Introduction Of Multi-walled Carbon Nanotubes Research Articles

Electrochemical synthesis and study of poly(2,5-diarylamino-3,6-dichlorobenzoquinone) and its composite with multiwalled carbon nanotubes

A procedure has been developed for electrochemical polymerization of dianiline dichlorobenzoquinone and electrosynthesis of a composite material based on poly(dianiline dichlorobenzoquinone) and multiwalled carbon nanotubes (MCNTs) in 1 M H2SO4. The introduction of a polymerization initiator (potassium hexachloroiridate IrCl62− (HCI)) accelerated the growth of the electrode coating. The introduction of MCNTs led to the creation of a current-conducting framework in the composite and an increase in the mass and electrochemical capacity of the electrode coating. The electrochemical behavior of the composite is similar to that of polyaniline (PAni), but includes the redox reaction of the chloranil substituents. The charging of the double electric layer makes a significant contribution to the electrochemical capacity.

In situ processing of MWCNTs/leucite composites through geopolymer precursor

A serial of multi-walled carbon nanotubes (MWCNTs) reinforced geopolymer composites were prepared, and then heated at elevated temperature to fabricate MWCNTs/leucite composites by in situ transformation. Effects of high-temperature treatment on the microstructure evolution and mechanical performance of the composites were investigated. The results indicated that the introduction of MWCNTs could improve the mechanical properties of geopolymer, and the optimum content was 3wt%. The mechanical performance declined instead with the further increase in MWCNTs content up to 5wt%, which could be attributed to the agglomeration of MWCNTs. Significant improvements in mechanical properties were achieved after the composites were treated in a temperature range from 950°C to 1200°C relative to their original state before heat treatment. The significant improvements could be described to the matrix densification, and leucite formation as well as the proper interface bonding state between carbon nanotube and leucite matrix.

Multi-walled carbon nanotubes induced a controllable TiO2morphology transformation for high-rate and long-life lithium-ion batteries

A facile strategy to achieve the controllable morphology transformation of TiO2induced by the introduction of multi-walled carbon nanotubes has been demonstrated.

Honeycomb structured porous films prepared from arborescent graft polystyrenes via the breath figures method

Highly ordered honeycomb films were produced from arborescent graft polystyrene (AGPS) solutions using breath figures (BF). The structure of the BF pattern (whether single layered or multilayered) of pores depended on several factors such as the type of solvent used (CS2 or CHCl3), the length of the side chains, the generation number and the concentration of the polymer. When solutions of AGPS with shorter side chains (Mw ∼ 5000 g/mol) were used for the BF process, arborescent polymers generated a multilayer pore structure. However, when polymers with longer side chains (Mw ∼ 30,000 g/mol) were used, monolayer pore structures were mostly generated. The regularity and surface quality of the honeycomb pattern became worsened as the multilayered structures formed. The polymer concentration (ϕ) also played a critical role in determining the morphology of the BF films. Higher ϕ led to a multilayer pore structure while lower ϕ resulted in a monolayer pore structure. In general, the regularity of top layer pores was found to decrease with increasing generation number. The introduction of multiwall carbon nanotubes (MWCNTs) into AGPS solutions and application of the BF process using the solution blends yielded patterned hybrid films. SEM images showed that some CNTs were loaded into the honeycomb pattern of AGPS, but that most MWCNTs precipitated to form the bottom layer. In this work, the influence of concentration and surface modification of MWCNTs on the BF patterns obtained is discussed.

Impact of multiwall carbon nanotubes on the fatigue strength of adhesive joints

This paper presents the results of research undertaken to determine the possibility of improving the fatigue properties of peel-loaded adhesive joints by dispersing multiwall carbon nanotubes (MWCNTs) into epoxy-based adhesives. The fatigue strength tests were carried out on an electromagnetic inductor with the resonance frequency of the adhesively bonded joint specimen. The tests were conducted for three types of epoxy adhesives whose properties were modified through the introduction of multiwalled carbon nanotubes, into their structure. Carbon nanotubes were synthesized by means of the Chemical Vapour Deposition (CVD) method with Fe-Co catalysts. A quantity of 1wt.% of the dried material was dispersed into the epoxy adhesives. The results of the fatigue strength tests revealed a significant improvement of the fatigue lifetime of adhesive joints due to MWCNT introduction as filler for epoxy adhesives. In the case of the Epidian 57/PAC adhesive composition, a more than twofold increase in the fatigue lifetime was obtained (an increase of 106.8%). For the Bison Epoxy adhesive composition, the fatigue lifetime increased by 69.3%. The fatigue strength for the best result increased by about 13%.

Bi4O5Br2 ultrasmall nanosheets in situ strong coupling to MWCNT and improved photocatalytic activity for tetracycline hydrochloride degradation

Multiwalled carbon nanotube (MWCNT)/Bi4O5Br2 materials have been prepared with the Bi4O5Br2 ultrasmall nanosheets in situ strong coupling to MWCNT via the ionic liquid (IL) assisted solvothermal method. The formation mechanism was based on the original formation of strong coupling between the IL and MWCNT, and then the tight junctions between Bi4O5Br2 and MWCNT can be established as the bromine ions in the IL react with bismuth source to in situ produce Bi4O5Br2 during solvothermal process. The structures, morphologies, surface features, optical properties, electronic structures and photocatalytic properties were investigated in detail. The MWCNT/Bi4O5Br2 materials exhibited increased photocatalytic activity than pure Bi4O5Br2 for the degradation of antibiotic agent tetracycline hydrochloride and rhodamine B. Meanwhile, the 0.1wt% MWCNT/Bi4O5Br2 materials displayed the highest activity. The hole and O2− were determined to be the main active species during the photodegradation process under visible light irradiation by the electron spin resonance, X-ray photoelectron spectroscopy valence band spectra and active species trapping experiments. After the introduction of MWCNT, the molecular oxygen activation capacity of Bi4O5Br2 greatly improved, which was believed to be responsible for the increased photocatalytic activity.

Bacterial-biofilm enhanced design for improved electrocatalytic reduction of oxygen in neutral medium

The specific reactivity and ability of biofilms to form stable polymer-like hydrogel aggregates of microorganisms adhering to common solid (including the glassy carbon electrode) surfaces have been explored here to form systems analogous to electrocatalytic redox-polymer modified electrodes. Growth of biofilms has been demonstrated with use of Yersinia enterocolitica, a robust Gram-negative rod-shaped bacteria known to be resistive to pH changes (4-10) and temperature variations (0–40°C). Charge distribution and propagation within the biofilm have been enhanced by introduction of multi-walled carbon nanotubes. The fact that carbon nanotubes are derivatized with the carboxyl-group containing 4-(pyrrole-l-yl) benzoic acid has facilitated the hybrid material integrity and stability, namely through electrostatic attractive interactions between anionic carboxyl sites and positively charged domains of bacterial aggregates. In neutral media, the biofilm-based composite (hybrid) matrices have exhibited themselves electrocatalytic activity during electroreductions of oxygen and hydrogen peroxide (with possibility of its sensing in a broad range of concentrations). By immobilizing additional catalytic (cobalt porphyrin) sites, a truly bifunctional redox-polymer-like electrocatalytic system capable of significantly enhancing oxygen reduction currents has been produced. Apparently, the reduction of oxygen (to hydrogen peroxide) is initiated at cobalt porphyrin centers, and the second step (decomposition of hydrogen peroxide intermediate to water) is pursued at reactive sites (perhaps c-cytochrome) existing within biofilm matrix. Comparative measurements have been performed with the biofilm-supported platinum nanoparticles as well as with such a model catalytic system as platinized carbon nanotubes. The proposed electrode designs are relevant to biosensing and to the development of alternate cathode materials for biofuel cells or biobatteries.

Morphologies and electromagnetic interference shielding performances of microcellular epoxy/multi-wall carbon nanotube nanocomposite foams

Microcellular epoxy/multi-wall carbon nanotube (EP/MWCNT) composite foams loaded with 0.5, 1.0, 2.0 and 3.0 wt% of multi-walled carbon nanotubes (MWCNTs) were prepared by a batch foaming process with supercritical carbon dioxide (scCO2). The morphologies of EP/MWCNT composite foams were analyzed by scanning electron microscopy (SEM). It was found that there was a synergic effect between the formation of microcellular structure and the addition of MWCNTs on improving the performances of EP/MWCNT composite foams. The addition of MWCNTs promoted the formation of microcellular structure, and the growth of cells in turn induced the redistribution of MWCNTs. Furthermore, the electromagnetic interference (EMI) shielding effectiveness (SE) of EP/MWCNT solid and foamed composites was investigated. The results indicated that the foaming improved the specific EMI SE from 5.2 to 21.3 dB cm3/g at the MWCNT content of 1.0 wt%. The introduction of MWCNTs and microcellular structure synergistically enhanced the EMI shielding performance of epoxy-based composites.

Synthesis and electrochemical characterization of binary carbon supported Pd3Co nanocatalyst for oxygen reduction reaction in direct methanol fuel cells

Binary carbon supports are applied to make the membrane electrode assembly (MEA) of passive direct methanol fuel cells (PDMFCs) and their comprehensive electrochemical characterization is considered. Electrocatalytic properties for the oxygen reduction reaction (ORR) are evaluated using polarization curves and electrochemical impedance spectroscopy (EIS) in PDMFC. The best efficiency is obtained when the mass ratio of multi-walled carbon nanotubes (MWCNTs) and Vulcan XC-72R (VC) is 25:75. The results of the electrode kinetic parameters indicate that introduction of MWCNTs as a secondary support delivers high available surface area, good electronic conductivity, and fast ORR kinetics. In addition to the significant role of Pd3Co active surface area on kinetic of the system, the improvement of kinetic parameters is also associated with the decrease of activation energy for ORR on binary-support electrode resulting in a notable enhancement of kinetic parameters. An 8-h lifetime test is performed for the single cell to evaluate the durability in which the MEA is made using MWCNT/VC with the mass ratio of 25:75. The test results show that the mentioned ratio of MWCNT and VC support results in highest stability and durability.

Conducting-Polymer-Supported Bacterial Biofilms As Active Matrices for Noble Metal and Molecular Catalytic Centers: Enhancement of Electroreduction of Oxygen and Carbon Dioxide

Hybrid matrices composed of porous conducting polymer - polyaniline (PANI) or poly(3,4- ethylenedioxythiophene) (PEDOT) - underlayer, robust bacterial biofilm and the multi-walled carbon nanotubes have been demonstarted to function as highly active supports for dispersed catalztic centers (both noble metal nanoparticles and molecular ligand complexes). We explore unique properties of biofilms, i.e. polymeric aggregates of microorganisms, in which cells adhere to each other on the electrode surfaces. Such systems are characterized by extracellular electron transfers involving c-type cytochromes (heme-containing proteins). Biofilms grown on inert carbon electrode substrates tend to exhibit electrocatalytic properties towards oxygen and hydrogen peroxide reductions in neutral media. The processes have been found to be further enhanced by introduction of multi-walled carbon nanotubes (MCNTs) that are modified with ultra-thin layers of organic (e.g. 4-(pyrrole-l-yl) benzoic acid. We expect here attractive electrostatic interactions between carboxyl-group containing anionic adsorbates and positively charged domains of the biofilm with c-type cytochrome enzymatic sites. Coexistence of the above components leads to synergistic effect that is evident from positive shift of the oxygen reduction voltammetric potentials and significant increase of voltammetric currents. Most likely, the reduction of oxygen has been initiated at the molecular (e.g. intentionally added cobalt porphyrin redox centers), whereas the undesirable hydrogen peroxide intermediate are further decomposed at the cytochrome sites. Among other important observations is the significant enhancement of activity of Pt nanoparticles toward electroreduction of carbon dioxide in the presence of such a robust bacterial biofilm as Y. enterocolitica. Although interactions between platinum and such a complex ecosystem as biofilm are difficult to describe precisely, it is reasonable to postulate some inhibition of the hydrogen evolution (competitive reaction) at platinum nanoparticles in presence of bacterial microcolonies in favor of enhancement of the CO2-reduction. It is also noteworthy that biofilms are highly hydrated, and existence of open water channels between the bacterial microcolonies facilitates flow of supporting electrolyte. Combination of the hydrophobic polymer (PANI) structures with hydrophilic bacterial aggregates seems to produce attractive hybrid supports for electrocatalysts operating in aqueous media. Based on numerous repetitive diagnostic experiments in both argon and carbon dioxide saturated electrolytes, it can be stated that, by growing and supporting the biofilm onto the PANI polymer underlayer, the overall stability of the biofilm-based system has been improved. Indeed, we have not effectively observed any degradation of the hybrid catalytic films (both in terms of electrocatalytic activity and physicochemical stability) during our prolonged diagnostic experiments. Because measurements have been performed in neutral (phosphate buffer at pH=6.1) rather than acid medium, the PANI films (regardless of the presence of some HSO4 - anions) are not expected to be very well conducting. Consequently, we have also introduced MWCNTs to the electrocatalytic interface to facilitate charge distribution there.

Open-cell phenolic carbon foam and electromagnetic interference shielding properties

In this study, phenolic foam composites (PFC2Fs) with closed-cell structure consisting of multi-walled carbon nanotubes (MWCNTs) and nano-Fe3O4 were prepared via in-situ polymerization. The introduction of MWCNTs and nano-Fe3O4 can endow the PF with electromagnetic interference (EMI) shielding property. The sample with 2 wt% MWCNTs and 7 wt% Fe3O4 (PFC2F7) with thickness of 2 mm exhibited the EMI shielding effectiveness (SE) with ∼34 dB at 8–12 GHz. Furthermore, novel high-performance carbonized PF/2 wt% MWCNTs/Fe3O4 composite foams (C-PFC2Fs, carbon foam) with open-cell structure were fabricated by using high-temperature heat treating method. The obtained C-PFC2F7 exhibited the highest EMI SE of ∼62 dB at 8–12 GHz. The shielding mechanism of MWCNTs and nano-Fe3O4 was investigated. The method is fast and simple, which may promote the commercialization of composite foams in the potential applications as EMI shielding materials in the fields of spacecraft and aircraft.

Effective monitoring of the electro-Fenton degradation of phenolic derivatives by differential pulse voltammetry on multi-walled-carbon nanotubes modified screen-printed carbon electrodes

This work illustrates a fast, sensitive and selective electroanalytical methodology for simultaneous determination of phenolic derivatives. Optimization of differential pulse voltammetry (DPV) conditions and electrochemical study by cyclic voltammetry (CV) of phenolics are included. Differential pulse voltammetry at screen-printed carbon electrodes (SPCE) was selected for the sensitive detection of m-Cresol and Tert-butylhydroquinone. The introduction of Multi-walled Carbon-Nanotubes with acid groups, MWCNT-COOH, as modifier on working SPCE enhances the performance of electrode surface with a highly catalytic activity on it, allowing a 5-fold higher sensitive analysis than unmodified SPCE, with a limit of detection as low as about 1μM. This simple and low-cost methodology has been applied, for first time, to monitoring the electro-Fenton degradation of m-Cresol, giving selective information of the reactant loss and products formation. Aromatic intermediates (monohydroxy, polyhydroxy and quinone phenolic derivatives) have been identified and followed during the electrolysis process. The electro-Fenton with iron on activate carbon is 4-fold faster than with other catalyst. The results are validated by chromatographic (HPLC) technique. The electroanalytical methodology described, in conjunction with the use of small SPCE as sensor transducer, can be implemented for continuous monitoring of end-point of the electro-Fenton reaction at industrial level in wastewater remediation plants, indicating the two main stages of electro-Fenton during the electrolysis.

(Keynote) Biofilm-Supported Redox-Polymer-Type Materials for Electrocatalytic Oxygen Reduction of Importance to Biosensing and Bioenergetics

Unique properties of biofilms, which include possibility of extracellular electron transport, specific redox activity and capability to form stable polymeric or hydro-gel like microorganism aggregates adhering to common surfaces (including the glassy carbon electrode substrate), were explored here to form systems analogous to redox-polymer modified electrodes. Growth of biofilms was demonstrated with use of Yersinia enterocolitica, a robust Gram-negative rod-shaped bacteria known to be resistive to pH changes (4-10) and temperature variations (0-40oC). The dynamics of bioelectronic transfers originating from the presence of c-type cytochromes, i.e. heme-containing proteins within the biofilm, were further enhanced by introduction of multi-walled carbon nanotubes. Long-term stability of the biofim-based materials was achieved by impregnating them with porous but rigid conducting polymer, poly(3,4-ethylenodioxythiophene) or PEDOT. The fact that carbon nanotubes were derivatized with the carboxyl-group containing 4-(pyrrole-l-yl) benzoic acid facilitated the materials integrity through electrostatic attractive interactions between anionic carboxyl sites and positively charged domains of conducting polymer (PEDOT) structures. In neutral media, the biofilm-based composite (hybrid) matrices exhibited themselves electrocatalytic activity toward reduction of hydrogen peroxide (with possibility of sensing in the broad range of concentrations) and some activity during electroreduction of oxygen. By immobilization of additional catalytic (cobalt porphyrin) sites, a truly bifunctional electrocatalytic interface capable of significantly enhancing oxygen electroreduction currents was produced. Apparently, the reduction of oxygen (to hydrogen peroxide) was initiated at cobalt porphyrin centers and the further reaction (decomposition of hydrogen peroxide intermediate to water) was continued at c-cytochrome–containing biofilm matrix. These features are of importance to bioenergetics, i.e. to the development of cathodes for biofuel cells or biobatteries.

Development of Biofilm-Based Electrocatalytic Materials for Biosensing and Bioenergetics

Biofilms, are polymeric aggregates of microorganisms, in which cells adhere to each other on the electrode surfaces. Such systems are characterized by extracellular electron transfers involving c-type cytochromes (heme-containing proteins). Biofilms can be grown on inert carbon electrode substrates tend to exhibit electrocatalytic properties towards oxygen and hydrogen peroxide reductions in neutral media. The processes have been found to be further enhanced by introduction of multi-walled carbon nanotubes (MCNTs) that are modified with ultra-thin layers of organic (e.g. 4-(pyrrole-l-yl) benzoic acid. We expect here attractive electrostatic interactions between carboxyl-group containing anionic adsorbates and positively charged domains of the biofilm with c-type cytochrome enzymatic sites. Coexistence of the above components leads to synergistic effect that is evident from positive shift of the oxygen reduction voltammetric potentials and significant increase of voltammetric currents. Most likely, the reduction of oxygen has been initiated at the molecular (e.g. intentionally added cobalt porphyrin redox centers), whereas the undesirable hydrogen peroxide intermediate are further decomposed at the cytochrome sites. An additional subject of interest is the process of carbon dioxide (CO2) reduction. There has been a growing interest in catalytic systems capable of efficient conversion of carbon dioxide into fuels. One of the promising electrocatalytic materials exhibiting high activity in this process is a macromolecular complex of palladium (II) with Schiff-base-ligands. Reduction of carbon dioxide may lead to carbon-based fuels and its derivatives. Fabrication of the biofilm based matrices for anodic reactions has also been considered. To facilitate electron transfers between the electrode surface and the redox protein centers, the concept of codeposition of multi-walled carbon nanotubes within the bioelectrocatalytic film has also been pursued here. First, carbon nanotubes are modified with ultra-thin layers of tetrathiafulvalene (TTF) or poly(dimethyldiallylammonium chloride) (PDDA) mediators. Their presence is expected to facilitate flow of electrons from the enzyme (e.g. glucose oxidase) active sites through biofilm to the electrode surface. Combination of intentionally derivatized carbon nanotubes with biofilm matrtices and the appropriate enzymes seems to produce biocatalytic systems capable of effective oxidation and sensing of glucose or ethanol in the neutral buffered solution. Collaboration with W. Lotowska, E. Szaniawska, E. Seta, M. Gierwatowska, B. Kowalewska and I.A. Rutkowska (from Faculty of Chemistry) as well as A. Raczkowska and K. Brzostek (from Faculty of Biology) is acknowledged.

MWCNTs/Cellulose Hydrogels Prepared from NaOH/Urea Aqueous Solution with Improved Mechanical Properties

Novel high strength composite hydrogels were designed and synthesized by introducing multiwalled carbon nanotubes (MWCNTs) into cellulose/NaOH/urea aqueous solution and then cross-linked by epichlorohydrin. MWCNTs were used to modify the matrix of cellulose. The structure and morphology of the hydrogels were characterized by Fourier transform infrared (FT-IR) spectroscopy, high resolution transmission electron microscopy (HR-TEM), and scanning electron microscopy (SEM). The results from swelling testing revealed that the equilibrium swelling ratio of hydrogels decreased with the increment of MWCNTs content. Thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) results demonstrated that the introduction of MWCNT into cellulose hydrogel networks remarkably improved both thermal and mechanical properties of the composite hydrogels. The preparation of MWCNTs modifiedcellulose-based composites with improved mechanical properties was the first important step towards the development of advanced functional materials.

Enhancement in Mode II Interlaminar Fracture Toughness at Cryogenic Temperature of Glass Fiber/Epoxy Composites through Matrix Modification by Carbon Nanotubes and n‐Butyl Glycidyl Ether

A typical diglycidyl ether of bisphenol‐F (DGEBF)/diethyl toluene diamine (DETD) epoxy system modified by multiwalled carbon nanotubes (MWCNTs) and a reactive aliphatic diluent named n‐butyl glycidyl ether (BGE) was used as the matrix for glass fiber composites. The glass fiber (GF) reinforced composites based on the unmodified and modified epoxy matrices were prepared by the hand lay‐up hot‐press process. Mode II interlaminar fracture toughness at both room temperature (RT) and cryogenic temperature (77 K) of the GF reinforced epoxy composites was investigated to examine the effect of the matrix modification. The result showed that the introduction of MWCNTs and BGE at their previously reported optimal contents led to the remarkable enhancement in mode II interlaminar fracture toughness of the composites. Namely, the 22.9% enhancement at RT and the 31.4% enhancement at 77 K were observed for mode II interlaminar fracture toughness of the fiber composite based on the optimally modified epoxy matrix by MWCNTs and BGE compared to the unmodified case.

Dispersion of Carbon Nanotubes in AA6061 Aluminium Alloy Powder by the High Energy Ball Milling Process

Multi-wall carbon nanotubes (MWCNT), up to 2% in weight, were dispersed into AA6061 aluminium alloy by high-energy ball milling (HEBM) process, for further consolidation into extruded metal-matrix composites (MMC) bars. Three distinct routes were employed: the simple one step loading of materials inside the milling vials, an ultrasonically assisted dispersion of MWCNT and alloy powder into acetone prior to the milling, and the gradual introduction of MWCNT into the vials, during the milling process. Mixed powders obtained were evaluated in terms of the MWCNT integrity after HEBM, and the dispersion level obtained for several milling times. It was found that MWCNT remain relatively undamaged even for milling times up to 10 h, being embedded into the ductile alloy particles through the breaking/welding process during HEBM. However, shorter milling times result in poor dispersion of MWCNT in the milled powders. This tendency can be improved by using pre-milling mixture procedures, as the ultrasonically assisted wet dispersion of nanotubes and alloy powder.

Facile synthesis of uniform MWCNT@Si nanocomposites as high-performance anode materials for lithium-ion batteries

We demonstrate the synthesis of uniform multi-walled carbon nanotube (MWCNT)@Si nanocomposites via the magnesiothermic reduction of pre-synthesized MWCNT@SiO2 nanocables. At first, the acid vapor steaming is used to treat the surface, which can facilitate the uniform deposition of SiO2 layer via the TEOS hydrolysis. Then, the uniform MWCNT@Si nanocomposites are obtained on the basis of MWCNT@SiO2 nanocables via a simple magnesiothermic reduction. When used as an anode material for lithium-ion batteries, the as-synthesized MWCNT@Si nanocomposites show high reversible capacity and good cycling performance, which is better than bulk Si and bare MWCNTs. It is believed that the good electrochemical performance can be attributed to the novel porous nanostructure and the introduction of MWCNTs that can buffer the volume change, maintain the electrical conductive network, and enhance the electronic conductivity and lithium-ion transport.

Importance of Specific Interactions between Support, Metal Oxide Nanostructures and Noble Metal or Organometallic Sites in Efficient Electrocatalytic and Bioelectrocatalytic Reduction of Oxygen

Systems utilizing carbon nanostructures (e.g. nanotubes) and noble metal nanoparticles can form advanced electrocatalytic materials with well-defined composition, structure and thickness. We explore here the ability of inorganic structures to stabilize and derivatize metal (Au, Pt, Pd) and carbon nanostructures. Among inorganic systems, polyoxometallates of tungsten are attractive since they can not only adsorb irreversibly on solid surfaces but also exhibit reversible stepwise multi-electron transfer reactions. The concept of the layer-by-layer formation of hybrid inorganic assemblies composed of anionic polyoxometallate-protected carbon nanotubes (or metal nanoparticles) and ultra-thin nanostructures of positively charged metal oxide (vanadia, titania, zirconia) nanostructures (alone or in combination with tungsten oxide) will be described and discussed here. The resulting novel composite materials are characterized by fast dynamics of charge propagation. When it comes to the electrocatalytic reduction of oxygen, polyoxometallates can also be applied to stabilize and link Pt, Pd and various alloyed Pt-based catalytic nanoparticles.To produce bioelectrocatalytic materials for oxygen reduction, we explore unique properties of biofilms, i.e. polymeric aggregates of microorganisms, in which cells adhere to each other on the electrode surfaces. Such systems are characterized by extracellular electron transfers involving c-type cytochromes (heme-containing proteins). Biofilms grown on inert carbon electrode substrates tend to exhibit electrocatalytic properties towards oxygen and hydrogen peroxide reductions in neutral media. The processes have been found to be further enhanced by introduction of multi-walled carbon nanotubes (MCNTs) that are modified with ultra-thin layers of organic (e.g. 4-(pyrrole-l-yl) benzoic acid. We expect here attractive electrostatic interactions between carboxyl-group containing anionic adsorbates and positively charged domains of the biofilm with c-type cytochrome enzymatic sites. Coexistence of the above components leads to synergistic effect that is evident from positive shift of the oxygen reduction voltammetric potentials and significant increase of voltammetric currents. Most likely, the reduction of oxygen has been initiated at the molecular (e.g. intentionally added metalloporphyrin redox centers), whereas the undesirable hydrogen peroxide intermediate are further decomposed at the cytochrome sites. Acknowledgement We appreciate collaboration with Krzysztof Miecznikowski, Adam Lewera, Beata Dembinska, Jakub Sek, and Anna Dobrzeniecka from Faculty of Chemistry, University of Warsaw.

Decoration of phthalocyanine on multiwalled carbon nanotubes/cellulose nanofibers nanocomposite for decoloration of dye wastewater

Abstract We describe the incorporation of multiwalled carbon nanotubes (MWNT) into cellulose nanofibers for the subsequent functionalization of cobalt tetraaminophthalocyanine (CoPc) catalyst. MWNT doped cellulose acetate nanofiber mats (MWNT/CA-NM) was prepared by electrospinning MWNT-cellulose acetate mixed solution. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) confirmed the morphologies of nanofibers and the aligned distribution of MWNT along the nanofiber axis. Both the thermal stability and the mechanical properties of nanofibers were significantly improved with increased MWNT concentration. CoPc was covalently immobilized onto the surface of nanofibers after MWNT/CA-NM was hydrolyzed with KOH, oxidized with NaIO 4 , and spacer-arm attached with tetraethylenepentamine (TEPA), using glutaraldehyde as a coupling agent. The resulting cellulose nanofiber-based functional nanomaterial, MWNT doped, CoPc functionalized cellulose nanofiber mats (MWNT/CoPc-spacer-NM), can efficiently decolorize reactive dye wastewater, and the introduction of MWNT obviously improved the catalytic efficiency of CoPc. Ultraviolet–visible light spectroscopy (UV) and fluorescence spectroscopy (FL) experiments identified the communication between the CoPc and the MWNT, which might be responsible for the improvement of catalytic activity.