Functionalization of Carbon Nanotubes with Polystyrene

Polystyrene-modified carbon nanotubes: Promising carriers in targeted drug delivery

To design drug-delivery agents for therapeutic and diagnostic applications, understanding the mechanisms by which covalently functionalized carbon nanotubes penetrate and interact with cell membranes is of great importance. Here, we report all-atom molecular dynamics results from polystyrene and carboxyl-terminated polystyrene-modified carbon nanotubes and show their translocation behavior across a model lipid bilayer together with their potential to deliver a molecule of the drug ibuprofen into the cell. Our results indicate that functionalized carbon nanotubes are internalized by the membrane in hundreds of nanoseconds and that drug loading increases the internalization speed further. Both loaded and unloaded tubes cross the closest leaflet of the bilayer by nonendocytic pathways, and for the times studied, the drug molecule remains trapped inside the pristine tube while remaining attached at the end of polystyrene-modified tube. On the other hand, carboxyl-terminated polystyrene functionalization allows the drug to be completely released into the lower leaflet of the bilayer without imposing damage to the membrane. This study shows that polystyrene functionalization is a promising alternative and facilitates drug delivery as a benchmark case.

Improving the air quality with Functionalized Carbon Nanotubes: Sensing and remediation applications in the real world

With the world developing exponentially every day, the collateral damage to air is incessant. There are many methods to purify the air but using carbon nanotubes (CNTs) as adsorbents remains one of the most efficient and reliable methods, due to their high maximum adsorption capacity which renders them extremely useful for removing pollutants from the air. The different types of CNTs, their synthesis, functionalization, purification, functioning, and advantages over conventional filters are deliberated along with diverse types of CNTs like single-walled (SWCNTs), multiwalled (MWCNTs), and others, which can be functionalized and deployed for the removal of harmful gases like oxides of nitrogen and sulphur, and ozone, and volatile organic compounds (VOCs), among others. A comprehensive description of CNTs is provided in this overview with illustrative examples from the past five years. The fabrication methods and target gases of many CNTs-based gas sensors are highlighted, in addition to the comparison of their properties, mainly sensitivity. The effect of functionalization on sensors has been discussed in detail for various composites targeting specific gases, including the future outlook of functionalized CNTs in assorted practical applications.

Dispersion of Multi-Walled Carbon Nanotubes into White Cement Mortars: The Effect of Concentration and Surfactants

Multi-wall carbon nanotubes (MWCNTs) exhibit exceptional mechanical and electrical properties and can be used to improve the mechanical and piezoelectric properties of cement-based materials. In the present study, the effect of different MWCNT concentrations as well as different types of surfactants and a superplasticizer were examined to reinforce, at the nanoscale, a white cement mortar typically used for the restoration of monuments of cultural heritage. It was shown that sodium dodecylbenzenesulfonate (SDBS) and Triton X-100 surfactants slightly decreased the white cement mortars’ electrical resistivity (by an average of 10%), however, the mechanical properties were essentially decreased by an average of 60%. The most suitable dispersion agent for the MWCNTs proved to be the superplasticizer Ceresit CC198, and its optimal concentration was investigated for different MWCNT concentrations. Carboxylation of the MWCNT surface with nitric acid did not improve the mechanical performance of the white cement nanocomposites. The parametric experimental study showed that the optimum combination of 0.8 wt% of cement superplasticizer and 0.2 wt% of cement MWCNTs resulted in a 60% decrease in the electrical resistivity; additionally, the flexural and compressive strengths were both increased by approximately 25% and 10%, respectively.

Carbon nanotube materials for electrocardiography

Carbon nanotubes (CNTs) as 1D nanomaterials of excellent physicochemical characteristics bring hope to compete and eventually conquer traditional solutions in electrocardiography - one of the most powerful and non-invasive diagnostic tools in cardiac disorders. Our review tracks (from 2008) the development of CNTs as critical components in the systems where CNTs serve mainly as electroconductive fillers hence enable recording electrocardiographs (ECG). The characteristics of the CNT-based ECG systems - mainly to-skin electrodes and in a few cases wiring - covers their electrical and mechanical performance (adhesivity, flexibility, elasticity) and qualitative biocompatibility. By comprehensive analysis of the state-of-art in this field, we intend to indicate the most important challenges for the CNT (and other) materials to be applied in scale-up solution for electrocardiography in the near future.

Processing Methods Used in the Fabrication of Macrostructures Containing 1D Carbon Nanomaterials for Catalysis

A large number of methodologies for fabrication of 1D carbon nanomaterials have been developed in the past few years and are extensively described in the literature. However, for many applications, and in particular in catalysis, a translation of the materials to a macro-structured form is often required towards their use in practical operation conditions. This review intends to describe the available methods currently used for fabrication of such macro-structures, either already applied or with potential for application in the fabrication of macro-structured catalysts containing 1D carbon nanomaterials. A review of the processing methods used in the fabrication of macrostructures containing 1D sp2 hybridized carbon nanomaterials is presented. The carbon nanomaterials here discussed include single- and multi-walled carbon nanotubes, and several types of carbon nanofibers (fishbone, platelet, stacked cup, etc.). As the processing methods used in the fabrication of the macrostructures are generally very similar for any of the carbon nanotubes or nanofibers due to their similar chemical nature (constituted by stacked ordered graphene planes), the review aggregates all under the carbon nanofiber (CNF) moniker. The review is divided into methods where the CNFs are synthesized already in the form of a macrostructure (in situ methods) or where the CNFs are previously synthesized and then further processed into the desired macrostructures (ex situ methods). We highlight in particular the advantages of each approach, including a (non-exhaustive) description of methods commonly described for in situ and ex situ preparation of the catalytic macro-structures. The review proposes methods useful in the preparation of catalytic structures, and thus a number of techniques are left out which are used in the fabrication of CNF-containing structures with no exposure of the carbon materials to reactants due to, for example, complete coverage of the CNF. During the description of the methodologies, several different macrostructures are described. A brief overview of the potential applications of such structures in catalysis is also offered herein, together with a short description of the catalytic potential of CNFs in general.

Conformal High-K Dielectric Coating of Suspended Single-Walled Carbon Nanotubes by Atomic Layer Deposition

As one of the highest mobility semiconductor materials, carbon nanotubes (CNTs) have been extensively studied for use in field effect transistors (FETs). To fabricate surround-gate FETs- which offer the best switching performance-deposition of conformal, weakly-interacting dielectric layers is necessary. This is challenging due to the chemically inert surface of CNTs and a lack of nucleation sites-especially for defect-free CNTs. As a result, a technique that enables integration of uniform high-k dielectrics, while preserving the CNT's exceptional properties is required. In this work, we show a method that enables conformal atomic layer deposition (ALD) of high-k dielectrics on defect-free CNTs. By depositing a thin Ti metal film, followed by oxidation to TiO₂ under ambient conditions, a nucleation layer is formed for subsequent ALD deposition of Al₂O₃. The technique is easy to implement and is VLSI-compatible. We show that the ALD coatings are uniform, continuous and conformal, and Raman spectroscopy reveals that the technique does not induce defects in the CNT. The resulting bilayer TiO₂/Al₂O₃ thin-film shows an improved dielectric constant of 21.7 and an equivalent oxide thickness of 2.7 nm. The electrical properties of back-gated and top-gated devices fabricated using this method are presented.

Anchoring conductive polymeric monomers on single-walled carbon nanotubes: towards covalently linked nanocomposites

Chemical functionalization with conductive polymeric monomers on carbon nanotubes carried out by a straightforward method.

Preparation of novel multi-walled carbon nanotubes nanocomposite adsorbent via RAFT technique for the adsorption of toxic copper ions

In the present work, polymer-coated multiwalled carbon nanotube (MWCNT) was prepared via RAFT method. First, a novel trithiocarbonate-based RAFT agent was prepared attached chemically into the surface of MWCNT. In addition, the RAFT co-polymerization of acrylic acid and acrylamide monomers was conducted through the prepared RAFT agent. In the next age, the surface morphology and chemical properties of the prepared components were fully examined by using FTIR, ¹HNMR, SEM, TEM, XRD and TGA/DTG techniques. Finally, the modified MWCNT composite was employed as an excellent adsorbent for the adsorption of copper (II) ions. The results indicated that ion adsorption basically relies on adsorbing time, solution pH, initial copper concentration, and adsorbent dosage. Further, the adsorption kinetics and isotherm analysis demonstrated that the adsorption mode was fitted with the pseudo-second-order and Langmuir isotherm models, respectively. Based on the results of thermodynamic study, the ion adsorption process was endothermic and spontaneous. Finally, based on the experimental results, the surface functionalized MWCNT with hydrophilic groups could be successfully used as a promising selective adsorbent material in wastewater treatment.

Synthesis of magnetic functionalized MWCNT nanocomposite through surface RAFT co-polymerization of acrylic acid and N-isopropyl acrylamide for removal of cationic dyes from aqueous solutions

In this study, magnetic multi-walled carbon nanotube (MMWCNT) composites were prepared via surface reversible addition fragmentation chain transfer (RAFT) co-polymerization of acrylic acid (AA) and N-isopropyl acrylamide (NIPAM) in the presence of Fe₃O₄ nanoparticles. First, a novel RAFT agent (RA) was prepared and then immobilized onto the surface of MWCNT to fabricate RA-g-MWCNT. Then, Fe₃O₄ nanoparticles were attached onto the surface of RA-g-MWCNT. Finally, RAFT co-polymerization of AA and NIPAM monomers was carried out via Fe₃O₄-g-RA-g-MWCNT RAFT agent. The structure and morphology of the prepared polymer-coated MWCNT was examined by FTIR, SEM, TEM, XRD, VSM, and TGA. The adsorption behaviours of the cationic dyes were studied. The equilibrium isotherm and kinetics of cationic dyes were investigated. Thermodynamics investigations also depicted that the adsorptions of cationic dyes were spontaneous and endothermic in nature. The synthesized dye adsorbent with high adsorption capacities, reusability, and easy recovery makes it as a good candidate for wastewater treatment.

Ultrasonic synthesis and characterization of poly(acrylamide)-co-poly(vinylimidazole)@MWCNTs composite for use as an electrochemical material

Applying a nanocomposite to increase the conductivity of an electrode can facilitate electrochemical analysis. In this regard, multi-walled carbon nanotubes (MWCNTs) evenly dispersed in hydrophilic solution can play an important role in electrochemical bio-sensing due to their unique properties, such as their high electrical conductivity and ability to conjugate with hydrophilic enzymes. Herein, we report the simple ultrasonic synthesis of a highly dispersible, enzyme-binding nanocomposite, poly(acrylamide)-co-poly(vinyl imidazole) (7:1 mol ratio)-MWCNTs (PAA-PVI@MWCNTs). This material, having a zeta potential of 36.6 ± 0.53 mV, was applied as a film to an electrode surface and stably bound with glucose oxidase to transfer an electron between the enzyme and electrode in the presence of glucose. The PAA-PVI@MWCNTs composite, which was readily dispersed in deionized water, can be used as a biocompatible material for applications such as bio-sensing, point-of-care testing (POCT), and other health care functions.

Polymer wrapping versus well-oriented crystal growth of polythiophenes onto multi-wall carbon nanotubes via surface chemical modification and regioregularity deliberation

Distinct nano-hybrids including double-fibrillar, shish–kebab, shish–kebab–shish, stem–leaf and stem–leaf–stem were developed using P3HT and CNTs.

Carbon Nanotube Membranes: Synthesis, Properties, and Future Filtration Applications

Over the course of the past decade, there has been growing interest in the development of different types of membranes composed of carbon nanotubes (CNTs), including buckypapers and composite materials, for an ever-widening range of filtration applications. This article provides an overview of how different types of CNT membranes are prepared and the results obtained from investigations into their suitability for different applications. The latter involve the removal of small particles from air samples, the filtration of aqueous solutions containing organic compounds and/or bacteria, and the separation of individual liquids present in mixtures. A growing number of reports have demonstrated that the incorporation of CNTs into composite membranes confers an improved resistance to fouling caused by biomacromolecules and bacteria. These results are discussed, along with evidence that demonstrates it is possible to further reduce fouling by taking advantage of the inherent conductivity of composite membranes containing CNTs, as well as by using different types of electrochemical stimuli.

A study on the fabrication of plasticized polystyrene-carbon nanotube nanocomposites for foaming

The impregnation of carbon nanotubes within fiber-reinforced polymers (FRPs) is a sought after capability for the advancement of composite systems. This study evaluates the novel processing of a carbon nanotube nanocomposite that has been developed to incorporate varying carbon nanotube loadings within final composite foams. This material is manufactured through a melt mix process of carbon nanotubes and polystyrene at ∼2.0–13.0 wt.% that further underwent a plasticization process in an acetone solvent. The chemical foaming agent 2.2′-Azobi(isobutyronitrile) is used to facilitate foaming at a constant 3.0 wt.% concentration. The foamed nanocomposite results in a carbon nanotube-loaded micro-porous structure showing capabilities of delivering localized carbon nanotube placement within fiber composite laminate systems. This report’s aim is to illustrate the effects of plasticizing polystyrene-carbon nanotube nanocomposite and calendaring the softened material to form foams imbedded with carbon nanotubes (carbon nanotubes). Scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and Fourier transform infrared spectroscopy were the tools that are used to characterize the materials at the various morphologies with their findings inclusive.

Metal ion-coordinated carboxymethylated chitosan grafted carbon nanotubes with enhanced antibacterial properties

Multiwalled carbon nanotubes were covalently bonded with carboxymethyl chitosan using the grafting method. The composites revealed notable controlled release properties and, after coordination with metal ions, the complexes exhibited good long-term antibacterial properties.

Reinforcement effects of nanocarbons on catalyst behaviour and polyethylene properties through in situ polymerization

MWCNT (multi-walled carbon nanotube), MWCNT-COOH and xGnP (exfoliated graphene nanoplatelet) were used by in-situ polymerization of ethylene in presence of a binuclear complex (BNC₄).

Influence of chemically and plasma-functionalized carbon nanotubes on high-performance polymeric nanocomposites

This investigation highlights different surface functionalization processes of multi-walled carbon nanotubes (MWCNTs) and their effects on mechanical properties of polyetherimide nanocomposite. Surfaces of MWCNTs were modified by chemical process and by low-pressure plasma process. There is a significant change in physicochemical characteristics of MWCNTs after chemical and low plasma treatment evident from scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy studies. Due to surface modification of CNTs, there is a significant change in surface morphology and increase in oxygen functionalities such as C=O, C–O, and COOH especially evident in low-pressure plasma treatment; however, differential scanning calorimeter and thermogravimetric analysis studies reveal that thermal properties of the composite do not alter as such. There is a significant increase in mechanical properties of high-performance polymeric nanocomposites when surface-functionalized MWCNTs are dispersed in polymeric matrix; however, surface characteristics of the composite remain almost unchanged evident from contact angle and surface energy studies.

Progress towards high-power Li/CFx batteries: electrode architectures using carbon nanotubes with CFx

This perspective describes the current status of lithium–carbon monofluoride batteries and highlights the opportunities for the development of high-power Li/CF_x batteries via utilization of carbon nanotubes.

Functionalized multi-walled carbon nanotubes as an efficient reusable heterogeneous catalyst for green synthesis of N-substituted pyrroles in water

In this protocol, the functionalization of multi-walled carbon nanotubes (MWCNTs) was investigated and they were applied as a recyclable heterogeneous catalyst for the synthesis of N-substituted pyrroles.

Amino-functionalization of carbon nanotubes by using a factorial design: human cardiac troponin T immunosensing application

A simple amino-functionalization method for carbon nanotubes and its application in an electrochemical immunosensor for detection of the human cardiac troponin T are described. Amino-functionalized carbon nanotubes allow oriented antibodies immobilization via their Fc regions, improving the performance of an immunosensor. Herein multiwalled carbon nanotubes were amino-functionalized by using the ethylenediamine reagent and assays were designed by fractional factorial study associated with Doehlert matrix. Structural modifications in the carbon nanotubes were confirmed by Fourier transform infrared spectroscopy. After amino-functionalization the carbon nanotubes were attached to screen-printed carbon electrode and a sandwich-type immunoassay was performed for measuring the cardiac troponin T. The electrochemical measurements were obtained through hydrogen peroxide reaction with peroxidase conjugated to the secondary antibody. Under optimal conditions, troponin T immunosensor was evaluated in serum samples, which showed a broad linear range (0.02 to 0.32 ng mL⁻¹) and a low limit of detection, 0.016 ng mL⁻¹. This amino platform can be properly used as clinical tool for cardiac troponin T detection in the acute myocardial infarction diagnosis.

Flexible carbon nanotube films for high performance strain sensors

Compared with traditional conductive fillers, carbon nanotubes (CNTs) have unique advantages, i.e., excellent mechanical properties, high electrical conductivity and thermal stability. Nanocomposites as piezoresistive films provide an interesting approach for the realization of large area strain sensors with high sensitivity and low manufacturing costs. A polymer-based nanocomposite with carbon nanomaterials as conductive filler can be deposited on a flexible substrate of choice and this leads to mechanically flexible layers. Such sensors allow the strain measurement for both integral measurement on a certain surface and local measurement at a certain position depending on the sensor geometry. Strain sensors based on carbon nanostructures can overcome several limitations of conventional strain sensors, e.g., sensitivity, adjustable measurement range and integral measurement on big surfaces. The novel technology allows realizing strain sensors which can be easily integrated even as buried layers in material systems. In this review paper, we discuss the dependence of strain sensitivity on different experimental parameters such as composition of the carbon nanomaterial/polymer layer, type of polymer, fabrication process and processing parameters. The insights about the relationship between film parameters and electromechanical properties can be used to improve the design and fabrication of CNT strain sensors.

Organic semiconductors for device applications: current trends and future prospects

With the rich experience of developing silicon devices over a period of the last six decades, it is easy to assess the suitability of a new material for device applications by examining charge carrier injection, transport, and extraction across a practically realizable architecture; surface passivation; and packaging and reliability issues besides the feasibility of preparing mechanically robust wafer/substrate of single-crystal or polycrystalline/amorphous thin films. For material preparation, parameters such as purification of constituent materials, crystal growth, and thin-film deposition with minimum defects/disorders are equally important. Further, it is relevant to know whether conventional semiconductor processes, already known, would be useable directly or would require completely new technologies. Having found a likely candidate after such a screening, it would be necessary to identify a specific area of application against an existing list of materials available with special reference to cost reduction considerations in large-scale production. Various families of organic semiconductors are reviewed here, especially with the objective of using them in niche areas of large-area electronic displays, flexible organic electronics, and organic photovoltaic solar cells. While doing so, it appears feasible to improve mobility and stability by adjusting π-conjugation and modifying the energy band-gap. Higher conductivity nanocomposites, formed by blending with chemically conjugated C-allotropes and metal nanoparticles, open exciting methods of designing flexible contact/interconnects for organic and flexible electronics as can be seen from the discussion included here.

Carbon nanotubes reinforced composites for biomedical applications

This review paper reported carbon nanotubes reinforced composites for biomedical applications. Several studies have found enhancement in the mechanical properties of CNTs-based reinforced composites by the addition of CNTs. CNTs reinforced composites have been intensively investigated for many aspects of life, especially being made for biomedical applications. The review introduced fabrication of CNTs reinforced composites (CNTs reinforced metal matrix composites, CNTs reinforced polymer matrix composites, and CNTs reinforced ceramic matrix composites), their mechanical properties, cell experiments in vitro, and biocompatibility tests in vivo.

Polymer Composites Reinforced by Nanotubes as Scaffolds for Tissue Engineering

The interest in polymer based composites for tissue engineering applications has been increasing in recent years. Nanotubes materials, including carbon nanotubes (CNTs) and noncarbonic nanotubes, with unique electrical, mechanical, and surface properties, such as high aspect ratio, have long been recognized as effective reinforced materials for enhancing the mechanical properties of polymer matrix. This review paper is an attempt to present a coherent yet concise review on the mechanical and biocompatibility properties of CNTs and noncarbonic nanotubes/polymer composites, such as Boron nitride nanotubes (BNNTs) and Tungsten disulfide nanotubes (WSNTs) reinforced polymer composites which are used as scaffolds for tissue engineering. We also introduced different preparation methods of CNTs/polymer composites, such as in situ polymerization, solution mixing, melt blending, and latex technology, each of them has its own advantages.