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Über dieses Buch

This book features comprehensive explanations from the classical theory of high-energy particle interactions with matter to their use for a novel nanofabrication technique for various organic soft materials. Potential readers include scientists and engineers in both academia and industry, as well as students of materials science, nanotechnology, and nuclear power engineering. Readers will learn about the historical research background of radiation chemistry and interactions of an accelerated particle with matter, and then move on to recent research topics having to do with nanofabrication of soft materials by using single charged particles with high energy. Target materials of the highlighted novel technique include proteins, thermo-responsive and photo-responsive polymers, semiconducting polymers, and even small organic molecules. The descriptions of these various newly developed nanomaterials will interest a broad spectrum of readers and provide them with a new perspective. The many conceptual illustrations and microscopic images of nanomaterials that are included will help readers to easily understand the contents of the book.

Inhaltsverzeichnis

Frontmatter

Chapter 1. High-Energy Charged Particle Interaction with Matter

Abstract
Ionizing radiation interacting with matter releases energy via a variety of processes, leading to chemical reactions and stable chemical bond formation. In this chapter, the primary interactions are schematized in view of an incident “ray” or charged particle as its slowing down process, with an important term of “stopping power” of the target materials. The energy released by an incident particle into unit volume is huge compared to that required for a chemical reaction, hence formation of a chemical bond. The overall dissipation process of the energy given directly by an incident charged particle is reviewed here, as well as the characteristic feature of the processes caused by high-energy charged particle with the long history of investigation of ionizing radiations and tremendous and well-sophisticated theoretical aspects on their physical interaction with the matters. Nonhomogeneous distribution of energy within a cylindrical area along the trajectory of a charged particle is the key to promote unique chemical reactions in an “ion track,” in connection with the single particle-induced/triggered nano-materials fabrication discussed in the following chapters.
Shu Seki, Tsuneaki Sakurai, Masaaki Omichi, Akinori Saeki, Daisuke Sakamaki

Chapter 2. Chemistry of High-Energy Charged Particles: Radiations and Polymers

Abstract
As reviewed in Chap. 1, the energy released by a charged particle in the limited spatial area is extremely huge in comparison with the energy of chemical bondings. However, the area is nm-sized and nothing happens out of the area, leading to the relatively small amount of the energy given by the charged particle in comparison with the thermodynamic energy averaged over the total volume and mass of the target materials. This suggests it hard to induce stoichiometric reaction in the molecular materials by the radiation chemical processes. Radiations met polymeric materials at an early era of the radiation physical chemistry in the beginning of twentieth century, where the drastic physical property change of the polymer materials was caused by the relatively small number (non-stoichiometric) of the reaction points to the total amount of substance in the target formed by radiation chemical processes. The combination of macromolecules and radiations were so-called the “best-match,” and developed into radiation processing of rubbers and the other polymeric materials. The basic aspects of the radiation chemical processes in macromolecular materials are overlooked in this chapter, and the unique feature of chemical reactions traced by bulk analysis is discussed in case of high-energy charged particle, inspiring “materials fabrication by A particle” discussed in the following chapter.
Shu Seki, Tsuneaki Sakurai, Masaaki Omichi, Akinori Saeki, Daisuke Sakamaki

Chapter 3. A Particle with High Energy: A Versatile Tool for Nanomaterials

Abstract
Unique characteristics of bulk radiation chemical reactions induced by high energy charged particle suggest strongly non-homogeneous process of the reactions limited in an ion track, and giving also the estimate of the size of spatial distribution ranging a few to tens nm. Herein, the high-energy charged particles become only the candidate of ionizing radiation which can cause “stoichiometric” chemical reactions in an ion track via condensed reactive intermediates in the area, and enable to produce “a nanomaterial” by “a particle”. The process called as “Single Particle Nanofabrication Technique” has been realized and utilized miniaturization of a variety of polymeric materials, suggesting versatile nature of the technique for nanofabrication. The visualization of the produced 1-dimensional nanomaterials are demonstrated in the present chapter, as well as the totally theoretical model of the energy distribution in an ion tack giving good interpretation to the sizes of produced nanomaterials. The present technique has been realized by a “charged particle”, but the size of the field of chemical reactions has also been revealed to be defined by the target polymer materials themselves. This is suggestive that the present methodology is neither “top-down” nor “bottom-up” approaches in the miniaturization of materials and nanotechnologies, but a unique and versatile tool for nanomaterials fabrication.
Shu Seki, Tsuneaki Sakurai, Masaaki Omichi, Akinori Saeki, Daisuke Sakamaki

Chapter 4. Bio-compatible Nanomaterials

Abstract
Protein nanowires exhibiting specific biological activities hold promise for interacting with living cells and controlling and predicting biological responses such as apoptosis, endocytosis, and cell adhesion. In this chapter, fabrication of various size-controlled protein nanowires by single-particle nanofabrication technique (SPNT) is reviewed. The human serum albumin (HSA) nanowires of various lengths can be fabricated, from HSA nanodots to HSA nanowires with extremely high aspect ratios of over 1000, by controlling the thickness of the film. The diameters of the protein nanowires are almost equal to the diameter of self-assembled protein and peptide nanostructures. Degradation of the HSA nanowires was examined using protease. The biotinylated human serum albumin nanowires can be transformed into nanowires exhibiting a biological function such as an enzyme through using avidin–biotin interaction. Interestingly, 2D Protein sheets and protein synthetic polymer nanowires can be fabricated by the application of SPNT. SPNT is a versatile platform for functionalizing the surface of any protein molecule with an extremely large surface area.
Shu Seki, Tsuneaki Sakurai, Masaaki Omichi, Akinori Saeki, Daisuke Sakamaki

Chapter 5. Stimuli-Responsive Nanomaterials

Abstract
A single particle nanofabrication technique (SPNT) was successfully applied to the fabrication of homogeneous thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) nanowires over a large area, using N,N′-methylene-bis-acrylamide (MBAAm) as a cross-linker. The PNIPAAm nanowires with high aspect ratio over 130 were formed uniformly on the substrate, and the mechanical strength and the length of the nanowires can be easily controlled by adjusting the MBAAm content. The nanowires were transformed from the non-aggregated to aggregated forms over a lower critical solution temperature (LCST) of approximately 32 °C in water. Furthermore, well-defined and uniform nanowires of the photoresponsive polymer, which composed of photochromic azobenzene and π-conjugated fluorene units, were successfully fabricated by the SPNT. Azo units in the nanowires underwent reversible trans-cis-trans isomerization upon exposure to ultraviolet or visible light, leading to changes in the radius (between ca. 6 and 8 nm) and morphology (straight or wavy) of the nanowires. SPNT is expected to provide various stimuli-responsive nanowires, which are otherwise difficult.
Shu Seki, Tsuneaki Sakurai, Masaaki Omichi, Akinori Saeki, Daisuke Sakamaki

Chapter 6. Nanowires for Renewable Energy

Abstract
Organic photovoltaics have emerged as a viable candidate for producing renewable energy. In this chapter, fabrication of fullerene nanowire by SPNT and hybridization with bulk heterojunction architecture are reviewed. Formation of fullerene nanowire itself is a remarkable milestone in SPNT, since this is the first example of molecule-based nanowires other than the previous polymer-based nanowires. Interestingly, fullerene nanowires display a more straight shape and circular cross section than those of polymers, due to the strong mechanical strength and tolerance for a swell during development process. By controlling the density and length of nanowires, [6,6]-phenyl C61 butyric acid methyl ester (PCBM) and indene-C60 bis adducts (ICBA) nanowires were found to improve the power conversion efficiencies of the corresponding poly(3-hexylthiophene) (P3HT)-based solar cell by approximately 10–20 %. Heterojunction nanowires composed of p-type polymer and n-type fullerene are formed and observed by atomic force microscopy, where each p/n component is clearly visualized by the difference in shape and radius.
Shu Seki, Tsuneaki Sakurai, Masaaki Omichi, Akinori Saeki, Daisuke Sakamaki

Chapter 7. Single-Particle Triggered Polymerization

Abstract
This chapter highlights the development of organic nanowires from small molecular organic compounds through intra-track chemical reactions using ion beam irradiation. Thin films of pentacene derivatives, 6,13-bis(triethylsilylethynyl)pentacene (TES-Pn), and 6,13-bis((triisopropylsilyl)ethynyl)pentacene (TIPS-Pn) were subjected to high-energy particle irradiation at a fluence of 108–1010 cm−2 and thereafter developed by organic solvents. This method, referred to as “Single-particle Triggered Linear Polymerization (STLiP)”, afforded the isolation of wire-shaped nanomaterials on a substrate that was visualized by atomic force microscopy and scanning electron microscopy. On the other hand, the pristine pentacene and derivative without (trialkylsilyl)ethynyl moiety did not give any nanowires. The STLiP technique serves as a versatile and easy nanofabrication tool for small molecular materials, and the resultant nanowires with high functional density are potentially usable as optical, electronic, and sensor materials.
Shu Seki, Tsuneaki Sakurai, Masaaki Omichi, Akinori Saeki, Daisuke Sakamaki
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