Effects Of Single-walled Carbon Nanotubes Research Articles

The Effect of Single Walled Carbon Nanotubes on Conductivity and Thermal Properties of Glass Fiber Reinforced Composites

Abstract This paper reports on a comprehensive study of the effect of single-walled carbon nanotube (SWCNT) on the alternating current (AC) conductivity, thermal and morphological properties of the unsaturated polyester based glass fiber reinforced polymer composite (GFRPC). AC conductivity measurements were carried out using the impedance spectrum and thermal measurements were carried out using differential scanning calorimetry (DSC) at a temperature range of 24-900 °C and heating rates of 20 °C/min. Impedance results showed that the conductivity behavior in the nanotube-loaded composite laminate obeys a Jonscher-type mechanism. At low frequencies, the conductivity value remains almost constant for the doped material and takes the value of 10-5 S/cm. It is observed that the AC conductivity starts to increase after the critical frequency value of approximately 103 Hz and increases up to 10-2 S/cm due to hopping and tunneling mechanisms caused by space charge polarization accumulated in the local regions at high frequencies. The pure material with an insulating nature also exhibited a typical insulating behavior. Thermal testing showed that nanotube reinforcement increases thermal conductivity in three different directions. DSC thermocurves analysis also revealed that the addition of carbon nanotubes increased the glass transition temperature of the material from 180°C to 190°C. The scaling and fractal analysis methods were also applied to obtain hetero morphological structure of materials. The fractal analysis results indicated that carbon nanotube doping to the standard sample increases the coating rates, scalability and heterogeneity of the solid phase surface of the sample. The coating rates of composite surfaces were calculated as 45% and 36%, respectively. Morphology analysis revealed that the probability of finding surface particles for the nanotube-doped sample decreased compared to the undoped sample, but the fractal dimension value increased. While this value was 1.83 in the pure sample, it increased to 1.92 in the nanotube material.

Influence of SWCNT on shielding and tensile properties of polyurethane nanocomposites

ABSTRACT The effect of single-walled carbon nanotubes (SWCNTs) as fillers in polyurethane matrix composites on the efficiency of attenuating electromagnetic waves in the X-band region (8–12 GHz) was studied in the current work. To meet the present-day challenges, the composites were tested using a tensile system. The inclusion of SWCNT in the polyurethane matrix proved the enhancement of electromagnetic interference shielding performance along with the improved mechanical properties. The composites were characterised by FTIR and FESEM. The dielectric properties were investigated in X-band frequencies. The shielding performance of the samples was found to be 28 dB for 1 wt% filler at 10 GHz. The effect of CNT on the mechanical performance of polyurethane composites was studied. The maximum tensile strength achieved was 2.87 MPa for 3 wt% CNT. The results showed that the synthesised sample materials found more shielding applications with favourable tensile properties.

Nanofiller effect of single-walled carbon nanotubes to elongate, toughen and acceleratingly produce ionic liquid dry-jet wet spun cellulose fibre

A cellulose is produced from renewable natural resources, and the regenerated fibres have been widely utilized, e.g., a tyre cord fabric. However, the production of viscose Rayon is inevitable to use environmentally burdened chemicals like CS2. We propose an eco-friendly cellulose fibre created with a recyclable ionic liquid, further mechanically toughened using a nanofiller. A synergetic architecture composed of minute amount of 0.1 wt% single-walled carbon nanotubes (CNT) and cellulose matrix achieves the increased (34 %) elongation and the retained tensile strength, thus creating the enhanced (39 %) toughness. Such a unique enhancement is different from diverse fillers generally known to decrease the elongation in return for the increased strength. To fully draw the reinforcement, controlling the bundled CNT particle size analogous to cellulose microfibril is essential. Moreover, the CNTs are advantageous to a high throughput, and maximum take-up rate of the wet-spun fibre is boosted (30 %).

Synergistic effects of single-walled carbon nanotube and carbon fiber on performance of conductive mortar

Single-walled carbon nanotube (SWCNT) and carbon fiber (CF) have been demonstrated to be conducive to an improved electrical conductivity of cement-based composites. However, there have been few studies on the possible hybrid use of SWCNT and CF to further promote the electrical conductivity and perhaps also other performance attributes. In this study, a trial to utilise both SWCNT and CF to produce conductive mortar was launched. A series of 20 mortar mixes featuring varying water-to-cement ratios, SWCNT contents and CF contents were tested to reveal their combined effects on fresh workability, mechanical strength, dimensional stability, electrical conductivity and microstructure. Test results exhibited that the co-addition of SWCNT and CF derived adverse effect on workability, but remarkable beneficial effects on strength, dimensional stability and electrical conductivity, and more interestingly, some combinations of SWCNT and CF showed synergistic effects. From the microscopic morphology, the agglomeration of SWCNT is an important causation for the decline in strength and dimensional stability of mortar. Finally, some mix proportions suitable for conductive mortars are proposed.

Promoted photocatalytic performances over Ti3+-B co-doped TiO2/BN with high carrier transfer and absorption capabilities driven by SWCNT addition

Recently, carbon nanotubes have been widely used as supporting materials for semiconductor photocatalysts due to their excellent electron and mass transportation. Herein, we prepared a novel SWCNT-decorated Ti3+-B co-doped TiO2/BN (STBN) photocatalyst with the presence of single-walled carbon nanotubes (SWCNTs) during the hybridization of BN and TiB2. The effects of SWCNTs on the structural and photocatalytic properties were investigated. Adding SWCNTs enables excellent multifunctional photocatalytic performances (N2 fixation, H2 production, and MO degradation) compared with the TBN synthesized in the previous study. Introducing SWCNTs reduces the transfer resistance and makes the photogenerated carriers transfer more efficiently, thereby improving photocatalytic activity. More defect sites provide extra adsorption sites for reactants and photogenerated electrons, significantly improving the system's photocatalytic activity. The enhanced photocatalytic mechanism of SWCNT-decorated hybrid catalysts was proposed at last.

Dielectric and conductivity properties of liquid crystal MBBA doped with single-walled carbon nanotubes

The effect of single-walled carbon nanotubes (SWCNTs) on the dielectric and conductivity properties of nematic liquid crystal 4-methoxybenzylidene-40-butylaniline (MBBA) has been studied. It was shown that the additive of SWCNTs with concentration of 0.3% leads to an increase in the order parameter of MBBA. Observation under the polarization microscope has shown that the presence of SWCNTs in MBBA increases the clearing temperature from 46.3°C to 47.4°C. This change can be explained by the improvement of the liquid crystalline orientation order. As a result, the transition to a complete disordering of the molecules (transition to an isotropic state) requires more heat energy, correspondingly, more temperature. The dielectric and conductivity measurements have showed that the longitudinal component of the dielectric permittivity decreases while the transverse component increases as well as dielectric anisotropy. The percolation effect promotes to the dominance of hopping electron conductivity over ionic conductivity, leading to an increase in electric conductivity.

Functionalized SWCNTs@Ag–TiO2 nanocomposites induce ROS-mediated apoptosis and autophagy in liver cancer cells

Abstract Hybrid nanomaterials with unique physiochemical properties have received a lot of attention, making them attractive for application in different fields like cancer treatment. This study was designed to investigate the combined effects of single-walled carbon nanotubes (SWCNTs) hybridized with silver titanium dioxide composite (SWCNTs@Ag–TiO2). Transmission electron microscopy and field emission scanning electron microscopy images demonstrated the accumulation of SWCNTs with Ag–TiO2 due to an increased main grain size with functionalization to 40 nm. The D and G bands in SWCNTs @Ag–TiO2 shifted to 1,366 and 1,534 cm−1, respectively. SWCNTs@Ag-TiO2 were assessed for their cytotoxicity and autophagy induction in liver cancer cells (Hep-G2) using the lactate dehydrogenase assay, MTT assay, and flow cytometry methods. The results showed that SWCNTs and SWCNTs@Ag–TiO2 exhibited strong anti-cancer activity in vitro against Hep-G2 cells by inducing apoptosis and autophagy in liver cancer cells via controlling the AKT and JNK mitogen-activated protein kinase pathways. The results show that SWCNTs and SWCNTs coated with silver/titanium dioxide (SWCNTs@Ag–TiO2) reduce the cells’ viability and proliferation. It was shown that an excessive amount of reactive oxygen species was a crucial mediator of both the cell death caused by SWCNTs and the cell death caused by SWCNTs combined with Ag–TiO2. Based on these findings, it appears that SWCNTs and SWCNTs@Ag–TiO2 have the potential to be developed as nanotherapeutics for the treatment of liver cancer cells.

Synthesis of TiC(1-x)–ZrCx (x=0.2) composite by FAST-SPS-FCT technology, effect of SWCNTs and nano-WC additions on structural properties: Application for ballistic protection

This paper describes the SWCNTs and nano WC when were introduced into TiC(1-x)– ZrCx with (x=2) nano-composite into ceramics to improve the fracture toughness (KIC) and hardeness (Hv). TiC–ZrC, TiC–ZrC–single walled carbon nanotubes (SWCNTs) (3 mass %) and TiC–ZrC–SWCNTs (3 mass %) - tungestun nanocarbide (NWC) (20 mass %) nano-composites were prepared by vacuum sintering FAST-SPS-FCT technology at the temperatures in the range of 1700–1800 °C for 400 s under pressure of 50 Mpa. Microtructural properties were investigated by X-ray diffraction and energy-dispersive spectrometry in addition scanning electron miroscopy. The investigations shows that the phase separation of the as-sintered (Ti, Zr) C into two phases: TiC-rich (Ti, Zr) C (dark) and ZrC-rich (Zr, Ti) C (bright) indicating that the as-sintered (Ti, Zr) C was thoroughly decomposed into two solid phases after sintering. The effect of nanostructures of SWCNTs and NWC is already illustrated. X-ray diffraction and energy-dispersive spectrometry results indicate that bright grains are (Zr, Ti) C solid solution. The relative density increases with the addition of SWCNTs and nano-WC content.
 Fully dense TiC-ZrC, TiC–ZrC-SWCNTs and TiC–ZrC-CNTs-NWC nanocomposites with a relative density of more than 98 % were obtained. The Vickers hardness (HV) and fracture toughness (KIC), of TiC-based nano-composites with SWCNTs and NWC will be performed in the near future. In addition, ballistic performance (the properties of shock resistance) ; thermo-mechanical modelling in-situ FAST-SPS-FCT cycle, also will be evaluated using the Rosenberg model and compared with the experimental results in order to better understand the shock behavior of nano-composites that to be applied for body armor

Buckling analysis of nanocomposite beams based on refined beam theory by considering the Agglomeration effect of CNTs

The present work deals with buckling load behavior of nanocomposite beams by considering the agglomeration effect of single-walled carbon nanotubes (CNTs) and different patterns CNTs in polymeric matrix. The material properties of nanocomposite beams are estimated using the Eshelby–Mori– Tanaka approach based on an equivalent fiber. The equations of motion are derived based on refined beam strain gradient theory, employing Hamilton’s principle and using Differential Quadrature Finite Element Method (DQFEM) derived from the differential quadrature method (DQM). The results are compared with analytical results in the literature. It is remarked that mechanical properties and therefore critical buckling loads of nanocomposite beam are seriously affected by CNTs agglomeration.

Superior photodynamic effect of single-walled carbon nanotubes in aprotic media: a kinetic study

It has been confirmed that single-walled carbon nanotubes (SWCNTs) could generate reactive oxygen species in aprotic media by utilizing photon energy. However, the impact of photon irradiation on SWCNTs and the kinetics of the generation process in aprotic media are still unclear, which significantly limits the yield performance. In this work, the kinetics for photodynamic effects has been investigated by performing characterizations on ultraviolet-treated SWCNTs using Raman spectroscopy, conductive atomic force microscope (in-situ), kelvin probe force microscope, and X-ray photoelectron spectroscopy. It is found that ultraviolet-treated SWCNTs are observed to have more defects, lower conductivity, and less surface charge after energy conversion. Starting from the fundamental intrinsic properties of SWCNTs, the kinetics and formation of these changes are thoroughly discussed. It turns out that the dispersion, chirality, and structural integrity of SWCNTs are important for achieving high-performance photodynamic effects, which are validated using several different SWCNTs as well as other carbon nanomaterials. A type of (6,5) s-SWCNTs exhibited the highest energy efficiency among a variety of other carbon nanomaterials. The yield rate is 2.15 mM/h, and the energy consumption is determined to be 2.79 W·h/mM. This work is expected to help dramatically boost the energy efficiency of the photodynamic effect in aprotic media, and pave the way for designing high-performance carbon nanomaterial-based photoinduced devices.

Effects of single-walled carbon nanotubes and steel fiber on recycled ferrochrome filled electrical conductive mortars

The production of electrically conductive concrete was introduced years ago among construction materials, generally for anti-icing. The present study investigates the electrical, mechanical, dynamic, and microstructural properties of recycled ferrochrome filled cementitious mortars, containing single-walled carbon nanotubes (SWCNTs) and steel fiber. 7, 14, and 28-day non-destructive and 28-day compressive and bending tests of cementitious conductive mortars obtained from five different mixtures were performed. Two-point uniaxial method was used to determine the electrical conductivity properties of the samples. The damping ratio of the samples was obtained by performing dynamic resonance tests. Ultrasound pulse velocity (UPV) and Leeb hardness tests were performed as other non-destructive testing methods. Microstructure analysis at the interfaces of conductive concrete samples were characterized by scanning electron microscopy (SEM), EDS (Energy-Dispersive X-ray Spectroscopy), and X-ray diffraction (XRD). According to the experimental results, all data agreed and confirmed each other. When SWCNT is used in combination with steel fiber, the conductive mortar samples exhibited reasonable conductivity, while their mechanical properties turned out to below.

Effect of Single-Walled Carbon Nanotubes on the Cross-Linking Process in Natural Rubber Vulcanization.

In this study, the effect of single-walled carbon nanotubes (SWCNTs) on the cross-linking of natural rubber (NR) using organic peroxides was investigated. NR-SWCNTs nanocomposites were prepared in an open two-roller mill followed by vulcanization with the compression molding process. Three different organic peroxides, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane (T29), dicumyl peroxide (DCP), and 2,5-bis(tert-butylperoxy)-2,5-dimethyl-3-hexyne (T145), were used as vulcanizing agents. SWCNTs promote a remarkable reduction in the vulcanization time and increase the degree of cross-linking of vulcanized rubber when compared with neat or natural rubber-carbon-black composites; the same tendency was obtained in the NR-SWCNTs vulcanized with sulfur. Additionally, the mechanical performance of the NR-SWCNTs composites was significantly improved up to 75, 83, 27, and 10% for tensile strength, moduli, tear strength, and hardness. Raman spectroscopy studies evidence the occurrence of reaction between nanotube walls and free radicals generated from using organic peroxides during the vulcanization process. These results demonstrate that the incorporation of SWCNTs in combination with the use of organic peroxides for the NR vulcanization represents a potential alternative for the improvement of the physicochemical properties of NR composites.

Effect of Single-Walled Carbon Nanotubes on Thermoelectric Properties of SnTe-Based Composites

Effect of Single-Walled Carbon Nanotubes on Thermoelectric Properties of SnTe-Based Composites

Focused Ion Beam Engineering of Carbon Nanotubes for Optical Rectenna Applications

The optical rectenna is a device that converts the optical range of electromagnetic radiations to a direct current. Optical antennas, as for the radio frequency (RF) antennas, require an antenna’s structure in the range of optical light EM wavelengths, i.e., a few hundred nanometers to a few micrometers. Herein, we demonstrate the optical rectenna effect of single-wall carbon nanotubes (SWCNTs) by cutting them in the resonance lengths of monopole nano-antennas (i.e., λ/4) of 100, 150, and 200 nm to convert incident red, green, and blue lights into a direct current. The physical engineering (cutting) of SWCNTs dispersed on SiO2/Si, comparable to one-quarter of the incident monochromatic light wavelength (i.e., red, green, and blue), is carried out with high-energy gallium (Ga) ion beams, with the help of a focused ion beam (FIB) system. The rectenna characteristics of these engineered SWCNTs are investigated using conductive mode atomic force microscopy (C-AFM). This unprecedented approach to investigating the optical rectennas will open more directions to study the rectenna effect at the nanometer scale.

(Invited) Sustainable Generator and in-Situ Monitor for Reactive Oxygen Species Using Photodynamic Effect of Single-Walled Carbon Nanotubes in Ionic Liquids

Due to the demand of public health maintenance, disinfectant generator technologies that utilize green processes are becoming attractive. It has been confirmed that single-walled carbon nanotubes (SWCNTs) could generate reactive oxygen species (ROS) in water when illuminated with solar irradiation. However, low efficiency due to the competitive reactions between ROS and water in aqueous media and unclear kinetics hinder their potential practical applications. To overcome these limitations, here, the SWCNTs were studied in a nonaqueous ionic liquid (IL) to form a suspension system to generate superoxide (O2 -) under UV light. The as-obtained O2 - from SWCNTs was qualitatively confirmed by electron paramagnetic resonance and UV-visible spectroscopy. The sustainability of the new SWCNTs/IL system was confirmed by UV-visible spectroscopy and Fourier-transform infrared spectroscopy. The IL proved to be an ideal media that could extend the duration of O2 - from a few microseconds (commonly generated in the water) to at least 65 hours in the IL. The kinetics of photodynamic effect was investigated by electrochemical characterizations. A new method was established to in-situ monitor the O2 - level in the IL system. The O2 - level in the IL was quantitatively determined by combining cyclic voltammetry and chronoamperometry techniques. The SWCNTs/IL system generated 4.11 mM of O2 - in a mini-scale generator, which was excessive to germicidal levels for ROS. The sustainable, long duration and high-yield of the generator exhibited an excellent potential as a generator as well as an in-situ monitor for O2 -. This work could pave the way for O2 - generation using SWCNTs and promote its applications in air and water disinfection for public health, as well as O2 - sensitive chemical sensors for monitoring environmental quality.

Exposure of carbon nanotubes affects testis and brain of common carp

Carbon nanotubes production has been rapidly increasing for many potential applications, however, the environmental impact of this nanomaterial needs to be comprehended. The present work focused on unraveling the effects of single-walled carbon nanotubes (SWCNT) in the common carp, Cyprinus carpio. The physicochemical properties of SWCNT were analyzed with X-ray diffraction, Fourier transforms infra-red, UV-Vis absorption, transmission electron microscopy (TEM), and Raman spectroscopy before testing for exposure impact. The effects of SWCNT, were investigated by exposing to two doses viz., 10 and 50 μg/L, for 7 days in adult common carp, in vivo. Expression of key steroidogenic and transcription factor genes related to testis and brain were downregulated after the treatment. The concomitant decreases in serum testosterone and 11-ketotestosterone levels revealed the impact of SWCNT after exposure. Further, SWCNT exposure induced antioxidant enzymes namely glutathione-S-transferases, superoxide dismutase, and catalase in both testis and brain. Concurrently, histological and TEM analysis of testis revealed structural disarray. In addition, SWCNT treatment, in testicular and brain primary cell cultures decreased cell viability with an increase of reactive oxygen species levels, leading to a significant elevation of apoptotic cells. In line with this, low mitochondrial membrane potential and DNA damage were also observed during post SWCNT treatment. Taken together, transient exposure of SWCNT causes toxic effects and alters testicular and brain function in the common carp. Thus, the discharge of carbon nanotubes poses a greater risk to the aquatic environment warranting regulatory measures.

Combined effect of single-walled carbon nanotubes and cadmium on human lung cancer cells.

Co-exposure of widely used single-walled carbon nanotubes (SWCNTs) and ubiquitous cadmium (Cd) to humans through ambient air is unavoidable. Studies on joint toxicity of SWCNTs and Cd in human cells are scarce. We aimed to investigate the joint effects of SWCNTs and Cd in human lung epithelial (A549) cells. Results showed that SWCNTs were safe while Cd induce significant toxicity to A549 cells. Remarkably, Cd-induced cell viability reduction, lactate dehydrogenase leakage, cell cycle arrest, dysregulation of apoptotic gene (p53, bax, bcl-2, casp3, and casp9), and mitochondrial membrane potential depletion were significantly mitigated following SWCNTs co-exposure. Cd-induced intracellular level of reactive oxygen species, hydrogen peroxide, and lipid peroxidation were significantly attenuated by SWCNT co-exposure. Moreover, glutathione depletion and lower activity of antioxidant enzymes after Cd exposure were also effectively abrogated by co-exposure of SWCNTs. Inductively coupled plasma-mass spectrometry study indicated that higher adsorption of Cd on SCWNTs might decreased cellular uptake and the toxic potential of Cd in A549 cells. Our work warranted further research to explore the potential mechanism of joint effects of SWCNTs and Cd at in vivo levels.

Sustainable generator and in-situ monitor for reactive oxygen species using photodynamic effect of single-walled carbon nanotubes in ionic liquids

Due to the increasing concerns regarding public health and climate change, disinfectant generator technologies that utilize green processes are becoming necessary. It has been confirmed that single-walled carbon nanotubes (SWCNTs) can generate reactive oxygen species (ROS) in aqueous media when illuminated with solar irradiation. However, low efficiency due to competitive reactions between ROS and water and unclear kinetics hinder their potential practical applications. To overcome these limitations, here, SWCNTs were studied in a non-aqueous ionic liquid (IL) to form a suspension system for generating superoxide (O2−) under UV light. The as-obtained O2− from SWCNTs was qualitatively confirmed by electron paramagnetic resonance and UV–vis spectroscopy. The sustainability of the new SWCNTs/IL system was confirmed by UV–vis and Fourier-transform infrared spectroscopy. The IL proved to be an ideal media that could extend the lifetime of O2− from a few microseconds (generated in water) to at least 65 h in the IL. The kinetics of photodynamic effect were investigated by electrochemical characterizations. A new method was established to in-situ monitor the O2− level in the IL system. The O2− level in the IL was quantitatively determined by combining cyclic voltammetry and chronoamperometry techniques. The SWCNTs/IL system generated 4.11 mM of O2− in a mini-scale generator, which was in excess of germicidal levels for ROS. The sustainable, long duration and high-yield of the generator exhibited excellent potential as a generator as well as an in-situ monitor for O2−. This work could pave the way for O2− generation using SWCNTs and promote its applications in air and water disinfection for public health, as well as O2− sensitive chemical sensors for monitoring the environmental quality.

Analyzing the effect of chirality and defects on mechanical properties of carbon nanotube reinforced polycarbonate composites using molecular dynamics

This study is mainly focused on predicting the impact of change in chirality and defects in carbon nanotubes (CNTs) on the mechanical properties of CNT reinforced polycarbonate (PC) composites using molecular dynamics (MD) simulations. The effect of single-walled carbon nanotube (SWCNT) reinforcement with different chirality, [three armchair {(5,5), (6,6), (7,7)}, three zigzag {(9,0), (10,0), (12,0)}, and three chiral {(6,4), (7,5), (8,6)}] in PC has been studied using MD simulation. Also, the effect of vacancy and Stone–Wales (SW) defects in CNTs on the mechanical properties of SWCNT-PC composites has also been predicted. It was concluded that for a constant CNT volume fraction (3%), the longitudinal Young’s modulus of armchair SWCNT-PC composites decreases with an increase in (n, n) value by 35.65%. For zigzag and chiral SWCNT-PC composites, the decrease in Young’s modulus was 53.12% and 36% respectively. Vacancy defected SWCNT-PC composites exhibited greater reduction in Young’s modulus in comparison to the SW defected composites. Chiral SWCNT-PC composites showed the highest reduction in Young’s modulus with an increase in the number of defects.

The Effect of Single-Walled Carbon Nanotubes on UDP-Glucuronosyltransferase 1A Activity in Human Liver

Single-walled carbon nanotubes (SWCNTs) are made from rolled single graphene sheets with a diameter in the nanometer range and are potential carriers for drug delivery systems. However, their effects on uridine 5'-diphosphate-glucuronosyltransferase (UGT) 1A activities remain unclear. The present study aimed to investigate the effect of two kinds of SWCNTs (EC1.5-P- and FH-P-SWCNTs) and other nanocarbons on human UGT1A activity due to the proposed application of SWCNTs in drug and gene delivery. β-Estradiol 3-glucuronidation, which is catalyzed mainly by UGT1A1, was inhibited by 99 and 76% in the presence of 0.1 mg/mL EC1.5-P- and FH-P-SWCNTs in human liver microsomes, respectively. The observed decrease of free UGT1A1 protein in the enzyme reaction mixture suggests a higher interaction with SWCNTs, and indicates the inhibition of β-estradiol 3-glucuronidation. Imipramine N-glucuronidation, which is formed mainly by UGT1A4, was also decreased by SWCNTs. Serotonin glucuronidation, which is mainly responsible for UGT1A6, was only influenced by specific nanocarbons in human liver microsomes. The attenuation of free UGT1A6 protein was observed with SWCNTs and carbon black, indicating that UGT1A6 activity was not influenced by the direct interaction of SWCNTs. We also observed a 127% increase by FH-P-SWCNTs for propofol glucuronidation in human liver microsomes, which is catalyzed mainly by UGT1A9. The values of maximum velocity and intrinsic clearance for propofol glucuronidation in the presence of FH-P-SWCNT were 1.8- and 2.0-fold higher than those of the control in human liver microsomes. These results suggest that the effects of SWCNTs on UGT1A are different among isoforms.