Functionalization Of Multi-walled Carbon Nanotubes Research Articles

Femtosecond pulsed laser microscopy: a new tool to assess the in vitro delivered dose of carbon nanotubes in cell culture experiments

BackgroundIn vitro models are widely used in nanotoxicology. In these assays, a careful documentation of the fraction of nanomaterials that reaches the cells, i.e. the in vitro delivered dose, is a critical element for the interpretation of the data. The in vitro delivered dose can be measured by quantifying the amount of material in contact with the cells, or can be estimated by applying particokinetic models. For carbon nanotubes (CNTs), the determination of the in vitro delivered dose is not evident because their quantification in biological matrices is difficult, and particokinetic models are not adapted to high aspect ratio materials. Here, we applied a rapid and direct approach, based on femtosecond pulsed laser microscopy (FPLM), to assess the in vitro delivered dose of multi-walled CNTs (MWCNTs).Methods and resultsWe incubated mouse lung fibroblasts (MLg) and differentiated human monocytic cells (THP-1) in 96-well plates for 24 h with a set of different MWCNTs. The cytotoxic response to the MWCNTs was evaluated using the WST-1 assay in both cell lines, and the pro-inflammatory response was determined by measuring the release of IL-1β by THP-1 cells. Contrasting cell responses were observed across the MWCNTs. The sedimentation rate of the different MWCNTs was assessed by monitoring turbidity decay with time in cell culture medium. These turbidity measurements revealed some differences among the MWCNT samples which, however, did not parallel the contrasting cell responses. FPLM measurements in cell culture wells revealed that the in vitro delivered MWCNT dose did not parallel sedimentation data, and suggested that cultured cells contributed to set up the delivered dose. The FPLM data allowed, for each MWCNT sample, an adjustment of the measured cytotoxicity and IL-1β responses to the delivered doses. This adjusted in vitro activity led to another toxicity ranking of the MWCNT samples as compared to the unadjusted activities. In macrophages, this adjusted ranking was consistent with existing knowledge on the impact of surface MWCNT functionalization on cytotoxicity, and might better reflect the intrinsic activity of the MWCNT samples.ConclusionThe present study further highlights the need to estimate the in vitro delivered dose in cell culture experiments with nanomaterials. The FPLM measurement of the in vitro delivered dose of MWCNTs can enrich experimental results, and may refine our understanding of their interactions with cells.

Insights into the effect of polymer functionalization of multiwalled carbon nanotubes in the design of flexible strain sensor

In the background of designing a polymer nanocomposite based flexible strain sensors, homogenized dispersion of nanofillers remain challenging due to the trade-off between upholding of inherent characteristics of nanofillers and stable dispersion of nanofillers in the polymer matrix. This study provides an approach of balancing the stable dispersion of nanofillers and maintain the inherent characteristics of nanofibers by the method of polymer functionalization. Herein, two oppositely charged polymers polystyrene sulfonate sodium salt (PSS) and poly-diallyl-dimethyl-ammonium chloride (PDDA) are used separately to functionalize the multiwalled carbon nanotubes (CNT) and it dispersed in poly (vinylidene difluoride) (PVDF) polymer matrix to get flexible nanocomposite strain sensor to investigate both electrical conductivity and the gauge factor. PSS functionalized CNT (PSS-CNT) shows better dispersion than the PDDA-CNT in PVDF matrix. Besides, the electrical conductivity of PVDF/PSS-CNT (0.44 ± 0.02 Scm−1) is about 28 times higher than the PVDF/PDDA-CNT, and the gauge factor of PVDF/PSS-CNT (9.8 ± 0.3) is 2-fold higher than the PVDF/PDDA-CNT. The stable dispersion of PSS-CNT is due to the repulsive nature existing between the individual CNTs caused by the attachment of charged polymer functional groups as same as intrinsic functional groups of the pristine CNT. This work signifies the role of synergy between the charged particles in the functional groups and charged nature of the filler influencing the performance of flexible strain sensors. The detailed investigation using various techniques reveals significance of selection of suitable polymers for functionalization by showing its influence in the context of designing the high-performance flexible strain sensor.

Improved CO2 adsorption properties through amine functionalization of multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWCNT) with different functionalities (standard–; OH–; and COOH– functionalized) are chemically modified with N1-(3-trimethoxysilylpropyl)diethylenetriamine (DETASi) aiming to enhance their CO2 adsorption/separation properties. The grafting of the DETASi groups to the surface of the MWCNT samples is studied by X-ray photoelectron spectroscopy (XPS), operando thermogravimetric analysis - infrared spectroscopy (TGA-IR), –196 °C N2-sorption isotherms, and scanning electron microscopy (SEM). A comprehensive overview of the reaction mechanism and samples structure/composition is provided. It was found that the aforementioned functionalities highly influence the physical–chemical and the textural properties of the DETASi modified-MWCNT materials, impacting in the DETASi functionalization degree and its distribution on the sample. Amount (by TGA-IR) and homogeneity (by SEM) of the organosilicon group in the functionalized samples increases with the increase of the functionalities in the parent MWCNT materials. Standard-MWCNT and OH– functionalized MWCNT showed to be unable to adsorb CO2, while COOH– modified MWCNT adsorbed just 0.1% at 1 bar and 30 °C. At the same adsorption conditions, DETASi modification of the MWCNT materials enhanced the CO2 adsorption capacity, with the maximum CO2 uptake (2.11%) for COOH-MWCNT functionalized with DETASi. The selectivity for CO2/N2 separation was also improved after DETASi grafting reaction, with the highest value (1.89%) observed for the standard-MWCNT material modified with DETASi. In general, the increase of the DETASi amount and of the microporosity in the functionalized MWCNT sorbents is accompanied by an improvement of the CO2 adsorption-separation properties. The water vapor adsorption indicated that the standard-MWCNT sample modified with DETASi is resistant to the presence of water and its presence (water vapor of ~3.2 kPa) can improve the CO2 uptake.

Covalently immobilized cobalt Phthalocyanine@MWCNT PDMS hollow fiber membrane for highly selective, reversible and bio-inspired oxygen transport

Facilitated oxygen transport is an effective strategy for the oxygen transport that may enhance the oxygen permeance and its selectivity, which may provide oxygen rich permeate that can be used in medical applications as in the present COVID-19 pandemic situation for providing the sufficient oxygen to the patients. This study presents the bio-inspired oxygen transport by covalently bonded Cobalt Phthalocyanine complex anchored on multi walled carbon nanotube (MWCNT) via axial ligand, incorporated in PDMS hollow fiber membranes with 0.05, 0.1, 0.5 and 1.0 wt % loadings. Successful functionalization of MWCNT was confirmed by Raman spectroscopy and X-ray photoelectron spectroscopy. The membranes were thoroughly characterized by using FE-SEM with elemental mapping, ATR-IR, DSC and TGA analysis. It demonstrated facilitated oxygen transport through the covalently immobilized Cobalt complex of the membrane with high oxygen permeance of 49 GPU as well as exceptional oxygen selectivity of 17 at 0.5 wt % Cobalt Phthalocyanine@ MWCNT loading. These values are highest among the known Cobalt complex based hollow fiber composite membranes in the literature suggesting its best utility in selective oxygen concentration for practical applications.

Performance Analysis of Reinforced Epoxy Functionalized Carbon Nanotubes Composites for Vertical Axis Wind Turbine Blade.

Synthetic materials using epoxy resin and woven Kevlar fiber nanocomposites were fabricated in the presence of functionalized multiwalled carbon nanotubes (F-MWCNTs). Kevlar-reinforced epoxy nanocomposites were designed to manufacture a small blade of vertical axis wind turbines (VAWT). It is important to estimate the deflection of the versatile composite turbine blades to forestall the blades from breakage. This paper investigates the effect of F-MWCNTs on mechanics and deflection of reinforced epoxy composites. The outcomes show that the mixing of F-MWCNTs with epoxy resin using a sonication process has a significant influence on the mechanical properties. Substantial improvement on the deflections was determined based on finite element analysis (FEA). The vortices from the vertical axis wind turbines (VAWTs) blades have a negative impact on power efficiency, since small blades are shown to be effective in reducing tip vortexes within the aerospace field. To support the theoretical movement of the VAWT blade, modeling calculations and analyzes were performed with the ANSYS code package to achieve insight into the sustainability of epoxy nanocomposites for turbine blade applications below aerodynamic, gravitational, and centrifugal loads. The results showed that the addition of F-MWCNTs to epoxy and Kevlar has a significant effect on the bias estimated by finite element analysis. ANSYS analysis results showed lower deflection on the blade using epoxy with an additional of 0.50 wt.% of MWCNTs-COOH at tip speed ratios of 2.1, 2.6, and 3.1.

Investigation of electrical properties of hybrid nanocomposites containing different fillers on pressure sensor applications under different loading

Conductive elastomeric nanocomposites (CEMs) were prepared in two stages to control the precision of pressure sensors. Carbon-based nanofillers such as multi-walled carbon nanotubes (MWCNT) or graphene (GR) were added to the rubber matrix. For Rubber/MWCNT composites, unfunctionalized (U-MWCNT) and –COOH functionalized MWCNT (F-MWCNT) fillers were synthesized. The properties of the CEMs and the synergistic improvements between the fillers and rubber matrix in composites were also investigated. SEM images show that F-MWCNT fillers were dispersed homogeneously in the composites and they interacted with rubber better than other carbon fillers. The piezoresistivity properties of the CEMs before and after compression were determined using the four-probe method by cyclic loading in 1 mm increments between 1.5 mm and 3.5 mm. F-MWCNT filled composites had higher strength than others when they were compressed by 2.5 mm. The F-MWCNT and GR filled nanocomposites possessed the best resistivity for pressure sensors when compressed at 2.5 mm (for F-MWCNT 1.1E + 08 Ω, GR 5.28E + 06 Ω). These nanocomposites are promising pressures sensors for air suspension systems.

Functionalization of multi-walled carbon nanotube and its effect on shape memory behavior of nanocomposite based on thermoplastic polyurethane/polyvinyl chloride/multi-walled carbon nanotube (TPU/PVC/MWCNT)

Nanocomposites based on thermoplastic polyurethane/polyvinyl chloride/multi-walled carbon nanotubes were prepared by a solution method and their shape memory properties were studied. The blend ratios were 70/30, 60/40, and 50/50 (w/w) of thermoplastic elastomer polyurethane/polyvinyl chloride. To improve the dispersion of multi-walled carbon nanotubes, at 0.5% and 1% (wt), in polymer matrices, three-step chemical modifications were performed, including oxidation, chlorination and grafting of poly (ɛ-caprolactone) diol. The occurrence of surface modifications in MWCNTs was monitored using Fourier transform infrared spectroscopy, elemental analysis, scanning electron microscopy and thermal gravimetric analysis techniques. SEM micrographs revealed a good dispersion of MWCNTs in the polymer matrix due to better matrix-filler interactions compared to filler–filler interactions. The results showed that the main indices of shape memory behavior (shape fixity and shape recovery) of nanocomposite samples were affected by the polymer blend ratio, nanoparticle concentration and surface modification. Increasing the content of polyvinyl chloride led to reduced shape fixity and shape recovery, which was attributed to the lack of rigid structural nature of polyvinyl chloride. The presence of nanoparticles contributed to enhanced shape fixity and weaker shape recovery. This can be explained by lower polymer chain mobility in the presence of multi-walled carbon nanotubes. The reduction in chain mobility in nanocomposites reinforced by surface-modified multi-walled carbon nanotubes was more significant due to higher distribution efficiency of nano-scale fillers in the polymer matrix.

Effect of nanodiamonds and multi‐walled carbon nanotubes in thermoset hybrid fillers system: Rheology, dynamic mechanical analysis, and thermal stability

AbstractRecently, the interfacial bonding between nanodiamonds (DNDs) and multi‐walled carbon nanotubes (MWCNTs) in epoxy‐based nanocomposites were found. In this work, effects of amino functionalization on MWCNTs and DNDs introduction on rheology, dynamic mechanical properties, and thermal stability of MWCNTs epoxy‐based nanocomposites are discussed. The results show that pristine MWCNTs increase the complex viscosity, lower the molecular weight of epoxy net chains as well as glass transition temperature (Tg), and expand the phase separation. Amino functionalization of MWCNTs make the behaviors above disappeared nearly. Besides, introduction DNDs improved Tg and restricted the phase separation as well, but the high complex viscosity and non‐Newtonian behavior remains. This work may provide inspirations for the further researches about hybrid fillers.

Isotropic Hedgehog-Shaped-TiO2/Functional-Multiwall-Carbon-Nanotube Micromotors with Phototactic Motility in Fuel-Free Environments.

Directional motion in response to specific signals is critically important for micro/nanomotors in precise cargo transport, obstacle avoidance, collective control, and complex maneuvers. In this work, a kind of isotropic light-driven micromotor that is made of hedgehog-shaped TiO2 and functional multiwall carbon nanotubes (Hs-TiO2@FCNTs) has been developed. The FCNTs are closely entangled with Hs-TiO2 and form a close-knit matrix on the surface of Hs-TiO2, which facilitates the transfer of electrons from Hs-TiO2 to FCNTs. Due to the high redox potential of Hs-TiO2, excellent electron-hole separation efficiency by the addition of FCNTs, and isotropic morphology of the micromotor, these Hs-TiO2@FCNT micromotors show phototactic and fuel-free propulsion under unidirectional irradiation of UV light. It is the first time to demonstrate isotropic micromotors that are propelled by self-electrophoresis. The isotropy of Hs-TiO2@FCNT micromotors makes them immune to the rotational Brownian diffusion and local flows, exhibiting superior directionality. The motion direction of our micromotors can be precisely tuned by light and a velocity of 8.9 μm/s is achieved under 160 mW/cm2 UV light illumination. Photodegradation of methylene blue and active transportation of polystyrene beads are demonstrated for a proof-of-concept application of our micromotors. The isotropic design of the Hs-TiO2@FCNT micromotors with enhanced photocatalytic properties unfolds a new paradigm for addressing the limitations of directionality control and chemical fuels in the current asymmetric light-driven micromotors.

Understanding the interaction in functionalized multi-walled carbon nanotube/polyaniline composite by impedance study at low temperature

The impedance, modulus spectroscopy and dielectric properties of polyaniline (PANI) and composite with multi-walled carbon nanotube (MWCNT) of different degrees of functionalization are studied from 300 to 4.2 K in the frequency range 40 Hz–5 MHz. At low temperature (T 100 K), grain and grain boundary relaxation peaks are observed in PANI. In composites, MWCNT forms a network between less and highly conducting grains, increases dc conductivity, and shows no relaxation peak at low temperature. The chemical functionalization of MWCNT increases the polar interaction between MWCNT and PANI, shifts the relaxation peaks towards lower frequency and slows the relaxation process. The relaxation process is manifested as non-Debye type and it tends towards Debye type with increasing temperature in functionalized muti-walled carbon nanotube (fMWCNT) PANI composites, and explained by Bergman’s theory. The relaxation barrier energy at the interface of fMWCNT and PANI increases with increasing degree of functionalization which is the effect of enhanced interfacial (Maxwell Wagner–Sillars) polarization. In MWCNT composite, the real part of dielectric constant shows high negative value below 10 K at lower frequency (950 Hz) and it becomes positive due to functionalization of MWCNT. An additional crossover from positive to negative occurs in both MWCNT and fMWCNT, PANI composite above temperature 60 K and frequency 500 Hz. This crossover shifts towards higher temperature and frequency with increasing degree of functionalization. The negative value and crossover of dielectric constant are explained by Drude–Sommerfeld model.

Effect of carbon nanotubes functionalization on properties of their nanocomposites with polycarbonate/poly(acrylonitrile‐butadiene‐styrene) matrix

AbstractIn this work, a comparative study evaluating the influence of different functionalization of carbon nanotubes on the properties of nanocomposites with polymeric matrix was performed. A 50/50 wt% polycarbonate (PC)/poly(acrylonitrile‐butadiene‐styrene) (ABS) blend was used as polymeric matrix of the nanocomposites. The comparison was made between nanocomposites reinforced with covalently functionalized multiwall carbon nanotubes (MWCNTf) and MWCNTf/nanoclay hybrid functionalization. The effect on the mechanical and morphological properties of the nanocomposites was evaluated through tensile and Izod impact tests and scanning electron microscopy and transmission electron microscopy (TEM) analyses. The thermal characterization of PC/ABS blends and nanocomposites was performed by differential scanning calorimetry (DSC). Results showed that both methods of functionalization of MWCNTs increased the stiffness and impact resistance of the nanocomposites. TEM micrographs indicated the preferred location of the reinforcements in the SAN phase of ABS. Results from DSC indicated an increase in the thermal resistance of the nanocomposites.

Surface functionalization of nylon 66 membrane using para-phenylenediamine and carboxylic functionalized multi-walled carbon nanotubes for removal of calcium ions from aqueous solution

Nylon 66, which is an important membrane class used in manufacturing of chitin and chitosan, have a number of features that can be improved by surface functionalizations into a novel composite structure with support of ultrasound and silica gel (SiG) catalyst in a doubled amidation reaction. Firstly, nylon 66/para-phenylenediamine thin film composite (NP-TFC) is prepared from commercial nylon 66 membrane in an ultrasound assisted hydrolysis-amidation reaction. Secondly, carboxylic functionalized multi-walled carbon nanotubes (MWCNT-COOH) are grafted on the NP fiber in an ultrasound assisted/SiG catalyzed amidation reaction, where para-phenylenediamine (pPD) role is cross-linking. As an excellent result confirmed by either Fourier transform infrared (FTIR), Raman spectrometry or scanning electron microscopic (SEM), bundled MWCNTs bridges are easily built in SiG catalyzed ethanol media to connect nylon 66 fibers at distances of 0.3 to 1 μm. The vacuum filtration test confirmed that as-prepared nylon 66/pPD/MWCNTs structure has superior Ca2+ rejection efficiency to that of original nylon 66.

Optimization of the adsorption of total organic carbon from produced water using functionalized multi-walled carbon nanotubes

This study investigated the removal of Total Organic Carbon (TOC) from produced water by batch adsorption process using adsorbents developed from Multi-Walled Carbon Nanotubes (MWCNTs). The MWCNTs, synthesized by catalytic chemical vapour deposition method using kaolin-supported tri-metallic (iron-cobalt-nickel) catalyst were purified by H2SO4/HNO3 and then functionalized with 1-pyrenebutanoic acid N-hydroxyl succinimidyl ester (PSE). The raw, purified and functionalized MWCNTs were characterized by High Resolution Scanning Electron Microscopy (HRSEM), High Resolution Transmission Electron Microscopy (HRTEM), Brunauer–Emmett-Teller (BET) and Fourier Transform Infrared Spectroscopy (FTIR). In the results, HRSEM/HRTEM revealed the structure, purity and also confirmed the attachment of the PSE molecule onto the nano-adsorbent(s). The BET surface areas of MWCNTs, PMWCNTs and FMWCNTs were 970.17, 869.25 and 831.80 m2/g, respectively while the FTIR established the existence of surface functional groups. The functionalized MWCNTs (FMWCNTs) nano-adsorbent showed superior performance efficiency (93.6%) than the purified MWCNTs (PMWCNTs) (79.2%) as examined under the same batch adsorption condition: 0.02 g adsorbent dosage, 10–90 min contact time and 30 °C solution temperature probably, due the improved wettability resulted from incorporation of PSE. Subsequently, Central Composite Design (CCD) was applied to optimize the process parameters for the sorption of TOC onto FMWCNTs. The CCD in the response surface methodology predicted 260 mg/g adsorption capacity of FMWCNTs in the removal of TOC at the optimum condition of 49.70 min contact time, 34.81 °C solution temperature, and 0.02 g adsorbent dosage. The kinetics data were best described by pseudo-second-order model and thermodynamic parameters suggested that the process was feasible, spontaneous and exothermic. It can be inferred from the various analysis conducted that the developed FMWCNTs nano-adsorbent is effective for removal of TOC from oil-produced water and may be explored for removal of organic contaminants from other industrial wastewater.

Carbon Nanotube Reinforced Natural Fibers for Biodegradable Nanocomposites

Natural fiber-reinforced nanocomposites (NFRCs) are proved as the best alternative for synthetic composites in view of cost and environmental effects. NFRCs have been produced from agro-waste such as banana tree fiber (BFs), because BF are strong, light-weight, and have smaller elongation. To improve the quality of BF, multiwall carbon nanotubes (MWCNTs) are used as reinforcing filler. MWCNTs are functionalized by an ecofriendly radio frequency oxygen plasma processing method. Cellulose nano-crystals (CNC) are extracted from BFs by double hydrolysis process and a simple dip-drying technique has been used to produce NFRCs. Field emission scanning electron micrographs and transmission electron microscopy conform the well functionalization of MWCNTs and also ensure homogeneous incorporation in the BF matrix. The composites continue thermally stable corresponding to BFs. Mechanical strength of the NFRCs are improved owing to the incorporation of MWCNTs. Functional groups in the BFs, CNC and NFRCs are investigated by Fourier transform infrared spectroscopy. The current density of the sample is increased 1000 times than the raw fibers and conductivity increases up to 17 Sm^-1, which increases with temperature under the applied voltage 100 V and shows the linier characterization. Therefore, these light-weight biodegradable NFRCs encourage its ability as cost effective industrial conductive composite as usable in electronic devices.

Features of oxidative functionalization of multiwalled carbon nanotubes

The paper studies the oxidation laws of multiwalled carbon nanotubes (MWCNTs) of various types, which differ in geometric parameters (diameter, length, specific surface), using nitric acid. In different experiments, the duration of oxidation, the concentration of nitric acid, and the consumption of HNO3 per 1 g of MWCNTs were varied. The qualitative composition of the formed oxygen-containing functional groups and the changes occurring with the graphene layers of nanotubes were established by the methods of IR and Raman spectroscopy, and transmission electron microscopy. The total oxygen content in the samples was determined by energy dispersive analysis. The degree of MWCNTs functionalization with acidic functional groups was determined by Boehm titration. An X-ray structural analysis of the obtained samples was carried out and their specific surface area was estimated. It was determined that the most serious changes in the functionalization degree occurred during the first 1–3 hours of oxidation. During this time interval, the achieved values of the functionalization degree were determined mainly by the shape of the MWCNTs graphene layers. At 7–10 hours of treatment, regardless of the initial parameters, MWCNTs have the functionalization degree in the range of 0.5–0.7 mmoLg–1. At the initial stage of oxidation, the amorphous phase is removed. Using dilute solutions of nitric acid does not allow obtaining oxidized nanotubes with the high functionalization degree. It is expedient to reduce the consumption of 65 % HNO3 to 40 mL per 1 g of MWCNTs.

Quantification of carboxyl-functionalized multiwall carbon nanotubes in plant tissues with programmed thermal analysis.

In this study, carboxyl functionalized multiwall carbon nanotubes (c-MWCNTs) in plant (lettuce [Lactuca sativa Bionda Ricciolina]) tissues were quantitatively analyzed with programmed thermal analysis coupled with a sequential digestion. Programmed thermal analysis evidenced a linear relationship between c-MWCNT-bound C and elemental C detected. A detection limit of 114-708μg C g-1 plant tissues (dry mass) was achieved for analysis of c-MWCNTs. The method was demonstrated using the tissues of lettuce cultured hydroponically for 3 wk with c-MWCNTs at an exposure of 10 and 20μg ml-1 . This quantitative analysis can be used to provide insights into carbon nanotube exposure through agricultural products and promote its sustainable application.

Functionalized multi walled carbon nanotubes supported copper-titania nanoparticles for oxidation of cinnamyl alcohol under mild reaction conditions

ObjectivesAlcohols oxidation is one of the important organic transformation in fine chemical industries. Prevailing processes are hazardous due to involvement of stoichiometric oxidants and homogeneous catalysts. In the present work, oxidation of cinnamyl alcohol was carried out using unconventional, affordable, and feasible heterogeneous catalysts. MethodCopper-titania (Cu-Ti) nanoparticles were prepared and supported on functionalized multi walled carbon nanotubes (F-CNTs). Various instrumental techniques such as X-ray Diffractometery (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) Analysis and Brunauer Emmett Teller (BET) surface area analyzer were used to characterize the synthesized catalysts. Both catalysts; Cu-Ti and Cu-Ti/F-CNTs were evaluated for their potencies in conversion of cinnamyl alcohol (CnOH) to cinnamaldehyde (CnHO). Different derivatives of CnOH (with attached electron withdrawing and donating groups) were also oxidized in presence of prepared catalysts to determine the substituents effect and get maximum yield. The prepared catalyst was used five times to determine its reuseablity. ResultsThe presence of copper and titania in the synthesized catalyst structure was confirmed through XRD and EDX analysis. The agglomeration level was confirmed from SEM analysis. Little reduction in surface area on parental carbon nanotubes was observed due to deposited metals. Appreciable yield of CnHO were obtained at the optimal reaction conditions: temperature = 70 °C, catalyst amount = 0.1 g, pO2 = 760 Torr, substrate solution concentration and volume = 1 mmol CnOH/10 mL ethanol, stirring speed = 900 rpm, and time interval = 60 min. The conversion rate was improved to 100% through attachment of electron donating groups at ortho and para position of parental compound benzene ring. No appreciable decrease in activity of catalyst were observed after 4th cycle. ConclusionCu-Ti/F-CNTs showed excellent catalytic activity, selectivity, true heterogeneous nature, low cost, and recyclability, hence it could be used as a potent catalyst for CnOH to CnHO conversion.

Polycarbazole-multiwalled carbon nanotubes based nanocomposite: Synthesis, spectral, biocidal and Acetaldehyde sensing studies

We herein report the functionalization of multi-walled carbon nanotubes (MWCNT) via oxidation method using a concoction of concentrated H2SO4 and HNO3. The electrically conducting polycarbazole-multiwalled carbon nanotubes nanocomposite (PCz/MWCNT) has been prepared by in-situ oxidation polymerization of monomer of carbazole (Cz). Several spectral techniques like FTIR, SEM/EDS, TEM, XRD and TGA were used to characterize PCz/MWCNTs nanocomposite. The spectroscopic data ascertains a strong interaction between PCz and MWCNTs. The nanocomposite exhibits high thermal stability as compared to the pristine PCz. The nanocomposite demonstrated better electrical conductivity and isothermal stability with respect to DC electrical conductivity retention under normal conditions below 100°C. The PCz/MWCNT based sensor was designed for the detection of acetaldehyde. It was observed that the resistivity of the PCz/MWCNT enhances on exposure to acetaldehyde at 25°C, and showed a direct relationship between the response and concentration of acetaldehyde. Moreover, PCz and PCz/MWCNT were also tested for their plausible biocidal activity.

Functionalisation of MWCNTs with piperazine and dopamine derivatives and their potential antibacterial activity

Functionalised multi-walled carbon nanotubes (MWCNTs) are exclusively used in antibacterial activity due to their high aspect ratio and surface penetration characteristics. This study reports the synthesis of piperazine and dopamine functionalised MWCNTs to investigate antibacterial activity against strains like Staphylococcus aureus and Micrococcus luteus. MWCNTs were activated through acid oxidation and then refluxed at 75°C for 10 and 8 h in the presence of piperazine and dopamine, respectively. The functionalised MWCNTs were characterised by scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction and Raman spectroscopy. Moreover, functionalised MWCNTs were subjected to zone inhibition assay on agar plates. Results revealed the significant antibacterial activity against various bacteria up to 50%. Similarly, it was observed that the effect of different solvents, such as dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO) was non-prevalent to the bacterial zone of inhibition. Such facile nano-modifications provide passage to nano-antibacterials for advanced studies.

Enhancement of functionalized carbon nanotubes gas sensor by adding metal oxide nanoparticles

Functionalized-multi wall carbon nanotubes (F-MWCNTs) and functionalized-single wall carbon nanotubes (F-SWCNTs) were well enhanced using CoO Nanoparticles. The sensor device consisted of a film of sensitive material (F-MWCNTs/CoONPs) and (F-SWCNTs/CoO NPs) deposited by drop- casting on an n-type porous silicon substrate. The two sensors perform high sensitivity to NO2 gas at room temperatures. The analysis indicated that the (F-MWCNTs/CoONPs) have a better performance than (F-SWCNTs/CoONPs). The F-SWCNTs/CoONPs gas sensor shows high sensitivity (19.1 %) at RT with response time 17 sec, while F-MWCNTs/CoONPs gas sensor show better sensitivity (39 %) at RT with response time 13 sec. The device shows a very reproducible sensor performance, with high repeatability, complete recovery, and adequate response. A demonstration of the improvement in sensing of NO2 gas using CoO-functionalized nanotubes is provided.