Electrical Conductivity, Thermoelectric Power, and Equilibration Kinetics of Nb-Doped TiO2.

This work considers the equilibration kinetics of Nb-doped TiO2 single crystal (0.066 atom % Nb) during oxidation and reduction within a wide range of temperature (1073-1298 K) and oxygen activity (10(-14)-10(5) Pa). The associated semiconducting properties were determined using simultaneous measurements of both electrical conductivity and thermoelectric power.

Defect chemistry and defect engineering of TiO2-based semiconductors for solar energy conversion.

This tutorial review considers defect chemistry of TiO2 and its solid solutions as well as defect-related properties associated with solar-to-chemical energy conversion, such as Fermi level, bandgap, charge transport and surface active sites. Defect disorder is discussed in terms of defect reactions and the related charge compensation. Defect equilibria are used in derivation of defect diagrams showing the effect of oxygen activity and temperature on the concentration of both ionic and electronic defects.

Repulsive van der waals forces self-limit native oxide growth.

Silicon is one of the most studied materials, yet questions remain unanswered about its unusual property of growing a self-limiting native oxide that attains its final thickness in a matter of hours yet months later has not grown further. For the first time, we have explored this self-limiting growth in terms of repulsive van der Waals (vdW) forces generated by the combination of material properties inherent to the system. These repulsive forces represent an energy barrier preventing additional oxidizing chemicals, mainly oxygen and water, from adsorbing on the surface as well as hindering diffusion of those that do adsorb toward the interface.

Control of adhesion force between ceria particles and polishing pad in shallow trench isolation chemical mechanical planarization.

The adhesion force between ceria and polyurethane (PU) pad was controlled to remove the step height from cell region to peripheral region during Shallow Trench Isolation Chemical Mechanical Planarization (STI-CMP) for NAND flash. Picolinic acid was found to be adsorbed on ceria particles at pH 4.5 following a Langmuir isotherm with the maximum adsorbed amount of 0.

Role of the surface chemistry of ceria surfaces on silicate adsorption.

Ceria nanoparticles (NPs) have been widely explored as a promising material in various fields. As synthesized under various physicochemical conditions, it exhibits the different surface chemistry. Here, the role of hydroxyl and nitrate group on ceria surface, formed under various physicochemical conditions, for the silicate adsorption was experimentally and theoretically investigated based on the adsorption isotherms and theoretical analyses using density functional theory (DFT) calculation.

Tin(II) amide/alkoxide coordination compounds for production of Sn-based nanowires for lithium ion battery anode materials.

A series of tin(II) amide alkoxides ([(OR)Sn(NMe(2))](n)) and tin(II) alkoxides ([Sn(OR)(2)](n)) were investigated as precursors for the production of tin oxide (SnO(x)) nanowires. The precursors were synthesized from the metathesis of tin dimethylamide ([Sn(NMe(2))(2)](2)) and a series of aryl alcohols {H-OAr = H-OC(6)H(4)(R)-2: R = CH(3) (H-oMP), CH(CH(3))(2) (H-oPP), C(CH(3))(3) (H-oBP)] or [H-OC(6)H(3)(R)(2)-2,6: R = CH(3) (H-DMP), CH(CH(3))(2) (H-DIP), C(CH(3))(3) (H-DBP)]}. The 1:1 products were all identified as the dinuclear species [(OAr)Sn(μ-NMe(2))](2) where OAr = oMP (1), oPP (2), oBP (3), DMP (4), DIP (5), DBP (6).

Thermally tunable surface wettability of electrospun fiber mats: polystyrene/poly(N-isopropylacrylamide) blended versus crosslinked poly[(N-isopropylacrylamide)-co-(methacrylic acid)].

This work reports on thermally tunable surface wettability of electrospun fiber mats of: polystyrene (PS)/poly(N-isopropylacrylamide) (PNIPA) blended (bl-PS/PNIPA) and crosslinked poly[(N-isopropylacrylamide)-co-[methacrylic acid)] (PNIPAMAA) (xl-NIPAMAA). Both the bl-PS/PNIPA and xl-PNIPAMAA fiber mats demonstrate reversibly switchable surface wettability, with the bl-PS/PNIPA fiber mats approaching superhydrophobic ≥150° and superhydrophilic contact angle (CA) values at extreme temperatures. Weight loss studies carried out at 10 °C indicate that the crosslinked PNIPAMAA fiber mats had better structural integrity than the bl-PS/PNIPA fiber mats.

Force interactions of porous silica glass microspheres against mirror-polished stainless steel in nonaqueous solvents.

Force interactions of porous silica particles against mirror-polished stainless steel surfaces were quantified in the presence of various solvents to facilitate processing of ceramics with less reliance on organic aids which subsequently need to be burned off. The results were compared to and found to be in good agreement to idealized models of van der Waals force interactions. Significantly, van der Waals attractive forces between steel surfaces and silica surfaces were minimized through the use of tetrahydrofuran and enhanced using methanol.

Microwave assisted nanofibrous air filtration for disinfection of bioaerosols.

Airborne biological agents, albeit intentionally released or naturally occurring, pose one of the biggest threats to public health and security. In this study, a microwave assisted nanofibrous air filtration system was developed to disinfect air containing airborne pathogens. Aerosolized vegetative cells and endospores, as benign surrogates of pathogens, were collected on nanofibrous filters and treated by microwave irradiation.

Coaxially electrospun PVDF-Teflon AF and Teflon AF-PVDF core-sheath nanofiber mats with superhydrophobic properties.

This work reports the coaxial electrospinning of poly(vinylidene fluoride) (PVDF)-Teflon amorphous fluoropolymer (AF) and Teflon AF-PVDF core-sheath nanofiber mats yielding superhydrophobic properties. The coaxial electrospinning configuration allows for the electrospinning of Teflon AF, a nonelectrospinnable polymer, with the help of an electrospinnable PVDF polymer. PVDF-Teflon AF and Teflon AF-PVDF core-sheath fibers have been found to a have mean fiber diameter ranging from 400 nm to less than 100 nm.

Synthesis and characterization of luminescent cerium oxide nanoparticles.

Aims: Fluorescent cerium oxide (ceria) nanoparticles were developed through incorporation of erbium into the lattice. Catalytic properties and luminescent behavior are examined.

Materials & Methods: Cerium-erbium mixed oxide nanoparticles were synthesized by the reverse micelles route.

Artificial hairy surfaces with a nearly perfect hydrophobic response.

A nearly perfect hydrophobic interface by dint of mimicking hairs of arthropods was achieved for the first time. These Gamma-shape artificial hairs were made via a membrane casting technique on polypropylene substrates. This extreme hydrophobicity merely arises from microstructure modification, and no further chemical treatments are needed.

Adsorption of sodium polyacrylate in high solids loading calcium carbonate slurries.

The adsorption of sodium polyacrylate (NaPAA) in slurries with up to 75 wt.% calcium carbonate was investigated with the use of attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and adsorption of probe molecules. Analysis of the IR spectra demonstrated that the carboxylate groups of NaPAA adsorbed onto ground calcium carbonate (GCC) in three different modes.

Reactive oxygen species scavenging properties of ZrO2-CeO2 solid solution nanoparticles.

Aims: The hypothesis that an increase in defects in cerium oxide (CeO(2)) nanoparticles induced by solid solutions with differences in valency and ionic radius of the solute will yield superior reactive oxygen species (ROS) scavengers at room temperature will be tested.

Methods: Solid solutions of zirconium in CeO(2), that is, Ce(x)Zr(1-x)O(2) nanoparticles, were synthesized by a reverse micelle method. Their crystal structures, particle sizes and level of agglomeration were characterized.

Novel synthesis of cerium oxide nanoparticles for free radical scavenging.

Aims: The aim of this article is to present a novel synthetic route to form CeO(2) nanoparticles that protects against the detrimental influence of oxidative stress in mammalian cells.

Methods: The noncytotoxic surfactant lecithin was used to synthesize CeO(2) nanoparticles and the products were colloidally stabilized in a biocompatible tri-sodium citrate buffer. These nanoparticles were delivered into murine insulinoma betaTC-tet cells, and intracellular free radical concentrations responding to exposure to hydroquinone were measured in a variety of extracellular CeO(2) concentrations.

Synthesis of anatase-silver nanocomposite fibers via electrospinning.

There has been growing interest in new ways to produce composite nanofibers. Continuous TiO2 (anatase phase) nanofibers with silver nanoparticles were prepared successfully via sol-gel and electrospinning. A sol containing poly(vinyl pyrrolidone), titanium tetraisopropoxide, and silver nitrate was injected through a conductive capillary where high voltage was applied.

Magnetically agitated photocatalytic reactor for photocatalytic oxidation of aqueous phase organic pollutants.

A magnetically agitated photocatalytic reactor (MAPR) has been developed and assessed for oxidation of phenol. The MAPR uses a titanium dioxide composite photocatalyst with a ferromagnetic barium ferrite core. The catalyst motion was controlled with a dual-component magnetic field.

Direct surface force measurement in water using a nanosize colloidal probe technique.

The direct force measurement between colloidal surfaces has been an essential topic in both theories and applications of surface chemistry. As particle size is decreased from micron size down to true nano size (<10 nm), surface forces are increasingly important. Nanoparticles at close proximity or high solids loading are expected to show a different behavior than what can be estimated from continuum and mean field theories.

Adsorption enhancement mechanisms of silica-titania nanocomposites for elemental mercury vapor removal.

A novel nanocomposite that combines high-surface area silica with the photocatalytic properties of titania has been developed that allows for effective capture of elemental mercury vapor. The adsorption capability of the developed material has been found to improve after periods of photocatalytic oxidation. In this study, the mechanisms for adsorption enhancement were identified.

Inactivation of bacterial endospores by photocatalytic nanocomposites.

A novel biocidal photocatalytic nanocomposite, composed of TiO(2) and multi-walled carbon nanotubes (MWNTs), was synthesized via wet chemistry followed by a heat treatment. Uniform anatase coatings on MWNTs were successfully obtained with a thickness of a few nanometers. The nanostructure of the composite was determined by high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD).

Functionalized multiwall carbon nanotube/gold nanoparticle composites.

Multiwall carbon nanotubes (MWCNTs) were chemically oxidized in a mixture of sulfuric acid and nitric acid (3:1) while being ultrasonicated. The effect of oxidative ultrasonication at room temperature on development of functional groups on the carbon nanotubes was investigated. The dispersability and the carboxylic acid group concentration of functionalized MWCNTs (fMWNTs) varied with reaction time.

ZnO nanocrystals synthesized by physical vapor deposition.

Various types of zinc oxide (ZnO) nanocrystais were synthesized by physical vaporization of zinc powders without the presence of catalysts and a subsequent exposure to air at a high temperature. These crystals were found to be composed of ZnO nanowires, sheets, and tetrapods. They were observed to crystallize as wurtzite ZnO single crystals.

Dip-pen nanolithography with poly(diallyl dimethyl ammonium) chloride.

Poly(diallyl dimethyl ammonium) chloride (PDAC), a high molecular weight cationic polyelectrolyte, was used as ink for dip-pen nanolithography. Line patterns were generated on bare silicon wafers directly with PDAC-coated tips. Widths and heights of lines increased with decreasing scan rates.

Formation of anatase TiO2 nanoparticles on carbon nanotubes.

Anatase TiO2 nanoparticles with a size range of 2 to 10 nm have been formed on carbon nanotubes by the controlled hydrolysis and condensation of titanium bis-ammonium lactato dihydroxide in water and electrosterically dispersed carbon nanotubes.

Cation-induced collapse of low-molecular-weight polyacrylic acid in the dispersion of barium titanate.

Observations on the steric layers formed by the adsorption of low-molecular-weight polyacrylic acid (PAA) were taken using the colloidal probe method in an atomic force microscope. The effects of divalent barium ions and of monovalent potassium ions at varying concentrations were observed on the repulsive interaction profiles. High ionic concentrations screened double-layer forces to small distances, whereby the acting forces were reduced to steric interactions.