Functionalization Of Multi-walled Carbon Nanotubes Research Articles

Microwave-Assisted Functionalization of Multi-Walled Carbon Nanotubes for Biosensor and Drug Delivery Applications

Microwave-assisted synthetic methods have emerged as a popular technique for surface modification and the functionalization of multi-walled carbon nanotubes (MWCNTs) for diverse drug delivery applications. Microwave-induced functionalization of MWCNTs provides a high functionalization and requires less time than conventional techniques. Microwave methods are simple, fast, and effective for the covalent and noncovalent conjugation of MWCNTs with various biomolecules and polymers. The present review focuses on the synthetic and drug delivery applications of microwave irradiation techniques (MITs) for the functionalization of MWCNTs, using amino acids and other molecular frameworks containing amino groups, vitamins, proteins, epoxy moieties, metal nanoparticles, and polymers.

Preparation and Statistical In-vitro Evaluation of Covalent Functionalized Multi Walled Carbon Nanotube 5-Fluorouracil Conjugates

In 21st century, carcinoma is predicted to be a remarkable health problem. The condition of the cancer patients will be critical when it comes to its remedy by chemotherapy using artificial anticancer molecules with various chemo side effects. In the field of nanotechnology, the nanomaterials are rapidly developing. Nanomaterials become admirable and necessary in lot of areas of human interest because of their exclusive size - dependent properties, chemical reactivity, conductivity, and enlarged strength. Carbon nanotubes (CNT) are referred to as nanomaterials. In this present world of medical research and the bio sensing technology has the capability to transform the CNT in the field of efficient medicine delivery, biosensor strategies for ailment treatment and for the health tracking. Our present work is an strive to probe the loading and release of 5- Fluorouracil from Multi Walled Carbon Nanotubes (MWCNTs) to cancer tissues. MWCNTs were subjected to covalent functionalization by using the strong acids, the oxidised MWCNTs are obtained in covalent functionalization process. Through this operation, carboxy (-COOH) groups are set up at the open sides (tips) and at the defects on the sidewalls of MWCNTs and then covalent functionalized MWCNTs were loaded with 5- Fluorouracil to prepare covalent functionalized MWCNTs-5-Flourouracil conjugate. Covalent functionalized MWCNTs-5-Flourouracil conjugate were subjected for SEM studies, TEM studies, particle size, zeta potential, drug entrapment efficiency and in vitro drug release. The release of drug shows longer than 40 h from covalent functionalized MWCNTs-5-Flourouracil conjugate and thus to manage the release of drug in controlled manner. The present research work presents esteemed, novel, and easy to prepare formulation of MWCNTs with superior drug entrapment efficiency with increased hydrophilic property of MWCNTs, and thus increases the bioavailability at selected site with narrow systemic toxicity.

Durability & mechanical properties of functionalized multiwalled carbon nanotube incorporated pozzolana portland cement composite

The current study examined the impact of Functional Multiwalled Carbon Nanotubes (FMWCNTs) incorporated in Pozzolana Portland Cement (PPC) mortar on mechanical and durability characteristics. The mechanical and durability properties of PPC mortar have been found to be remarkable in the presence nanomaterials. The results indicate that 0.0015% FMWCNTs by weight percent of cement (PPC1) had the maximum improvement in mechanical and durability performance over the 90-day curing periods. In PPC1, compressive and tensile strengths improved by 8.74% and 20.61%, respectively, as compared to the control sample (PPC-C). When the calcium silicate hydrate (CSH) gel is dense, it improves the electrical resistance of PPC mortar for PPC1. Water absorption was found to be reduced by 29.31% and 78.71% in PPC1 samples at 28- and 90-day curing ages, respectively, when compared to PPC-C. This decrease can be attributed to the influence of FMWCNTs in PPC mortar on void reduction via the bridging and filler effects. After an aggressive acid attack, the compressive strength of PPC mortar was found to be 43.63% for PPC3 as compared to PPC-C at 28 days of curing. The investigation showed that the nano-engineered mortar displayed the lowest amount of mass loss and the least reduction in mechanical strength as compared to PPC-C. The characterizations of Powdered X-ray Diffraction (PXRD) and Fourier Transform Infrared Spectroscopy (FT-IR) have been employed for the finding of significant bonding within the PPC mortar.

Detection of Protamine Based on Competitive Adsorption on the Surface of Functionalized Multi Walled Carbon Nanotubes

Detection of Protamine Based on Competitive Adsorption on the Surface of Functionalized Multi Walled Carbon Nanotubes

The Influence of MWCNTs Amounts and PVP Aqueous Solutions on the Properties of PVA/PVP/MWCNTs Nanocomposite Membranes

In this article, the surface functionalization of multi-walled carbon nanotubes (MWCNTs) is performed using a tris(2-aminoethyl)amine (TAA) to generate functional moieties (−NH2) on the surface. The functionalized MWCNTs (f-MWCNTs) are incorporated in the blend polymers of polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) to fabricate a nanocomposite membrane via phase inversion process, which are named PVA/PVP/f-MWCNT. The nanocomposite membranes are characterized by a field emission scanning electron microscopy (FE-SEM), fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), water contact angle. The FE-SEM images show that the PVA/PVP/f-MWCNTs nanocomposite membrane consisting 0.01 g of f-MWCNTs exhibits a uniform morphology and good dispersion of f-MWCNTs. The X-ray results demonstrate that the incorporation of f-MWCNTs has successfully changed the structural properties of the nanocomposite membranes. TGA analysis indicates that the PVA/PVP/f-MWCNTs nanocomposite membranes exhibit higher thermal properties than the pristine PVA/PVP blend membrane. The weight loss within 420 °C–550 °C is increased from 34.62 to 55.66% with increasing the PVP content from 1 wt% to 8 wt%, respectively. The contact angle measurements indicate that addition of f-MWCNTs to the PVA/PVP blend membrane has improved hydrophilic properties.

Enhancement of mechanical properties of matrix by functionalized Multi-Wall Carbon Nanotubes (MWCNT) in composite material

In present era, Multi-Wall Carbon Nanotubes (MWCNTs) added composites are used to enhance the mechanical properties which are mostly used in aerospace and defense applications. This paper is about fabrication and testing of four different epoxy matrix laminates. Amine and Carboxylic Functionalized CNTs, un-Treated-Multiwall carbon nanotubes (MWCNTs) and Carbon fiber/epoxy, having variation of 0.5 wt% of multiwall carbon nanotubes (MWCNTs), which is fabricated by using vacuum bagging Technique with carbon fiber as reinforcement. The composites are tested for flexural and inter-linear shear strength (ILSS) and Tensile as per ASTM standards D790, D2344, and D3039. From the test results and analysis, it is found that Carboxylic Functionalized CNTs added epoxy resin has higher flexural and inter-laminar shear strength (ILSS) when compared with other CNTs and in terms of Tensile strength perspective Amine Functionalized CNTs showed better results.

Low-temperature magnetoresistance of functionalized multiwall carbon nanotubes

Temperature and magnetic field dependencies of resistance for functionalized multiwall carbon nanotubes (MWCNTs) have been studied. The measurements were carried out in the temperature range T = 4.2–200 K. It is shown that in magnetic fields up to B = 9 T, the conductivity behavior for the functionalized MWCNTs sample can be described in terms of charge carriers weak localization and interaction phenomena. We show that the contribution to the functionalized MWCNTs conductivity due to the weak localization effect exceeds the quantum correction due to the effect of the charge carriers interaction for all the temperatures and in the entire range of the applied magnetic fields except for the magnetic fields above B = 6.5 T at T = 5 K. Within the terms of the specified models, we estimate the value of the Fermi energy and determine the explicit form of the temperature dependence of the phase relaxation time for the wave function. We show that for the functionalized MWCNTs sample, the phase relaxation time for the wave function has a less pronounced temperature dependence, and its Fermi energy is more shifted to the valence band compared to non-functionalized MWCNTs. The charge carriers’ interaction constant at different temperatures can also be estimated from our experiments.

Hybridized sulfated-carboxymethyl cellulose/MWNT nanocomposite as highly selective electrochemical probe for trace detection of arsenic in real environmental samples.

A highly selective and ultra-sensitive electrochemical sensing probe was proposed by combining sulfated-carboxymethyl cellulose (CMC-S) and a functionalized-multiwalled carbon nanotube (f-MWNT) nano-composite with high conductivity and durability. The CMC-S/MWNT nanocomposite was impregnated on a glassy carbon electrode (GCE) to construct the non-enzymatic and mediator-free electrochemical sensing probe for trace detection of As(iii) ions. The fabricated CMC-S/MWNT nanocomposite was characterized by FTIR, SEM, TEM, and XPS. Under the optimized experimental conditions, the sensor exhibited the lowest detection limit of 0.024 nM, a high sensitivity (69.93 μA nM-1 cm-2) with a good linear relationship in the range of 0.2-90 nM As(iii) concentration. The sensor demonstrated strong repeatability, with the current response continuing at 84.52% after 28 days of use, in addition to good selectivity for the determination of As(iii). Additionally, with recovery ranging from 97.2% to 107.2%, the sensor demonstrated comparable sensing capability in tap water, sewage water, and mixed fruit juice. The electrochemical sensor for detecting trace levels of As(iii) in actual samples is anticipated to be produced by this effort and is expected to possess great selectivity, good stability, and sensitivity.

An ultra-sensitive uric acid second generation biosensor based on chemical immobilization of uricase on functionalized multiwall carbon nanotube grafted palm oil fiber in the presence of a ferrocene mediator.

In this work, palm oil fiber (POF) grafted functionalized multiwall carbon nanotube (FMWCNT) decorated ferrocene (Fc) has been drop coated on a platinum electrode (Pt), in which uricase (UOx) has been chemically immobilized for sensitive and selective biosensing of uric acid (UA). Through the use of EDC/NHS, a stable bioelectrode (UOx/Fc/FMWCNT-POF/Pt) was obtained and characterized by FTIR/ATRIR, XRD, Raman, EA/EDX, TGA, SEM, TEM, CV, EIS, CA, and DPV. Results from DPV showed the rapid response of the developed bioelectrode towards UA (0.185 V) with high sensitivity (41.14 μA mM-1) and good limit of detection (19 μM) in the linear range 10-1000 μM. The low value of Michaelis-Menten constant (km = 31.364 μM) shows high affinity of the UA towards the enzyme at the electrode surface. The developed biosensor demonstrates good reproducibility, repeatability, and stability with a deviation of less than 2.5%, and was successfully applied for human blood sample analysis. The CA study revealed a fast response time (2 s) of the sensor. The work has pioneered a new addition to the class of tailorable chemical species for biosensor development and proven to be a promising new tool for point of care testing (POCT) applications.

Fragmentation and release of pristine and functionalized carbon nanotubes from epoxy-nanocomposites during accelerated weathering.

There is an increasing volume of nano-enabled materials in the market. Once composites containing nano-additives are disposed of, weathering could deteriorate their structures, releasing nanoparticles and risking exposure of humans and aquatic organisms. Composite degradation due to environmental aging continues, including structural deterioration resulting in cracking, fragmentation, and release of microplastics and nano-additives to the environment. This research aims to study the degradation and release of initially embedded nanomaterials (NMs) from composites and their toxicity. The molecular interaction of carbon nanotube (CNT)/polymer composites is critical for modifying the polymer properties. This study investigated the interactions of functional multiwalled carbon nanotube (MWCNT) composites which affect their release during accelerated weathering processes. Different epoxy-MWCNT composites were prepared by filling a polymer with pure MWCNTs and MWCNTs functionalized with acid () and amine () groups. The physical and chemical changes of aged composites were characterized by gravimetric analysis, contact angle measurements, FTIR, SEM, and laser confocal microscopy. A loss of hydrophobicity was observed for composite surfaces long before surface cracks materialized. Released polymer fragments and nanoparticles were analyzed in wash water using TEM, FTIR and Raman spectroscopy. The environmental risks for long-term use of CNT-polymer composites and the influence of fillers on the extent of chemical photodegradation depended on the combination of polymer and fillers. If nanoparticles are released from the matrix, the high surface-to-volume ratio and reactivity of NMs make them highly dynamic in environmental systems. Exposure to these released NMs could negatively affect human health and the environment. This study provides fragmentation and CNT particle release data that could describe how molecular-level interactions between functionalized CNTs and epoxy polymers affect the aging and release of CNTs. A toxicity assessment based on a reactive oxygen species (ROS) formation assay and MTS assay for cell viability and activity of the released polymer and CNT fragments and leachate showed moderate levels of cytotoxicity of released materials as compared to pristine epoxy plates.

Supercritical processing of thermally stable multiwalled carbon nanotube/boron nitride nanohybrids with synergistically improved electrical conductivity

A novel method of processing of thermally stable nanohybrids (NHs) with synergistically improved electrical conductivity (σDC) has been developed in supercritical carbon dioxide (SCC). Processing of NHs was executed through dispersion of selected weight fractions (wt%) of hexagonal boron nitride (h-BN) into carboxylate functional multiwalled carbon nanotube (c-MWCNT) at 1200 psi, 90 ± 1°C over 5 hr in SCC. Formation of NHs was ascertained through diverse analytical methods. Scanning electron microscopy coupled with energy dispersive spectra, elemental mapping and X-ray diffraction analysis reveals deposition of h-BN over the surface of c-MWCNT. NHs derived at 5 wt% of h-BN has shown reduced optical band gap (Eg, 3.34 eV) with 41 % increase in crystallite size. Working electrodes (WEs) derived from NHs has rendered increasing trend of DC conductivity (mS/cm) with concentration of h-BN up to 5 wt% at 100 V. WEs involving h-BN (5 wt%) has shown enhanced DC conductivity (0.93) followed by c-MWCNT (0.63) and h-BN (0.41) at 100 V. Present investigation delivers a clean, dry and environmentally benign method of processing of NHs suitable for development of inexpensive WEs for potential applications in hydrogen storage, electrocatalysis and sensors.

Engineered nanostructure fibrous cell-laden biointerfaces integrating Fe3O4/SrO2-fMWCNTs induce osteogenesis and anti-bacterial effect

Improving biomechanical and biochemical properties of tissue-engineered scaffolds akin to those of native stem-cell niches can effectively regenerate tissues. Bio-ceramic nanomaterials integrated porous scaffolds can be employed to promote bone cell proliferation and contribute to their translational value. Here, we successfully developed highly conductive fibrous scaffolds of polyurethane (PU) integrating Fe3O4/SrO2 nanoparticles (NPs) in association with functionalized multiwall carbon nanotubes (fMWCNTs). The engineered scaffold of PU-Fe3O4/SrO2-fMWCNTs with 0.4 wt.% of NPs showed synergistic effects on physicochemical and biological performances. The porous scaffold showed superior interfacial biocompatibility, antibacterial properties, and load-bearing ability. Results of in vitro, including ALP activity, collagen-I, and ARS staining of MC3T3-E1 cells confirmed that the scaffold provided a favorable microenvironment with a prominent effect on the growth, proliferation, and differentiation of MC3T3-E1 cells. Furthermore, the up-regulated osteogenic protein expression of MC3T3-E1 cells was studied by qRT-PCR, and Western blotting and found the osteoblastic activity accelerated due to the enhanced mineralization of PU-Fe3O4/SrO2-fMWCNTs (0.4 wt.%). Together, our findings suggest these scaffolds with improved cell-interface compatibility exhibit osteoinductivity that could become a novel nanomaterial-based tissue construct as a therapeutic strategy for bone cell regeneration and bone defect repair.

In vitro comparative cytotoxic assessment of pristine and carboxylic functionalized multiwalled carbon nanotubes on LN18 cells.

Multiwalled carbon nanotubes (MWCNTs) have been used in biomedical applications due to their ability to enter the cells. Carboxylic functionalization of MWCNT (MWCNT-COOH) is used to mitigate the toxicity of MWCNTs. Our study focuses on comparing the toxicity of MWCNT and MWCNT-COOH on the neuronal cells, LN18. Concentrations of 5, 10, 20, and 40 µg ml-1 were used for the study, and cytotoxicity was determined at 0, 1, 3, 6, 12, 24, and 48 h of incubation. Cell viability was assessed by Trypan Blue, MTT, and Live dead cell assays, and the oxidative stress produced was determined by reactive oxygen species (ROS) and Lipid peroxidation assays. MWCNT-COOH showed higher cell viability than MWCNT for 20 and 40 µg ml-1 at 24 and 48 h. This was also visually observed in the live dead cell imaging. However, at 48 h, the morphology of the cells appeared more stretched for all the concentrations of MWCNT and MWCNT-COOH in comparison to the control. A significant amount of ROS production can also be observed at the same concentration and time. Viability and oxidative stress results together revealed that MWCNT-COOH is less toxic when compared to MWCNT at longer incubation periods and higher concentrations. However, otherwise, the effect of both are comparable. A concentration of 5-10 µg ml-1 is ideal while using MWCNT and MWCNT-COOH as the toxicity is negligible. These findings can further be extended to various functionalizations of MWCNT for wider applications.

Mechanically robust and highly elastic thermally induced shape memory polyurethane based composites for smart and sustainable robotic applications

AbstractIn the present study, polyurethane (PU) was prepared using a pre‐polymer (two‐shot) process with a novel phloroglucinol chain extender. PU nanocomposite was prepared by incorporating acid‐FMWCNTs in pristine‐PU. Polystyrene (PS) was functionalized with the nitro group through our previously reported method. The ternary blend composites (PU/PS‐NO2/FMWNTs) were prepared using acid functionalized multiwall carbon nanotubes (FMWCNTs) for enhanced properties and selectivity. Nitro‐functionalized‐PS/PU composite properties were compared with pristine‐PU and its blend composite. The structure of the pre‐designed PU polymer and its composites were confirmed by the FTIR and the degree of crystallinity and amorphous state was determined with XRD analysis. Excellent thermal stabilities were confirmed through a TGA thermogram with an increase in the loading amount of FMWCNTs. Excellent tensile strength 59.2 ± 2.6 MPa with 0.1 g loading amount of FMWCNTs with enhanced flexibilities was achieved. The significant change in surface morphologies and porosity suggested enhanced interaction (physical and chain entanglement) of FMWCNTs and nitrated‐PS with PU chain as the loading amount of filler increased. The resulted porous spongy cluster (as seen in SEM images) provides efficient shape recovery strain with excellent flexibility to the composite material without compromising repeatability. Almost 100% shape recovery was observed for all samples with repeated recoveries. The recovery time of PU nanocomposite observed is shorter than neat polyurethane and PU/PS‐NO2 blends because of their better conductive nature but causes brittleness, which can easily initiate a crack in the sample compared to a blended sample.

High performance of asymmetric coin cells designed using optimized weight percentage of multiwalled carbon nanotubes in Ni/Co-MOFs nanocomposites

• 20% of F-MWCNTs in Ni/Co-MOF was better than other weight % of F-MWCNTs. • Ni/Co-MOF/20% F-MWCNTs exhibited a high Cs of 1779 F/g at 2 mV/s & 890 F/g at 2.5 A/g. • The coin cell with Ni/Co-MOF/20% F-MWCNTs//AC offered ED-56 Wh/kg & PD-11 kW/kg. • Six-coin cells in series were used to power three red coloured LEDs for 3 minutes. Nanocomposites (NC-X) of Ni/Co-MOFs with varying weight % of functionalized multiwalled carbon nanotubes (F-MWCNTs) were synthesized by solvothermal method. Physicochemical properties of NC-X were analyzed by different analytical techniques. Further, electrochemical studies were made to comprehend the effect of weight % of F-MWCNTs in the nanocomposites for high-performance supercapacitors. 20 weight % of F-MWCNTs in the nanocomposite exhibited higher supercapacitance performance (890 F/g at 2.5 A/g) than other nanocomposites. The fabricated asymmetric coin cell (ASC) offered high energy and power densities of 56.25 Wh/kg and 11.9 kW/kg respectively with 20,000 cycle stability at 25 A/g (1 M KOH). The ASC also retained 72% capacitance with 100% coulombic efficiency at 20,000 th cycle. Six ASC of each cell with operating potential window of 1.8 V were utilized in powering three red light emitting diodes (LEDs-12 V) connected in series. Thus, demonstrating the practical application of ASCs to power LEDs for 3 minutes.

Development of a Toxic Lead Ionic Sensor Using Carboxyl-Functionalized MWCNTs in Real Water Sample Analyses.

Functional multiwall carbon nanotubes (f-MWCNTs) are of significant interest due to their dispersion ability in the aqueous phase and potential application in environmental, nanotechnology, and biological fields. Herein, we functionalized MWCNTs by a simple acid treatment under ultra-sonification, which represented a terminal or side-functional improvement for the fabrication of a toxic lead ion sensor. The f-MWCNTs were characterized in detail by XRD, Raman, XPS, BET, UV/vis, FTIR, and FESEM-coupled XEDS techniques. The analytical performance of the f-MWCNTs was studied for the selective detection of toxic lead ions by inductively coupled plasma-optical emission spectrometry (ICP-OES). The selectivity of the f-MWCNTs was evaluated using several metal ions such as Cd2+, Co2+, Cr3+, Cu2+, Fe3+, Ni2+, Pb2+, and Zn2+ ions. Lastly, the newly designed ionic sensor was successfully employed to selectively detect lead ions in several environmental water samples with reasonable results. This approach introduced a new technique for the selective detection of heavy metal ions using functional carbon nanotubes with ICP-OES for the safety of environmental and healthcare fields on a broad scale.

Multi-walled carbon nanotubes as a platform for Immunoglobulin G attachment

Nanomaterials have been extensively used in different applications due to their peculiar characteristics and nanoscale dimensions. Among nanoparticles, carbon-based nanomaterials are becoming highly attractive for biomedical applications such as diagnosis, tissue engineering, drug delivery, and biosensing. The conjugation of carbon-based nanomaterials with antibodies combines the properties of these materials with the specific and selective recognition ability of the antibodies to antigens. The present work proposes a process intensification approach for immunoglobulin G (IgG present in rabbit serum) attachment on multi-walled carbon nanotubes (MWCNTs) in a single step. The effect of several parameters, namely MWCNTs external diameter, rabbit serum concentration, MWCNTs functionalization and pH value, on the IgG attachment yield was evaluated. The dilution of rabbit serum decreased other protein attachment, namely rabbit serum albumin (RSA), while increasing the IgG yield to 100%. The interaction mechanisms between IgG and MWCNTs were evaluated at pH 5.0 to 8.0. The protonation of IgG amino acids indicates that N-term are the most reactive amino acids in the antibody structure. The identification of the N-term reactivity at pH 8.0 allows to indicate a possible orientation of the antibody over the MWCNTs surface, described as “end-on”. Since the amount of RSA attached to MWNT decreased with the increase in serum dilution, the IgG orientation and amine activity was not affected. This orientation demonstrates that the IgG attachment over the surface of the MWCNTs could be an effective strategy to maintain the antigen recognition by the antibody, and to be used for biomedical applications.

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.

A Study on the Effects of Potassium Permanganate on the Functionalization of Multi-Walled Carbon Nanotubes

In this work, multi-walled carbon nanotubes (MWCNTs) are functionalized by a wet chemical oxidation method using a mixture of potassium permanganate (KMnO4) and sulfuric acid (H2SO4) at 70 °C, for 12 h. The effects of various KMnO4 amounts on the functionalization of MWCNTs are studied and reported. The surface morphologies, structural properties, dispersion and thermal stability of the MWCNTs are characterized using a field emission scanning electron microscope (FE-SEM), Raman spectroscopy, UV-visible spectroscopy (UV–vis), thermal gravimetric analysis (TGA). The FE-SEM images display some surface roughness, cutting and open ends of functionalized MWCNTs (f-MWCNTs). The TGA curves of f-MWCNTs indicate a weight loss between 150 °C and 350 °C, which is attributed to the loss of carboxyl groups on the MWCNTs surface and the weight loss is increased when KMnO4 mass is increased. The highest weight loss value of 22.23% is recorded for the oxidation treatment with a mixture of 5 M H2SO4 and 200 mg KMnO4. UV–vis measurements indicate that the f-MWCNTs are highly dispersed in the aquoues solution in comparision to the pristine MWCNTs (p-MWCNTs). And f-MWCNTs with higher functionalization degree show better dispersibility. This study provides a great prospect of effective method to cut, end-open, functionalize and disperse MWCNTs.

The mechanism and sorption kinetic analysis of hydrogen storage at room temperature using acid functionalized carbon nanotubes

The present work investigates the effect of acid functionalization of multiwalled carbon nanotubes (MWCNTs) on the physisorption based mechanism of hydrogen storage at room temperature. For this purpose, a suite of functionalized CNT samples is synthesized and subjected to a comprehensive range of material characterization techniques and hydrogen storage measurements. Nitric acid (HNO3) and the mixture of sulphuric acid and nitric acid (H2SO4:HNO3) are used for the synthesis at oxidation temperatures of 80 °C and 100 °C. Electron microscopy and X-ray photoelectron spectroscopy results reveal that acid functionalization causes major alternation in the physicochemical properties of the CNTs due to the varied concentration of oxygen functional groups. Particularly, the H2SO4:HNO3 functionalized sample at 100 °C is found to have the highest interlayer spacing, oxygen to carbon ratio (26.09 at. %), defect content, and specific surface area (215.3 m2/g). These features collectively contribute to substantially improved hydrogen storage properties, including a ∼150% increase in the hydrogen storage capacity at 298 K and 50 bar. Furthermore, kinetic analysis shows that the desorption follows a multiple diffusion process which is sensitive to the oxygen functional groups and structural defects, hence reducing the rate of desorption; whereas the adsorption is controlled by a more rapid, three-dimensional diffusion process.