Effects of noncovalently functionalized multiwalled carbon nanotube with hyperbranched polyesters on mechanical properties of epoxy composites

In order to improve the dispersibility and interface properties of multi-walled carbon nanotubes (MWCNTs) in epoxy resin (EP), aromatic hyperbranched polyesters with terminal carboxyl (HBP) and aromatic hyperbranched polyesters with terminal amino groups (HBPN) were used for noncovalent functionalization of MWCNTs. Epoxy composites reinforced by different types of MWCNT were prepared. The effects of noncovalent functionalization of MWCNTs on the dispersibility, wettability, interface properties and mechanical properties of epoxy composites were investigated. The results show that the dispersibility and wettability of MWCNTs are significantly improved after noncovalent functionalization. A large number of terminal primary amines (NH₂) on noncovalently functionalized MWCNT with HBPN (HBPN-MWCNT) form covalent bonds with EP matrix, and thus the interfacial adhesion is enhanced significantly, resulting in high load transfer efficiency and substantial increase in mechanical properties. The interface with covalent bonding formed between the flexible hyperbranched polyester layer on the surface of HBPN-MWCNT and the EP matrix promotes plastic deformation of the surrounding EP matrix. The toughening mechanisms of HBPN-MWCNT are MWCNT pull-out and a large amount of plastic deformation of the surrounding EP matrix.     

Soluble carbon nanotubes

Carbon nanotubes have attracted great interdisciplinary interest because of their unique structure and properties. However, carbon-nanotube research is challenged by several problems, such as: i) mass production of material, ii) control of length, diameter, and chirality, and iii) manipulation for use in diverse technological fields. Issues regarding the synthesis and purification as well as the functionalization and solubilization of carbon nanotubes are relevant topics in this rapidly growing field. In this paper, covalent and noncovalent approaches to functionalized and solubilized nanotubes are examined in detail, with particular emphasis on the change of properties that accompany the chemical modification.     

Density functional and molecular docking studies towards investigating the role of single-wall carbon nanotubes as nanocarrier for loading and delivery of pyrazinamide antitubercular drug onto pncA protein

The potential biomedical application of carbon nanotubes (CNTs) pertinent to drug delivery is highly manifested considering the remarkable electronic and structural properties exhibited by CNT. To simulate the interaction of nanomaterials with biomolecular systems, we have performed density functional calculations on the interaction of pyrazinamide (PZA) drug with functionalized single-wall CNT (fSWCNT) as a function of nanotube chirality and length using two different approaches of covalent functionalization, followed by docking simulation of fSWCNT with pncA protein. The functionalization of pristine SWCNT facilitates in enhancing the reactivity of the nanotubes and formation of such type of nanotube-drug conjugate is thermodynamically feasible. Docking studies predict the plausible binding mechanism and suggests that PZA loaded fSWCNT facilitates in the target specific binding of PZA within the protein following a lock and key mechanism. Interestingly, no major structural deformation in the protein was observed after binding with CNT and the interaction between ligand and receptor is mainly hydrophobic in nature. We anticipate that these findings may provide new routes towards the drug delivery mechanism by CNTs with long term practical implications in tuberculosis chemotherapy.     

Selective polycarboxylation of semiconducting single-walled carbon nanotubes by reductive sidewall functionalization

The efficient and controllable synthesis, the detailed characterization, and the chemical postfunctionalization of polycarboxylated single-walled carbon nanotubes SWCNT(COOH)(n) are reported. This innovative covalent sidewall functionalization method is characterized by (a) the preservation of the integrity of the entire σ-framework of SWCNTs; (b) the possibility of achieving very high degrees of addition; (c) control of the functionalization degrees by the variation of the reaction conditions (reaction time, ultrasonic treatment, pressure); (d) the identification of conditions for the selective functionalization of semiconducting carbon nanotubes, leaving unfunctionalized metallic tubes behind; (e) the proof that the introduced carboxylic acid functionalities can serve as versatile anchor points for the coupling to functional molecules; and (f) the application of a subsequent thermal degradation step of the functionalized semiconducting tubes leaving behind intact metallic SWCNTs. Functional derivatives have been characterized in detail by means of Raman, UV-vis/nIR, IR, and fluorescence spectroscopy as well as by thermogravimetric analysis combined with mass spectrometry, atomic force microscopy, and zeta-potential measurements.     

共价功能化碳纳米管的应用研究进展

本文跟踪碳纳米管的功能化研究进展,对共价功能化碳纳米管在材料领域,如复合材料、催化剂载体、电子器件、光学材料、及生物医学中的应用进行了综述.     

碳纳米管在药物和基因转运领域的研究进展

当前,国内外的许多研究小组都致力于开发出新型有效的药物和基因转运系统,用于改善多种治疗因子的药理学作用并降低其毒性。在纳米材料这一类中,碳纳米管（Carbon Nanotubes, CNTs）正逐步引起人们的关注。功能化的CNTs的两个关键优势在于它具有很强的细胞穿透能力和较低的细胞毒性,使其在药物和基因转运领域中的应用成为可能。CNTs可通过形成稳定的共价键或形成以非共价键为基础的超分子结合物来运载肽类、蛋白质、核酸和药物等活性分子,并将其运送至特定的组织、器官中以表达特殊的生物学功能。针对这一研究热点,本文综述了近几年国内外关于碳纳米管在药物和基因转运领域中的应用进展,并探讨了其毒性,以期为这一领域中的研究工作者提供参考。     

Lysinated Multiwalled Carbon Nanotubes with Carbohydrate Ligands as an Effective Nanocarrier for Targeted Doxorubicin Delivery to Breast Cancer Cells

Multiwalled carbon nanotubes (MWCNTs) are elongated, hollow cylindrical nanotubes made of sp2 carbon. MWCNTs have attracted significant attention in the area of drug delivery due to their high drug-loading capacity and large surface area. Furthermore, they can be linked to bioactive ligands molecules via covalent and noncovalent bonds that allow for the targeted delivery of anticancer drugs such as doxorubicin. The majority of methodologies reported for the functionalization of MWCNTs for drug delivery are quite complex and use expensive linkers and ligands. In the present study, we report a simple, cost-effective approach for functionalizing MWCNTs with the carbohydrate ligands, galactose (GA), mannose (MA) and lactose (LA), using lysine as a linker. The doxorubicin (Dox)-loaded functionalized MWCNTs were characterized using FT-IR, NMR, Raman, XRD and FE-SEM. The drug–loaded MWCNTs were evaluated for drug loading, drug release and cell toxicity in vitro, in breast cancer cells. The results indicated that the carbohydrate-modified lysinated MWCNTs had greater Dox loading capacity, compared to carboxylated MWCNTs (COOHMWCNTs) and lysinated MWCNTs (LyMWCNTs). In vitro drug release experiments indicated that the carbohydrate functionalized LyMWCNTs had higher Dox release at pH 5.0, compared to the physiological pH of 7.4, over 120 h, indicating that they are suitable candidates for targeting the tumor microenvironment as a result of their sustained release profile of Dox. Doxorubicin-loaded galactosylated MWCNTs (Dox-GAMWCNTs) and doxorubicin loaded mannosylated MWCNTs (Dox-MAMWCNTs) had greater anticancer efficacy and cellular uptake, compared to doxorubicin–loaded lactosylated MWCNTs (Dox-LAMWCNTs) and pure Dox, in MDA-MB231 and MCF7 breast cancer cells. However, neither the ligand conjugated multiwall blank carbon nanotubes (GAMWCNTs, MAMWCNTs and LAMWCNTs) nor the lysinated multiwalled blank carbon nanotubes produced significant toxicity in the normal cells. Our results suggest that sugar-tethered multiwalled carbon nanotubes, especially the galactosylated (Dox-GAMWCNTs) and mannosylated (Dox-MAMWCNTs) formulations, may be used to improve the targeted delivery of anticancer drugs to breast cancer cells.     

Efficient Chemical Modification of Carbon Nanotubes with Metallacarboranes

As‐produced single‐walled carbon nanotubes (SWCNTs) tend to aggregate in bundles due to π–π interactions. Several approaches are nowadays available to debundle, at least partially, the nanotubes through surface modification by both covalent and noncovalent approaches. Herein, we explore different strategies to afford an efficient covalent functionalization of SWCNTs with cobaltabisdicarbollide anions. Aberration‐corrected HRTEM analysis reveals the presence of metallacarboranes along the walls of the SWCNTs. This new family of materials presents an outstanding water dispersibility that facilitates its processability for potential applications.     

Coating Multi-walled Carbon Nanotubes with Uniform Silica Shells:Independent of Surface Chemistry

A facile and general method was described to coat six types of multi-walled carbon nanotubes, functionalized by either noncovalent or covalent way, with smooth silica shells. 3-Aminopropyltriethoxysilane(APTES) and pH value play important roles in the coating process and the thickness of silica shell could be controlled by the added amount of silicon alkoxides. After the removal of multi-walled carbon nanotubes by calcination, the silica nanotubes were successfully prepared.     

Electrochemical Characterization of the Interaction of Multiwalled Carbon Nanotubes with Doxorubicin

It has been suggested that multiwalled carbon nanotubes (MWCNTs) interacting with pharmaceutics may be introduced into the body as nanocarriers. To deliver the anticancer drugs, covalent or noncovalent functionalization of MWCNTs is required. In this study, the influence of oxidation on MWCNTs in the interaction with chemotherapeutic drug, doxorubicin, was characterized. The binding of doxorubicin with MWCNTs decreased rapidly with the increasing oxidation period with sulfuric acid. However, with nitric acid, the interaction increased initially and slowly decreased with time. The best results were obtained for sulfuric and nitric acid following 1 and 3?h of oxidation, respectively. The results show that sulfuric acid provided more favorable interaction for MWCNTs with doxorubicin than nitric acid.     

Pyrenyl Carbon Nanotubes for Covalent Bilirubin Oxidase Biocathode Design: Should the Nanotubes be Carboxylated?

Understanding the characteristics of nanomaterials in the context of electrode designs for bio‐electrocatalysis is an emerging research direction. Applications for fuel cells, batteries, and biosensors are directly benefited. The objective of this study is to understand the influence of unfunctionalized multiwalled carbon nanotubes (MWNT) in comparison to carboxylated nanotubes (MWNT?COOH) for pi‐pi stacking with 1‐pyrenebutyric acid (Py) and covalent immobilization of bilirubin oxidase (BOD) enzyme toward the resulting oxygen reduction currents. We designed pyrolytic graphite‐edge electrodes modified with MWNT/Py, MWNT?COOH/Py, or only MWNT?COOH for carbodiimide activation and BOD immobilization. The relative increase in surface ?COOH groups as we move from MWNT to MWNT/Py to MWNT?COOH/Py modification is voltammetrically estimated. Although the MWNT?COOH/Py displayed the highest relative amount of surface ?COOH groups, the oxygen reduction current was the largest for the BOD‐immobilized MWNT/Py electrode than others. Results indicate that unfunctionalized MWNT is the optimal choice for pi‐pi stacking with pyrene linkers and covalent BOD immobilization as biocathode for energy devices. Favorable hydrophobic MWNT surface to interact more closely with the electron‐receiving T1 Cu site of BOD, as opposed to the relatively polar and more defective MWNT?COOH material due to functionalization, is suggested to be one of the underlying factors for the observed electrocatalytic trend.     

Chemical functionalization of carbon nanotubes by carboxyl groups on stone-wales defects: a density functional theory study

Chemical functionalization of carbon nanotubes with Stone-Wales (SW) defects by carboxyl (COOH) groups is investigated by density functional calculations. Due to the localized donor states induced by the SW defect, the binding of the COOH group with the defective carbon nanotube is stronger than that with the perfect one. A quasi-tetrahedral bonding configuration of carbon atoms, indicating sp3 hybrid bonding, is formed in the adsorption site. The charge distribution analysis shows that, in comparison with benzoic acid, the localized or delocalized pi states on the nanotube would affect the polarities of chemical bonds of the COOH group without losing the acidity. Furthermore, it is found that the double-adsorption system (two COOH groups are respectively adsorbed on two individual carbon atoms of the SW defect) is more energetically favorable than the monoadsorption one. The adsorption of COOH groups leads to a significant change of the electronic states around the Fermi level, which is advantageous for the electrical conductivity. The functionalization by introducing functional groups on the topological defects provides a pathway for applications of carbon nanotubes in chemical sensors and nanobioelectronics.     

Heightened Integration of POM‐based Metal–Organic Frameworks with Functionalized Single‐Walled Carbon Nanotubes for Superior Energy Storage

To increase the conductivity of polyoxometalate‐based metal–organic frameworks (POMOFs) and promote their applications in the field of energy storage, herein, a simple approach was employed to improve their overall electrochemical performances by introducing a functionalized single‐walled carbon nanotubes (SWNT‐COOH). A new POMOF compound, [Cu₁₈(trz)₁₂Cl₃(H₂O)₂][PW₁₂O₄₀] (CuPW), was successfully synthesized, then the size‐matched functionalized SWNT–COOH was introduced to fabricate CuPW/SWNT–COOH composite (PMNT–COOH) by employing a simple sonication‐driven periodic functionalization strategy. When the PMNT–COOH nanocomposite was used as the anode material for Lithium‐ion batteries (LIBs), PMNT–COOH( 3 ) (CuPWNC:SWNT‐COOH=3:1) showed superior behavior of energy storage, a high reversible capacity of 885 mA h g^?1 up to a cycle life of 170 cycles. The electrochemical results indicate that the uniform packing of SWNT–COOH provided a favored contact between the electrolyte and the electrode, resulting in enhanced specific capacity during lithium insertion/extraction process. This fabrication of PMNT–COOH nanocomposite opens new avenues for the design and synthesis of new generation electrode materials for LIBs.     

DFT study of SiO2 nanoparticles as a drug delivery system: structural and mechanistic aspects

Structural Chemistry - Adsorption and reaction mechanisms for the noncovalent and covalent functionalization of SiO2 nanoparticle (SiNP) with gemcitabine (GEM) anticancer drug have been...     

Azide-functionalization of carbon nanotubes by electrochemical oxidation of N3- in situ

Azide-functionalization of single-walled carbon nanotubes （SWCNTs） was achieved by electrochemical oxidation of N3 in situ. The functionalized nanotubes were characterized in details by single internal reflection infrared spectroscopy （ATR-FTIR） and thermogravimetic analysis （TGA/MS）. The results revealed that a covalent C-N bond had formed and this might provide an effective method for the preparation of azide-functionalized materials, especially carbon materials. The degree of functionaliza- tion was measured by X-ray photoelectron spectroscopy （XPS）.     

Functionalization of Single‐Walled Carbon Nanotubes

Through chemical functionalization of single‐walled carbon nanotubes, the prerequisites for possible applications of such nanostructures are established. The derivatized tubes differ from the crude materials in their good solubility, which enables both a more extensive characterization and subsequent chemical reactivity. Current derivatization methods include defect and covalent sidewall functionalization, as well as noncovalent exo‐ and endohedral functionalization. In this way, for example, a range of nanotubes can be prepared: with sidewall substituents, wrapped with polymers, or with guest molecules included. The current state of the literature is presented in this Minireview.     

Encapsulation of carbon nanotubes by self-assembling peptide amphiphiles

We demonstrate the dispersion and noncovalent functionalization of carbon nanotubes in water using peptide amphiphiles each consisting of a short hydrophobic alkyl tail coupled to a more hydrophilic peptide sequence. The assembly of peptide amphiphile molecules on the surfaces of carbon nanotubes adds biofunctionality to these one-dimensional conductors and simultaneously eliminates the hydrophobic nanotube-water interface, thus dispersing them in the aqueous medium. This should occur without the degradation of their structural, electronic, and optical properties caused by covalent functionalization and without the need for specific peptide sequences designed to bind with nanotube surfaces. The encapsulation by peptide amphiphiles is confirmed using transmission electron microscopy and optical absorbance spectroscopy and may have significant future applications in biosensing or medicine.