Allen Apblett

Anatase-phase TiO ₂ nanorods with diameters of approximately 3 ± 1 nm and lengths of 40 ± 10 nm were successfully synthesized using a solvothermal method, followed by metal doping through thermal diffusion of Fe ²⁺ ions onto the nanocrystals.

Anatase-phase rod-shaped TiO₂ nanocrystals are prepared by the solvothermal method, the surface is metalated, and doped nanocrystals are achieved by thermal diffusion of surface metal ions. Incorporation of dopant ions into TiO₂ lattice enhances the visible light absorption of the material and in some cases can increase the rate of photocatalysis. Even though there are overflowing studies on the preparation of doped TiO₂ materials, there are no methods that enable the precise control of dopant concentration in TiO₂ nanocrystals. We have developed a method to load the surface of oleic acid stabilized anatase-phase rod-shaped TiO₂ nanocrystals (approx. 3 ± 1 nm diameter and 40 ± 10 nm long) with transition metal ions followed by ion diffusion to prepare metal-doped nanocrystals with exact control of the dopant concentration. Specifically, in this work, Cr³⁺ adsorbs TiO₂ nanorods to yield a green colloid, followed by ion diffusion at elevated temperature. After removal of any remaining surface Cr³⁺, tan-colored chromium-doped TiO₂ nanorods can be obtained. Electron microscopy and powder X-ray diffraction indicate no change in nanocrystal size and morphology throughout the process. The TiO₂ nanorods play an important role in photocatalysis owing to their excellent chemical and physical properties. Titanium dioxide is a low-cost, non-toxic, highly stable, chemically robust material. Doped TiO₂ materials have found application in photocatalysis (oxidative degradation of organic molecules, hydrogen evolution), photovoltaics, solar cells, lithium-ion batteries, supercapacitors, and sensors. TiO₂ photocatalysis is also the basis for clean energy technologies, such as dye-sensitized solar cells and photoelectrochemical cells. In photocatalysis applications, nanocrystalline TiO₂ presents advantages of a high surface area, ability to control the surface facet, and minimized bulk recombination.

Titanium(IV) solutions are known to detect hydrogen peroxide in solutions by a colorimetric method. Xplosafe’s XploSens PS commercial titanium(IV)-based peroxide detection test strips are used to detect hydrogen peroxide in liquids. The use of these test strips as gas-phase detectors for peroxides was tested using low-cost hardware. The exposure of these strips to hydrogen peroxide liquid or gas leads to the development of an intense yellow color. For liquids, a digital single-lens reflex camera was used to quantify the color change using standardized solutions containing between 50 and 500 ppm peroxide by mass. Analysis of the images with color separation can provide a more quantitative determination than visual comparison to a color chart. For hydrogen peroxide gas, an inexpensive web camera and a tungsten lamp were used to measure the reflected light intensity as a function of exposure from a test strip held in a custom cell. First-order behavior in the color change with time was observed during the exposure to peroxide vapor over a range of peroxide concentrations from 2 and 30 ppm by volume. For a 1-min measurement, the gas-phase detection limit is estimated to be 1 ppm. A 0.01 ppm detection limit can be obtained with a 1-h exposure time. Titanium(IV)-based peroxide detection test strips are sensitive enough to work as a gas-phase hydrogen peroxide detector.

The asymmetric unit of the title compound, 2,4,6-triamino-1,3,5-triazin-1-ium cyanoacetate monohydrate, C₃H₇N₆ ⁺·NCCH₂COO⁻·H₂O, consists of a melaminium cation, a cyanoacetate anion and a water molecule, which are connected to each other via N—H...O and O—H...O hydrogen bonds, generating an eight-membered ring. In the crystal, the melaminium cations are connected by two pairs of N—H...N hydrogen bonds, forming tapes along [110]. These tapes develop a three-dimensional network through N—H...O, O—H...O, N—H...N and C—H...O hydrogen bonds between the cations, anions and water molecules.

A nanoporous WO₃sorbent was found to be highly reactive towards Pb²⁺, exhibiting a molar sorption capacity of 42.5% and sorption half-lives as low as 47 s.

Water‐soluble precursors for nanometric calcium tungstate (CaWO ₄ ) were prepared from calcium 2‐hydroxycarboxylate salts. The precursors decompose as low as 425 °C to yield nanocrystalline scheelite. Supported CaWO ₄ in a convenient form for water treatment processes was prepared by impregnation of high surface area catalyst support pellets with an aqueous solution of a single‐source precursor followed by drying and calcining. Both the powder and supported nanocrystalline forms of CaWO ₄ underwent ion‐exchange reaction with aqueous lead ions whereby Ca ²⁺ was released and Pb ²⁺ was adsorbed to produce crystalline stolzite (PbWO ₄ ). Electron microscopy demonstrated that little morphological change of the particles occurred upon reaction with excess Pb ²⁺ . The process appears to occur via an ion‐exchange route. The nonlinear pseudo first‐order kinetic model gave the best fit for both the powder and supported forms of CaWO ₄ , allowing the kinetic results from the two materials to be directly compared to each other. Supporting of CaWO ₄ improves the kinetics at higher CaWO ₄ :Pb ²⁺ ratios while at lower ratios diffusion of the Pb ²⁺ ions into the porous pellets likely becomes the controlling factor and the powder form uptakes Pb ²⁺ faster. The molar capacity of the material for Pb ²⁺ uptake improved from 70 % to 100 % upon supporting the CaWO ₄ . The novel ion‐exchange materials were demonstrated to be useful for the purification of industrial wastewaters and juice.

A commercially-available tungsten trioxide nanopowder was investigated and shown to be an excellent sorbent for removal of Pb²⁺ions from water.

This paper describes the results of an experimental study that uses radio frequency identification (RFID) technology to detect cracking in concrete elements. A RFID-based sensor is used to monitor the change in electrical resistance that occurs in conductive materials applied to the surface of the concrete. When the concrete substrate is strained, the conductive material at the surface is stretched, and its electrical resistance increases. If the concrete substrate is strained to the point where it cracks, the conductive material at the surface also cracks, causing its electrical resistance to increase by orders of magnitude. This paper describes how this increase in electrical resistance attributable to cracking can be detected wirelessly by RFID technology. To experimentally illustrate the application of this technology, an RFID-based sensor and conductive surface materials are used to detect cracking in the restrained ring test. The experimental results indicate that this technology can be easi...

Nanometric lead molybdate was prepared using lead nitrate and an aqueous suspension of nanoparticulate (190 nm) molybdenum trioxide and by varying the concentration of the reactants. At intermediate concentrations, less precipitate was formed in favor of formation of a stable suspension of nanoparticles (48 nm) that displayed a very strong Tyndall effect. At high dilution, particles that resembled German crosses were produced.