Showing papers on "Nanocomposite published in 2010"

P25-Graphene Composite as a High Performance Photocatalyst

Abstract: Herein we obtained a chemically bonded TiO2 (P25)-graphene nanocomposite photocatalyst with graphene oxide and P25, using a facile one-step hydrothermal method. During the hydrothermal reaction, both of the reduction of graphene oxide and loading of P25 were achieved. The as-prepared P25-graphene photocatalyst possessed great adsorptivity of dyes, extended light absorption range, and efficient charge separation properties simultaneously, which was rarely reported in other TiO2−carbon photocatalysts. Hence, in the photodegradation of methylene blue, a significant enhancement in the reaction rate was observed with P25-graphene, compared to the bare P25 and P25-CNTs with the same carbon content. Overall, this work could provide new insights into the fabrication of a TiO2−carbon composite as high performance photocatalysts and facilitate their application in the environmental protection issues.

Microfibrillated cellulose and new nanocomposite materials: a review

Abstract: Due to their abundance, high strength and stiffness, low weight and biodegradability, nano-scale cellulose fiber materials (e.g., microfibrillated cellulose and bacterial cellulose) serve as promising candidates for bio-nanocomposite production. Such new high-value materials are the subject of continuing research and are commercially interesting in terms of new products from the pulp and paper industry and the agricultural sector. Cellulose nanofibers can be extracted from various plant sources and, although the mechanical separation of plant fibers into smaller elementary constituents has typically required high energy input, chemical and/or enzymatic fiber pre-treatments have been developed to overcome this problem. A challenge associated with using nanocellulose in composites is the lack of compatibility with hydrophobic polymers and various chemical modification methods have been explored in order to address this hurdle. This review summarizes progress in nanocellulose preparation with a particular focus on microfibrillated cellulose and also discusses recent developments in bio-nanocomposite fabrication based on nanocellulose.

TiO2−Graphene Nanocomposites for Gas-Phase Photocatalytic Degradation of Volatile Aromatic Pollutant: Is TiO2−Graphene Truly Different from Other TiO2−Carbon Composite Materials?

Abstract: The nanocomposites of TiO2−graphene (TiO2−GR) have been prepared via a facile hydrothermal reaction of graphene oxide and TiO2 in an ethanol−water solvent. We show that such a TiO2−GR nanocomposite exhibits much higher photocatalytic activity and stability than bare TiO2 toward the gas-phase degradation of benzene, a volatile aromatic pollutant in air. By investigating the effect of different addition ratios of graphene on the photocatalytic activity of TiO2−GR systematically, we find that the higher weight ratio in TiO2−GR will decrease the photocatalytic activity. Analogous phenomenon is also observed for the liquid-phase degradation of dyes over TiO2−GR. In addition, the key features for TiO2−GR including enhancement of adsorptivity of pollutants, light absorption intensity, electron−hole pairs lifetime, and extended light absorption range have also been found in the composite of TiO2 and carbon nanotubes (TiO2−CNT). These strongly manifest that TiO2−GR is in essence the same as other TiO2−carbon (carb...

Enhanced Mechanical Properties of Graphene-Based Poly(vinyl alcohol) Composites

Abstract: Graphene, flat carbon nanosheets, has generated huge activity in many areas of science and engineering due to its unprecedented physical and chemical properties. With the development of wide-scale applicability including facile synthesis and high yield, this exciting material is ready for its practical application in the preparation of polymer nanocomposites. Here we report that nanocomposites based on fully exfoliated graphene nanosheets and poly(vinyl alcohol) (PVA) are prepared via a facial aqueous solution. A significant enhancement of mechanical properties of the graphene/PVA composites is obtained at low graphene loading; that is, a 150% improvement of tensile strength and a nearly 10 times increase of Young’s modulus are achieved at a graphene loading of 1.8 vol %. The comparison between the experimental results and theoretical simulation for Young’s modulus indicates that the graphene nanosheets in polymer matrix are mostly dispersed randomly in the nanocomposite films.

Graphene/Polyurethane Nanocomposites for Improved Gas Barrier and Electrical Conductivity

Abstract: Recently developed strategies for isolating single-layer carbon sheets from graphite have enabled production of electrically conductive, mechanically robust polymer nanocomposites with enhanced gas barrier performance at extremely low loading. In this article, we present processing, morphology, and properties of thermoplastic polyurethane (TPU) reinforced with exfoliated graphite. For the first time, we compare carbon sheets exfoliated from graphite oxide (GO) via two different processes: chemical modification (isocyanate treated GO, iGO) and thermal exfoliation (thermally reduced GO, TRG), and three different methods of dispersion: solvent blending, in situ polymerization, and melt compounding. Incorporation of as low as 0.5 wt % of TRG produced electrically conductive TPU. Up to a 10-fold increase in tensile stiffness and 90% decrease in nitrogen permeation of TPU were observed with only 3 wt % iGO, implying a high aspect ratio of exfoliated platelets. Real- and reciprocal-space morphological characteri...

Hierarchical Nanocomposites of Polyaniline Nanowire Arrays on Graphene Oxide Sheets with Synergistic Effect for Energy Storage

Abstract: We introduced a facile method to construct hierarchical nanocomposites by combining one-dimensional (1D) conducting polyaniline (PANI) nanowires with 2D graphene oxide (GO) nanosheets. PANI nanowire arrays are aligned vertically on GO substrate. The morphologies of PANI nanowires can be controlled by adjusting the ratios of aniline to GO, which are attributed to different nucleation processes. The hierarchical nanocomposite structures of PANI−GO were further proved by UV−vis, FTIR, and XRD measurements. The hierarchical nanocomposite possessed higher electrochemical capacitance and better stability than each individual component as supercapacitor electrode materials, showing a synergistic effect of PANI and GO. This study will further guide the preparation of functional nanocomposites by combining different dimensional nanomaterials.

Poly-Lactic Acid: Production, Applications, Nanocomposites, and Release Studies.

Abstract: Environmental, economic, and safety challenges have provoked packaging scientists and producers to partially substitute petrochemical-based polymers with biodegradable ones. The general purpose of this review is to introduce poly-lactic acid (PLA), a compostable, biodegradable thermoplastic made from renewable sources. PLA properties and modifications via different methods, like using modifiers, blending, copolymerizing, and physical treatments, are mentioned; these are rarely discussed together in other reviews. Industrial processing methods for producing different PLA films, wrappings, laminates, containers (bottles and cups), are presented. The capabilities of PLA for being a strong active packaging material in different areas requiring antimicrobial and antioxidant characteristics are discussed. Consequently, applications of nanomaterials in combination with PLA structures for creating new PLA nanocomposites with greater abilities are also covered. These approaches may modify PLA weaknesses for some food packaging applications. Nanotechnology approaches are being broadened in food science, especially in packaging material science with high performances and low concentrations and prices, so this category of nano-research is estimated to be revolutionary in food packaging science in the near future. The linkage of a 100% bio-originated material and nanomaterials opens new windows for becoming independent, primarily, of petrochemical-based polymers and, secondarily, for answering environmental and health concerns will undoubtedly be growing with time.

Design and Synthesis of Hierarchical MnO2 Nanospheres/Carbon Nanotubes/Conducting Polymer Ternary Composite for High Performance Electrochemical Electrodes

Abstract: For efficient use of metal oxides, such as MnO2 and RuO2, in pseudocapacitors and other electrochemical applications, the poor conductivity of the metal oxide is a major problem. To tackle the problem, we have designed a ternary nanocomposite film composed of metal oxide (MnO2), carbon nanotube (CNT), and conducting polymer (CP). Each component in the MnO2/CNT/CP film provides unique and critical function to achieve optimized electrochemical properties. The electrochemical performance of the film is evaluated by cyclic voltammetry, and constant-current charge/discharge cycling techniques. Specific capacitance (SC) of the ternary composite electrode can reach 427 F/g. Even at high mass loading and high concentration of MnO2 (60%), the film still showed SC value as high as 200 F/g. The electrode also exhibited excellent charge/discharge rate and good cycling stability, retaining over 99% of its initial charge after 1000 cycles. The results demonstrated that MnO2 is effectively utilized with assistance of ot...

Multifunctional Mesoporous Composite Microspheres with Well-Designed Nanostructure: A Highly Integrated Catalyst System

Abstract: The precise control of the size, morphology, surface chemistry, and assembly process of each component is important to construction of integrated functional nanocomposites. We report here the fabrication of multifunctional microspheres which possess a core of nonporous silica-protected magnetite particles, transition layer of active gold nanoparticles, and an outer shell of ordered mesoporous silica with perpendicularly aligned pore channels. The well-designed microspheres have high magnetization (18.6 emu/g), large surface area (236 m(2)/g), highly open mesopores (approximately 2.2 nm), and stably confined but accessible Au nanoparticles and, as a result, show high performance in catalytic reduction of 4-nitrophenol (with conversion of 95% in 12 min), styrene epoxidation with high conversion (72%) and selectivity (80%), especially convenient magnetic separability, long life and good reusability. The unique nanostructure makes the microsphere to be a novel stable and approachable catalyst system for various catalytic industry processes.

Nanosheets of oxides and hydroxides: Ultimate 2D charge-bearing functional crystallites.

Abstract: A wide variety of cation-exchangeable layered transition metal oxides and their relatively rare counterparts, anion-exchangeable layered hydroxides, have been exfoliated into individual host layers, i.e., nanosheets. Exfoliation is generally achieved via a high degree of swelling, typically driven either by intercalation of bulky organic ions (quaternary ammonium cations, propylammonium cations, etc.) for the layered oxides or by solvation with organic solvents (formamide, butanol, etc.) for the hydroxides. Ultimate two-dimensional (2D) anisotropy for the nanosheets, with thickness of around one nanometer versus lateral size ranging from submicrometer to several tens of micrometers, allows them to serve either as an ideal quantum system for fundamental study or as a basic building block for functional assembly. The charge-bearing inorganic macromolecule-like nanosheets can be assembled or organized through various solution-based processing techniques (e.g., flocculation, electrostatic sequential deposition, or the Langmuir-Blodgett method) to produce a range of nanocomposites, multilayer nanofilms, and core-shell nanoarchitectures, which have great potential for electronic, magnetic, optical, photochemical, and catalytic applications.

Ternary self-assembly of ordered metal oxide-graphene nanocomposites for electrochemical energy storage

Abstract: Surfactant or polymer directed self-assembly has been widely investigated to prepare nanostructured metal oxides, semiconductors, and polymers, but this approach is mostly limited to two-phase materials, organic/inorganic hybrids, and nanoparticle or polymer-based nanocomposites. Self-assembled nanostructures from more complex, multiscale, and multiphase building blocks have been investigated with limited success. Here, we demonstrate a ternary self-assembly approach using graphene as fundamental building blocks to construct ordered metal oxide−graphene nanocomposites. A new class of layered nanocomposites is formed containing stable, ordered alternating layers of nanocrystalline metal oxides with graphene or graphene stacks. Alternatively, the graphene or graphene stacks can be incorporated into liquid-crystal-templated nanoporous structures to form high surface area, conductive networks. The self-assembly method can also be used to fabricate free-standing, flexible metal oxide−graphene nanocomposite fil...

Fracture and fatigue in graphene nanocomposites

Abstract: Graphene, a single-atom-thick sheet of sp-bonded carbon atoms, has generatedmuch interest due to its high specific area and novel mechanical, electrical, and thermal properties. Recent advances in the production of bulk quantities of exfoliated graphene sheets from graphite have enabled the fabrication of graphene–polymer composites. Such composites show tremendous potential for mechanical-property enhancement due to their combination of high specific surface area, strong nanofiller–matrix adhesion and the outstanding mechanical properties of the sp carbon bonding network in graphene. Graphene fillers have been successfully dispersed in poly(styrene), poly(acrylonitrile) and poly(methyl methacrylate) matrices and the responses of their Young’s modulus, ultimate tensile strength, andglass-transition temperaturehave been characterized. However, to the best of our knowledge there is no report on the fracture toughness and fatigue properties of graphene–polymer composites. Fracture toughness describes the ability of a material containing a crack to resist fracture and it is a critically important material property for design applications. Fatigue involves dynamic propagation of cracks under cyclic loading and it is one of the primary causes of catastrophic failure in structural materials. Consequently, the material’s resistance to fracture and fatigue crack propagation are of paramount importance to prevent failure. Herein we report the fracture toughness, fracture energy, and fatigue properties of an epoxy polymer reinforced with various weight fractions of functionalized graphene sheets. Remarkably, only 0.125% weight of functionalized graphene sheets was observed to increase the fracture toughness of the pristine (unfilled) epoxy by 65% and the fracture energy by 115%.Toachievecomparableenhancement,carbonnanotube (CNT) and nanoparticle epoxy composites require one to two orders of magnitude larger weight fraction of nanofillers. Under fatigue conditions, incorporation of 0.125% weight of functionalized graphene sheets drastically reduced the rate of crack propagation in the epoxy 25-fold. Fractography analysis

Highly conductive, printable and stretchable composite films of carbon nanotubes and silver

Abstract: highly conductive, printable and stretchable hybrid composites composed of micrometre-sized silver flakes and multiwalled carbon nanotubes decorated with self-assembled silver nanoparticles. The nanotubes were used as one-dimensional, flexible and conductive scaffolds to construct effective electrical networks among the silver flakes. The nanocomposites, which included polyvinylidenefluoride copolymer, were created with a hot-rolling technique, and the maximum conductivities of the hybrid silver–nanotube composites were 5,710 S cm 21 at 0% strain and 20 S cm 21 at 140% strain, at which point the film ruptured. Three-dimensional percolation theory reveals that Poisson’s ratio for the composite is a key parameter in determining how the conductivity changes upon stretching. Useful combinations of conductivity and stretchability have been observed in vertically aligned multiwalled carbon nanotube (MWNT) forest/polyurethane films (� 0.5–1 S cm 21 at 0% strain and electrical resistance increased upon stretching 12 ) and in textiles

Thermal Conductivity: Theory, Properties, and Applications

Abstract: Section 1 Overview of Thermal Conductivity in Solid Materials: Theory of Thermal Conductivity. Thermal Conductivity of Metals. Thermal Conductivity of Insulators and Glasses. Thermal Conductivity of Semiconductors. Thermal Conductivity Of Semiconductor and Thermoelectric Materials. Thermal Conductivity of Superlattices. Experimental Studies on Thermal Conductivity of Thin Film and Superlattices.- Section 2 Measurement Techniques: Bulk Techniques. Experimental Techniques for Thin Film Thermal Conductivity Characterization.- Section 3 Thermal Properties and Applications of Emerging Materials: Glasses and Ceramic Materials. Quasicrystals. Thermal Properties of Nanomaterials and Nanocomposites.

Carbon nanotube/manganese oxide ultrathin film electrodes for electrochemical capacitors.

Abstract: Multiwall carbon nanotube (MWNT)/manganese oxide (MnO2) nanocomposite ultrathin film electrodes have been created via redox deposition of MnO2 on layer-by-layer (LbL)-assembled MWNT films. We demonstrate that these LbL-assembled MWNT (LbL-MWNT)/MnO2 thin films consist of a uniform coating of nanosized MnO2 on the MWNT network structure using SEM and TEM, which is a promising structure for electrochemical capacitor applications. LbL-MWNT/MnO2 electrodes yield a significantly higher volumetric capacitance of 246 F/cm3 with good capacity retention up to 1000 mV/s due to rapid transport of electrons and ions within the electrodes. The electrodes are generated with two simple aqueous deposition processes: the layer-by-layer assembly of MWNTs followed by redox deposition of MnO2 at ambient conditions, thus providing a straightforward approach to the fabrication of high-power and -energy electrochemical capacitors with precise control of electrode thickness at nanometer scales.

Carbon nanotube-based hierarchical composites: a review

Abstract: The introduction of carbon nanotubes (CNTs) into conventional fibre-reinforced polymer composites creates a hierarchical reinforcement structure and can significantly improve composite performance. This paper reviews the progress to date towards the creation of fibre reinforced (hierarchical) nanocomposites and assesses the potential for a new generation of advanced multifunctional materials. Two alternative strategies for forming CNT-based hierarchical composites are contrasted, the dispersion of CNTs into the composite matrix and their direct attachment onto the primary fibre surface. The implications of each approach for composite processing and performance are discussed, along with a summary of the measured improvements in the mechanical, electrical and thermal properties of the resulting hierarchical composites.

Polymer-Nanoparticle Composites: From Synthesis to Modern Applications

Abstract: The addition of inorganic spherical nanoparticles to polymers allows the modification of the polymers physical properties as well as the implementation of new features in the polymer matrix. This review article covers considerations on special features of inorganic nanoparticles, the most important synthesis methods for ceramic nanoparticles and nanocomposites, nanoparticle surface modification, and composite formation, including drawbacks. Classical nanocomposite properties, as thermomechanical, dielectric, conductive, magnetic, as well as optical properties, will be summarized. Finally, typical existing and potential applications will be shown with the focus on new and innovative applications, like in energy storage systems.

A high-performance gas-separation membrane containing submicrometer-sized metal-organic framework crystals.

Abstract: Metal–organic frameworks (MOFs) are an emerging class of nanoporous materials comprising metal centers connected by various organic linkers to create one-, two-, and threedimensional porous structures with tunable pore volumes, surface areas, and chemical properties. Several thousand MOF materials have been synthesized and their numbers continue to grow rapidly. MOFs are predicted to be highly attractive for application in gas-separation membranes and also have a range of other potential applications, for example in selective gas adsorption, hydrogen storage, catalysis, and sensing. Recently, thin continuous MOFmembranes for gas separation have been reported by several authors using MOFs such as MOF-5, HKUST-1 (Cu3(BTC)2), [8] Cu(hfipbb)(H2hfipbb)0.5, [9] and ZIF-8. However, the gas-permeation properties (permeability and selectivity) have so far not been found to be technologically attractive. This may have several reasons, such as membrane defects and related processing issues, use of MOFs with low selectivity, and unfavorable orientation of crystals in the membrane. An alternative route to high-performance MOF membranes is to incorporate them into polymers to obtain nanocomposite (mixed-matrix) membranes. The incorporation of nanoporous molecular sieves such as zeolites into polymeric membranes has attracted much attention, since one can in principle combine the size/shape selectivity of nanoporous materials with the processibility and mechanical stability of polymers. However, zeolite/polymer composite membranes often have defective morphologies characterized by void spaces between the zeolite particles and the polymeric matrix, leading to poor gas-separation performance since the gas molecules bypass the zeolite particles. Recent approaches to address the issue of interface compatibilization are emerging. On the other hand, the use of MOFs in mixed-matrix membranes provides several potential advantages over zeolites. The control of MOF/polymer interface morphology is easier than that of the zeolite/polymer interface, since the organic linkers in MOFs have better affinity with polymer chains than the inorganic zeolites do, and the surface properties of MOFs can be easily tuned by functionalization with various organic molecules if necessary. In general, MOFs also have higher pore volumes and lower density than zeolites, and hence their effect on the membrane properties can be greater for a given mass loading. Recently, several MOFmixed-matrix membranes such as Cu-BPY-HFS (Cu-4,40-bipyridine hexafluorosilicate) in Matrimid, HKUST-1 in poly(sulfone), MOF-5 in Matrimid, and Cu-TPA (terephthalic acid) in poly(vinyl acetate) have been reported. Although a high degree of MOF/polymer adhesion (as characterized by scanning electron microscopy) was found, the gas-separation performance of these membranes was not high. In addition to the control of interface morphology, the selection of appropriate MOF/polymer pairs is indispensable for high-performance mixed-matrix membranes, a fact emphasized in theoretical predictions. ZIF-90 (zeolitic imidazolate framework-90) is an attractive MOF for application in CO2-selective mixed-matrix membranes. ZIF-90 has a sodalite cagelike structure with 0.35 nm pore windows, through which size exclusion of CH4 from CO2/CH4 mixtures is possible. [20] Furthermore, the imidazole linker in ZIF-90 contains a carbonyl group, which has a favorable chemical noncovalent interaction with CO2. [21] Submicrometer-sized crystals of a related MOF material, ZIF-8, have recently been reported. So far, ZIF-90 crystals have been synthesized by the conventional solvothermal method. However, their size (ca. 100 mm) is too large for use in thin mixed-matrix membranes (which require submicrometer-sized crystals). Herein, we describe the synthesis of submicrometer-sized ZIF-90 crystals by a novel method, namely nonsolvent-induced crystallization. The ZIF-90 crystals were thoroughly characterized, and we compare them with solvothermally synthesized ZIF-90. Mixed-matrix membranes were then fabricated using three poly(imide)s as polymer matrices, and their CO2/CH4 separation properties were investigated. In particular, we demonstrate the first MOF-containing gas-separation membranes with technologically attractive properties. The morphology of our ZIF-90 crystals is shown in Figure 1. In general, the synthesis of smaller crystals requires reaction conditions that favor nucleation over crystal growth. Particle-size control proved difficult in conventional solvothermal synthesis. We crystallized small ZIF-90 particles at room temperature by the rapid addition of a nonsolvent to the reagent solution (see the Supporting Information), leading to supersaturation of the solution. The nucleation rate can be [*] Dr. T.-H. Bae, J. S. Lee, Dr. W. Qiu, Prof. Dr. W. J. Koros, Prof. Dr. C. W. Jones, Prof. Dr. S. Nair School of Chemical & Biomolecular Engineering Georgia Institute of Technology 311 Ferst Drive NW, Atlanta, GA 30332-0100 (USA) Fax: (+1)404-894-4200 E-mail: christopher.jones@chbe.gatech.edu sankar.nair@chbe.gatech.edu

Enhanced thermoelectric performance of single-walled carbon nanotubes/polyaniline hybrid nanocomposites.

Abstract: Hybrid nanocomposites containing carbon nanotubes (CNTs) and ordered polyaniline (PANI) have been prepared through an in situ polymerization reaction using a single-walled nanotube (SWNT) as template and aniline as reactant. TEM, SEM, XRD, and Raman analyses show that the polyaniline grew along the surface of CNTs forming an ordered chain structure during the SWNT-directed polymerization process. The SWNT/PANI nanocomposites show both higher electrical conductivity and Seebeck coefficient as compared to pure PANI, which could be attributed to the enhanced carrier mobility in the ordered chain structures of the PANI. The maximum electrical conductivity and Seebeck coefficient of composites reach 1.25 × 104 S m−1 and 40 μV K−1, respectively, and the maximum power factor is up to 2 × 10−5 W m−1 K−2, more than 2 orders of magnitude higher than the pure polyaniline. This study suggests that constructing highly ordered chain structure is a novel and effective way for improving the thermoelectric properties of c...

Interfacial stress transfer in a graphene monolayer nanocomposite

Abstract: It is demonstrated from stress-induced Raman bands shifts that stress can be transferred from a polymer matrix to a graphene monolayer (see image) in a model nanocomposite. It is shown further that the behavior can be modeled using continuum mechanics and that the interface between the graphene and the polymer breaks down at a shear stress of the order of 2 MPa.

Spontaneous high-concentration dispersions and liquid crystals of graphene

Abstract: Graphene combines unique electronic properties and surprising quantum effects with outstanding thermal and mechanical properties. Many potential applications, including electronics and nanocomposites, require that graphene be dispersed and processed in a fluid phase. Here, we show that graphite spontaneously exfoliates into single-layer graphene in chlorosulphonic acid, and dissolves at isotropic concentrations as high as approximately 2 mg ml(-1), which is an order of magnitude higher than previously reported values. This occurs without the need for covalent functionalization, surfactant stabilization, or sonication, which can compromise the properties of graphene or reduce flake size. We also report spontaneous formation of liquid-crystalline phases at high concentrations ( approximately 20-30 mg ml(-1)). Transparent, conducting films are produced from these dispersions at 1,000 Omega square(-1) and approximately 80% transparency. High-concentration solutions, both isotropic and liquid crystalline, could be particularly useful for making flexible electronics as well as multifunctional fibres.

Multi-scale mechanical and fracture characteristics and early-age strain capacity of high performance carbon nanotube/cement nanocomposites

Abstract: Due to their exceptional mechanical properties, carbon nanotubes (CNTs) are considered to be one of the most promising reinforcing materials for the next generation of high-performance nanocomposites. In this study, the reinforcing effect of highly dispersed multiwall carbon nanotubes (MWCNTs) in cement paste matrix has been investigated. The MWCNTs were effectively dispersed in the mixing water by using a simple, one step method utilizing ultrasonic energy and a commercially available surfactant. A detailed study on the effects of MWCNTs concentration and aspect ratio was conducted. The excellent reinforcing capabilities of the MWCNTs are demonstrated by the enhanced fracture resistance properties of the cementitious matrix. Additionally, nanoindentation results suggest that the use of MWCNTs can increase the amount of high stiffness C–S–H and decrease the porosity. Besides the benefits of the reinforcing effect, autogenous shrinkage test results indicate that MWCNTs can also have a beneficial effect on the early strain capacity of the cementitious matrix, improving this way the early age and long term durability of the cementitious nanocomposites.

New Insight for Enhanced Photocatalytic Activity of TiO2 by Doping Carbon Nanotubes: A Case Study on Degradation of Benzene and Methyl Orange

Abstract: A carbon nanotubes (CNT)/TiO2 nanocomposite photocatalyst has been prepared by a simple impregnation method, which is used, for the first time, for gas-phase degradation of benzene. It is found that the as-prepared CNT/TiO2 nanocomposite exhibits an enhanced photocatalytic activity for benzene degradation, as compared with that over commerical titania (Degussa P25). A similar phenomenon has also been found for liquid-phase degradation of methyl orange. The characterization of photocatalysts by a series of joint techniques, including X-ray diffraction, transmission electron microscopy, ultraviolet/visible (UV/vis) diffuse reflectance spectra, and photoluminescence spectra, discloses that CNT has two kinds of crucial roles in enhancement of photocatalytic activity of TiO2. One is to act as an electron reservoir, which helps to trap electrons emitted from TiO2 particles due to irradiation by UV light, therefore hindering electron−hole pairs recombination. The other is to act as a dispersing template or suppo...