This updated second edition puts nanotechnology into perspective by explaning issues in health, environmental and military application domains, and discusses the technology in the context of current media and ethical debates.
Inspec keywords: nanoelectronics; electronic structure; nanofabrication; nanomagnetics; nanocomposites; molecular electronics; plastics
Other keywords: nanostructure fabrication; reviews; atomic cohesion; nanosystems; electronic structures; book; atomic structure; neuroelectronics; organic-matrix-based nanocomposites; nanotechnology revolution; plastic electronics; nanomagnetism; molecular electronics
Subjects: Amorphous and nanostructured magnetic materials; Magnetic properties of nanostructures; Low-dimensional structures: growth, structure and nonelectronic properties; Polymers and plastics (engineering materials science); Molecular electronics; Methods of nanofabrication and processing; Electron states in low-dimensional structures; Composite materials (engineering materials science)
This chapter reviews the history of the revolution of nanotechnologies. The following topics are dealt with: from micro- to nanoelectronics; from the macroscopic to the nanoscopic world; from fundamentals to applications; a different physics; some examples; and various applications.
In this chapter, the principal characteristics of surfaces of solids was discussed. This will help to understand their role in the cohesion of nanoparticles. The transition from solid state to nanoparticle is not abrupt. To verify it, the thermodynamic approach was used, in which the macroscopic concept of superficial tension remains valid. This top-down approach is interesting because it allows to understand the essential factors of the cohesion in nanoparticles, free or coated, or even constrained when they are encapsulated in a solid matrix. Thermodynamics is valid when the number of atoms in the nanoparticle is high, but it is not valid any more for small particles.
This chapter introduces the concept of an ideal nanocrystal, known as quantum dot, which will help explain the particular properties of nanosystems. Electronic-state density of atoms and molecules was discussed. The electronic energy levels are calculated by well-known methods of atomic and molecular physics, and quantum chemistry.
In this chapter we will describe the emergence of the field of molecular electronics, particularly the different types of components developed at a molecular scale, which can be involved in the integrated circuit of the future.
Within the integrated circuits of computers (which we can compare to 'artificial brains'), the data transmission between the different elementary elements the transistors is made by electrical impulse. It is interesting to note that within the human brain, and between the brain and the other different organs, transmission of information (a function fulfilled by the nervous system) is also based on electrical phenomena. The sending of information all along the system of nerve cells (neurons) is expressed by the propagation of a change in the electrical charge of the neurons' membrane. In this way, an electrical impulse goes through the nervous system to the organs. The electrical characteristics of nerve impulses were demonstrated two centuries ago, during a well-known experiment in which Volta placed two electrodes on frogs' legs and applied a voltage, in this way producing a movement. But it is only recently that the similarity between the transmission process of information in microelectronics systems and the nervous systems made researchers think of correlating transistors and neurons. This new scientific field, which relates microelectronics concepts and neurology, has been named neuroelectronics. The first point of interest in this approach (making transistors and neurons communicate with each other) is that an integrated circuit associated with a neuron (or a group of neurons) forms a sensor of the neurons' activity. Then, those systems would be able to monitor in vitro (within test tubes) the effect of new medicine on the nervous system, which will allow the reduction of in vivo (m-the-body) tests (on animals). The functioning of the human brain (a network of more than a hundred billion neurons) is far from being completely understood. To connect a neuron network to a microelectronic integrated circuit would allow the network to be observed while it was working and then to better understand the functioning of our brain; moreover, it would allow the use of this network to assist the computer in some tasks and calculations. This is the second major aspect of neuroelectronics. Finally, we can also imagine that an artificial microelectronics system could restore the communication in an area of the nervous system damaged after an ill ness or an accident. Those artificial neurons could be used for instance to repair spinal-cord injuries after some accidents. Of course, all those applications exist currently only in the speculative world of researchers, but the recent advances of neuroelectronics (a scientific field only ten years old) are promising. In the next sections these progresses will be briefly presented.
Most known polymer materials behave like good electrical insulators; therefore, most sheaths of electric cable are made of polypropylene. However, a specific group of polymers known as conjugated polymers reveal amazing electrical properties. Thanks to a simple oxido-reduction reaction known as chemical doping, electrical properties of conjugated polymers can be increased by a few orders of magnitude and can even become comparable to the conductivity of some common metals such as iron and copper, which is suggested by the term they are known by: synthetic metals. As a matter of interest. Synthetic Metals is the name of an international scientific journal that publishes works done on conducting polymers, and Professor Alan Heeger (co-winner of the 2000 Nobel Prize in Chemistry) has long been its principal editor The interest for conducting plastics is that, in a single material, the electrical properties of metal can be combined with the mechanical properties of polymers (plasticity, lightness, ease of manufacture, low cost, etc.) This potential leads to significant advances in the development of conducting polymers for technological applications. Some of them have been achieved, e.g.. antistatic plastic films that cover photography films produced by Agfa-Gevaert SA.
This chapter of the book about fabrication of nanostructures is subdivided into 8 parts. It discusses the situation of the problem; contribution of supramolecular chemistry; semiconducting nanoribbons; creation of nanostructures; patterning; hybrid techniques; writing via local probe microscopy; and design and development of molecular circuits.
A nanocomposite is a composite material whose dispersed phase constitutes particles at least one of whose free dimensions is in the order of a nanometre or a few dozen nanometres at maximum. Under this definition, many metal-matrix-based nanocomposites are gathered (for instance materials resulting from the dispersion of nanoparticles of oxide, nitride, or metal carbide in matrices or metal alloy), ceramic or inorganic matrices-based nanocomposites, or nanocomposites based on organic matrices. The last group is described in this chapter, with a particular focus on polymer matrices.
In this chapter, the use of nanomagnets can resolve the issue of the selection of the zone to heat. In fact, in this case the dissipated heat is directly proportional to the concentration of magnetic nanocrystals. The heated zone will then be the reflection of the bioselectivity of the nanomagnets for the pathology to be treated. The frequency of the variation of the magnetic field used (between 100 and 300 kHz) will be a thousand times lower than the one used in a classical thermotherapy irradiation. This allows a heat dissipation caused exclusively by the interaction between magnetic field and magnetic nanocrystals.
This chapter discusses nanotechnologies in perspective with regards to the following topics: health and environmental issues; military interests; media and ethical considerations; NBIC (nanotechnologies, biotechnologies, information technology and cognitive sciences); and education issues.
In this appendix, only transmission electronic microscopy (TEM) will be discussed here. This technique represents a good choice for a tool for the study of nanomaterials, since it allows direct imaging of the samples. By observation of transversal sections, the linages can be obtained both at the surface and inside the sample. Structural characteristics, such as shape, size and distribution of nanometric precipitates, can in this way be obtained. Furthermore, the advent of high-resolution techniques has allowed us to examine samples down to the atomic scale, and consequently to have a precise idea of their nanostructure. To conclude, electronic microscopy techniques seem to have revolutionized and allowed the nanotechnologies domain to develop by their capacity to show the link between fabrication, structure and properties of nanomaterials, and all that down to the atomic scale.
Physical effects that are important at our scale, such as gravity, are negligible at the micrometre scale and at the scale at which nanomateπals work. The molecular attraction forces and the surface effects are predominant. For this reason, it is important to know the chemical nature of nanomaterials' surfaces perfectly. There fore, surface-analysing techniques such as X photoemission spectroscopy (XPS) and time-of-flight secondary ions mass spectroscopy (ToF-SIMS) play a vital part and can be an efficient tool for the characterization of nanomaterials' surfaces. These two techniques can be used on a great variety of materials: metals, oxides, nitrates, carbides, organic compounds, etc., being either in bulk form as a thin film or in monolayer form.
The main application of the nuclear magnetic resonance (NMR) phenomenon is indisputably magnetic resonance imaging (MRI). This technique has been widely used for more than 15 years in the medical environment as a diagnosis tool. It allows the formation of contrasted anatomic images from the NMR signal of the protons of human bodies. The contrast is imposed by the protons' density of the tissues, by the longitudinal (T1) and transverse (T2) relaxation time, and by the acquisition parameter of the image.
