Single-walled Carbon Nanotubes Concentration Research Articles

Spin coated ultrathin PEDOT:PSS/SWCNT film with high electronic conductivity

Conductive Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been extensively used as non-metallic electrodes. However, the relatively low electrical conductivity of pristine PEDOT:PSS film restricts its further application. Although doping high content conductive filler or increasing the film thickness are effective for enhancing the electrical property, the transparency is sacrificed, which limits the application of PEDOT:PSS films. In this study, preparing PEDOT:PSS composite film with highly conductive and transparent property was the primary purpose. To achieve this goal, single-walled carbon nanotubes (SWCNTs) and dimethyl sulfoxide (DMSO) was chosen to composite with PEDOT:PSS. The spin-coated SWCNT/PEDOT:PSS composite film exhibited excellent electrical conductivity and transparency. The electrical conductivity of composite film with desired transmittance property (78%) reached the highest value (1060.96 S cm−1) at the SWCNTs content was 6 wt%. Under the modification process applied in this work, the non-conductive PSS was partially removed by incorporated DMSO and SWCNTs. Then, the molecular chains of PEDOT stretched and adsorbed onto the surface of SWCNTs, forming a highly efficient three-dimensional conductive structure, which contributed to the enhancement of electrical conductivity and transparency. Additionally, the spin-coating process allowed for the reduction of film thickness, ensuring better transparency. This research contributed to expanding the further applications of PEDOT:PSS films in high-performance transparent film electrodes.

Investigation of electromagnetic interference shielding performance of ultra-high-performance mortar incorporating single-walled carbon nanotubes and steel fiber

For security amenities and key infrastructure, construction materials with extraordinary mechanical, durability, and electromagnetic interference (EMI) shielding performance are essential. This study investigates the EMI shielding performance of ultra-high performance mortar (UHPM) incorporating single-walled carbon nanotubes (SWCNT) and steel fibers. Currently, no such work is present in the existing literature. Eight mixtures were prepared with varying SWCNT dosages (0%–0.03 % by weight of cement) and steel fiber additions (1.2 % of the volume of the UHPM mixture). The performance of UHPM incorporating SWCNT and steel fibers was evaluated through flow diameter, compressive strength, flexural strength, Schmidt hardness, ultrasonic pulse velocity, EMI shielding performance, and scanning electron microscopy analysis tests. It is observed that increasing the SWCNT content enhances the compressive strength, flexural strength, ultrasonic pulse velocity, and Schmidt hardness of UHPM. The addition of steel fibers further enhances compressive (up to 22 %) and flexural (up to 92 %) strengths. In terms of the transmittance behavior, the improved EMI shielding performance of UHPM with the increasing SWCNT content is observed prominently at high electromagnetic frequencies (i.e., 2500 MHz–5100 MHz). However, the improved shielding performance is observed to be quite low, limited to 10 dB. Moreover, combining steel fibers and SWCNT enhances the EMI shielding performance of UHPM in terms of the transmittance behavior. As a result, UHPM incorporating SWCNT and steel fibers behaves as an absorbent material, shielding a significant amount of energy, approximately 45 dB, at a frequency of 5000 MHz. Based on the results, UHPM incorporating SWCNT and steel fibers can be used effectively as EMI shielding material. The findings of this study will enhance the practical applications of UHPM incorporating SWCNT and steel fibers.

An investigation on enhancing the wear resistance of PTFE-based composites through complex fillers incorporating a combination of kaolinite and single-walled carbon nanotubes

ABSTRACT In this study, the combined effect of kaolinite with single-walled carbon nanotubes (SWCNTs) on mechanical, tribological, thermodynamic properties and structure of polymer composites based on polytetrafluoroethylene was investigated. Combination of SWCNTs with the composite mixture (containing kaolinite) was carried out in liquid and dry forms by ultrasonic dispersion. X-ray diffraction analysis revealed that the composite with 0.5 wt.% SWCNTs and 1 wt.% kaolinite in the liquid treatment was characterized by a 12% increase in the degree of crystallinity. It is shown that the introduction of complex fillers into PTFE significantly increased the wear resistance of composites by 688 times compared to the initial PTFE. Mechanical testing of the composites showed an increase in elastic modulus by 29% and 28% increase in compressive strength compared to the initial PTFE. The friction surface of the composites was investigated using IR spectroscopy and scanning electron microscopy. It was registered that the PCM friction surface is characterized by the formation of “scaly” structures. The IR spectra of PCM friction surfaces revealed the presence of hydroxyl groups and carboxylate anions – perfluorocarboxylic acid. It indicates the formation of a new structure on the friction surfaces of the composites with the formation of “scaly” micro-protrusions at increasing SWCNTs concentration. Keywords: polytetrafluoroethylene; single-walled carbon nanotubes; kaolinite; ultrasonic treatment.

Enhancement of the mechanical properties in ultra-low weight SWCNT sandwiched PDMS composites using a novel stacked architecture

This study focuses on enhancing the mechanical properties of thin, soft, free-standing films via a layer-by-layer (LBL) fabrication process called LBL-FP. Soft polymer nanocomposite (PNC) thin films, combining polydimethylsiloxane (PDMS) and single-walled carbon nanotubes (SWCNT) at ultra-low loadings using a unique bottom-up LBL-FP, are examined. Two different structures of layered composites, (i) LBL PNCs- Layered composites with alternating layers of PDMS and SWCNT, (ii) Bulk PNCs- Layered composites with SWCNT dispersed in the bulk of PDMS, are comparatively investigated for their structural and mechanical properties. Silane-functionalized SWCNT strengthens the chemical bonding with PDMS, improving adhesion and dispersion. Mechanical analysis using nanoindentation, delamination, and dynamic analysis highlights the advantages of LBL PNCs with alternating layers of PDMS and SWCNT. Notably, LBL PNC (0.5 wt%) exhibits significant improvements, such as 2.6X increased nanoindentation resistance, 3X improved viscoelasticity, and (2–5)X enhanced tensile properties in comparison with neat PDMS. Due to this, LBL PNCs offer potential for soft, lightweight applications like wearables, electromagnetic interference shielding materials, and strain sensors while advancing composite thin film mechanics. The study emphasizes using a stacked architecture to produce PDMS-SWCNT multilayered PNCs with improved mechanics utilizing ultra-low concentrations of SWCNT. This first-of-its-kind stack design facilitates possibilities for lightweight composites utilizing less fillers. The LBL assembly involves the stacking of alternating layers of different materials, each contributing specific properties to enhance the overall strength and toughness of the structure.

Thermophysical Properties of SWCNT Nanofluid

AbstractThe current paper has the objective of exploring the thermophysical properties (TPPs) of single walled carbon nanotube (SWCNT) nanofluids (NFs) for heat transfer applications. The effect of dispersing the nanotubes in conventional heat transfer fluids (HTFs) has been investigated. Carbon nanotubes (CNTs) have exceptionally high thermal conductivities. Using the effective medium theory, density, specific heat, thermal conductivity, and viscosity has been evaluated as functions of volume fractions. The base fluids considered in this work are water, ethylene glycol, engine oil, and kerosene oil as these are the commonly used HTFs for industrial applications. Theoretical predictions from this study show an increase in density, thermal conductivity, and viscosity with volume fraction while there is a decrease in specific heat with volume fraction. The effect of the aspect ratio (AR) of CNTs on the thermal conductivity of NF is also investigated. For low volume fractions of SWCNT, the thermal conductivity has been found to increase with AR. Further, this study has been extended for a real‐world application of heat transfer using SWCNT. In this paper, a numerical investigation of heat transfer in a square enclosure with differentially heated vertical walls, filled with SWCNT‐water NF under natural convection is carried out. Due to low concentrations of SWCNT in water, single phase flow is assumed. Velocity and temperature distributions are obtained as solutions to the energy and Navier–Stoke's equations. A comparison of the temperature and velocity profile has been represented by simulating the system over a range of Rayleigh numbers.

Advanced hydrophobic cotton threads enhanced with graphene/SWCNT nanocomposites for exceptionally high electrical conductivity

This study investigates the fabrication and characterization of conductive threads using graphene and single-walled carbon nanotubes (SWCNTs), focusing on their application in wearable electronics and smart textiles. We employed the drop casting method to coat cotton threads with a polar solvent-based dispersion of graphene and SWCNTs, aiming to enhance their electrical conductivity and hydrophobic properties. Our results demonstrate that the electrical conductivity of these conductive threads significantly increases with the concentration of graphene and SWCNTs, reaching a peak conductivity of 68.75 S. cm−1 in threads coated with a SWCNT layer followed by a graphene layer. These threads exhibit metallic behavior across a broad temperature range (room temperature to 130 °C) and maintain electrical stability over an extended period. Additionally, varying degrees of hydrophobicity were observed among the different thread compositions. A washability study revealed that threads with a bilayer of SWCNT and graphene maintained higher electrical conductivity after multiple wash cycles compared to those fabricated with a mixed layer of these materials. This research not only highlights the potential of graphene and SWCNTs in developing advanced conductive threads but also addresses the challenges in scalability and reproducibility, paving the way for future innovations in smart textile applications.

The Influence of Single-Walled Carbon Nanotubes on the Aging Performance of Polymer-Modified Binders.

The use of polymer-modified binders in asphalt concrete makes it possible to increase the efficiency and durability of highways. However, at present, there is an important and unresolved problem in this area, making it impossible to fully exploit the potential of modified binders. This is a tendency of aging processes that leads to the premature destruction of the pavement. In many literary sources, it is reported that reasons are related to the peculiarity of the chemical composition and occur at the submicron level. Therefore, the influence of single-walled carbon nanotubes has been studied for a better understanding of aging processes. The aging processes of the RTFOT (rolling thin film oven test) and PAV (pressure aging vessel) modified with SBS (styrene-butadiene-styrene) polymer, single-walled carbon nanotubes, and waste industrial oil were simulated in a laboratory furnace. Microstructural features were studied using the method of infrared spectral analysis. The dependences of viscoelastic properties on the component composition of binders were investigated. The optimal content of single-walled carbon nanotubes (0.001%), SBS (styrene-butadiene-styrene) polymer (3.5%), and waste industrial oil (4%) in the binder composition was established, which synergistically improved the performance of the modified binder from PG (52-22) (performance grade) to PG (64-34). It was established that single-walled carbon nanotubes provide improvement in the durability parameter ∆Tc binder by 150%, improved relaxation properties at low temperatures, and resistance to fatigue damage.

Exposure to single-walled carbon nanotubes differentially affect in vitro germination, biochemical and antioxidant properties of Thymus daenensis celak. seedlings

Carbon nanomaterials such as single-walled carbon nanotubes (SWCNTs) offer a new possibility for phyto-nanotechnology and biotechnology to improve the quality and quantity of secondary metabolites in vitro. The current study aimed to determine the SWCNTs effects on Thyme (Thymus daenensis celak.) seed germination. The seedlings were further assessed in terms of morphological and phytochemical properties. Sterile seeds were cultured in vitro and treated with various concentrations of SWCNTs. Biochemical analyses were designed on seedling sample extracts for measuring antioxidant activities (AA), total flavonoids (TFC) and phenolic contents, and the main enzymes involved in oxidative reactions under experimental treatments. The results indicated that an increase in SWCNTs concentration can enhance the total percentage of seed germination. The improvement was observed in samples that received SWCNTs levels of up to 125 µg ml−1, even though seedling height and biomass accumulation decreased. Seedling growth parameters in the control samples were higher than those of grown in SWCNT-fortified media. This may have happened because of more oxidative damage as well as a rise in POD and PPO activities in tissues. Additionally, secondary metabolites and relevant enzyme activities showed that maximum amounts of TPC, TFC, AA and the highest PAL enzyme activity were detected in samples exposed to 62.5 µg ml−1 SWCNTs. Our findings reveal that SWCNTs in a concentration-dependent manner has different effects on T. daenensis morphological and phytochemical properties. Microscopic images analysis revealed that SWCNTs pierce cell walls, enter the plant cells and agglomerate in the cellular cytoplasm and cell walls. The findings provide insights into the regulatory mechanisms of SWCNTs on T. daenensis growth, germination and secondary metabolites production.

Influence of Excess Conjugated Wrapping Polymer in Semiconducting Single-Walled Carbon Nanotube Dispersions

Single-walled carbon nanotubes (SWNTs) are promising nanomaterials for incorporation into organic electronic devices (OEDs), with the potential to fabricate flexible devices while exploiting inexpensive solution-processing techniques. As-synthesized SWNTs are insoluble and comprised of a mixture of metallic and semiconducting SWNTs (sc-SWNTs), necessitating dispersal and purification before integration into OEDs. Refinement of conjugated polymer extraction techniques has allowed for the isolation of sc-SWNTs from metallic in a reproducible and scalable manner. The availability of highly-pure sc-SWNT materials has facilitated the production of thin-film transistors (TFTs) with very high charge carrier mobilities, outperforming organic small molecule and polymer semiconductors. However, the realization of commercial OED applications of polymer-sorted sc-SWNTs have not yet been achieved, partially due to the prohibitive time and materials costs associated with purifying sc-SWNTs.Current protocols for dispersing sc-SWNTs with conjugated polymers involve three broad steps: (1) dispersion of bulk SWNT material, (2) removal of non-dispersed carbonaceous materials, and (3) removal of excess polymer through filtration or centrifugation. The final step of removal of excess polymer is time-consuming and wasteful, but viewed as necessary for preparing high-performing TFTs, as the conjugated polymer has much lower performance compared to SWNTs.In this study we performed the first systematic investigation of the effect of excess polymer on SWNT TFT performance. Three SWNT concentrations were investigated, with varying ratios of excess polymer added to each. TFT device performance was monitored using several metrics, including: mobility, threshold voltage, on/off ratios and hysteresis. Characterization of large numbers of replicate TFT devices determined that below a threshold amount of excess polymer the presence of excess polymer did not have a negative impact on device performance. Detailed analysis of the sc-SWNT films through Raman spectroscopy and atomic force microscopy (AFM) confirmed that a simple rinsing step was sufficient to remove all the unbound conjugated polymer from the substrate surface without affecting the sc-SWNT network. The volume of solvent required for the rinsing step was substantially lower than that required for filtration or centrifugation steps. Furthermore, at higher SWNT concentrations the excess polymer prevented nanotube bundling, resulting in moderate improvements in both mobility and on/off ratios. Our results were reproducible for two different conjugated polymer sc-SWNT systems, demonstrating the versatility of this procedure.

Molecular Dynamics Modeling for the Determination of Elastic Moduli of Polymer-Single-Walled Carbon Nanotube Composites.

The use of carbon nanotubes to improve the mechanical properties of polymers is one of the promising directions in materials science. The addition of single-walled carbon nanotubes (SWCNTs) to a polymer results in significant improvements in its mechanical, electrical, optical, and structural properties. However, the addition of SWCNTs does not always improve the polymer properties. Also, when a certain content of SWCNTs is exceeded, the mechanical properties of the nanocomposite become worse. This article reports the results of computer simulations for predicting the mechanical properties of polymer/single-walled carbon nanotube nanocomposites. The efficiency of reinforcing polymer composites is considered depending on the concentration of carbon nanotubes in the polymer matrix, their size, and structure. The elastic moduli of the nanocomposites are predicted using computer simulations for unit cell tension (0.1%). General trends in the mechanical properties of composites with polypropylene (PP), poly(ethyl methacrylate) (PEMA), polystyrene (PS) matrices, and SWCNTs are shown.

Influence of Single-Wall Carbon Nanotube Suspension on the Mechanical Properties of Polymeric Films and Electrospun Scaffolds.

Carbon nanotubes (CNTs) are used in applications ranging from electrical engineering to medical device manufacturing. It is well known that the addition of nanotubes can influence the mechanical properties of various industrial materials, including plastics. Electrospinning is a popular method for fabricating nanomaterials, widely suggested for polymer scaffold manufacturing. In this study, we aimed to describe the influence of single-walled carbon nanotube (SWCNT) suspensions on polymeric poured films and electrospun scaffolds and to investigate their structural and mechanical properties obtained from various compositions. To obtain films and electrospun scaffolds of 8 mm diameter, we used poly-ε-caprolactone (PCL) and poly(cyclohexene carbonate) (PCHC) solutions containing several mass fractions of SWCNT. The samples were characterized using tensile tests, atomic force and scanning electronic microscopy (AFM and SEM). All the studied SWCNT concentrations were shown to decrease the extensibility and strength of electrospun scaffolds, so SWCNT use was considered unsuitable for this technique. The 0.01% mass fraction of SWCNT in PCL films increased the polymer strength, while fractions of 0.03% and more significantly decreased the polymer strength and extensibility compared to the undoped polymer. The PHCH polymeric films showed a similar behavior with an extremum at 0.02% concentration for strength at break.

Improving recycled carbon fiber by single walled carbon nanotubes in reinforcement of polyamide composites

Recycled carbon fibers (rCF) represent an inexpensive alternative to virgin carbon fibers (CF) but the mechanical improvement brought by rCF to polymer composites is noticeably lower than that from CF. In this article we evaluate two methods of coating rCF by single walled carbon nanotubes (SWCNTs), wet and dry, and demonstrate that extremely low concentrations of SWCNTs, ∼0.03%, are sufficient to measurably improve the strength (by 16%), modulus (by 38%), and Izod impact strength (by 52%) of thermoplastic crystalline polyamide polyxylylene adipamide (MXD6) with 30% rCF. The dry method with grinding of rCF and SWCNTs works better than the wet (dip coating) method and the rCF with residual epoxy is better than purified by pyrolysis rCF. We link this improvement of the mechanical properties to the enhanced crystallization rate caused by SWCNTs, which is observed in differential scanning calorimetry (DSC).

Single‐walled Carbon Nanotubes Dispersed by CO2 Responsive Surfactants for Fabricating High Conductive Epoxy Composites

AbstractThe emerging nanomaterials single‐walled carbon nanotube (SWNTs) with large specific surface area, excellent electrical conductivity and high mechanical strength, has been used to fabricate electronic devices. However, the extremely strong π‐π interactions make SWNTs easy to agglomerate, thus limiting their application. In this work, a novel method was applied to disperse SWNTs by using rigid rosin‐based CO2 responsive surfactant rosin acid dimaleimide choline (R‐BMI‐C). When pH 10.4, SWNTs can be uniformly and stably dispersed, and at pH 6.3, SWNTs aggregated. The dispersed SWNTs was then integrated into diglycidyl ether of bis phenol A (DGEBA) to fabricate high conductive epoxy composites. Their properties were characterized by SEM, TG, high resistivity meters, etc.. The results showed that the modified SWNTs/DGEBA composites obtained an ultra‐low percolation threshold (0.025 wt.%). Compared with the original SWNTs/DGEBA composite, its tensile strength and elastic modulus were enhanced by 17 % and 96 %, respectively, when the SWNTs content was 0.5 wt.%.

Ultimate tensile behavior of short single‐wall carbon nanotube/epoxy composites and the reinforced mechanism

AbstractShort single‐wall carbon nanotubes (SWCNTs)/epoxy composites were fabricated by a procedure of cutting and functionalizing SWCNTs, dispersion and curing, with a very low weight ratio of SWCNTs from 0.03% to 0.5%. It was found that the tensile fracture strength of composites increases with increasing SWCNT content initially, then reaches a maximum at 0.05 wt% and finally decreases with further increasing the SWCNT content. The fracture strength of the composite with 0.05 wt% SWCNTs (78.46 MPa) is ~160% of that of pure epoxy sample (48.64 MPa). A model analysis based on the competition of local matrix fracture and the debonding of short SWCNT was proposed. It revealed that there is a transition from local matrix fracture to the debonding of SWCNT when the SWCNT content increases, this transition leads to the decrease in the tensile strength. Further analyses indicated that the content of carbon nanotubes (CNTs) at the transition depends on their radius and length. Considering the effect of surface cracks on the fracture strength of pure epoxy sample, the theoretical analyses are qualitatively in agreement with the experimental results. The present study partly explains why the fracture strength of CNT reinforced composites has various results for a similar CNT loading in previous works.

Selective growth of metallic single-walled carbon nanotubes via the application of high magnetic fields of 10 T

The structure of carbon materials can be controlled using a magnetic field, enhancing their functional properties. Most of the magnetic-field effects on carbon material growth were found to originate from the magnetic-field orientation. However, we observed that the magnetic-field orientation did not affect the growth of single-walled carbon nanotubes (SWCNTs); instead, under a magnetic field of 10 T, the preferential growth of metallic SWCNTs (1-nm diameter) was observed using chemical vapor deposition and liquid decomposition, suggesting chirality selectivity. Raman and X-ray photoelectron spectra showed that the defect structure and oxygen content of SWCNTs increased with increasing magnetic-field intensity. Therefore, thin metallic nanotubes can be selectively grown by applying a high magnetic field in environments where nanotubes are relatively difficult to form.

Ternary PM6:Y6 Solar Cells with Single‐Walled Carbon Nanotubes

An organic solar cell with single‐walled carbon nanotubes (SWCNTs) in the photoactive layer is typically a type II heterojunction with the semiconducting SWCNTs acting as the electron donor and C60 or other fullerene derivatives as the acceptor. Herein, the performance of solar cells consisting of (6,5) SWCNTs combined with C60 and three nonfullerene acceptors is evaluated in a bilayer architecture. SWCNTs are then combined with the donor/acceptor PM6:Y6 in a ternary mixture and both bulk heterojunction and bilayer devices are fabricated. The SWCNTs are found to extend the light absorption of PM6:Y6 solar cells into the infrared but their use must strike a balance between the SWCNT concentration to enhance light absorption and solvent‐induced changes to the morphology of the active layer.

Highly individual single-walled carbon nanotubes synthesized by floating catalyst chemical vapor deposition for transparent conducting films

The bundle formation of single-walled carbon nanotubes (SWCNTs) has dramatically hindered their performances of transparent conducting films (TCFs). Herein, we synthesized less bundled SWCNTs by reducing the concentration of catalyst precursor in floating catalyst chemical vapor deposition. The gas-phase number concentration of SWCNTs could be reduced from 1.6×106 to 4×105 cm−3 by decreasing the catalyst precursor and thus, the bundle formation due to nanotube collisions induced by Brownian diffusion was significantly inhibited. ∼42% of SWCNTs were found to be individual with a mean tube diameter of 1.0 nm, mean length of 2.5 μm and mean bundle diameter of 2.1 nm, the corresponding SWCNT TCF exhibited a sheet resistance of 109 Ω/sq. at 90% optical transmittance. Our work provides a strategy of synthesizing highly individual SWCNTs for enhanced performance of TCFs, implying great potential in electronic applications.

Commercial carbon nanotube as rear contacts for industrial p-type silicon solar cells with an efficiency exceeding 23%

Commercially available single wall carbon nanotube (SWCNT) soots are combined with an organic passivation scheme and shown to be an efficient rear contact and alternative to ALD-Al2O3/PECVD-SiNx/laser treatment in conventional passivated emitter and rear cell (PERC) solar cells. Both low carbonaceous purity 60–70% and 95% SWCNTs are tested and a power conversion efficiency of over 23% is demonstrated. The approach is simple, scalable and completely eliminates the metal-semiconductor contact known to cause high interfacial recombination in PERC technology. A low reverse saturation current density (J0) is achieved by varying the concentration and species of SWCNTs used and a full-area back surface field on an industrial sized (275.54 cm2) solar cell is obtained.

Binder-free, pre-consolidated single-walled carbon nanotubes for manufacturing thermoset nanocomposites

In this work, we propose a pre-consolidated form of single-walled carbon nanotubes (SWCNT) – SWCNT briquettes – as a binder-free, robust, and safe material for manufacturing electrically and thermally conductive thermoset nanocomposites with universal applicability to all polymer matrices. We prove that the briquettes provide similar performance in nanocomposites compared to reference samples: a pristine powder, a commercial masterbatch and an aerogel based on the same type of SWCNTs. Using comprehensive sets of methods, we observe no significant differences in electrical (∼10−7-1 S/cm depending on SWCNT loading) and thermal (0.210–0.304 W/mK) conductivities for all sample types across a wide range of SWCNT concentrations. Moreover, the percolation thresholds of nanocomposites for SWCNT briquettes were ultra-low and close to that of pre-dispersed masterbatches (0.001–0.003 wt%). Pre-consolidated SWCNT powder is shown to provide the same final functional properties, while being free from common nanotube drawbacks such as the higher price of masterbatch manufacturing or aerosolization and low dispersibility during handling for the SWCNT powder/aerogel. The briquettes not only offer a safe solution for large scale fabrication, cutting away the need for personal and facility level safety measures, but do so at no significant cost increase, can be used with any polymer matrix and associated industrial processing route without any loss of final properties. This makes them universally attractive for all composite industrial production as well as small scale low capital laboratories.

Single-walled carbon nanotubes protect photosynthetic reactions in Chlamydomonas reinhardtii against photoinhibition

Single-walled carbon nanotubes (SWCNTs) are among the most exploited carbon allotropes in nanosensing, bioengineering, and photobiological applications, however, the interactions of nanotubes with the photosynthetic process and structures are still poorly understood. We found that SWCNTs are not toxic to the photosynthetic apparatus of the model unicellular alga Chlamydomonas reinhardtii and demonstrate that this carbon nanomaterial can protect algal photosynthesis against photoinhibition. The results show that the inherent phytotoxicity of the nanotubes may be overcome by an intentional selection of nanomaterial characteristics. A low concentration (2 μg mL−1) of well-dispersed, purified and small SWCNTs did not alter the growth and pigment accumulation of the cultures. Indeed, under the photoinhibitory conditions of our experiments, SWCNT-enriched samples were characterized by a lower rate of PSII inactivation, reduced excitation pressure in PSII, a higher rate of photosynthetic electron transport, and an increased non-photochemical quenching in comparison with the controls. In addition, SWCNTs change the distribution of energy between the photosystems in favour of PSII (state 1). The underlying mechanism of this action is not yet understood but possibly, electrons or energy can be exchanged between the redox active nanotubes and photosynthetic components, and probably other redox active intra-chloroplast constituents. Alternatively, nanotubes may promote the formation of an NPQ conformation of PSII. Our results provided evidence for such electron/energy transfer from photosynthetic structures toward the nanotubes. The discovered photoprotective effects can potentially be used in photobiotechnology to maintain the photosynthetic activity of microorganisms under unfavourable conditions.