Poly(N-vinylpyrrolidone) modified polyaniline/Na<Superscript>+</Superscript>-cloisite nanocomposite: Synthesis and characterization

A novel electrically conductive nanocomposite consisting of poly(N-vinylpyrrolidone) (PVP) modified polyaniline (PANI) and cloisite clay nanoparticles was obtained via insitu polymerization method. The synthesized nanocomposite was characterized using FT-IR, XRD, conductivity measurement and cyclic voltammetry techniques. The electrical conductivity measurements of prepared nanocomposite showed that the nanocomposite is electrically conductive. Also cyclic voltammetry studies revealed that the synthesized nanocomposite is electro active. Electrochemical corrosion studies including open circuit potential measurements and tafel tests were carried out in various corrosive environments to evaluate the anticorrosive property of the nanocomposite coating on iron samples. Results showed that the coating of this nanocomposite on iron was useful in decreasing corrosion current and corrosion rate of iron in comparison with bare iron and pure polyaniline coated samples. A positive shift in corrosion potential and a significant decrease in corrosion current were observed for nanocomposite coated iron samples in sodium chloride 3.5 %, hydrochloric acid 0.1 M and sulfuric acid 0.1 M solutions.     

Immobilization of Cationic Titanium Dioxide (TiO<Subscript>2</Subscript><Superscript>+</Superscript>) on Electrospun Nanofibrous Mat: Synthesis,Characterization, and Potential Environmental Application

We report a facile approach to fabrication and characterization of cationic titanium dioxide (TiO₂⁺) on poly (vinyl alcohol)/poly (acrylic acid) (PVA/PAA) composite electro-spun nanofibrous mat. The aim of this study is to develop a “functional electrospun nanofibrous mat” as a sustainable approach to superior photocatalytic degradation of organic colorants. For that, the PVA/PAA nanofibrous mat was prepared by electrospinning of PVA and PAA solution according to an aspect ratio of 1:1 and later water stability was induced by the thermal cross linking at an elevated temperature of 145 °C for 30 minute. By means of electrostatic layer-by-layer (LbL) assembly, cationic titanium dioxide (TiO₂⁺, ~19 nm) was immobilized on the surface of the water stable nanofibrous mat. As functionalized composited nanofibrous mat was characterized by using scanning electron microscope (SEM), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) analysis and thermogravimetric analysis (TGA). Superior competency of the functionalized nanofibrous mat towards photocatalytic degradation of organic dye (methyl blue) in aqueous solution was observed by using UV-visible spectrophotometer with quantitative measuring method. The result indicates a complete degradation of methyl blue within 40 mins and superior reusability upto 5 cycles application. The study signifies the prospect of using electrospun nanofibers to manipulate the catalytic activity, which could be a foundation for further rational design of various composite nanofibrous materials.     

Multifunctional modification of wool fabric using graphene/TiO<Subscript>2</Subscript> nanocomposite

In this study, a new finishing technique is introduced through treatment of wool fabric with graphene/TiO₂ nanocomposite. Graphene oxide/titanium dioxide nanocomposite first applied on the wool fabric by hydrolysis of titanium isopropoxide in graphene oxide suspension and then this coating chemically converted by sodium hydrosulfite to graphene/TiO₂ nanocomposite. The homogenous distribution of the graphene/TiO₂ nanocomposite on the fiber surface was confirmed by field emission scanning electron microscopy (FE-SEM), Energy-dispersive X-ray spectroscopy (EDS) and X-ray mapping. X-ray diffraction patterns proved the presence of titanium dioxide nanoparticles with a crystal size of 127 Å on the treated wool fabric. Also, the defect analysis based on X-ray photoelectron spectroscopy (XPS) established the composition of the nanocomposite. Other characteristics of treated fabrics such as antibacterial activity, photo-catalytic self-cleaning, electrical resistivity, ultraviolet (UV) blocking activity and cytotoxicity were also assessed. The treated wool fabrics possess significant antibacterial activity and photo-catalytic self-cleaning property by degradation of methylene blue under sunlight irradiation. Moreover, this process has no negative effect on cytotoxicity of the treated fabric even reduces electrical resistivity and improves UV blocking activity.     

SiO2-kaolinite affecting the surface properties of ternary poly(vinyl chloride)/silica/kaolinite nanocomposites

The products from the dispersion of nanoscale particulates such as the layered clays or the spherical inorganic minerals within the polymeric matrices are called polymeric nanocomposites. In this paper, we prepared poly(vinyl chloride) (PVC) based nanocomposites containing SiO₂-kaolinite by melt compounding. The influence of SiO₂-kaolinite on the surface properties of PVC was investigated by the use of various surface analysis techniques including a ttenuated total reflectance spectroscopy (ATR), wide angle X-ray diffractometry (WAXD), atomic force microscopy (AFM), scanning electron microscopy (SEM), electron dispersive X-ray spectrometer (EDX), contact angle measurement (CAM), and reflectance spectroscopy (RS). ATR spectroscopy showed possible interaction between layered kaolinite and PVC at surface. Microscopic methods illustrated an increased surface roughness compared to the pure PVC. Contact angle measurements of the resultant PVC nanocomposites demonstrated that the wettability of substrates depends on the surface interactions between kaolinite layers and PVC matrix. Optical properties of nanocomposite films were finally measured by the aid of reflectance spectrophotometer. It can be seen from optical studies that reflectance values were increased after incorporation of SiO₂-kaolinite in nanocomposite.     

Mechanical and moisture absorption characterization of PLA composites reinforced with nano-coated flax fibers

This research is intended to improve the interface between the fibers and the matrix and limit water absorption of bio-based material thereby decreasing degradation of the composites when they are exposed to external environment such as high temperature and humidity. In this study, flax fibers were treated with an organic surface coating containing SiO₂ nanoparticles. This coating was a dispersion of silica fume in epoxy. One composite was also made with raw fibers as reference as well as one sample of pure PLA. Flax fibers/PLA composites were manufactured by hot pressing by stacking 4 PLA films and 3 pieces of flax fabric. Morphology and dispersion of the coating on the fibers was observed by scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Accelerated ageing was carried out on the 3 materials by placing them in a 50 °C water bath until saturation to investigate the influence of the coating on water diffusion. Mechanical properties of the different composites were investigated by tensile (before and after conditioning) and short beam shear (SBS) testing in order to evaluate the impact of the coating on the interfacial properties of the materials. The results show that the fibers surface was homogenized and that a better adhesion was reached because of the coating. Coating the fibers also allowed the decrease in water uptake by more than 10 % and their protection during conditioning, preserving their mechanical properties.     

Influence of natural clinoptilolite nanoparticles on thermal stability,scratch resistance and adherence properties of Acrylonitrile butadiene styrene (ABS)

In order to improve thermal stability of Acrylonitrile-butadiene-styrene (ABS) polymer, ABS/natural clinoptilolite (Clino) nanocomposite was produced using solvent/non-solvent method. The influence of natural clinoptilolite nanoparticles on scratch resistance and adherence properties of ABS coating on steel coupons was investigated. In order to study the scratch resistance and adherence properties, thin (20 µm) coatings of ABS and ABS/Clino nanocomposites, were prepared by solution casting method. The formation of ABS/Clino nanocomposite was characterized using FTIR spectroscopy, X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM). Results showed that there is a strong interaction such as hydrogen bonding between ABS and clinoptilolite nanoparticles. The thermal stability of the nanocomposite was examined using thermogravimetric analysis (TGA). TGA results showed an increase in the thermal degradation temperature of the nanocomposite. TGA results indicated that the thermal stability of ABS increases by increasing the Clino content of nanocomposite up to 5 % w/w. Scratch resistance and adherence properties of ABS/Clino nanocomposite coatings were also evaluated. Results showed that the scratch resistance and adherence strength of ABS/Clino nanocomposite coatings are higher than that of pure ABS coatings.     

Influences of organic-modified Fe-montmorillonite on structure, morphology and properties of polyacrylonitrile nanocomposite fibers

The Fe-montmorillonite (Fe-MMT) combined catalysis effects of Fe ion with barrier effects of silicate clays, was firstly synthesized by hydrothermal method, and then was modified by cetyltrimethyl ammonium bromide (CTAB). The organic-modified Fe-montmorillonite (Fe-OMT) was dispersed in the N, N-dimethyl formamide (DMF) and then compounded with polyacrylonitrile (PAN) solution which was dissolved in DMF. The composite solutions were electrospun to form PAN/Fe-OMT nanocomposite fibers. The influences of the Fe-OMT on the structure, morphology, thermal, flammability and mechanical properties of PAN nanocomposite fibers were respectively characterized by X-ray diffraction (XRD), High-resolution transmission electron microscopy (HRTEM), Scanning electron microscopy (SEM), Thermogravimetric analyses (TGA), Micro Combustion Calorimeter (MCC) and Electronic Single Yarn Strength Tester. It was found from XRD curves that there was not observable diffraction peak of silicate clay, indicating that the silicate clay layers were well dispersed within the PAN nanofibers. The HRTEM image indicated that the multilayer stacks of nanoclays could be found within the nanofibers and were aligned almost along the axis of the nanofibers. The SEM images showed that the diameters of nanocomposite fibers were decreased with the loading of the Fe-OMT. The TGA analyses revealed that the onset temperature of thermal degradation and charred residue at 700°C of PAN nanocomposite fibers were notably increased compared with the pure PAN nanofibers, contributing to the improved thermal stability properties. It was also observed from MCC analyses that the decreased peak of heat release rate (PHRR) of the PAN nanocomposite fibers reduced the flammability properties. The loadings of Fe-OMT increased the tensile strength of PAN nanocomposite fibers, but the elongation at break of PAN nanocomposite fibers was lower than that of the PAN nanofibers.     

Na+/K+-ATPase Activation by cAMP in the Midgut of Lutzomyia longipalpis (Lutz & Neiva, 1912; Diptera: Psychodidae)

Lutzomyia longipalpis (Lutz & Neiva, 1912) females have been intensively studied regarding the regulation of midgut pH. The mechanisms involved in pH regulation are complex, and some aspects remain to be clarified. Here, we investigated the role of the Na⁺/K⁺-ATPase pump as an electrochemical potential generator and its modulation by the second messenger cAMP in the midgut of female L. longipalpis. Our results suggest that not only may Na⁺/K⁺-ATPase be the main generator of an electrochemical potential across membranes in the midgut of female L. longipalpis, but also its activity is positively regulated by cAMP. cAMP-mediated Na⁺/K⁺-ATPase pump activity might be necessary to maintain the transport of the nutrients produced during blood digestion.     

Preparation and properties of polypropylene nanocomposites reinforced with exfoliated graphene

We have prepared a series of polypropylene/exfoliated graphene (PP/EG) nanocomposite films via efficient meltcompounding and compression, and investigated their morphology, structures, thermal transition behavior, thermal stability, electrical and mechanical properties as a function of EG content. For the purpose, EG, which is composed of disordered graphene platelets as reinforcing nanoscale fillers, is prepared by the oxidation/exfoliation process of natural graphite flakes. SEM images and X-ray diffraction data confirm that the graphene platelets of EG are well dispersed in PP matrix for the nanocomposites with EG contents less than 1.0 wt%. It is found that thermo-oxidative degradation of PP/EG nanocomposites is noticeably retarded with the increasing of EG content. Electrical resistivity of the nanocomposite films was dramatically changed from ∼10¹⁶ to ∼10⁶ Ω·cm by forming electrical percolation threshold at an certain EG content between 1 and 3 wt%. Tensile drawing experiments demonstrate that yielding strength and initial modulus of PP/EG nanocomposite films are highly improved with the increment of EG content.     

Development of Maghemite Glass Fibre Nanocomposite for Adsorptive Removal of Methylene Blue

Maghemite glass fibre nanocomposite with excellent magnetic and adsorption properties was successfully developed from nontoxic and eco-friendly reagents by thermal decomposition approach. The developed nanocomposite was utilized in adsorption of methylene blue which follows Freundlich adsorption isotherm. The excellent value of adsorption capacity (51.31 mg g^-1) as compared to other adsorbents recommends its potential role for adsorption phenomenon in multiple applications. The developed nanocomposite can be recycled and reused easily. Surface and other functional characteristics of developed nanocomposite were determined through scanning electron microscopy, X-ray diffraction, raman spectroscopy, energy dispersive X-ray spectroscopy and vibrating sample magnetometer. The obtained results revealed that maghemite glass nanocomposite is a potential tool that can be utilized in waste water treatments.     

盐胁迫下钾吸收途径的抑制对小麦叶片K~+、Na~+含量的影响

为研究盐胁迫下小麦维持钾、钠平衡的生理机制,以耐盐小麦沧麦6005和盐敏感小麦矮抗58为材料,利用TEA、NEM、Ba(NO_3)_2三种药物分别抑制钾离子通道、钾载体及非选择性阳离子通道,测定正常及盐胁迫下小麦叶片K~+、Na~+含量,比较耐盐性不同的小麦品种在K~+、Na~+吸收中的差异。结果显示,盐胁迫下,沧麦6005和矮抗58叶片K~+含量下降,Na~+含量增加;沧麦6005叶片Na~+含量低于矮抗58,K~+/Na~+比值高于矮抗58。正常条件下,NEM、TEA处理均可降低沧麦6005和矮抗58叶片K~+含量,NEM处理较TEA处理效果更为明显;TEA处理显著降低了盐胁迫下矮抗58叶片K~+含量,而NEM处理则明显降低了盐胁迫下沧麦6005的叶片K~+含量;TEA、NEM、Ba(NO_3)_2处理降低了盐胁迫下矮抗58叶片Na~+含量,仅NEM处理降低了沧麦6005叶片Na~+含量。综上所述,正常条件下,钾载体是小麦K~+吸收的主要方式;盐胁迫下,耐盐品种和盐敏感品种K~+吸收途径不同,耐盐品种的NSCCs和钾离子通道具有更强的"拒钠"能力。     

Electrospinning and microwave absorption of polyaniline/polyacrylonitrile/multiwalled carbon nanotubes nanocomposite fibers

Electrical conductive nanocomposite fibers were prepared with polyaniline (PANI), polyacrylonitrile (PAN) and multi-walled carbon nanotubes (MWCNTs) via electrospinning. The morphology and electrical conductivity of the PANI/PAN/MWCNTs nanocomposite fibers were characterized by scanning electron microscope (SEM) and Van De Pauw method. Electrical conductivity of nanocomposite fibers increased from 1.79 S·m^?1 to 7.97 S·m^?1 with increasing the MWCNTs content from 3.0 wt% to 7.0 wt%. Compared with PANI/PAN membranes, the mechanical property of PANI/PAN/MWCNTs nanocomposites fiber membranes decreased. The microwave absorption performance of composite films was analyzed using waveguide tube, which indicated that with the thickness increasing the value of R_L reduced from ?4.6 to ?5.9 dB.     

Eco-friendly biopolymer/clay/conducting polymer nanocomposite: Characterization and its application in reactive dye removal

In this study starch-montmorillonite/polyaniline (St-MMT/PANI) nanocomposite was synthesized by chemical oxidative polymerization of aniline in the presence of starch-montmorillonite nanocomposite dispersion. The prepared ternary nanocomposite was characterized using FT-IR, XRD, SEM, TGA and TEM techniques. XRD patterns combined with TEM results confirmed the intercalation of MMT in the starch matrix. SEM micrographs revealed the growth of polyaniline over the surface of the St-MMT nanocomposite. The St-MMT/PANI nanocomposite was used for the adsorption of a reactive dye. Batch removal experiment results showed complete removal of dye in a very short contact time. Further investigations indicated that the removal mechanism was based on both the adsorption and electrostatic attraction between nanocomposite and dye molecules. The experimental data were well fitted to the Langmuir isotherm and pseudo-second-order kinetic model. The adsorption capacity of reactive dye on St-MMT/PANI nanocomposite was 91.74 mg g^?1. All these results demonstrated the effectiveness of the hybrid system as an efficient adsorbent for removal of reactive dyes from textile effluents.     

A rapid quantification method for tissue Na+ and K+ concentrations in salt-tolerant and susceptible accessions in Vigna vexillata (L.) A. Rich.

A rapid quantification method for leaf sodium (Na⁺) and potassium (K⁺) concentrations was developed using a compact ion meter. Leaf ion concentrations were evaluated for species of Vigna vexillata (L.) A. Rich. after two weeks of treatment with 0–200 mM of sodium chloride. To compare the ion extraction efficiency, extraction solutions of distilled water and ammonium acetate were tested. The ion concentrations of extracts obtained by both solutions were measured using an ion meter, and the values were validated using ion chromatography. For both extraction solutions, the ion meter values were highly correlated with those of the ion chromatograph. However, correlations between ion meter and chromatograph values were largely different for Na⁺ and K⁺. The rapid quantification of ion concentrations using an ion meter developed in this study was successfully utilized for evaluating differences in leaf Na⁺ concentrations, K⁺ concentrations, and K⁺/Na⁺ ratio in species of V. vexillata.     

Copper oxide-carbon nanotube (CuO/CNT) nanocomposite: Synthesis and photocatalytic dye degradation from colored textile wastewater

In this paper, CuO/CNT nanocomposite was synthesized and its photocatalytic dye degradation ability for colored textile wastewater was studied. The characteristics of the nanocomposite were investigated by XRD, SEM and FTIR. The photodegradation of Direct Red 31 (DR31) and Reactive Red 120 (RR120) by CuO/CNT in presence of H₂O₂ was investigated. Photocatalytic dye degradation was determined by UV-vis spectrophotometer. Effects of catalyst dosage, initial dye concentration and salt on photodegradation performance were studied. The photocatalytic dye degradation ability of pure CuO and CuO/CNT nanocomposite is 78 % and 89 % for DR31 and 70 % and 87 % for RR120, respectively. The results showed that CNT increased the photocatalytic activity of CuO. The presence of salt decreases dye degradation efficiency. The dye degradation kinetics by nanocomposite followed first-order kinetic model. The reaction rate at 0.005 g catalyst was 0.0137 and 0.0105 min^-1 for DR31 and RR120, respectively. It was found that the CuO/CNT nanocomposite as a photocatalyst could be used to degrade dyes from colored wastewater.     

Degradation and rheological properties of biodegradable nanocomposites prepared by melt intercalation method

Biodegradable nanocomposites were prepared by mixing a polymer resin and layered silicates by the melt intercalation method. Internal structure of the nanocomposite was characterized by using the small angle X-ray scattering (SAXS) and transmission electron microscope (TEM). Nanocomposites having exfoliated and intercalated structures were obtained by employing two different organically modified nanoclays. Rheological properties in shear and extensional flows and biodegradability of nanocomposites were measured. In shear flow, shear thinning behavior and increased storage modulus were observed as the clay loading increased. In extensional flow, strain hardening behavior was observed in well dispersed system. Nanocomposites with the exfoliated structure had better biodegradability than nanocomposites with the intercalated structure or pure polymer.     

Vertical Distribution of Sodium in Roots of Rice Plants Exposed to Salinity as Analyzed by Cryo Time-of-Flight Secondary Ion Mass Spectrometry

Abstract

Distribution of Na⁺ along the root axis under salinity stress was analyzed in two rice (Oryza sativa L.) cultivars with different salt resistance (salt-sensitive IR 24 and salt-resistant Pokkali). Rice plants were grown hydroponically and NaCl was applied with nutrient solution at concentrations of 0, 25 and 50 mM for 7 d after germination. The distribution of Na⁺ in roots under salinity was analyzed by the cryo time-of-flight secondary ion mass spectrometry (cryo TOF-SIMS). The Na⁺ content in the root was higher in salt-sensitive IR 24 than in salt-resistant Pokkali under NaCl stress. The content was highest at the root tip and was decreased basipetally along the root axis. The difference in Na⁺ content between the cultivars was apparent in all regions from the root tip.     

The Protection of Polysaccharide from the Brown Seaweed Sargassum graminifolium against Ethylene Glycol-Induced Mitochondrial Damage

The aim of the present study is to evaluate the protective effect of polysaccharide from the Brown Seaweed Sargassum graminifolium (SGP) on ethylene glycol-induced kidney damage and the mechanism of SGP-mediated protection. Mitochondrial lipid peroxidation, mitochondrial swelling, the activity of succinate dehydrogenase (SDH), ATPases and mitochondrial antioxidant enzymes was observed in hyperoxaluric rats. Administration of SGP (25, 100 and 400 mg·kg⁻¹, intragastrically) increased the activities of antioxidant enzymes, SDH and Na⁺/K⁺-ATPases, Ca²⁺-ATPases, Mg²⁺-ATPases, also decreased mitochondrial lipid peroxidation and mitochondrial swelling. SGP exhibited a protective effect by improving antioxidant enzymes and restoring mitochondrial dysfunction in the kidney of hyperoxaluric rats. It may be used as a promising therapeutic agent to provide superior renal protection.     

Differential Sensitivity of Rice Cultivars to Salinity and Its Relation to Ion Accumulation and Root Tip Structure

Abstract

Effects of NaCl on the growth, ion content, root cap structure and Casparian band development were examined in four rice (Oryza sativa L.) cultivars with different salt resistance (salt-sensitive indica-type IR 24 and japonica-type Nipponbare and salt-resistant indica-type Nona Bokra and Pokkali). Experiments were conducted to find the differences in salinity resistance during early seedling and developed seedling stages among the cultivars. For salinity treatment, sodium chloride (NaCl) was added to nutrient solution at concentrations of 0, 25 and 50 mM for 7 days from germination to the 7th day (early seedling stage) or from the 7th day to 14th day (developed seedling stage). Growth inhibition by salinity was more prominent in the early seedling stage than in the developed seedling stage. Based on the growth, the order of the sensitivity was IR24 > Nipponbare > Nona Bokra > Pokkali. The growth of NaCl-treated rice cultivars relative to control was significantly and negatively correlated with the Na⁺ content and Na⁺/K⁺ ratio in roots and shoots in both stages. Scanning electron microscopic observation revealed that the root cap tissues proliferated and extended to the basal part of the root tip by salinity. The length of root cap was, however, reduced by 50 mM NaCl in sensitive cultivars due to peeling off. An endodermal Casparian band was formed in the basal region of the root tip. Development of the Casparian band was more prominent in sensitive cultivars than in tolerant cultivars. Root cap proliferation might be related to NaCl resistance in rice seedlings, but the Casparian band may not function efficiently in Na⁺ exclusion. Essentially the present results suggest that exclusion of Na⁺ from roots plays a critical role in expression of Na⁺ resistance in rice seedlings and the root cap is important for Na⁺ exclusion.     

Synthesis of Ag-Loaded TiO<Subscript>2</Subscript> Electrospun Nanofibers for Photocatalytic Decolorization of Methylene Blue

Titanium dioxide (TiO₂) is one of the excellent photocatalysts used for degradation of environmetal pollutants. In this work, 2.5, 5.0 and 7.5 wt.% of silver (Ag)-loaded TiO₂ nanofibers of mean size 52–134 nm were synthesized by electrospinning method. These electrospun nanofibers were calcined at 500 °C to enable the transformation of Rutile (R) phase to Anatase (A), elimination of reaction moieties from the TiO₂ matrix and subsequently formation of Ag clusters. The effect of Ag loading on the morphology, crystal structure, phase transformation, and band gap of these electrospun nanofibers have been characterized by scannining electron microscopy (SEM), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), raman spectroscopy and UV-visible spectroscopy. These nanofibers exhibited a red-shift in the absorbance edge and a significant enhancement of light absorption in the wavelength range of 250–550 nm. These electrospun nanofibers were investigated for photodecomposition of methylene blue (MB), and photocatalytic decolorization rates were determined by pseudo-first-order equation. The rate constants for the pure and those of 2.5, 5.0, and 7.5 wt% Agloaded TiO₂ nanofibers were computed to be 0.1439 min^-1, 0.1608 min^-1, 0.1876 min^-1, and 0.2251 min^-1 respectively.