Edge‐functionalized graphene nanoplatelets with polystyrene by atom transfer radical polymerization: grafting through carboxyl groups

The surface modifier 3‐((4‐hydroxybutoxy)dimethylsilyl)propyl methacrylate (CD), which contains a double bond and a hydroxyl group, was synthesized through a coupling reaction of 1,4‐butanediol and (3‐methacryloxypropyl)dimethylchlorosilane. Subsequently, graphene oxide (GO) was functionalized with different amounts of CD from its edge carboxyl groups. Then, grafting through atom transfer radical polymerization of styrene in the presence of various amounts of the edge‐functionalized GO was carried out to evaluate the effect of graphene loading along with graft density. A peak at 3.8 ppm in the ¹H NMR spectrum of CD associated with the methylene adjacent to the Si–O group indicated a successful coupling reaction. Attachment of CD on the edges of GO was evaluated using X‐ray photoelectron and Fourier transform infrared spectroscopies. Expansion of GO interlayer spacing by functionalization was evaluated using X‐ray diffraction. The ordered and disordered crystal structure of carbon was studied using Raman spectroscopy. The close I_D/I_G values for GO and various kinds of functionalized graphenes show the preserved graphitic crystallite size. Relaxation behaviour of polystyrene chains in the presence of graphene nanoplatelets and also the effect of graft content on chain confinement were studied using differential scanning calorimetry. High‐graft‐density nanocomposites show higher glass transition temperatures. Morphology of graphene nanoplatelets was studied using scanning electron and transmission electron microscopies. The flat and smooth morphology of graphene nanoplatelets is disturbed and also the transparency of the nanoplatelets decreases during the oxidation and functionalization processes. © 2014 Society of Chemical Industry     

Effects of metal source in metal substitution of lithium manganese oxide spinel

Usefulness of W substitution for improvement of battery performance of LiMn₂O₄ cathode was investigated. Small amounts of tungsten were incorporated into LiMn₂O₄ spinel instead of available Mn. For this purpose, two sources of tungsten (metallic W or WO₃) were examined. W concentration and source have significant influence on both morphology and electrochemical behavior of W-substituted LiMn₂O₄ spinels. W substitution of LiMn₂O₄ spinel can lead to the formation of uniform spinel particles and improved battery performance. Cyclic voltammetric behaviors of the samples were examined in an aqueous solution, and Li diffusion process was investigated for different cases. The best case was the LiW_0.01Mn_1.99O₄ spinel prepared from metallic W powder, as exhibits excellent rate capability, but better cycleability was observed for the LiW_0.01Mn_1.99O₄ spinel prepared from WO₃. This means that because of significant influence of the dopant source, this parameter should be chosen in respect with the desire improvement.     

Effect of Chemical Composition of Tetraethoxysilane and Trimethoxy(Propyl)Silane Hybrid Sol on Hydrophobicity and Corrosion Resistance of Anodized Aluminum

Silicon - The current study indicates the application of three different range of hybrid sols on substrates. The aim was to achieve an optimum chemical composition on the silane- treated surface in...     

Carbon nanotube and its applications in textile industry – A review

One of the major components of nanotechnology is Carbon nanotube (CNT) that can have a length-to-diameter ratio more than 1,000,000. They are used in several fields in material science, due to their exceptional electrical, mechanical, and thermal properties, which are anisotropic. Different techniques have been developed to produce CNT. They have good potential for applications in various technological areas such as nanoelectronic, biotechnology, material science, polymer, composite, and textile industries. In this paper, recent researches on application of CNT in textile industry are reviewed. Treatment of textiles with CNT leads to the production of a wide variety of conductive textiles with different electrical properties. The wear performances of fabrics apply with CNT to open the potentiality of producing composite materials for conventional and innovative applications, ranging from conventional apparel and sportswear to protective clothing, heating equipment, automotive textiles, building covering, geo-textiles, biomedical textiles, etc.     

Noble metal (Pd, Ru, Rh, Pt, Au, Ag) doped graphene hybrids for electrocatalysis

Metal decorated graphene materials are highly important for catalysis. In this work, noble metal doped-graphene hybrids were prepared by a simple and scalable method. The thermal reductions of metal doped-graphite oxide precursors were carried out in nitrogen and hydrogen atmospheres and the effects of these atmospheres as well as the metal components on the characteristics and catalytic capabilities of the hybrid materials were studied. The hybrids exfoliated in nitrogen atmosphere contained a higher amount of oxygen-containing groups and lower density of defects on their surfaces than hybrids exfoliated in hydrogen atmosphere. The metals significantly affected the electrochemical behavior and catalysis of compounds that are important in energy production and storage and in electrochemical sensing. Research in the field of energy storage and production, electrochemical sensing and biosensing as well as biomedical devices can take advantage of the properties and catalytic capabilities of the metal doped graphene hybrids.     

In situ atom transfer radical polymerization of styrene to in-plane functionalize graphene nanolayers: grafting through hydroxyl groups

We report synthesis of a novel diamine 1,2-bis(4-(Hydrazonomethyl)phenoxy)ethane (bis- HPE) and a derived novel polyimide. The diamine was reacted with PMDA and ODA to synthesize copolyimide. Unmodified and modified silica particles were dispersed in the polyimide to prepare polyimide-silica hybrids: (a) unmodified (PSH-UM), and (b) modified (PSH-M). The PSH-UM were prepared by generating silica particles in situ in PI. In PSH-M, structural group identical to PI, 2,6- bis(3-(triethoxysilyl)propyl)pyrrolo[3,4-f]isoindole-1,3,5,7(2H,6H)-tetraone was introduced into silica nano-particles. The structural similarity enhanced compatibility between organic–inorganic components by like-like chemical interactions as both contain flexible alkyl groups. PSH-M have shown improved surface smoothness, hydrophobicity and thermal stability. Such properties are mandatory for stable coatings. The structure of silica and PI was affirmed by FTIR, EDX, and solid-state 29Si NMR spectroscopy. Morphological and thermal properties of the prepared PI-SiO₂ nano-composites were investigated by field emission scanning electron microscopy, atomic force microscopy, contact angle measurement and thermogravimetric analysis.     

Lithium perchlorate promoted highly regioselective ring opening of epoxides under solvent-free conditions

A simple and efficient synthesis of diol diesters, protected chlorohydrins, chlorohydrins and β-hydroxy azides with acetyl or benzoyl, TMSN₃ and TMSCl groups has been achieved by ring opening of epoxides with acetic anhydride, acetyl chloride or benzoyl chloride and TMSN₃ using catalytic amount of lithium perchlorate under solvent-free conditions. All reactions proceeded in short times and afforded the corresponding products in good to excellent yields under mild reaction conditions. LiClO₄ shows enhanced reactivity for the ring opening of epoxides under solvent-free conditions, therefore, reducing the reaction times dramatically and improved the yields and amount of catalyst.     

Macronutrients, vitamins and minerals intake and risk of esophageal squamous cell carcinoma: a case-control study in Iran

Background

Although Iran is a high-risk region for esophageal squamous cell carcinoma (ESCC), dietary factors that may contribute to this high incidence have not been thoroughly studied. The aim of this study was to evaluate the effect of macronutrients, vitamins and minerals on the risk of ESCC.

Methods

In this hospital-based case-control study, 47 cases with incident ESCC and 96 controls were interviewed and usual dietary intakes were collected using a validated food frequency questionnaire. Data were modeled through unconditional multiple logistic regression to estimate odds ratios (OR) and 95% confidence intervals (CI), controlling for age, sex, gastrointestinal reflux, body mass index, smoking history (status, intensity and duration), physical activity, and education.

Results

ESCC cases consumed significantly more hot foods and beverages and fried and barbecued meals, compared to the controls (p < 0.05). After adjusting for potential confounders, the risk of ESCC increased significantly in the highest tertiles of saturated fat [OR:2.88,95%CI:1.15-3.08], cholesterol [OR:1.53, 95%CI: 1.41-4.13], discretionary calorie [OR:1.51, 95%CI: 1.06-3.84], sodium [OR:1.49,95%CI:1.12-2.89] and total fat intakes [OR:1.48, 95%CI:1.09-3.04]. In contrast, being in the highest tertile of carbohydrate, dietary fiber and (n-3) fatty acid intake reduced the ESCC risk by 78%, 71% and 68%, respectively. The most cancer-protective effect was observed for the combination of high folate and vitamin E intakes (OR: 0.02, 95%CI: 0.00-0.87; p < 0.001). Controls consumed 623.5 times higher selenium, 5.48 times as much β-carotene and 1.98 times as much α-tocopherol as the amount ESCC cases consumed.

Conclusion

This study suggests that high intake of nutrients primarily found in plant-based foods is associated with a reduced esophageal cancer risk. Some nutrients such as folate, vitamin E and selenium might play major roles in the etiology of ESCC and their status may eventually be used as an epidemiological marker for esophageal cancer in Iran, and perhaps other high-risk regions.