Water-soluble Precursor Research Articles

水溶性な前駆体からのREPO4(RE = Y, Lu)の合成

水溶性な前駆体からのREPO4(RE = Y, Lu)の合成

Synthesis of magnesium titanate nanocrystallites from a cheap and water-soluble single source precursor

Pure nanocrystallite magnesium titanate (MgTi0 3 ) was conveniently synthesized by thermal decomposition of a cheap and water-soluble heterobimetallic single source precursor [Mg(H 2 O) 5 ] 2 [Ti 2 (O 2 ) 2 O(NC 6 H 6 -O 6 ) 2 ]·7H 2 O at low temperature. This single source precursor was obtained in high yield and in a crystalline form from the quaternary system of MgO-Ti(OC 4 H 9 ) 4 -H 2 O 2 -H 3 nta (H 3 nta = nitrilotriacetic acid) at pH 4.0. It was characterized by elemental analysis, IR spectrum, NMR, thermal gravimetric analysis and X-ray single-crystal diffraction. The morphology, microstructure, and crystallinity of the resulting MgTiO 3 materials have been characterized by transmission electron microscopy and X-ray diffraction. The TEM image of the resulting MgTi0 3 powders only consists of the nano-scale crystallites with the crystalline size of 30-100 nm.

Novel Metastable Hexagonal MoO3 Nanobelts: Synthesis, Photochromic, and Electrochromic Properties

In this work, we report the crystalline structure, morphology, and optical properties of novel metastable hexagonal phase MoO3 (h-MoO3) nanobelts prepared by a simple hydrothermal route from peroxomolybdate solution with the presence of sodium nitrate as a mineralizer. During the reaction process, NaNO3 has been proposed to influence the deoxidation, condensation, and further dehydration of the water-soluble peroxomolybdate precursor for connecting the [MoO6] octahedra with vertex sharing and edge sharing arrangements on determining the generation of metastable phase. The present work comparatively investigates the photochromic and electrochromic behaviors of the resultant hexagonal h-MoO3 nanobelts and the common thermodynamically stable orthorhombic α-MoO3 nanobelts. The performances concerning photochromism on two types of MoO3 nanobelt suspensions show that the photochemical efficiency of h-MoO3 is more excellent than that of α-MoO3 under UV light irradiation based on a remarkable coloration phenomenon. And the as-obtained h-MoO3 nanobelt coated film exhibits a steady electrochromic property in quick response to electrical impulse. Higher structure openness degree in the tunnel structure of h-MoO3, which could lead to an efficient electron−hole separation and provid larger spatial locations for cation insertion/extraction and diffusion, is suggested to be responsible for its enhanced coloration properties.

クリックペプチドの開発:アルツハイマー病関連アミロイドβペプチドを産生する刺激応答性プレカーサー

In a pathological mechanism of Alzheimer's disease (AD), amyloid beta peptide (Abeta) 1-42 plays a crucial role. However, the detailed pathological mechanism remains unclear. This elucidation is hampered by handling difficulties of Abeta1-42 due to its poor water-solubility and uncontrollable aggregation. These properties prevent reproducing neurotoxicity-related assembly events of Abeta1-42 in the experiments, leading to discrepant study outcomes. Namely, such properties of Abeta1-42 are serious obstacles to establish an experiment system that clarifies the pathological mechanism of Abeta1-42 in AD. To solve these problems, we developed "click peptide" of Abeta1-42 based on the "Omicron-acyl isopeptide method". The click peptide, which contains an Omicron-acyl instead of N-acyl residue at Gly(25)-Ser(26) of Abeta1-42, is converted to Abeta1-42 via an Omicron-to-N intramolecular acyl migration upon being triggered by pH-change (pH-click) or photo-irradiation (photo-click). The click peptide was 100-fold more water-soluble than Abeta1-42 and clearly adopted a monomeric random coil structure due to the Omicron-acyl moiety in the peptide backbone. The click peptide was quickly converted to monomer Abeta1-42 with a random coil structure under physiological conditions upon an action (click). The obtained Abeta1-42 underwent both self-assembly and conformational changes with time. Because the in situ production of intact Abeta1-42 from the water-soluble and non-aggregative precursor could overcome the handling problems of Abeta1-42, this click peptide strategy would provide a reliable experiment system to investigate the pathological functions of Abeta1-42 in AD.

Practical Considerations in the Pharmaceutical Analysis of Methyl and Hexyl Ester Derivatives of 5-Aminolevulinic Acid

Photodynamic therapy (PDT) using topical 5-aminolevulinic acid (ALA), a water-soluble precursor of the potent endogenous photosensitiser, protoporphyrin IX (PpIX), is a treatment and diagnostic tool for premalignant and malignant skin cancers. However, to improve drug delivery to deeper skin lesions, more lipophilic ALA esters have been investigated. Owing to the necessity in drug delivery research for efficient and validated assays for ALA esters in solution, this paper aims to describe optimised protocols to quantify the methyl and hexyl esters of ALA. ALA esters were derivatised using acetyl acetone and formaldehyde reagents and analysed using reversed phase HPLC. For the first time, the significance of ALA-impurities in ester samples has been highlighted. Furthermore, it was shown that for a given concentration, peak areas obtained for ALA-esters were significantly smaller than those obtained for ALA (p m-ALA (38.3%) > h-ALA (33.9%). These findings may explain why, historically, some of the benefits seen with ALA-esters using cell culture models have not been demonstrated in vivo.

Water-soluble amorphous alumina-based ceramic precursors and alumosols: Structural and chemical characterization

We examined the solid-state water-soluble amorphous precursors that are formed by partial thermal decomposition of Al(NO3)3·9H2O (aluminum nitrate nonahydrate: ANN) using Raman and FTIR and solid-state magic-angle spinning NMR spectroscopy. We also studied the species formed in the aqueous alumosols formed by dissolution of the pre-ceramic precursors using 27Al NMR spectroscopy. Species identified in the alumosols included the Al3+(H2O)6 monomer, the [AlO4Al12(OH)24(H2O)12]7+(Al13) Keggin ion, and the Al30 polycation, [Al30O8(OH)56(H2O)24]18+, as well as various other oligomers or nanoparticles containing IV-, V- and VI-coordinated Al3+ ions.

Synthesis, Characterization, and Applications of Water-Soluble Tantalum Carboxylate Precursors via a Flux Method

A novel, simple, and feasible route for synthesizing air-stable, water-soluble tantalum precursors has been developed using moisture-insensitive Ta 2 O 5 as a starting source of the Ta element, based on the conventional basic flux method. Various analytical techniques have been used to characterize the formation mechanism, purity, and thermal decomposition features of these Ta precursors including tantalum oxalate, tantalum peroxo-tartarate, and tantalum peroxo-citrate. These Ta precursor solutions have a higher Ta ion purity over 99.0 wt% and a lone shelf life. Using home-made Ta precursors, photocatalyst powders of 1 mol% Ta-doped ZnO and ferroelectric films of SrBi 2 Ta 2 O 9 on Pt/TiO 2/ SiO 2 /Si substrates have been prepared by a modified polymerizable complex (PC) route. Ta-doped ZnO powders from polymeric precursors show hexagonal wurtzite structures with uniform smaller grain sizes of 25 nm and a larger specific surface area of 32 m 2 /g. Moreover, they exhibit excellent photocatalytical activity under visible light irradiation compared with pure ZnO powders. PC-derived SrBi 2 Ta 2 O 9 films also show comparable ferroelectric and dielectric properties with those from the metalorganic decomposition method. All these qualities indicate that water-soluble Ta precursors are potential and competitive candidates for photocatalyst and ferroelectric applications.

A novel magnetic nanocomposite involving anatase titania coating on silica-modified cobalt ferrite via lower temperature hydrolysis of a water-soluble titania precursor

A high surface area magnetic nanocomposite titania/silica/cobalt ferrite photocatalyst was synthesized via controlled hydrolysis and condensation of water-soluble titanium bis-ammonium lactato dihydroxide at relatively lower temperature (<97 °C) and characterized by XRD, FTIR, HRTEM, BET, XPS and magnetism analysis. The results reveal that as-prepared photocatalyst possesses a core/shell structure involving ferrite particles sequentially coated with coherent silica layer and anatase nanocrystallites via a heterogeneous nucleation and growth mechanism. The photodegradation of the photocatalyst for methyl orange is comparative to Degussa P25 and higher than the heated samples, being tentatively attributed to the proper microstructure and isolation/immobilization functions by silica intermediate phase as well as the surface-bond hydroxyl groups.

New route to process uni-directional carbon fiber reinforced (SiC + ZrB2) matrix mini-composites

Unidirectional carbon fiber-reinforced (SiC + ZrB2) matrix mini-composites were prepared by soft solution route. In this process, the matrix materials were prepared using water-soluble precursors of colloidal silica, sucrose, zirconium oxychloride, and boric acid as sources of silica, carbon, zirconia, and boron oxide respectively. The room temperature mechanical properties were investigated and the fracture features of the composites were examined. Tensile strength of 269 ± 36 MPa and fracture energy of 0.38 ± 0.05 MJ/m3 for the mini-composite, carbothermally reduced at 1,600 °C were attributed to the fiber pull out. In spite of a composite failure mode, the composite carbothermally reduced at 1,700 °C exhibited lower mechanical properties. It showed that carbon fibers reacted with ZrO2 to form ZrC phase at 1,700 °C, formed chemical bonding, and led to a strong interface between fibers and matrix, which resulted in the degradation of mechanical properties of the mini-composites. The XRD and SEM investigations of the powders and the mini-composites revealed phase formation whereas cross-sectional microstructure indicated the uniform distribution of fibers within the matrix.

Preparation of rectangular and 2D-hexagonal mesostructured silica at neutral conditions using poly(oxyethylene) cholesteryl ethers and a water-soluble silica precursor

We report on the fabrication of hybrid organic–inorganic mesostructured materials from aqueous solutions of a series of poly(oxyethylene) cholesteryl ethers (ChEO n , where n is the number of oxyethylene units) with a water-soluble silica precursor, tetra(2-hydroxyethyl) orthosilicate (THEOS) at a neutral pH condition. ChEO 10 and ChEO 15 form rectangular and 2D-hexagonal mesostructures, respectively, as detected by Small-Angle X-ray Scattering (SAXS) measurements. On the other hand, disordered structures (showing nevertheless a correlation length) are observed with longer hydrophilic chain surfactants, such as ChEO 20, ChEO 24 and ChEO 30. Highly ordered mesostructures cannot be obtained at neutral pH when THEOS is substituted with a conventional silica precursor, tetraethyl orthosilicate (TEOS). The structural evolution from initial disordered micellar solutions is dependent on both surfactant and THEOS concentrations. It is also found that the silica mesostructures obtained from ChEO 10 and ChEO 15 templates are the same as those of the liquid crystalline phases formed in aqueous mixtures of the corresponding surfactant.

Preparation, characterization of the Ta-doped ZnO nanoparticles and their photocatalytic activity under visible-light illumination

This paper describes a novel catalyst of the Ta-doped ZnO nanocrystals prepared by a modified polymerizable complex method using the water-soluble tantalum precursor as the sources of Ta. The catalysts were characterized by means of various analytical techniques as a function of Ta content ( x=0–4 mol%) systematically. A remarkable advantage of the results was confirmed that dopant Ta enhanced the visible-light absorption of ZnO and the low-solubility tantalum doping could restrain the growth of crystal and minish the particle size. The relationship between the physicochemical property and the photocatalytic performance was discussed, and it was found that the photocatalytic activity in the photochemical degradation of methylene blue under visible-light irradiation ( λ⩾420 nm) was dependent on the contents of the dopant, which could affect the particle size, concentration of surface hydroxyl groups and active hydrogen-related defect sites, and the visible-light absorption. The highest photocatalytic activity was obtained for the 1.0 mol% Ta-doped ZnO sample.

Synthesis, characterisation and properties of α,β-poly( N-2-hydroxyethyl)- dl-aspartamide-graft-maleic anhydride precursors and their stimuli-responsive hydrogels

A family of poly(amino acid)-maleic anhydride hydrogels were designed and synthesized. Water soluble polymeric precursors were prepared by partially substituting the hydroxyl groups of the α,β-poly( N-2-hydroxyethyl)- dl-aspartamide backbone with maleic anhydride, so as to provide double bonds for crosslinking and carboxylic acid groups for pH and electric field responsiveness. Reaction conditions (reactive mixture composition and catalysis) were systematically varied in order to obtain PHEA–MA precursors with different and reliable graft-maleic anhydride levels. PHEA–MA precursors were characterised by titration, Nuclear Magnetic Resonance ( 1H NMR), Fourier-Transformed Infrared Spectroscopy (FTIR) and Size Exclusion Chromatography (SEC) for structural and molecular determination. Aqueous solutions of selected PHEA–MA precursors were subjected to gamma-irradiation at different irradiation doses and polymer to water concentrations in order to induce chemical crosslinking without the addition of crosslinking agents. The yield of crosslinking reactions was evaluated by solubility tests as well as the effect of ammonium persulphate, as assistant radical initiator for gamma crosslinking. Selected hydrogels were tested through swelling measurements to prove their pH and electric field responsiveness. Structural features of the different variants produced were related to the swelling behaviour.

Regulation of phospholipid synthesis in yeast

Phospholipid synthesis in the yeast Saccharomyces cerevisiae is a complex process that involves regulation by both genetic and biochemical mechanisms. The activity levels of phospholipid synthesis enzymes are controlled by gene expression (e.g., transcription) and by factors (lipids, water-soluble phospholipid precursors and products, and covalent modification of phosphorylation) that modulate catalysis. Phosphatidic acid, whose levels are controlled by the biochemical regulation of key phospholipid synthesis enzymes, plays a central role in the regulation of phospholipid synthesis gene expression.

“Click Peptide“: pH‐Triggered in Situ Production and Aggregation of Monomer Aβ1–42

The intense and uncontrollable self-assembling nature of amyloid beta peptide (Abeta) 1-42 is known to cause difficulties in preparing monomeric Abeta1-42; this results in irreproducible or discrepant study outcomes. Herein, we report novel features of a pH click peptide of Abeta1-42 that was designed to overcome these problems. The click peptide is a water-soluble precursor peptide of Abeta1-42 with an O-acyl isopeptide structure between the Gly25-Ser26 sequence. The click peptide adopts and retains a monomeric, random coil state under acidic conditions. Upon change to neutral pH (pH click), the click peptide converts to Abeta1-42 promptly (t(1/2) approximately 10 s) and quantitatively through an O-to-N intramolecular acyl migration. As a result of this quick and irreversible conversion, monomer Abeta1-42 with a random coil structure is produced in situ. Moreover, the oligomerization, amyloid fibril formation and conformational changes of the produced Abeta1-42 can be observed over time. This click peptide strategy should provide a reliable experimental system to investigate the pathological role of Abeta1-42 in Alzheimer's disease.

New water soluble and handy silicon precursor for synthesis of (Y,Ce,Gd)2SiO5 phosphor

We prepared a new stable and water-soluble silicon compound. The potential of this silicon reagent for synthesis of multicomponent oxide materials via a solution based method was demonstrated by preparation of a (Y0.79Ce0.01Gd0.20)2SiO5 blue emission phosphor using a polymerizable complex method. Phase composition and fluorescence properties of the prepared material were compared against a series of reference samples prepared by either conventional solid state reaction or by a polymerizable complex method employing fumed silica and TEOS as the traditional silicon reagents. The use of the new water-soluble silicon compound allowed for preparation of a single phase (Y,Ce,Gd)2SiO5 material at reduced temperatures and its fluorescence intensity was considerably higher compared to the phosphors of the same composition prepared by the other methods.

3D Hierarchical Porous TiO2 Films from Colloidal Composite Fluidic Deposition

We use a “structure director” colloidal composite to fabricate porous titanium oxide films having a hierarchical pore architecture consisting of mesopores regularly distributed in the macropore shell. The colloidal composite consists of polystyrene beads coated with (ammonium lactate)titanium dihydroxide deposited by means of a fluidic technique. The pore properties and interconnections are controlled at different length scales: a macroscale, which is imposed by the polystyrene beads; a mesoscale, which is controlled by the composition and by the thermal history of the composite; a nanometer-scale, controlled by the nanocrystal sintering in air. Our approach can be extended to a wide class of water-soluble metal oxide precursors; therefore, it opens interesting perspectives for “bottom-up” nanotechnology of functional arrays and devices.

Porous Anatase Nanoparticles with High Specific Surface Area Prepared by Miniemulsion Technique

A simple template-free approach to generate spherical porous anatase nanoparticles by combining the sol−gel process with the inverse miniemulsion technique is reported. These as-synthesized particles of about 200 nm in diameter consist of aggregated small anatase crystallites of several nanometers, thus leading to a high specific surface area of more than 300 m2·g−1, even after calcination at 400 °C. The only employed surfactant is a block copolymer (P(E/B-b-EO)), which stabilizes the aqueous droplets with the water-soluble precursor bis(2-hydroxyethyl)titanate (EGMT) in the organic phase but also leads to aggregation and pore formation inside the particles. The lower relative rates of hydrolysis and condensation compared to the commonly used titanium alkoxides allow convenient handling in miniemulsion. Here we report the effects of synthesis conditions, such as the amount of surfactant, the composition of the dispersed phase, and the reaction and calcination temperature, on the particle size, porosity, c...

Cationic poly(VCL–AETA) hydrogels and ovalbumin (OVA) release in vitro

The objective of this research is to explore the synthesis of a new family of water soluble polycationic copolymeric precursors that could be photo-crosslinked into hydrogels. The in vitro control release of ovalbumin protein (OVA) from this family of hydrogels was also studied to assess the biomedical potential of this new family polycationic hydrogels. A series of novel poly(VCL-AETA) copolymer hydrogels was fabricated in an aqueous medium via photo-induced polymerization and crosslinking of hydrophobic N-vinylcaprolactam (VCL) and hydrophilic [2-(acryloxy)ethyl]trimethylammonium chloride (AETA) monomers over a wide range of VCL to AETA feed molar ratios of 2:1, 1:1, 1:2, 1:5. N,N'-methylene bisacrylamide (MBA) was used as a crosslinker. Ovalbumin (OVA), a model antigen, was preloaded into poly(VCL-AETA) hydrogel precursors and its release profiles in pH 7.4 PBS at 37 degrees C were investigated as a function of VCL to AETA monomer feed ratios over a period of 4 weeks. The in vitro results showed that OVA initial burst and subsequent sustained releases could be controlled by 3 material parameters: the hydrophobic VCL to hydrophilic AETA monomer feed ratios, crosslinking density and hydrogel degradation rate. Thus, the hydrophobic-hydrophilic VCL-AETA hydrogel network for controlled OVA release could offer advantages over organic solvent-based single component polymer system. However, these in vitro OVA release profiles may change in an in vivo environment.

α-MoO 3 nanocrystals of controlled size on a glass substrate

A procedure to grow α-MoO 3 nanocrystals of rod and belt forms under mild conditions involved deposition onto a glass substrate via vapor transport with a water-soluble precursor. Scanning electron and transmission electron microscopic studies, selected-area electron diffraction and powder X-ray analyses indicate that these α-MoO 3 nanocrystals exhibit rod or belt forms that grow along [0 0 1] and became vertically aligned on the glass substrate. Such deposition is effective to form thin films of controllable size and density of coverage on varying the precursor concentration and the duration of deposition.

A stable water-soluble molecular precursor for the preparation of stoichiometric strontium titanate

A well-characterized strontium edta complex [Sr(H 2O)] 7[Ti(O 2)(edta)] · H 2O ( 1) was synthesized from the reaction of [Ti(H 2O)(edta)], H 2O 2 and Sr(NO 3) 2 · 6H 2O at pH 4.0–5.0 (H 4edta = ethylenediaminetetraacetic acid), which is used as a molecular precursor for the preparation of stoichiometric SrTiO 3.