Graphene Oxide Carbon Nanotubes Research Articles

Breakthroughs in the Design of Novel Carbon-Based Metal Oxides Nanocomposites for VOCs Gas Sensing.

Nowadays, the detection of volatile organic compounds (VOCs) at trace levels (down to ppb) is feasible by exploiting ultra-sensitive and highly selective chemoresistors, especially in the field of medical diagnosis. By coupling metal oxide semiconductors (MOS e.g., SnO2, ZnO, WO3, CuO, TiO2 and Fe2O3) with innovative carbon-based materials (graphene, graphene oxide, reduced graphene oxide, single-wall and multi-wall carbon nanotubes), outstanding performances in terms of sensitivity, selectivity, limits of detection, response and recovery times towards specific gaseous targets (such as ethanol, acetone, formaldehyde and aromatic compounds) can be easily achieved. Notably, carbonaceous species, highly interconnected to MOS nanoparticles, enhance the sensor responses by (i) increasing the surface area and the pore content, (ii) favoring the electron migration, the transfer efficiency (spillover effect) and gas diffusion rate, (iii) promoting the active sites concomitantly limiting the nanopowders agglomeration; and (iv) forming nano-heterojunctions. Herein, the aim of the present review is to highlight the above-mentioned hybrid features in order to engineer novel flexible, miniaturized and low working temperature sensors, able to detect specific VOC biomarkers of a human’s disease.

Preparation of NH2-SH-GO/SWCNTs based on graphene oxide/single-walled carbon nanotubes for CO2 and N2 separation from blast furnace gas

The traditional molecular sieve membrane for gas separation is mostly prepared by zeolite, MOFs and other materials. Nano-carbon materials such as graphene and carbon nanotubes have been studied in the field of gas separation in recent years which have large specific surface area and high porosity. The performance of carbon nanotubes and graphene can be effectively improved by adding corresponding groups. A novel molecular sieve membrane was synthesized by sulfhydryl and amino-modified graphene oxide/oxidized single-walled carbon nanotubes (NH 2 -SH-GO/SWCNTs). The composite material was characterized by transmission electron microscopy, field emission scanning electron microscopy, X-ray diffraction, thermo-gravimetric analysis, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller specific surface area analyzers. The results reveal that laminated graphene oxide and tubular single-walled carbon nanotubes are intertwined and carbon nanotubes attach onto the surface of GO or intercalate into the GO sheets to form a spatial stereoscopic structure. TGA results demonstrate that the loading amount of amino and sulfydryl groups in NH 2 -SH-GO/SWCNTs is about 11.91 wt%. When the intake pressure of N 2 is 0.10 MPa, the permeability coefficient for N 2 passing through NH 2 -SH-GO/SWCNTs is 1829 Barrer. With the increase of temperature, permeability coefficient for N 2 decreases, while it increases as the intake pressure rises. The experimental results for mixed gases passing through NH 2 -SH-GO/SWCNTs show that, when P 0 = 0.10 MPa and T = 323 K, the permeability coefficient for CO 2 is 1896 Barrer, while that for CO is only 116 Barrer. At 323 K, selectivity for N 2 /CO, CO 2 /CO and CO 2 /N 2 is 39.2, 46.3, and 9.3, respectively. These results indicate that NH 2 -SH-GO/SWCNTs may be a promising molecular sieve membrane for gas separation. • Simultaneously separate CO 2 and N 2 from blast furnace gas. • Preparation of new style NH 2 -SH-GO/SWCNTs. • The permeability coefficient for N 2 is 1829 Barrer. • Selectivity for N 2 /CO, CO 2 /CO and CO 2 /N 2 is 39.2, 46.3, and 9.3, respectively.

Mechanochemical Preparation of Pd(II) and Pt(II) Composites with Carbonaceous Materials and Their Application in the Suzuki-Miyaura Reaction at Several Energy Inputs.

Pd(II) and Pt(II) composites with activated carbon (AC), graphene oxide, and multiwalled carbon nanotubes were prepared by ball milling and used as catalysts for the Suzuki-Miyaura reaction, under several energy inputs (mechanical grinding, conventional heating, and microwave irradiation). The catalytic composites were characterized by ICP-MS, BET, XPS analyses, TEM, and SEM. The average particle size of the prepared composites was estimated to be in the range of 6–30 nm, while the loadings of Pd and Pt did not significantly affect the surface area of the AC support due to the tendency to agglomerate as observed by the TEM analysis. The Pd/AC composites exhibit high mechanochemical catalytic activity in cross-coupling of bromobenzene and phenylboronic acid with molar yields up to 80% with TON and TOF of 222 and 444 h−1, respectively, achieved with Pd(4.7 wt%)-AC catalyst under the liquid assisted grinding for 0.5 h at ambient conditions, using cyclohexene as an additive.

Improved Electrical and Thermal Aging Properties of DBSA-Doped PANI Using MWCNT and GO

Electrical conductivity deterioration of polyaniline (PANI) at elevated temperatures has limited its applications for commercial usages. In this study we endeavored to improve the thermal aging resistance of PANI and its conductivity stability at elevated temperatures using a high molecular weight dopant, dodecylbenzenesulfonic acid (DBSA), along with the addition of carbon-based nanoparticles. DBSA-doped PANI (DBSA-PANI) and its nanocomposites with graphene oxide (PANI/GO) and multi-walled carbon nanotube (PANI/MWCNT) were prepared through in situ polymerization. The samples were aged at 90°C up to 1000 h and characterized by Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), scanning electron microscopy (SEM), and electrical conductivity measurements. It was observed that electrical conductivity deteriorates more rapidly in DBSA-PANI than in GO and MWCNT nanocomposites. The FTIR results confirmed a strong retention of DBSA groups in the nanocomposites after aging, but not for DBSA-PANI. This showed more stability of DBSA dopant in PANI/GO and PANI/CNT. The characteristic time (τ), as a criterion for thermal stability, was found to be 91, 172, and 295 h for DBSA-PANI, PANI/MWCNT, and PANI/GO, respectively. It was suggested that the retardation of the de-doping process is the major reason for the higher τ value and more electrical conductivity stability of PANI/GO. The obtained thermal stability for the electrical conductivity of DBSA doped PANI/GO nanocomposites was nearly 30 times higher than that of HCl-doped PANI.

Electronic Nose Based on Carbon Nanocomposite Sensors for Clove Essential Oil Detection.

This work describes the development of an electronic nose (e-nose) based on carbon nanocomposites to detect clove essential oil (CEO), eugenol (EUG), and eugenyl acetate (EUG.ACET). Our e-nose system comprises an array of six sensing units modified with nanocomposites of poly(aniline), graphene oxide, and multiwalled carbon nanotubes doped with different acids, dodecyl benzene sulfonic acid, camphorsulfonic acid, and hydrochloric acid. The e-nose presented an excellent analytical performance to the detected analytes (CEO, EUG, and EUG.ACET) with high sensitivity and reversibility. The limit of detection was lower than 1.045 ppb, with response time (<13.26 s) and recovery time (<106.29 s) and low hysteresis. Information visualization methods (PCA and IDMAP) demonstrated that the e-nose was efficient to discriminate the different concentrations of analyte volatile oil compounds. PM-IRRAS measurements suggest that the doping mechanism of molecular architectures is composed of a change in the oscillation energy of the characteristic dipoles and changes in the molecular orientation dipoles C═C and C═O at 1615 and 1740 cm-1, respectively. The experimental results indicate that our e-nose system is promising for a rapid analysis method to monitor the quality of essential oils.

Long term durability of solid-state supercapacitor based on reduced graphene oxide aerogel and carbon nanotubes composite electrodes

Extensive research efforts are dedicated to the development of high voltage aqueous supercapacitors to solve their low energy density concern. Whilst the operating voltage window is governed by decomposition of water (i.e. 1.23 V), this can be overcome by levelling potentials of oxygen (OER) and hydrogen (HER) evolution reactions. Here we report the design of a symmetrical supercapacitor (SC) in which the electrodes are fabricated from an ink containing reduced graphene oxide (rGO) aerogel, carbon nanotubes and binder by screen printing method on a conductive carbon cloth. For rGO aerogels, porous graphene oxide is prepared by freeze drying and reduced at 180 °C in vacuum. The solid-state supercapacitor is manufactured with two electrodes and a cation exchange electrolyte membrane and can operate stably at 1.6 V in a neutral environment. The initial supercapacitor power density increases from 61.7 to 602 W kg−1 when the current is raised from 0.1 to 1 A g−1. During the long-term durability test, the SC energy density decreases from 4.2 to 2.7 Wh kg−1 while the power density reduces from 61.7 to 53.1 W kg−1. The post-mortem analysis performed by X-ray photoelectron spectroscopy on electrodes demonstrats only small chemical modifications of positive electrode, while negative electrode is insignificantly altered, indicating promising perspectives for the usability of rGO-aerogel-based electrodes in practical supercapacitor applications. The self-discharge of the supercapacitor assessed after 10 000 charge/discharge cycles and 140 h floating at 1.6 V is mainly dependent on the activation contributions, likely due to Faradaic processes, which are more significant than that of diffusional ion species and voltage decay due to ohmic leakage mechanism. The solid-state rGO-based supercapacitor is found to be rather stable even under very stringent durability test, revealing low self-discharge rate that can promote possible commercial applications.

Controlled synthesis of reduced graphene oxide-carbon nanotube hybrids and their aqueous behavior

This paper reports the controlled synthesis of reduced graphene oxide-carbon nanotube (rGO-CNT) hybrids and their aqueous behavior. The CNTs were suspended in an aqueous dispersion of GO, and the GO-CNT hybrids were reduced in situ in a controlled fashion using nascent hydrogen. Several hybrids with oxygen content ranging from 26 to 2% were synthesized. The properties of the hybrids with low degree of reduction were closer to GO while those with high degree of reduction were closer to CNTs. Solubility, dispersibility, hydrophobicity, critical coagulation concentration (CCC value), and Zeta potential of the hybrids were studied and compared. Solubility of GO-CNT hybrid decreased from 6.2 to ~ 0 μg/ml after reducing oxygen content to 2%. Dispersibility of hybrids also decreased from 7.1 to 0.5 μg/ml after GO reduction. CCC value of hybrids in the presence of NaCl decreased from 16 in unreduced GO-CNT hybrid to 6 for one containing 7% oxygen, and equivalent decrease in the presence of MgCl2 was from 3 to 1. Additionally, as expected, the hydrophobicity of hybrids increased on reduction and the hydrophobicity index increased from − 3.2 to 7.4% as oxygen concentration decreased from 26 to 2%.

Development of Miniature Solid Contact Ion Selective Electrodes for in situ Instrumentation

AbstractUsing a standardized miniature format ion selective electrode, five different carbon based solid contact materials, including a novel commercially available graphene oxide assisted carbon nanotube dispersion (FlexipheneTM), were compared. The electromotive force (EMF) response, stability, and behavior following storage was evaluated. Bulk resistance for the novel graphene oxide/carbon nanotube (GO‐CNT) based ISE was observed to be 0.09±0.03 MΩ, which is two orders of magnitude lower than reported for either component in isolation. The results for previously described solid contact materials are in general agreement with the literature, and the tradeoffs between solid contact layer material choices are discussed. Performance of GO‐CNT solid contact ion selective electrodes were then evaluated in a 3D‐printed fluidic array to determine their suitability for future in situ instruments.

A flexible, printable, thin-film thermoelectric generator based on reduced graphene oxide–carbon nanotubes composites

Thermoelectric energy harvesting is one of the keystones of modern green renewable energy generation. Unfortunately, most conventional state-of-the-art inorganic semiconductor thermoelectric generators are expensive, fragile, and not flexible. Considering these limitations, we developed a flexible printable thermoelectric generator (TEG) with both n-type and p-type organic composites of reduced graphene oxide, carbon nanotubes, poly(3,4-ethylenedixoythiphene)–polystyrene sulfate, and lead sulfide composite materials. We constructed a TEG of ten alternating n–p pairs as a prototype with an effective area of 1.4 cm2 each, which generated 13 mV thermovoltage at operating temperature difference of 77 °C. It demonstrates that its fabrication is scalable, printable, and relatively simple, and the resultant structure is flexible, conformal, and reconfigurable.

Enhancement in mechanical properties of polyamide 66-carbon fiber composites containing graphene oxide-carbon nanotube hybrid nanofillers synthesized through in situ interfacial polymerization

Polyamide 66 (PA66)/carbon fiber (CF) composites with acyl chloride-functionalized GO (AGO) and carbon nanotubes (CNTs) as hybrid fillers were prepared through in situ interfacial polymerization. The optimal ratio of AGO to CNTs in terms of hydrogen bonding in the composites was determined to be 2:1 via thermochemical analyses of the as-prepared PA66/AGO-CNT composites. The optimized hybrid filler-reinforced PA66/CF composites showed improvements in the interfacial shear strength, tensile strengh and storage modulus by 160, 136 and 300%, respectively, compared to the control sample, as well as high damping properties due to an enhanced transcrystalline interphase. The superior interfacial bonding between CF and PA66 is attributed to hydrogen bonding, enhanced dispersion, and the mechanical interlocking effect induced by AGO-CNT hybrids, which lead to effective energy absorption and load transfer.

Microstructure-Electrochemical Behaviour Correlation for Nico-GO and Nico-Mwcnts Composite Coatings

NiCo coatings are widely used in sensors, actuators and as protective coatings. Recent studies have shown that addition of foreign particles like Al2O3, SiC and TiO2 promotes grain randomization and refinement resulting in improved corrosion resistance performance. In the present work, NiCo coating containing varying amount of graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) were electrodeposited over mild steel substrate. Microstructure and corrosion behavior of these composite coatings were then studied as a function of the volume fraction of the secondary additives. NiCo-GO & NiCo-CNT composite coating were characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) for phase identification, morphology and composition respectively. Potentiodynamic polarization studies and electrochemical impedance spectroscopy (EIS) studies in 3.5 wt. % NaCl solution revealed that the corrosion behavior of the coatings was very sensitive to the concentration of GO/ MWCNTs in the coating matrix. With continuous increase in the amount of GO/CNT in the coatings, the corrosion resistance first increased followed by a decrease, indicating possibility of an optimum with respect to the amount of the additives for achieving high corrosion resistance performance. On analyzing the electrolytic bath solution, we observed that nickel ions (Ni+2) showed preferential deposition onto the graphene oxide sheets resulting in a compositional heterogeneity near and far from the graphene-metal interface in the electrodeposited coating microstructure. This compositional segregation led to a change in the relative abundance of low angle and high angle boundaries in the coating microstructure. Electron backscattered diffraction (EBSD) technique was used to study the type of grain boundaries, strain in the grain and average grain size (area) of the samples (prepared using focused ion beam FIB). The data revealed that the samples exhibiting maximum corrosion resistance (optimum CNT/ GO concentrations) also had the highest fraction of low angle grain boundaries (LAGBs) with no additional strain in the matrix. Further increase in GO concentration resulted in more grains with high misorientation angle. In case of CNTs addition, the coatings were found to be hydrophobic in nature with a grain growth along low energy (111) direction. Figure 1

Reduced Graphene Oxide/Multiwalled Carbon Nanotube Composite Decorated with Fe₃O₄ Magnetic Nanoparticles for Electrochemical Determination of Hydrazine in Environmental Water.

In the present work, a reduced graphene oxide and multiwalled carbon nanotube (RGO/MWCNTFe₃O₄) composite decorated with Fe₃O₄ magnetic nanoparticles was prepared as an electrochemical sensor. The surface morphology of the prepared composite was identified by scanning electron microscopy and X-ray diffraction. The electrochemical properties of the GCE/RGO/MWCNT-Fe₃O₄ electrode were investigated by electrochemical impedance spectroscopy, cyclic voltammetry and amperometry. The GCE/RGO/MWCNT-Fe₃O₄ electrode exhibited higher electrocatalytic performance towards the oxidation of hydrazine. In the optimal conditions, the GCE/RGO/MWCNT-Fe₃O₄ electrode showed a wide linear range (0.15-220 μM), low limit of detection (LOD) (0.75 μM), and high sensitivity (2.868 μA μM-1 cm-2). The prepared GCE/RGO/MWCNT-Fe₃O₄ electrode also had excellent repeatability, selectivity, and reproducibility. The practical application of the electrode was confirmed with various spiked water samples and demonstrated acceptable recovery.

Enzyme-free and label-free strategy for electrochemical oxaliplatin aptasensing by using rGO/MWCNTs loaded with AuPd nanoparticles as signal probes and electro-catalytic enhancers

An innovative label free electrochemical aptasensor was developed for the analysis of oxaliplatin (OXAL) for the first time. The DNA oligonucleotide (aptamer) was successfully fabricated, by covalently attaching the amino terminus of the functional DNA on the glassy carbon electrode (GCE) surface modified with reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs) loaded with AuPd nanoparticles (AuPd NPs@rGO/MWCNTs/GCE). The stepwise assembly process of aptasensor on AuPd NPs@rGO/MWCNTs/GCE was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The aptamer-OXAL complex formation led to inhibition the electron transfer of Fe(CN)63−/4- on the electrode interface, which was clearly observed by decreasing the peak current of the redox probe. Furthermore, we managed to quantitatively measure OXAL by adding different concentrations of OXAL, while monitoring the decrease of differential pulse voltammogram (DPV) responses of the redox probe. Under the optimized conditions, the electrochemical aptasensor exhibited a linear range of 0.1–170.0 nmol L−1 with LOD of 60.0 pmol L−1. Next, we successfully applied the aptasensor calibrated system to determine OXAL in pharmaceutical injection and human biological samples.

Furcellaran nanocomposite films: The effect of nanofillers on the structural, thermal, mechanical and antimicrobial properties of biopolymer films

Graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) were added to furcellaran films (FUR). Silver nanoparticles (AgNPs) were prepared by reducing AgNO3 using a FUR matrix as the stabilising agent. The structure and surface morphology of nanocomposite films were obtained using FTIR, SEM and XRD. The molecular weights of furcellaran chains were estimated using HPSEC-MALLS-RI. Characterisation of the films was undertaken to analyse their physical, mechanical and structural properties. SEM analysis revealed that GO, MWCNTs and AgNPs were evenly distributed throughout the FUR surface. FUR + AgNP films showed antimicrobial activity against bacteria and fungi. P. aeruginosa, E. faecalis and S. aureus were the most affected with effective growth inhibition using the disc diffusion method. In the study, the effect of nanofillers on the structural, thermal, mechanical and antimicrobial properties of furcellaran films as potential materials for food packaging is presented.

Stretchable strain sensors based on conductive coating cracks with improved interfacial adhesion by wet phase separation treatment

Stretchable strain sensors have drawn plenty of attention due to their importance and necessity in high-technology areas. In this study, we fabricated a series of thermoplastic polyurethane (TPU) film-based stretchable strain sensors with a conductive hybrid sensing layer of reduced graphene oxide (RGO) and multiwalled carbon nanotubes (CNT) by simple coating methods. Meanwhile, we developed a kind of roughening method based on wet phase separation to form interpenetrating micropores on the surface of the TPU film, which overcomes the sliding and overlapping of the RGO/CNT sensing layer by improving the mechanical interlocking between the hybrid sensing layer and the elastic substrate. Owing to the improved adhesion between the sensing layer and the elastomeric substrate, the stretchable sensor shows good sensitivity (gauge factor (GF) = 75 at 50% strain), linearity (logarithmic GF = 10 during 0–50% strain), and stability (more than 1000 stretching–releasing cycles at a strain of 50%). These high performances suggest the potential application of our strain sensor in the detection of human body movements, personal health monitoring, and other kinds of human–machine interfaces.

A dual CoNi MOF nanosheet/nanotube assembled on carbon cloth for high performance hybrid supercapacitors

Layered-structure MOF is a promising material for electrochemical energy storage applications. However, low conductivity hinders their electrochemical performance. Herein, a hierarchical layered-structure CoNi-MOF with ultrathin nanosheets and nanotube arrays are directly grown on carbon cloth (CC) with Co(OH)2 as both template and Co source. The synthesized CC/CoNi-MOF shows high areal capacity of 1.01 C cm−2 at 2 mA cm−2, while keeps 61.4% capacity retention at 15 mA cm−2. A hybrid supercapacitor is successfully fabricated with CC/CoNi-MOF as positive electrode and reduced graphene oxide-carbon nanotube as negative electrode, possessing a maximum areal capacitance of 846 mF cm−2 at 1 mA cm−2, a high energy density of 55.5 Wh kg−1 at 175.5 W kg−1, and excellent cycling stability (96.5% after 10000 cycles). This work may pave a new way for designing MOF based materials with similar structure for high performance supercapacitors.

On-the-fly rapid immunoassay for neonatal sepsis diagnosis: C-reactive protein accurate determination using magnetic graphene-based micromotors

Based on the exceptional and new opened biosensing possibilities of self-propelled micromotors, a micromotor-based immunoassay (MIm) has smartly been designed for C-reactive protein (CRP) determination in plasma of preterm infants with sepsis suspicion.The design of the micromotors involved the electrosynthesis of a carbon-based outer layer (for antibody functionalization), an intermediate Ni layer (for magnetic guidance and stopped flow operations) and PtNPs inner catalytic layer (for catalytic bubble propulsion).Micromotors biofunctionalization on the outer layer (using carbon black (CB), reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs), and biocompatible propulsion capabilities, were carefully studied. Magnetic rGO/Ni/PtNPs micromotors exhibited the most efficient and reproducible (CV = 9%) anti-CRP functionalization, controlled stopped-flow operations as well as efficient bubble propulsion (1% H2O2, 1,5% NaCh, speed 140 μm s-1). Analytical performance of MIm was excellent, allowing the direct (without dilution), sensitive (LOD = 0.80 μg/mL), and accurate CRP determination (Er = 1%) in hardly available preterm babies’ plasma samples with suspected sepsis using very low volumes (<10 μL) and in just 5 min of on-the-fly bioassay.Overall, the results obtained allowed the fast and reliable sepsis diagnostics in preterm babies’ individuals with suspected sepsis, not only proving the usefulness of the approach as its potential utilization as point-of-care device for clinical analysis but drawing new horizons in extremely low sample volumes-based diagnostics.

Developing the Ternary ZnO Doped MoS2 Nanostructures Grafted on CNT and Reduced Graphene Oxide (RGO) for Photocatalytic Degradation of Aniline

Transition metal sulfide semiconductors have achieved significant attention in the field of photocatalysis and degradation of pollutants. MoS2 with a two dimensional (2D) layered structure, a narrow bandgap and the ability of getting excited while being exposed to visible light, has demonstrated great potential in visible-light-driven photocatalysts. However, it possesses fast-paced recombination of charges. In this study, the coupled MoS2 nanosheets were synthesized with ZnO nanorods to develop the heterojunctions photocatalyst in order to obtain superior photoactivity. The charge transfer in this composite is not adequate to achieve desirable activity. Therefore, heterojunction was modified by reduced graphene oxide (RGO) nanosheets and carbon nanotubes (CNTs) to develop the RGO/ZnO/MoS2 and CNTs/ZnO/MoS2 ternary nanocomposites. The structure, morphology, composition, optical and photocatalytic properties of the as-fabricated samples were characterized through X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM), Energy-Dispersive X-ray (EDX), elemental mapping, Photoluminescence (PL), Ultraviolet–Visible spectroscopy (UV-VIS), and Brunauer-Emmett-Teller (BET) techniques. The photo-catalytic performance of all samples was evaluated through photodegradation of aniline in aqueous solution. The combination of RGO or CNTs into the ZnO/MoS2 greatly promoted the catalytic activity. However, the resulting RGO/ZnO/MoS2 ternary nanocomposites showed appreciably increased catalytic performance, faster than that of CNTs/ZnO/MoS2. Charge carrier transfer studies, the BET surface area analysis, and the optical studies confirmed this superiority. The role of operational variables namely, solution pH, catalyst dosage amount, and initial concentration of aniline was then investigated for obtaining maximum degradation. Complete degradation was observed, in the case of pH = 4, catalyst dosage of 0.7 g/L and aniline concentration of 80 ppm, and light intensity of 100 W. According to the results of trapping experiments, hydroxyl radical was found to be the main active species in the photocatalytic reaction. Meanwhile, a plausible mechanism was proposed for describing the degradation of aniline upon ternary composite. Moreover, the catalyst showed excellent reusability and stability after five consecutive cycles due to the synergistic effect between its components. Total-Organic-Carbon concentration (TOC) results suggested that complete mineralization of aniline occurred after 210 min of irradiation. Finally, a real petrochemical wastewater sample was evaluated for testing the catalytic ability of the as-fabricated composites in real case studies and it was observed that the process successfully quenched 100% and 93% of Chemical Oxygen Demand (COD) and TOC in the wastewater, respectively.

Covalently bonded polyaniline-reduced graphene oxide/single-walled carbon nanotubes nanocomposites: influence of various dimensional carbon nanostructures on the electrochromic behavior of PANI

In this paper, water-dispersible and covalently bonded polyaniline-carbon nanostructures, including polyaniline-reduced graphene oxide (PANI-rGO), polyaniline-single-walled carbon nanotubes (PANI-SWCNTs), and polyaniline-reduced graphene oxide/single-walled carbon nanotube (PANI-rGO/SWCNTs) nanocomposites, were synthesized by grafting PANI onto p-phenylenediamine (PPD)-functionalized graphene oxide (GO) or single-walled carbon nanotubes (SWCNTs) using polystyrene sulfonate (PSS) as a macromolecular dopant agent. The structures and morphologies of the PANI, PANI-rGO, PANI-SWCNTs, and PANI-rGO/SWCNTs nanocomposites were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The cyclic voltammetry and UV–vis spectra were performed on an electrochemical workstation and a UV–vis spectrometer, respectively. The results show that the electrochromic and electrochemical properties of nanocomposites can benefit from the high conductivity of SWCNTs and the abundant active sites of rGO. When SWCNTs and rGO work together, their respective shortcomings are overcome, allowing the nanocomposite to exhibit the best electrochemical and electrochromic properties. The optical contrast increased from 0.38 for PANI to 0.52 for PANI-rGO/SWCNTs. The coloring and bleaching times decreased from 2.59 s and 2.39 s, respectively, for PANI to 1.33 and 0.78 s, respectively, for PANI-rGO/SWCNTs. The charge transfer resistance (Rct) decreased from 135 Ω for PANI to 30 Ω for PANI-rGO/SWCNTs. The synergistic effect of PANI, rGO, and SWCNTs can significantly improve the electrochromic ability of PANI. Electrochromic properties of covalently bonded polyaniline-reduced graphene oxide/single walled carbon nanotubes nanocomposites. A high performance electrochromic material was prepared using polyaniline (PANI) and two different dimensional carbon nanostructures, single-walled carbon nanotubes (SWCNTs) and reduced graphene oxide (rGO) as the components. The covalent bond was introduced to interface between PANI and two carbon nanostructures to form a three-dimensional conductive network. Owing to the high electron conduction through directly connected covalent bond and loose molecular chain aggregation brought by two various dimensional carbon nanostructure, PANI-rGO/SWCNTs nanocomposites exhibit superior electrochemical and electrochromic properties (high optical contrast and short switching time) compared with PANI.

Highly selective carbon nanotube‐coupled graphene oxide‐incorporated polydimethylsiloxane membrane for pervaporative membrane bioreactor ethanol production

AbstractBACKGROUNDIn this work, a pervaporation membrane bioreactor (PVMBR) with the novel ethanol permselective membrane was used to achieve ethanol production with high yield. For this purpose, ethanol produced by Saccharomyces cerevisiae from glucose and pervaporation was performed via dense hydrophobic polydimethylsiloxane (PDMS) having carbon nanotube‐graphene oxide (CNT‐GO) mixed matrix membrane. Different percentages of CNT‐GO (0, 0.25, 0.5, 0.75, and 1) were loaded in polymer matrix. Synthesized membranes were analyzed using FESEM, AFM, FTIR and XRD.RESULTSThe bonding of groups in CNT‐GO, that was synthesized in this work, and membranes was characterized and confirmed using FTIR test. Considering the existence of 0.75 wt% of CNT‐GO in PDMS showed the highest ethanol selectivity of 22.5 in synthetic ethanol‐water solution, this incorporation was selected to use in PVMBR. The high ethanol selectivity was proved using XRD patterns. Also, FESEM indicated the optimum dispersion of nanoparticles at 0.75% of loading and AFM proofed the optimum surface roughness at this percentage.CONCLUSIONSThe results showed that maximum ethanol production in PVMBR was achieved after 44 h with productivity of 0.5g.l−1.h−1 in feed side and 9.89 g.l−1.h−1 in permeate side. In fact, PVMBR enhanced the ethanol concentration up to 26 times. © 2020 Society of Chemical Industry