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ABSTRACT: The assembly of metal oxide nanoparticles (NPs) on a biomolecular template by a one-pot hydrothermal synthesis method is achieved
for the first time. Magnetite (Fe3O4) nanoneedles (length: ~100nm; width: ~10nm) were assembled on cyclic-diphenylalanine (cFF) nanorods (length: 2–10μm; width:
200nm). The Fe3O4 nanoneedles and cFF nanorods were simultaneously synthesized from FeSO4 and l-phenylalanine by hydrothermal synthesis (220°C and 22MPa), respectively. The samples were analyzed by powder X-ray diffraction
(XRD), Fourier transform infrared spectroscopy (IR), transmission electron microscopy (TEM), and superconducting quantum interference
device (SQUID) magnetometry. Experimental results indicate that Fe3O4 nanoneedles were assembled on cFF nanorods during the hydrothermal reaction. The composite contained 3.3wt% Fe3O4 nanoneedles without any loss of the original magnetic properties of Fe3O4.
KeywordsSelf-assembly–Magnetite–Peptide–Hydrothermal–One-pot synthesis
Journal of Nanoparticle Research 04/2012; 13(9):3991-3999. · 3.29 Impact Factor
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ABSTRACT: Decanoic acid self-assembled monolayer (SAM) in the quasi-crystalline state was prepared on the surface of the cubic CeO2 nanoparticles (6.5±1.1nm) by hydrothermal synthesis. The purification method to obtain quasi-crystalline SAM without residual
(free) decanoic acid was developed. The SAM was carefully washed (purified) and characterized carefully by FT-IR, TG, DSC,
and NMR. The obtained results showed that good agreement with the property of the dry state SAM. The solution state properties
of the SAM were also examined by the CeO2 nanoparticles. It turned out that the quasi-crystalline SAM could be swollen by its good solvents, cyclohexane, and chloroform;
however, the quasi-crystalline SAM showed that a size exclusion effect to the solvent, trans-decalin. In addition, it turned out that the molecular motion of the decanoic acids in the SAM was highly restricted even
in the swollen state depending on the distance from the grafting point to the CeO2 surface. The strong osmosis was also observed. The solvent molecules were not easily released from the SAM even after the
solvent molecules outside of the SAM were frozen.
KeywordsSelf-assembled monolayer-Nanoparticle-Polymer brush-Surface chemistry-Thin films-Supercritical fluids
Journal of Nanoparticle Research 04/2012; 12(7):2567-2578. · 3.29 Impact Factor
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ABSTRACT: Continuous production of highly crystalline ZnO nanorods by supercritical hydrothermal synthesis was reported in this article.
Zinc nitrate aqueous solution was pressurized to 30MPa at room temperature and rapidly heated to 673K by mixing with supercritical
water and then fed into a tubular reactor. Residence time is about 10s. Production of ZnO nanorod particles with uniform
particle size distribution showed a strong ultraviolet light emission at room temperature. This article also reported in-situ
surface modification of ZnO nanorods with organic reagents by the supercritical hydrothermal synthesis.
Journal of Materials Science 04/2012; 43(7):2393-2396. · 2.02 Impact Factor
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ABSTRACT: ITO nanoparticles were synthesized hydrothermally and surface modified in supercritical water using a continuous flow reaction system. The organic modification of the nanoparticles converted the surface from hydrophilic to hydrophobic, making the modified nanoparticles easily dispersible in organic solvent. The addition of a surface modifier into the reaction system impacted the crystal growth and particle size as well as dispersion. The particle size was 18 nm. Highly crystalline cubic ITO with a narrow particle size distribution was obtained. The advantages of short reaction time and the use of a continuous reaction system make this method suitable for industrial scale synthesis.
ACS Applied Materials & Interfaces 12/2011; 4(1):351-4. · 4.53 Impact Factor
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ABSTRACT: We have experimentally carried out a Rayleigh scattering study of a high refractive index TiO(2) nanohybrid polymer. By employing the Rayleigh scattering technique with at least three different wavelengths, we can obtain the Rayleigh ratio of the TiO(2) nanohybrid polymer at each utilized wavelength. These measured Rayleigh ratios are then used to estimate the size of the nanoparticle and determine the number of nanoparticles per unit volume or particle density. Furthermore, this technique can be used to evaluate the dominant size of nanoparticles in the nanohybrid polymer mainly contributed to Rayleigh scattering.
Physical Chemistry Chemical Physics 03/2011; 13(10):4470-5. · 3.57 Impact Factor
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ABSTRACT: The solution-state property of three-dimensional self-assembled monolayers (3D SAMs) on CeO2 nanoparticles (NPs) has been found to seriously affect dispersion of the NPs. The chain length and solvent-dependent changes in the properties of SAMs were investigated by using various n-alkanoic acid SAMs on CeO2 NPs and various nonpolar organic solvents. NMR and DSC were employed to analyze solution-state behavior of the 3D SAMs. A scaling approach on the chain length and the grafting density of the SAMs could characterize the behavior of SAMs in solution: whether the SAMs were swelling or not. The solvent quality (good or poor) for SAMs was also important for the swelling of the SAMs. In addition, the volume of the solvent molecule was also a critical parameter. The swollen SAMs could provide effective repulsion to overcome van der Waals attraction between NPs. Combining our scaling analysis on solution-state behavior of the 3D SAMs and the experimental results of dispersion of the CeO2 NPs, a criterion for the 3D SAMs to obtain well-dispersed surface-modified NPs was proposed.
02/2011;
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ABSTRACT: Magnetic nanoparticles (MNPs) have many potential biomedical applications. Improvements in their magnetic properties and solubility are necessary for these applications to realize their full potential. In this study, MNPs in the form of raspberry-like magnetite (Fe(3)O(4)) nanoparticle clusters, consisting of tiny Fe(3)O(4) particles with a diameter of approximately 20 nm, were prepared under hydrothermal conditions at 200 °C in the presence of 3,4-dihydroxyhydroxysinnamic acid (DHCA). The primary particles were connected by DHCA molecules to form the clusters, which were well dispersed in water media because a COOH group from DHCA appeared on their surfaces. The cluster size could be tuned from 50 to 400 nm without changing the primary particle size by controlling the reaction time. Therefore, all prepared clusters displayed superparamagnetic properties at room temperature. In addition, the sensitivity of Fe(3)O(4) to an external magnetic field could also be controlled by the cluster size.
Dalton Transactions 02/2011; 40(5):1073-8. · 3.84 Impact Factor
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ABSTRACT: Herein we demonstrate the extra-low-temperature oxygen storage capacity (OSC) of cerium oxide nanocrystals with cubic (100) facets. A considerable OSC occurs at 150 °C without active species loading. This temperature is 250 °C lower than that of irregularly shaped cerium oxide. This result indicates that cubic (100) facets of cerium oxide have the characteristics to be a superior low-temperature catalyst.
Nano Letters 02/2011; 11(2):361-4. · 13.20 Impact Factor
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ABSTRACT: Recently, a zinc oxide (ZnO)-binding peptide (ZnOBP) has been identified and has been used to assist the synthesis of unique crystalline ZnO particles. We analyzed the influence of ZnOBP on the crystal growth of ZnO structures formed from zinc hydroxide. The addition of ZnOBP in the hydrothermal synthesis of ZnO suppressed [0001] crystal growth in the ZnO particles, indicating that the specificity of the material-binding peptide for specific inorganic crystal faces controlled the crystal growth. Furthermore, the dipeptides with a partial sequence of ZnO-binding "hot spot" in ZnOBP were used to synthesize ZnO particles, and we found that the presence of these dipeptides more strictly suppressed (0001) growth in ZnO crystals than did the complete ZnOBP sequence. These results demonstrate the applicability of dipeptides selected from material-binding peptides to control inorganic crystal growth.
Journal of Bioscience and Bioengineering 10/2010; 111(2):140-5. · 1.79 Impact Factor
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ABSTRACT: Titanium dioxide (TiO2, anatase) nanocyrstals tha can be transparently (perfectly) dispersed in several organic solvents were synthesized by organic-ligand-assisted hydrothermal synthesis. To analyze the dispersion behavior of surface-modified nanocrystals from the surface of the surface-modified nanocrystals, three types of surface-modified TiO2 nanocrystals were prepared. Depending on the surface nature of the surface-modified TiO2 nanocrystals, the nanocrystals showed different dispersion behaviors in organic solvents. In particular, the dispersion of surface-modified TiO2 nanocrystals with carboxylic acid terminated surface modifier (TiO2—COOH) varied strongly with changing solvent species. We investigated the dispersity of TiO2—COOH in typical organic solvents using dynamic light scattering (DLS) measurements. One of the three-dimensional solubility parameters, namely, the Hansen solubility parameter, provided detailed information on the mechanism of the dispersion of TiO2—COOH. Because of the carboxylic acid groups exhibited on the surface of the titania nanocrystals, the dispersion of TiO2—COOH was very much affected by the hydrogen-bonding ability of the solvent. The hydrogen-donating/-accepting ability adequately described the dispersion of TiO2—COOH in organic solvents.
09/2010;
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ABSTRACT: Peptides with both an affinity for ZnO and the ability to generate ZnO nanoparticles have attracted attention for the self-assembly and templating of nanoscale building blocks under ambient conditions with compositional uniformity. In this study, we have analyzed the specific binding sites of the ZnO-binding peptide, EAHVMHKVAPRP, which was identified using a phage display peptide library. The peptide binding assay against ZnO nanoparticles was performed using peptides synthesized on a cellulose membrane using the spot method. Using randomized rotation of amino acids in the ZnO-binding peptide, 125 spot-synthesized peptides were assayed. The peptide binding activity against ZnO nanoparticles varied greatly. This indicates that ZnO binding does not depend on total hydrophobicity or other physical parameters of these peptides, but rather that ZnO recognizes the specific amino acid alignment of these peptides. In addition, several peptides were found to show higher binding ability compared with that of the original peptides. Identification of important binding sites in the EAHVMHKVAPRP peptide was investigated by shortened, stepwise sequence from both termini. Interestingly, two ZnO-binding sites were found as 6-mer peptides: HVMHKV and HKVAPR. The peptides identified by amino acid substitution of HKVAPR were found to show high affinity and specificity for ZnO nanoparticles.
Biotechnology and Bioengineering 08/2010; 106(6):845-51. · 3.95 Impact Factor
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ABSTRACT: We have found that the concentrated poly(methyl methacrylate) (PMMA) brush showed the very good nanoparticles (NPs) repellency in its good solvent, e.g. tetrahydrofuran (THF). Whereas the oil- and hydro-phobic (fluorinated), hydrophobic and hydrophilic surfaces adsorbed a lot of NPs. The repellency of NPs did not depend on the surface nature of the NPs. Preparing absorption free columns for size exclusion chromatography (SEC) may enable us to separate quantum dots (QDs) and NPs according to their size. By installing the concentrated PMMA brush into silica monolith columns, we tried to achieve SEC of QDs and NPs. The concentrated PMMA brush immobilized silica monolith columns were prepared by surface initiated atom transfer polymerization of MMA. As a result, we have succeeded in separating QDs according to their size. This SEC system may be advantageous because it can be used in good solvents of the brush regardless of the stability of the surface modifier layer on the NPs.
Nanoscale 08/2010; 2(8):1467-73. · 5.91 Impact Factor
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ABSTRACT: Colloidal CeO2 nanoparticles (HNPs) stabilized with a decanoic fatty acid self-assembled monolayer (SAM) (decHNPs) showed very good dispersibility, i.e., perfect dispersion in cyclohexane up to 20 wt%. However, the HNPs stabilized with a dodecanoic acid SAM (dodHNPs) did not show good dispersion, i.e., at most 0.2 wt%. Interestingly, when we mixed equal portions of 5 wt% decHNPs in cyclohexane and 2 wt% dodHNPs in cyclohexane, the mixture showed much better dispersion than 1 wt% of dodHNPs in cyclohexane. This might indicate that the size and size distribution of the major components of the HNP solution are the most dominant factors for determining the dispersibility of HNPs in solution.
Nanoscale 05/2010; 2(5):689-93. · 5.91 Impact Factor
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ABSTRACT: The stability of atomic intercalated boron nitride K4 crystal structures, XBN (X=H, Li, Be, B, C, N, O, F, Na, Mg, Al, Si, P, S, Cl, K, Ca, Ga, Ge, As, Se, Br, Rb or Sr) is evaluated by the geometric optimization and frozen phonon calculations based on the first principles calculations. NaBN, MgBN, GaBN, FBN and ClBN are found to be stable. NaBN, GaBN, FBN and ClBN are metallic, whereas MgBN is semiconducting. Comment: Under reviewing process of Physical Review B same with "Properties of atomic intercalated carbon K4 type crystals" (arXiv:0911.1526) which is authorized by Masahiro Itoh, Seiichi Takami, Yoshiyuki Kawazoe, and Tadafumi Adschiri
04/2010;
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ABSTRACT: 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.
Journal of Biological Chemistry 03/2010; 285(10):7784-93. · 4.77 Impact Factor
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ABSTRACT: 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.
Journal of Biological Chemistry 03/2010; 285(10):7784-7793. · 4.77 Impact Factor
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ABSTRACT: Sufficiently high-coverage monolayer structures of cerium oxide nanocrystals modified with decanoic acid, with sizes of 9 nm, were fabricated on the surface using a silicon substrate modified with 3,4-dihydroxyhydrocinnamic acid where catechol group lied at the top. By doing this, no further pretreatment for the modified nanocrystals is required to fix them chemically on the substrate. Selective adhesion between nanocyrstals and the substrate for the two-dimensional assembly can be attributed to the chemical bonding formed by on-site ligand exchange on the catechol-terminated substrate. Catechol-carboxyl group ligand exchange results in high-efficient due to higher affinity of catechol to metal oxide surfaces. This affinity difference enabled to perform this on-site ligand exchange even at room temperature.
01/2010;
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ABSTRACT: Ceria (CeO2) nanocyrstals which could be transparently dispersed in several organic solvents were synthesized by organic-ligand-assisted hydrothermal synthesis. We have studied the dispersity of the nanocrystals into typical organic solvents using dynamic light scattering (DLS) measurement. The mean diameter of the dispersant (the nanocrystals’ cluster) varied with changing the solvent species. When the solubility parameter (SP) values of the solvent and the modifier were comparable to each other, the nanocrystals tended to disperse in the solvent with the initial particle size. One of the three-dimensional SPs, i.e., the Hansen solubility parameters, brought more detailed understanding of the mechanism of the dispersion of the surface modified nanocrystals. Because of the dense modifier layer on the surface of the ceria nanocrystals, the hydrogen bonding ability of the solvent was not the dominant factor to determine dispersion of the surface modified nanocrystals. The dispersion and polar factors of the Hansen SPs could describe the ideal condition of perfect dispersion of the surface modified CeO2 nanocrystals.
12/2009;
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ABSTRACT: Tailor-made surface-modified metal oxide nanocrystals enable various applications including medical, electronic, magnetic, and photovoltaic devices. Both the synthesis and application of surface-modified metal oxide nanocrystals rely on the interaction between organic molecules and the surface of metal oxides. From this viewpoint, we have focused on the synthesis of metal oxide nanocrystals using supercritical water in the presence of organic molecules as a surface modifier. Here, we describe the use of dicarboxylic acids with various chain lengths as the modifiers of CeO2 nanocrystals. The morphology and displayed crystallite plane of CeO2 nanocrystals could be controlled by the length of dicarboxylic acids. Long dicarboxylic acids produced cuboctahedral or cubic CeO2 nanocrystals, possibly because of the decreased growth rate of the {200} plane. The growth mechanism of the CeO2 nanocrystals is discussed in detail. Furthermore, dicarboxylic acids on the surface of the CeO2 nanocrystals changed the isoelectric point of the nanocrystals by displaying carboxyl groups. As a result, we have succeeded in synthesizing water-soluble CeO2 nanocrystals with various morphologies using dicarboxylic acids.
12/2009;
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Nozomi Yokoo,
Takanari Togashi,
Mitsuo Umetsu,
Kouhei Tsumoto,
Takamitsu Hattori,
Takeshi Nakanishi,
Satoshi Ohara,
Seiichi Takami,
Takashi Naka,
Hiroya Abe,
Izumi Kumagai, Tadafumi Adschiri
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ABSTRACT: 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 ZnOBP's 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.
The Journal of Physical Chemistry B 12/2009; 114(1):480-6. · 3.70 Impact Factor
