Non-covalent Functionalization Of Carbon Nanotubes Research Articles

Glucose Biosensors - State of the Art and Prospects

Rapid glucose concentration detection in technical and biological systems is an important scientific and technical task of modern chemistry, engineering and technology. The article provides an overview of the last technical solutions in this area. The issues of developing first generation biosensors are considered. However, the main disadvantage of such systems was the significant influence of ascorbic and uric acids on the generated signal, which significantly reduced their selectivity and accuracy. To solve this problem, it is possible to use ion-selective membranes such as Nafion and polycarbonate. The second generation of glucose biosensors uses artificial mediators to facilitate electron transfer between the enzyme and the electrode. These mediators can be immobilized directly by the enzyme or introduced into an enzyme-modified electrode. Suitable mediators include conducting organic salts, ferrocene, quinone compounds, ferricyanide, transition metal complexes, phenothiazine and foxazine compounds. Effective interactions between enzymes and mediators are critical for efficient electron transport. Various approaches have been proposed to tailor mediators, such as the use of Os complexes, noncovalent functionalization of carbon nanotubes, and stabilization of artificial mediators. The third generation of enzyme glucose biosensors uses direct electron transfer to perform electrochemical reduction. Various approaches have been considered, including reassembling apoproteins on cofactor-modified enzymes and electrically coupling enzymes to electrode surfaces using redox polymers or nanomaterials such as gold nanoparticles. Such approaches ensure the formation of an effective enzyme-electrode bond. In addition, the thickness of the enzymatic layer can affect the performance of the biosensor. External factors such as temperature, pH and humidity can have a significant impact on the performance of such electrodes.

Noncovalent functionalization of carbon nanotubes as a scaffold for tissue engineering

Tissue engineering is one of the hot topics in recent research that needs special requirements. It depends on the development of scaffolds that allow tissue formation with certain characteristics, carbon nanotubes (CNTs)-collagen composite attracted the attention of the researchers with this respect. However, CNTs suffer from low water dispersibility, which hampered their utilization. Therefore, we aim to functionalize CNTs non-covalently with pyrene moiety using an appropriate hydrophilic linker derivatized from polyethylene glycol (PEG) terminated with hydroxyl or carboxyl group to disperse them in water. The functionalization of the CNTs is successfully confirmed by TEM, absorption spectroscopy, TGA, and zeta potential analysis. 3T3 cells-based engineered connective tissues (ECTs) are generated with different concentrations of the functionalized CNTs (f-CNTs). These tissues show a significant enhancement in electrical conductivity at a concentration of 0.025%, however, the cell viability is reduced by about 10 to 20%. All ECTs containing f-CNTs show a significant reduction in tissue fibrosis and matrix porosity relative to the control tissues. Taken together, the developed constructs show great potential for further in vivo studies as engineered tissue.

Microtubule-inspired functionalization of carbon nanotubes: a biomimetic carrier design

A strategy is proposed for the non-covalent functionalization of carbon nanotubes based on biomimicry of the cytoskeletal protein, microtubule.

Non-covalent functionalization of CNTs with Chitosan for drug delivery system

Nanotechnology of drug delivery is a new topic aimed at delivering medications to the desired places, such as tumor tissues, while reducing the chemotherapeutic drug adverse effects on adjacent tissues. A new form of nanomaterial has been discovered, which expands the possibilities for drug delivery systems. The carbon nanotube (CNT) is a novel type of synthetic material that has shown great potential for targeted delivery of anti-cancer drug agents. The initial problem for biomedical applications of CNT has been its hydrophobicity. A major stage in the biomedical application of CNT is proper surface modification or CNT functionalization, in order to prepare well-dispersed and biocompatible CNT in biological fluids.The goul of this study is to noncovalently functionalize of multi-walled carbon nanotubes conjugated with chitosan in various concentrations for the delivery of the chemotherapy drug paclitaxel (PTX) to breast cancer cell line. After that, characterize and investigate in vitro cell cytotoxicity of f-CNTs with and without Paclitaxel (PTX). The chitosan conjugate was synthesized and the conjugation was confirmed using Fourier transform infrared spectroscopy. The average diameter of MWCNT is 42.27 nm and the MWCNT/CHI is 48.48 nm. MWCNT exhibit stability in polymeric system (CHI) based formulation in terms of greater ζ-potential values with f-CNTs, higher entrapment efficiency was achieved with a maximum efficiency of 200 μg/ml.MDA-MB-231 cell line was exploited for cytotoxicity evaluations. MWCNT and MWCNT/CHI in different concentrations demonstrated insignificant cytotoxic effects on MDA-MB-231cell line. Nevertheless, at lower Paclitaxel concentration (100μg/ml), fMWCNTs with PTX demonstrated a considerable reduction in cell viability.

Highly sensitive and selective sensing of acetone and hydrogen sulfide using metal phthalocyanine – carbon nanotube hybrids

Noncovalent functionalization of carbon nanotubes with metal phthalocyanine has great potential for sensor nanodevices, nevertheless, some aspects of their electron transport mechanism behind the sensing properties have not been understood yet. Here, we evaluate the sensing performance of metal phthalocyanine – carbon nanotube hybrids for acetone and hydrogen sulfide (H2S) detection in terms of sensitivity and selectivity, using density functional theory and the non-equilibrium Green’s function method. We systematically investigated the effects of central transition metal atoms (Fe, Co, and Mn) of metal phthalocyanine with different chiralities (quasi-metallic CNT (9,0) zigzag and metallic CNT(5,5) armchair) of single-walled carbon nanotubes and tuning the gate voltages making this nanosensor highly sensitive and selective to acetone and H2S.

A review on the mechanical properties of polymer composites reinforced by carbon nanotubes and graphene

Compared to carbon nanotubes (CNTs), graphene possesses high strength due to wrinkled surface texture caused by a high density of surface defects which benefits more contact with the polymer material than a rolled-up CNT. In the present review, we have discussed and compared the various properties of CNTs (1-D) and graphene (2-D) obtained in experimental results. The effects of covalent and non-covalent functionalization of CNTs and graphene on the properties of its composites have also been reviewed and compared. A comparative analysis has been carried out between CNTs and graphene-reinforced polymer composites. Furthermore, the synergetic effects of CNTs and graphene hybrid nanofiller on the mechanical properties of polymer composites have also been briefly discussed. Finally, this review concludes with the potential application and future challenges are discussed with regards to filler and their polymer composites.

Noncovalent functionalization of carbon nanotubes by polyaniline molecules: Raman analysis

Polyaniline/single-walled carbon nanotube composite (PANI4@SWCNT) has been studied theoretically by means of Raman spectroscopy calculations. We evidence that the structural organization of the nanohybrid systems depends on the diameter of carbon nanotubes. To study the stability of PANI4 molecules encapsulated in the cavity of the SWCNTs, the optimum configurations of PANI4 inside carbon nanotubes are derived from minimum energy calculations using a convenient Lennard-Jones expression. We discussed also two important Raman features of SWCNTs before and after encapsulation of PANI4 including the G-band and the radial breathing mode (RBM) taking into account its metallic or semiconducting character. The G-band shift suggests a significant charge transfer between the PANI4 and the nanotubes.

Insights into the π - π interaction driven non-covalent functionalization of carbon nanotubes of various diameters by conjugated fluorene and carbazole copolymers.

We investigate the interaction of polyfluorene and fluorene/carbazole copolymers bearing various functional groups and side chains with small to large diameter-from 1.7 nm to 9 nm-carbon nanotubes (CNTs) in vacuo. We use variable-charge molecular dynamics simulations based on the reactive force field ReaxFF. We show that non-covalent functionalization of nanotubes, driven by π - π interactions, is effective for all the polymers studied, thanks to their conjugated backbone and regardless of the presence of specific functional groups. The geometry at equilibrium of these polymer/CNT hybrids is analyzed in detail at the scale of each fluorene or carbazole unit. The role of both the functional groups and the alkyl chain length is analyzed in detail. Adsorption of the polymers on the nanotube sidewalls is shown to be either complete-with the whole chain physisorbed-or partial-due to intrachain coiling or interchain repulsion-depending on the initial geometry, number of polymers, and nanotube diameter. Energetic arguments supplement the described geometric features. Both energetic and geometric adsorption features are derived here for the first time for large diameter carbon nanotubes (up to 9 nm) and fluorene/carbazole copolymers having up to 30 monomers and bearing different functional groups. The force field ReaxFF and its available parameterization used for the simulations are validated, thanks to a benchmark and review on higher-level quantum calculations-for simple π - π interacting compounds made up of polycyclic aromatic molecules adsorbed on a graphene sheet or bilayer graphene. Although it is shown that the influence of the nanotube chirality on the adsorption pattern and binding strength cannot be discussed with our method, we highlight that an available force field such as ReaxFF and its parameterization can be transferable to simulate new systems without specific re-parameterization, provided that this model is validated against reference methods or data. This methodology proves to be a valuable tool for optimal polymer design for nanotube functionalization at no re-parameterization cost and could be adapted to simulate and assist the design of other types of molecular systems.

Phosphonium-based ionic liquid as crosslinker/dispersing agent for epoxy/carbon nanotube nanocomposites: electrical and dynamic mechanical properties

Phosphonium-based ionic liquid (IL), tributyl(ethyl)-phosphonium diethylphosphate, was investigated as the curing agent for the preparation of nanocomposites involving multi-walled carbon nanotube (CNT) and epoxy resin (ER). Different mixing procedures were employed in order to attain better filler dispersion within the epoxy matrix. The dispersion effectiveness was evaluated by rheological behavior and transmission electron microscopy. Also the electrical conductivity and dynamic mechanical properties were investigated as a function of the mixing procedure. The AC electrical conductivity stayed in the range of 0.10–0.5 S m−1 with the addition of 1 phr of CNT. The non-covalent functionalization of CNT with the IL by previously milling the CNT with IL in a mortar resulted in better reinforcing effect and higher conductivity. Thus, the use of high shear speed mixer combined with acetone was considered the best mixing conditions. At these conditions, composites with high electrical conductivity and better dynamic mechanical properties were obtained. The effect of the amounts of CNT on the main properties of the ER-based nanocomposites was also investigated for systems cured with different amounts of IL. Both systems displayed low electrical percolation (1.6 × 10−4 and 4.7 × 10−4 volume fraction for systems cured with 10 or 30 phr of IL, respectively). Lower amount of IL resulted in outstanding dynamic mechanical properties, as well as better thermal stability.

Study on the performance of syntactic foam reinforced by hybrid functionalized carbon nanotubes

ABSTRACTHollow glass microspheres (HGMs)/epoxy syntactic foam were reinforced by hybrid functionalized carbon nanotubes that were synthesized by simultaneous covalent and noncovalent functionalization of carbon nanotubes. The effect of hybrid functionalized carbon nanotubes on density, mechanical properties, and water absorption of HGMs/epoxy syntactic foam was studied. The study indicated that the dispersion of carbon nanotubes in epoxy resin can be improved by hybrid functionalization. The compression strength of syntactic foam reinforced by hybrid functionalized carbon nanotubes was significantly enhanced. The maximum compressive strength of syntactic foam corresponding to chitosan modified carbon nanotubes approached 60 MPa. Hybrid functionalized carbon nanotubes had little effect on the water absorption ability of syntactic foam, and was less than 1%. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48586.

Electrochemical Detection of Micro-RNAs As Potential Cancer Biomarker

MicroRNAs (miRNAs) are single-stranded RNA transcripts, typically of 19–23 nucleotides in length. Recently, miRNAs have been identified as important biomarkers that hold promise in early cancer diagnosis. Accumulative evidences have proved that abnormal expression of miRNAs is closely related with the occurrence, diagnosis and treatment of cancer [1]. Conventional methods of miRNA detection have some intrinsic drawbacks including the need for tedious and complex procedures, requirement of large amount of samples, highly skilled experts and high-end equipment. To address these shortcomings as well as to provide multiplexing capability, different types of electrochemical cancer biosensors have been developed. Electrochemical biosensors have been widely paid attention due to their merits including high sensitivity, specificity, low-cost, and multiplexing [2]. Herein, a label-free and sensitive biosensor was developed for miRNA-21 detection at femtomolar concentrations. A glassy carbon electrode (GCE) was first modified with carbon nanotube (CNT) which serves as platform for immobilization of probe DNA as well as providing higher surface area. Capture DNA probes were immobilized onto the surface of CNT modified electrode using an established molecular tethering method [3,4]. Electrochemical analyses confirmed the surface modification, immobilization, and hybridization between probe DNA and the target miRNA. Besides, different variables such as probe concentration and hybridization time were investigated and optimized to find the optimal experimental conditions for miRNA detection. The obtained results demonstrated that the proposed biosensor exhibits excellent analytical properties including high sensitivity, low detection limit, selectivity, and reproducibility for miRNA detection. References Lan H, Lu H, Wang X, Jin H (2015) MicroRNAs as potential biomarkers in cancer: opportunities and challenges. BioMed research international 2015Kilic T, Erdem A, Ozsoz M, Carrara S (2018) MicroRNA biosensors: Opportunities and challenges among conventional and commercially available techniques. Biosensors and Bioelectronics 99:525-546Ramasamy RP, Luckarift HR, Ivnitski DM, Atanassov PB, Johnson GR (2010) High electrocatalytic activity of tethered multicopper oxidase–carbon nanotube conjugates. Chemical Communications 46 (33):6045-6047Zhou Y, Fang Y, Ramasamy RP (2019) Non-covalent functionalization of carbon nanotubes for electrochemical biosensor development. Sensors 19 (2):392

An Experimental and Theoretical Study of Biodegradable Gemini Surfactants and Surfactant/Carbon Nanotubes (CNTs) Mixtures as New Corrosion Inhibitor

Inhibition performance of noncovalent functionalization of carbon nanotubes (CNTs) with biodegradable gemini surfactants on mild steel surface in 2 M hydrochloric acid solution was examined by potentiodynamic polarization, electrochemical impedance spectroscopy and quantum chemical calculations. Ultraviolet–visible (UV–vis) spectroscopy, thermogravimetric analysis, Raman analysis, and zeta-potential (Z-potential) measurements are also applied to discuss the stability of studied solutions. Ester-containing cationic surfactants; monomeric betainate, dodecyl esterquat gemini (ET), and dodecyl betainate gemini (BT) were used as potentially superior noncovalent functionalization agents for CNT-based formulations. For the first time, the anticorrosive efficiency of these surfactants on mild steel was investigated. The noncovalent functionalization of CNTs with ester-containing surfactants showed more appropriate inhibition properties at higher surfactant concentrations as a result of further dispersing ability. The best inhibition efficiency (IEE = 93%) is reported for BT (2.5 mM)-suspended nanotubes, while the effectiveness is decreased (IEE = 12%) dramatically at low concentration (0.1 mM). Surface observations are also employed to verify the corrosion protection of mild steel covered with noncovalent functionalization of CNTs. Density functional theory was employed for quantum chemical calculations, and a good correlation between experimental data and theoretical data has been obtained.

Versatile Multi-Functional Block Copolymers Made by Atom Transfer Radical Polymerization and Post-Synthetic Modification: Switching from Volatile Organic Compound Sensors to Polymeric Surfactants for Water Rheology Control via Hydrolysis.

Novel, multipurpose terpolymers based on styrene (PS), tert-butyl methacrylate (tBMA) and glycidyl methacrylate (GMA), have been synthesized via Atom Transfer Radical Polymerization (ATRP). Post-synthetic modification with 1-pyrenemethylamine (AMP) allows non-covalent functionalization of carbon nanotubes, eventually yielding a conductive nanocomposite materials capable of interacting with different Volatile Organic Compounds (VOCs) by electrical resistance variation upon exposure. Moreover, facile hydrolysis of the tBMA group yields polyelectrolytic macrosurfactants with remarkable thickening properties for promising applications in water solution, such as Enhanced Oil Recovery (EOR).

Non-Covalent Functionalization of Carbon Nanotubes for Electrochemical Biosensor Development.

Carbon nanotubes (CNTs) have been widely studied and used for the construction of electrochemical biosensors owing to their small size, cylindrical shape, large surface-to-volume ratio, high conductivity and good biocompatibility. In electrochemical biosensors, CNTs serve a dual purpose: they act as immobilization support for biomolecules as well as provide the necessary electrical conductivity for electrochemical transduction. The ability of a recognition molecule to detect the analyte is highly dependent on the type of immobilization used for the attachment of the biomolecule to the CNT surface, a process also known as biofunctionalization. A variety of biofunctionalization methods have been studied and reported including physical adsorption, covalent cross-linking, polymer encapsulation etc. Each method carries its own advantages and limitations. In this review we provide a comprehensive review of non-covalent functionalization of carbon nanotubes with a variety of biomolecules for the development of electrochemical biosensors. This method of immobilization is increasingly being used in bioelectrode development using enzymes for biosensor and biofuel cell applications.

Noncovalent functionalization of carbon nanotubes via co-deposition of tannic acid and polyethyleneimine for reinforcement and conductivity improvement in epoxy composite

In this paper, a novel strategy via one-pot co-deposition of tannic acid (TA) and polyethyleneimine (PEI) to modify the MWCNTs was reported, which allows to modify MWCNTs with polymer via robust linkage in a convenient, green and nondestructive way. The obtained TA-PEI modified MWCNTs (TA-PEI/MWCNTs) with abundant amine and imine groups have good dispersibility in various solvents as well as epoxy resin. Epoxy composites reinforced with TA-PEI/MWCNTs were prepared and their mechanical properties was studied in detail. The modification of MWCNTs by TA-PEI could not only enhance the compatibility of MWCNTs with epoxy resin, but also improve the interface interaction between MWCNTs and epoxy matrix caused by the curing reaction between epoxy and amine groups on MWCNTs surface. With the 0.4 wt% loading of TA-PEI/MWCNTs, the impact strength and tensile strength of the composite reach 40.51 kJ/m2 and 80.83 MPa, improved by 154% and 148% compared with pristine MWCNTs/epoxy composites, respectively, clearly demonstrating the important role of TA-PEI modification. In addition, the glass transition temperature (Tg) of the composite is 152.4 °C which is significantly higher than pure epoxy resin (136.9 °C) and MWCNTs/epoxy (142.0 °C). Furthermore, the electrical conductivity of the epoxy composite was also remarkably enhanced.

Pillar[5]arene-Decorated Single-Walled Carbon Nanotubes.

Control of single-walled carbon nanotube dispersion properties is of substantial interest to the scientific community. In this work, we sought to investigate the effect of a macrocycle, pillar[5]arene, on the dispersion properties of a polymer–nanotube complex. Pillar[5]arenes are a class of electron-rich macrocyclic hosts capable of forming inclusion complexes with electron-poor guests, such as alkyl nitriles. A hydroxyl-functionalized pillar[5]arene derivative was coupled to the alkyl bromide side chains of a polyfluorene, which was then used to coat the surface of single-walled carbon nanotubes. Noncovalent functionalization of carbon nanotubes with the macrocycle-containing conjugated polymer significantly enhanced nanotube solubility, resulting in dark and concentrated nanotube dispersions (600 μg mL–1), as evidenced by UV–vis–NIR spectroscopy and thermogravimetric analysis. Differentiation of semiconducting and metallic single-walled carbon nanotube species was analyzed by a combination of UV–vis–NIR, Raman, and fluorescence spectroscopy. Raman spectroscopy confirmed that the concentrated nanotube dispersion produced by the macrocycle-containing polymer was due to well-exfoliated nanotubes, rather than bundle formation. The polymer–nanotube dispersion was investigated using 1H NMR spectroscopy, and it was found that host–guest chemistry between pillar[5]arene and 1,6-dicyanohexane occurred in the presence of the polymer–nanotube complex. Utilizing the host–guest capability of pillar[5]arene, the polymer–nanotube complex was incorporated into a supramolecular organogel.

Non-Covalent Functionalization of Carbon Nanotubes by Phthalocyanines Analyzed by Spatial-Resolved EELS

Non-Covalent Functionalization of Carbon Nanotubes by Phthalocyanines Analyzed by Spatial-Resolved EELS

Noncovalent functionalization of carbon nanotubes using branched random copolymer for improvement of thermal conductivity and mechanical properties of epoxy thermosets

AbstractA branched random copolymer, poly[(hydroxyethyl acrylate)‐r‐(N‐vinylcarbazole)] (BPHNV), was synthesized through a facile one‐pot free radical polymerization with hydroxyethyl acrylate and N‐vinylcarbazole monomers, using 4‐vinylmethylmercaptan as the chain transfer agent. BPHNV was employed to noncovalently modify multiwall carbon nanotubes (MWCNTs) by π–π interaction. The as‐modified MWCNTs were then incorporated into epoxy resin to improve the thermal conductivity and mechanical properties of epoxy thermosets. The results suggest that, due to both the conjugation structure and the epoxy‐philic component, BPHNV could form a polymer layer on the wall of MWCNTs and inhibit entanglement, helping the uniform dispersion of MWCNTs in epoxy matrix. Owing to the unprecedented thermal conductivity of MWCNTs and the enhancement in the interfacial interaction between fillers and matrix, the thermal conductivity of epoxy/MWCNTs/BPHNV composites increases by 78% at extremely low filler loadings, while the electrical resistivity is still maintained on account of the insulating polymer layer. Meanwhile, the mechanical properties and glass transition temperature (Tg) of the thermosets are elevated effectively, with no significant decrease occurring to the modulus. The addition of as little as 0.1 wt% of MWCNTs decorated with 1.0 wt% of BPHNV to an epoxy matrix affords a great increase of 130% in impact strength for the epoxy thermosets, as well as an increase of over 13 °C in Tg. © 2018 Society of Chemical Industry

Properties of Functionalized Carbon Nanotubes and Their Interaction with a Metallic Substrate Investigated by Scanning Tunneling Microscopy

Noncovalent functionalization of carbon nanotubes (CNTs) allows the combination of the remarkable physical properties of these one-dimensional systems with the properties of the functional molecules and, at the same time, modifies the physicochemical properties of nanotubes for specific applications. The use of functionalized carbon nanotubes in electronics often requires the deposition of the nanotubes on a substrate, and eventually an annealing step, which can modify their properties due to molecule–surface interactions. Using scanning tunneling microscopy/spectroscopy (STM/STS) and classical molecular dynamics (MD) simulations we studied the physical properties of carbon nanotubes functionalized with porphyrin derivatives and discuss the effect of physisorption and sample annealing on the nanotube surface. The results reveal that the functionalized parts exhibit nonperiodic structure with a significant modification of the local density of states. The coverage degree can be estimated from STM images. Wh...

High-Performance Silicone Rubber Composites via Non-Covalent Functionalization of Carbon Nanotubes

ABSTRACTA high-performance silicone rubber (SR) composite (denoted as SCT) filled with 5 phr functionalized carbon nanotubes (CNTs) and 40 phr fumed silica (SiO2) was prepared by mechanical blending. The CNTs were functionalized by tetrakis (phenylmethyl)-thioperoxydi (carbothioamide) (TBzTD); it contains four benzene rings that can interact with the CNTs via π–π interactions. Raman spectroscopy and X-ray photoelectron spectroscopy analysis demonstrated the existence of the π-π interactions between the CNTs and the TBzTD. Transmission electron microscopy and scanning electron microscopy confirmed the uniform dispersion of the CNTs in SR matrix and strong interfacial interactions between the SR and the CNTs. The effects of these non-covalently functionalized CNTs on the mechanical properties of the silica filled SR composites were fully investigated. The results showed that the tear strength of the SCT composite with TBzTD functionalized CNTs was significantly improved, by 249%, compared with that of the composite containing only SiO2. An obvious crack deflection occurred in the SCT during the tearing process, resulting in the enhanced tear strength.