Dispersion Of Single-walled Carbon Nanotubes Research Articles

In vitro and in vivo modulation of Hematopoietic Stem Cell (HSCs) differentiation into T and B cells by poly dispersed acid-functionalized single-walled carbon nanotubes (AF-SWCNTs)

Abstract Background AF-SWCNTs are known to have significant effect on the immune function. There is not much information available on the effect of carbon nanotubes (CNTs) on the differentiation of the HSCs. In the present study we have focused on studying the modulatory effects of AF-SWCNTs on the differentiation of HSCs into T & B cells. Methods Single-walled CNTs were acid-functionalized by treating with concentrated sulfuric & nitric acid; thus, tagged with Alexa Fluor 633 to get fluorescent AF-SWCNTs (FAF-SWCNTs). To study internalization, magnetic beads enriched C57bl/6 mouse bone marrow (BM) HSCs (Lin− Sca1+cKit+) were incubated with FAF-SWCNTs & studied using flow cytometry & confocal microscopy. HSCs were cultured with a cocktail of cytokines to induce differentiation to T & B cells, in (+/−) AF-SWCNTs & monitored by live cell imaging. For in vivo ontogenesis study, mice were lethally irradiated (gamma irradiation) & reconstituted using syngeneic BM cells pretreated (+/−) AF-SWCNTs. At different time points, appearance of T & B cells in the spleen was monitored. Results Our results indicate that HSCs internalized significant amounts of FAF-SWCNTs in vitro that remained essentially localized in cytoplasm. Differentiation of cytokines stimulated HSCs to T & B cell was significantly suppressed by AF-SWCNTs. Results of our in vivo experiments indicated that after 17th day of BM transplantation, significant numbers of T & B cells appeared in the reconstituted mouse spleen. However, when AF-SWCNTs pretreated BM cells used to reconstitute irradiated mice, significant decline in both of their percentage & absolute recovery was noted. These results indicate that CNTs may significantly modulate the differentiation of HSCs into lymphocytes.

Cardanol-derived cationic surfactants enabling the superior antibacterial activity of single-walled carbon nanotubes

Single-walled carbon nanotubes (SWCNTs) are potential antibacterial material, and their antibacterial activity in aqueous solutions depends on efficient surfactants to create strong interactions between well-dispersed SWCNTs and bacterial cells. Here, we designed and synthesized a new family of cationic surfactants by introducing different positively charged hydrophilic heads, i.e. –(CH2)6N+(CH3)3Br−, –(CH2)2N+(CH3)3Br− and –(CH2)2N+PyridineBr−, to cardanol obtained from cashew nut shell liquid. These surfactants can efficiently disperse SWCNTs in aqueous solutions because benzene rings and olefin chains in cardanol enable their strong π-stacking on SWCNTs. A much higher fraction of SWCNTs can be dispersed individually compared to the commonly used surfactant, dodecylbenzene-sulfonate sodium (SDBS). SWCNTs dispersed in the cardanol-derived surfactants demonstrate significantly improved antibacterial activity. At the concentration of 0.5 wt%, their minimum inhibitory concentration is 0.33 and 0.02 μg ml−1 against E. coli and S. aureus, respectively, which is only 0.8%–1.5% of that of SDBS-dispersed SWCNTs. The strong antibacterial activity can be attributed to both better dispersion of SWCNTs and positive charges introduced by hydrophilic heads, which are attracted to negatively charged bacterial cell surfaces. These cardanol-derived surfactants are promising as sustainable surfactants for enabling various SWCNT applications.

Dispersion quality of single-walled carbon nanotubes reveals the recognition sequence of DNA

The specific recognition between DNA and single-walled carbon nanotubes (SWCNTs) has enabled wide applications, especially in the chiral sorting of SWCNTs. However, the molecular recognition mechanism has not been fully understood. In our work, various DNA–SWCNT dispersions were prepared by the ultrasonic dispersion method, and characterized by UV absorption spectroscopy, fluorescence emission spectroscopy, zeta potential measurement, SDBS exchange kinetics and computer simulation. The effect of DNA sequence on the structure and properties of hybrid molecules was analyzed. Data analysis showed that DNA with specific recognition had better dispersion quality of the corresponding SWCNT, which means that higher content of monodispersed SWCNTs was obtained. The high-quality dispersion of the DNA–SWCNT pair was attributed to the stronger binding between DNA and SWCNT, resulting in a tighter conformation of DNA on the SWCNT surface and a larger zeta potential of DNA–SWCNT hybrids. Consequently, DNA–SWCNT dispersions of the recognition pair exhibited better stability against salt and stronger fluorescence emission intensity. However, the correlation between specific recognition and DNA coverage on SWCNT was not observed. This work gives more insight into the recognition mechanism between DNA and SWCNTs.

Modeling of Single-Walled Carbon Nanotube Binding to Nitric Oxide Synthase and Guanylate Cyclase Molecular Structures

Previously, we have demonstrated that water dispersible single-walled carbon nanotubes (SWCNTs) may be used in low therapeutic doses in antihypertensive therapy as promising agents capable of activating constitutive nitric oxide synthase (NOS) in spontaneously hypertensive rats, thus increasing the NO production in central and peripheral elements of the cardiovascular system [1]. Here we confirm this effect by docking and molecular dynamics simulations, clearly showing that SWCNTs may interact with NOS and guanylate cyclase molecular structures.

Composite Interlayer Consisting of Alcohol-Soluble Polyfluorene and Carbon Nanotubes for Efficient Polymer Solar Cells.

We report the synthesis of composite interlayers using alcohol-soluble polyfluorene (ASP)-wrapped single-walled carbon nanotubes (SWNTs) and their application as electron-transport layers for efficient organic solar cells. The ASP enables the individual dispersion of SWNTs in solution. The ASP-wrapped SWNT solutions are stable for 54 days without any aggregation or precipitation, indicating their very high dispersion stability. Using the ASP-wrapped SWNTs as a cathode interlayer on zinc oxide nanoparticles (ZnO NPs), a power conversion efficiency of 9.45% is obtained in PTB7-th:PC71BM-based organic solar cells, which is mainly attributed to the improvement in the short circuit current. Performance enhancements of 18 and 17% are achieved compared to those of pure ZnO NPs and ASP on ZnO NPs, respectively. In addition, the composite interlayer is applied to non-fullerene-based photovoltaics with PM6:Y6, resulting in a power conversion efficiency of up to 14.37%. The type of SWNT (e.g., in terms of diameter range and length) is not critical to the improvement in the charge-transport properties. A low density of SWNTs in the film (∼1 SWNTs/μm2 for ASP-wrapped SWNTs) has a significant influence on the charge transport in solar cells. The improvement in the performance of the solar cell is attributed to the increased internal quantum efficiency, balanced mobility between electrons and holes, and minimized charge recombination.

Comparison of Attachment and Antibacterial Activity of Covalent and Noncovalent Lysozyme-Functionalized Single-Walled Carbon Nanotubes.

Carbon nanotube–lysozyme (LSZ) conjugates provide an attractive combination of high strength and antimicrobial activity. However, there has not been a direct comparison of the covalent and noncovalent methods for creating them. In this work, single-walled carbon nanotubes (SWNT) were functionalized with LSZ using both noncovalent adsorption and covalent attachment via N-ethyl-N-(3-dimethylamino-propyl) carbodiimide hydrochloride–N-hydroxysuccinimide (EDC–NHS) chemistry. The amount of attached lysozyme, dispersion stability, and antimicrobial activity was compared. In addition, the mechanical properties of LSZ–SWNT in poly(vinyl alcohol) (PVA) composite films were investigated. Dispersions of covalently bound LSZ–SWNT had better dispersion stability. This was attributed to covalent functionalization enabling sustained SWNT dispersion at a lower LSZ/SWNT ratio. The covalently bound LSZ–SWNT also exhibited a lower initial rate of antibacterial response but were active over a longer time scale. Composite films made from LSZ–SWNT maintained similar activity as the corresponding dispersions. However, the noncovalent LSZ–SWNT films were stronger and more hydrolytically stable than those made from covalent LSZ–SWNT.

Dispersion of arc-discharged single-walled carbon nanotubes using the natural α-amino acid derivative N-dodecanoyl leucinate.

The natural α-amino acid derivate N-dodecanoyl leucinate was synthesized via Schotten–Baumann reaction and alkali treatment, and was applied to the dispersion of arc-discharged single-walled carbon nanotubes (SWNTs). Optical absorption and Raman scattering spectra as well as AFM observation confirmed the effective individualization and selective dispersion of SWNTs. Moreover, charge transfer from N-dodecanoyl leucinate to SWNTs was evidenced by FT-IR and Raman scattering spectroscopic analyses. We believe that the formation of a charge transfer complex between dispersants and SWNTs is responsible for the effective individualization of SWNTs, and that the charge transfer from dispersants to SWNTs (or from SWNTs to dispersants) is crucial for selective dispersion of semiconducting (or metallic) SWNTs.

Humic acid assisted stabilization of dispersed single-walled carbon nanotubes in cementitious composites

AbstractSignificant research has been done in recent decades in the field of the dispersion of carbon nanotubes in aqueous solutions and the reinforcement of ordinary Portland cement (OPC). However, the cementitious mixture, as an alkaline environment, easily leads to the re-agglomeration of dispersed single-walled carbon nanotubes (SWCNTs) and influences their enhancing effects. Humic acid (HA) is a type of natural organic matter which can assist the stabilization of dispersed single-walled carbon nanotubes in cementitious composites. The present study characterizes the influence of HA in stabilizing the dispersion of SWCNTs by means of ultraviolet spectrophotometer tests. The fluidity of fresh cement slurry and mechanical performance of hardened OPC pastes were measured to better illustrate the dispersion of SWCNTs in real cement composites. The results not only reveal that the addition of an alkaline environment to the SWCNT suspensions results in a rapid decrease of the dispersion, but also suggest that the appropriate content of HA (0.12 wt.%) can play a significant role in stabilizing the dispersion of SWCNTs. When the mixed hybrid of SWCNTs and HA with a concentration of HA/c equal to 0.05 wt.% is used, the fluidity of the fresh cement slurry experiences a maximum decline and this mixture content of materials will dramatically increase the compressive and flexural strength by about 31% and 48%, which indicates that more SWCNTs are in a dispersed state under this concentration. SEM images further prove that a suitable HA/c can inhibit the expansion of cracks in the cementitious composites.

Carbon nanotube-based mixed-matrix membranes with supramolecularly engineered interface for enhanced gas separation performance

In this study, novel nanocomposite membranes were fabricated from single-walled carbon nanotubes (SWNTs) and a triptycene-containing polyimide. The desirable interfacial morphology and homogenous dispersion of SWNTs were achieved by strong π-π stacking and supramolecular shape-fitting interactions between the nanotube and the paddlewheel-shaped triptycene moieties in polymer matrix. Mixed-matrix membranes (MMMs) containing 2–15 wt% of as-purchased SWNTs (AP-SWNTs) were prepared and tested for their gas transport properties. While all MMMs showed greatly enhanced permeabilities with well-maintained selectivities, a non-linear dependence of permeability on filler content was observed. Another series of MMMs with purified SWNTs (P-SWNTs) and acid-treated SWNT (A-SWNTs) were also prepared. The functionalized A-SWNT MMM exhibited the best separation performance at 2 wt% filler content among all MMMs, which can be attributed to the improved interfacial affinity with carboxylic acid functionalized surface of A-SWNTs.

Dispersion of Metallic Arc-discharged Single-walled Carbon Nanotubes by Two Polysilane Derivatives

Dispersion of Metallic Arc-discharged Single-walled Carbon Nanotubes by Two Polysilane Derivatives

Aqueous Dispersion of Single-Walled Carbon Nanotubes Using Tetra-Phenyl Bimesitylene Derivative via Noncovalent Modification and Improved Antimicrobial Activity.

Tetra-arylbimesityl derivative containing carboxylic groups have successfully been utilized in dispersing single-walled carbon nanotubes (SWNTs) in aqueous solutions through sonication and centrifugation procedures. The dispersion process and the characterization of final stabilized SWNTs were accomplished using analytical techniques, providing sufficient evidences on the preparation of the dispersed SWNTs in water. All the prepared SWNT water dispersions were evaluated for antimicrobial activity against three different reference strains namely Escherichia coli, Staphylococcus aureus and Candida albicans, and have shown considerable selective activity against the Gram-positive strain Staphylococcus aureus.

Excellent dispersibility of single-walled carbon nanotubes in highly concentrated electrolytes and application to gel electrode for Li-S batteries

The high dispersibility of single-walled carbon nanotubes (SWCNTs) in supporting media is a challenge for maximizing the mechanical and electrical properties of SWCNT-based composite materials. Herein, we demonstrate that highly concentrated lithium-salt electrolytes (HCEs) can disperse SWCNTs without using any other dispersing agents. Incorporating SWCNT-dispersed HCEs into a polymer matrix allows the fabrication of mechanically stable, electronically and ionically (Li+) conductive composite gels. Due to its high electronic conductivity and good dispersion of the electrolyte, the SWCNT/HCE composite gel is a promising electrode material for energy storage devices. As a demonstration, the composite gel is applied as a gel cathode for a Li-sulfur battery by incorporating molecular sulfur into the gel, resulting in stable cycling performance.

Square Wave Voltammetric (SWV) Determination of Quercetin in Tea Samples at a Single-Walled Carbon Nanotube (SWCNT) Modified Glassy Carbon Electrode (GCE)

The voltammetric determination of quercetin in tea samples was performed at a modified sensor which was fabricated by the addition of a single-walled carbon nanotube dispersion on a glassy carbon electrode. Due to the electrochemcal activity of quercetin, electroanalytical methods were used with great success for the determination of quercetin. The electrochemical properties of quercetin were investigated. Quercetin in water and methanol extracts of tea samples were determined at the modified glassy carbon electrode by using square wave voltammetry. The results were found to be 116.4 and 116.3 µg quercetin equivalent/g dry green tea, 127.9 and 104.24 µg quercetin equivalent/g dry basil tea 27.5 and 26.1 µg quercetin equivalent/g dry black tea. The limit of detection and limit of quantification values for quercetin for the 0.01 to 100 µM concentration range were 7.7 nM and 25.6 nM, respectively. Very low concentrations of quercetin were successfully determined by square wave voltammetry with sensitivity and selectivity.

Hybrids of CO2-Responsive Water-Redispersible Single-Walled Carbon Nanotubes by a Surfactant Based on Natural Rosin.

A kind of polymerizable dispersant based on natural rosin was used to disperse single-walled carbon nanotubes (SWNTs) in aqueous solution followed by in situ free-radical polymerization to achieve a controllable SWNTs dispersion, that not only can be controlled by CO2/N2, but can also be recycled and redispersed in CO2-saturated water after drying without sonication.

Highly flexible all-nonwoven piezoelectric generators based on electrospun poly(vinylidene fluoride)

Acoustic energy is a sustainable and clean form of energy that is always being generated and wasted in our environment. Acoustic energy harvesting technology is a very promising substitute for fossil fuels and can serve as a suitable power supply for small electronic devices, owing to the high efficiency of piezoelectric devices. Thus, many studies have investigated the conversion of sound energy into electricity for power generation. In this study, we successfully fabricated an all-nonwoven polymer-based piezoelectric generator with a high acoustic energy conversion efficiency and high flexibility. A dispersion of single-walled carbon nanotubes (SWCNTs) was sprayed onto electrospun poly(vinylidene fluoride) (PVDF) webs to produce flexible and durable electrodes. The thickness and flexibility of the PVDF web used as the active piezoelectric layer were controlled by the spinning time. The effect of flexibility on frequency response, sound pressure response, output power, and energy harvesting characteristics was investigated by observing sound wave-induced vibration behavior and evaluating the output characteristics of the generators. The all-nonwoven polymer-based generator with the highest flexibility showed the highest output voltage overall due to its excellent vibration characteristics. Due to its effectiveness and durability suitable for acoustic energy harvesting, this all-nonwoven polymer-based generator can be useful for a wide range of applications, such as wearable electronics and large area flexible devices.

Swelling and electrical properties of LLDPE reinforced by SWCNTs nanocomposites for radiation and sensors applications

Linear low-density polyethylene (LLDPE) incorporated with single-walled carbon nanotubes (SWCNTs) by mistreatment casting technique. The result of various weight percentage loadings of SWCNTs on the swelling and electrical properties of LLDPE/SWCNTs nanocomposite also γ-irradiation effects had been investigated. It was found that, at low concentration, it uniformly disperses into an LLDPE matrix and provides LLDPE/SWCNTs nanocomposites with abundant improved electrical properties by nine orders of magnitude. Positive temperature coefficient of conductivity (PTCC)/negative temperature coefficient of conductivity (NTCC) was affected by the SWCNT contents. Transmission electron microscopy and scanning electron microscope techniques were used to investigate the dispersion of SWCNTs in the LLDPE matrix. Linear exceptional modification within direct current electrical conduction of percolative threshold-loaded LLDPE as a perform of γ-irradiation dose will be used as a nontoxic, easy, inexpensive, and sensitive method to evaluate the irradiation dose in range 10 Gy–1 kGy also can be used in fabrication of firing sensors with various ranges of temperatures.

Measuring the Accessible Surface Area within the Nanoparticle Corona Using Molecular Probe Adsorption.

The corona phase-the adsorbed layer of polymer, surfactant, or stabilizer molecules around a nanoparticle-is typically utilized to disperse nanoparticles into a solution or solid phase. However, this phase also controls molecular access to the nanoparticle surface, a property important for catalytic activity and sensor applications. Unfortunately, few methods can directly probe the structure of this corona phase, which is subcategorized as either a hard, immobile corona or a soft, transient corona in exchange with components in the bulk solution. In this work, we introduce a molecular probe adsorption (MPA) method for measuring the accessible nanoparticle surface area using a titration of a quenchable fluorescent molecule. For example, riboflavin is utilized to measure the surface area of gold nanoparticle standards, as well as corona phases on dispersed single-walled carbon nanotubes and graphene sheets. A material balance on the titration yields certain surface coverage parameters, including the ratio of the surface area to dissociation constant of the fluorophore, q/KD, as well as KD itself. Uncertainty, precision, and the correlation of these parameters across different experimental systems, preparations, and modalities are all discussed. Using MPA across a series of corona phases, we find that the Gibbs free energy of probe binding scales inversely with the cube root of surface area, q. In this way, MPA is the only technique to date capable of discerning critical structure-property relationships for such nanoparticle surface phases. Hence, MPA is a rapid quantitative technique that should prove useful for elucidating corona structure for nanoparticles across different systems.

The critical effect of electrodes components mixing on efficiency of anode material for lithium-ion batteries

An investigation is attempted to highlight the importance of electrode preparation. Graphite carbon (GC), SnO2 and single wall carbon nanotubes (SWCNT) were used as components of anode catalyst for lithium-ion batteries. For mixing these materials, two common processes were performed: ball milling of GC + SnO2+ SWCNT and dispersion of SWCNT in GC-SnO2. The composite electrode prepared from dispersion step presented a superior performance, due the formation of porous and hollow microstructure, which provides more lithium storage sites, shorter Li+ diffusion length and sufficient void space.

Improving mechanical properties of PVA based nano composite using aligned single-wall carbon nanotubes

The fabrication and characterization of PVA films reinforced with single-wall carbon nanotubes (SWNTs) and Fe2O3 nanoparticles were investigated. The composite made with sodium dodecylbenzene sulfonate (NaDDBS) dispersed SWNTs at a 4 wt% loading percentage demonstrated good dispersion and resulted in the highest tensile strength (97 MPa) of all the SWNT reinforced films tested, and a 21% increase compared to the neat PVA film (80 MPa). The study revealed that with 10 wt% of NaDDBS, only 10–20 min of sonication was necessary to obtain uniform and stable SWNT dispersion in water. Moreover, applying a magnetic field (H = 0.12 kG) to the composite film to align the SWNTs resulted in a tensile strength of 106.4 MPa. Using 5 wt% of Fe2O3 the tensile strength increased to 115 MPa after exposing the composite film to the magnetic field for 60 min during the drying process to align the carbon nanotubes. In addition, the tensile property of the composites was enhanced by annealing the polymer composites in a vacuum oven at 75 °C for 2 h.

Intrinsically disordered protein as carbon nanotube dispersant: How dynamic interactions lead to excellent colloidal stability

The rich pool of protein conformations combined with the dimensions and properties of carbon nanotubes create new possibilities in functional materials and nanomedicine. Here, the intrinsically disordered protein α-synuclein is explored as a dispersant of single-walled carbon nanotubes (SWNTs) in water. We use a range of spectroscopic methods to quantify the amount of dispersed SWNT and to elucidate the binding mode of α-synuclein to SWNT. The dispersion ability of α-synuclein is good even with mild sonication and the obtained dispersion is very stable over time. The whole polypeptide chain is involved in the interaction accompanied by a fraction of the chain changing into a helical structure upon binding. Similar to other dispersants, we observe that only a small fraction (15–20%) of α-synuclein is adsorbed on the SWNT surface with an average residence time below 10 ms.