Enhanced Photocatalysis of Electrically Polarized Titania Nanosheets.

Titania (TiO2) nanosheets are crystals with controlled, highly ordered structures that improve the functionality of conventional TiO2 nanoparticles. Various surface modification methods have been studied to enhance the effectiveness of these materials as photocatalysts. Surface modifications using electrical polarization have attracted considerable attention in recent years because they can improve the function of titania without changing its composition. However, the combination of facet engineering and electrical polarization has not been shown to improve the functionality of TiO2 nanosheets. In the present study, the dye-degradation performance of polarized TiO2 nanosheets was evaluated. TiO2 nanosheets with a F/Ti ratio of 0.3 were synthesized via a hydrothermal method. The crystal morphology and structure were evaluated using transmission electron microscopy and X-ray diffraction. Then, electrical polarization was performed under a DC electric field of 300 V at 300 °C. The polarized material was evaluated using thermally stimulated current measurements. A dye-degradation assay was performed using a methylene blue solution under ultraviolet irradiation. The polarized TiO2 nanosheets exhibited a dense surface charge and accelerated decolorization. These results indicate that electrical polarization can be used to enhance the photocatalytic activity of TiO2.

Development of TiO2 Nanosheets with High Dye Degradation Performance by Regulating Crystal Growth.

TiO2 nanosheets have been studied as photocatalysts in various fields, and their performance has been actively improved. Herein, we prepared titania nanosheets with a smaller size than those reported previously with a side length of 29 nm and investigated their photocatalytic activity. (NH4)2TiF6 and Ti(OBu)4 were used as raw materials, and the F/Ti ratio was varied in the range of 0.3 to 2.0 to produce a series of samples with different side lengths by hydrothermal synthesis. A reduction in the F/Ti ratio led to the reduced size of the titanium nanosheets. The photocatalytic activity of each sample was evaluated through the degradation of methylene blue (MB) under ultraviolet (UV) irradiation (365 nm, 2.5 mW/cm2). UV irradiation promoted the decomposition of MB, and the highest degradation efficiency was achieved using titania nanosheets prepared with a F/Ti ratio of 0.3. The high catalytic activity can be attributed to the increase in the surface area due to size reduction. The ratio of the {001} surface exposed on the titania nanosheet also affected the photocatalytic activity; it resulted in increased activation of the reaction. This study demonstrates that further activation of the photocatalytic activity can be achieved by adjusting the size of titania nanosheets.

Ferromagnetism and exchange bias in compressed ilmenite-hematite solid solution as a source of planetary magnetic anomalies.

We propose a compressed ilmenite-hematite solid solution as a new potential source of Earth's magnetic anomalies. The 0.5FeTiO3·0.5Fe2O3 solid solution compressed by collision synthesis with super-high-energy ball milling showed a decrease in molar volume of approximately 1.8%. Consequently, the sample showed a saturation magnetization of 1.5 ampere square meter per kilogram (Am2/kg) at 300 kelvin, a Curie temperature of 990 kelvin, and a magnetic exchange bias below 100 kelvin, e.g., 1.7 × 105 ampere per meter at 60 kelvin. Ilmenite-hematite solid solutions are common mineral systems in most mafic igneous and metamorphic rocks, and the compressive force in the rocks is generated by the high pressure in the upper mantle or by shock events with high pressure such as the collision of these rocks with meteorites. Therefore, we consider that the compressed ilmenite-hematite solid solution is an additional candidate source of other planetary magnetic anomalies including those in the Moon and Earth.

Emergence of ferromagnetism due to charge transfer in compressed ilmenite powder using super-high-energy ball milling.

Ilmenite, FeTiO3, is a common mineral in nature, existing as an accessory phase in the most basic igneous and metamorphic rocks, for example, it is derived from the upper mantle. Therefore, an understanding of the high-pressure physics of FeTiO3 is of fundamental importance in the study of rock magnetization. Here, we provide experimental evidence of lattice compression of FeTiO3 powder using super-high-energy ball milling, enabling the very high collision energy of 420 times gravitational acceleration. A sample obtained as an ilmenite- hematite 0.5FeTiO3·0.5Fe2O3 solid solution showed a decrease in molar volume of approximately 1.8%. Consequently, the oxidation state in FeTiO3 powder was changed into almost Fe3+Ti3+, corresponding to 87% Fe3+ of the total Fe for FeTiO3, resulting in the emergence of ferromagnetism. This new ferromagnetic behaviour is of crucial importance in the study of rock magnetization which is used to interpret historical fluctuations in geomagnetism. In addition, the super-high-energy ball mill can be used to control a range of charge and spin states in transition metal oxides with high pressure.

Soft X-ray-Enhanced Reactive Oxygen Species Generation in Mesoporous Titanium Peroxide and the Application in Tumor Synergistic Therapy.

Mesoporous titanium peroxide TiOx nanospheres with a high surface area are synthesized for the application of an advanced drug system. The mesoporous TiOx nanospheres have a high specific surface area of 681.89 m2/g and suitable pore size (∼3 nm) that can effectively upload doxorubicin (DOX) and possesses a high drug storage capacity of 146.08%. They show a distinct ability to produce reactive oxygen species (ROS) in response to X-ray irradiation, which can effectively improve the radiotherapy in tumor treatment using the lung cancer cell line. The ROS generation of TiOx is more than ten-fold higher than that of TiO2. No apparent toxicity is found for the TiOx material itself without X-ray irradiation. In vitro and in vivo experiments show that TiOx/DOX nanodrugs significantly enhance cytotoxicity in response to X-ray irradiation. CCK8 assays display that the TiOx/DOX nanodrug has higher cancer treatment efficiency in response to X-ray irradiation because of the synergistic effect of chemotherapy and generation of ROS. In the in vivo experiments using lung cancer tumor-bearing mice model, the tumor inhibition rate in the TiOx/DOX + X-ray group increased by 90.4% compared to the untreated control group, showing a good synergistic chemo-radiotherapy effect in tumor treatment.

Enhanced Antibacterial Property of Facet-Engineered TiO2 Nanosheet in Presence and Absence of Ultraviolet Irradiation.

Titania (TiO2) has attracted much attention recently for reducing bacterial diseases by the generation of reactive oxygen species (ROS) under UV irradiation. However, demand for higher photocatalytic activity due to higher recombination of electron and hole remains. The aims of this study were to make titania with higher antibacterial property and show the mechanisms of the bactericidal effect. In this study, we hydrothermally synthesized TiO2 nanosheets (NS) with highly-oriented structures. Samples were divided into five groups, depending on the fluorine/titanium ratio in the raw material, namely NS1.0, NS1.2, NS1.5, NS1.8, and NS2.0. Facet ratio and nanosheet size increased with an increase of fluorine/titanium ratio. The photocatalytic activity of TiO2 nanosheet was assessed by the generation of ROS. Hydroxyl radicals and superoxides were generated efficiently by ultraviolet light irradiation on NS1.5 and NS1.0, respectively. Antibacterial activity against Streptococcus mutans was assessed in the presence and absence of UV irradiation; NS1.0 showed superior antibacterial properties compared to commercially available TiO2 nanoparticles, under both conditions, due to the oxidation of intracellular components and cell membrane. These results together suggested TiO2 nanosheet induced bacterial cell death by oxidation, and TiO2 facet engineering resulted in enhancement of both photocatalytic and antibacterial activities of TiO2.

Titanium peroxide nanoparticles enhanced cytotoxic effects of X-ray irradiation against pancreatic cancer model through reactive oxygen species generation in vitro and in vivo.

BACKGROUND: Biological applications of nanoparticles are rapidly increasing, which introduces new possibilities to improve the efficacy of radiotherapy. Here, we synthesized titanium peroxide nanoparticles (TiOxNPs) and investigated their efficacy as novel agents that can potently enhance the effects of radiation in the treatment of pancreatic cancer. METHODS: TiOxNPs and polyacrylic acid-modified TiOxNPs (PAA-TiOxNPs) were synthesized from anatase-type titanium dioxide nanoparticles (TiO2NPs). The size and morphology of the PAA-TiOxNPs was evaluated using transmission electron microscopy and dynamic light scattering. The crystalline structures of the TiO2NPs and PAA-TiOxNPs with and without X-ray irradiation were analyzed using X-ray absorption. The ability of TiOxNPs and PAA-TiOxNPs to produce reactive oxygen species in response to X-ray irradiation was evaluated in a cell-free system and confirmed by flow cytometric analysis in vitro. DNA damage after X-ray exposure with or without PAA-TiOxNPs was assessed by immunohistochemical analysis of γ-H2AX foci formation in vitro and in vivo. Cytotoxicity was evaluated by a colony forming assay in vitro. Xenografts were prepared using human pancreatic cancer MIAPaCa-2 cells and used to evaluate the inhibition of tumor growth caused by X-ray exposure, PAA-TiOxNPs, and the combination of the two. RESULTS: The core structures of the PAA-TiOxNPs were found to be of the anatase type. The TiOxNPs and PAA-TiOxNPs showed a distinct ability to produce hydroxyl radicals in response to X-ray irradiation in a dose- and concentration-dependent manner, whereas the TiO2NPs did not. At the highest concentration of TiOxNPs, the amount of hydroxyl radicals increased by >8.5-fold following treatment with 30 Gy of radiation. The absorption of PAA-TiOxNPs enhanced DNA damage and resulted in higher cytotoxicity in response to X-ray irradiation in vitro. The combination of the PAA-TiOxNPs and X-ray irradiation induced significantly stronger tumor growth inhibition compared to treatment with either PAA-TiOxNPs or X-ray alone (p < 0.05). No apparent toxicity or weight loss was observed for 43 days after irradiation. CONCLUSIONS: TiOxNPs are potential agents for enhancing the effects of radiation on pancreatic cancer and act via hydroxyl radical production; owing to this ability, they can be used for pancreatic cancer therapy in the future.

Development of flocculent Saccharomyces cerevisiae strain GYK-10 for the selective fermentation of glucose/fructose in sugar mills.

Advances in glucose/fructose-selective ethanol production have successfully enhanced raw sugar extraction from sugarcane juice by converting inhibitory substances (i.e., glucose/fructose) into ethanol, which is removed by subsequent operations in cane sugar mills. However, the commercial implementation of this breakthrough process in existing cane sugar mills requires a yeast strain that (i) can be used in food production processes, (ii) exhibits stable saccharometabolic selectivity, and (iii) can be easily separated from the saccharide solution. In this study, we developed a suitable saccharometabolism-selective and flocculent strain, Saccharomyces cerevisiae GYK-10. We obtained a suitable yeast strain for selective fermentation in cane sugar mills using a yeast mating system. First, we crossed a haploid strain defective in sucrose utilization with a flocculent haploid strain. Next, we performed tetrad dissection of the resultant hybrid diploid strain and selected GYK-10 from various segregants by investigating the sucrose assimilation and flocculation capacity phenotypes. Ten consecutive fermentation tests of the GYK-10 strain using a bench-scale fermentor confirmed its suitability for the implementation of practical selective fermentation in a commercial sugar mill. The strain exhibited complete saccharometabolic selectivity and sustained flocculation, where it maintained a high ethanol yield and conversion rate throughout the test.

In situ fabrication of high-performance Ni-GDC-nanocube core-shell anode for low-temperature solid-oxide fuel cells.

A core-shell anode consisting of nickel-gadolinium-doped-ceria (Ni-GDC) nanocubes was directly fabricated by a chemical process in a solution containing a nickel source and GDC nanocubes covered with highly reactive {001} facets. The cermet anode effectively generated a Ni metal framework even at 500 °C with the growth of the Ni spheres. Anode fabrication at such a low temperature without any sintering could insert a finely nanostructured layer close to the interface between the electrolyte and the anode. The maximum power density of the attractive anode was 97 mW cm(-2), which is higher than that of a conventional NiO-GDC anode prepared by an aerosol process at 55 mW cm(-2) and 600 °C, followed by sintering at 1300 °C. Furthermore, the macro- and microstructure of the Ni-GDC-nanocube anode were preserved before and after the power-generation test at 700 °C. Especially, the reactive {001} facets were stabled even after generation test, which served to reduce the activation energy for fuel oxidation successfully.

Nano-architecture of gustatory chemosensory bristles and trachea in Drosophila wings.

In the Drosophila wing anterior margin, the dendrites of gustatory neurons occupy the interior of thin and long bristles that present tiny pores at their extremities. Many attempts to measure ligand-evoked currents in insect wing gustatory neurons have been unsuccessful for technical reasons. The functions of this gustatory activity therefore remain elusive and controversial. To advance our knowledge on this understudied tissue, we investigated the architecture of the wing chemosensory bristles and wing trachea using Raman spectroscopy and fluorescence microscopy. We hypothesized that the wing gustatory hair, an open-ended capillary tube, and the wing trachea constitute biological systems similar to nano-porous materials. We present evidence that argues in favour of the existence of a layer or a bubble of air beneath the pore inside the gustatory hair. We demonstrate that these hollow hairs and wing tracheal tubes fulfil conditions for which the physics of fluids applied to open-ended capillaries and porous materials are relevant. We also document that the wing gustatory hair and tracheal architectures are capable of trapping volatile molecules from the environment, which might increase the efficiency of their spatial detection by way of wing vibrations or during flight.

Hydrothermal crystal growth and structure determination of double hydroxides LiSb(OH)6, BaSn(OH)6, and SrSn(OH)6.

Colorless single crystals of LiSb(OH)6, SrSn(OH)6, and BaSn(OH)6, which are useful as precursors for the synthesis of LiSbO3, SrSnO3, and BaSnO3, were synthesized by a low-temperature hydrothermal method using a Teflon-lined autoclave at 380 K. The crystal structures were determined by single-crystal X-ray diffraction measurements. LiSb(OH)6 crystallizes in the trigonal space group P3̅1m with a = 5.3812(3)A, c = 9.8195(7)A, V = 246.25(3)A(3), Z = 2. In this layered structure, [Li2Sb(OH)6](+) and [Sb(OH)6](-) layers are alternately stacked along the c-direction. The [Li2Sb(OH)6](+) layer can be regarded as a cation-ordered CdCl2 layer. The [Sb(OH)6)](-) layer is built up from isolated [Sb(OH)6](-) octahedra, which are linked to each other via hydrogen bonding within the layer. BaSn(OH)6 and SrSn(OH)6 crystallize with monoclinic P21/n space group symmetry. The monoclinic structure possesses a CsCl-type packing of Ba(2+)/Sr(2+) cations and [Sn(OH)6](2-) anions. The [Sn(OH)6](2-) polyhedra are connected to each other through hydrogen bonding to form a three-dimensional framework. The factors that favor these hitherto unknown crystal structures are discussed using a structure map that compares various M(OH)3 and M'M″(OH)6 compounds.

Raman scattering of linear chains of strongly coupled Ag nanoparticles on SWCNTs.

We compare the Raman scattering properties of hybrid nanostructures consisting of Ag nanoparticles (NPs) in disordered and aligned arrangements on single-walled carbon nanotubes (SWCNTs) as a result of chemical and photoreduction methods. In the latter case, the unique structure of the very small Ag NP (from 4 to 7 nm) chains generated an extremely large mode at 969 cm(-1) that was assigned to the sulphate-silver interaction at the NP surface. Another strong mode was present at 1201 cm(-1) and was assigned to an IR-active mode of sodium dodecyl sulphate (SDS); this mode was observed because the symmetry changes altered the selection rules. We demonstrate that both the UV photoreduction of silver and the presence of SWCNTs are necessary to produce this very strong Raman scattering. The Raman modes of the SWCNTs are also significantly modified by the presence of Ag NP chains along the nanotubes.

Quenching ilmenite with a high-temperature and high-pressure phase using super-high-energy ball milling.

The mass production of highly dense oxides with high-temperature and high-pressure phases allows us to discover functional properties that have never been developed. To date, the quenching of highly dense materials at the gramme-level at ambient atmosphere has never been achieved. Here, we provide evidence of the formation of orthorhombic Fe2TiO4 from trigonal FeTiO3 as a result of the high-temperature (>1250 K) and high-pressure (>23 GPa) condition induced by the high collision energy of 150 gravity generated between steel balls. Ilmenite was steeply quenched by the surrounding atmosphere, when iron-rich ilmenite (Fe2TiO4) with a high-temperature and high-pressure phase was formed by planetary collisions and was released from the collision points between the balls. Our finding allows us to infer that such intense planetary collisions induced by high-energy ball milling contribute to the mass production of a high-temperature and high-pressure phase.

Selective ethanol production from reducing sugars in a saccharide mixture.

Fermentation profiles of four different yeasts reportedly defective in sucrose utilization indicate that all strains tested removed particular sugar via selective conversion to ethanol in a saccharide mixture. At the temperature of pressed sugarcane juice, Saccharomyces dairenensis and Saccharomyces transvaalensis performed better in ethanol production rate and yield, respectively.

Extra-low-temperature oxygen storage capacity of CeO2 nanocrystals with cubic facets.

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.

Material-binding peptide application--ZnO crystal structure control by means of a ZnO-binding peptide.

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.

Oriented growth behavior of Ag nanoparticles using SDS as a shape director.

We report a chemical approach for synthesizing shape-controlled Ag nanoparticles by using the surfactant SDS as a soft template. The experimental approach includes a two-step reaction: the first step is quickly generating Ag seed clusters by a chemical reaction using sodium borohydride as a reducing reagent; the second is the slow growth of controllable Ag nanoparticles by a mild chemical reaction using hydroxylamine hydrochloride as a reducing reagent. Spherical, polyhedral, and fibrous Ag nanoparticles are synthesized successfully in aqueous solution having SDS concentrations of 0.01, 0.02, and 0.2 wt.%, respectively. Size, morphology, and dispersion stability of these Ag nanoparticles depend on the concentrations of both SDS and AgNO(3).

Arrangement of palladium nanoparticles templated by supramolecular self-assembly of SDS wrapped on single-walled carbon nanotubes.

We report a facile route to selectively deposit and arrange palladium (Pd) nanoparticles on single-walled carbon nanotubes (SWCNTs) having sub 10 nm diameter by using supramolecular self-assembly of sodium dodecyl sulfate (SDS) as a soft template.

Anisotropic polyhedral self-assembly of Ag-CNT nanocomposites.

We report the unique assembling behavior of Ag NP supported CNT nanocomposites. Initially Ag NPs were precipitated homogeneously on the walls of SDS-coated CNTs by a NaBH4 chemical reduction and/or photoreduction directly in an aqueous solution. An additional Ag source was subsequently added into the Ag-CNT dispersion and Ag was further reduced using hydroxylamine in a weakly alkaline condition. The morphology of the resulting Ag-CNT nanocomposites strongly depended on the Ag+ ion concentration. Interestingly, an anisotropic polyhedral self-assembly of Ag-CNT nanocomposites was observed when the Ag concentration was increased to 0.1 M (real concentration).