Close-Contact Oxygen Vacancies Synthesized by FSP Promote the Supplement of Active Oxygen Species To Improve the Catalytic Combustion Performance of Toluene.

Catalytic combustion is an important means to reduce toluene pollution, and improving the performance of catalytic combustion catalysts is of great significance for practical applications. The study of oxygen vacancies is one of the key steps to improve catalyst performance. Here, two different oxygen vacancy structures were well-defined and controllably synthesized by flame spray pyrolysis (FSP) to evaluate their effect on the catalytic combustion performance of toluene. The closely contacted oxygen vacancies (c-Vo) enhance the oxygen activation capacity of the catalyst, and the temperature of the first oxygen desorption peak and hydrogen reduction peak is 56 and 37 °C lower than the separated oxygen vacancy (s-Vo) sample, respectively. The oxygen activation energy barrier on the c-Vo is calculated to be negligible of only 0.04 eV. Both in situ DRIFT and DFT calculations indicate that the c-Vo structure accelerates the catalytic oxidation of p-toluene molecules. Moreover, due to the unique characteristics of high-temperature synthesis and rapid quenching, FSP brings excellent water resistance and high-temperature stability to the catalyst. In conclusion, utilizing the FSP in situ reduction strategy can create more c-Vo to improve the catalytic combustion performance of toluene.

Early Osteogenic Marker Expression in hMSCs Cultured onto Acid Etching-Derived Micro- and Nanotopography 3D-Printed Titanium Surfaces.

Polyetheretherketone (PEEK) titanium composite (PTC) is a novel interbody fusion device that combines a PEEK core with titanium alloy (Ti6Al4V) endplates. The present study aimed to investigate the in vitro biological reactivity of human bone-marrow-derived mesenchymal stem cells (hBM-MSCs) to micro- and nanotopographies produced by an acid-etching process on the surface of 3D-printed PTC endplates. Optical profilometer and scanning electron microscopy were used to assess the surface roughness and identify the nano-features of etched or unetched PTC endplates, respectively. The viability, morphology and the expression of specific osteogenic markers were examined after 7 days of culture in the seeded cells. Haralick texture analysis was carried out on the unseeded endplates to correlate surface texture features to the biological data. The acid-etching process modified the surface roughness of the 3D-printed PTC endplates, creating micro- and nano-scale structures that significantly contributed to sustaining the viability of hBM-MSCs and triggering the expression of early osteogenic markers, such as alkaline phosphatase activity and bone-ECM protein production. Finally, the topography of 3D-printed PTC endplates influenced Haralick's features, which in turn correlated with the expression of two osteogenic markers, osteopontin and osteocalcin. Overall, these data demonstrate that the acid-etching process of PTC endplates created a favourable environment for osteogenic differentiation of hBM-MSCs and may potentially have clinical benefit.

Zinc Fertilizers Modified the Formation and Properties of Iron Plaque and Arsenic Accumulation in Rice (Oryza sativa L.) in a Life Cycle Study.

This study examined the effect of three forms of zinc fertilizers on arsenic (As) accumulation and speciation in rice tissues over the life cycle of this cereal crop in a paddy soil. The formation and properties of iron plaque on rice roots at the maximum tillering stage and the mature stage were also determined. Elevated As at 5 mg/kg markedly lowered the rice yield by 86%; however, 100 mg/kg Zn fertilizers significantly increased the rice yield by 354-686%, regardless of the Zn form. Interestingly, only Zn2+ significantly lowered the total As in rice grains by 17% to 3.5 mg/kg and As(III) by 64% to around 0.5 mg/kg. Zinc amendments substantially hindered and, in the case of zinc oxide bulk particles (ZnOBPs), fully prevented the crystallization of iron oxides (Fe3O4 and Fe2O3) and silicon oxide (SiO2) and altered the composition of iron plaques on rice roots. SiO2 was first reported to be a significant component of iron plaque. Overall, ZnOBPs, ZnO nanoparticles, and Zn2+ displayed significant yet distinctive effects on the properties of iron plaque and As accumulation in rice grains, providing a fresh perspective on the potentially unintended consequences of different Zn fertilizers on food safety.

Highly efficient Au/Fe2O3 for CO oxidation: The vital role of spongy Fe2O3 toward high catalytic activity and stability.

Supported gold catalysts have drawn great attention for many decades due to their outstanding performance in remedying the environment from carbon monoxide (CO) pollution. In this study, due to the large surface area of spongy Fe2O3, fabricated by salt-assisted ultrasonic spray pyrolysis, a considerable amount of Au was loaded on spongy Fe2O3 compared to low-surface-area non-spongy Fe2O3. It is seen that the spongy Fe2O3 catalyst loaded with Au has an interface that can be extremely active for CO desorption and O2 activation. That means it has high catalytic activity in CO oxidation than non-spongy and low surface area Fe2O3 loaded with Au. Also, the incorporation of Au in low alkaline condition further enhances the interaction between Au and Fe2O3, providing more active sites. This made the catalyst to have better activity, good stability over 60 hrs, and there was no carbonate on its surface. It had full conversion at 30 °C on 120 L g-1h-1 with high TOF (2.2 s-1).

Tapered Optical Fiber Detector for a Red Dye Concentration Measurement.

BACKGROUND: In this work, a detector based on optical fiber covered with Multi-Wall Carbon Nanotubes (MWCNTs) was used for sensing and removal of Alizarin from wastewaters. Alizarin is a strong anionic red dye that is part of the anthraquinone dye group. As a rule, this dye is used in the textile industry as a coloring agent. Experiments showed a good efficiency of wastewater treatment. This development could resolve the problem of water contamination with Alizarin red dye. METHODS: We used a single-mode fiber SMF-28e with a core diameter of 8.2 µm and a cladding diameter of 125 µm as a base for the tapered optical fiber detector. An MWCNTs array was synthesized on the tapered optical fiber detector surface by spray pyrolysis Chemical Vapor Deposition (CVD) method at 800oC for 20 min inside a tubular furnace, using ferrocene solution in toluene as a catalyst precursor. The formed structure was applied for Alizarin detection in water. RESULTS: According to the patent studies, the nanotubes completely covered the optical fiber surface and the array had a high density with minimal distance between nearby nanotubes. Carbon nanotubes were oriented along the radius of the optical fiber. The average diameter of carbon nanotubes was 24 nm. The optical absorbance levels increased as the Alizarin concentration increased from 50 mg/L to 1000 mg/L. MWCNTs on the optical fiber tapered section adsorbed the dye molecules from aqueous solution. Three intensive absorption bands with the wavelength of the 700, 714 and 730 nm appeared and their intensity increased as the Alizarin concentration increased. The accumulated Alizarin can be recovered by multiple immersing clean water. This property may make tapered optical fiber detector reusable and increase the economic expediency of the sensor application. CONCLUSION: The study showed higher Alizarin adsorption efficiency of the tapered optical fiber detector compared with relative detectors. This structure can be reusable for dye detection. Removal efficiency for Alizarin reached 98.6%, which makes the tapered optical fiber detector promising for wastewater treatment and dye elimination.

Attachment of cerium oxide nanoparticles of different surface charges to kaolinite: Molecular and atomic mechanisms.

Sustainable applications of nanotechnology in agriculture require insights into the interactions between engineered nanoparticles (ENPs) and clay minerals, a key component in soil that governs the soil properties and functions. This study investigated the charge-dependent interactions of cerium oxide nanoparticles (CeO2NPs) with kaolinite at atomic level with several complementary surface characterization techniques. High resolution transmission electron microscope (HRTEM) and atomic force microscope (AFM) images showed strong attachment of positively charged and neutral CeO2NPs to the surface of kaolinite while the negatively charged CeO2NPs demonstrated low affinity to the surface of kaolinite, indicating strong electrostatic interactions between CeO2NPs and kaolinite surface. Attached CeO2NPs on kaolinite surface displayed charge-dependent aggregation, with neutral CeO2NPs showing the most substantial aggregation on kaolinite surface. The variation in hydrodynamic size and surface charge of kaolinite with the charge on CeO2NPs was observed. The attachment of CeO2NPs also changed the surface charge density distribution on the surface of kaolinite, converting a relatively homogenously charged basal plane into a heterogeneously charged plate. The change on kaolinite surface charge density may markedly affect the interactions of clay minerals with surrounding macro- and micro-nutrients in soil pore water and affect their bioavailability to plants.

Anisotropic Strain Induced Directional Metallicity in Highly Epitaxial LaBaCo2O5.5+δ Thin Films on (110) NdGaO3.

Highly directional-dependent metal-insulator transition is observed in epitaxial double perovskite LaBaCo2O5.5+δ films. The film exhibit metallic along [100], but remain semiconducting along [010] under application of a magnetic field parallel to the surface of the film. The physical origin for the properties is identified as in-plane tensile strain arising from oxygen vacancies. First-principle calculations suggested the tensile strain drastically alters the band gap, and the vanishing gap opens up [100] conduction channels for Fermi-surface electrons. Our observation of strain-induced highly directional-dependent metal-insulator transition may open up new dimension for multifunctional devices.

Morphology-tunable synthesis of ZnO nanoforest and its photoelectrochemical performance.

Understanding and manipulating synthesis reactions and crystal growth mechanisms are keys to designing and constructing the morphology and functional properties of advanced materials. Herein, the morphology-controlled synthesis of three-dimensional (3D) ZnO nanoforests is reported via a facile hydrothermal route. Specifically, the respective and synergistic influence of polyethylenimine (PEI) and ammonia on tuning the architecture of ZnO nanoforests is systematically studied. An in-depth understanding of the mechanism of hydrothermal growth is vital for advancing this facile approach and incorporating special 3D nanostructures into versatile nanomanufacturing. More importantly, its unique architectural characteristics endow the willow-like ZnO nanoforest with prominent photoelectrochemical water splitting performance, including small charge transfer resistance, long photoelectron lifetime, a high photocurrent density of 0.919 mA cm(-2) at +1.2 V (vs. Ag/AgCl), and more important, a high photoconversion efficiency of 0.299% at 0.89 V (vs. RHE), which leads the realm of homogeneous ZnO nanostructures. In all, it is expected that this work will open up an unprecedented avenue to govern desirable 3D ZnO nanostructures and broaden the application potentials of 3D nanotechnology.

The origin of local strain in highly epitaxial oxide thin films.

The ability to control the microstructures and physical properties of hetero-epitaxial functional oxide thin films and artificial structures is a long-sought goal in functional materials research. Normally, only the lattice misfit between the film and the substrate is considered to govern the physical properties of the epitaxial films. In fact, the mismatch of film unit cell arrangement and the Surface-Step-Terrace (SST) dimension of the substrate, named as "SST residual matching", is another key factor that significantly influence the properties of the epitaxial film. The nature of strong local strain induced from both lattice mismatch and the SST residual matching on ferroelectric (Ba,Sr)TiO3 and ferromagnetic (La,Ca)MnO3 thin films are systematically investigated and it is demonstrated that this combined effect has a dramatic impact on the physical properties of highly epitaxial oxide thin films. A giant anomalous magnetoresistance effect (~10(10)) was achieved from the as-designed vicinal surfaces.

Interface engineered BaTiO3/SrTiO3 heterostructures with optimized high-frequency dielectric properties.

Interface engineered BaTiO3/SrTiO3 heterostructures were epitaxially grown on (001) MgO substrates by pulsed laser deposition. Microstructural characterizations by X-ray diffraction and transmission electron microscopy indicate that the as-grown heterostructures are c-axis oriented with sharp interfaces. The interface relationships between the substrate and multilayered structures were determined to be [001](SrTiO3)//[001](BaTiO3)//[001](MgO) and (100)(SrTiO3)//(100)(BaTiO3)//(100)(MgO). The high-frequency microwave (∼18 GHz) dielectric measurements reveal that the dielectric constant and dielectric loss of the nanolayered heterostructures are highly dependent upon the stacking period numbers and layer thicknesses. With the increase in the periodic number, or the decrease in each layer thickness, the dielectric constant dramatically increases and the dielectric loss tangent rapidly decreases. The strong interface effect were found when the combination period is larger than 16, or each STO layer is less than 6.0 nm. The optimized dielectric performance was achieved with the best value for the loss tangent (0.02) and the dielectric constant (1320), which suggests that the BTO/STO heterostructures be promising for the development of the room-temperature tunable microwave elements.

Giant magnetoresistance and anomalous magnetic properties of highly epitaxial ferromagnetic LaBaCo2O(5.5+δ) thin films on (001) MgO.

Ferromagnetic thin films of the A-site nano-ordered double perovskite LaBaCo(2)O(5.5+δ) (LBCO) were grown on (001) MgO, and their structural and magnetic properties were characterized. The as-grown films have an excellent epitaxial behavior with atomically sharp interfaces, with the c-axis of the LBCO structure lying in the film plane and the interface relationship given by (100)(LBCO)//(001)(MgO) and [001](LBCO)//[100](MgO) or [010](MgO). The as-grown LBCO films exhibit a giant magnetoresistance (54% at 40 K under 7 T) and an anomalous magnetic hysteresis, depending strongly on the temperature and the applied magnetic field scan width.

Trapping Iron Oxide into Hollow Gold Nanoparticles.

Synthesis of the core/shell-structured Fe3O4/Au nanoparticles by trapping Fe3O4 inside hollow Au nanoparticles is described. The produced composite nanoparticles are strongly magnetic with their surface plasmon resonance peaks in the near infrared region (wavelength from 700 to 800 nm), combining desirable magnetic and plasmonic properties into one nanoparticle. They are particularly suitable for in vivo diagnostic and therapeutic applications. The intact Au surface provides convenient anchorage sites for attachment of targeting molecules, and the particles can be activated by both near infrared lights and magnetic fields. As more and more hollow nanoparticles become available, this synthetic method would find general applications in the fabrication of core-shell multifunctional nanostructures.

Wear mechanism of nanocrystalline metals.

Our tribological experiments on nanocrystalline (nc) Ni (grain size down to approximately 10 nm) showed significant reductions in both, the coefficient of friction and wear rate compared to its microcrystalline (mc) counterpart. A consistent relationship was found between grain size, hardness and tribological behavior. In the present study, the wear mechanism was investigated by conducting transmission electron microscopy (TEM) and nanoindentation experiments in the wear track region. TEM observations revealed that sliding wear developed two entirely different substructures in mc and nc Ni. Under the extensive plastic deformation, surface nanocrystallization occurred in the former and deformation-induced grain growth in the latter. These changes were consistent with the nanoin-dentation measurements from the wear track. Hardness in the mc Ni was increased due to work hardening/surface nanocrystallization. On the contrary, hardness remained at similar or slightly lower levels for nc Ni probably due to grain coarsening from the activation of grain boundary-related modes of deformation. The two different deformation mechanisms are consistent with the observed differences in frictional behavior and wear resistance that involves wear/fatigue for mc Ni and fine scale abrasion for nc Ni.

Capturing electrochemically evolved nanobubbles by electroless deposition. A facile route to the synthesis of hollow nanoparticles.

Gas evolution during electrochemical deposition has long been regarded as undesired and deliberately suppressed. Here, we show a new role of electrochemically evolved hydrogen bubbles, serving as both templates and reducing agent to form hollow Au nanoparticles via electroless deposition. Hollow gold nanoparticles with a complete nanocrystalline shell and a 50 nm hollow core were fabricated. By controlling the shell thickness, particle size can be varied from 100 to 150 nm. The process is very simple, scalable, and with a high throughput. Using this method, more complicated hollow nanostructures such as double nanoshells ("nanomatryoshka") can also be synthesized. These hollow nanoparticles possess desirable plasmonic properties and can potentially be used as nanocontainers to store and deliver gaseous materials. In addition, the process can be used for fundamental studies of nanobubble formation mechanism.