Takanari Togashi

Direct and selective immobilization of proteins by means of an inorganic material-binding peptide: discussion on functionalization in the elongation to material-binding peptide.

Using an artificial peptide library, we have identified a peptide with affinity for ZnO materials that could be used to selectively accumulate ZnO particles on polypropylene-gold plates. In this study, we fused recombinant green fluorescent protein (GFP) with this ZnO-binding peptide (ZnOBP) and then selectively immobilized the fused protein on ZnO particles. We determined an appropriate condition for selective immobilization of recombinant GFP, and the ZnO-binding function of ZnOBP-fused GFP was examined by elongating the ZnOBP tag from a single amino acid to the intact sequence. The fusion of ZnOBP with GFP enabled specific adsorption of GFP on ZnO substrates in an appropriate solution, and thermodynamic studies showed a predominantly enthalpy-dependent electrostatic interaction between ZnOBP and the ZnO surface. The ZnOBPs binding affinity for the ZnO surface increased first in terms of material selectivity and then in terms of high affinity as the GFP-fused peptide was elongated from a single amino acid to intact ZnOBP. We concluded that the enthalpy-dependent interaction between ZnOBP and ZnO was influenced by the presence of not only charged amino acids but also their surrounding residues in the ZnOBP sequence.

Nanoparticle chemisorption printing technique for conductive silver patterning with submicron resolution

Silver nanocolloid, a dense suspension of ligand-encapsulated silver nanoparticles, is an important material for printing-based device production technologies. However, printed conductive patterns of sufficiently high quality and resolution for industrial products have not yet been achieved, as the use of conventional printing techniques is severely limiting. Here we report a printing technique to manufacture ultrafine conductive patterns utilizing the exclusive chemisorption phenomenon of weakly encapsulated silver nanoparticles on a photoactivated surface. The process includes masked irradiation of vacuum ultraviolet light on an amorphous perfluorinated polymer layer to photoactivate the surface with pendant carboxylate groups, and subsequent coating of alkylamine-encapsulated silver nanocolloids, which causes amine–carboxylate conversion to trigger the spontaneous formation of a self-fused solid silver layer. The technique can produce silver patterns of submicron fineness adhered strongly to substrates, thus enabling manufacture of flexible transparent conductive sheets. This printing technique could replace conventional vacuum- and photolithography-based device processing.

High Affinity Anti-inorganic Material Antibody Generation by Integrating Graft and Evolution Technologies POTENTIAL OF ANTIBODIES AS BIOINTERFACE MOLECULES

Recent advances in molecular evolution technology enabled us to identify peptides and antibodies with affinity for inorganic materials. In the field of nanotechnology, the use of the functional peptides and antibodies should aid the construction of interface molecules designed to spontaneously link different nanomaterials; however, few material-binding antibodies, which have much higher affinity than short peptides, have been identified. Here, we generated high affinity antibodies from material-binding peptides by integrating peptide-grafting and phage-display techniques. A material-binding peptide sequence was first grafted into an appropriate loop of the complementarity determining region (CDR) of a camel-type single variable antibody fragment to create a low affinity material-binding antibody. Application of a combinatorial library approach to another CDR loop in the low affinity antibody then clearly and steadily promoted affinity for a specific material surface. Thermodynamic analysis demonstrated that the enthalpy synergistic effect from grafted and selected CDR loops drastically increased the affinity for material surface, indicating the potential of antibody scaffold for creating high affinity small interface units. We show the availability of the construction of antibodies by integrating graft and evolution technology for various inorganic materials and the potential of high affinity material-binding antibodies in biointerface applications.

Continuous hydrothermal synthesis of 3,4-dihydroxyhydrocinnamic acid-modified magnetite nanoparticles with stealth-functionality against immunological response

In our study, water dispersible magnetite (Fe3O4) nanoparticles were continuously synthesized in water under high temperature and pressure in the presence of 3,4-dihydroxyhydrocinnamic acid (DHCA) by using a tubular flow reactor. The prepared Fe3O4 nanoparticles were well dispersed in water because the surfaces of the nanoparticles were fully covered by DHCA molecules and the –COOH groups in the DHCA molecules were exposed to the surrounding water. Cytokines such as IL-12 and TNF-α were not produced from the dendritic cells of mice by co-incubation with our synthesized Fe3O4. This indicates that the synthesized Fe3O4 had no immune stimulating property for the dendritic cells of the mouse. Therefore, our synthesized Fe3O4 nanoparticles are suitable for biological applications such as magnetic resonance imaging contrast agents and carriers for drug and gene delivery, and in areas such as hyperthermia therapy for cancer, biosensors, and tissue engineering.

Molecular Nanostamp Based on One-Dimensional Porphyrin Polymers

Surface design with unique functional molecules by a convenient one-pot treatment is an attractive project for the creation of smart molecular devices. We have employed a silane coupling reaction of porphyrin derivatives that form one-dimensional polymer wires on substrates. Our simple one-pot treatment of a substrate with porphyrin has successfully achieved the construction of nanoscale bamboo shoot structures. The nanoscale bamboo shoots on the substrates were characterized by atomic force microscopy (AFM), UV-vis spectra, and X-ray diffraction (XRD) measurements. The uneven and rigid nanoscale structure has been used as a stamp for constructing bamboo shoot structures of fullerene.

Largely enhanced photocurrent via gap-mode plasmon resonance by a nanocomposite layer of silver nanoparticles and porphyrin derivatives fabricated on an electrode

Photocurrent generation efficiency via the photoactive dyes, porphyrins, was strongly enhanced by construction of a nanocomposite structure, which consists of an undercoat layer of (3-mercaptopropyl)trimethoxysilane and densely and homogeneously attached silver nanoparticles on an electrode. The employed 5 -(4-carboxyphenyl)-10,15,20-triphenylporphyrins, 1, were embedded on the silver nanoparticle surface through their carboxylate moiety. The photo-absorption of 1 was significantly influenced by normal and gap-mode plasmon bands. The photocurrent of the nanocomposite structure was more strongly enhanced via the Q band excitation of 1, overlapped with the gap-mode plasmon band in the absorption wavelength range, and also showed stable photocurrent.

Self-Assembly and Reassembly Phenomena of Organic–Inorganic Hybrid Nanocrystals in Highly Ordered Nanocrystalline Multi/Monolayer

Uniform and highly ordered nanocrystalline multilayers were obtained after tetrahydrofuran annealing of pre-assembled nanocrystals on the substrate surfaces. As a result of the rearrangement process during solvent annealing, cerium oxide hybrid nanocrystals were correctly positioned in the nanocrystalline film layers because of high carrier ability and the high affinity of the solvent to the nanocrystals. It was also found that solvent annealing had almost no effect on the nanocrystalline monolayer macroscopically, indicating that nanocrystals chemisorbed on the modified substrate surface did not move freely as compared with nanocrystals on top of the pre-assembled nanocrystals. A sufficiently highly ordered nanocrystalline structure was self-assembled in the concentrated solvent and thus printed to such a sticky surface from a face-down configuration that prevented the random deposition of nanocrystals, resulting in the uniform and ordered nanocrystalline monolayer of macroscopic size.

Dual‐functional surfactant‐templated strategy for synthesis of an in‐situ N2‐intercalated mesoporous WO3 photoanode for efficient visible‐light‐driven water oxidation

N2 -Intercalated crystalline mesoporous tungsten trioxide (WO3 ) was synthesized by a thermal decomposition technique with dodecylamine (DDA) as a surfactant template with a dual role as an N-atom source for N2 intercalation, alongside its conventional structure-directing role (by micelle formation) to induce a mesoporous structure. N2 physisorption analysis showed that the specific surface area (57.3 m2  g-1 ) of WO3 templated with DDA (WO3 -DDA) is 2.3 times higher than that of 24.5 m2  g-1 for WO3 prepared without DDA (WO3 -bulk), due to the mesoporous structure of WO3 -DDA. The Raman and X-ray photoelectron spectra of WO3 -DDA indicated intercalation of N2 into the WO3 lattice above 450 °C. The UV/Vis diffuse-reflectance spectra exhibited a significant shift of the absorption edge by 28 nm, from 459 nm (2.70 eV) to 487 nm (2.54 eV), due to N2 intercalation. This could be explained by the bandgap narrowing of WO3 -DDA by formation of a new intermediate N 2p orbital between the conduction and valance bands of WO3 . A WO3 -DDA-coated indium tin oxide (ITO) electrode calcined at 450 °C generated a photoanodic current under visible-light irradiation below 490 nm due to photoelectrochemical water oxidation, as opposed to below 470 nm for ITO/WO3 -bulk. The incident photon-to-current conversion efficiency (IPCE=24.5 %) at 420 nm and 0.5 V versus Ag/AgCl was higher than that of 2.5 % for ITO/WO3 -bulk by one order of magnitude due to N2 intercalation and the mesoporous structure of WO3 -DDA.

Grain-Boundary-Free Super-Proton Conduction of a Solution-Processed Prussian-Blue Nanoparticle Film

A porous crystal family has been explored as alternatives of Nafion films exhibiting super-proton conductivities of ≥10-2  S cm-1 . Here, the proton-conduction natures of a solution-processed film of nanoparticles (NPs) have been studied and compared to those of a Nafion film. A mono-particle film of Prussian-blue NPs is spontaneously formed on a self-assembled monolayer substrate by a one-step solution process. A low-temperature heating process of the densely packed, pinhole-free mono-particle NP film enables a maximum 105 -fold enhancement of proton conductivity, reaching ca. 10-1  S cm-1 . The apparent highest conductivity, compared to previously reported data of the porous crystal family, remains constant against humidity changes by an improved water-retention ability of the film. In our proposed mechanism, the high-performing solution-processed NP film suggests that heating leads to the self-restoration of hydrogen-bonding networks throughout their innumerable grain boundaries.

Supercritical Hydrothermal Synthesis

This chapter describes specific features of a supercritical hydrothermal synthesis method. First, the some characteristic properties of supercritical water are summarized, and then the mechanism of supercritical hydrothermal synthesis is explained. Higher reaction rate and lower solubility are the key factors to synthesize nanosize crystals in a short reaction time. The flow reaction system to achieve rapid heating is explained. Some commercialized process is introduced. This method is useful to synthesize organic molecule modified nanoparticles (NPs). Since the organic molecules and metal–salt aqueous solutions are miscible under the supercritical state, and water molecule works as an acid/base catalyst for the reactions, organic–inorganic conjugate NPs can be synthesized under the condition. The mechanism of the conjugate forming reaction is explained. NPs’ superlattice structure and bioconjugate materials are also formed under the condition. The hybrid NPs show high affinity for the organic solvent or the polymer matrix, which leads to fabricate the organic–inorganic hybrid nanomaterials with the trade-off function (superhybrid nanomaterials). One of the applications is to fabricate a heat-conductive flexible hybrid-polymer sheet. By the surface modification of BN particles by supercritical method, affinity of BN and polymers could be improved so that high BN content of hybrid materials, thus high thermal conductivity materials, could be synthesized.