscale structural units in geometrically well-defined configurations is essential for building integrated nanoscale systems. Here, we describe a powerful method to simultaneously grow aligned carbon nanotube bundles in multiple, predetermined orientations on planar substrates to build one- to three-dimensional architectures. We effect multidirectional nanotube growth by gas-phase delivery of a xylene−ferrocene mixture on to lithographically machined silica surface templates. The preference of nanotubes to grow normal to, and selectively on, silica surfaces forces the nanotubes to inherit the topography of the substrate templates, enabling premeditated selection of both nucleation sites and growth direction. By using silica templates of different shapes, we can build a wide variety of organized nanotube structures of differing complexity and shapes, density, dimensions, and orientation, for example, mutually orthogonal arrays of pillars and platelets, films with hierarch...

Assembly of Highly Organized Carbon Nanotube Architectures by Chemical Vapor Deposition

Substrate effects on the growth of carbon nanotubes by thermal decomposition of methane

Simultaneous growth of silicon carbide nanorods and carbon nanotubes by chemical vapor deposition

To build nanotube based nanodevices, controlling the growth of aligned carbon nanotubes will be essential. Our group reported a method for growing aligned nanotube selectively on SiO 2 surfaces by thermal chemical vapor deposition (CVD) method from xylene-metallocene mixtures. Here we will describe further studies on the roles of shape and thickness of patterned oxide structures for the controlled growth of aligned carbon nanotubes. By designing the shapes and the thickness of silicon oxide patterns with conventional micro fabrication techniques like lithography and dry & wet etching we could control the growth position as well as orientation of aligned carbon nanotubes precisely.

J. Ward

Papers

Microfabrication technology: Organized assembly of carbon nanotubes

Assembly of Highly Organized Carbon Nanotube Architectures by Chemical Vapor Deposition

Substrate effects on the growth of carbon nanotubes by thermal decomposition of methane

Simultaneous growth of silicon carbide nanorods and carbon nanotubes by chemical vapor deposition

Controlling the aligned growth of carbon nanotubes by substrate selection and patterning