Nano Fe3O4-activated carbon composites for aqueous supercapacitors

In this study, a symmetric supercapacitor has been fabricated by adopting the nanostructured iron oxide (Fe3O4)-activated carbon (AC) composite as the core electrode materials. The composite electrodes were prepared via a facile mechanical mixing process and PTFE polymeric solution has been used as the electrode material binder. Structural analysis of the nanocomposite electrodes were characterized by scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis. The electrochemical performances of the prepared supercapacitor were studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in 1.0 M Na2SO3 and 1.0 M Na2SO4 aqueous solutions, respectively. The experimental results showed that the highest specific capacitance of 43 F/g is achieved with a fairly low Fe3O4 nanomaterials loading (4 wt. %) in 1 M Na2SO3. It is clear that the low concentration of nanostructured Fe3O4 has improved the capacitive performance of the composite via pseudocapacitance charge storage mechanism as well as the enhancement on the specific surface areas of the electrode. However, further increasing of the Fe3O4 content in the electrode is found to distort the capacitive performance and deteriorate the specific surface area of the electrode, mainly due to the aggregation of the Fe3O4 particles within the composite. Additionally, the CV results showed that the Fe3O4/AC nanocomposite electrode in Na2SO3 electrolyte exhibits a better charge storage performance if compared with Na2SO4 solution. It is believed that Fe3O4 nanoparticles can provide favourable surface adsorption sites for sulphite (SO32-) anions which act as catalysts for subsequent redox and intercalation reactions

Studies on the growth and characterization of CdS and PbS nanoparticles using sugar-ester nonionic water-in-oil microemulsion

The nanometer-sized semiconductors of CdS and PbS were prepared in the nonionic water-in-oil microemulsion system formed by sucrose monoester, 1-butanol, cyclohexane and water. The surfactant that has been employed in the present study is commercial food grade additive, in which is biodegradable and nonhazardous to the environment. The resultant nanoparticles were characterized by X-ray diffraction measurements in order to determine the crystalline phase of the products. The structural and morphological features of the nanoparticles have been investigated by energy filter transmission electron microscopy, X-ray photoelectron spectroscopy and UV-Vis absorption spectroscopy. The experimental results showed that the synthesized nanoparticles exhibited strong quantum confinement effect as the optical band gap increased significantly as compared to the bulk molecules. In addition, the as-prepared nanoparticles were found in spherical shape with a reasonably narrow size distribution. © 2003 Elsevier Science B.V. All rights reserved

Synthesis and characterization of conducting polyaniline-coated cadmium sulphide nanocomposites in reverse microemulsion

II-VI group of semiconductor cadmium sulphide (CdS) nanocrystalline, which were coated with conducting polyaniline (PANI), have been prepared by microemulsion processing technique. The synthesized polyaniline-coated CdS nanocomposites were characterized by UV-Vis absorption spectroscopy, energy filter transmission electron microscopy (EFTEM), FTIR spectroscopy and TGA analysis. The UV-Vis spectrums revealed the enhancement of doping level for the nanocomposites, which is assigned to the existence of greater number of charges on the polymer backbone. The FTIR spectra indicated that the polymers were highly doped and existed in conducting emeraldine salt form. The as-prepared PANI/CdS nanocomposites were polydispersed and have an average size of ca. 17.8 nm. The obtained CdS/PANI nanocomposites showed significant improvement in the thermal behavior as indicated in the TGA thermograph. © 2003 Elsevier B.V. All rights reserved

Synthesis of NiS nanoparticles using a sugar-ester nonionic water-in-oil microemulsion

Nickel sulfide (NiS) nanoparticles were prepared in water-in-oil (w/o) microemulsion system containing sucrose ester as the surfactants. The commercial food grade sucrose monoester (abbreviated S-1170) is a biodegradable and non-toxic surfactant, which can be adopted to form w/o microemulsion system in the presence of 1-butanol as co-solvent. The pseudo-ternary phase diagram for the inverse microemulsion region has been determined by the titration method. It was found that the studied system forms clear and homogenous microemulsion when heated to 37 °C but gradually becomes turbid at room temperature due to the phase separation. The as-prepared NiS nanoparticles were characterized by energy filter transmission electron microscopy (EFTEM), UV-VIS-NIR absorption spectroscopy and X-ray photoelectron spectroscopy (XPS). The results showed that the synthesized nanoparticles have regular shape, monodispersed and in the size range of 3-12 nm. © 2003 Elsevier B.V. All rights reserved

Single w/o microemulsion templating of CdS nanoparticles

We report the synthesis of monodispersed CdS nanoparticle with tunable size by controlling the reaction aging time in a single water in oil (w/o) microemulsion system. The w/o microemulsion system consists of nonionic surfactant poly (oxyethylene) 5 nonyl phenol ether (NP5), poly (oxyethylene) 10 nonyl phenol ether (NP10), cyclohexane and aqueous solution (cadmium salt and thioacetamide). Thioacetamide (TAA) has been utilized as a source for slow release of sulfur ions in the in situ synthesis of CdS. UV-Visible spectra shows obvious blue shift for the CdS nanoparticles as compared to the bulk material due to quantum size effect. CdS nanoparticle size depends on the reaction aging time where longer reaction aging time yields bigger particles. CdS nanoparticles growth behaviour as a function of reaction aging time in the microemulsion system was characterized by UV-Visible spectroscopy. The particle growth follows a power law with an exponential in the order of 0.17. Energy Filter Transmissions Electron Microscopy (EFTEM) reveals monodispersed CdS nanoparticles with standard deviation, � less than 8. © 2004 Kluwer Academic Publishers

Synthesis and characterization of copper sulfide nanoparticles in hexagonal phase lyotropic liquid crystal

Copper sulfide nanoparticles were prepared in lyotropic hexagonal phase consisting of poly (oxyethelene) 5 nonyl phenol ether (NP5), poly (oxyethelene) 10 nonyl phenol ether (NP10), cyclohexane and aqueous solutions. The stability of the hexagonal phase, which was employed as the reaction template, has been determined by polarizing microscopy, small-angle X-ray scattering (SAXS) and rheology measurement. The optical observation showed that the hexagonal phase liquid crystal system still presented the characteristics spherulitic and focal conic texture after the growth reaction. In addition, there was giving no significant changes on the rheological response of the surfactant system after the formation of the copper sulfide nanoparticles. SAXS data showed that the microstructure dimensions of the surfactant aggregates were preserved and not affected by the growth reaction inside the systems. The final products were characterized by energy filter transmission microscopy, energy dispersive X-ray analysis and UV-visible absorption spectroscopy. The results showed that the size and morphology of the nanoparticles obtained were greatly affected by the reaction aging time. The presence of quantum confinement effect was apparent for the resulting nanoparticles as the estimated optical band-gap energy increased markedly with the decrement of the particles size. © 2004 Elsevier B.V. All rights reserved

In situ templating of PbS nanorods in reverse hexagonal liquid crystal

We report the in situ templating of lead sulfides (PbS) with mean diameter of 5.7 ± 1.0 nm in the reverse hexagonal phase liquid crystal using lead nitrate and thioacetamide as the reactants. The texture of the reverse hexagonal phase for before and after PbS growth does not varies as observed under polarizing microscope indicating direct templating of PbS in hexagonal liquid crystalline phase. This result is consistent with measurement using small-angle X-ray scattering (SAXS). X-ray photoelectron spectroscopy (XPS) has been carried out to confirm the formation of PbS and energy filter transmission electron microscopy (EFTEM) observations show the size and shape of the PbS particles. The templated PbS nanorods show blue shift compare to the bulk material when characterized using UV-vis-NIR spectroscopy. © 2004 Elsevier B.V. All rights reserved

Preparation and characterization of ZnS nanoparticles synthesized from chitosan laurate micellar solution

Synthesis of ZnS nanostructured materials has been performed in the micellar solution system, containing chitosan laurate as the surfactant. The self-assembling of the surfactant molecules in water solution can form unique architecture that can be adopted as the reaction template for the formation of nanomaterials. The synthesized nanomaterials have been characterized by energy filter transmission electron microscopy (EFTEM), Energy Dispersive X-ray Analysis (EDAX), X-ray diffractometry (XRD) and UV-Visible absorption measurement in order to determine the size, morphology, composition, crystal structure and optical behavior of the products. The spectroscopic results showed that the synthesized nanoparticles exhibited strong quantum confinement effect as the optical band gap increased significantly as compared to the bulk materials. In addition, the size of the resulting nanoparticles is greatly affected by the surfactant concentration and range from 2 to 10 nm. It was found that the nanomaterials obtained existed in face-centered cubic structure and exhibited the characteristic line broadening feature in the XRD patterns. © 2004 Elsevier B.V. All rights reserved

In situ polymerization of conducting polyaniline in bicontinuous cubic phase of lyotropic liquid crystal

The polymerization of conducting polyaniline (PANI) in lyotropic bicontinuous cubic phase consisted of poly(oxyethylene) 10 nonyl phenol ether (NP10), octane and water have been explored. The rheology measurements have been carried out in order to assess the phase behavior of the pure lyotropic mesophases, doped with reactant and after polymerization. It was found that the phase structure did not rupture upon polymerization as the complex modulus of the system after polymerization is maintained in the cubic phase region. The results of small-angle X-ray scattering (SAXS) also showed that the microstructure of the mesophase did not disrupt after the polymerization process and indicate the direct templating of polyaniline in the cubic lyotropic mesophase. The synthesized PANI particles have been characterized by energy filter transmission electron microscopy (EFTEM), UV-vis absorption and Fourier transform infrared (FTIR) spectroscopy. The spectroscopy studies revealed the presence of emeraldine salts in the polymer, and thus confirms that the prepared polyaniline is in conducting form. The microscopy results showed that the resulting polymers have spherical shape with mesopores structure, fairly monodispersed and in the size range of 100-300 nm, depending on the reactants concentration. © 2004 Elsevier B.V. All rights reserved

Green synthesis of graphene-silver nanocomposites and its application as a potent marine antifouling agent

Fouling of marine surfaces has been a perpetual problem ever since the days of the early sailors. The tenacious attachment of seaweed and invertebrates to man-made surfaces, notably on ship hulls, has incurred undesirable economic losses. Graphene receives great attention in the materials world for its unique combination of physical and chemical properties. Herein, we present a novel 2-step synthesis method of graphene-silver nanocomposites which bypasses the formation of graphene oxide (GO), and produces silver nanoparticles supported on graphene sheets through a mild hydrothermal reduction process. The graphene-Ag (GAg) nanocomposite combines the antimicrobial property of silver nanoparticles and the unique structure of graphene as a support material, with potent marine antifouling properties. The GAg nanocomposite was composed of micron-scaled graphene flakes with clusters of silver nanoparticles. The silver nanoparticles were estimated to be between 72 and 86 nm (SEM observations) while the crystallite size of the silver nanoparticles (AgNPs) was estimated between 1 and 5 nm. The nanocomposite also exhibited the SERS effect. GAg was able to inhibit Halomonas pacifica, a model biofilm-causing microbe, from forming biofilms with as little as 1.3 wt.% loading of Ag. All GAg samples displayed significant biofilm inhibition property, with the sample recording the highest Ag loading (4.9 wt.% Ag) associated with a biofilm inhibition of 99.6%. Moreover, GAg displayed antiproliferative effects on marine microalgae, Dunaliella tertiolecta and Isochrysis sp. and inhibited the growth of the organisms by more than 80% after 96 h. The marine antifouling properties of GAg were a synergy of the biocidal AgNPs anchored on the stable yet flexible graphene sheets, providing maximum active contact surface areas to the target organisms