Aggregation Of Multi-walled Carbon Nanotubes Research Articles

Heterogenization of Ionic Liquid on Multiwalled Carbon Nanotubes for Lead(II) Ion Detection.

The presence of lead(II) ion poses a significant threat to water systems due to their toxicity and potential health hazards. The detection of Pb2+ ions in contaminated water is very crucial. The ionic liquid functionalized multiwalled carbon nanotubes (IL@MWCNT) nanocomposite was fabricated using ionic liquid (IL) 1-methyl-3-(4-sulfobutyl)-imidazolium chloride and multiwalled carbon nanotubes (MWCNTs) for detection of lead(II) ions. It is a novel method to heterogenize the layer of IL on the surface of MWCNTs. The XPS and FTIR analyses confirm that the ionic liquid is not decomposed during annealing process. Moreover, the XRD analysis shows the presence of MWCNTs and carbon quantum dots (CQDs). The HRTEM results exhibit the aggregation of MWCNTs with IL, and formation of small distorted round shaped flakes of CQDs. Further, the successful heterogenization of IL on the surface of MWCNTs is also confirmed by TGA-DSC analysis. The quenching phenomenon of nanocomposite was observed by UV-Visible spectroscopy. The nanocomposite exhibits high performance for the selective detection of lead(II) ions in comparison to other metal ions. The presence of lead(II) ions eventually reduced the intensity of absorption. A limit of detection (LOD) of 9.16 nM was attained for Pb2+ ions in a concentration range of 0-20 nM.

The impact of synergistic action of methacrylic acid/zinc oxide/carbon nanotubes on metal Friction and wear

The continuous operation of essential refining equipment, internal mixers, leads to wear on their end faces, resulting in an increased gap between the mixer chamber and the end face. This, in turn, causes material leakage, reducing mixing efficiency and adversely impacting rubber performance. Therefore, investigating metal wear on the mixer's end face during the mixing process is essential. Scholars have introduced dynamic covalent bonds into rubber molecular chains, bestowing self-repairing capabilities upon the materials. This innovation has significant implications for extending rubber lifespan and lowering production costs. It involves adding methacrylic acid (MAA) and excess zinc oxide (ZnO) to construct an ionic crosslinking network, limiting covalent crosslinking of rubber molecules and enabling in-situ polymerization of MAA/ZnO, resulting in self-repairing properties. However, it is crucial to consider corrosive wear induced by MAA's strong acidity on metals. This study combines MAA, ZnO, and multi-walled carbon nanotubes (MWCNTs) through mechanical mixing to create a composite material called zinc methacrylate (ZDMA)/MWCNTs/rubber. The research investigates the in-situ synthesis mechanism of MAA and ZnO and the synergistic mechanism of ZDMA and MWCNTs. The study analyzes the impact of MWCNTs additive amount on the frictional wear of the internal mixer's metal end face. During the mixing process, ZDMA is grafted and polymerized onto rubber's macromolecular chains, forming ionic pairs with strong electrostatic interactions, creating a primarily reversible supramolecular network dominated by ion crosslinking. This ion crosslinking network, along with the three-dimensional mesh structure of MWCNTs, establishes a stable spatial structure within the rubber matrix. The study reveals that increasing the MWCNTs content to 3 phr reduces the aggregation of SiO2 particles and ZDMA granules within the rubber matrix, resulting in reduced friction coefficients, roughness, and wear rates of the metal. However, exceeding 3 phr of MAA content leads to excessive MWCNT aggregation within the rubber matrix, increasing wear rates, roughness, and friction coefficients due to hindrance of rubber macromolecular chain crosslinking and reduced SiO2 particle dispersion within the rubber matrix. These findings provide valuable insights into the dynamics of frictional wear in internal mixers.

Effect of Cellulose Material-Based Additives on Dispersibility of Carbon Nanotubes

In nanoscience, nanotechnology is applied to various technologies, and research is actively being conducted. As the application of multi-walled carbon nanotubes (MWCNTs) in various fields increases, efforts have been made to develop dispersion and functionalization technologies. In order to effectively use MWCNT nanofluids, it is most important to solve the problem of dispersion. In this study, MWCNTs were improved in dispersibility and functionalized through various chemical and mechanical treatments. In addition, MWCNTs aggregation was alleviated by using cellulose nanocrystal (CNC) as a dispersant. The processing results of MWCNTs and CNC were analyzed through transmission electron microscopy (TEM) and the dispersion was characterized by UV–Vis spectroscopy. The addition of CNC to MWCNTs has been confirmed to have high dispersibility and improved stability compared to untreated MWCNTs, and this effect affects the quality of the machine.

Effect of X-ray exposure on nano-mechanical properties of multi-walled carbon nanotube incorporated silicone polymer nanocomposites: An AFM-based study

Nano-mechanical properties of silicone polymer-based nanocomposites loaded with multi-walled carbon nanotube (MWCNT) as nanofillers are probed here using the atomic force microscopy (AFM) technique. Further, the effects of MWCNT concentration and X-ray exposure on the nano-mechanical and topographic properties of the polymer nanocomposites are systematically studied. The root mean square surface roughness is found to increase by ∼123% when the neat polymer matrix is loaded with 2.5 wt.% of MWCNT, whereas, for a fixed MWCNT concentration, the surface roughness is found to increase by ∼171% after X-ray irradiation. This is attributed to the X-ray induced polymer degradation, polymer pull-out and poor filler-matrix interaction leading to the aggregation of MWCNT. Adhesion force and adhesion energy are estimated from the AFM-based force-displacement curves. Both quantities are found to increase with MWCNT concentration. After an exposure to diagnostic X-rays (30–70 keV), the adhesion force is found to increase by ∼4 times, which is attributed to the increased tip-surface contact area due to the higher surface roughness of the X-ray exposed samples. Further, the variation of adhesion energy with filler concentration is found to be in agreement with the theoretical values obtained from the Johnson, Kendall and Roberts (JKR) model. The elastic modulus is found to increase with the filler concentration due to an increase in adhesion force. The obtained results are beneficial for the optimal design of nanofiller loaded polymer nanocomposites for various applications, including the fabrication of lead-free radio-opaque nanocomposites.

Static and dynamic moduli of elasticity and drying shrinkage behavior of concrete containing multi-walled carbon nanotubes

This paper investigated the efficiency of concrete reinforced with multi-walled carbon nanotubes (MWCNTs) specimens in terms of fresh concrete slump, compressive strength, static and dynamic moduli of elasticity, the drying shrinkage strain, and microstructure. In addition, the particle sizes distribution of MWCNTs dispersions in water was investigated by the dynamic light scattering (DLS) test. The dispersion sonicated with an ultrasonic probe had a smaller distribution range with a higher rate in smaller particle sizes compared with the dispersion sonicated with an ultrasonic bath. By incorporation of MWCNTs with an amount of 0.05–0.2% of cement weight, the fresh concrete workability, and the 365 day-age drying shrinkage strain are reduced up to 20% and 24%, respectively; also, the compressive strength, the static modulus of elasticity, and the dynamic modulus of elasticity increased up to 35.4%, 8.9%, and 5%, respectively. The SEM studies showed the bridging behavior of MWCNTs in the cement paste matrix at the nanoscale, and map analysis showed the distribution and the aggregation of MWCNTs in some parts of the concrete mixture.

Electrical, mechanical, and optical changes in MWCNT-doped PMMA composite films

In this study, we report the preparation of poly (methyl methacrylate)/multi-walled carbon nanotube (MWCNT) composite thin films by simple and efficient solution mixing and ultrasonic method and the electrical, optical, and mechanical characterizations. Scattered light intensity ( I sc), tensile modulus ( E), and surface conductivity ( σ) of these composites have increased with the addition of MWCNT into the composite. The observed behavior in electrical, optical, and mechanical properties of the poly (methyl methacrylate)/MWCNT composites was interpreted by site and classical percolation theory. The optical mechanical and electrical percolation thresholds of poly (methyl methacrylate)/MWCNT composites were determined as φ op = 3 wt%, φ m = 0 wt%, and φσ = 5 wt%, respectively. The optical ( t op), mechanical ( t m), and electrical ( t σ) critical exponents were calculated as 2.23, 0.43, and 0.11, respectively. Both the tensile modulus and tensile strength of poly (methyl methacrylate)/MWCNT composites were increased with increasing MWCNT content until it reaches to 10 wt%. However, above φ = 10 wt%, the mechanical properties of the composites were decreased due to the aggregation of MWCNTs, while the toughness does not show a significant change until φ = 10 wt% MWCNT content, whereas it was decreased above this value.

Improvement of electrical conductivity of PEMA film by incorporating EMITFSI and carbon based nanofiller

Abstract The electrical conductivity of dual inclusion of 1-ethyl-3-methyl imidazolium bis(trifluorosulfonyl) imide ionic liquid and three allotropes of carbon based nanofillers (multiwalled carbon nanotube, graphene and graphite) in poly (ethyl methacrylate) films with thickness ranging from 100 to 250 μm has been investigated in the temperature range of 300–380 K. It is found that the electrical conductivity of film with 0.5 wt % multiwalled carbon nanotube has the highest ambient electrical conductivity of 4.9 × 10−6 Scm−1 which is five order of magnitude higher than pure poly (ethyl methacrylate) film. Moreover, the stability of the highest electrical conductivity is also found to be significantly improved for a longer period. From the investigated physicochemical properties, these improvements are likely can be explained by the aggregation of multiwalled carbon nanotubes, the increase in electronic transport and the reduction in glass transition temperature which likely effect its ionic mobility. Consequently, these enhancements may lead to a promising improvement of its electrical properties for a stable near room temperature application.

Modification of MWNTs by the combination of Li-TFSI and MAPP: Novel strategy to high performance PP/MWNTs nanocomposites

Polypropylene (PP)/multi-walled carbon nanotubes (MWNTs) nanocomposites with excellent toughness and ductility pose significant challenges because of the severe aggregation of MWNTs in non-polar PP matrix due to the incompatibility. In this work, lithium bis(trifloromethanesulfonyl) imide (Li-TFSI) and maleic anhydride grafted polypropylene (MAPP) have been simultaneously introduced to modify MWNTs for the homogenous dispersion in PP matrix. The surface of MWNTs has strong “π-cation” interactions with the Li+ ions of Li-TFSI. At the same time, Li-TFSI can promote the ring-opening of the maleic anhydride and form coordination with the newly formed carboxylate. Therefore, the combination of Li-TFSI/MAPP enhanced the compatibility between PP and MWNTs. The Li-TFSI/MAPP modified MWNTs can be dispersed uniformly in the polypropylene. The elongation at break and the toughness of the nanocomposites with the 3 wt % modified MWNTs are 800% and 26 kJ/m2, respectively. The values are significantly higher than those of the samples (200% and 22 kJ/m2) at the same MWNTs loading. The strategy paves new possibility to fabricate high performance PP nanocomposites.

Dispersion, sedimentation and aggregation of multi-walled carbon nanotubes as affected by single and binary mixed surfactants.

Two commonly used dispersants, octyl phenol ethoxylate (Triton X-100) and sodium dodecyl sulfate (SDS), were employed to explore the effects of single or mixed surfactants on the dispersion, sedimentation and aggregation of multi-walled carbon nanotubes (MWCNTs). Non-ionic surfactant TX100 showed much superior capability to anionic surfactant SDS in dispersing MWCNTs due to the benzene ring structure in its tail group. The addition of SDS reduced the adsorption of TX100 on the surface of MWCNTs and the consequent suspension of MWCNTs. The dispersing ability of TX100–SDS binary mixture was between those of individual SDS and TX100. The introduction of SDS greatly retarded the sedimentation and aggregation of suspended MWCNTs. The critical coagulation concentration (CCC) values of suspended MWCNTs dispersed by TX100 (2000 mg l−1), SDS (2000 mg l−1) and TX100–SDS (2000 mg l−1 of each component) were 48.6, 398 and 324 mM, respectively, for Na+ treatments. The CCC values were much lower for Ca2+ treatments, which were 30.4 and 32.1 mM, respectively, for MWCNTs dispersed by TX100 and TX100–SDS mixture. Overall, these results demonstrated that although the introduction of SDS did not improve the ability of TX100 in suspending MWCNTs, the suspensions exhibited more stable properties than those dispersed by TX100 alone. Our findings have important implications for the design of surfactant mixtures and the prediction of the behaviour and fate of MWCNTs in the water environment.

Effect of Multi-walled Carbon Nanotubes on the Toxicity of Triphenyltin to the Marine Copepod Tigriopus japonicus.

Marine organisms are often exposed to a mixture of various pollutants in marine environment (i.e., nanoparticles, organic pollutants). The present study investigated the potential effects of multi-walled carbon nanotubes (MWCNTs) on the toxicity of triphenyltin chloride (TPTCl). The results revealed an antagonistic interaction between MWCNTs and TPTCl on the copepod through 96h acute exposure, which was attributed to the adsorption of TPTCl to MWCNTs and aggregation of MWCNTs in the test solutions. Results of 21days' chronic exposure showed that the effect concentration of MWCNTs could be 100 times lower than that of acute exposure. The exposure to binary mixture of MWCNT (1.0mg/L) and TPTCl (0.3µg/L) caused a reduction by 94% for the 3rd time spawning and 83% for the total number of hatched nauplii. The ingestion and exterior attachment of MWCNTs to the copepod might be the main reasons causing the adverse effect in reproduction.

Flexible Carbon Nanotube-Based Polymer Electrode for Long-Term Electrocardiographic Recording.

The long-term monitoring of electrocardiogram (ECG) is critical for the accurate diagnosis and tracking of cardiovascular diseases (CVDs). However, the commercial Ag/AgCl electrode is not suitable for long-term monitoring due to skin allergies and signal degradation, caused by the conductive gel drying over time. In this paper, a flexible gel-free electrode, composed of a multi-wall carbon nanotube (MWCNT) and polydimethylsiloxane (PDMS), is proposed for long-term wearable ECG monitoring. To achieve uniform dispersion of MWCNTs in viscous PDMS, we developed a novel parallel solvent-assisted ultrasonic dispersion method, wherein the organic solvent n–Hexane served as a dispersion to avoid MWCNT aggregates. The properties of the MWCNT/PDMS electrode were assessed through structural characterization, contact impedance tests, ECG measurements, and biocompatibility tests. When the MWCNT weight fraction reached 5.5 wt%, the skin-electrode contact impedance of the MWCNT/PDMS electrode was lower than that of the Ag/AgCl electrode below 100 Hz. In daily ECG monitoring, the MWCNT/PDMS electrodes showed superior performance against motion artifact compared to the Ag/AgCl electrode. After seven days of wearing the MWCNT/PDMS electrode, ECG signals did not degrade and no side effects, such as skin redness and swelling, were observed. Thus, this electrode could enable long-term ECG monitoring in wearable healthcare systems.

Polyurethane hybrid membranes with confined mass transfer channels: The effect of functionalized multi-walled carbon nanotubes on permeation properties

Aiming to prepare pervaporation membranes with confined mass transfer channels, multi-walled carbon nanotubes (MWCNTs) with and without functionalization were incorporated into polyurethane (PU) polymer matrices. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD), Fourier-transform infrared (FTIR), and Raman spectroscopy were employed to explore the effect of functionalization on the morphologies of MWCNTs. The changes in the morphologies of the resulting PU hybrid membrane were then characterized by SEM, TEM, and XRD. Swelling-sorption and pervaporation experiments of benzene and cyclohexane were employed to evaluate the separation performances of various hybrid membranes. The results showed that the introduction of many oxygenated functional groups onto the MWCNT surfaces through functionalization not only efficiently inhibited the MWCNT aggregation but also improved the distributions of the MWCNTs in solvents and polymer materials. Due to the 1D tube structures of the MWCNTs with conjugated π bonds, the addition of well-distributed MWCNTs into the hybrid membranes not only increased the benzene sorption abilities of the membranes but also enhanced the benzene diffusion selectivities due to the strong driving force for the molecules in the confined mass transfer channels. A higher content of well-distributed MWCNTs in the membrane yielded a higher separation performance for benzene. Additionally, increasing the operating temperature in the pervaporation experiments accelerated the molecular motion and weakened the affinity between the benzene molecules and the walls of the MWCNTs, increasing the permeation fluxes of the membranes while decreasing the benzene separation factors.

Designing an advanced electrode of mixed carbon materials layered on polypyrrole/reduced graphene oxide for high specific energy supercapacitor

A free-standing and flexible film is fabricated by layering multiwalled carbon nanotube/reduced graphene oxide/nanocrystalline cellulose composite on polypyrrole/reduced graphene oxide composite layer. The bilayer composite film is prepared by in-situ polymerization through a vacuum filtration method followed by a chemical reduction in the presence of hydrazine vapor and used as an electrode material for supercapacitor. The aggregation of multiwalled carbon nanotube and graphene oxide in the composite are addressed effectively by the support of nanocrystalline cellulose that favors ions movements in the composite. The symmetrical supercapacitor device developed in this study combines the features of pseudocapacitor and electrical double layer capacitor and delivers outstanding supercapacitive properties. As manifested by the electrochemical results, the device exhibits a high specific capacitance of 882.2 F g−1, remarkable cycling stability of ∼90% over 10,000 cycles, and high specific energy of 44.6 Wh kg−1 with a high specific power of 2889.9 W kg−1, which outperformed many other reported polypyrrole-based materials for supercapacitors. This makes the bilayer a promising candidate for future high performance energy storage devices.

The influence of Climate Change on the fate and behavior of different carbon nanotubes materials and implication to estuarine invertebrates

The widespread use of Carbon nanotubes (CNTs) has been increasing exponentially, leading to a significant potential release into the environment. Nevertheless, the toxic effects of CNTs in natural aquatic systems are related to their ability to interact with abiotic compounds. Considering that salinity variations are one of the main challenges in the environment and thus may influence the behavior and toxicity of CNTs, a laboratory experiment was performed exposing the tube-building polychaete Diopatra neapolitana (Delle Chiaje 1841) for 28 days to pristine multi-walled carbon nanotube (MWCNTs) and carboxylated MWCNTs, maintained at control salinity 28 and low salinity 21. An innovative approach based on thermogravimetric analysis (TGA) was adopted for the first time to assess the presence of MWCNTs aggregates in the organisms. Both CNTs generated toxic impacts in terms of regenerative capacity, energy reserves and metabolic capacity as well as oxidative and neuro status, however greater toxic impacts were observed in polychaetes exposed to carboxylated MWCNTs. Moreover, both CNTs maintained under control salinity (28) generated higher toxic impacts in the polychaetes compared to individuals maintained under low salinity (21), indicating that exposed polychaetes tend to be more sensitive to the alteration induced by salinity variations on the chemical behavior of both MWCNTs in comparison to salt stress.

Optimization of Carbon Nanotube Dispersions in Water Using Response Surface Methodology.

The aim of this work was to demonstrate an optimization methodology to reliably obtain stable macrodispersions (i.e., for ≥24 h) of carbon nanotubes in water using sonication. Response surface methodology (RSM) was utilized to assess and optimize the sonication parameters for the process. The studied input parameters were (i) sonication time (duration), (ii) amplitude (of vibration), and (iii) pulse-on/off (duration) of the sonicator. The analyzed responses were mean diameter and size distribution of multiwalled carbon nanotube (MWNT) aggregates in water, which were measured by the dynamic light scattering technique. A semiempirical model was developed and statistically tested to estimate the magnitude of sonicator parameters required to obtain specified MWNT macrodispersions (i.e., aggregates’ mean diameter and distribution) in water. The results showed that MWNT aggregates of 2 ± 0.5 μm can be obtained by optimizing sonicator parameters to a sonication time of 89 s, amplitude of 144 μm, and pulse-on/off cycle of 44/30 s. These process settings for 100 mg/L MWNTs in a 30 mL aliquot of deionized water would consume 863 J/mL of sonication energy. Contrary to the popular belief, “sonication time” and/or “sonication energy input” were not found to be proportional to the degree of dispersion of MWNTs in water. This might be the reason for the frequent disparity and nonreproducibility of sonication results reported in scientific literature, especially for dispersing nanomaterials in a number of different systems. The amplitude of vibration was noted to be the most sensitive parameter affecting MWNT aggregates’ diameter and distribution in water. The characterization of MWNTs was performed using electron microscopy, surface area analyzer, thermogravimetric analyzer, and zeta potential analyzer. This study can be helpful in evaluating sonication dispersion of particulate matter in other incompressible fluids such as graphene dispersion in organic solvents.

Gold nanorods decorated with graphene oxide and multi-walled carbon nanotubes for trace level voltammetric determination of ascorbic acid.

An ultra-sensitive sensor is described for the voltammetric determination of ascorbic acid (AA). A glassy carbon electrode (GCE) was modified with graphene oxide (GO), multi-walled carbon nanotubes (MWCNTs) and gold nanorods (AuNRs). GO was used to prevent the aggregation of MWCNTs. The integration of positively charged AuNRs reduces the overpotential and increases the peak current of AA oxidation. Figures of merit of this sensor, typically operated at a low working potential of 0.036V (vs. Ag/AgCl), include a low detection limit (0.85nM), high sensitivity (7.61μA·μM-1·cm-2) and two wide linear ranges (from 1nM to 0.5μM and from 1μM to 8mM). The use of GO simplifies the manufacture and results in a highly reproducible and stable sensor. It was applied to the quantification of AA in spiked serum. Graphical abstract Graphical abstract contains poor quality and small text inside the artwork. Please do not re-use the file that we have rejected or attempt to increase its resolution and re-save. It is originally poor, therefore, increasing the resolution will not solve the quality problem. We suggest that you provide us the original format. We prefer replacement figures containing vector/editable objects rather than embedded images. Preferred file formats are eps, ai, tiff and pdf.We have provided the original format with the attachments named g.tif. Graphene oxide (GO) in combination with multiwalled carbon nanotubes (MWCNTs) and gold nanorods (AuNRs) were used to constructa sensing interface with outstanding electrocatalytic performance for ascorbic acid detection.

Cell Attachment and Spreading on Carbon Nanotubes Is Facilitated by Integrin Binding.

Owing to their exceptional physical, chemical, and mechanical properties, carbon nanotubes (CNTs) have been extensively studied for their effect on cellular behaviors. However, little is known about the process by which cells attach and spread on CNTs and the process for cell attachment and spreading on individual single-walled CNTs has not been studied. Cell adhesion and spreading is essential for cell communication and regulation and the mechanical interaction between cells and the underlying substrate can influence and control cell behavior and function. A limited number of studies have described different adhesion mechanisms, such as cellular process entanglements with multi-walled CNT aggregates or adhesion due to adsorption of serum proteins onto the nanotubes. Here, we hypothesized that cell attachment and spreading to both individual single-walled CNTs and multi-walled CNT aggregates is governed by the same mechanism. Specifically, we suggest that cell attachment and spreading on nanotubes is integrin-dependent and is facilitated by the adsorption of serum and cell-secreted adhesive proteins to the nanotubes.

Debundling, Dispersion, and Stability of Multiwalled Carbon Nanotubes Driven by Molecularly Designed Electron Acceptors.

Carbon nanotubes (CNTs) have attracted significant attention because of their outstanding physical and chemical properties, and yet, their high natural tendency to form bundles, ropes, or aggregates, as a consequence of their strong π-π interactions, limits their solvent processing and further applications. Efficient processing solvents, mostly amide-based, that partially compensate for these strong inter-CNT π-π interactions have been widely reported. However, the yield of debundled/dispersed CNTs and the stability of subsequent dispersions in these solvents remain key challenges. Moreover, there are major concerns related to the large-scale use of conventional solvents, as they are fossil fuel based and intrinsically highly toxic, hence the need to identify environmentally friendly and safer alternatives. Herein, we address these challenges by using a ternary system composed of multiwalled CNTs (MWCNTs), tailored electron-deficient acceptors, and an organic solvent. Not only do the electron-deficient acceptors interrupt the inter-CNTs π-π interactions, thereby enabling the subsequent debundling and dispersion of MWCNTs aggregates in the solvent, they also act as stabilizers, after dispersion, by inhibiting inter-CNT π-π interactions and re-agglomeration. The use of electron acceptors increases the yield by a factor of 165 in N-methyl 2-pyrrolidone, improves the long-term stability of the debundled and dispersed MWCNTs, and reduces the energy input to only 30 min of mild bath sonication, compared with prolonged high-energy sonication reported in the literature. We also report for the first time, the use in MWCNT processing of a "green" biosolvent, dihydrolevoglucosenone, as an environmentally friendly and nontoxic alternative to the more conventional amide-based solvents.

Dispersion and stability study of carbon nanotubes in pH and temperature responsive polymeric matrix: Experiment and dispersion-corrected DFT study

We report the temperature and pH responsive dispersion of multi-walled carbon nanotubes (MWNTs) in poly(N-isopropylacrylamide) (PNIPAM) and poly-l-lysine hydrobromide (PLL) based polymeric matrix. An excellent dispersion of MWNTs in PNIPAM was observed below its lower critical solution temperature (LCST; 32 °C), however, aggregation of MWNTs observed above this critical temperature. The pH effect on MWNTs dispersion was also analysed, where at room temperature PLL/PNIPAM mixture demonstrates an excellent dispersion of MWNTs at pH 7 and 10, whereas, an agglomeration was observed at pH 4. PLL transforms from ionized coil to α-helix conformation with increase in pH (more globular shape), thus the solution demonstrates agglomeration of MWNT at low pH and well dispersed MWNTs at high pH. Density functional theory based analysis was also carried out to concurrent changes in the interfacial morphology, where PNIPAM shows better interaction with CNT than PLL including a higher strength of interaction. This can be attributed to the geometry curvature of PNIPAM that enables strong van der Waals interaction with the CNT surface, thus, PNIPAM may serve as a better dispersion agent than PLL. The quick responsive nature of PNIPAM and PLL shows notable changes with variation in temperature and pH, thus may be helpful to fabricate CNT based smart devices.

The influence of salinity on the effects of Multi-walled carbon nanotubes on polychaetes

Salinity shifts in estuarine and coastal areas are becoming a topic of concern and are one of the main factors influencing nanoparticles behaviour in the environment. For this reason, the impacts of multi-walled carbon nanotubes (MWCNTs) under different seawater salinity conditions were evaluated on the common ragworm Hediste diversicolor, a polychaete species widely used as bioindicator of estuarine environmental quality. An innovative method to assess the presence of MWCNT aggregates in the sediments was used for the first time. Biomarkers approach was used to evaluate the metabolic capacity, oxidative status and neurotoxicity of polychaetes after long-term exposure. The results revealed an alteration of energy-related responses in contaminated polychaetes under both salinity conditions, resulting in an increase of metabolism and expenditure of their energy reserves (lower glycogen and protein contents). Moreover, a concentration-dependent toxicity (higher lipid peroxidation, lower ratio between reduced and oxidized glutathione and activation of antioxidant defences and biotransformation mechanisms) was observed in H. diversicolor, especially when exposed to low salinity. Additionally, neurotoxicity was observed by inhibition of Cholinesterases activity in organisms exposed to MWCNTs at both salinities.