Single-walled Carbon Nanotubes In Water Research Articles

Novel synthesis of thermoresponsive single-walled carbon nanotubes/poly(N-isopropylacrylamide) hybrids

Poly(N-isopropylacrylamide) (PNIPAM) is one of the most well studied thermoresponsive polymers and its microgels undergo a reversible volume phase transition (VPT) at temperatures close to that of the human body. Coupling this property with the unique optical properties of single-walled carbon nanotubes (SWCNT) in the near infrared (NIR) leads to interesting nanohybrids that could be used as multi-responsive sensors/actuators for biological applications.We show the synthesis of thermoresponsive SWCNT/PNIPAM hybrids using two different non-covalent strategies, preserving the nanotube optical properties such as fluorescence. The first strategy involves the dispersion of the SWCNT in water with sodium dodecyl sulfate (SDS), and subsequent in situ synthesis of PNIPAM microgels inside the SDS coatings around the nanotubes. The second strategy starts with modifying the nanotubes with a pyrene derivative, which in turn is used as the starting point for the in situ polymerization of the PNIPAM microgels, thus ensuring that the polymer grows around the nanotubes. In both cases, we obtain hybrids showing a phase transition at temperatures close to that of the human body, with the absorption and fluorescence spectra of the hybrids in the NIR changing in response to the changing dielectric environment. These systems could be used as actuators/sensors in biological systems.

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.

Peptide-Encapsulated Single-Wall Carbon Nanotube-Based Near-Infrared Optical Nose for Bacteria Detection and Classification

Sense of smell has been used as a diagnostic tool for almost entire human history. While successful examples of the use of the human nose for diagnostics are rare in modern history, there are ample reports of use of animals to diagnose various medical conditions. Bacterial infections often result in strong odors. In recent years, electronic noses (e-nose) and optical noses (o-nose) are of high interest in diagnostics and classification of bacterial infections. Artificial olfactory sensors can perform noninvasively, immediately at the point of care, do not require extensive sample handling, and promise to be highly cost-effective. This manuscript demonstrates the development of a near-infrared optical sniffer comprised of peptide-encapsulated (6,5) single-wall carbon nanotubes (SWCNTs) for bacteria detection and classification. Sixteen different peptides that include tyrosine in different proportions and positions were synthesized. The ability of these peptides to disperse SWCNTs in water was tested, and the intensity of the resultant optical signal was evaluated. Overall, longer peptides provided better dispersion as compared to shorter peptides. Addition of the fluorenylmethyloxycarbonyl chloride (Fmoc) group to positively charged peptides tested in the current study significantly improved SWCNT dispersion and signal intensity. The sensors successfully distinguished between the odor of sterile growth medium, Escherichia coli, and Klebsiella pneumoniae. Moreover, we demonstrated the possibility of using the developed sensors for antibiotics susceptibility testing. The sensors provided results in real-time, enabled multiple-usage, and operated at room temperature.

Dispersion of single-walled carbon nanotubes in water in presence of Direct Current field

Dispersion of single-walled carbon nanotubes in water in presence of Direct Current field

Visible near Infrared Spectroscopic Evidence of the Purification and Dispersion of Single-Walled Carbon Nanotubes

The application of dispersible single-walled carbon nanotubes in water is required in many fields, such as mechanics, thermology, electricity, etc. In this paper, single-walled carbon nanotube samples were dispersed in sodium deoxycholate aqueous solution with the assistance of ultrasonic crushing. The effects of centrifugal time, concentration and centrifugal velocity on dispersion were investigated. After centrifugal separation, the dispersible single-walled carbon nanotubes solution in water was obtained. The dispersion behavior of single-walled carbon nanotubes in sodium deoxycholate aqueous solution was further investigated by Uv-visible near infrared spectrum and electrochemical cyclic voltammetry curve. At the same time, characterization results of Uv-visible near infrared spectrum shew that the purity of single-walled carbon nanotubes was improved. The cyclic voltammetry curves of single-walled carbon nanotubes after purification and dispersion were tested by electrochemical method, and the electron transfer behavior of single-walled carbon nanotubes after purification and dispersion was investigated.

Surface Coating- and Light-Controlled Oxygen Doping of Carbon Nanotubes

Tuning the optical properties of single-wall carbon nanotubes (SWCNTs) via oxygen doping has been a simple and effective approach to create fluorescent quantum emitters. We performed oxygen doping of SWCNTs in water utilizing chirality-pure (6,5) enantiomers with different surface coatings of DNA and surfactants by ultraviolet (UV) light irradiation. We found the reaction to be primarily dependent on the wavelength of UV light and the specific coating material on the nanotube surface. Particularly, DNA coatings react more readily with the reactive oxygen species that is photochemically produced under short-wavelength UV light than SWCNTs, preventing oxygen doping of nanotubes from occurring. The surface coverage of SWCNTs created by coating materials plays a weaker role in controlling the reaction efficiency of oxygen doping. This is demonstrated clearly by the lack of oxygen doping for two (6,5) enantiomers wrapped by DNA with drastically different surface coverages. These findings reveal important mechanisms of oxygen doping of SWCNTs, providing methods of controlling optical properties of nanotubes for developing unique applications.

Deep Eutectic Solvent Assisted Dispersion of Carbon Nanotubes in Water.

Deep Eutectic Solvents (DESs) are emerging as a promising medium for many chemical processes. They can be used to observe specific properties required for nanomaterials' applications. Controlled CO2 adsorption requires disaggregation of carbon nanotubes into smaller bundles which can be accomplished by dispersing them in aqueous DES system. In this study, response surface methodology (RSM) was adopted to examine the impacts of three important factors on the dispersion of single walled carbon nanotubes (SWNTs) in Choline Chloride-Glycerol (ChCl-Gly) DES; (i) ChCl-Gly (mass% in water), (ii) sonication energy input (J/mL), and (iii) SWNTs' concentration (mg/L). The net negative surface charge of ChCl-Gly, a “green solvent,” provided superior dispersion of inherently negatively charged SWNTs in water via electrostatic repulsion. The impacts of the dispersion factors were quantified by the average aggregate diameter (nm) and polydispersity (polydispersity index, PDI) of SWNTs in aqueous-DES systems. Models were developed, experimentally verified, and statistically validated to map the impacts of these factors and to obtain optimized dispersions. The optimized dispersions, characterized by the small (<100 nm) and uniform (<0.1 PDI) SWNTs' aggregates, were achieved at lower sonication energy costs which can have promising implications across many nano-manufacturing fields. The dispersion/aggregation mechanism was proposed using COSMO-RS (based on equilibrium thermodynamics and quantum chemistry) modeling of ChCl-Gly and zeta potential measurements of SWNTs. This understanding will help create optimally sustainable and economically feasible DES-nanomaterial dispersions.

Conductive Nanocomposite Cotton Thread Strands for Wire and Industrial Applications

This paper reports the synthesis of conducting cotton thread strands obtained by dip coating in sodium dodecyl-benzene sulfonate (SDBS) surfactant with dispersed single-walled carbon nanotubes (SWCNT), as a promising candidate for energy storage applications. The effect of the dispersion and SDBS in the dissolved SWCNT solution was detected using field emission scanning electron microscopy (FE-SEM) and x-ray diffraction (XRD). XRD confirms that there was good dispersion of SWCNTs on the cotton thread strands obtained by doping employing ethylene glycol (EG) which lowers the corrugation of the cotton thread. FE-SEM images obtained at different magnifications show micro-fibril structure. Energy dispersive x-ray (EDX) analysis confirms the presence of only C, Na and S, ruling out the presence of any elemental impurity. A strong decrease from 3.587Ω to 0.01257Ω in electrical resistance was observed when the concentration of SWCNTs was increased from 0.008049 wt.% to 1.07269 wt.%, indicating that the SWCNTs induced conductive properties in the cotton thread strands. The study shows that sodium dodecyl benzyl sulfonate (SDBS) has the best dispersion of single-walled carbon nanotubes in water when used along with ethylene glycol. The results show that the coated threads can have great industrial applications as conduction wire substitute.

Carbohydrate- and Chain Length-Controlled Complexation of Carbon Nanotubes by Glycopolymers.

Stable dispersions of single-wall carbon nanotubes (SWCNTs) by biopolymers in an aqueous environment facilitate their potential biological and biomedical applications. In this report, we investigated a small library of precision synthesized glycopolymers with monosaccharide and disaccharide groups for stabilizing SWCNTs via noncovalent complexation in aqueous conditions. Among the glycopolymers tested, disaccharide lactose-containing glycopolymers demonstrate effective stabilization of SWCNTs in water, which strongly depends on carbohydrate density and polymer chain length as well. The introduction of disaccharide lactose potentially makes glycopolymers less flexible as compared to those containing monosaccharide and facilitates the wrapping conformation of polymers on the surface of SWCNTs while preserving intrinsic photoluminescence of nanotubes in the near-infrared region. This work demonstrates the synergistic effects of the identity of carbohydrate pendant groups and polymer chain length of glycopolymers on stabilizing SWCNTs in water, which has not been achieved previously.

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.

(Invited) Step-Wise Molecular Self-Assembly on Single-Wall Carbon Nanotube Networks: Towards Development of Delivery Systems of Highly Potent but Difficult to Administer Drugs

Single-walled carbon nanotubes (SWCNTs) are increasingly being investigated for biomedical imaging, sensing, and drug delivery. Individual dispersion and coating with biocompatible molecules of SWCNTs are essential to avoid triggering cytotoxicity and to realize these applications. Perhaps the most common method for generating SWCNT-based drug delivery systems involves individually dispersing SWCNTs in water with various biocompatible molecules such as DNA, biopolymers and proteins followed by linking drugs and targeting moieties to the biocompatible coating. Another relatively less frequently exploited approach entails first attaching drugs to SWCNTs and then dispersing with biocompatible molecules, which may also be targetable. Unfortunately, both approaches suffer from low SWCNT dispersion yield and inadequate control of drug loading process, particularly if the drugs are highly potent and difficult to administer. We have developed an extremely facile scheme to generate SWCNT-based drug delivery systems by controllably depositing biocompatible molecules and drugs on preformed SWCNT hydrogels. We first individually dispersed SWCNTs in water using suitable surfactant molecules, concentrated the dispersion to form freestanding hydrogels, and then removed the surfactant from the hydrogel. These surfactant-free SWCNT hydrogels comprise of three-dimensional, isotropic network of individual nanotubes held together via van der Waals interactions the junctions between nanotubes, and have >99% porosity, which allows unimpeded transport of biocompatible molecules and drugs. Furthermore, since many potent drugs are only soluble in non-aqueous solvents, water in the hydrogel can be easily exchanged with other suitable solvents to facilitate drug loading. As a proof-of-concept, we coated SWCNTs within the hydrogels first with drugs such as Doxorubicin, Bleomycin, and Digoxin, then with proteins such as albumins, and lastly dispersed in water through gentle 5 minutes sonication with little or no loss of SWCNT yield. Optical characterizations and imaging show that the albumin/drug/SWCNTs complexes are individually dispersed that the cells readily uptake. To demonstrate robustness of this approach, we coated SWCNTs with polymers prior to decorating with biomolecules/drug layers; the polymer coating was chosen to assist in rapid drug release after cell uptake. Overall, this approach allows precisely controlled, step-wise molecular self-assembly on SWCNTs of any drug and biomolecule combinations, suggesting high potential for development of multifunctional drug delivery platforms utilizing SWCNTs.

(Invited) Sequence-Dependent Stability and Fate of DNA-Wrapped Single-Walled Carbon Nanotubes in Mammalian Cells

The intrinsic fluorescence of single-walled carbon nanotubes (SWCNTs), which exhibits exceptional photostability, near-infrared (NIR) tissue-penetrating emission, and microenvironmental sensitivity, makes them ideal candidates for a variety of biomedical imaging and sensing applications. Single-stranded DNA was found to disperse SWCNTs in water and enable their uptake into mammalian cells through an energy-dependent endocytosis mechanism. Here, we show that the NIR fluorescence behavior and subsequent stability of DNA-wrapped SWCNTs are dictated by the DNA sequence upon entry to cells. We further show that these effects are highly cell-type dependent. Future work includes the development of a cellular uptake and expulsion model that accounts for the sequence-dependent aggregation of SWCNTs.

Quantification of the Number of Adsorbed DNA Molecules on Single-Walled Carbon Nanotubes

Single-walled carbon nanotubes (SWCNTs) have unique photophysical properties and promise many novel applications. Their functionalization is crucial, but the organic phase around SWCNTs is poorly understood. Noncovalent functionalization with single-stranded DNA (ssDNA) is one of the most used approaches to solubilize SWCNTs in water, and variation of ssDNA sequences leads to major advances in separation of SWCNT chiralities and SWCNT-based sensors. However, the exact number of adsorbed ssDNA molecules on ssDNA/SWCNT complexes and consequently the surface coverage are not precisely known. Here, we determine the number of adsorbed/bound ssDNA molecules per SWCNT for different ssDNA sequences. For this purpose, we directly quantify free and bound/adsorbed ssDNA and the concentration of SWCNTs using an approach based on filtration, absorption spectroscopy, and atomic force microscopy. We found that the number of adsorbed ssDNA molecules on 600 nm long (6,5)-SWCNTs varies between ∼860 for (GT)5 and ∼130 for (...

Polymeric surfactants with tricyclic rigidity from natural rosin: Synthesis and dispersion of single-walled carbon nanotubes in aqueous solution

Polymeric surfactants from natural rosin containing a unique tricyclic rigid structure were prepared and their structures were characterized by IR, 1H NMR and GPC. Their surface activities including hydrophile—lipophile balance values (HLB), emulsification properties, foaming properties, critical micelle concentration (CMC) and the minimum surface tension (γCMC) were evaluated. With the increase in ratio of hydrophobic to hydrophilic in polymeric surfactant, the CMC values of the surfactants decreased, and the emulsification and foaming properties of these surfactants increased, and the HLB values of them decreased. This type of polymeric surfactants was used to disperse single-walled carbon nanotubes (SWCNTs) in water, and their dispersal capacities were comparatively determined by UV-visible absorption spectroscopy. Thermogravimetric analysis (TGA) was used to quantify the amount of surfactant attached onto the nanotubes. More intuitive image of their dispersion states were obtained by transmission electron microscopy (TEM) and atomic force microscopy (AFM). The results showed that this type of polymeric surfactants had good dispersion capacity and dispersion stability to SWCNTs in water through strong hydrophobic attraction and weak van der Waals interactions.

DNA Origami and G-Quadruplex Hybrid Complexes Induce Size Control of Single-Walled Carbon Nanotubes via Biological Activation.

DNA self-assembly has enabled the programmable fabrication of nanoarchitectures, and these nanoarchitectures combined with nanomaterials have provided several applications. Here, we develop an approach for cutting single-walled carbon nanotubes (SWNTs) of predetermined lengths, using DNA origami and G-quadruplex hybrid complexes. This approach is based on features of DNA: (1) wrapping SWNTs with DNA to improve the dispersibility of SWNTs in water; (2) using G-quadruplex DNA to confine hemin in close proximity to SWNTs and enhance the biological activation of hydrogen peroxide by hemin; and (3) forming DNA origami platforms to allow for the precise placement of G-quadruplexes, enabling size control. These integrated features of DNA allow for temporally efficient cutting of SWNTs into desired lengths, thus expanding the availability of SWNTs for applications in the fields of nanoelectronics, nanomedicine, nanomaterials, and quantum physics, as well as in fundamental studies.

Scalable Fabrication of High-Performance Transparent Conductors Using Graphene Oxide-Stabilized Single-Walled Carbon Nanotube Inks.

Recent development in liquid-phase processing of single-walled carbon nanotubes (SWNTs) has revealed rod-coating as a promising approach for large-scale production of SWNT-based transparent conductors. Of great importance in the ink formulation is the stabilizer having excellent dispersion stability, environmental friendly and tunable rheology in the liquid state, and also can be readily removed to enhance electrical conductivity and mechanical stability. Herein we demonstrate the promise of graphene oxide (GO) as a synergistic stabilizer for SWNTs in water. SWNTs dispersed in GO is formulated into inks with homogeneous nanotube distribution, good wetting and rheological properties, and compatible with industrial rod coating practice. Microwave treatment of rod-coated films can reduce GOs and enhance electro-optical performance. The resultant films offer a sheet resistance of ~80 Ω/sq at 86% transparency, along with good mechanical flexibility. Doping the films with nitric acid can further decrease the sheet resistance to ~25 Ω/sq. Comparing with the films fabricated from typical surfactant-based SWNT inks, our films offer superior adhesion as assessed by the Scotch tape test. This study provides new insight into the selection of suitable stabilizers for functional SWNT inks with strong potential for printed electronics.

Preparation and Properties of Aqueous SCNTs Dispersion based on A UV-curable Polymeric Dispersant

A novel photosensitive copolymer P(SS-co-AA-g-GMA) (PSAG) was synthesized and utilized to noncovalently functionalize pristine single-walled carbon nanotubes (SCNTs). PSAG was highly effective for the solubilization of SCNTs in water and validated by UV-vis absorption spectra experiments, resulting in homogeneous and stable PSAG-SCNT aqueous dispersion. The microstructure of SCNTs was observed through Raman spectroscopy and transmission electron microscopy. In addition, compared with the two common polymeric dispersants of Triton X-100 and PSS, PSAG demonstrated more effective performances for dispersing SCNTs under identical conditions. Furthermore, the photosensitive PSAG-SCNTs can be crosslinked after UV irradiation, leading to significant improvement in the water resistance of SCNT films. UV-cured films can be transferred to plastic wrap to form a flexible film with high electrical conductivity.

Tip and inner walls modification of single-walled carbon nanotubes (3.5 nm diameter) and preparation of polyamide/modified CNT nanocomposite reverse osmosis membrane

ABSTRACTTo enhance the water flux and salt rejection of reverse osmosis membranes, thin film nanocomposite reverse osmosis membranes were prepared by incorporating functionalised single-walled carbon nanotubes (SWNTs). The functionalised SWNTs were obtained by chemical process such as mixed acid oxidation and substitution reaction. The SWNTs were characterised by HRTEM, FTIR, TGA, Raman spectra, UV-Vis and XPS, etc. The surface morphology and structure of membrane were characterised by SEM and contact angle measurement, respectively. The results showed that carboxyl, acyl, amide and amine were successfully grafted on the tip and inner wall of the single-walled carbon nanotubes. The dispersity of the functionalised SWNTs in water was tested, indicating a good hydrophilic property. The polyamide/modified CNT nanocomposite reverse osmosis membrane was prepared. Compared with the bare polyamide membrane, the SWNT-polyamide thin film nanocomposite membranes showed higher property in hydrophilic surface and its water flux, as along with salt rejection, improved dramatically. The experimental results revealed that the modified SWNTs (especially those containing hydrophilic groups such as carboxyl groups and amino groups) well dispersed in the polyamide thin film layer, and hence improved the water permeation, and the salt rejection.

Solubility of functionalized single-wall carbon nanotubes in water: a theoretical study

In this work, we perform an in silico functionalization of single-wall carbon nanotubes to model the apparent solubility, binding energies and to understand the dependence of such properties on the functionalization and the electronic properties. The present study is performed using two finite models of single-wall carbon nanotubes (SWCNTs), the first one is a SWCNT with metallic character and the second one is a SWCNT with semiconductor character. In addition, we use several functionalizing molecules reported in the literature: formic acid, triethylene glycol diamine, glucosamine, polyaminobenzene sulfonic acid, and polystyrene. We found that the molecule that confers a better apparent solubility to both models of SWCNTs, metallic and semiconductor, is glucosamine, due to the several hydroxyl groups in its structure, promoting a higher polarization of the system. At the same time, we found that metallic molecules promote higher polarization compared with the nonmetallic as it is observed in the electrostatic potential surfaces. Therefore, a single-wall carbon nanotube functionalized with glucosamine is suitable to show good solubility properties that can be related to a decrease in the toxicity and an increment in the biocompatibility properties.

Individually Dispersing Single-Walled Carbon Nanotubes in Water without Cutting

Single-walled carbon nanotubes (SWCNTs) are one of the most intensively studied nanomaterials due to their extraordinary mechanical, electrical and optical properties. Many fundamental studies and applications of SWCNTs, such as imaging, sensing and sorting, require SWCNTs to be dispersed in aqueous solutions first1, which is typically realized via ultrasonication in the presence of surfactants followed by ultracentrifugation2. However, due to the large energy input, ultrasonication inevitably introduces defects to SWCNTs and cuts the tubes into smaller pieces, compromising the many intriguing properties of SWCNTs3,4. Here, we show a simple method that disperses individual SWCNTs in water while retaining their lengths and avoiding introduction of defects. The as-prepared SWCNTs are 350% longer in length and 150% lower in defect density than their sonicated counterparts. These SWCNTs can also be further sorted in a chirality-specific manner. Due to the nondestructive merit of our method, the resulting full-length tubes showed a 50% increase in photoluminescence and an order of magnitude improvement in sheet conductance over those of sonicated controls. 1De Volder, M. F. L., Tawfick, S. H., Baughman, R. H. & Hart, A. J. Science 339, 535–539 (2013). 2Pagani, G., Green, M. J., Poulin, P., & Pasquali, M. Proc. Natl. Acad. Sci. 109, 11599–11604 (2012) 3Hecht, D.S., Hu, L. & Irvin, G. Advanced Materials 23, 1482-1513 (2011). 4Tabakman, S.M., Welsher, K., Hong, G. & Dai, H. The Journal of Physical Chemistry C 114, 19569-19575 (2010).