Masaaki Omichi

Fullerene nanowires as a versatile platform for organic electronics

The development of organic semiconducting nanowires that act as charge carrier transport pathways in flexible and lightweight nanoelectronics is a major scientific challenge. We report on the fabrication of fullerene nanowires that is universally applicable to its derivatives (pristine C60, methanofullerenes of C61 and C71, and indene C60 bis-adduct), realized by the single particle nanofabrication technique (SPNT). Nanowires with radii of 8–11 nm were formed via a chain polymerization reaction induced by a high-energy ion beam. Fabrication of a poly(3-hexylthiophene) (P3HT): [6,6]-phenyl C61 butyric acid methyl ester (PC61BM) bulk heterojunction organic photovoltaic cell including PC61BM nanowires with precisely-controlled length and density demonstrates how application of this methodology can improve the power conversion efficiency of these inverted cells. The proposed technique provides a versatile platform for the fabrication of continuous and uniform n-type fullerene nanowires towards a wide range of organic electronics applications.

Fabrication of enzyme-degradable and size-controlled protein nanowires using single particle nano-fabrication technique

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. Here we report the result of the interaction of a single high-energy charged particle with protein molecules, giving size-controlled protein nanowires with an ultra-high aspect ratio of over 1,000. Degradation of the human serum albumin nanowires was examined using trypsin. The biotinylated human serum albumin nanowires bound avidin, demonstrating the high affinity of the nanowires. Human serum albumin–avidin hybrid nanowires were also fabricated from a solid state mixture and exhibited good mechanical strength in phosphate-buffered saline. The biotinylated human serum albumin nanowires can be transformed into nanowires exhibiting a biological function such as avidin–biotinyl interactions and peroxidase activity. The present technique is a versatile platform for functionalizing the surface of any protein molecule with an extremely large surface area.

Protein nanoarrays on a highly-oriented lamellar surface

Well-aligned nanopatterns of various serum, antithrombogenic and cell adhesive proteins, such as gamma-globulin, fibrinogen, thrombomodulin, fibronectin and type I collagen, were fabricated on a highly-oriented block copolymer lamellar surface, and these bioactive protein nanoarrays will be useful in biological research.

Fabrication of Thermoresponsive Nanoactinia Tentacles by a Single Particle Nanofabrication Technique.

Nanowires that are retractable by external stimulus are the key to fabrication of nanomachines that mimick actinia tentacles in nature. A single particle nanofabrication technique (SPNT) was applied over a large area to the fabrication of retractable nanowires (nanoactinia tentacles) composed of poly(N-isopropylacrylamide) (PNIPAM) and poly(vinylpyrrolidone) (PVP), which are thermoresponsive and hydrophilic polymers. The nanowires were transformed with increasing temperature from rod-like- to globule-forms with gyration radii of ∼1.5 and ∼0.7 μm, respectively. The transformation of the nanowires was reversible and reproducible under repeated cycles of heating and cooling. The reversible transformation was driven by hydration and dehydration of PNIPAM, the thermoresponsive segments, resulting in coil-to-globule transformation of the segments. The nanoactinia tentacle systems trapped the nanoparticles as a model of living cells under thermal stimulation, and the trapping was controlled by temperature. We present herein a unique nanomachine system which can be applicable to nanoparticle filtering/sensing systems and expandable to large-area functionalization and demonstrate polymer-based nanoactuators via scaling of molecular level coil-to-globule transformation into micron-sizes.

Enhancement of the blood compatibility of dialyzer membranes by the physical adsorption of human thrombomodulin (ART-123)

ART-123 is a recombinant soluble human thrombomodulin (hTM) with excellent anticoagulant activity. We focused on improving the blood compatibility of the polysulfone-polyvinylpyrrolidone dialyzer surface by the physical adsorption of ART-123 onto the surface. The blood compatibility of the dialyzer with the hTM adsorbed membrane was evaluated by measuring the differential pressure between the arterial and the venous pressures and by blood parameters during blood circulation. The hTM adsorbed dialyzer membrane inhibited blood clot formation without heparin administration due to the anticoagulant activity of hTM for over 4 h. The physically adsorbed hTM was stable during blood circulation, and it did not affect activated clotting time, which is significant drawback of heparin administration, and blood cell counts of RBC, WBC, or platelets. The physical adsorption of hTM onto the dialyzer membrane will be a simple and safe method to prevent blood coagulation during dialysis instead of heparin administration.

Alkylated alkali lignin for compatibilizing agents of carbon fiber-reinforced plastics with polypropylene

AbstractAs an alternative to petroleum-based compatibilizing agents, we developed lignin derivatives for compatibilizing agents of carbon fiber-reinforced plastics that have thermoplasticity. In this study, alkyl chains were introduced into alkali lignin at various ratios to optimize the compatibility of the lignin derivatives with both polypropylene and carbon fiber. The interfacial shear strength between the two materials was improved from 8.2 to 17.2 MPa by mixing with the optimized lignin derivative. The value is comparable to that achieved with a typical petroleum-based compatibilizing agent (18.3 MPa).Lignin-derived compatibilizing agents were developed for polypropylene-based carbon fiber-reinforced prastics. Introduction of acyl groups to alkali lignin improved compatibility of the lignin to both carbon fiber and polypropylene while underivatized alkali lignin did not show compatibility. The interfacial shear strength between carbon fiber and polypropylene was significantly improved by addition of the lignin derivatives as compatibilizing agents.

Improvement of Blood Compatibility on Polysulfone–Polyvinylpyrrolidone Blend Films as a Model Membrane of Dialyzer by Physical Adsorption of Recombinant Soluble Human Thrombomodulin (ART-123)

ART-123 is a recombinant soluble human thrombomodulin (hTM) with potent anticoagulant activity, and is available for developing antithrombogenic surfaces by immobilization. We focused on improving blood compatibility on the dialyzer surface by the physical adsorption of ART-123 as a safe yet simple method without using chemical reagents. The physical adsorption mechanism and anticoagulant activities of adsorbed hTM on the surface of a polysulfone (PSF) membrane containing polyvinylpyrrolidone (PVP) as a model dialyzer were investigated in detail. The PVP content of the PSF–PVP films was saturated at 20 wt% after immersion in Tris-HCl buffer, even with the addition of over 20 wt% PVP. The surface morphology of the PSF–PVP films was strongly influenced by the PVP content, because PVP covered the outermost surface of the PSF–PVP films. The adsorption speed of hTM slowed dramatically with increasing PVP content up to 10 wt%, but the maximum adsorption amount of hTM onto the PSF–PVP film surface was almost the same, regardless of the PVP content. The PSF–PVP film with the physically adsorbed hTM showed higher protein C activity as compared to the PSF film, it showed excellent blood compatibility due to the protein C activity and the inhibition properties of platelet adhesion. The physical adsorption of hTM can be useful as a safe yet simple method to improve the blood compatibility of a dialyzer surface.

Fabrication of Au nanoparticles on poly(vinylpyrrolidone) nanowires exhibiting reversible frequency change of localized surface plasmon resonance

Au nanoparticles (NPs) are formed on gel nanowires (NWs) based on poly(vinylpyrrolidone) (PVP) via photoreduction in a HAuCl4-containing MeOH solution. The particle size and number density of the Au NPs increase with the photoreduction time. At a photoreduction time of 15 min, the surfaces of the PVP NWs are almost completely covered by Au NPs. The hybrid material exhibited visible optical absorption based on the localized surface plasmon resonance (LSPR) of the Au NPs. The peak LSPR absorption wavelength under dry conditions red-shifted slightly as the particle size and number density increased owing to increased coupling of the plasmonic bands of each particle. In water, the LSPR wavelength is blue-shifted compared with under dry conditions because of an increase in the interparticle distance between the Au NPs owing to the swelling of the PVP gel NWs; this causes a decrease of the plasmonic coupling of the particles. The absorption peak wavelength shifts reversibly when the hybrid NWs is alternately ex...

A Particle with High Energy: A Versatile Tool for Nanomaterials

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.

Single-Particle Triggered Polymerization

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.