Activity Of Multi-walled Carbon Nanotubes Research Articles

Enhanced antibacterial activity of multi-walled carbon nanotubes loaded with hot-melt extruded Mulberry leaf silver nanoparticles

We suggest an antibacterial nanoplatform composed of multi-walled carbon nanotubes (MWCNTs) coated with mesoporous silica decorated with silver nanoparticles (AgNPs) via an N-[3-(trimethoxysilyl)propyl]ethylenediamine (TSD)-mediated method. In this system, the external mesoporous silica shell enhances the dispersion of MWCNTs to increase their contact area with bacterial cell walls. Meanwhile, the multiple mesoporous voids in the silica layer serve as a microreactor for on-site synthesis of small-sized and uniformly distributed AgNPs, thereby enhancing the antibacterial activity. Mulberry leaf (ML) extract was used to reduce Ag ions. In this process, hot melt extrusion (HME) was applied to increase the active ingredients of the ML extract. To prevent loss of ML components due to the heat and pressure applied during HME treatment, several excipients, including whey protein isolate, were mixed, and added. Compared with ML AgNPs and mesoporous silica-coated MWCNTs decorated with AgNPs (MWCNT-Ag), the MWCNT-Ag@ML (MWCNT-ML) exhibited stronger antibacterial against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and methicillin-resistant S. aureus (MRSA). Therefore, this nano platform is a potential antibacterial agent and therapeutic agent for drug-resistant infections.

Controlled synthesis of MWCNTs/V2O5 nanocomposite by hydrothermal approach for adsorption and photodegradation processes.

The current paper outlines the synthesis of pristine multi-wall carbon nanotubes (PMWCNTs)/Vanadium pentoxide V2O5 and functionalized multi-wall carbon nanotubes (FMWCNTs)/V2O5 nanocomposite for photocatalytic applications. The FMWCNTs were obtained by the oxidizing agents (H2SO4 and HNO3) to introduce the oxygenated functional groups. The samples were synthesized by hydrothermal approach and investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy analysis (EDX), and Fourier transform infrared spectroscopy (FTIR). The photocatalytic activity of multi-wall carbon nanotubes (MWCNTs), FMWCNTs/V2O5, and PMWCNTs/V2O5 nanocomposites was assessed via methylene blue (MB) degradation from water under visible light. The results demonstrated that the removal efficiency of MB by PMWCNTs, FMWCNTs/V2O5, and PMWCNTs/V2O5 could reach 90.4, 98.9, and 94.9%, respectively. It was noticed that MB adsorption and photodegradation tend to follow pseudo-second-order kinetics. The mechanism of MB photodegradation by FMWCNTs/V2O5 nanoparticles was explained. MWCNTs/V2O5 nanocomposites will allow further applications to remove other dyes and contaminants from wastewater.

Surface antibacterial activity of multi-walled carbon nanotubes with an intrinsic and radiation-induced disorder

Surface antibacterial activity of multi-walled carbon nanotubes with an intrinsic and radiation-induced disorder

Preparation of Multi-walled Carbon Nanotubes/Polyvinyl Alcohol Conducting Hydrogel Electrode Films and Electrocatalysis of Biological Small Molecules

According to the good conductivity and electrocatalytic activity of multi-walled carbon nanotubes (MWCNTs) and the hydrogel properties of polyvinyl alcohol (PVA), MWCNTs and PVA double-network porous hydrogels were designed. MWCNTs/ PVA conductive hydrogels were prepared by electrophoretic deposition (EPD) and freeze-thaw cyclic crosslinking process. The electrochemical performance and microstructure of MWCNTs/PVA electrode film showed that MWCNTs/PVA hydrogel electrode film has a highly hydrophilic porous conducting hydrogel network structure. Although MWCNTs/PVA hydrogel electrode film has no obvious catalytic activity on glucose in PBS solution. However, it has obvious catalytic activity on dopamine and ascorbic acid.

Fe-CONTAINING CARBON NANOTUBES AS CATALYSTS IN THE AEROBIC OXIDATION REACTIONS OF DECALIN AND TETRADECANE

This article studies the catalytic activity of multi-walled carbon nanotubes (MWCNTs) in the oxidation reactions of aliphatic and polycyclic hydrocarbons is studied. In order to determine the catalytic activity, MWCNTs catalysts containing 22.8% Fe each were used. Catalyst samples were synthesized from propane gas under optimal conditions determined by CVD method. The experiments were performed at 5 different temperatures (60, 80, 100, 120, 1400C) for 2 hours. No significant change in the oxidation reaction of both hydrocarbons was observed at relatively low temperatures. In the oxidation of decalin, when the reaction temperature rises to 1200C and 1400C, oxidation has already taken place, and the rate of the reaction is directly proportional to the increase in temperature. The same trend can be seen in the oxidation reaction of tetradecane at MWCNTs with temperatures of 120 and 1400C. However, unlike decalin, the MWCNTs sample in tetradecane oxidation showed optimal catalytic performance at 1200C. However, at these temperatures, where oxidation occurs, the oxidation of decalin and tetradecane in an environment without a catalyst is almost non-existent

Insights into the electrocatalytic behavior of nitrogen and sulfur co-doped carbon nanotubes toward oxygen reduction reaction in alkaline media

This study examines the effect of pretreatment and doping to enhance the ORR activity of multiwalled carbon nanotubes (MWCNTs). Melamine and thio-urea are chosen as precursors for mono and co-doping, respectively. A series of samples with pristine and pretreated CNTs are prepared and characterized physicochemically by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) and electrochemically by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The obtained results show that co-doping is an effective way for improving ORR activity, due to the synergistic effect of N and S for changing the charge and spin density, respectively. Moreover, thio-urea favors the proportion of pyridinic and graphitic nitrogen configurations within doped samples. As a consequence, our synthesis method gives samples with superior ORR activity. The maximum ORR activity is obtained for NS-OX-CNTs which shows an over potential of 0.95 V vs RHE at 0.1 mA/cm2, which is comparable to Pt/C (0.98 V vs RHE). The electron transfer number (n) is calculated as 3.9 at 0.4 V which suggests that the ORR proceeds through a dominant 4 e− path. These comparable half-cell results to that of Pt/C pave the way for further testing as cathode materials for anion exchange membrane fuel cells (AEMFC).Graphical abstract

Evaluating the origin of the electrocatalytic activity of multiwalled carbon nanotubes towards Vitamin D3 oxidation

Multiwalled carbon nanotubes (MWCNT) have been reported to be electrocatalytic towards a wide range of analytes. However, the electrocatalytic property is often wrongly attributed, and its origin is often due to the impurities included in the carbon nanotubes. The present report systematically explores the origin of the electrocatalytic nature of multiwalled carbon nanotubes towards Vitamin D3 oxidation. It was found that, in addition to the edge sites, the oxygen functional groups present on the MWCNTs play a vital role in the electro-oxidation of Vitamin D3. The analytical parameters obtained using MWCNT modified electrodes for Vitamin D3 sensing are also presented.

Is the Antibacterial Activity of Multi-Walled Carbon Nanotubes (MWCNTs) Related to Antibiotic Resistance? An Assessment in Clinical Isolates.

Antimicrobial resistance has spread globally, compromising the treatment of common infections. This feature is particularly harmful for nosocomial pathogens that can survive on hospital surfaces. Research studies have been conducted to evaluate new materials that are able to counteract the microbial growth and the colonization of the hospital environment. In this context, nanotechnologies have showed encouraging applications. We investigated the antibacterial activity of multi-walled carbon nanotubes (MWCNTs), both pristine (p) and functionalized (f), at concentrations of 50 and 100 μg mL−1, against bacterial strains isolated from hospital-acquired infections, and this activity was correlated with the antibiotic susceptibility of the strains. The inhibiting effect of MWCNTs occurred for both types and doses tested. Moreover, f-MWCNTs exerted a greater inhibiting effect, with growth decreases greater than 10% at 24 h and 20% at 48 h compared to p-MWCNTs. Moreover, a lower inhibitory effect of MWCNTs, which was more lasting in Gram-positives resistant to cell wall antibiotics, or temporary in Gram-negatives resistant to nucleic acid and protein synthesis inhibitors, was observed, highlighting the strong relation between antibiotic resistance and MWCNT effect. In conclusion, an antimicrobial activity was observed especially for f-MWCNTs that could therefore be loaded with bioactive antimicrobial molecules. However, this potential application of CNTs presupposes the absence of toxicity and therefore total safety for patients.

Catalytic activity of multi-walled carbon nanotubes decorated with tungsten trioxides nanoparticles against 4-nitrophenol

The fabrication of metallic oxide nanoparticles in a matrix material for use in catalysis has piqued researchers' curiosity, particularly in the aqueous phase. In this work, Multi-walled carbon nanotubes decorated with tungsten trioxide nanocomposites structure exhibit improved catalytic reduction activity in comparison to individual MWCNTs. the nanocomposites structure was prepared in just one step by infrared pulsed laser ablation (Nd:YAG laser, 1064 nm) of tungsten plate immersed in liquid media of functionalized multi-walled carbon nanotubes. Furthermore, the properties of composite hydrogels have been studied by X-ray diffraction, scanning electron microscope, transmission electron microscope, Fourier transforms infrared spectroscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectrometer, and thermal gravimetric analysis. The effective reduction of 4-Nitrophenol to 4-Aminophenol by NaBH4 was studied in the existence of the prepared nanocomposite structure of WO3-decorated MWCNTs. This nanocomposite demonstrated the large-scale possible use of organic catalytic oxidation and disposal of wastewater.

Profibrotic Activity of Multiwalled Carbon Nanotubes Upon Prolonged Exposures in Different Human Lung Cell Types

Abstract Introduction: The expanding use of multiwalled carbon nanotubes (MWCNTs) in various consumer and industrial products has raised concerns regarding the potential health risks following the ...

Multi-walled carbon nanotube forests covered with atomic-layer-deposited ruthenium layers for high-performance counter electrodes of dye-sensitized solar cells

Abstract On account of the high surface area and good catalytic activity of multi-walled carbon nanotube (MWNT) forests, they have great potential for use as alternative materials to conventional Pt/fluorine-doped tin oxide (FTO) counter electrodes (CEs). Nevertheless, the inferior charge collection efficiency of MWNT forest CEs is a drawback that needs to be overcome. Here, we uniquely introduce a Ru layer on MWNT forests by a typical atomic layer deposition (ALD) process. Under an optimal ALD cycle number of 600, Ru layers directly connect vertically grown MWNTs by acting as their bridges while also retaining the microporous structure of the MWNTs. As a result, deposition of the Ru layer under the optimal conditions causes a decrease in the resistances of as-synthesized MWNT forests (charge transfer resistance Rct: from 155.3 Ω to 4.12 Ω; series resistance Rs: from 205.1 Ω to 12 Ω); these decreased resistances are better than even those of Pt/FTO CEs (Rct = 14.2 Ω and Rs = 17.6 Ω). Dye-sensitized solar cells with the optimally deposited Ru/MWNT forest CEs show performances equivalent to those of devices with Pt/FTO CEs on account of the excellent Rct and Rs values of the former CEs.

Influence of Surface Roughness on the Lubrication Effect of Carbon Nanoparticle-Coated Steel Surfaces

In the present study, a systematic evaluation of the influence of the surface roughness on the lubrication activity of multi-wall carbon nanotubes (MWCNT) and onion-like carbon (OLC) is performed. MWCNT and OLC are chosen as they both present an sp2-hybridization of carbon atoms, show a similar layered atomic structure, and exhibit the potential to roll on top of a surface. However, their morphology (size and aspect ratio) clearly differs, allowing for a methodical study of these differences on the lubrication effect on systematically varied surface roughness. Stainless steel platelets with different surface finishing were produced and coated by electrophoretic deposition with OLC or MWCNT. The frictional behavior is recorded using a ball-on-disk tribometer, and the resulting wear tracks are analyzed by scanning electron microscopy in order to reveal the acting tribological mechanisms. It is found that the lubrication mechanism of both types of particles is traced back to a mixture between a rolling motion on the surfaces and particle degradation, including the formation of nanocrystalline graphitic layers. This investigation further highlights that choosing the suitable surface finish for a tribological application is crucial for achieving beneficial tribological effects of carbon nanoparticle lubricated surfaces.

Catalytic Activity of Multiwalled Carbon Nanotubes in Acetylene Hydrogenation

AbstractThe hydrogenation of acetylene was investigated on multiwalled carbon nanotubes (MWCNTs) with an average diameter of 35 nm and prepared by chemical vapor deposition from ethylene. The MWCNT structure and surface‐oxygen‐containing functional groups were verified by transmission electron microscopy, scanning electron microscopy, X‐ray photoelectron spectroscopy, Raman spectroscopy, and Boehm titration. Significant differences in the surface functionalities of the MWCNTs were found before and after catalysis, but the morphology of the MWCNTs did not change. During catalysis, the MWCNTs are characterized by a large number of defects and the surface is functionalized with hydroxy and carbonyl groups. The MWCNTs demonstrated high selectivity towards ethylene formation. The formation of methane was not recorded. Our study indicates that acetylene hydrogenation proceeds according to a Langmuir–Hinshelwood mechanism.

Factors Determining the Catalytic Activity of Multi-walled Carbon Nanotubes in the Decomposition of Diacyl Peroxides in Non-aqueous Media (DPDec)

The catalytic activity of multi-walled carbon nanotubes (CNT) with different surface chemistry was investigated in the decomposition of benzoyl and lauroyl peroxides (BP and LP respectively) at room temperature in non-aqueous media. Calculated diffusion coefficients (D eff ) indicate that catalysis is not limited by internal diffusion. CNT demonstrate a moderate catalytic activity that ordering in the raw: N-CNT > CNTini > CNTox. Surface chemistry analysis displays the dependence of catalytic ability of CNT on their surface electron donor properties. Operation stability experiments and TPD–MS analysis reveal that reactions proceeding via the single electron transfer (SET) mechanism.

Significant enhancement of photocatalytic activity of multi-walled carbon nanotubes modified WSe2 composite

Flowerlike WSe2 and multi-walled carbon nanotubes modified WSe2 (CNT/WSe2) composite has been successfully synthesized via a facile one-pot solvothermal reaction. The morphologies, structures and photocatalytic activities were characterized by scanning electron microscopy, transmission electron microscope, X-ray diffraction, and UV–vis absorption spectroscopy, respectively. Compared to bare WSe2, the characterization results show that the CNT/WSe2 composite exhibits enhanced photocatalytic activity in photocatalytic degradation of organic dye methyl orange (MO) under visible light irradiation. The enhanced photocatalytic activity is attributed to the CNTs can reduce electron-hole pair recombination and efficiently inhibit the aggregation of WSe2 for fully exposing the active edges. In addition, a possible mechanism of CNT/WSe2 composite for degradation of MO molecules is proposed and discussed.

Electrocatalytic water treatment using carbon nanotube filters modified with metal oxides.

This study examined the electrocatalytic activity of multi-walled carbon nanotube (CNT) filters for remediation of aqueous phenol in a sodium sulfate electrolyte. CNT filters were loaded with antimony-doped tin oxide (Sb-SnO2; SS) and bismuth- and antimony-codoped tin oxide (Bi-Sb-SnO2; BSS) via electrosorption at 2V for 1h and then assembled into a flow-through batch reactor as anode-cathode couples with perforated titanium foils. The as-synthesized pristine CNT filters were composed of 50-60-nm-thick tubular carbons with smooth surfaces, whereas the tubes composing the SS-CNT and BSS-CNT filters were slightly thicker and bumpy, because they were coated with SS and BSS particles ~50nm in size. Electrochemical characterization of the samples indicated a positive shift in the onset potential and a decrease in the current magnitude in the modified CNT filters due to passivation and oxidation inhibition of the bare CNT filters. These filters exhibited a similar adsorption capacity for phenol (5-8%), whereas loadings of SS and BSS enhanced the degradation rate of phenol by ~1.5 and 2.1 times, respectively. In particular, the total organic carbon removal performance and mineralization efficiency of the BSS-CNT filters were approximately twice those of the bare CNT filters. The BSS-CNT filters also exhibited an enhanced oxidation of ferrocyanide [FeII(CN)64-], which was not adsorbed onto the CNT filters. The enhanced electrocatalytic performance of the modified CNT filters was attributed to an effective generation of OH radicals. The surfaces of the filters were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy.

Size effects of multi-walled carbon nanotubes on the electrochemical oxidation of propionic acid derivative drugs: Ibuprofen and naproxen

The superior electrochemical activity of multi-walled carbon nanotubes (MWCNTs) of shorter dimensions towards the oxidation of propionic acid derivative drugs, namely ibuprofen (IBF) and naproxen (NPX), is presented. A glassy-carbon electrode was modified with MWCNTs of different sizes (diameter×length: 100–170nm×5–9μm and 6–9nm×5μm, corresponding to LD- and SD-MWCNTs, respectively, larger and shorter diameter). Cyclic voltammetry of the SD-MWCNT-modified electrode showed a 200–300mV decrease in the overpotential of oxidation reactions of both drugs and an increase in current (2 to 3.5-fold) in comparison with the LD-MWCNT-modified and unmodified electrodes. Similarly, the amperometric determination of both drugs using the SD-MWCNT-modified electrode presented an increase in sensitivity in comparison with LD-MWCNT-modified electrode (2 to 2.8-fold). Improved performance of the SD-MWCNT-modified electrode was in agreement with electrochemical impedance spectroscopy measurements. These results indicate the higher electrocatalytic activity of SD-MWCNTs, which can be explained by the increased defect density revealed by Raman spectroscopic measurements. Additionally, we report the first amperometric method for IBF determination using the SD-MWCNT-modified electrode, with a linear range from 10 to 1000μmolL−1, detection limit of 1.9μmolL−1, precision of 4%, and accuracy attested by capillary electrophoresis analyses.

MWCNTs as a catalyst in oxy-steam reforming of methanol

The catalytic activity of multi-walled carbon nanotubes (MWCNTs) in oxy-steam reforming of methanol (ASRM) was investigated for the first time.

Catalyst free low temperature synthesis and antioxidant activity of multiwalled carbon nanotubes accessed from ghee, clarified butter of cow׳s milk

Multiwalled carbon nanotubes (MWCNTs) have been synthesized at low temperature on silicon substrates in a thermal chemical vapor reactor from ghee, clarified butter from cow׳s milk as the carbon source without using any catalyst. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) analyses revealed bundles of micrometer long MWCNTs with an interlayer separation of 0.33nm consisting of 25 concentric graphene sheets with outer and inner diameters of 27.45 and 13.68nm, respectively. The powder X-ray diffraction (XRD) pattern showed a hexagonal structure of graphitic carbon with average crystallite size of 4.6nm. The MWCNTs exhibited pronounced antioxidant activity.

Electrocatalytic activity of multiwalled carbon nanotubes decorated by silver nanoparticles for the detection of halothane

Commercially available multiwalled carbon nanotubes (CNTs) were decorated by size-controlled and stable silver nanoparticles (NPs) using a sol immobilisation technique. Silver nanoparticles were in some cases protected by polyvinyl-alcohol (PVA). These materials were used to prepare different glassy carbon modified electrodes, which were tested in the electrochemical reduction of the anaesthetic halothane in two different solvents: water and acetonitrile. A different behaviour in the two different solvents is observed: silver nanoparticles are essential for the electrocatalytic activity in water while CNT are useless; in acetonitrile silver and CNT present a similar catalytic behaviour. The best modified electrode was used for the electroanalytical detection of anaesthetic halothane in both solvents. The use of PVA protective polymer for silver NPs allows better electroanalytical performances due to the protection from oxidation, fouling products and interferents.