Interpretation of partial thermal decomposition mechanism of Dy<Subscript>2</Subscript>(SO<Subscript>4</Subscript>)<Subscript>3</Subscript>·8H<Subscript>2</Subscript>O

Partial dehydration of Dy₂(SO₄)₃·8H₂O was studied employing TG, DSC, D.C. electrical conductivity and spectroscopic techniques. The possible mechanism for the loss of water molecules (partial dehydration) was found to be random nucleation obeying Mapel equation based on TG trace. The DSC traces are supports the results of TG traces and are also utilized to understand the enthalpy changes accompanying the partial dehydration and phase transition accompanying the dehydrated samples. D.C. electrical conductivity studies are attempted to supplement these TG studies. Attempts are made to explain the structural changes accompanying dehydration on the basis of infrared spectra and X-ray diffraction and scanning electron microscopic studies.     

Preparation,characterization, and thermal studies of γ-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> and CuO dispersed polycarbonate nanocomposites

Polycarbonate with γ-Fe₂O₃ and CuO dispersions were carried out by solvent casting method to make polycarbonate-γ-Fe₂O₃ and polycarbonate-CuO composite films. These films were characterized for the molecular structure through FTIR spectroscopy and crystallinity by X-ray diffraction (XRD) measurements. The morphology of polycarbonate-γ-Fe₂O₃ was found to be different from that of polycarbonate-CuO composite films based on the scanning electron micrograph (SEM) images. The thermal traces of composites are different from that of pure polycarbonate which indicating the catalytic decomposition when compared with virgin polymer which is oxidative decomposition. An understanding of the structure, morphology, and thermal behaviour of the composite films are envisaged in the present study.     

Surface characterization and electrical behavior of polyaniline–polymannuronate nanocomposites

Conducting polyaniline‐polymannuronate (PANI‐PM) composites were synthesized via in situ deposition techniques. By dissolving different weight percentages of polymannuronate (PM) (5, 10, 15, and 25%), the oxidative polymerization of aniline was achieved through the use of ammonium persulfate as oxidant. Structural morphology, FT‐IR, and X‐ray diffraction (XRD) studies support a strong interaction between PANI and PM. The temperature‐dependent DC conductivity of PANI‐PM composites was studied within the range of 300 ≤ T ≤ 500 °K, presenting evidence for the transport properties of PANI‐PM composites. Conductivity was analyzed through Mott's equation, which leveraged the variable range hopping model in three dimensions. Parameters such as density of states at the Fermi energy, hopping energy, and hopping distance were calculated. Based on the above factors, the synthesis of PANI‐PM composites envisages the future development of biomimetic materials for the creation of a new bionanocomposite as a multicomponent and multifunctional material. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 36–45, 2009     

Extracellular biosynthesis of functionalized silver nanoparticles by strains of Cladosporium cladosporioides fungus

In the present investigation, we report the extracellular biosynthesis of silver nanoparticles (AgNP) employing the fungus Cladosporium cladosporioides. The extracellular solution of C. cladosporioides was used for the reduction of AgNO(3) solution to AgNP. The present study includes time dependent formation of AgNP employing UV-vis spectrophotometer, size and morphology by employing TEM (transmission electron microscopy), structure from powder X-ray diffraction (XRD) technique and understanding of protein-AgNP interaction from Fourier transform infrared (FT-IR) spectroscopy. The AgNP were 10-100nm in dimensions as measured by TEM images.     

A novel ZnO/reduced graphene oxide and Prussian blue modified carbon paste electrode for the sensitive determination of Rutin

Science China Chemistry - A carbon paste modified sensor based on a novel composite of zinc oxide nanoparticles deposited on reduced graphene oxide (ZnO-rGrO) and Prussian blue (PB) was drop-cast...     

Chemically modified polyaniline nanocomposites by poly(2-acrylamido-2-methyl-1-propanesulfonicacid)/graphene nanoplatelet

New conducting polyaniline (PANI) nanocomposites that were chemically modified by poly(2-acrylamido-2-methyl-1-propanesulfonicacid) (PMP) and graphene nanoplatelets (GNPs) were prepared via in situ deposition. PMP was first synthesized using GNPs, and aniline hydrochloride monomer was then polymerized in the presence of PMP-GNPs. The nanopolymer composites were characterized, and its structural morphology was analyzed via transmission electron microscopy and scanning electron microscopy. Fourier transformation infrared spectroscopy results indicate a strong interaction between PANI, PMP, and GNPs. To understand the conduction behavior of the composites, temperature-dependent DC electrical conductivity was measured between 295 K and 503 K, and the mechanism of transport properties of the new composites was analyzed by Mott’s variable range of hopping model. The PANI/PMP-GNP showed higher conductivity than pure PANI polymer. The high electrical conductivity of the nanocomposites may be useful in fabricating multifunctional materials in bulk for future technological applications.     

Microwave-assisted rapid extracellular synthesis of stable bio-functionalized silver nanoparticles from guava (<Emphasis Type="Italic">Psidium guajava</Emphasis>) leaf extract

Our research interest centers on microwave-assisted rapid extracellular synthesis of bio-functionalized silver nanoparticles of 26 ± 5 nm from guava (Psidium guajava) leaf extract with control over dimension and composition. The reaction occurs very rapidly as the formation of spherical nanoparticles almost completed within 90 s. The probable pathway of the biosynthesis is suggested. Appearance, crystalline nature, size and shape of nanoparticles are understood by UV–vis (UV–vis spectroscopy), FTIR (fourier transform infrared spectroscopy), XRD (X-ray diffraction), FESEM (field emission scanning electron microscopy) and TEM (transmission electron microscopy) techniques. Microwave-assisted route is selected for the synthesis of silver nanoparticles to carry out the reaction fast, suppress the enzymatic action and to keep the process environmentally clean and green.     

Microwave absorption studies of polyaniline nanocomposites encapsulating gold nanoparticles on the surface of reduced graphene oxide in the presence of 2-naphthalene sulfonic acid

Polyaniline nanocomposites containing gold nanoparticles (GNPs) attached to the surface of reduced graphene oxide (RGO) were chemically prepared using β-naphthalene sulfonic acid as a dopant. The synthesized composites were characterized using Fourier transform infrared spectroscopy and UV-vis spectroscopy, and their surface morphology and amended crystallinity were determined by scanning electron microscopy and X-ray diffraction, respectively. Further the elemental analysis was also performed to identify the synthesized polymer composites. Complex impedance measurements were performed on the composite samples in the form of films. Sheets prepared by conventional techniques were used to study the microwave absorption properties in the microwave range of 2–12?GHz, and the effects of sample thickness on the microwave absorption were investigated. Experimental results show that the electrical conductivity of the composites increases with increasing concentrations of added GNP-RGO without a percolation threshold.     

Characterization and electrical behavior of polyaniline–poly-N-isopropylacrylamide-co-acrylic acid/alumina aqueous dispersions in the presence of dodecyl benzenesulfonic acid

Polymer composites containing polyaniline–poly-N-isopropylacrylamide-co-acrylic acid/alumina (PANI–PNA/Al₂O₃) were synthesized by chemical polymerization of aniline in an aqueous solution containing dispersed PNA/Al₂O₃ in the presence of dodecylbenzene sulfonic acid (DBSA) using different wt% of Al₂O₃ (5%, 10%, 20%, and 30%). The structure and morphology of the polymer matrix were identified by scanning electron microscope (SEM) and atomic force microscope (AFM). Thermal stability and an amended crystallinity were reasserted by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and X-ray diffraction (XRD), respectively. Chemical interaction of Al₂O₃ and PANI was characterized by XPS. The enhancement of the electrical conductivity in the temperature range 293–483 K shows a semiconducting behavior with a negative temperature coefficient of resistivity (TCR). In addition, the conductivity data are characterized by three different regions with small changing jerks with increasing temperature.     

Anomalous dielectric behavior in the nematic and isotropic phases of a strongly polar–weakly polar binary system

We report permittivity studies in the isotropic liquid and anisotropic liquid crystalline (nematic or N) phases of a binary system, in which one component has molecules with a strongly polar longitudinal group, and the other has a weakly polar transverse group. The dielectric constant in the isotropic phase as well as its anisotropy in the N phase show, surprisingly, an anomalous non-monotonic dependence with concentration having a peak-like behavior for 10.2 mol% concentration of the weakly polar constituent. The transition between the two phases, being weakly first order, exhibits pretransitional effects signifying the appearance of the N-like regions in the isotropic phase. The coordinates of the maximum point of the convex shaped temperature-dependence of the dielectric constant in the isotropic phase, characteristic of strongly polar systems, also exhibit a non-monotonic dependence with concentration. Possible causes for these observations are discussed.