Surface Functionalization Of Carbon Nanotubes Research Articles

Dispersion mechanism of nanoparticles and its role on mechanical, thermal and electrical properties of epoxy nanocomposites - A Review

The combined effect of nano-reinforcements on the mechanical performance of nanocomposites, which are a novel class of epoxy matrix hybrid nanocomposites containing multiwall carbon nanotubes (MWCNT), graphene, and nanodiamonds (NDs), is drawing substantial attention from many research communities. The discussion concentrates on the dispersion techniques adopted for the preparation of epoxy composites containing different types of nanoparticles (3-D fillers, nanofibers, nanotubes, and plate-like fillers). This review paper covers the electrical, thermal, and mechanical properties of carbon nanotubes (CNTs), graphene, and nanodiamond-reinforced epoxy nanocomposites and correlates them with the topographical features, morphology, weight fraction, dispersion state, and surface functionalization of CNTs, graphene, and nanodiamond. This review paper also summarises recent developments in the dispersion method of different carbon nanoparticles in epoxy matrix.

Unraveling the carbon dot bridges in oxidized carbon nanotubes for efficient microwave absorption

Carbon nanotube (CNT)-based composites hold immense promise in the realm of electromagnetic (EM) wave absorption. Surface functionalization of CNTs plays a pivotal role in augmenting their surface binding energy, thereby bolstering their affinity for composites. However, the incorporation of functional groups may disrupt the electronic configuration of sp2 plus delocalized π-bonds and impede electronic transport within the CNT framework. Herein, carbon dots (CDs) were introduced onto the surface of oxidized CNTs (O-CNTs) using a one-step hydrothermal method to enhance their bonding capability and microwave absorption performance. Analysis showed that the characteristic functional groups on the surfaces of the CDs formed amide bonds between the CNTs, bridging them with π-conjugated structures and repairing the blocked electron transport pathway triggered by carboxyl groups. The bridging accelerated the electron flow between adjacent CNTs and enhanced the electron jumping and migration in the CDs-CNTs system. Additionally, a comprehensive investigation of the heterogeneous charge distribution within the CDs bridges and their tunable band gap demonstrated their significant influence on polarization relaxation and conduction loss. In short, the study presents a novel functionalization theory for CNTs that exhibit remarkable microwave-absorption performance in X-band.

Functionalization of Carbon Nanotubes Surface by Aryl Groups: A Review.

The review is devoted to the methods of introducing aryl functional groups to the CNT surface. Arylated nanotubes are characterized by extended solubility, and are widely used in photoelectronics, semiconductor technology, and bioelectrocatalysis. The main emphasis is on arylation methods according to the radical mechanism, such as the Gomberg-Bachmann and Billups reactions, and the decomposition of peroxides. At the same time, less common approaches are also considered. For each of the described reactions, a mechanism is presented in the context of the effect on the properties of functionalized nanotubes and their application. As a result, this will allow us to choose the optimal modification method for specific practical tasks.

Surface functionalization of carbon nanotubes via plasma discharge: A review

• Plasma is mainly used as a non-destructive and fast method for the functionalization of carbon nanotubes. • The nature change of the carbon nanotubes occurs via functional groups formed on nanotubes using plasma functionalization. • Plasma Functionalized carbon nanotubes can dramatically improve some properties in the polymer matrix. • The creation of active sites on nanotubes by the plasma treatment can be used for grafting with metals. The use of carbon nanotubes in a wide range of academic and industrial fields has received considerable attention due to their uniqueness in structures and properties. Despite these advantages, there are still some significant challenges and drawbacks such as insolubility which can have negative impacts on the application process. The introduction of functional groups on the surface of carbon nanotube can overcome this obstacle. Plasma functionalization can be a preferred method in comparison to other ones as a quick and relatively non-destructive, as well as environmentally-friendly method for the surface functionalization of carbon nanotubes. This review presents a brief introduction to the types, properties, and functionalization methods of carbon nanotubes for a better understanding. The focus of this review is on the modification of carbon nanotubes through different types of plasma functionalization methods, notably plasmas that operate at an ambient temperature and atmospheric pressure, to improve their properties. It also investigates the results obtained from analytical methods for plasma treated carbon nanotubes.

Hybrid Plasma-Liquid Treatment of Carbon Nanotubes for Application in Direct Absorption Solar Thermal Collectors

Covalent functionalization of carbon nanotubes (CNTs) with oxygen-based or nitrogen-based functional groups is one of the most popular techniques to modify the surface energy and inherent properties of the CNTs.1 This functionalization generates interest for a broad range of applications including mechanically superior advanced composites,2 more sensitive gas sensors,3 enhanced energy storage materials4 or ultra-conductive fibers.5 As an alternative to the harsh chemicals used by traditional chemical functionalization, plasma-based surface treatments can be used with great efficacy and reduced reaction times, providing an array of application-specific benefits.Awareness of the environmental pollution caused by fossil fuels and the ever-increasing demand for energy has driven research focussed on zero-carbon renewable energy sources. Conscious of this, direct absorption solar thermal collectors are gaining prominence, both for domestic heating and steam generation. CNTs have been investigated as an additive to take advantage of the near blackbody absorption and high thermal conductivity to improve system efficiency. Critical to the success of the additive nanoparticles is the stability in the fluid, however, due to their high surface energy CNTs tend to agglomerate which can limit the efficacy of their integration into real-world products.In this work, macroscopic ribbon-like assemblies of carbon nanotubes are functionalized by plasma-induced non-equilibrium electrochemistry (PiNE) implemented through a simple direct current-based plasma-liquid system. This system utilizes the plasma-generated species in an electrolyte of 10 %vol ethanol in water, with or without a nitrogen precursor, for the oxygen and/or nitrogen functionalization of the carbon nanotube assembly. For this treatment, a ribbon-like piece of CNT was used as the anode and a helium plasma discharge triggered by applying 10 mA and 1 - 1.6 kV to act as the cathode. The plasma-generated species are then expected to migrate towards the CNTs and functionalize the sidewalls.The oxygen content is shown to be increased by between 70 % and 300 % when the treatment solution of 10 %vol ethanol is used in the ribbon electrode configuration. When ethylenediamine is added as a nitrogen precursor, the atomic concentration of nitrogen reaches 23 %, with amine groups, pyrrolic groups and graphitic nitrogen observed in the x-ray photoelectron spectra. This nitrogen content is unmatched in quantity when compared to either a simple soaking procedure or an electrolysis process with a platinum foil replacing the plasma as the counter-electrode. This demonstrates that the plasma either directly or indirectly, through plasma-generated species, facilitates and enhances the availability of nitrogen from the ethylenediamine precursor. The potential plasma-induced chemical pathways which lead to the functionalization of the CNTs are also investigated and discussed.In the application of a direct absorption solar collector system, it is found that the covalent functionalization provided by the plasma-liquid system enhances the stability of the CNT-ethylene glycol nanofluid, with the oxygen-functionalized samples producing the most stable nanofluids. This is explained through the lower value for contact angle measurements, suggesting greater hydrophobicity of the CNTs.References(1) Mallakpour, S.; Soltanian, S. Surface Functionalization of Carbon Nanotubes: Fabrication and Applications. RSC Adv. 2016, 6 (111), 109916–109935. https://doi.org/10.1039/c6ra24522f.(2) Williams, J.; Broughton, W.; Koukoulas, T.; Rahatekar, S. S. Plasma Treatment as a Method for Functionalising and Improving Dispersion of Carbon Nanotubes in Epoxy Resins. J. Mater. Sci. 2013, 48 (3), 1005–1013. https://doi.org/10.1007/s10853-012-6830-3.(3) Ham, S. W.; Hong, H. P.; Kim, J. H.; Min, S. J.; Min, N. K. Effect of Oxygen Plasma Treatment on Carbon Nanotube-Based Sensors. J. Nanosci. Nanotechnol. 2014, 14 (11), 8476–8481. https://doi.org/10.1166/jnn.2014.10007.(4) Hulicova-Jurcakova, D.; Seredych, M.; Lu, G. Q.; Bandosz, T. J. Combined Effect of Nitrogen- and Oxygen-Containing Functional Groups of Microporous Activated Carbon on Its Electrochemical Performance in Supercapacitors. Adv. Funct. Mater. 2009, 19 (3), 438–447. https://doi.org/10.1002/adfm.200801236.(5) Li, L.; Liu, E.; Shen, H.; Yang, Y.; Huang, Z.; Xiang, X.; Tian, Y. Charge Storage Performance of Doped Carbons Prepared from Polyaniline for Supercapacitors. J. Solid State Electrochem. 2011, 15 (1), 175–182. https://doi.org/10.1007/s10008-010-1087-8. Figure 1

Surface functionalization of CNTs with amine group and decoration of begonia-like ZnO for detection of antipyretic drug acetaminophen

Detection of hepatotoxic antipyretic drug acetaminophen (APAP) at nanomolar level is detailed in this paper. We have prepared a novel nanocomposite with excellent electrocatalytic property for the detection of APAP based on amine-functionalized multi-walled carbon nanotubes (NH2-MWCNTs) decorated zinc oxide (ZnO). Surface functionalization of carbon nanotubes with amine group using ultrasound-assisted approach and synthesis of begonia flower-like ZnO nanoparticles based on arginine-assisted aqueous solution method were performed. Techniques including UV–Vis, micro Raman spectroscopy, FTIR, XRD, elemental mapping, and SEM were used to record significant characterizations of synthesized materials for analysis. The outstanding surface controlled electrocatalysis of APAP at ZnO NPs/NH2-MWCNTs modified SPCE was evident from the well-defined redox peak currents observed at low potentials during electrochemical investigations. Moreover, the resultant ultra-low detection limit of 1 nM and very high sensitivity of 89.64 μA μM−1cm−2 showcase the excellent performance of proposed APAP sensor. We have investigated all the salient features of the APAP sensor as part of this work and it exhibited good stability, reproducibility, repeatability, and excellent anti-interference property. The practical feasibility of APAP detection was also evaluated by conducting experiment on real samples including APAP tablet, human urine, and human serum.

Synthesis, Characterization and Toxicity Assessment of the Novel Non covalent Functionalized Multi-walled Carbon Nanotubes with Glycyrrhizin, Curcumin and Rutin

Carbon nanotubes (CNTs) have emerged as a new group of novel multifunctional nanoparticles in biomedicine and can be classified into single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). In the present work, a simple and efficient method was introduced for non-covalent functionalization of CNTs through the incorporation of phytochemicals of Curcumin (CUR), Glycyrrhizin (GLY) and Rutin (RUT). Different functionalization of CNTs were employed and the obtained nanoparticles were characterized by TEM, EDX, size and, zeta analyzer. Furthermore cell toxicity studies were done on A549 cell line with MTT assay. The obtained results showed that non-covalent functionalization with CUR, GLY or RUT led to the stable suspension of CNTs in aqueous media comparable to the surfactant Tween 80 as the effective surfactant that revealed visually and by TEM images. Upon surface functionalization, an increase in the size and net zeta potentials, indicates surface functionalization of CNTs. Cytotoxicity data showed that functionalization with these phytochemicals can increase the IC 50 value of CNTs from 301 µg/mL to a maximum of 4088 µg/mL in RUT functionalized CNTs. Overall the data showed that CNTs can be functionalized through this feasible method and could be introduced as interesting less toxic drug delivery system.

Carbon Nanotubes: Smart Drug/Gene Delivery Carriers.

The unique properties of carbon nanotubes (CNTs) (such as their high surface to volume ratios, enhanced conductivity and strength, biocompatibility, ease of functionalization, optical properties, etc.) have led to their consideration to serve as novel drug and gene delivery carriers. CNTs are effectively taken up by many different cell types through several mechanisms. CNTs have acted as carriers of anticancer molecules (including docetaxel (DTX), doxorubicin (DOX), methotrexate (MTX), paclitaxel (PTX), and gemcitabine (GEM)), anti-inflammatory drugs, osteogenic dexamethasone (DEX) steroids, etc. In addition, the unique optical properties of CNTs have led to their use in a number of platforms for improved photo-therapy. Further, the easy surface functionalization of CNTs has prompted their use to deliver different genes, such as plasmid DNA (PDNA), micro-RNA (miRNA), and small interfering RNA (siRNA) as gene delivery vectors for various diseases such as cancers. However, despite all of these promises, the most important continuous concerns raised by scientists reside in CNT nanotoxicology and the environmental effects of CNTs, mostly because of their non-biodegradable state. Despite a lack of widespread FDA approval, CNTs have been studied for decades and plenty of in vivo and in vitro reports have been published, which are reviewed here. Lastly, this review covers the future research necessary for the field of CNT medicine to grow even further.

Immobilization of carbon nanotubes decorated gold nanoparticles on anodized aluminium oxide (Au-CNTs-AAO) membrane for enhanced catalytic performance

In recent years, the integration of nanostructure assemblies has led to unprecedented levels of control over the fabrication and functional properties of materials, with numerous potential applications. Here, we highlight the recent contributions towards the fabrication of multi-layered assemblies of carbon nanotubes (CNTs) decorated with gold nanoparticles (Au NPs) on porous materials. In this study, a three-component composite consisting of functionalized carbon nanotubes (CNTs), anodized aluminium oxide (AAO), and Au NPs was designed and synthesized in the form of a free-standing catalyst using a simple and unsophisticated technique for the first time. The AAO were coated with carbon nanotubes and gold nanoparticles and used as the supports for the catalytic. The CNTs-AAO composite was prepared by spin-coating of CNTs on the AAO surface. The Au NP layers were incorporated into the CNTs-AAO composite by immersing the composite in a gold solution. The Au-CNTs-AAO assemblies were tested for catalytic performance in the reduction of p-nitrophenol (p-NP) to p-aminophenol (p-AP). The Au-CNTs-AAO exhibited superior catalytic activity, with a reaction rate (k) of 0.678 min −1, higher than those of Au-CNTs and Au-AAO. Additionally, the Au-CNTs-AAO assemblies prepared with support of different AAO porosities showed that the catalytic activity increased as the pore diameter increased from 40 to 80 nm. Subsequently, it was demonstrated that the surface functionalization of CNTs with the silane moiety leads to higher catalytic activity compared to unfunctionalized CNTs. This efficient approach to the design and construction of this porous support improved the catalyst's properties in the reduction of p-NP, such as the catalytic performance, thermal stability, natural separation and reusability. These layered assemblies can potentially serve as a platform for various catalytic activities.

Carbon Nanotube Field-Effect Transistor-Based Chemical and Biological Sensors.

Chemical and biological sensors have attracted great interest due to their importance in applications of healthcare, food quality monitoring, environmental monitoring, etc. Carbon nanotube (CNT)-based field-effect transistors (FETs) are novel sensing device configurations and are very promising for their potential to drive many technological advancements in this field due to the extraordinary electrical properties of CNTs. This review focuses on the implementation of CNT-based FETs (CNTFETs) in chemical and biological sensors. It begins with the introduction of properties, and surface functionalization of CNTs for sensing. Then, configurations and sensing mechanisms for CNT FETs are introduced. Next, recent progresses of CNTFET-based chemical sensors, and biological sensors are summarized. Finally, we end the review with an overview about the current application status and the remaining challenges for the CNTFET-based chemical and biological sensors.

Surface functionalization of CNTs by a nitro group as a sensor device element: theoretical research

The problem of modifying carbon nanotubes (CNTs) by functional groups is relevant in connection with the intensive development of the nanoindustry, in particular, nano- and microelectronics. For example, a modified nanotube can be used as a sensor device element for detecting microenvironments of various substances, in particular, metals included in salts and alkalis. The paper discusses the possibility of creating a highly efficient sensor using single-walled carbon nanotubes as a sensitive element, the surface of which is modified with the functional nitro group —NO2. Quantum-chemical research of the process of attaching a nitro group to the outer surface of a single-walled CNTs of the (6, 0) type were carried out, which proved the possibility of modifying CNTs and the formation of a bond between the —NO2 group and the carbon atom of the nanotube surface. The results of computer simulation of the interaction process of a surface-modified carbon nanotube with alkali metal atoms (lithium, sodium, potassium) are presented. The sensory interaction of a modified carbon nanosystem with selected metal atoms was investigated, which proved the possibility of identifying these atoms using a nanotubular system that can act as a sensor device element. When interacting with alkali metal atoms in the “СNT – NO2” complex, the number of major carriers increases due to the transfer of electron density from metal atoms to the modified CNTs. The results presented in this paper were obtained using the molecular cluster model and the DFT calculation method with the exchange-correlation functional B3LYP (valence split basis set 6-31G).

Synthesis and plasma surface functionalization of carbon nanotubes for using in advanced epoxy-based nanocomposites

In this study, thermal chemical vapor deposition (CVD) method was utilized to fabricate carbon nanotubes (CNTs) using an Fe/Al catalyst. Plasma enhanced CVD (PECVD) was applied to coat CNTs surfaces with a hydrophobic poly(hexafluorobutyl acrylate) (PHFBA) thin film. Then pure CNT and surface-modified CNT (f-CNT) were used as nanofillers at 0.5–3 wt% in bisphenol-A (DGEBA) and phenolic novolac types epoxy (EPN) resins to produce composite materials with superior properties. For characterization of both types of CNTs, FTIR, XRD, SEM, TEM and TGA analyses were performed. The morphologies of composites were examined via XRD and SEM. Thermal properties of composites were revealed by TGA. The influences of CNT surface functionalization and matrix type on the thermal, mechanical, electrical conductivity and surface wettability properties of composites were investigated. EPN based composites exhibited higher mechanical properties than that DGEBA based ones. At 1.5 wt% f-CNTs, the Young's modulus and tensile strength of the nanocomposites were found 6.9 ± 0.50 GPa and 141.0 ± 7.8 MPa, respectively using DGEBA matrix; 8.7 ± 0.59 GPa and 153.4 ± 7.9 MPa respectively, using EPN matrix. Composites electrical conductivity increased with increasing both type CNTs amount and reached a maximum value of 10−4 S/m and 10−6 S/m at 3 wt% of neat and f-CNTs contents.

Hybrid Plasma-Liquid Treatment of Carbon Nanotubes for Application in Direct Absorption Solar Thermal Collectors

Awareness of the environmental pollution caused by fossil fuels and the ever-increasing demand for energy has driven research focussed on zero-carbon renewable energy sources. Conscious of this, direct absorption solar thermal collectors are gaining prominence, both for domestic heating and steam generation. Carbon nanotubes (CNTs) have been investigated as an additive to take advantage of the near blackbody absorption and high thermal conductivity to improve system efficiency. Critical to the success of the additive nanoparticles is the stability in the fluid, however, due to their high surface energy CNTs tend to agglomerate which can limit the efficacy of their integration into real-world products. Covalent functionalization of the CNT sidewalls with oxygen-based or nitrogen-based functional groups is one of the most popular techniques to modify the surface energy of the CNTs.1 As an alternative to the harsh chemicals used by traditional chemical functionalisation, plasma-based surface treatments can be used with great efficacy and reduced reaction times.In this work, macroscopic ribbon-like assemblies of carbon nanotubes are functionalized using a simple direct current-based plasma-liquid system. This system utilizes the plasma-generated species in a fluid of 10 %vol ethanol in water, with or without a nitrogen precursor, for the oxygen and/or nitrogen functionalisation of the carbon nanotube assembly. For this treatment, a ribbon-like piece of CNT was used as the anode and a helium plasma discharge triggered by applying 10 mA and 1 - 1.6 kV to act as the cathode. The plasma-generated species are then expected to migrate towards the CNTs and functionalisation the sidewalls.The oxygen content is shown to be increased by between 50 % and 200 % when the treatment solution of 10 %vol ethanol is used in the ribbon electrode configuration. When ethylenediamine is added as a nitrogen precursor, the atomic concentration of nitrogen reaches 23 % in the ribbon electrode configuration, with amine groups, pyrrolic groups and graphitic nitrogen observed in the x-ray photoelectron spectra. This nitrogen content is unmatched in quantity when compared to either a simple soaking procedure or an electrolysis process with a platinum foil replacing the plasma as the counter-electrode. This demonstrates that the plasma either directly or indirectly, by means of plasma-generated species, facilitates and enhances the availability of nitrogen from the ethylenediamine precursor. The potential plasma-induced chemical pathways which lead to the functionalization of the CNTs are also investigated and discussed.In the application of a DASC system, it is found that the covalent functionalisation provided by the plasma-liquid system enhances the stability of the CNT-EG nanofluid, with the oxygen-functionalized samples producing the most stable nanofluids. This functionalization method generates interest for a broader range of applications including mechanically superior advanced composites,2 more sensitive gas sensors,3 enhanced energy storage materials4 or ultra-conductive fibres.5 References (1) Mallakpour, S.; Soltanian, S. Surface Functionalization of Carbon Nanotubes: Fabrication and Applications. RSC Adv. 2016, 6 (111), 109916–109935.(2) Williams, J.; Broughton, W.; Koukoulas, T.; Rahatekar, S. S. Plasma Treatment as a Method for Functionalising and Improving Dispersion of Carbon Nanotubes in Epoxy Resins. J. Mater. Sci. 2013, 48 (3), 1005–1013.(3) Ham, S. W.; Hong, H. P.; Kim, J. H.; Min, S. J.; Min, N. K. Effect of Oxygen Plasma Treatment on Carbon Nanotube-Based Sensors. J. Nanosci. Nanotechnol. 2014, 14 (11), 8476–8481.(4) Hulicova-Jurcakova, D.; Seredych, M.; Lu, G. Q.; Bandosz, T. J. Combined Effect of Nitrogen- and Oxygen-Containing Functional Groups of Microporous Activated Carbon on Its Electrochemical Performance in Supercapacitors. Adv. Funct. Mater. 2009, 19 (3), 438–447.(5) Li, L.; Liu, E.; Shen, H.; Yang, Y.; Huang, Z.; Xiang, X.; Tian, Y. Charge Storage Performance of Doped Carbons Prepared from Polyaniline for Supercapacitors. J. Solid State Electrochem. 2011, 15 (1), 175–182. Figure 1

The Effect of Different Oxygen Surface Functionalization of Carbon Nanotubes on the Electrical Resistivity and Strain Sensing Function of Cement Pastes.

Different studies in the literature indicate the effectiveness of CNTs as reinforcing materials in cement–matrix composites due to their high mechanical strength. Nevertheless, their incorporation into cement presents some difficulties due to their tendency to agglomerate, yielding a non-homogeneous dispersion in the paste mix that results in a poor cement–CNTs interaction. This makes the surface modification of the CNTs by introducing functional groups on the surface necessary. In this study, three different treatments for incorporating polar oxygen functional groups onto the surface of carbon nanotubes have been carried out, with the objective of evaluating the influence of the type and oxidation degree on the mechanical and electrical properties and in strain-sensing function of cement pastes containing CNTs. One treatment is in liquid phase (surface oxidation with HNO3/H2SO4), the second is in gas phase (O3 treatment at 25 and 160 °C), and a third is a combination of gas-phase O3 treatment plus NaOH liquid phase. The electrical conductivity of cement pastes increased with O3- and O3-NaOH-treated CNTs with respect to non-treated ones. Furthermore, the oxygen functionalization treatments clearly improve the strain sensing performance of the CNT-cement pastes, particularly in terms of the accuracy of the linear correlation between the resistance and the stress, as well as the increase in the gage factor from 28 to 65. Additionally, the incorporation of either non-functionalized or functionalized CNTs did not produce any significant modification of the mechanical properties of CNTs. Therefore, the functionalization of CNTs favours the de-agglomeration of CNTs in the cement matrix and consequently, the electrical conductivity, without affecting the mechanical behaviour.

Surface functionalization of carbon nanotubes by biological adhesive polymers carbopol for developing high‐permittivity polymer composites

Surface functionalization of carbon nanotubes (CNTs) by biological adhesive polymers carbopol (CP) was developed by simply mixing CNT suspension and an aqueous solution of CP without any toxic solvents. CP can be easily coated onto CNTs through hydrogen bonds OCOH⋯NH2CO and electrostatic interaction between COO on CP and NH3+ on CNTs. After modification, the surface of the CNT is endowed with a large number of carboxyl groups, which can effectively prevent the reaggregation of CNT by electrostatic repulsion between the ionized carboxyl groups. Hence, highly dispersed functionally modifying CNT by CP (CP‐CNT) filler in polydimethylsiloxane (PDMS) matrix can be obtained. More important, with the help of adhesive properties of CP, the interfacial compatibility between fillers and matrix can also be improved. Thus, the CP‐CNT/PDMS composites exhibited higher dielectric permittivity comparing with CNT/PDMS composites at the same filler content. We present a potential and green approach of surface functionalization of CNT for preparing high‐permittivity polymer composites. J. VINYL ADDIT. TECHNOL., 26:165–172, 2020. © 2019 Society of Plastics Engineers

Succinylated β-Lactoglobuline-Functionalized Multiwalled Carbon Nanotubes with Improved Colloidal Stability and Biocompatibility.

PEGylation (i.e., attachment of polyethylene-glycol) of carbon nanotubes (CNTs) is one of the most widely used strategies to improve its biocompatibility and aqueous dispersion stability, which are critical for their successful clinical application. However, PEGylation of nanomaterials has recently been associated with production of anti-PEG antibody, low cellular uptake, and degradation. Herein, we explore surface functionalization of CNTs using the bovine-milk-derived protein succinylated β-lactoglobuline (Sblg) as an alternative strategy to PEGylation. The aqueous dispersion stability, in vitro cell uptake and biocompatibility of Sblg-functionalized multiwalled CNTs (Sblg-f-MWCNTs) was compared to PEGylated MWCNTs (PEG-f-MWCNTs). The surface functionalization with Sblg was found to improve the IC50 values of CNTs by ∼5- to 6-fold in comparison with pristine CNTs in various cell lines. Both Sblg-f-MWCNTs and PEG-f-MWCNTs improved the aqueous colloidal stability of CNTs, which remained suspended for a period of one month. Our study concluded that the Sblg provides a cost-effective alternative to the PEG-based CNT functionalization with significant improvement in the biocompatibility and dispersion stability of CNTs.

Comprehensive quantum chemical insight into the mechanistic understanding of the surface functionalization of carbon nanotube as a nanocarrier with cladribine anticancer drug

Using molecular models for pristine (NT) and COOH (FNT) functionalized carbon nanotube, ten noncovalent configurations and four mechanisms of covalent functionalization of NT and FNT with cladribine anticancer drug (CDA) were studied. Quantum molecular descriptors, free energies of solvation and binding energies of noncovalent interactions were investigated in H2O and DMF solvents and gas phase. The calculation of binding energies confirmed the energetic stability of all CDA/NT and CDA/FNT configurations. The free energies of solvation show that NT and FNT solubility increases in all drug-nanotube configurations which is a main factor for its applicability in the drug delivery. Quantum molecular descriptors of drug such as global hardness and HOMO-LUMO energy gap are higher than those of drug-nanotube complexes, showing the reactivity of the drug increases. The AIM analysis for the most stable configuration (CDA/FNT2) demonstrated that the intermolecular hydrogen bonding plays a main role in this system. For the covalent functionalization COOH (FNT) and COCl (NTCOCl) functionalized carbon nanotubes were considered. Cladribine may bond to FNT and NTCOCl through NH2 and OH groups. The activation parameters of all pathways were calculated, indicating the activation energies and Gibbs free energies related to FNT mechanisms are higher than those of NTCOCl mechanisms.

Electrochemical functionalization of single-walled carbon nanotubes with amine-terminated dendrimers encapsulating Pt nanoparticles: Toward facile field-effect transistor-based sensing platforms

We present a method for functionalization of single-walled carbon nanotubes (CNTs) with amine-terminated dendrimers encapsulating catalytic nanoparticles, and demonstrate the feasibility of functionalized CNTs as efficient field-effect transistor (FET)-sensing platforms. As a model system, we synthesized Pt dendrimer-encapsulated nanoparticles (DENs) using amine-terminated sixth-generation poly(amidoamine) dendrimers, and functionalized CNT-based FET channels with Pt DENs via electro-oxidative grafting of the terminal amines of dendrimers onto the surface of CNTs. We also demonstrated spatially-controlled surface functionalization of CNTs and subsequent modification of the functionalized CNT-based FET channels with glutamate oxidases for efficient FET-based sensing of glutamates. Our approach could facilitate the functionalization of CNTs with a variety of catalytic nanoparticles and biologically active materials, enabling the development of sensitive and selective FET-based sensor devices.

THE EFFECT OF NANOADDITIVES ON THE HYDRATION OF GYPSUM BINDING AGENTS

The results of investigation of hydration processes of gypsum with carbon nanomodifiers are presented in the article. Gypsum modification by multilamellar carbon nanotube (CNT) results in the improvement of its compression strength. Experiments proved that at the nanotubes content of 0,18 %, strength improvement by up to 30 % is observed. Chemical functionalization of carbon nanotube surface facilitates the reduction of the sedimentation effect inherent to the nanoparticles, enables more uniform nanostructure dispersion throughout the modified material volume and provides the chemical interaction between nanotubes and the substance matrix. Quantum-chemical analysis methods confirm that the interaction of calcium sulfate dihydrate molecule with the dihydrate -like surface is the chemical process. The improvement of CNT-containing gypsum composite strength is due to the accelerated process of calcium sulfate dihydrate crystallization at the graphene surface. Therefore, it may be assumed that CNTs act as “crystallization nuclei” in the gypsum composite. The analysis of the microstructure of gypsum composition samples showed that without the modifying additive, loose structure of the gypsum samples is formed with a significant number of pores.It may be assumed that nanodispersed CNT additives act as “crystallization nuclei” on the surface of which calcium sulfate matrix structuring occurs with the improvement of the gypsum composition structural characteristics. This is due to the fact that during growth, crystals partly penetrate into each other and form three-dimensional network permeating and incorporating the entire gypsum stone into a body.

CNT–CdSe QDs nanocomposites: synthesis and photoluminescence studies

In this study, synthesis of carbon nanotube (CNT)–CdSe Quantum dots (QDs) nanocomposites has been investigated. CdSe QDs were synthesized via hydrothermal process. The chemical tendency of CNT and QDS was increased by precipitation after surface functionalization of CNTs (by carboxylated groups) and CdSe QDs (by silane groups), separately. The structure of nanocomposites was amorphous with a little amount of nanocrystalline cubic CdSe. The Fourier-transform infrared (FTIR) spectra and Raman spectrum revealed the strong chemical tendency of linkage between CNTs and QDs after functionalization on the surface of them. The morphology of nanocomposites depended on the QDs concentration and changed from aggregates of CNTs to the marvelous decoration of quantum dots on the ropes of CNTs. Transmission electron microscope (TEM) and atomic force microscope (AFM) images confirmed the adorable coatings of CNTs with CdSe QDs. The nanocomposites emitted in blue–green region with a maximum peak at 490 nm under the exposure of Ultraviolet (UV) light. Below 50 wt% QDs, the emission was quenched completely.