Antimicrobial Activity and Physical Characterization of Silver Nanoparticles Green Synthesized Using Nitrate Reductase from Fusarium oxysporum

Nanostructures from natural sources have received major attention due to wide array of biological activities and less toxicity for humans, animals, and the environment. In the present study, silver nanoparticles were successfully synthesized using a fungal nitrate reductase, and their biological activity was assessed against human pathogenic fungi and bacteria. The enzyme was isolated from Fusarium oxysporum IRAN 31C after culturing on malt extract-glucose-yeast extract-peptone (MGYP) medium. The enzyme was purified by a combination of ultrafiltration and ion exchange chromatography on DEAE Sephadex and its molecular weight was estimated by gel filtration on Sephacryl S-300. The purified enzyme had a maximum yield of 50.84 % with a final purification of 70 folds. With a molecular weight of 214 KDa, it is composed of three subunits of 125, 60, and 25 KDa. The purified enzyme was successfully used for synthesis of silver nanoparticles in a way dependent upon NADPH using gelatin as a capping agent. The synthesized silver nanoparticles were characterized by X-ray diffraction, dynamic light scattering spectroscopy, and transmission and scanning electron microscopy. These stable nonaggregating nanoparticles were spherical in shape with an average size of 50 nm and a zeta potential of ?34.3. Evaluation of the antimicrobial effects of synthesized nanoparticles by disk diffusion method showed strong growth inhibitory activity against all tested human pathogenic fungi and bacteria as evident from inhibition zones that ranged from 14 to 25 mm. Successful green synthesis of biologically active silver nanoparticles by a nitrate reductase from F. oxysporum in the present work not only reduces laborious downstream steps such as purification of nanoparticle from interfering cellular components, but also provides a constant source of safe biologically-active nanomaterials with potential application in agriculture and medicine.     

Efficient removal of heavy metal ions using hydrophilic thiacalix[4]arene doped polyaniline prepared by emulsion polymerization: conductivity,isotherm and kinetic study

The adsorption capacity of conductive polyaniline doped by thiacalix[4]arene tetrasulfonate (PANI–TCAS) towards Cu(II), Cd(II), Co(II) and Cr(III) was investigated through batch adsorption techniques, and the extent of adsorption was measured as a function of pH, initial metal ion concentration and contact time. It was found that the metal ion removal reached maximum at pH 8.0 and remained constant after 60 min. Experimental data was fitted to Langmuir, Freundlich, Redlich–Peterson and Temkin equation models with the maximum adsorption capacity calculated to be 833.3, 555.5, 526.3 and 500 for Cr³⁺, Cu²⁺, Co²⁺ and Cd²⁺, respectively, from the Langmuir isotherm model. The kinetic study was carried out through pseudo‐first‐order, pseudo‐second‐order, Elovich kinetic and intraparticle diffusion models in which the related correlation coefficient for each kinetic model showed that the pseudo‐second‐order rate equation was better described by the adsorption process. XRD spectra, SEM and TEM images of the adsorbent revealed a homogeneous distribution of nano‐sized particle structure with a porous surface, the morphology of which brings about high adsorption capacity for the PANI–TCAS molecular nanocomposite which in turn was observed by the AFM micrograph. The conductivity of thiacalix[4]arene tetrasulfonate doped polyaniline after metal ion adsorption was also assessed, and the four‐probe measurement technique revealed conductivity increment as high as 102.4 S cm^?1 with a 100 order of magnitude enhancement. Copyright © 2015 John Wiley & Sons, Ltd.     

Water Expandable Polystyrene-Organoclay Nanocomposites: Role of Clay and Its Dispersion State

A published process for preparing expandable polystyrene containing water as a blowing agent was applied to synthesize water expandable polystyrene-organoclay nanocomposites (WEPS-OCN). Organoclay was uniformly dispersed in styrene monomer. During suspension polymerization, water was trapped in the polystyrene (PS) matrix through the use of starch, ending up with spherical PS-organoclay beads. By selecting organoclays with various surfactants and modifier concentrations, different distribution states of nanoclay in the PS matrix, from cluster (poor dispersion) to either intercalated (limited dispersion) or exfoliated (full dispersion) were obtained. The incorporation of organoclay led to higher water content in the expandable beads. However, as expected, the flammability of the expanded product was increased with organoclay content. Furthermore, the results showed that the average unexpanded bead size, density of preexpanded beads, foam cell morphology, and flammability were directly influenced by the dispersion status of the organoclay. The best results were obtained when full dispersion (exfoliation) of nanoclay in PS matrix occurred.     

Novel Conductive PANI/Hydrophilic Thiacalix[4]areneNanocomposites: Synthesis,Characterization andInvestigation of Properties简

Nanocomposites of polyaniline(PANI) and the macrocycle thiacalix[4]arene tetra sulfonate(TCAS) were successfully synthesized in feed ratios of 1:0.25, 1:0.50 and 1:0.75 by three prevail synthetic methods, i.e. in situ polymerization, emulsion polymerization and solution casting technique. The structures of the nanocomposites were confirmed by FTIR, UV-Vis, XRD, SEM, and TEM techniques. The conductivity was measured by a four probe method. The conductivity was recorded to be as high as 105 × 10 2S cm 1for the nanocomposite with a nanometer size structure and homogeneously distributed morphology. The electroactivity of the nanocomposites was approved by cyclic voltammetry(CV) and impedance spectroscopy technique(EIS). The antioxidant ability and thermal property of the composites were further studied. Preliminary studies have evidenced the production of conductive nanocomposites with good thermal property and relatively good solubility in N-methyl 2-pyrrolidone(NMP), with the antioxidant activity reaching up to 80%.