Dispersion polymerization of aniline using hydroxypropylcellulose as stabilizer: role of rate of polymerization

Hydroxypropylcellulose (HPC) has been used as a steric stabilizer for preparing polyaniline dispersions using the route of oxidative dispersion polymerization of aniline. Using strongly acidic conditions (1 mol l^?1 HCl), low temperature of about 2 °C and a concentration of aniline as low as 0.5%, ammonium peroxodisulfate at 1.25% and hydroxypropylcellulose concentrations at 0.5–1 g d l^?1, unstable dispersions were obtained not only in water but also in aqueous alcohols (ethanol and methanol) up to at least 70 vol% alcohol. In contrast, dispersions that remained stable for at least 72 h were obtained when the alcohol concentration of the medium was as high as about 80 vol%. Kinetic studies of the polymerization systems suggested that success in the latter case was due to a lowering of the rate of polymerization. Transmission electron microscopy studies showed that dispersion particles prepared in 80 vol% alcohol media are spherical in shape and their diameter decreases with increasing stabilizer concentration. However, a change of morphology from spherical to aggregated needle‐shaped was observed when the rate was increased by increasing the aniline concentration from 0.5% to 0.75% g d l^?1 in the above recipe. The aggregated particles were found to be broken down to spherical nanoparticles when the as‐prepared dispersions were sonicated for about 30 min. The sonicated dispersion on drying showed the presence of fractal clusters of polyaniline particles in the dried film. The fractal dimension was determined to be 1.77 which agreed well with the theoretical value determined by computer simulation based on a diffusion limited cluster–cluster aggregation model in three dimensions. © 2001 Society of Chemical Industry     

Oxidative degradation of polyaniline during the chemical oxidative polymerization of aniline in aqueous methanol medium

The course of chemical oxidative polymerization of aniline using ammonium persulfate as the initiator in acidic (1 M HCl) aqueous methanol (30 to 70 vol%) was studied spectrophotometrically. It was found that at temperatures greater than about 10 °C the reaction leads to degradation of polyaniline, the effect being greater with increasing methanol concentration. This is quite unlike the situation in aqueous ethanol where the product is the usual emeraldine hydrochloride form of polyaniline. Copyright © 2005 Society of Chemical Industry     

Photocatalytic performance of nano-photocatalyst from TiO2 and Fe2O3 by mechanochemical synthesis

Nano-particles of homogeneous solid solution between TiO₂ and Fe₂O₃ (up to 10 mol%) have been prepared by mechanochemical milling of TiO₂ and yellow Fe₂O₃/red Fe₂O₃/precipitated Fe (OH)₃ using a planetary ball mill. Such novel solid solution cannot be prepared by conventional co-precipitation technique. A preliminary investigation of photocatalytic activity of mixed oxide (TiO₂/Fe₂O₃) on photo-oxidation of different organic dyes like Rhodamine B (RB), Methyl orange (MO), Thymol blue (TB) and Bromocresol green (BG) under visible light (300-W Xe lamp; λ > 420 nm) showed that TiO₂ having 5 mol% of Fe₂O₃ (YFT1) is 3-5 times higher photoactive than that of P25 TiO₂. The XRD result did not show the peaks assigned to the Fe components (for example Fe₂O₃, Fe₃O₄, FeO₃, and Fe metal) on the external surface of the anatase structure in the Fe₂O₃/TiO₂ attained through mechanochemical treatment. This meant that Fe components were well incorporated into the TiO₂ anatase structure. The average crystallite size and particle size of YFT1 were found to be 12 nm and 30 ± 5 nm respectively measured from XRD and TEM conforming to nanodimensions. Together with the Fe component, they absorbed wavelength of above 387 nm. The band slightly shifted to the right without tail broadness, which was the UV absorption of Fe oxide in the Fe₂O₃/TiO₂ particle attained through mechanochemical method. This meant that Fe components were well inserted into the framework of the TiO₂ anatase structure. EPR and magnetic susceptibility show that Fe³⁺ is in low spin state corresponding to μ_B = 1.8 BM. The temperature variation of μ_B shows that Fe³⁺ is well separated from each other and does not have any antiferromagnetic or ferromagnetic interaction. The evidence of Fe³⁺ in TiO₂/Fe₂O₃ alloy is also proved by a new method that is redox titration which is again support by the XPS spectrum.     

Synthesis of size-tunable gold nanoparticles by poly(vinylphenol) and electrostatic multilayer deposition of the gold-poly(vinylphenol) nanocomposites

Water-dispersible gold nanoparticles (GNPs) were synthesized by the polymer in situ redox technique at room temperature using poly(4-vinylphenol) (PVPh) as a simultaneous template/stabilizer and reducing agent. GNPs were characterized by its surface plasmon absorption peak at 536 nm. The average particle size of the gold-poly(4-vinylphenol) (Au-PVPh) nanocomposites decreases with increase in the ratio of PVPh to gold salt. A uniform multilayer of Au-PVPh nanocomposites was fabricated on glass surface by electrostatic layer-by-layer assembly using poly(diallyldimethylammonium chloride) (PDDAC) as the oppositely charged polycation. UV-vis spectra of the consecutive multilayer showed that the absorbance at 549 nm corresponding to GNPs increases linearly with the number of Au-PVPh nanocomposite layers, indicating regular bilayer growth.     

Recent advances in production and biotechnological applications of thermostable and alkaline bacterial lipases

Microbial lipases occupy a vital position with respect to their industrial applications and they are studied extensively. Thermophilic microorganisms are potential sources of thermostable alkaline lipases, which have been isolated from various natural origins. Most lipases can act in a wide range of pH and temperature, though alkaline bacterial lipases are more common. Thermostable alkaline lipases have commercial value and find applications in various industrial and biotechnological sectors such as additives in detergents, additives in food industries, environmental bioremediations and in molecular biology. The latest trend in lipase research is the development of novel and improved lipases through molecular approaches such as directed evolution and exploring natural communities by the metagenomic approach. Therefore, thermostable alkaline lipases are the enzymes of choice for many biotechnologists, microbiologists, biochemists, environmentalists and biochemical engineers. In the present review, we discuss some novel sources along with recent advances in fermentation conditions, substrate conditions and biotechnological applications of thermostable alkaline bacterial lipases. © 2013 Society of Chemical Industry     

Poloxamer and gelatin gel guided polyaniline nanofibers: synthesis and characterization

A rapid polymerization technique was successfully employed to synthesize interconnected polyaniline (PANI) nanofibers using chemical oxidative polymerization inside a soft template. The thermoreversible hydrogels of Lutrol F 127 and gelatin were used as templates where the interstices present in the hydrogel were responsible for the formation of PANI nanofibers with a diameter in the range ca 70?75 nm and ca 50?55 nm respectively and several micrometers in length. The doped emeraldine salt of PANI was confirmed by Fourier transform infrared spectroscopy and ultraviolet–visible spectroscopy. The crystallinity of as‐synthesized PANI nanofibers for both cases was verified by an X‐ray diffraction study while thermogravimetric analysis was performed to compare the relative stability of the synthesized PANI nanofibers. The electrical conductivities of polymerized PANI are of the order of 10^?3 S cm^?1 and are compared with those of template fabricated PANI. The Lutrol F 127 gel guided PANI nanofibers showed a rectifying property while the gelatin gel guided PANI provided a simple ohmic nature. © 2013 Society of Chemical Industry     

Interaction of a laser beam with the rotational lines of nitrogen in the wavelength region of 5700 A

Propagation of a dye laser beam of wavelength 5700 A through nitrogen is considered. Values of transmittance, averaged over intervals of 0.5 cm(-1), are obtained for absorber thicknesses of 0.1, 1, and 10 atm-cm, using the quasi-random model of molecular band absorption. From these values, intensities of the absorption lines in the first positive system of N(2) are simulated in the frequency interval of 17,540-17,548 cm(-1).     

将PET废料回收为纯净的聚合物

Maskara工业公司 (MIL)的名字在几年前还不为人所熟知 ,当它建了一个能将 PET聚合物废料回收并制成纯净的切片及 POY的工厂后 ,人们才开始关注它。标志着 MIL公司发展的第一个里程碑是在1 998年 ,它在孟买附近的 Murbad地区建了一个变形加工厂。 1 991年 ,该工厂的生产规模又通过添加变形和加捻设备得以扩大。公司 1 994年还成立了一个现代化的生产 PET切片和 POY的工厂 ,并在 1 998年与一个德国技术公司合作。对一个公司来说 ,其最终产品的质量是非常重要的。 MIL公司以聚酯废料为原料生产 POY,这在世界上尚属首次 ,以下将介绍…     

Iodine a Simple, Effective and Inexpensive Catalyst for the Synthesis of Substituted Coumarins

This work studies toluene abatement from gaseous streams, using gamma-Al₂O₃ supported palladium and platinum catalysts, titania and gamma-Al₂O₃ supported vanadium oxide catalysts and ZnO/Al₂O₃ supported copper oxide catalyst, characterized by textural and thermal analyses, X-ray diffraction and fluorescence. Noble metal catalysts have shown higher activity but lower selectivity toward total oxidation, with higher selectivity toward undesired products, like CO and benzene.     

Downregulation of miR-506-3p Facilitates EGFR-TKI Resistance through Induction of Sonic Hedgehog Signaling in Non-Small-Cell Lung Cancer Cell Lines

Non-small-cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR) mutation eventually develop resistance to EGFR-targeted tyrosine kinase inhibitors (TKIs). Treatment resistance remains the primary obstacle to the successful treatment of NSCLC. Although drug resistance mechanisms have been studied extensively in NSCLC, the regulation of these mechanisms has not been completely understood. Recently, increasing numbers of microRNAs (miRNAs) are implicated in EGFR-TKI resistance, indicating that miRNAs may serve as novel targets and may hold promise as predictive biomarkers for anti-EGFR therapy. MicroRNA-506 (miR-506) has been identified as a tumor suppressor in many cancers, including lung cancer; however, the role of miR-506 in lung cancer chemoresistance has not yet been addressed. Here we report that miR-506-3p expression was markedly reduced in erlotinib-resistant (ER) cells. We identified Sonic Hedgehog (SHH) as a novel target of miR-506-3p, aberrantly activated in ER cells. The ectopic overexpression of miR-506-3p in ER cells downregulates SHH signaling, increases E-cadherin expression, and inhibits the expression of vimentin, thus counteracting the epithelial–mesenchymal transition (EMT)-mediated chemoresistance. Our results advanced our understanding of the molecular mechanisms underlying EGFR-TKI resistance and indicated that the miR-506/SHH axis might represent a novel therapeutic target for future EGFR mutated lung cancer treatment.