Here we report on the synthesis of a graphene/polyaniline (PANI) nanocomposite and its application in the development of a hydrogen (H2) gas sensor. Using a chemical synthetic route, graphene was prepared and ultrasonicated with a mixture of aniline monomer and ammonium persulfate to form PANI on its surface. The developed material was characterized by scanning electron microscopy (SEM), transmission electron microscopy, Raman spectroscopy, and X-ray photoemission spectroscopy. The SEM study revealed that the PANI in the composite has a nanofibrillar morphology. We investigated the H2 gas sensing performance of this material and compare it with that of the sensors based on only graphene sheets and PANI nanofibers. We found that the graphene/PANI nanocomposite-based device sensitivity is 16.57% toward 1% of H2 gas, which is much larger than the sensitivities of sensors based on only graphene sheets and PANI nanofibers.

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A layered surface acoustic wave gas sensor based on a polyaniline/In2O3 nanofibre composite

The structural, spectroscopic, and magnetochemical characteristics of a new tetranuclear iron-oxo complex are reported. [Fe402(02CCH3)7(bpy)2](C104>y4CH2Cl2-H20 (l) crystallizes in the monoclinic space group C2/c with a = 27.261 (10) A, b = 11.789 (4) Á, c = 16.439 (5) A, ß = 118.27 (2)°, V = 4653.19 Á3, and Z = 4. The structure was refined with 2646 reflections having F > 2.33a(F), giving final R factors of 0.0644 and 0.0688 for R and Rw, respectively. The [Fe402]8+ core of the cation is structurally similar to other [M402]8+ (M = Mn, Fe) complexes which have been previously reported.The core structure consists of a tetranuclear bis^-O) cluster disposed in a "butterfly" arrangement. Two different Fe-O(oxide) bridge distances of 1.819 ( 5) Á (wing-body) and 1.926 ( 5) Á (body-body) are observed. These differences are reflected in the Mossbauer spectrum of the complex, which analyzes as two quadrupole-split doublets in the range of 100-300 K. Each of the doublets has parameters characteristic of high-spin Fe(III) ions.NMR spectra are reported for two [Fe402]8+ complexes. Assignments for all resonances were made on the basis of chemical shift data for two related complexes and one deuterated complex as well as measurements of spin-lattice (T¡) relaxation times. The magnetic susceptibility of complex 1 was measured in the range of 5.01-277.4 K. The effective moment per molecule decreases gradually from 4.20 µ at 277.4 K to 0.82 µ at 5.01 K, indicating a diamagnetic 5 = 0 ground state. A detailed theoretical analysis of the susceptibility data using a spin Hamiltonian approach gives a value for the "wing-body" Fe-Fe magnetic exchange interaction parameter of Jwb = -45 cm'1. It was interesting to find that the "body-body" interaction Jbb is indeterminate and can only be described as being more positive than -15 cm"1. The lack of definition of Jbb is due to spin frustration, where the relative magnitudes of the antiferromagnetic Jwb and 7bb interactions result in a net alignment of the spin vectors on the two body dioxo bridge core Fem ions. The significance of these results as they pertain to exchange coupling in iron-oxo proteins is discussed.

A template‐free method for the production of polypyrrole nanofibers is presented. By adding a small amount of bipyrrole into the oxidative polymerization of pyrrole, a drastic change in the morphology of the observed material is observed from large, granular particles to nanofibrils with an average diameter of 20 nm. This simple procedure allows for the production of polypyrrole nanofibers without the presence of surfactants or other structural directing agents. The polypyrrole nanofibers can form stable water dispersions which can be cast into films of sufficient quality to function as chemical sensors for analytes such as ammonia.magnified image

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This study demonstrates the enhanced Cu2+ adsorption capability of polyaniline nanofibers (PAni NFs) by doping of phytic acid. The PAni NFs were synthesized by radical polymerization process using acidic solutions of hydrochloric and phytic acid, yielding chlorinated (Cl-) and phytic acid-doped (Ph-) PAni NFs. The Ph-PAni NFs showed remarkably higher Cu2+-adsorption efficiency than Cl-PAni NFs, presumably owing to high capacity and/or high ionic affinity of the doped phytic acid in Ph-PAni NFs. The pH-dependent adsorption capability exhibited increasing Cu2+ adsorption trend as increasing aqueous pH because of spontaneous deprotonation of the doped phytic acid in a basic environment. Furthermore, Ph-PAni NFs showed stable, high Cu2+ adsorption capability, irrespective of Co2+ concentration in the bimetallic Cu and Co aqueous solution. Surface morphologies of PAni NFs were investigated using electron microscopy, and molecular structures were identified using X-ray photoemission and Fourier transform infrared spectroscopies. The ability of PAni NFs to capture aqueous Cu2+ is discussed in terms of surface functional groups doped to NFs. Surface modification and/or doping to enhance the adsorption capability of Cu­(II) introduced in this study will provide a great venue for expanding the use of many other polymeric nanostructures for reclamation in metal mining as well as the conventional environmental applications such as water purification.