Structurally Stabilized Organosilane‐Templated Thermostable Mesoporous Titania

Structurally thermostable mesoporous anatase TiO₂ (m‐TiO₂) nanoparticles, uniquely decorated with atomically dispersed SiO₂, is reported for the first time. The inorganic Si portion of the novel organosilane template, used as a mesopores‐directing agent, is found to be incorporated in the pore walls of the titania aggregates, mainly as isolated sites. This is evident by transmission electron microscopy and high‐angle annular dark field scanning transmission electron microscopy, combined with electron dispersive X‐ray spectroscopy. This type of unique structure provides exceptional stability to this new material against thermal collapse of the mesoporous structure, which is reflected in its high surface area (the highest known for anatase titania), even after high‐temperature (550 °C) calcination. Control of crystallite size, pore diameter, and surface area is achieved by varying the molar ratios of the titanium precursor and the template during synthesis. These mesoporous materials retain their porosity and high surface area after template removal and further NaOH/HCl treatment to remove silica. We investigate their performance for dye‐sensitized solar cells (DSSCs) with bilayer TiO₂ electrodes, which are prepared by applying a coating of m‐TiO₂ onto a commercial titania (P25) film. The high surface area of the upper mesoporous layer in the P25–m‐TiO₂ DSSC significantly increases the dye loading ability of the photoanode. The photocurrent and fill factor for the DSSC with the bilayer TiO₂ electrode are greatly improved. The large increase in photocurrent current (ca. 56 %) in the P25–m‐TiO₂ DSSC is believed to play a significant role in achieving a remarkable increase in the photovoltaic efficiency (60 %) of the device, compared to DSSCs with a monolayer of P25 as the electrode.     

Polyaniline‐tailored electromechanical responses of the silver/epoxy conductive adhesive composites

In this article, the electromechanical properties of silver‐in‐epoxy conductive adhesives with the polyaniline (PANI) micron particles as cofillers have been investigated. PANI is a conductive polymer and has a moderate conductivity in between those of silver and epoxy. It was found that PANI can be used to tailor both the adhesive's electrical contact resistance and its relaxation behavior; however, the effects of adding PANI were complex. The addition of small amount of PANI (2 wt %) dramatically increased the contact resistance; it might block the electrical contacts among silver flakes and was not able to form a continuous path among themselves. The addition of more PANI showed a moderate increase in contact resistance, which increased with the weight fraction of PANI from 6 to 15 wt %. Interdependent behavior of compressive strain and relaxation in electrical contact resistance is characterized to evaluate the origin of this relaxation. The addition of PANI made the relaxation in electrical contact resistance more sensitive to the compressive strain and the electromechanical coupling to deviate from the linear relationship. These research findings provide insights into the way to use PANI to tailor the electromechanical properties of the adhesive bonds or joints in the development of advanced functional devices. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013, 51, 1448–1455     

Thermal annealing combination with pulse Nd-YAG laser treatment of ITO on polycarbonate using spin coating process

This work, we report a cost effective method to decompose ITO thin layer on polycarbonate as flexible substrate by means of spin coating technique. Three calcinations techniques were carried out. The coating were deposited by spin and cured by heat, ultraviolet (UV) irradiation and Nd-YAG pulse laser. The resistivity change on annealing of the amorphous film by thermal, UV and laser was investigated by X-ray diffraction, scanning electron microscopy, atomic force spectroscopy and UV–Vis spectrometer. It is shown that the resistance of coated film on polymer decreases dramatically to less than impedance spectroscopy (600 Ω) when using combination of low heat treatment and laser irradiation with a wavelength of 1,100 nm and energy of 6–25 J.     

Novel nanocomposite membranes based on polybenzimidazole and Fe<Subscript>2</Subscript>TiO<Subscript>5</Subscript> nanoparticles for proton exchange membrane fuel cells

In this work, Fe₂TiO₅ nanoparticles were used for improving the proton conductivity, and water and acid uptake of polybenzimidazole (PBI)-based proton exchange membranes. The nanocomposite membranes have been prepared using different amounts of Fe₂TiO₅ nanoparticles and dispersed into a PBI membrane with the solution-casting method. The prepared membranes were then physico-chemically and electrochemically characterized for use as electrolytes in high-temperature PEMFCs. The PBI/Fe₂TiO₅ membranes (PFT) showed a higher acid uptake and proton conductivity compared with the pure PBI membranes. The highest acid uptake (156 %) and proton conductivity (78 mS/cm at 180 °C) were observed for the PBI nanocomposite membranes containing 4 wt% of Fe₂TiO₅ nanoparticles (PFT₄). The PFT₄ composite membrane showed 380 mW/cm² power density and 760 mA/cm² current density in 0.5 V at 180 °C at dry condition. The above results indicated that the PFT₄ nanocomposite membranes could be utilized as proton exchange membranes for high-temperature fuel cells.     

Schiff base‐functionalized boehmite nanoparticle‐supported molybdenum and vanadium complexes: efficient catalysts for the epoxidation of alkenes

Boehmite nanoparticles, with high surface area and high degree of surface hydroxyl groups, were prepared via hydrothermal‐assisted sol–gel processing of aluminium 2‐butoxide. The produced powder was covalently functionalized with 3‐(trimethoxysilyl)propylamine, and then, in order to support vanadium oxosulfate and molybdenum hexacarbonyl complexes, all the terminal amine groups were changed to Schiff bases by refluxing with salicylaldehyde. These catalysts were applied in the epoxidation of cis‐cyclooctene and other olefins with tert‐BuOOH in CCl₄. The catalytic procedures for both catalysts were optimized for various parameters such as solvent and oxidant. Recycling experiments revealed that these heterogeneous nano‐catalysts could be repeatedly applied for the epoxidation of alkenes. Copyright © 2015 John Wiley & Sons, Ltd.     

Closed vessels microwave digestion method for uranium analysis of soils using alpha-spectroscopy

The neutron activation analysis of oriental medicine remedies (herbs, food products) was performed for 14 chemical elements. Remedies with the significantly higher and lower concentrations of particular elements (as compared to the average values) were identified. An attempt was made to find possible correlations between distribution of elements in remedies and oriental medicine parameters and absence of such correlation was found.     

Polyoxomolybdate368 /polyaniline nanocomposite as a novel fiber for solid‐phase microextraction of antidepressant drugs in biological samples

A novel solid‐phase microextraction fiber was synthesized by coating a stainless steel wire with polyoxomolybdate₃₆₈/polyaniline as a sorbent aimed at extraction of amitriptyline, nortriptyline, and doxepin as antidepressant drugs from urine and blood samples. The polyoxomolybdate₃₆₈/polyaniline composite coating was applied using electropolymerization process under constant potential. This composition leads to enhanced extraction efficiency of the fiber. Scanning electron microscopy images show that huge three‐dimensional structures of polyoxomolybdate₃₆₈ in composite induced more non‐smooth and porous fiber. In order to optimize of the extraction process, a series of variables including concentration of the composite materials, coating thickness, pH, extraction time, salt addition, and stirring rate was investigated and optimum conditions were determined. Analysis of surface morphology and chemical composition was performed. High‐performance liquid chromatography was used for separation and evaluation of mentioned antidepressant drugs from the matrixes. The experiments indicated a detection limits of <0.2 ng/L and a linear dynamic range of 0.3–100 ng/L (R² > 0.994). The relative recovery values were found to be in the range of 92–98%. It was concluded that the purposed fiber is highly efficient in analyzing traces of antidepressant drugs in urine and blood.     

Oxalic acid as a simple and efficient organocatalyst for three-component synthesis ofα-amino nitriles

A simple,efficient,and general method has been developed for the synthesis ofα-amino nitriles.Oxalic acid as a BrФnsted acid promotes the addition of TMSCN to various imines(generated in situ).     

Effect of pulse Nd-YAG laser beam interaction on annealing of nanopowder ITO using spin-on-glass

The effect of pulse Nd-YAG laser on structural and electrical properties of ITO thin film on glass by spin coating process was evaluated. It was found that the beam interaction of pulse laser energy has a significant effect on crystallization, conductivity and optical properties of ITO. Laser irradiation with a wavelength of 1,064 nm and energy of 8–40 J are employed. The conventional X-Ray diffraction studies show the peak intensities of (211), (222), and (440) planes increased by using Nd-YAG laser treatment and prove the crystallization of ITO nanoparticle. Due to absorption of millisecond pulse laser, the resistivity of ITO coating on glass substrate which was annealed at 350 °C, reduced by a factor of 100, and a resistance of less than 0.6 kΩ has been achieved.