Hydroxyl-functionalized Carbon Nanotubes Research Articles

Effect of functionalization on the adsorption performance of carbon nanotube as a drug delivery system for imatinib: molecular simulation study

In this study, efficiency of functionalized carbon nanotube as a potential delivery system for imatinib anti-cancer drug was investigated. Accordingly, carboxyl and hydroxyl functionalized carbon nanotube were inspected as a notable candidate for the carriage of this drug in aqueous media. For this purpose, possible interactions of imatinib with pure and functionalized carbon nanotube were considered in aqueous media. The compounds were optimized in gas phase using density functional calculations. Solvation free energies and association free energies of the optimized structures were then studied by Monte Carlo simulation and perturbation method in water environment. Outcomes of quantum mechanical calculations presented that pure and functionalized carbon nanotubes can act as imatinib drug adsorbents in gas phase. However, results of association free energy calculations in aqueous solution indicated that only carboxyl and hydroxyl functionalized carbon nanotubes could interact with imatinib. Monte Carlo simulation results revealed that electrostatic interactions play a vital role in the intermolecular interaction energies after binding of drug and nanotube in aqueous solution. Computed solvation free energies in water showed that the interactions with functionalized carbon nanotubes significantly enhance the solubility of imatinib, which could improve its in vivo bioavailability.

Thermal properties and mechanical behavior of functionalized carbon nanotube-filled polypropylene composites using molecular dynamics simulation

Polypropylene (PP) is widely recognized as an environmentally friendly material for cable insulation due to its good insulation performance and environmental friendliness. One common method for enhancing the overall performance of PP is the addition of nanoparticles. To analyze the influence of different functionalized multi-walled carbon nanotubes (MWCNT) fillers on the properties of PP/MWCNT composite materials from a microscale perspective, molecular dynamics is used to construct pure PP models and models filled with untreated carbon nanotubes (UFCNT), amino-functionalized carbon nanotubes (AFCNT), carboxyl-functionalized carbon nanotubes (CFCNT), and hydroxyl-functionalized carbon nanotubes (HFCNT) (functionalized MWCNT with 4 or 8 functional groups grafted onto them). The simulation results indicate that the doping of nanotubes can effectively enhance the thermodynamic properties of PP. Among them, PP/CFCNT-8 exhibits the most significant improvement in melting temperature and mechanical properties, with an increase in melting temperature of 88.85 K and a 184.52 % increase in Young's modulus. The melting temperature of PP/HFCNT-8 is second only to PP/CFCNT-8, with an increase of 82.59 K. The results indicate that the thermodynamic properties of PP nanocomposites filled with functionalized MWCNT are improved with the grafting rate. The filling of functionalized MWCNT alters the microscale properties of PP composites, with a significant decrease in root mean square displacement (RMSD), and improvement in free volume fraction (FFV) as well as interfacial binding energy, which can better maintain the electrical properties of PP insulation materials. Applying functionalized carbon nanotubes to filled PP can significantly increase the electrical insulation properties of PP cable materials, which provides meaningful guidance for adopting polypropylene cable insulation materials.

Intrinsically Nonswellable Multifunctional Hydrogel with Dynamic Nanoconfinement Networks for Robust Tissue-Adaptable Bioelectronics.

Developing bioelectronics that retains their long-term functionalities in the human body during daily activities is a current critical issue. To accomplish this, robust tissue adaptability and biointerfacing of bioelectronics should be achieved. Hydrogels have emerged as promising materials for bioelectronics that can softly adapt to and interface with tissues. However, hydrogels lack toughness, requisite electrical properties, and fabrication methodologies. Additionally, the water-swellable property of hydrogels weakens their mechanical properties. In this work, an intrinsically nonswellable multifunctional hydrogel exhibiting tissue-like moduli ranging from 10 to 100kPa, toughness (400-873 J m-3 ), stretchability (≈1000% strain), and rapid self-healing ability (within 5min), is developed. The incorporation of carboxyl- and hydroxyl-functionalized carbon nanotubes (fCNTs) ensures high conductivity of the hydrogel (≈40Sm-1 ), which can be maintained and recovered even after stretching or rupture. After a simple chemical modification, the hydrogel shows tissue-adhesive properties (≈50kPa) against the target tissues. Moreover, the hydrogel can be 3D printed with a high resolution (≈100µm) through heat treatment owing to its shear-thinning capacity, endowing it with fabrication versatility. The hydrogel is successfully applied to underwater electromyography (EMG) detection and ex vivo bladder expansion monitoring, demonstrating its potential for practical bioelectronics.

Molecular dynamics investigation of the mechanical properties and fracture behaviour of hydroxyl-functionalised carbon and silicon carbide nanotubes-reinforced polymer nanocomposites

ABSTRACT The tensile properties and fracture mechanism of hydroxyl-functionalized silicon carbide nanotubes (O-fSiCNTs) inserted into polymer matrices are explored and the outcomes are compared to results for the hydroxyl-functionalized carbon nanotubes (O-fCNTs) incorporated in similar matrices. The molecular dynamics (MD) method is used and the simulations are based on the notion of representative volume elements (RVEs). The incorporation of chemisorbed nanotubes in polymers has a profound effect on the enhancement of their mechanical properties. The O-fSiCNTs inside the polyethylene (PE) and polypropylene (PP) (O-fSiCNTs/PE and O-fSiCNTs/PP) possess lower Young’s modulus, maximum stress, and strain energy as compared to the O-fCNTs/PE and O-fCNTs/PP. The zigzag O-fSiCNTs/polymer experiences lower bearable maximum strains in response to imposed loads in comparison with the O-fCNTs/polymer which is opposite to what occurs in the armchair O-fSiCNTs and O-fCNTs/polymer. The more the functionalization degree is, the weaker the structure is and its stiffness, tensile strength, tolerable strain before fracture, and ability to absorption of internal energy decline. Not only are the zigzag O-fSiCNTs/polymer stiffer than the armchair O-fSiCNTs/polymer in every percent of functionalization, but also as compared to the armchair ones, they show a lower decrease in the variation of Young’s modulus with increasing the functionalization percentage.

Proton conduction and electrochemical enzyme-free glucose sensitive sensing based on a newly constructed Co-MOF and its composite with hydroxyl carbon nanotubes

It is a great challenge to construct MOFs-based materials with low activation energy for potential applications in proton exchange membrane fuel cells (PEMFCs) as well as fine electrocatalytic glucose sensing performance. Herein, we report a novel 2D Co-MOF {[Co(iip)(bbbm)(H2O)2]·2DMF·2H2O}n obtained through the assembly between Co(II) and 5-iodoisophthalic acid (H2iip) in the presence of the hydrophobic ligand 1,1-(1,4-butanediyl)bis-1H-benzimidazole (bbbm). Its composite with hydroxyl-functionalized carbon nanotubes (Co-MOF@CNTs) was fabricated under ambient conditions. The (8) hydrogen-bonded ring exists in Co-MOF. Both the composite membranes of Co-MOF and Co-MOF@CNTs with nafion exhibit interesting proton-conductive behavior, which are even superior to that of nafion in aqueous medium with the same pH values. Among them, the proton conductivity of the composite Co-MOF@CNTs/nafion membrane is expectedly superior to that of the composite Co-MOF/nafion membrane. Remarkably, the composite Co-MOF@CNTs/nafion membrane exhibited an exceptionally low activation energy (Ea = 0.082 eV, pH = 3), which is among one of the lowest Ea values for the reported novel proton-conducting polymeric materials/composites, resulting in almost unchanged conductivity over the measured temperature range, revealing its potential application in PEMFCs. Moreover, both the pristine Co-MOF and its composite Co-MOF@CNTs could serve as electrocatalytic materials toward glucose oxidation. The Co-MOF@CNTs electrode exhibits expectedly more rapid and sensitive electrochemical glucose sensing with relatively lower determination limit (LOD = 3 μM) and larger detection range (0.01–5 mM) in comparison with that of the pristine Co-MOF (LOD = 0.021 mM, 0.01–2.40 mM).

On the adsorption of volatile organic compounds on hydroxyl-functionalized carbon nanotubes in aqueous solution

Volatile organic compounds (VOCs) are among the primary concerns due to their practical threatening on living environment and human health. This work aims at examining the physical adsorption behavior of four representative VOC species on hydroxyl-functionalized CNTs in terms of molecular dynamics simulations. Simulation results indicate that the adsorption affinities of these four VOC species follow the order of toluene > ether > acetone > methanol for both the unfunctionalized and hydroxyl-functionalized CNTs. This adsorption preference is endorsed by the binding energy calculations based on the umbrella sampling algorithm. The surface modifications due to the introduction of hydroxyl groups affect both the adsorption mechanism and equilibrium configuration. The hydrogen-bond network near the adsorption region is rebuilt for stabilizing the adsorption kinetics. Compared to the dominant van der Waals interaction, the electrostatic interaction between the charged hydroxyl groups and the VOC molecules are found to be much less significant. With the increase of hydroxyl concentration, the adsorption affinity decays for all four VOC species. This conclusion is confirmed by both the binding free energies and the number of successfully adsorbed VOC molecules. The fundamental mechanism is due to the reduction of the originally hydrophobic area of CNTs surface and the additional bonding competition from water molecules. This work presents a molecular insight on the interaction between VOC molecules and hydroxyl-functionalized CNTs in aqueous solution. It can also benefit the development and design of smart filtration devices of VOC molecules for their early removal in aqueous solutions.

Ultrasonically Induced Covalent Grafts of Cisplatin Loaded Ginger Oil Nanoemulsion System on the Surface of OH-SWCNT’S for Anticancer Studies and Biomedical Applications - A Novel Approach in Nanotechnology

Hydroxyl functionalized Carbon nanotubes are the low-dimensional sp2 carbon nanomaterial’s exhibiting many distinctive physical and chemical characteristics which are intriguing in a broad variety of fields including nanomedicine. Their latent applications in Nanoelectronics, biosensors, bimolecular recognition devices, and molecular transporters, as well as cancer treatment and diagnosis, are still fascinating. For the first time, Hydroxyl functionalized SWCNT(OH-SWCNT) was developed as a delivery platform for Cisplatin loaded Ginger (o/w) nanoemulsion in this work, which is known for its prominent role as targeted drug delivery systems in the field of nanomedicine application and cancer therapy. OH-functionalized SWCNTs were first modified with anionic surfactant (tween80) to facilitate the covalent connection of a Cisplatin cored GE-NE(Cisp/GE-NE) on surface charge interaction. The total Cis/Ge-ne loading on the resulting nanotubes was l mol/mg where the release was observed under both room temperature and at 37oc. the successful grafting of Cisp-Ge/Ne on OH-SWCNTs at each step was confirmed qualitatively by (Fourier-transform infrared spectroscopy and UV-visible spectroscope). Morphological studies carried by Transmission electron microscopy (TEM) have shown the hollow long tubular structure occupied with the Cisplatin cored Ginger oil nanoemulsion (Cisp/Ge-ne). Cis/Ge-ne-OH-SWCNTs were preserved after modification at different temperatures given high stability at 37o C. OH-SWCNT-Cis/Ge-Ne showed significant toxicity towards HEK(Normal Kidney cell lines) and AGS(gastric cancer cell lines) whereas no significant cytotoxicity on normal Kidney cell lines (HEK) was observed on different dilution factor equal to or below 2mg/ml. The Cis/Ge-Ne attached to hydroxyl functionalized SWCNTs is a novel and effective drug delivery method that might be employed alone or in combination with other treatments for various nanomedicine applications and also for dual-targeted therapy in cancer.

Atomistic Insights on the Adsorption of Long-Chain Undecane Molecules on Hydroxyl-Functionalized Carbon Nanotubes

Atomistic Insights on the Adsorption of Long-Chain Undecane Molecules on Hydroxyl-Functionalized Carbon Nanotubes

On the Adsorption of Volatile Organic Compounds on Hydroxyl-Functionalized Carbon Nanotubes in Aqueous Solution

On the Adsorption of Volatile Organic Compounds on Hydroxyl-Functionalized Carbon Nanotubes in Aqueous Solution

Effect of hydroxylated carbon nanotubes on the thermal and electrical properties of derived epoxy composite materials

Carbon nanotubes are efficient thermal conductors and exhibit unique electrical properties. What is not entirely clear, however, is how to effectively transfer the carbon nanotube's unique attributes exhibited at the nanoscale to the macroscale. The primary focus of this study was upon identifying the main causes that can lead to improvements in thermal and electrical conductivity for polymers with the use of the reinforcement material. The effects of carbon nanotube type and structure on the physical properties of derived epoxy composite materials were investigated experimentally to better understand the applied physics of thermal and electrical transport at the nanoscale. The thermal and electrical properties of the composite materials were also investigated theoretically with various models. The results indicated that the hydroxyl functionalization of carbon nanotubes can be an effective means to enhance the thermal and electrical properties of the derived composite materials. Hydroxyl-functionalized carbon nanotubes exhibit considerably improved thermal and electrical conductivity in applications including polymer composites. Hydroxylated carbon nanotubes can achieve at least one or more of the following objectives: improves the solubility and dispersibility of the carbon nanotubes in polymer materials into which the carbon nanotubes are to be mixed, reduces contact resistance between carbon nanotubes incorporated into the polymer material by drawing the carbon nanotubes closer together, and provides a conductive bridge between carbon nanotubes to reduce the electrical contact resistance there between. Multi-walled carbon nanotubes can reduce the probability of inelastic phonon scattering due to grain boundaries, thereby yielding a higher effective thermal conductivity for derived polymer composite materials.

Binding Capacity and Selectivity of Functionalized and Un-functionalized Carbon Nanotubes for Development of Copper-Detecting Printable Sensor.

Carbon nanotubes (CNTs) have unique properties which can be modified through surface functionalization. The ability of several functionalized and un-functionalized CNTs to bind copper was investigated as a first step toward developing a printable CNT-based sensor to detect copper in aqueous systems. Binding capacity and specificity were shown to vary by functionalization and vendor. CNTs from two vendors were tested, and the equilibrium binding data was fitted using two isotherm models. Calculated qmax (mg/g) values indicated one vendor's carboxyl-functionalized CNTs had the greatest binding capacity (94-115mg/g), while other carboxyl-functionalized CNTs and amine-functionalized CNTs had similar capacities to un-functionalized CNTs (15-30mg/g). Hydroxyl-functionalized CNTs had the lowest copper binding capacity (7-8mg/g) of the CNTs tested. Freundlich isotherms showed no obvious trends in binding affinity, but suggested that binding was primarily due to chemisorption. Variations in CNT size, functionalization percentage, and purity could explain, partially, the observed adsorption differences.

Understanding the first half-ALD cycle of the ZnO growth on hydroxyl functionalized carbon nanotubes.

We report the adsorption of diethylzinc on hydroxyl functionalized carbon nanotubes. This study intends to understand, at the atomic level, the initial stages of ZnO formation by atomic layer deposition. Our study begins with the molecule physisorbed on the nanotube (initial state of the reaction). The final state of this reaction is when the H atom of the hydroxyl group is abstracted and migrates to one ethyl group of diethylzinc. The oxygen atom relaxes towards the nanotube and forms a strong bond with a carbon atom, while the remaining part of the molecule forms a bond with the H atom and physisorbs on top of the ZnO unit. The probability for this process to happen is very high since the energy to desorb the diethylzinc molecule is higher than the energy needed to break down the O-H bond. Non-covalent interactions and charge density distributions are plotted to confirm the break-down, formation of bonds, and repulsion during the reaction pathway.

Effective Trapping of Lithium Polysulfides Using a Functionalized Carbon Nanotube-Coated Separator for Lithium-Sulfur Cells with Enhanced Cycling Stability.

The critical issues that hinder the practical applications of lithium-sulfur batteries, such as dissolution and migration of lithium polysulfides, poor electronic conductivity of sulfur and its discharge products, and low loading of sulfur, have been addressed by designing a functional separator modified using hydroxyl-functionalized carbon nanotubes (CNTOH). Density functional theory calculations and experimental results demonstrate that the hydroxyl groups in the CNTOH provoked strong interaction with lithium polysulfides and resulted in effective trapping of lithium polysulfides within the sulfur cathode side. The reduction in migration of lithium polysulfides to the lithium anode resulted in enhanced stability of the lithium electrode. The conductive nature of CNTOH also aided to efficiently reutilize the adsorbed reaction intermediates for subsequent cycling. As a result, the lithium-sulfur cell assembled with a functional separator exhibited a high initial discharge capacity of 1056 mAh g-1 (corresponding to an areal capacity of 3.2 mAh cm-2) with a capacity fading rate of 0.11% per cycle over 400 cycles at 0.5 C rate.

Enhanced Lithium-Sulfur Battery By Amine-Functionalized Cathode and Kinetic Study of Polysulfides Dissolution

Lithium-Sulfur battery is very attractive due to its high energy density of 2500 Wh/kg or 2800 Wh/L. The low cost of Sulfur ($0.02/g) provides a significant driving force to obtain a commercial Li-S battery. But their practical use is still hindered by several issues including capacity fading, short lifespan, and low efficiency. The dissolution of long-chain lithium polysulfides (Li2Sx, 2 < x < 8) (LiPS) into the electrolyte and the shuttling of polysulfides between cathode and anode have been generally considered responsible for the capacity degradation. A variety of methods have been applied to prevent the dissolution of LiPS, most of which focus on physical trapping by using carbon matrix as barrier materials. However, the effect of barrier materials is kinetics; LiPS physically trapped in carbon host will eventually leach into the electrolyte. Also, the nonpolar carbon matrix will facilitate the detachment of LiPS, which is highly polar, from the cathode, resulting in loss of active materials. Thus thermal sequestering of LiPS via chemical binding and a polar cathode surface is desired. Herein, we report a facile approach towards high-performance sulfur-carbon cathodes by stabilizing LiPS on amine-functionalized cathode. Specifically, Polyethylenimine (PEI) is chosen for the reason that it possesses a large amount of amine groups within a molecular. PEI is attached to the cathode by reacting with hydroxyl functionalized carbon nanotubes (Figure 1). The strong affinity of LiPS to PEI-functionalized CNT is verified by DFT calculation, showing high binding energy of 1.23 eV, while it is 0.34eV between LiPS and graphene and 0.83eV between LiPS and PVDF. The interaction is also confirmed by FTIR, XPS, and other characterization techniques. With the merits of CNT such as good conductivity and robust mechanical properties, the nanocomposite of amine-functionalized CNT and sulfur exhibits stable cycling performance with high capacities (Figure 1). Furthermore, the kinetic study of polysulfides dissolution is carefully carried out. The dissolution constant k is determined by the method described in Figure 2. k is obtained for cathodes with various compositions: (1) Li2S4 without PEI; (2) Li2S4 with PEI; (3) Li2S9 without PEI; (4) Li2S9 with PEI. By comparing dissolution constants in each case, the much stronger affinity of PEI with the LiPS can be observed with smaller k. Also, the higher solubility and dissolution rate are found with increasing chain length of LiPS. The equilibrium concentration (ceq) of LiPS in the electrolyte is found, where LiPS has equal chemical potential in the electrolyte and cathode. This guides us in adding LiPS with concentration of ceqto the electrolyte when designing Li-S batteries. In this case, LiPS will not leach into the electrolyte since there is no driving force in the condition of equilibrium. The battery performance will be presented in the talk. In summary, the new method takes advantage of the numerous amine groups in PEI and the strong affinity with LiPS to realize a high performance Li-S battery. The systematical kinetic study also reveals the working mechanism and paves the way to further rational design of Li-S battery. Figure 1

Facile preparation of octadecyl monoliths with incorporated carbon nanotubes and neutral monoliths with coated carbon nanotubes stationary phases for HPLC of small and large molecules by hydrophobic and π–π interactions

Two approaches for incorporating carbon nanotubes into monolithic columns for HPLC are described in this report. They pertain to the investigation of carbon nanotubes either (i) as entities to modulate solute retention on monolithic columns bearing well defined retentive ligands or (ii) as entities that constitute the stationary phase responsible for solute retention and separation. Approach (i) involved the incorporation of carbon nanotubes into octadecyl monolithic columns while approach (ii) concerns the preparation and evaluation of an ideal monolithic support and coating it with carbon nanotubes to yield a real “carbon nanotube stationary phase” for the HPLC separation of a wide range of solutes. First, an octadecyl monolithic column based on the in situ polymerization of octadecyl acrylate and trimethylolpropane trimethacrylate was optimized for use in HPLC separations of small and large solutes (e.g., proteins). To further modulate the retention and separation of proteins, small amounts of carbon nanotubes were incorporated into the octadecyl monolith column. In approach (ii), an inert, relatively polar monolith based on the in situ polymerization of glyceryl monomethacrylate (GMM) and ethylene glycol dimethacrylate (EDMA) proved to be the most suitable support for the preparation of “carbon nanotube stationary phase”. This carbon nanotube “coated” monolith proved useful in the HPLC separation of a wide range of small solutes including enantiomers. In approach (ii), a more homogeneous incorporation of carbon nanotubes into the diol monolithic columns (i.e., GMM/EDMA) was achieved when hydroxyl functionalized carbon nanotubes were incorporated into the GMM/EDMA monolithic support. In addition, high power sonication for a short time enhanced further the homogeneity of the monolith incorporated with nanotubes. In all cases, nonpolar and π interactions were responsible for solute retention on the monolith incorporated carbon nanotubes.

Interfacial improvement of carbon fiber/epoxy composites using a simple process for depositing commercially functionalized carbon nanotubes on the fibers

An aqueous suspension deposition method was used to coat the sized carbon fibers T700SC and T300B with commercially carboxylic acid-functionalized and hydroxyl-functionalized carbon nanotubes (CNTs). The CNTs on the fiber surfaces were expected to improve the interfacial strength between the fibers and the epoxy. The factors affecting the deposition, especially the fiber sizing, were studied. According to single fiber-composite fragmentation tests, the deposition process results in improved fiber/matrix interfacial adhesion. Using carboxylic acid-functionalized CNTs, the interfacial shear strength was increased 43% for the T700SC composite and 12% for the T300B composite. The relationship between surface functional groups of the CNTs and the interfacial improvement was discussed. The interfacial reinforcing mechanism was explored by analyzing the surface morphology of the carbon fibers, the wettability between the carbon fibers and the epoxy resin, the chemical bonding between the fiber sizing and the CNTs, and fractographic observation of cross-sections of the composites. Results indicate that interfacial friction, chemical bonding and resin toughening are responsible for the interfacial improvement of nanostructured carbon fiber/epoxy composites. The mechanical properties of the CNT-deposited composite laminate were further measured to confirm the effectiveness of this strategy.