Oxidation Of Multi-walled Carbon Nanotubes Research Articles

Evaluation of the electrochemical response of Saccharomyces cerevisiae using screen-printed carbon electrodes (SPCE) modified with oxidized multi-walled carbon nanotubes dispersed in water – Nafion®

The evaluation of the electrochemical determination of Saccharomyces cerevisiae was carried out using a screen-printed carbon electrode (SPCE) modified with Nafion-dispersed oxidized multi-walled carbon nanotubes (OMWCNT). The morphology was studied using scanning electron microscopy (SEM), showing a complete modification of the surface with the nanotubes and yeast interaction with them instead of the graphite surface. The redox couple Fe(CN)64−/Fe(CN)63− was used to determine the electroactive area, the heterogeneous transfer constant, and the Nafion® effect. Results showed increases in electroactive area and heterogeneous transfer constant of 146% and 20.4%, respectively, due to the presence of nanotubes. Studies of the Nafion® effect showed that the polymeric membrane affects the electroactive area but not the heterogeneous transfer constant. Studies of the scan rate effect show that yeast oxidation is an irreversible mixed control process. As the concentration and scan rate increased, the anodic potential shifted toward more anodic values. The relationship between yeast concentration and the anodic current density (current/electroactive area) of yeast showed a linear range between 0.61 and 7.69 g L−1, the limit of detection (LOD) and the limit of quantification (LOQ) were 0.17 g L−1, and 0.61 g L−1, respectively, and the sensibility obtained was 0.03 μA L g−1 mm−2. These results show that with the screen-printed carbon electrodes it is possible to improve the electrochemical determination of this microorganism, enhancing the analytical parameters and quantification, allowing greater portability and decreasing measurement times and associated waste.

Corrosion resistance enhancement of a sol-gel coating by incorporation of modified carbon nanotubes: Artificial neural network (ANN) modeling and experimental explorations

A computational method of data analysis based on an artificial neural network (ANN) has been proposed to model the behavior of a sol-gel coating modified with different amounts of oxidized multi-walled carbon nanotubes (O-MWCNT). The constructed ANN model utilized a single hidden-layer perceptron. The Levenberg–Marquardt algorithm optimization procedure was applied as a learning algorithm. In this model, the input variables were the different concentrations of O-MWCNT, the immersion time, and the real part of the impedance, and consequently, the imaginary part of the impedance was considered as the output variable. Then, the accuracy of the optimized model was evaluated using the correlation coefficient and schematically comparing the simulated data with the experimental ones in the Nyquist diagrams. Furthermore, the protection performance of the sol-gel layer was enhanced by the incorporation of O-MWCNTs. To this end, the different concentrations of the O-MWCNTs up to 0.9 % wt./wt. have been added to a silane layer, and the performance was followed by electrochemical exploration using electrochemical impedance spectroscopy (EIS). The results revealed the improvement of the protective performance of the silane coating by increasing the content of the O-MWCNTs in the matrix, followed by the enhancement of barrier properties. Moreover, the polarization curves, in agreement with the AC impedance spectra, reflected the significant decrease in the corrosion current density by employing more content of O-MWCNTs in the silane-based coatings.

Heterostructures of Cut Carbon Nanotube-Filled Array of TiO2 Nanotubes for New Module of Photovoltaic Devices.

In this work, a new photovoltaic device was prepared. The device uses titanium (Ti) foil/TiO2 nanotubes as the photoanode and multi-walled carbon nanotubes (MWCNTs) as a photosensitizer. Titanium dioxide nanotube arrays (TiO2-NTs) were prepared by one-step anodic oxidation. Cut-MWCNTs with a length of less than 100 nm were obtained by the mixed-acid oxidation of MWCNTs. The two materials were combined to form a TiO2-NTs@cut-MWCNT heterostructure by electrophoresis. TiO2-NTs@cut-MWCNTs were characterized by field-emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD), which showed that the two materials were effectively combined. We fabricated the heterostructure into a photovoltaic device, showing an enhanced photocurrent response and an efficiency of 0.0138%, and explained this phenomenon by performing UV-vis absorption spectroscopy and electrochemical tests. It is hoped that this work can provide a reference value for the application of carbon nanotubes in photovoltaic devices.

PPSU dual layer hollow fiber mixed matrix membranes with functionalized MWCNT for enhanced antifouling, salt and dye rejection in water treatment

AbstractLoose nanofiltration dual layer hollow fiber membranes (DLHFM) were prepared from polyphenylsulfone (PPSU) with a thin contact mixed matrix membrane (MMM) outer layer containing functionalized multiwalled carbon nanotubes (MWCNT). Two types of MWCNT were used; oxidized MWCNT (OMWCNT) and polyethyleneimine (PEI) functionalized MWCNT (PEI‐MWCNT). Z potential measurements indicate that OMWCNT and PEI‐MWCNT were negatively charged, being OMWCNT most negative. Na2SO4, MgSO4, and methylene blue (MB) rejection was enhanced due to OMWCNT and PEI‐MWCNT incorporation in DLHFM outer layer. Enhanced hydrophilicity and negatively charge mixed matrix DLHFM layer was the key factor for a better mixed matrix DLHFM performance. The best salt and MB rejection was found in those membranes prepared with (OMWCNT) followed by (PEI‐MWCNT) compared with neat PPSU membranes. An increase of 113% and 100% in Na2SO4 and MB rejection respectively was attained in DLHFM with 0.04 wt%, OMWCNT (relative to dope's weight) in comparison with the neat PPSU membrane. Antifouling test for bovine serum albumin (BSA) and MB showed better performance also for the mixed matrix DLHFM containing OMWCNT's. In antifouling tests, a 4.4% and 25% flux recovery increase for MB and BSA respectively was obtained in DLHFM with 0.04 wt% OMWCNT compared with the neat PPSU DLHFM.

Tungsten doped neodymium oxide–carbon nanotubes based voltammetric platform as a highly efficient electrocatalyst and sensing material for monitoring albuterol

• An ultrasonication-assisted platform based on W-Nd 2 O 3 /MWCNTs/GCE was constructed. • The platform presented efficient catalytic activity for the oxidation of albuterol. • A linear range of 6.6×10 -8 M-2.0×10 -5 M with an LOD of 2.37×10 -9 M was obtained. • Reasonable values of recoveries with RSD% were obtained for the sample analysis. • The proposed method can be used for monitoring albuterol against its illegal use. An ultrasonication-assisted construction of a voltammetric platform based on tungsten doped neodymium oxide-multiwalled carbon nanotubes (W-Nd 2 O 3 /MWCNTs) on a glassy carbon electrode (GCE) has been developed. The platform presented efficient electrocatalytic activity for the electro-oxidation of albuterol in comparison to several other electrodes and exhibited highly improved voltammetric behaviour for albuterol in the presence of uric acid. The proposed platform enabled a linear working range from 6.6 × 10 −8 M to 2.0 × 10 −5 M and a detection limit (LOD) of 2.37 × 10 −9 M for albuterol. A mean recovery of 101.1 % with an RSD% of 1.8 obtained for ventolin nebules and mean recoveries between 98.8 % and 101.7 % with acceptable RSD’s% values for the standard addition of albuterol in urine were obtained at W-Nd 2 O 3 -MWCNTs/GCE. Such a successful method of analysis at W-Nd 2 O 3 -MWCNTs/GCE was shown to make the proposed procedure of high interest for especially controlling and monitoring albuterol against its illegal use in sport competitions.

Enhanced Visible‐light Photocatalytic Dye Degradation Ability of CdS/O‐CNTs Nanocomposites

AbstractThe rapid developpment of industrialization and urbanization has caused extensive environmental pollution, especially water pollution. Here, a bud‐like shaped CdS (cadmium sulfide), with O‐CNTs (oxidized multiwalled carbon nanotubes) homogeneously embedde (BCO), were synthesized by a facile hydrothermal process. The surface properties of the composites and the photocatalytic performances were studied systematically. The photocatalytic degrading anionic dye Methyl orange (MO) and cationic dye Rhodamine B (RhB) under visible light (λ≥420 nm) unveiled that BCO nanocomposites exhibited much better photocatalytic decolorization activity than bud‐like shaped CdS. Due to the delaying time of electron recombination to the hole and the participation of holes (h+) and⋅superoxide radicals (⋅O2−) by loading O‐CNTs, BCO‐3 wt% could decolorize 98.5 % RhB in 30 min and 95.5 % MO in 90 min, implying potential applications prospect.

Young's Modulus and Vickers Hardness of the Hydroxyapatite Bioceramics with a Small Amount of the Multi-Walled Carbon Nanotubes.

The Vickers hardness and Young’s modulus of the hydroxyapatite (HA) bioceramics with a small amount of the multi-walled carbon nanotubes (MWCNTs) were studied by using ultramicrotester Shimadzu for dynamic tests DUH-211. Small concentrations of MWCNTs were from 0.05 to 0.5 wt.%. The argon inert atmosphere and vacuum condition were taken for the prevention of the MWCNTs oxidation. The Brunauer–Emmett–Teller (BET) surface area SBET of the HA-MWCNTs composites was determined by thermal adsorption-desorption of nitrogen. It was found that for HA-MWCNTs sintered in the Ar atmosphere, an increase in the concentration of nanotubes up to 0.5 wt.% leads to a decrease in porosity near 3 times in comparison to HA without MWCNTs additives. The small amount of additives of multi-walled carbon nanotubes leads to an increase in hardness of 1.3 times and compression strength of composite and compression strength of composite that is comparable in absolute values with the literature data of enamel hardness (3–5 GPa) and compression strength (95–370 MPa). The absolute values increase close to linearly with the increase of nanotube concentrations. The Young’s modulus of sintered composite slightly changes with the variation of concentrations of nanotubes and close to the enamel (75–100 GPa). The ratio of plastic work to total work and the ratio of elastic (reversible) work to the total work of deformation of composite HA/MWCNTs are practically constant at a studied range of MWCNTs concentration. The additives of the multi-walled carbon nanotubes lead to both an increase in the elasticity index of ~1.5 times and an increase in the resistance to plastic deformation of ~3 times, which improved the tribological performance of the surface. Plastic and elastic (reversible) work slightly changed.

Development of High Flux Nanocomposite Polyphenylsulfone/Oxidized Multiwalled Carbon Nanotubes Membranes for Ultrafiltration Using the Systems with Critical Solution Temperatures.

The study deals with the investigation of the effect of the modification of polyphenylsulfone (PPSU) flat sheet membranes for ultrafiltration using oxidized multiwalled carbon nanotubes (O-MWCNT) in order to enhance membrane permeability and antifouling performance. The effect of O-MWCNT loading to the PPSU-polyethylene glycol (PEG-20,000, Mn = 20,000 g·mol−1)-polyvinylpyrrolidone (PVP K-30, Mn = 40,000 g·mol−1)-N-methy-2-pyrrolidinone (NMP) colloid systems on the phase state and viscosity was studied. It was found that PPSU-PEG-20,000-PVP K-30-O-MWCNT-NMP colloid systems feature a gel point (T = 35–37 °C) and demixing temperature (T = 127–129 °C) at which two bulk phases are formed and a polymer system delaminates. According to the study of the phase state and viscosity of these colloid systems, a method for the preparation of high flux PPSU membranes is proposed which includes processing of the casting solution at the temperature higher than gel point (40 °C) and using a coagulation bath temperature lower than gel point (25 °C) or lower than demixing temperature (40 °C and 70 °C). Membrane structure, topology and hydrophilic-hydrophobic balance were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and water contact angle measurements. The effect of coagulation bath temperature and O-MWCNT concentration on the membrane separation and antifouling performance in ultrafiltration of human serum albumin and humic acids solutions was studied. It was found that the modification of PPSU ultrafiltration membranes by O-MWCNTs yielded the formation of a thinner selective layer and hydrophilization of the membrane surface (water contact angle decreased from 53–56° for the reference PPSU membrane down to 33° for the nanocomposite membrane with the addition of 0.19 wt.% O-MWCNT). These changes resulted in the increase in membrane flux (from 203–605 L·m−2·h−1 at transmembrane pressure of 0.1 MPa for the reference membrane up to 512–983 L·m−2·h−1 for nanocomposite membrane with the addition of 0.19 wt.% O-MWCNT depending on coagulation bath temperature) which significantly surpasses the performance of PPSU ultrafiltration membranes reported to date while maintaining a high level of human serum albumin rejection (83–92%). It was revealed that nanocomposite membrane demonstrated better antifouling performance (the flux recovery ratio increased from 47% for the reference PPSU membrane up to 62% for the nanocomposite membrane) and higher total organic carbon removal compared to the reference PPSU membrane in humic acids solution ultrafiltration.

A study on retention of MWCNT in robocasted MWCNT-HAP scaffold structures using vacuum sintering technique and their characteristics

Bioceramic scaffolds are being widely employed in bone tissue engineering applications for their ability to interact with host tissues without inducing any toxicity. Additionally, bioceramics possess good biocompatibility, osteointegration, osteoinduction, and biodegradation characteristics. Hydroxyapatite (HAP) is one such bioceramic known to exhibit closeness to natural bone in terms of chemical composition. The present reports additive manufacturing of HAP and Multiwalled carbon nanotubes (MWCNTs) reinforced HAP scaffold structures for bone tissue engineering applications using the Robocasting technique. Carboxymethyl Cellulose (CMC) was employed as the polymeric binder in this study to prepare the highly viscous HAP and CNT-HAP slurry ideal for robocasting of the scaffold structures. Different percentages of MWCNT (0.5, 1 and 2 wt%) incorporated into the developed CNT-HAP scaffold structures and were vacuum sintered at 1000 °C for 15 min. Vacuum sintering was found to effectively prevent oxidation of MWCNT which is subjected to decomposition at temperatures above 400 or 500 °C in Oxygen atmosphere as per literature. Further, the retention of MWCNTs in the developed CNT-HAP structures post sintering was confirmed using FESEM imaging. The mechanical characterizations revealed that 0.5CNT-HAP structures exhibited highest compression strength (3.36 ± 0.67 MPa) in comparison to 1CNT-HAP and 2CNT-HAP structures. Also, the in vitro biological characterizations demonstrated that the developed CNT-HAP scaffold structures were cytocompatible and remained stable for about 35 days at 37 °C.

Electrochemical determination of dopamine and uric acid with covalent organic frameworks and Ox-MWCNT co-modified glassy carbon electrode

Covalent organic frameworks (COFs) have received tremendous interest due to their structural diversity and versatility. These unique physicochemical properties make them exhibit great application potential in the field of electrochemical sensor. In this study, an imine bond-linked COF with porosity and large specific surface area was fabricated by a dehydration condensation reaction between 1, 3, 5-tris(4-formylphenyl)benzene (TFPB) and 1, 3, 5-tris(4-aminophenyl) benzene (TAPB) and combined with high electrical conductivity of oxidized multi-walled carbon nanotube (Ox-MWCNT). The structure of the COF and the resulted composite material were confirmed through a series of characterization techniques, including Fourier-transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy and thermogravimetric analysis, then a co-modified glassy carbon electrode was constructed for simple, sensitive and selective electrochemical recognition of dopamine (DA) and uric acid (UA). The fabricated electrochemical sensor displayed a strong current response to both DA and UA in the phosphate buffer solution (PBS) at pH = 6.5. The synergistic effect between COFs and Ox-MWCNT effectively improved the analytical sensitivity for the target analytes. Under optimized experimental conditions, the method showed good performance for DA and UA in the concentration range of 0.6–250.0 μM with low detection limits of 0.073 μM and 0.063 μM (S/N = 3), respectively. Moreover, the proposed sensor exhibited high selectivity, longtime stability, desirable repeatability and acceptable reproducibility and can be used to analyze simultaneously DA and UA in biological and medicine samples with satisfactory results. Our work not only provides a simple way to detect DA and UA quantitatively in real samples, but also offers a new platform for COF-based composite application in electrochemical sensing . • TFPB-TAPB-COF is prepared via a simple solvothermal method. • TFPB-TAPB-COF/Ox-MWCNT/GCE is fabricated for sensing of dopamine (DA) and uric acid (UA). • The sensor has low detection limits and wide linear ranges for detection DA and UA. • The sensor is successfully applied to the determination of DA and UA in real samples.

Preparation, Characterization, and Electrochemical Performance of the Hematite/Oxidized Multi-Walled Carbon Nanotubes Nanocomposite.

In this research work, a hematite (α-Fe2O3) nanoparticle was prepared and then mixed with oxidized multi-walled carbon nanotubes (O-MWCNT) to form a stable suspension of an α-Fe2O3/O-MWCNTs nanocomposite. Different characterization techniques were used to explore the chemical and physical properties of the α-Fe2O3/O-MWCNTs nanocomposite, including XRD, FT-IR, UV-Vis, and SEM. The results revealed the successful formation of the α-Fe2O3 nanoparticles, and the oxidation of the MWCNT, as well as the formation of stable α-Fe2O3/O-MWCNTs nanocomposite. The electrochemical behaviour of the α-Fe2O3/O-MWCNTs nanocomposite was investigated using cyclic voltammetry (CV) and linear sweep voltammetry (LSV), and the results revealed that modification of α-Fe2O3 nanoparticles with O-MWCNTs greatly enhanced electrochemical performance and capacitive behaviour, as well as cycling stability.

Effects of Length and Oxidation of Multi-walled Carbon Nanotubes on the Mechanical and Electrical Properties for Epoxy Matrix Composites

Effects of Length and Oxidation of Multi-walled Carbon Nanotubes on the Mechanical and Electrical Properties for Epoxy Matrix Composites

Investigation on performance of adding manganese dioxide into graphene oxide electrode film

ABSTRACT In this paper, the preparation of electroactive polymers artificial muscle electrode membrane with graphene oxide and manganese dioxide as the main research material to explore the performance of electrode membrane. Using sodium alginate as matrix, manganese dioxide with different mass ratios was compounded with graphene oxide and sodium alginate aqueous solution to prepare electrode films. The effects of manganese dioxide on the morphology and electrochemical properties of electrode films were discussed. From the test results, it can be seen that the scanning electron microscopy results show that the manganese dioxide layer is uniformly compounded on graphene oxide. With the increase of manganese dioxide/graphene oxide mass ratio, the specific capacitance of the electrode film gradually increases and the impedance increases. With the increase of driving voltage, the deflection displacement gradually increases and then shows a downward trend. When the mass ratio of manganese dioxide/graphene oxide is 0.1(# 2), the maximum deflection displacement is 14.1 mm, which is 2.76 times of the minimum deflection displacement of the sample (# 1). The specific capacitance of the electrode film was increased by 1.57 times to 15.62 F · g−1. Finally, the performance difference of graphene oxide electrode film and multi-walled carbon nanotube electrode film on EAP artificial muscle was explored.

The Influence of Forced Convective Heat Transfer on Hybrid Nanofluid Flow in a Heat Exchanger with Elliptical Corrugated Tubes: Numerical Analyses and Optimization

The capabilities of nanofluids in boosting the heat transfer features of thermal, electrical and power electronic devices have widely been explored. The increasing need of different industries for heat exchangers with high efficiency and small dimensions has been considered by various researchers and is one of the focus topics of the present study. In the present study, forced convective heat transfer of an ethylene glycol/magnesium oxide-multiwalled carbon nanotube (EG/MgO-MWCNT) hybrid nanofluid (HNF) as single-phase flow in a heat exchanger (HE) with elliptical corrugated tubes is investigated. Three-dimensional multiphase governing equations are solved numerically using the control volume approach and a validated numerical model in good agreement with the literature. The range of Reynolds numbers (Re) 50 < Re < 1000 corresponds to laminar flow. Optimization is carried out by evaluation of various parameters to reach an optimal case with the maximum Nusselt number (Nu) and minimum pressure drop. The use of hybrid nanofluid results in a greater output temperature, a higher Nusselt number, and a bigger pressure drop, according to the findings. A similar pattern is obtained by increasing the volume fraction of nanoparticles. The results indicate that the power of the pump is increased when EG/MgO-MWCNT HNFs are employed. Furthermore, the thermal entropy generation reduces, and the frictional entropy generation increases with the volume fraction of nanoparticles and Re number. The results show that frictional and thermal entropy generations intersect by increasing the Re number, indicating that frictional entropy generation can overcome other effective parameters. This study concludes that the EG/MgO-MWCNT HNF with a volume fraction (VF) of 0.4% is proposed as the best-case scenario among all those considered.

Co-Doped Magnesium Oxychloride Composites with Unique Flexural Strength for Construction Use.

In this study, the combined effect of graphene oxide (GO) and oxidized multi-walled carbon nanotubes (OMWCNTs) on material properties of the magnesium oxychloride (MOC) phase 5 was analyzed. The selected carbon-based nanoadditives were used in small content in order to obtain higher values of mechanical parameters and higher water resistance while maintaining acceptable price of the final composites. Two sets of samples containing either 0.1 wt. % or 0.2 wt. % of both nanoadditives were prepared, in addition to a set of reference samples without additives. Samples were characterized by X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, and energy dispersive spectroscopy, which were used to obtain the basic information on the phase and chemical composition, as well as the microstructure and morphology. Basic macro- and micro-structural parameters were studied in order to determine the effect of the nanoadditives on the open porosity, bulk and specific density. In addition, the mechanical, hygric and thermal parameters of the prepared nano-doped composites were acquired and compared to the reference sample. An enhancement of all the mentioned types of parameters was observed. This can be assigned to the drop in porosity when GO and OMWCNTs were used. This research shows a pathway of increasing the water resistance of MOC-based composites, which is an important step in the development of the new generation of construction materials.

Electrochemical determination of Saccharomyces cerevisiae sp using glassy carbon electrodes modified with oxidized multi-walled carbon nanotubes dispersed in water –Nafion®

The electrochemical behavior of Saccharomyces cerevisiae sp was studied using a glassy carbon electrode (GCE) modified with Nafion-dispersed oxidized multi-walled carbon nanotubes (OMWCNT). The morphology was studied using scanning electron microscopy (SEM), showing that the yeast sticks to the carbon nanotube surface instead of the glassy carbon surface. The redox couple Fe(CN)64−/Fe(CN)63− was used to determine the electroactive area and the heterogeneous transfer constant, which increased 80.5% and 108% respectively by the presence of nanotubes. The studies of the pH effect showed that the anodic potential decreases at alkaline pH and that the highest current intensity occurs at a pH value of 7.00. Studies of the scan rate effect have shown that yeast oxidation is an irreversible mixed control process in which two electrons participate. The relationship between yeast concentration and the anodic current density was studied using different electrochemical techniques obtaining the best analytical parameters through chronoamperometry. The linear range was between 3.36 and 6.52 g L−1, the limit of detection (LOD) and the limit of quantification (LOQ) were 0.98 g L−1 and 3.36 g L−1 respectively, and the sensibility obtained was 0.086 μA L g−1 mm−2. These results show that the multi-walled carbon nanotubes in water and Nafion® allow obtaining an anodic signal corresponding to the yeast, which facilitates its quantification through electrochemical methodologies, favoring the reduction of analysis times and costs compared with other techniques.

Development of MoS2/O-MWCNTs/PES blended membrane for efficient removal of dyes, antibiotic, and protein

In this work, a nanocomposite of MoS2 nanosheets and oxidized multi-walled carbon nanotubes (O-MWCNTs) was prepared using the hydrothermal method. The successful synthesis of the MoS2/O-MWCNTs nanocomposite was further confirmed using a scanning electron microscope (SEM), energy dispersive X-Ray dot mapping, and X-ray diffraction analysis. The synthesized nanocomposite was used as a nanoadditive for the improvement of polyethersulfone (PES) polymeric membrane. The phase inversion route was used to prepare MoS2/O-MWCNTs blended membranes containing different amounts of nanocomposite (0–1 wt%). The morphology of the prepared membranes was studied using SEM and atomic force microscopy techniques. Asymmetric structure with small pores at the top layer and well-developed large finger-like pores and macro voids at the sublayer can be observed in fabricated membranes. The hydrophilicity enhancement of the PES membrane in the existence of nanocomposite was verified by the contact angle test. The modified membrane containing 0.75 wt% of MoS2/O-MWCNTs exhibited improved permeability of 64.1 L/m2 h bar, and high pollutants removal of 93.5% for reactive blue 19, 97.5% for rifampicin, 98.4% for reactive red 195, and 99% for bovine serum albumin, with enhanced flux recovery ratio of 60.8%. Moreover, the stability of the blended membrane in the long-time operation makes it a promising candidate to be applied in the treatment of textile and industrial wastewaters.

Unveiling the role of oxidative treatments on the electrochemical performance of carbon nanotube-based cotton textile supercapacitors

Herein, all-solid-state textile supercapacitors (TSCs) were produced using a cost-effective readily-available natural fabric as substrate (cotton) and different types of oxidized multiwalled carbon nanotubes (MWCNTs) as electrode nanomaterials. The MWCNT oxidative treatments were performed using three agents, HNO3, H2SO4 and HNO3/H2SO4, to unveil their role on the performance and energy storage mechanism of the resulting TSCs. The TSCs based on the oxidized MWCNTs exhibited up to 106% enhanced energy density than the device based on pristine MWCNTs (up to 3.48 W h kg−1 vs. 1.69 W h kg−1) and up to 98% capacitance retention over 5000 cycles. A balance between the extent of oxidation of the MWCNTs, their specific surface area and electrical conductivity was required to boost the performance. The MWCNT oxidation with HNO3 promoted the highest increase of the specific surface area, the creation of redox-active surface oxygen-based groups and optimum surface oxygen loading (4.0%). The synergy between these features endowed a pseudocapacitive contribution to the energy storage mechanism, leading to the TSC with the best performance. This work constitutes a breakthrough on the rational design of easily scalable TSCs directly produced on natural non-conductive substrates using tuned oxidized MWCNT electrode nanomaterials to meet the demands of the thriving Era of wearable electronics.

Development of zinc oxide-multi-walled carbon nanotube hybrid nanofluid for energy-efficient heat transfer application: A thermal lens study

This paper addresses the need for developing an energy-efficient hybrid nanofluid with zinc oxide–multi-walled carbon nanotube (ZnO-MWCNT) for overcoming the bottleneck of efficient heat transfer in thermal systems. The concentration-dependent thermal diffusivity modifications are analyzed using the highly sensitive mode mismatched thermal lens technique. The hybrid composite is prepared by the solid-state mixing and annealing of a pure multi-walled carbon nanotube (MWCNT) and zinc oxide (ZnO), synthesized by the solution combustion method. The composite formation is studied by structural, morphological, and optical characterization techniques. Among the three nanofluids ZnO, MWCNT, and ZnO-MWCNT, the composite exhibits a drastic enhancement in thermal diffusivity at a lower solid volume fraction of 0.047 mg/ml containing 0.009 mg/ml of MWCNT. All the nanofluids show an optimum concentration beyond which the thermal diffusivity decreases with the nanoparticle concentration. Thus, this study suggests the potential application of ZnO-MWCNT hybrid nanofluids in thermal system design to enhance internal combustion engines' efficiency during cold-start.

Manganese Deposition Content in Carbon Nanotubes Based Filters: Energy Dispersive X-ray and Rutherford Backscatter Spectrometry Investigations

Carbon nanotubes (CNTs) based filters have a prospective advantage compared to the commercial filters due to their lightweight and ability to work without electricity or heat. The manganese (Mn) removal from aqueous solutions by oxidized multi-walled carbon nanotubes (O-MWCNTs) was investigated. The filtration performance was studied under ambient conditions: the solution pH, the initial manganese concentration, and the MWCNT-filter mass. The samples of MWCNT-filters were investigated using energy dispersive X-ray spectroscopy (EDS) and rutherford backscatter spectrometry (RBS) to account for the manganese content within the MWCNT-filter. These techniques were conducted to study the oxidation effect on the morphology of MWCNTs and evaluate the oxygen functional groups and the average diameter distribution. Based on these examinations, the competence of Mn removal may exceed 91% for 50 ppm initial concentration of Mn, proposing that functionalized MWCNTs is a promising filter. The Mn removal was achieved at low pH with removal enhancement at the pH of 2. Functionalized MWCNTs based filters are promising candidate for heavy metal ions removal from industrial wastewater.