Preparation of cellulose/multi-walled carbon nanotube composite membranes with enhanced conductive property regulated by ionic liquids

Cellulose/multi-walled carbon nanotubes (MWCNTs)- composite membranes applied in electrochemical and biomedical fields were prepared using 1-ethyl-3-methylimidazolium diethyl phosphate (EmimDEP) as solvent in this study. With the increasing of MWCNTs amount, the membrane conductivity increased, and the conductivity reached 9.1 S/cm as the mass ratio of MWCNTs to cellulose being 2:1. The additions of sodium dodecyl sulfate (SDS), 1-hexadecyl-3-methylimidazolium bromide (C₁₆mimBr) and 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF₄) efficiently improved the conductivity, mechanical property, and thermal stability by promoting the dispersion of MWCNTs. When the mass ratio of C₁₆mimBr to MWCNTs changed from 0 to 0.3:1, the conductivity increased from 0.08 S/cm to 0.14 S/cm, and the tensile strength increased from 13.3 MPa to 17.0 MPa. These results indicate that the binary ionic liquids (ILs) system can regulate the properties of the composite membranes, and is a feasible approach for preparing cellulose/MWCNTs composite membranes with enhanced properties.     

Preparation and characterization of porous carbon based nanocomposite for supercapacitor

Porous nanocomposites are prepared by electrospinning blended polyacrylonitrile, copper acetate and mutiwalled carbon nanotube in N, N-dimethylformamide. The electrospun nanofiber webs are oxidatively stabilized and then carbonized resulting in composite carbon nanofibers. The study reveals that composite nanofibers with relatively smooth surface morphology are successfully prepared. X-ray diffraction is used to confirm the presence of Cu in carbon nanofibers. The carbon nanofibers with CNTs have better thermal stability and higher electrical conductivity. The Brunauer-Emmett-Teller analysis reveals that C/Cu/CNTs nanocomposites with mesopores possess larger specific surface area and narrower pore size distribution than that of C/Cu nanofibers. The electrochemical properties are investigated by cyclic voltammetry and galvanostatic charge-discharge tests. The nanocomposite with 0.5 wt.% CNT loading exhibits an energy density of 2 Whkg^?1, power density of 1916 Wkg^?1, a specific capacitance of about 225 Fg^?1 at a current density of 2 Ag^?1 and its capacitance decreased to 78 % of its initial value after 3,000 cycles.     

Preparation and characterization of bacterial cellulose/hydroxypropyl chitosan blend as-spun fibers

In the work, N-methylmorpholine-N-oxide monohydrate (NMMO·H₂O) was used as a solvent to solve bacterial cellulose (BC) and hydroxypropyl chitosan (HPCS) together, and regenerated bacterial cellulose (RBC)/HPCS blend as-spun fibers were prepared by blending BC with HPCS via wet-spinning in the Lyocell process. Structure and properties of the blend as-spun fibers were characterized by different techniques, together with the antibacterial activity of the blend as-spun fibers against Staphylococcus aureus. Results revealed that HPCS was mixed with BC very well. The blend as-spun fibers showed a rough and folded surface morphology and an interior pore structure on the cross-section. Compared with pure RBC as-spun fibers, the blend as-spun fibers had lower degree of crystallinity and thermal stability. Although extension at break of the blend as-spun fibers was lower than the pure RBC as-spun fibers, their tensile strength and modulus had been enhanced obviously. The blend as-spun fibers were also found to exhibit excellent antibacterial activities against S. aureus.     

A study of mechanical behavior and morphology of carbon nanotube reinforced UHMWPE/Nylon 6 hybrid polymer nanocomposite fiber

We report a phenomenal increase in strength, modulus, and fracture strain of ultra high molecular weight polyethylene (UHMWPE) fiber by 103 %, 219 %, and 108 %, respectively through hybridizing this fiber with Nylon 6 as a minor phase and simultaneously reinforcing it with single-walled carbon nanotubes (SWCNTs). Loading of Nylon 6 and SWCNTs into UHMWPE was 20.0 wt% and 2.0 wt%, respectively. Hybridized fibers were processed using a solution spinning method coupled with melt mixing and extrusion. We claim that the enhancement in strain-to-failure of the nanocomposites is due to induced plasticity in the hybridized Nylon 6-UHMWPE polymers. The enhancement in strength and stiffness in the nanocomposites is attributed to the load sharing of the SWCNTs during deformation. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) studies showed that changes in percent crystallinity, rate of crystallization, crystallite size, alignment of nanotubes, sliding of polymer interfaces and strong adhesion of CNT/polymer blends were responsible for such enhancements.     

Development of transparent bacterial cellulose nanocomposite film as substrate for flexible organic light emitting diode (OLED) display

Nanocomposite film composed of bacterial cellulose (10-50 wt.%) and poly-urethane (PU) based resin was fabricated and utilized as a substrate for flexible organic light emitting diode (OLED) display. The performance of the nanocomposite satisfied the criteria for the substrate of OLED with an additional feature of flexibility. The visible light transmittance of the nanocomposite film was as high as 80%. Its thermal stability was stable up to 150 °C while its dimensional stability in terms of coefficient of thermal expansion (CTE) was less than 20 ppm/K. After OLED was fabricated on the substrate through thermal evaporation technique, the OLED performed highest current efficiency of 0.085 cd/A and power efficiency of 0.021 lm/W at 200 cd/m² while retained its flexible feature, suggesting that bacterial cellulose nanocomposite is a promising material for the development of substrate for flexible OLED display.     

In-situ preparation of multi-walled carbon nanotube (MWNT)/cellulose nanocomposites and their physical properties

The multi-walled carbon nanotube (MWNT)/cellulose nanocomposites were prepared by using monohydrated Nmethylmorpholine-N-oxide (NMMO) as a solvent for dispersing the acid-treated MWNTs (A-MWNTs) as well as for dissolving the cellulose. The A-MWNTs were well dispersed in both monohydrated NMMO and the nanocomposite films. The nanocomposite films were prepared by a film-casting method onto a glass plate. The tensile strain at break, Young’s modulus, and toughness of nanocomposite films increased by ～5, ～2 and ～12 times, respectively at ? (A-MWNT content in the nanocomposite)=0.8 wt%, as compared to those of the pure cellulose film. The thermal degradation temperature of the nanocomposite films also increased from 329 to 339 oC by incorporation of 1 wt% A-MENTs. The electric conductivities of the A-MWNT/cellulose nanocomposites at ? =1 and 10 wt% were 2.09×10^?5 and 3.68×10^?3 S/cm, respectively. The transmittances were 86, 69 and 55 % at 550 nm for 0.4, 0.8 and 1 wt% nanocomposite films, respectively. Thus, these nanocomposites are promising materials in terms of all the properties studied in this paper and can be used for many applications, such as toughened cellulose fibers, transparent electrodes, etc.     

Oxidation of regenerated cellulose with nitrogen dioxide/carbon tetrachloride

This paper explores the influence of oxidation time on selective oxidation of regenerated cellulose with NO₂/CCl₄ as oxidation system. FTIR and other testing methods are used to characterize the structure of oxidized regenerated cellulose (ORC), showing that the regenerated cellulose is oxidized at C6 by the NO₂/CCl₄ system with extremely high selectivity. With the extension of oxidation duration, the carboxyl content in ORC increases gradually from 12.11 to 21.29 % while the degree of polymerization (DP) decreases from 92.86 to 53.40 and the strength of monofilament decreases gradually. In case of the reaction duration of 24 h, the performance of oxidation product can satisfy the requirement of absorbing hemostatic materials, i.e., with good hemostatic performance, while it is also provided with excellent antibacterial activity, which the reduction in colony forming units (CFU) is more than 99.9 %.     

Preparation and characterization of silk sericin/glycerol/graphene oxide nanocomposite film

Sericin (SS) is a protein that is secreted by silkworms, but it is usually discarded during the degumming process. To obtain and make use of the sericin, we prepared sericin/glycerol/graphene oxide nanocomposite film. The inherent brittleness of pure sericin film was improved by the addition of glycerol (Glc) as a plasticizer. To compensate for the reduced stiffness, we added graphene oxide (GO) into the SS/Glc film. At concentrations of up to 0.8 wt% relative to SS, GO dispersed evenly in the SS matrix without any agglomeration. The maximum tensile strength (9.5±0.7 MPa) and Young’s modulus (414.4±23.2 MPa) were obtained when the GO content was 0.8 wt% relative to SS. The elongation of SS/Glc/GO nanocomposite film also increased by approximately 40 % compared to SS/Glc film. The strong interfacial interaction between the SS and the GO was responsible for the increased stiffness. The increased elongation was due to the reduced crystallinity of the sericin matrix in the presence of GO.     

Electrospinning and microwave absorption of polyaniline/polyacrylonitrile/multiwalled carbon nanotubes nanocomposite fibers

Electrical conductive nanocomposite fibers were prepared with polyaniline (PANI), polyacrylonitrile (PAN) and multi-walled carbon nanotubes (MWCNTs) via electrospinning. The morphology and electrical conductivity of the PANI/PAN/MWCNTs nanocomposite fibers were characterized by scanning electron microscope (SEM) and Van De Pauw method. Electrical conductivity of nanocomposite fibers increased from 1.79 S·m^?1 to 7.97 S·m^?1 with increasing the MWCNTs content from 3.0 wt% to 7.0 wt%. Compared with PANI/PAN membranes, the mechanical property of PANI/PAN/MWCNTs nanocomposites fiber membranes decreased. The microwave absorption performance of composite films was analyzed using waveguide tube, which indicated that with the thickness increasing the value of R_L reduced from ?4.6 to ?5.9 dB.     

A flexible nanocomposite membrane based on traditional cotton fabric to enhance performance of microbial fuel cell

A flexible and stretchable three-dimensional nanocomposite membrane based on traditional cotton fabric is a promising alternative for proton exchange membrane because it has the capability of transferring protons, is inexpensive, and also have higher current density compared to Nafion membranes in microbial fuel cells. The obtained results showed that the highest power and current of PVAc-g-PVDF-coated cotton fabric were 400±10 mW/m² and 92 mA/m², respectively. However, maximum generated power and current for Nafion-117 were 300±10 mW/m² and 60 mA/m², respectively. The highest proton conductivity of PVAc-g-PVDF-coated cotton fabric was (1.5±0.2)×10^-2 S/cm at 25 °C and lowest glucose permeability was (12±1)×10^-6 cm²/s after Mg²⁺ ions adsorption. Furthermore, the highest COD removal (85±3 %) and CE (11.2 %) were obtained from PVAc-g-PVDF-coated cotton fabric. The coated cotton fabric can provide a novel route for low-cost production of high-performance flexible proton exchange materials from the natural fabrics.     

Morphology and properties of polyacrylonitrile/single wall carbon nanotube composite films

Composite films were prepared by casting the solution of polyacrylonitrile (PAN) and single wall nanotube (SWNT) in DMF subsequent to sonication. The SWNTs in the films are well dispersed as ropes with 20–30 nm thickness. Moreover, AFM surface image of the composite film displays an interwoven fibrous structure of nanotubes which may give rise to conductive passways and lead to high conductivity. The polarized Raman spectroscopy is an ideal characterization technique for identification and the orientation study of SWNT. The well-defined G-peak intensity at 1580 cm⁻¹ shows a dependency on the draw ratio under cross-Nicol. The degree of nanotube orientation in the drawn film was measurable from the sine curve obtained by rotating the drawn film on the plane of cross-Nicol of polarized Raman microscope. The threshold loading of SWNT for electrical conductivity in PAN is found to be lower than 1 wt% in the composite film. The electrical conductivity of the SWNT/PAN composite film decreased with increasing of draw ratio due to the collapse of the interwoven fibrous network of the nanotubes with uniaxial orientation.     

Preparation of hybrid AHO-POSS/polypropylene nanocomposite monofilaments by radiation induced grafting

The Allyl-heptaisobutyl-polyhedral Oligomeric Silsesquioxane (AHO-POSS) grafted polypropylene (PP) nanocomposite monofilaments were prepared by γ-ray irradiation induced grafting. The structure and properties of physically blended and γ-ray irradiated AHO-POSS/PP nanocomposite filaments were investigated by FTIR, wide-angle X-ray diffraction (WAXD), Thermo-gravimetric Analysis and mechanical property studies. Chemical bonding of AHO-POSS with PP after γ-ray irradiation was confirmed by FT-IR spectroscopy. Grafting resulted in change in mechanical and thermal properties and the extent of change was critically dependent on loading of AHO-POSS in PP and radiation dose level. In general, tensile strength decreased almost continuously with increase in radiation dose whereas thermal stability increased upto a radiation dose of 5 kGy and then decreased. The loss in tensile strength was caused due to chain scission, cross linking and loss in orientation.     

Three-dimensional carbon nanotube electrodes for extracellular recording of cardiac myocytes

Low impedance at the interface between tissue and conducting electrodes is of utmost importance for the electrical recording or stimulation of heart and brain tissue. A common way to improve the cell-metal interface and thus the signal-to-noise ratio of recordings, as well as the charge transfer for stimulation applications, is to increase the electrochemically active electrode surface area. In this paper, we propose a method to decrease the impedance of microelectrodes by the introduction of carbon nanotubes (CNTs), offering an extremely rough surface. In a multistage process, an array of multiple microelectrodes covered with high quality, tightly bound CNTs was realized. It is shown by impedance spectroscopy and cardiac myocyte recordings that the transducer properties of the carbon nanotube electrodes are superior to conventional gold and titanium nitride electrodes. These findings will be favorable for any kind of implantable heart electrodes and electrophysiology in cardiac myocyte cultures.     

Preparation and property of ultrahigh molecular weight polyethylene/halloysite nanotube fiber

In this research, halloysite nanotubes (HNTs) were incorporated into ultra-high molecular weight polyethylene (UHMWPE) in order to prepare the nanocomposite fibers by a gel-spun and hot drawing process. The HNTs were treated with oleic acid to improve the dispersion in the UHMWPE fibers. Both the crystallinity tested by differential scanning calorimetry (DSC) and mechanical properties increased with a low loading of HNTs, and decreased with a high loading. The thermal gravimetric analysis (TGA) test showed the thermal stability to improve with the incorporation of HNT. The addition of HNT did not change the crystal type, according to the X-ray diffraction (XRD) study.     

Compressional behavior of carbon nanotube reinforced mesophase pitch-based carbon fibers

The tensile-recoil compressional behavior of the carbon nanotube reinforced mesophase pitch (MP)-based composite carbon fibers (CNT-re-MP CFs) was investigated by using Instron and SEM. The CNT-re-MP CFs exhibited improved, or at least equivalent, compressive strength as compared with commercial MP-based carbon fibers. Particularly, when CNT of 0.1 wt% was reinforced, the ratios of recoil compressive strengths to tensile strength of CNT-re-MPCFs were much higher (the difference is at least 10% or higher) than those for the commercial counterparts and even than those for PAN-based commercial carbon fibers. FESEM micrographs showed somewhat different fractography from that of a typical shear failure as the CNT content increased.     

Directly-prelithiated carbon nanotube film for high-performance flexible lithium-ion battery electrodes

Carbon nanotube (CNT) films are very flexible and serve as active materials for lithium-ion batteries (LIBs). Hence, they have high potential as flexible free-standing electrodes for wearable batteries. However, nanocarbon materials such as CNTs and graphene are of limited use as electrodes because they have a large initial irreversible capacity due to the formation of a solid electrolyte interphase (SEI). Herein, we prelithiated the CNT films to make them available as electrodes for flexible batteries by reducing their irreversible capacity. The SEI is pre-formed through a direct prelithiation (DP) method that brings lithium metal into direct contact with CNT films in an electrolyte. As a result, the capacity of directly-prelithiated CNT film electrodes continues to increase to 1520 mAh/g until 350th cycle of charge/discharge and their initial irreversible capacity vanishes. The changes in the electrochemical properties of CNT film electrodes by DP treatment and their flexibility are investigated.     

Properties of polyacrylonitrile/single wall carbon nanotube composite films prepared in nitric acid

Nanocomposite films were prepared by casting the solution of polyacrylonitrile (PAN) and single wall nanotube (SWNT) in nitric acid subsequent to sonication. Even though SWNT shows good dispersion visually, the reinforcing effect was not satisfactory. The G-band Raman spectra of the drawn film clearly demonstrated that SWNTs in the film are well-oriented along the drawing axis of the film. The electrical resistivity of the film prepared using nitric acid was lower than that of the film using DMF. Thus, nitric acid is presumably more effective in dispersing nanotubes than DMF.     

Preparation and characterization of poly(2-hydroxyethyl methacrylate) grafted bacterial cellulose using atom transfer radical polymerization

The purpose of this study is to synthesize grafted Bacterial Cellulose (BC) nanofibers using Atom Transfer Radical Polymerization (ATRP) reinforced into poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogel matrix. Nanofibers grafting polymerizations were conducted in the presence of the catalyst CuCl/CuBr and the initiator 2-bromoisobutyrylbromide (2-BiBr). Degrees of substitution (DS) of BC-macroinitiators were quantified using both elemental analysis and gravimetric method. FTIR results confirmed BC nanofibers’ surface modifications of both initiator and hydroxyethyl methacrylate (HEMA) grafts. X-ray spectroscopy further confirmed the increase in carbonyl content after PHEMA-grafting polymerization. Results of the gravimetric analysis showed an increase in the weight of the grafted BC upon increasing reaction time. Furthermore, the change in the swelling ratio percentages of the reinforced composites product (BC-MI-3-g-PHEMA-1.5) was considerably higher based on reaction time. Slight increase in the swelling ratio of BC-MI-3 nanofibers was observed after 48 hours to reach 31 %. Moreover, results of thermal gravimetric analysis (TGA) demonstrated that decomposition temperature at 50 % weight loss (T₅₀) decreased to 350 °C for BC-MI-3-g-PHEMA-1.5. These characteristics demonstrate potentials for applications in the biomedical fields including drug delivery and wound care.     

Enhancement biocompatibility of bacterial cellulose membrane via laccase/TEMPO mediated grafting of silk fibroins

Silk fibroin (SF) has the characteristic of moisture penetrability and biocompatibility. To enhance the biocompatibility of bacterial cellulose (BC), silk fibroin is grafted onto BC membrane using laccase and 2,2′,6,6′-tetramethylpiperidine-N-oxyl (TEMPO). As the model compound of BC, cellobiose is incubated with laccase/TEMPO for disclosing the mechanism of enzymatic oxidation. The structure and property of the composite membranes of SF/BC are investigated by means of FTIR, XPS, DSC, and biocompatibility analysis. The results indicate that cellobiose might react with hexamethylenediamine and form Schiff bases. The concentration of amino group in SF solution noticeably decreased after laccase/TEMPO oxidation, indicating the occurrence of self-crosslinking of SF. After enzymatic grafting of SF, the content of atomic nitrogen on BC surface was increased compared to that of the control. Meanwhile, the composite membrane of SF/BC exhibits more satisfactory biocompatibility compared to BC, and it has potential applications in biomedical fields.     

Copper oxide-carbon nanotube (CuO/CNT) nanocomposite: Synthesis and photocatalytic dye degradation from colored textile wastewater

In this paper, CuO/CNT nanocomposite was synthesized and its photocatalytic dye degradation ability for colored textile wastewater was studied. The characteristics of the nanocomposite were investigated by XRD, SEM and FTIR. The photodegradation of Direct Red 31 (DR31) and Reactive Red 120 (RR120) by CuO/CNT in presence of H₂O₂ was investigated. Photocatalytic dye degradation was determined by UV-vis spectrophotometer. Effects of catalyst dosage, initial dye concentration and salt on photodegradation performance were studied. The photocatalytic dye degradation ability of pure CuO and CuO/CNT nanocomposite is 78 % and 89 % for DR31 and 70 % and 87 % for RR120, respectively. The results showed that CNT increased the photocatalytic activity of CuO. The presence of salt decreases dye degradation efficiency. The dye degradation kinetics by nanocomposite followed first-order kinetic model. The reaction rate at 0.005 g catalyst was 0.0137 and 0.0105 min^-1 for DR31 and RR120, respectively. It was found that the CuO/CNT nanocomposite as a photocatalyst could be used to degrade dyes from colored wastewater.