Nanomaterials, Polymers and Devices

Materials Functionalization and Device Fabrication

E. S. W. Kong

• Publisher: Wiley
• Year: 2015
• ISBN:
  9781118867198
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Industrial & Technical Chemistry

Providing an eclectic snapshot of the current state of the art and future implications of the field, Nanomaterials, Polymers, and Devices: Materials Functionalization and Device Fabrication presents topics grouped into three categorical focuses:

• The synthesis, mechanism and functionalization of nanomaterials, such as carbon nanotubes, graphene, silica, and quantum dots
• Various functional devices which properties and structures are tailored with emphasis on nanofabrication. Among discussed are light emitting diodes, nanophotonic, nano-optical, and photovoltaic devices
• Nanoelectronic devices, which include semiconductor, nanotube and nanowire-based electronics, single-walled carbon-nanotube based nanoelectronics, as well as thin-film transistors

Chapter 1
The Functionalization of Carbon Nanotubes and Nano-Onions

Karthikeyan Gopalsamy¹, Zhen Xu¹, Chao Gao¹ and Eric S.W. Kong²

¹MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, People's Republic of China

²Research Institute of Micro/Nanometer Science & Technology, Shanghai Jiao Tong University, Shanghai, People's Republic of China

1.1 Functionalization of Carbon Nanotubes

The unique structure and morphology of carbon nanotubes have kept attracting researchers to explore their novel properties and applications since their discovery by Iijima in 1991 (1). Carbon nanotube (CNT) is a tubular structure made of carbon atoms and denoted as single-walled or multiwalled CNTs, having diameter of nanometer scale but length in micrometers. As in graphite, the carbon atoms in CNTs are in sp² hybridization and these sp² carbon sets give a great mechanical strength to CNTs. Single-walled carbon nanotubes (SWCNTs) are narrow and possess the simplest geometry and have been observed with diameters ranging from 0.4 to 3 nm. Multiwalled carbon nanotubes (MWCNTs) possess diameters of up to 100 nm. In general, pure CNTs have all carbons bonded in a hexagonal pattern except at their ends, and other defects in the sidewalls and the formation of various patterns resulting from the mass production generally humiliate desired properties.

Starting from diamond and fullerene to related nanostructures (Fig. 1.1) (2), CNTs have progressive properties, and during the past decade, CNTs had fascinated much attention for their electronic and mechanical properties. One of the main challenges in implementing serious applications of CNTs is functionalizing them. The lack of solubility and the difficult processing of CNTs in solvents impose great limitations to the practical applications of CNTs. Therefore, surface functionalization of CNTs has become the focus of research in recent years in order to improve their compatibility with matrices. Several methods, such as covalent or noncovalent functionalization, have been developed to achieve effective dispersion and bonding without the loss of properties of CNTs. The scope of applicability of CNTs has been expanded by extensive research particularly on tuning structural and electronic properties. According to the reports in recent times, CNTs have been used for many purposes and still implementation has been done day to day. Among those diverse applications, CNTs alone find some limitations in thermal, electrical, and mechanical properties, and this can be improved by combining them with certain polymers. Grafting polymers on CNTs is likely to improve the thermal and electrical properties (3, 4). Nanotube reinforcement into the polymer matrix has been considered as the primary need in order to obtain strongly enough composites (5). In general, CNTs have hollow structure and a very high aspect ratio (length-to-diameter ratio) which help them to form a network of conductive tubes. The surface properties of CNT-grafted polymers have been reported early by Downs and Baker (6) and Thostenson et al. (7). In particular, surface area tends to increase by the growth of nanofibers when compared to conventional process as predicted by Downs et al. It was observed that the surface area increased around 300 times and the interfacial shear strength by 4.75 times. From then, the feasibility of grafting CNT–polymers has been investigated to a larger extent and the nanotube composites have been designed according to the requirement of specific applications. The development of polymer–CNT composite methodology is based on improving the dispersion and controlling the orientation of CNTs in the polymer matrix (8). In general, high resistance at the nanotube–matrix interface limits thermal transfer along percolating networks of CNTs. However, viscoelasticity of the nanocomposites has been greatly enhanced by the nanotube network interpenetrating the polymer template. The small cross-sectional dimensions and extreme length of the CNTs allow bending to a large extent to have good intertube interactions under processing conditions. It has been clearly explained that the CNTs not only influence the electrical or thermal properties but they also eliminate the die swell, a problem faced during polymer processing (9).

Figure 1.1 Model structures of carbon: (a) diamond, (b) fullerene, (c) multilayer fullerene, (d) single-walled carbon nanotubes, (e) double-walled carbon nanotubes, (f) multiwalled carbon nanotubes, and (g) graphene. (Reproduced with permission from Reference (2)).

1.1.1 Surface Chemistry of CNTs (Small Molecules)

After the CNTs came into existence, the structure, surface properties, and formation mechanism took the prime place to prove one or the other. Surface modification of pristine CNTs with no damage to CNT sidewalls is indispensable in current materials world when concerned with the mass production. Much of the applications involve the interaction of the CNT with the surrounding medium, and in particular, for example, molecules encapsulated or bonded/grafted in or to the CNTs. In these systems, the hydrophobic–hydrophilic behavior of the CNT is considered to be important to achieve well-designed surface-modified CNT materials. In general, CNTs line up into bundle of ropes held together by van der Waals (VDW) forces, more distinctively, pi-stacking. Ruoff et al. suggested that adjacent nanotubes which are present within the multiple cylindrical layers could be deformed by VDW forces, thereby destroying cylindrical symmetry (10). It is also important to note that the interaction between a CNT and the environment mainly consists of VDW forces (either attractive or repulsive force). It is these forces that are strong enough to insert molecules inside the CNT channel. The next step of explanation could be well understood in a simple CNT–molecule–water system. The molecule remains encapsulated inside the CNT channels, and based on the energy change during this process, it was proposed that the largest energ...

Table of contents

• Cover
• Title Page
• Copyright
• Table of Contents
• Contributors
• Foreword
• Chapter 1: THE FUNCTIONALIZATION OF CARBON NANOTUBES AND NANO-ONIONS
• Chapter 2: THE FUNCTIONALIZATION OF GRAPHENE AND ITS ASSEMBLED MACROSTRUCTURES
• Chapter 3: DEVICES BASED ON GRAPHENE AND GRAPHANE
• Chapter 4: LARGE-AREA GRAPHENE AND CARBON NANOSHEETS FOR ORGANIC ELECTRONICS: SYNTHESIS AND GROWTH MECHANISM
• Chapter 5: Functionalization of Silica Nanoparticles for Corrosion Prevention of Underlying Metal
• Chapter 6: NEW NANOSCALE MATERIAL: GRAPHENE QUANTUM DOTS
• Chapter 7: Recent Progress of Iridium(III) Red Phosphors for Phosphorescent Organic Light-Emitting Diodes
• Chapter 8: Four-Wave Mixing and Carrier Nonlinearities in Graphene–Silicon Photonic Crystal Cavities
• Chapter 9: Polymer Photonic Devices
• Chapter 10: Low Dielectric Contrast Photonic Crystals
• Chapter 11: Microring Resonator Arrays for Sensing Applications
• Chapter 12: Polymers, Nanomaterials, and Organic Photovoltaic Devices
• Chapter 13: Next-Generation GA Photovoltaics
• Chapter 14: Nanocrystals, Layer-by-Layer Assembly, and Photovoltaic Devices
• Chapter 15: Nanostructured Conductors for Flexible Electronics
• Chapter 16: Graphene, Nanotube, and NANOWIRE-Based Electronics
• Chapter 17: NANOELECTRONICS BASED ON SINGLE-WALLED CARBON NANOTUBES
• Chapter 18: Monolithic Graphene–Graphite Integrated Electronics
• Chapter 19: THIN-FILM TRANSISTORS BASED ON TRANSITION METAL DICHALCOGENIDES
• Index
• End User License Agreement