Presence Of Single-walled Carbon Nanotubes Research Articles

The effects of single-walled carbon nanotubes (SWCNTs) on the structure and function of human serum albumin (HSA): Molecular docking and molecular dynamics simulation studies

Here, the interaction of single-walled carbon nanotubes (SWCNTs) and human serum albumin (HSA) as one of the most important proteins for carrying and binding of drugs was investigated and the impact of radius to volume ratio and chirality of the SWCNTs was evaluated using molecular docking method. Molecular docking results represented that zigzag SWCNT with radius to volume ratio equal to 6.77 × 10−3 A−2 has the most negative binding energy (−17.16 kcal mol−1) and binds to the HSA cleft by four π–cation interactions. To study the changes of HSA structure, the complex of HSA–SWCNT was subjected to 30 ns molecular dynamics simulation. The MD results showed that HSA was compressed about 2% after interaction with SWCNT. The equilibrated structure of HSA–SWCNT complex was used to compare the binding of warfarin to HSA in the absence and presence of SWCNT. The obtained results represent that warfarin-binding site was changed in the presence of SWCNT and its binding energy was increased. Really, warfarin was bound on the surface of SWCNT instead of its binding site on HSA. It means that HSA function as a carrier for warfarin is altered, the free concentration of warfarin is changed, and its release is decreased in the presence of SWCNT.

Strongly Bound Sodium Dodecyl Sulfate Surrounding Single-Wall Carbon Nanotubes.

NMR techniques have been widely used to infer molecular structure, including surfactant aggregation. A combination of optical spectroscopy, proton NMR spectroscopy, and pulsed field gradient NMR (PFG NMR) is used to study the adsorption number for sodium dodecyl sulfate (SDS) with single-wall carbon nanotubes (SWCNTs). Distinct transitions in the NMR chemical shift of SDS are observed in the presence of SWCNTs. These transitions demonstrate that micelle formation is delayed by SWCNTs due to the adsorption of SDS on the nanotube surface. Once the nanotube surface is saturated, the free SDS concentration increases until micelle formation is observed. Therefore, the adsorption number of SDS on SWCNTs can be determined by the changes to the apparent critical micelle concentration (CMC). PFG NMR found that SDS remains strongly bound onto the nanotube. Quantitative analysis of the diffusivity of SDS allowed calculation of the adsorption number of strongly bound SDS on SWCNTs. The adsorption numbers from these techniques give the same values within experimental error, indicating that a significant fraction of the SDS interacting with nanotubes remains strongly bound for as long as 0.5 s, which is the maximum diffusion time used in the PFG NMR measurements.

Carbon Nanotubes in Tyre Rubbers. Part 1: The Effect of Carbon Nanotubes on the Properties of Breaker Rubber

The processing and mechanical properties of green and vulcanised breaker rubbers based on natural rubbers containing single-wall carbon nanotubes (SCNTs) were studied. SCNTs were treated and introduced into a rubber mix in a composite containing carbon black (88.24%), SCNTs (9.8%), and SKI-3 polyisoprene rubber in solution (1.96%). The presence of –COOH groups on the surface of SCNTs after treatment was confirmed by IR spectroscopy. Increase in the content of SCNTs in the breaker rubber mix to 0.15 or 0.2% leads to an increase in cohesion strength up to 1.6-fold; the Mooney viscosity also increases, and there is an improvement in the vulcanisation properties. Changes in the Payne effect of rubbers containing SCNTs indicate an improvement in the interaction between the carbon black particles. Small amounts of SCNTs ensure a reduction in tg δ at 60°C, and increases in tear strength and in adhesion to metal cord. However, wear resistance deteriorates. The possibility of replacing 30 parts natural rubber with SKI-3 in the presence of SCNTs is shown.

Sonocatalytic degradation coupled with single-walled carbon nanotubes for removal of ibuprofen and sulfamethoxazole

This study examined the degradation of pharmaceuticals ((PhACs), ibuprofen (IBP) and sulfamethoxazole (SMX)) using an ultrasonic (US) reactor at a 1000kHz frequency in the absence and presence of single walled carbon nanotubes (SWNTs). In the absence of SWNTs, maximum degradation of PhACs were achieved under high temperature; 55>35>25>15°C. In addition, the relatively higher degradation of IBP and SMX was obtained under acidic condition at pH 3.5 than pH 7 and 9.5; >99%, 79%, and 72% for IBP and >99%, 75%, and 65% for SMX, respectively. However, H2O2 production increased from 77μM (no SWNTs) to 115μM in the presence of SWNTs (45mg/L) at pH 7. In addition, the removal of IBP and SMX significantly increased under US/SWNTs reaction conditions than US and SWNTs only reactions. The removal of IBP and SMX was 57% and 48% under SWNTs (adsorption) reactions, 77% and 70% under US reactions, and 97% and 92% under US/SWNTs reactions, respectively. This study evaluated the effect of temperature, pH, SWNTs, and physiochemical properties of selected PhACs under US process. In addition, the adsorption molecular modeling was validated with the experimental results.

Influence of the Gastrointestinal Environment on the Bioavailability of Ethinyl Estradiol Sorbed to Single-Walled Carbon Nanotubes.

Recent evidence suggests that, because of their sorptive nature, if single-walled carbon nanotubes (SWCNTs) make their way into aquatic environments, they may reduce the toxicity of other waterborne contaminants. However, few studies have examined whether contaminants remain adsorbed following ingestion by aquatic organisms. The objective of this study was to examine the bioavailability and bioactivity of ethinyl estradiol (EE2) sorbed onto SWCNTs in a fish gastrointestinal (GI) tract. Sorption experiments indicated that SWCNTs effectively adsorbed EE2, but the chemical was still able to bind and activate soluble estrogen receptors (ERs) in vitro. However, centrifugation to remove SWCNTs and adsorbed EE2 significantly reduced ER activity compared to that of EE2 alone. Additionally, the presence of SWCNTs did not reduce the extent of EE2-driven induction of vitellogenin 1 in vivo compared to the levels in organisms exposed to EE2 alone. These results suggest that while SWCNTs adsorb EE2 from aqueous solutions, under biological conditions EE2 can desorb and retain bioactivity. Additional results indicate that interactions with gastrointestinal proteins may decrease the level of adsorption of estrogen to SWCNTs by 5%. This study presents valuable data for elucidating how SWCNTs interact with chemicals that are already present in our aquatic environments, which is essential for determining their potential health risk.

Dispersed single wall carbon nanotubes do not impact mitochondria structure or function, but technical issues during analysis could yield incorrect results.

Mitochondria are the organelles of cells that generate a majority of the cell's energy through ATP and are involved in programmed cell death through apoptosis. An understanding of non-specific targeting of nanomaterials, including single wall carbon nanotubes (SWCNTs), to organelles is important in trying to modulate cell function or determine the cellular toxicity with long term exposure. Here, we examine the impact of SWCNTs dispersed with Pluronic F127 and protein on mitochondria using a battery of standard tests. Seahorse XF24 analysis suggests complete loss of mitochondiral function, but this data is artifactual due to SWCNTs adsorbing onto the Seahorse probes. Imaging using the mitochondrial functional dye JC-1 gives inconclusive results owing to fluorescence quenching by SWCNTs. We observe no co-localization or reorganization of mitochondria in the presence of SWCNTs, although the results could have been misinterpreted had we not been correcting for significant fluorescence quenching by SWCNTs. In sum, the surface activity and fluorescence quenching of SWCNTs alter many traditional cellular assays. However, light emitting (luciferase) assays show that ATP levels are not altered with SWCNT treatment suggesting that mitochondiral function is not impacted as well as that light-emitting assays are an essential complimentary approach for quantitative, unambiguous cellular study of nanomaterials.

Optical properties of single-walled carbon nanotubes functionalized with copolymer poly(3,4-ethylenedioxythiophene-co-pyrene)

Optical properties are reported for composites based on single-walled carbon nanotubes (SWNTs) and copolymer poly(3,4-ethylenedioxythiophene-co-pyrene) (PEDOT-Py) prepared by chemical polymerization of two monomers in the presence of carbon nanotubes. A charge transfer between SWNTs and the PEDOT-Py copolymer was demonstrated by Raman scattering. The increase in the relative intensity of the Raman lines peaked at 440–577 cm−1, which were assigned to the ethylenedioxy ring vibrational modes, indicated a significant hindrance steric in the case of the composites based on the PEDOT-Py copolymer and metallic SWNTs. The increase in the absorbance of IR band peaked at 984 cm−1 occurred simultaneously with the disappearance of the IR band at 1639 cm−1. This finding was a consequence of the formation of new covalent bonds between SWNTs and the thiophene and benzene rings of the repeating units of the PEDOT-Py copolymer. The photoluminescence (PL) quenching process of the PEDOT-Py copolymer was induced by semiconducting SWNTs. The PL quenching of PEDOT-Py copolymer in the presence of SWNTs was demonstrated based on the energy level diagrams of the two constituents of the PEDOT-Py/SWNTs composite material.

Mobility enhancement of hole transporting layer in quantum-dot light-emitting diodes incorporating single-walled carbon nanotubes

Polymeric hole-transporting layers (HTLs) in quantum-dot light-emitting diodes (QLEDs) usually exhibit lower charge carrier transport properties (i.e. carrier mobility) than those of electron-transporting layers (ETLs) which consist mainly of metal oxide nanoparticles, such as TiO2 or ZnO. The difference of carrier transport properties between HTLs and ETLs creates an unbalanced charge injection in the QLED, which results in electron charging of the quantum-dot (QD) and the subsequent non-radiative Auger recombination process, attributing to detrimental effects on QLEDs. In this study, we incorporate small amounts (0.001 to 0.010wt.%) of single-walled carbon nanotubes (SWCNTs), which have ultrafast carrier transport properties, with the HTL material in the QLED to overcome the intrinsic hole-mobility limitation of the HTL material. We adopt poly (N-vinylcarbazole), which has a considerably low hole-mobility of 2.5×10−6cm2V−1s−1, as the HTL of our QLED. This intentionally-created unbalanced charge injection of our QLEDs allows us to take transient electroluminescence (TEL) measurements, a dynamic method to determine minor carrier mobility while maintaining overall device structure. We observe a reduced delay time for TEL onsets in the presence of SWCNTs in the HTL, which is clear evidence for hole-mobility enhancement. Compared with our normal device, 55% enhancement of zero-field hole mobility from is recorded from 0.005wt.% SWCNT-incorporated QLED. Simultaneously, luminance and efficiency of devices are also maximized when 0.005wt.% SWCNTs are incorporated with PVK HTL (from 13,962cd/m2, 1.32% to 16,922cd/m2, 2.54%, respectively for luminance and current efficiency). Consequently, A linear correlation between mobility enhancement and luminance is obtained, clearly demonstrating that these performance enhancement is due to the enhancement of hole mobility of the HTL. Based on our study, we expect that incorporation of SWCNTs in the HTL have a potential to further the improvement of QLED displays.

Enhancement of electrical conductivity, director relaxation frequency and slope of electro-optical characteristics in the composites of single-walled carbon nanotubes and a strongly polar nematic liquid crystal

ABSTRACTIn the present work, single-walled carbon nanotubes (SWCNTs) were dispersed in a room temperature nematic liquid crystal 4-pentyl-4′-cyanobiphenyl at the concentration of 0.02 and 0.05 wt%. Differential scanning calorimetry and temperature-dependent dielectric studies suggest decrease in clearing temperature of the composite materials as compared to the pure material. Ionic conductivity increases by two orders of magnitude due to the dispersion of such a low concentration (0.05 wt%) of SWCNTs. Dielectric studies also show that the presence of the SWCNTs decreases the effective longitudinal as well as transverse components of the dielectric permittivity. For homeotropic aligned samples, a relaxation mechanism has been detected in the lower MHz region both for the pure as well as dispersed samples. Presence of SWCNTs increases the relaxation frequency corresponding to flip-flop motion of molecules around their short axes. From frequency-dependent dielectric studies, important dielectric parameters such as relaxation frequency, dielectric strength and distribution parameters have been determined. Electro-optical experiments show that the threshold voltage decreases and the steepness of the transmission voltage curve improves due to the dispersion of SWCNTs.

Interaction Dynamics in Inhibiting the Aggregation of Aβ Peptides by SWCNTs: A Combined Experimental and Coarse-Grained Molecular Dynamic Simulation Study.

The aggregation of amyloid-β peptides (Aβ) is considered as the main possible cause of Alzheimer's disease (AD). How to suppress the formation of toxic Aβ aggregates has been an intensive concern over the past several decades. Increasing evidence shows that whether carbon nanomaterials can suppress or promote the aggregation depends on their physicochemical properties. However, their interaction dynamics remains elusive as amyloid fibrillation is a complex multistep process. In this paper, we utilized atomic force microscopy (AFM), electrostatic force microscopy (EFM), ThT/fluorescence spectroscopy, and cell viability measurements, combined with coarse-grained molecular dynamic (MD) simulations to study the dynamic interaction of full length Aβ with single-walled carbon nanotubes (SWCNT). At the single SWCNTs scale, it is found that the presence of SWCNTs would result in rapid and spontaneous adsorption of Aβ1-40 peptides on their surface and stacking into nonfibrillar aggregates with reduced toxicity, which plays an important role in inhibiting the formation of toxic oligomers and mature fibrils. Our results provide new clues for studying the interaction in amyloid/SWCNTs system as well as for seeking amyloidosis inhibitors with carbon nanomaterials.

Thermal radiation energy due to SWCNTs on MHD nanofluid flow in the presence of seawater/water: Lie group transformation

Abstract An investigation of the boundary layer nanofluids flow over a porous wedge in the presence of uniform transverse magnetic field and thermal radiation energy has been analyzed. Water and seawater based nanofluid containing copper, aluminum oxide and Single Walled Carbon nanotubes (SWCNTs) is taken into consideration. The governing equations in terms of ODEs are solved using fourth–fifth order Runge–Kutta–Fehlberg method with shooting technique. Approximate solution of temperature, velocity, the rate of heat transfer and the shear stress at the wedge are illustrated graphically for several values of the pertinent parameters. Thermal conductivity enhancements of water and seawater in the presence of single-walled carbon nanotubes (SWCNTs) are presented. The thermal boundary layer of SWCNTs–water is compared to SWCNTs–seawater on absorbing the incident thermal energy radiation and transmitting it to the nanofluid by convection. Momentum and thermal boundary layer thickness for SWCNTs–seawater is stronger than SWCNTs–water with increase of the radiation parameter because of low thermal conductivity of seawater. The rate of heat transfer of Cu–seawater is significantly stronger than all the other mixtures in the flow regime because of the combined effects of density of copper and seawater.

Sonocatalytical degradation enhancement for ibuprofen and sulfamethoxazole in the presence of glass beads and single-walled carbon nanotubes

Sonocatalytic degradation experiments were carried out to determine the effects of glass beads (GBs) and single-walled carbon nanotubes (SWNTs) on ibuprofen (IBP) and sulfamethoxazole (SMX) removal using low and high ultrasonic frequencies (28 and 1000kHz). In the absence of catalysts, the sonochemical degradation at pH 7, optimum power of 0.18WmL−1, and a temperature of 15°C was higher (79% and 72%) at 1000kHz than at 28kHz (45% and 33%) for IBP and SMX, respectively. At the low frequency (28kHz) H2O2 production increased significantly, from 10μM (no GBs) to 86μM in the presence of GBs (0.1mm, 10gL−1); however, no enhancement was achieved at 1000kHz. In contrast, the H2O2 production increased from 10μM (no SWNTs) to 31μM at 28kHz and from 82μM (no SWNTs) to 111μM at 1000kHz in the presence of SWNTs (45mgL−1). Thus, maximum removals of IBP and SMX were obtained in the presence of a combination of GBs and SWNTs at the low frequency (94% and 88%) for 60min contact time; however, >99% and 97% removals were achieved for 40 and 60min contact times at the high frequency for IBP and SMX, respectively. The results indicate that both IBP and SMX degradation followed pseudo-first-order kinetics. Additionally, the enhanced removal of IBP and SMX in the presence of catalysts was because GBs and SWNTs increased the number of free OH radicals due to ultrasonic irradiation and the adsorption capacity increase with SWNT dispersion.

Enzymatic formation of carbohydrate rings catalyzed by single-walled carbon nanotubes.

Macrocyclic carbohydrate rings were formed via enzymatic reactions around single-walled carbon nanotubes (SWNTs) as a catalyst. Cyclodextrin glucanotransferase, starch substrate and SWNTs were reacted in buffer solution to yield cyclodextrin (CD) rings wrapped around individual SWNTs. Atomic force microscopy showed the resulting complexes to be rings of 12-50 nm in diameter, which were highly soluble and dispersed in aqueous solution. They were further characterized by Raman and Fourier transform infrared spectroscopy and molecular simulation using density functional theory calculation. In the absence of SWNT, hydrogen bonding between glucose units determines the structure of maltose (the precursor of CD) and produces the curvature along the glucose chain. Wrapping SWNT along the short axis was preferred with curvature in the presence of SWNTs and with the hydrophobic interactions between the SWNTs and CD molecules. This synthetic approach may be useful for the functionalization of carbon nanotubes for development of nanostructures.

Influence of Single-Walled Carbon Nanotubes Enriched in Semiconducting and Metallic Tubes on the Vibrational and Photoluminescence Properties of Poly(para-phenylenevinylene)

A new synthesis method based on the electrochemical reduction of α,α,α′,α′-tetrabromo-p-xylene in the presence of single-walled carbon nanotubes (SWNTs) is used to obtain composites of carbon nanotubes (CNTs) functionalized with poly(para-phenylenevinylene) (PPV). To separate the effects of metallic and semiconducting CNTs on their interaction with PPV, the experiments are carried out with SWNTs enriched in semiconducting (S, 99%) and metallic (M, 98%) tubes. Significant changes in the relative intensity and shift of the radial breathing vibrational mode are reported in the Raman spectra of the as-prepared SWNTs samples, i.e., as mixtures of metallic (33%) and semiconducting (66%) entities and SWNTs enriched in M tubes (98%) that result from the electrofunctionalization with PPV. This different behavior originates in the noncovalent and covalent functionalization of SWNTs enriched in M and S SWNTs tubes with PPV, respectively. A gradual decrease in the absorption of the infrared (IR) bands of PPV situated...

Diameter-control in synthesis of carbon nanotubes inside porous stainless steel block and application to glucose fuel cell electrode

Carbon nanotubes (CNTs) can be synthesized on inner surface of a porous stainless steel block by feeding ethanol or methanol as carbon source. In comparison with a conventional CNT growth in the porous stainless steel block by feeding ethylene, the diameter of CNTs in the newly-developed conditions using the alcohols are significantly smaller. In these conditions, a radial breathing mode were observed in Raman spectra, indicating the presence of single-walled carbon nanotubes. When the porous stainless steel block including CNTs directly grown on its inner surface is used for an anode in a glucose fuel cell, its power generation using the new CNT growth condition with ethanol or methanol can be improved by approximately three times higher than using the conventional condition with ethylene. Compared with the two alcohols used here, the fuel cell using the anode with the CNTs synthesized from methanol can exhibit 10% higher power than that from ethanol. According to Raman shift analysis and TEM observation, the surface area and the crystallinity of CNTs seem to be the key factors to realize the high electric generation performance.

Multi and single walled carbon nanotubes: effects on cell responses and biomineralization of osteoblasts cultures.

The use of carbon nanotubes (CNTs) on the development of biomaterials has been motivated by their excellent mechanical properties that could improve synthetic bone materials. However, the toxicity of CNTs on the tissue/implant interface and their influence on the biomineralization process have some contradictions. We investigated the influence of CNTs on osteoblasts plated on titanium (Ti) discs or plastic surfaces. We evaluated osteoblasts viability, alkaline phosphatase (ALP) activity, and mineralized matrix formation in the different phases of osteoblasts growth in the presence of single-walled CNTs (SWCNTs) and multi-walled CNTs (MWCNTs). An increase in osteoblasts viability was observed at the 21st day for both CNTs on plastic surface, while viability increased for MWCNTs at the 7th and 14th days and at the 7th day for SWCNTs on Ti discs compared to control. ALP activity increased at the 14th and 21st days for MWCNTs on plastic surfaces. For cells incubated with SWCNTs, an increase in ALP activity at the 7th day for plastic surface and at the 14th day for both materials (plastic and Ti) was observed. The mineralized matrix formation increased at the 21st day on plastic surface with SWCNTs, and at the 14th and 21st days for both CNTs on Ti discs. In conclusion, both SWCNTs and MWCNTs are not toxic to osteoblasts at concentrations up to 5×10(-5) and 1.3×10(-2)mg/mL, respectively, either in Ti discs or plastic surfaces. In the long term, the cells grown in contact with both CNTs and Ti presented better results regarding bone-like nodules formation.

Effect of single-walled carbon nanotubes with imide cycles on the synthesis and properties of polycaproamide

The anionic polymerization of e-caprolactam in the presence of single-walled carbon nanotubes with grafted acyllactam groups or polyimide macromolecules is performed. It is shown that the polymerization of e-caprolactam slows down with an increase in the filler concentration. The introduction of 0.01 wt % nanotubes with polyimide fragments into polycaproamide leads to a 25% increase in the compressive modulus. In this case, the Izod impact strength is 10 kJ/m2, that is, 150% higher than that for an unfilled polycaproamide or polycaproamide containing other types of nanotubes.

Effect of single walled carbon nanotubes on the threshold voltage of dye based photovoltaic devices

Carbon nanotubes are being widely used in organic photovoltaic (OPV) devices as their usage has been reported to enhance the device efficiency along with other related parameters. In this work we have studied the energy (Ec) effect of single walled carbon nanotubes (SWCNT) on the threshold voltage (Vth) and also on the trap states of dye based photovoltaic devices. SWCNT is added in a series of dyes such as Rose Bengal (RB), Methyl Red (MR), Malachite Green (MG) and Crystal Violet (CV). By analysing the steady state dark current–voltage (I–V) characteristics Vth and Ec is estimated for the different devices with and without addition of SWCNT. It is observed that on an average for all the dyes Vth is reduced by about 30% in presence of SWCNT. The trap energy Ec also reduces in case of all the dyes. The relation between Vth, Ec and total trap density is discussed. From the photovoltaic measurements it is seen that the different photovoltaic parameters change with addition of SWCNT to the dye based devices. Both the short circuit current density and fill factor are found to increase for all the dye based devices in presence of SWCNT.

High‐Temperature Deformation Mechanisms in Monolithic 3YTZP and 3YTZP Containing Single‐Walled Carbon Nanotubes

Monolithic 3YTZP and 3YTZP containing 2.5 vol% of single‐walled carbon nanotubes (SWCNT) were fabricated by Spark Plasma Sintering (SPS) at 1250°C. Microstructural characterization of the as‐fabricated 3YTZP/SWCNTs composite shows a homogeneous CNTs dispersion throughout the ceramic matrix. The specimens have been crept at temperatures between 1100°C and 1200°C in order to investigate the influence of the SWCNTs addition on high‐temperature deformation mechanisms in zirconia. Slightly higher stress exponent values are found for 3YTZP/SWCNTs nanocomposites (n~2.5) compared to monolithic 3YTZP (n~2.0). However, the activation energy in 3YTZP (Q = 715 ± 60 kJ/mol) experiences a reduction of about 25% by the addition of 2.5 vol% of SWCNTs (Q = 540 ± 40 kJ/mol). Scanning electron microscopy studies indicate that there is no microstructural evolution in crept specimens, and Raman spectroscopy measurements show that SWCNTs preserved their integrity during the creep tests. All these results seem to indicate that the high‐temperature deformation mechanism is grain‐boundary sliding (GBS) accommodated by grain‐boundary diffusion, which is influenced by yttrium segregation and the presence of SWCNTs at the grain boundary.

Improvement of electrical and photovoltaic properties of methyl red dye based photoelectrochemical cells in presence of single walled carbon nanotubes

In this work, we investigated the effect of single walled carbon nanotubes (SWCNT) on the electrical and photovoltaic properties of methyl red (MR) dye based photoelectrochemical cell (PEC). MR dye based PEC with LiClO4 as ion salt were fabricated with and without mixing SWCNT. The cells were characterized through electrical and optical measurements. The performance of the devices changed drastically in presence of SWCNT. The transition voltage and trap energy of the cells were estimated from the steady-state dark current voltage (I-V) analysis. The transition voltage and trap energy decreased for MR dye cell in presence of SWCNT. Open circuit voltage (Voc), short circuit current (Jsc), fill factor (FF) and power conversion efficiency (η) increased due to the addition of SWCNT. Further measurement of the transient photocurrent showed that the growth and decay of photocurrent was quite faster in presence of SWCNT. The photocurrent decay with time was fitted for both the cells and found to follow a power law relation which indicates dispersive transport mechanism with exponential trap states distributed in between lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) levels. Possible interpretation is done on the lowering of trap energy with the photocurrent. These results suggest that SWCNT lowers the trap energy of the cells by providing efficient percolation pathways for the conduction of charges. It is expected that due to lowering of trap energy the residing time of the free carriers within the traps decreases. In other words, it may also be said that the charge recombination decreases. These factors affect the overall conduction of charges and improve the electrical and photovoltaic properties.