No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Abstract
Poly(aminobenzene sulfonic acid) (PABS) and polyethylene glycol (PEG) were covalently attached to single-walled carbon nanotubes (SWNTs) to form water-soluble graft copolymers. Quantitative near-IR (NIR) spectroscopic studies of these SWNT graft copolymers indicate a water solubility of about 5 mg/mL, and atomic force microscopy studies show a fairly uniform length and diameter. On the basis of thermogravimetric analysis, the loading of SWNTs in the graft copolymers is estimated to be 30% for SWNT-PABS and 71% for SWNT-PEG. NIR spectroscopic studies of SWNT-PABS show that this graft copolymer has a ground state that is a hybrid of the electronic structures of the isolated PABS and SWNT macromolecules.
... CNTs tend to occur as bundles with bundle lengths of 1-5 µm and average bundle diameters of 2-10 nm and bundle length: 500-600 nm; bundle diameter: 4-5 nm [27]. The same commercial CNTs that we used in our work were characterized in [28]. In this work P7-CNTs were obtained from commercial P3-CNTs by derivatizing with PEG to give water solubility. ...
... In this work P7-CNTs were obtained from commercial P3-CNTs by derivatizing with PEG to give water solubility. According to [28], the characterization of P7-CNTs revealed that the zeta potential of CNTs in a pH range of the soil used in our work (from pH 6 to pH 8) is about-50 mV. ...
... The following are 10 nm diameter gold nanoparticles properties obtained from [28]: polydispersity index (PDI) ≤ 0.2, core size: 8-12 nm, hydrodynamic diameter (Z): 11-25 nm; concentration of particles/mL: 5.38 × 10 12 -6.58 × 10 12 , absorption max: 510-525 nm, OD 1, zeta potential of −25.8 mV at pH 7.4 in stabilized suspension in 0.1 mM PBS (reactant free) that we used in our work [29]. ...
The aim of this work was to study the applicability of infrared spectroscopy combined with machine learning techniques to evaluate the uptake and distribution of gold nanoparticles (AuNPs) and single-walled carbon nanotubes (CNTs) in Cicer arietinum L. (chickpea). Obtained spectral data revealed that the uptake of AuNPs and CNTs by the C. arietinum seedlings’ root resulted in the accumulation of AuNPs and CNTs at stem and leaf parts, which consequently led to the heterogeneous distribution of nanoparticles. principal component analysis and support vector machine classification were applied to assess its usefulness for evaluating the results obtained using the attenuated total reflectance-Fourier transform infrared spectroscopy method of C. arietinum plant grown at different conditions. Specific wavenumbers that could classify the different nanoparticle constituents of C. arietinum plant extracts according to their ATR-FTIR spectra were identified within three specific regions: 450–503 cm−1, 750–870 cm−1, and 1022–1218 cm−1, based on larger PCA loadings of C. arietinum ATR-FTIR spectra with distinct spectral differences between samples of interest. The current work paves a path to the future fabrication strategies for AuNPs and single-walled CNTs via plant-based routes and highlights the diversity of the applications of these materials in bio-nanotechnology. These results indicate the importance of family-plant selection, choice of methods, and pathways for the efficient biomolecule delivery, drug cargo, and optimal conditions in the wide spectrum of bioapplications.
... cholesterol), and long chain organics (e.g. PEG) [39]. Acid oxidation introduces defects on the side and end of the CNT. ...
... These cause decoration of tips and sidewalls of the CNTs with oxygenated functionalities such as carboxylic, carbonyl, and hydroxyl groups. Modification via surface -COOH is very attractive because there is a plethora of chemical crosslinking agents that can use this feature [39]. These include carbodiimides, esters, and thionyl. ...
... Subsequently, they covalently attached to various types of biomolecules. Other methods include treatment with hydrogen, fluorine, and azomethine [39]. showed that functionalized carbon nanotubes have no toxicity [40]. ...
This research investigated the use of carbon nanotubes (CNTs) as a treatment to increase
the permeability of a bacterial cell wall. Recombinant Escherichia coli BL21 (DE3) containing a
plasmid that expressed Green Fluorescent Protein (GFP) and -lactamase were exposed to CNTs
under various levels of agitation for different times. Fluorescence assay for GFP, optical
absorbance for -lactamase activity, and Transmission Electron Microscopy (TEM) were used to
determine the amount of released protein, and visually examine the permeability enhancement of
the cells, respectively. It was found that more -lactamase was present in the culture fluid after
treatment with CNTs in a dose dependent manner. Indeed, CNTs can lyse the cells up to 90% of
maximum when compared to lysozyme treatment. Based on TEM, it is believed that this
treatment damaged the cell walls to make E. coli permeable, causing periplasm proteins and
enzymes to leak out into the medium. Consequently, CNTs can be used as lysis agents when it is
undesirable to add an additional enzyme (lysozyme) to cause the release of intracellular proteins.
... The 2 µL PEG solution was dropped casting on the sensing electrode and baked at 60 • C for 6 h to form a two-layer structure of single-walled carbon nanotube/polymer composite sensing film. The proposed SU-8 based gas sensor exhibited excellent flexibility [18]. Figure 5 shows the sensor was packaged via the PCB gas response experiment. ...
... The 2 µL PEG solution was dropped casting on the sensing electrode and baked at 60 °C for 6 h to form a two-layer structure of single-walled carbon nanotube/polymer composite sensing film. The proposed SU-8 based gas sensor exhibited excellent flexibility [18]. Figure 5 shows the sensor was packaged via the PCB gas response experiment. ...
This study proposed a SU-8 based gas sensor, integrated with heater and sensing electrodes, to develop a multi-channel gas sensor with PEG/SWCNTs composite films. The impedance of single-walled carbon nanotubes (SWCNTs) on each sensing electrode was well controlled via dielectrophoresis technology. To investigate dielectrophoretic mobility characteristics, the concentric circular sensing electrode has three different spacing between the inner and outer electrodes, including 10 μm, 15 μm, and 20 μm. The electrodes were applied with a 5 MHz AC source with a voltage ranging from 1 Vpp to 5 Vpp. Polyethylene glycol (PEG) was deposited on the gas sensor via drop casting. The fabricated gas sensor was operated at different working temperatures, including 25 °C, 40 °C, 50 °C and 60 °C, to examine the sensing response. The response results revealed that the PEG/SWCNTs composites gas sensor with 60 °C working temperature exhibited the ability to detect 80 ppm ethanol vapor.
... Moreover, their large surface area and inner hollow space are an excellent scaffold for the attaching of drug molecules [11]. The stability of MWCNTs allows various chemical modifications to their tips and surfaces, improving their biocompatibility and binding to the bioactive agents as well [12,13]. In the last decade, different studies have been performed and developed to add multifunctional properties to MWCNTs, such as generating covalently bound functional groups for multi-walled carbon nanotubes using strong acids (H 2 SO 4 and HNO 3 ) for nanomedicine applications [13,14]. ...
... The stability of MWCNTs allows various chemical modifications to their tips and surfaces, improving their biocompatibility and binding to the bioactive agents as well [12,13]. In the last decade, different studies have been performed and developed to add multifunctional properties to MWCNTs, such as generating covalently bound functional groups for multi-walled carbon nanotubes using strong acids (H 2 SO 4 and HNO 3 ) for nanomedicine applications [13,14]. Applications of MWCNTs have increased rapidly due to their oxygencontaining moieties on the surface that can be modified by inorganic or organic molecules to affect the enhancement of the solubility of MWCNTs [15,16]. ...
In this work, the preparation of a PEG@ multi-walled carbon nanotubes (MWCNTs) composite has shown a great potential effect in tumor therapy using graphite powder at room temperature. PEGylated MWCNTs were created and used as a carrier for targeting the antineoplastic drug Ixazomib to myeloma cancer cells (abnormal plasma cells). Ixazomib (MLN2238) was covalently encapsulated into functionalized carbon nanotubes modified with polyethylene glycol (PEG 600) to obtain MWCNTs-PEG-MLN2238. The Ixazomib@ MWCNTs-PEG composite shows promising results as an effective nanocarrier and using a small amount of MWCNTs-PEG-Ixazomib that has a low toxicity compared with that of Ixazomib alone. A multifunctional MWCNTs-PEG-Ixazomib composite is used to test biological effects on multiple myeloma cell lines RPMI 8226 using the MTT assay to enhance treatment efficiency. The cytotoxicity of free Ixazomib citrate (69% cell viability of RPMI8226 cells) was higher than that of MWCNTs-PEG-Ixazomib (91% cell viability) at the same maximum concentration of Ixazomib citrate (50 µg/ml). In this work, we performed a study of preparation of MWCNTs with an acceptable Ixazomib loading efficiency and determination of the drug systemic toxicity for the first time. In this study, the preparation of MWCNTs with acceptable Ixazomib loading efficiency and determination of the drug systemic toxicity was performed for the first time. The MTT assay results show decreasing the toxicity of Ixazomib after loading with the MWCNTs-PEG composite. The MWCNTs-PEG @ Ixazomib show promising results as an effective carrier of Ixazomib and lead to a decrease in the cost of using Ixazomib.
Graphical Abstract
... PANI exhibits a peak at around 348 nm which is allocated to the π-π* transition of the benzenoid rings, while the shoulder at around 435 nm is characteristic of the protonated polyaniline of the localized polarons. The increasingly broad shoulder at ~ 800 nm with free carrier tail confirms the formation of emeraldine salt (ES) of PANI which is conducting in nature [28]. The optical spectrum of emeraldine base phase (EB) of PANI displays two peaks at around 325 nm for π-π* transition of benzenoid ring and at around 635 nm for quinoid excitation bands [21]. ...
... (1) = L∕RA The impact of incorporation of MWCNTs and dopant acids on the conductivities of PANI and its nanocomposites is illustrated statistically in Fig. 9. The MWCNTs act as a conducting bridge amongst the PANI chains and facilitate inter-chain charge transfer between the quinoid units [28], thus causing profound enhancements in conductivity. The MWCNTs are excellent electron acceptors, and PANI is a relatively good electron donor; this generates π-π* transitions between the MWCNTs surface and quinoid unit of PANI. ...
Polymer nanocomposites with vital reinforcements of conductive fillers have evinced as next-generation high-performance materials with multi-functional applications. Herein, we report the facile synthesis of thermally stable, highly electrically conducting polyaniline multi-walled carbon nanotubes (PANI/MWCNT) nanocomposites doped in two different protonic acids, i.e. hydrochloric acid (HCl) and sulphuric acid (H2SO4). The doping acids significantly affect the electric and dielectric properties of conducting polymer nanocomposites. The paper probes in the synergistic effects of MWCNTs and the effect of doping acid on the thermal stability, conductivity and dielectric properties of the nanocomposites based on PANI nanofibres. The structural, morphological, optical, thermal and electrical properties were evaluated through X-ray diffraction, scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, UV–Vis spectroscopy, thermogravimetric analysis and two-point probe technique. Ascribed to the high interfacial interaction between PANI and MWCNT, and considering the effect of doping acids, nanocomposites with high thermal stability, enhanced conductivity and high dielectric constant that can store large electrical charges have been synthesized by surfactant-assisted, in situ oxidative polymerization of aniline, in the presence of potassium persulfate as oxidant. The micellar structure of surfactant assists the dispersion of MWCNTs as well as the formation of PANI/MWCNT tubular structures. The effect of surfactant below and above critical micelle concentration was also studied. This complete study would affirm such a nanocomposite which procures excellent electrical and dielectric properties for microelectronic applications.
... CNTs are often associated with tissuespecific toxicity, and hence functionalization with appropriate group reduces toxicity to the significant level. 98 ...
... 103 CNTs, including both SWCNTs and multiwalled carbon nanotubes (MWCNTs), have shown promising results in delivering exogenous protein and nucleotides as negative regulators. Zhao et al, 2005 succeeded in synthesizing water-soluble SWCNTs with enormous potential in drug delivery system, including anticancer drug delivery. 104 SWCNTs with significant water solubility provide higher affinity to plasma protein and biocompatibility. ...
The breast cancer is one of the most common cancer affecting millions of lives worldwide. Though the prevalence of breast cancer is worldwide; however, the developing nations are having a comparatively higher percentage of breast cancer cases and associated complications. The molecular etiology behind breast cancer is complex and involves several regulatory molecules and their downstream signaling. Studies have demonstrated that the CD44 remains one of the major molecule associated not only in breast cancer but also several other kinds of tumors. The complex structure and functioning of CD44 posed a challenge to develop and deliver precise anti-cancerous drugs against targeted tissue. There are more than 20 isoforms of CD44 reported till date associated with several kinds of tumor in the using breast cancer. The success of any anti-cancerous therapy largely depends on the precise drug delivery system, and in modern days nanotechnology-based drug delivery vehicles are the first choice not only for cancer but several other chronic diseases as well. The Carbon nanotubes (CNTs) have shown tremendous scope in delivering the drug by targeting a particular receptor and molecules. Functionalized CNTs including both SWCNTs and MWCNTs are a pioneer in drug delivery with higher efficacy. The present work emphasized mainly on the potential of CNTs including both SWCNTs and MWCNTs in drug delivery for anti-cancerous therapy. The review provides a comprehensive overview of the development of various CNTs and their validation for effective drug delivery. The work focus on drug delivery approaches for breast cancer, precisely targeting CD44 molecule.
... Previous reports where esterification reactions were used for their preparation have been documented elsewhere. [10] However, other reactions, such as amidation, are useful for chemical preparations. Because PEG chains of 2 kDa molecular weight are sufficient to achieve protection against opsonization, [11] the 'grafting to' approach is an excellent method of synthesis because control of the molecular weight (MW) of PEG is possible. ...
The design of drug nanocarriers is a topic of current interest. To achieve a desirable efficiency, the preparation of a new nanocarrier must tune multiple complicated factors. Polyethylene glycol (PEG) has demonstrated the ability to evade biological barriers of living matter. In this work, the synthesis of nanocomposites prepared with PEG and carbon nanotubes (CNTs) functionalized with amine ending groups (named CNTsamine), which could be used as nanocarriers is described. A thorough characterization of prepared nanocomposites using Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) is presented. To explore the possibility of using the PEG/CNTsamine nanocomposites as suitable carriers its toxicity to HeLa cells was evaluated, their ability to release the anti-cancer drug cisplatin was determined, and their capacity to inhibit the growth of bacteria Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli as well as the fungus Candida albicans was studied. Although the PEG/CNTsamine nanocomposites have the ability to release the drug cisplatin with better efficacy than pure PEG, the evidence that produces a toxic effect on HeLa cells limit their practical use as suitable nanocarriers.
... To improve their performance, CNTs can be chemically modified. It is widely accepted that CNTs should have strong compatibility with various materials when coated with structurally similar polymers (45)(46)(47)(48)(49)(50)(51). To achieve a well-developed PFA/MWNTs composite coating, we choose to graft FA onto the surfaces of MWNTs, disperse the functional MWNTs in FA, and then polymerize the PFA/MWNTs composite. ...
... The CNT consists of a single layer of rolled-up G, such as in cylinder-like morphology. With the recent discovery of the versatile properties of CNTs, they have revolutionized biomedical research with their impressive structural, mechanical, and electrical properties [134][135][136][137][138][139]. Notably, their high drug-loading capacity due to their large surface-volume ratios, as well as their high mechanical properties and electrical and thermal conductivities, show their potential in PAI. ...
Photoacoustic imaging using energy conversion from light to ultrasound waves has been developed as a powerful tool to investigate in vivo phenomena due to their complex characteristics. In photoacoustic imaging, endogenous chromophores such as oxygenated hemoglobin, deoxygenated hemoglobin, melanin, and lipid provide useful biomedical information at the molecular level. However, these intrinsic absorbers show strong absorbance only in visible or infrared optical windows and have limited light transmission, making them difficult to apply for clinical translation. Therefore, the development of novel exogenous contrast agents capable of increasing imaging depth while ensuring strong light absorption is required. We report here the application of carbon nanomaterials that exhibit unique physical, mechanical, and electrochemical properties as imaging probes in photoacoustic imaging. Classified into specific structures, carbon nanomaterials are synthesized with different substances according to the imaging purposes to modulate the absorption spectra and highly enhance photoacoustic signals. In addition, functional drugs can be loaded into the carbon nanomaterials composite, and effective in vivo monitoring and photothermal therapy can be performed with cell-specific targeting. Diverse applied cases suggest the high potential of carbon nanomaterial-based photoacoustic imaging in in vivo monitoring for clinical research.
... Lin et al. [39] anchored PVA chains onto acid-treated SWCNTs and MWCNTs by esterifications activated with dicyclohexylcarbodiimide (DCC). In another study, poly(aminobenzene sulfonic acid) (PABS) and PEG were covalently attached to SWCNTs to form water-soluble graft copolymers with grafting extents of 30% and 71%, respectively [40]. Diez-Pascual et al. [41] synthesized a hydroxyl polyetheretherketone derivative (PEEK-OH) that was covalently grafted to the surface of acid-treated SWNCTs via a one-step process by activation of the carboxylic groups with DCC and via a two-stage process by acylation of the nanotubes with thionyl chloride (Scheme 4), leading to a grafting degree of about 12%. ...
Carbon nanotubes (CNTs), the one-dimensional allotropes of carbon, have attracted noteworthy research interest since their discovery in 1991 owing to their large aspect ratio, low mass density, and unique chemical, physical, and electronic properties that provide exciting possibilities for nanoscale applications. Nonetheless, two major issues should be considered when working with this sort of nanomaterial: their strong agglomerating tendency, since they are typically present as bundles or ropes of nanotubes, and the metallic impurities and carbonaceous fragments that go along with the CNTs. The successful utilization of CNTs in a wide variety of applications—in particular, in the field of polymer composites—depends on their uniform dispersion and the development of a strong chemical interaction with the polymeric matrix. To achieve these aims, chemical functionalization of their sidewalls and tips is required. In this article, a brief overview of the different approaches for CNT modification using polymers is provided, focusing on the covalent functionalization via “grafting to” or “grafting from” strategies. The characteristics and advantages of each approach are thoroughly discussed, including a few typical and recent examples. Moreover, applications of polymer-grafted CNTs as biosensors, membranes, energy storage substances, and EMI shielding are briefly described. Finally, future viewpoints in this vibrant research area are proposed.
... The delivery system itself was also found to be capable of doing something else to enhance drug penetration. For instance, when CNTs and drug crystals were subjected to the differential scanning calorimetry (DSC) analyses, melting endotherms of drug molecules were reported to disappear after surface adsorptions [5,6]. This interesting finding suggests that if CNTs adsorb drug molecules, they cannot go back to their original crystalline state because of strong interactions between carbon and the drug molecules. ...
The development or designing of new and futuristic drug delivery systems have been mainly focused on nanoparticles and the drug, but the alteration of water properties or configuration of water molecules in these formulations have not been properly addressed yet. Quite strange and unexpected results have been obtained with nanoparticles or nanotubes when they were subjected to the diffusion or penetration experiments. It may be possible to alter water properties in these nanoparticulate systems without notice. Water molecules can be surrounded by nanoparticles or they can travel inside of nanotubes. They are then squeezed among or inside of them. It forms an unexpected and entirely new type of molecule, a new state of water; “Quantum water”. The altered dissolving ability of this water can result in alteration of dissolution characteristics of the solution. These may affect permeability, absorption, or bioavailability. All these alterations should be considered before introducing any nanoparticulate/drug system to the market for human use. This article represents some literature findings with unexpected results and gives some new interpretations considering possible consequences, reasons. This new horizon can open a new window and new requirements can be determined when nanoparticles are going to be used for humans. All these can give better clues for the researcher to explain what is happening in the nano environment in drug formulations with nanoparticles.
... Briefly, CNTs are firstly modified to create carboxyl acid groups on the surface with a 3:1 mixture of concentrated H 2 SO 4 /HNO 3 [24]. This ensures the CNTs that can be stably dispersed in polar solvent because of the chemical combination between carboxyl acid group and amine group [25]. The functional CNTs were then added into TiO 2 precursor with NH 4 F used to adjust the pH value and reaction process, leading to the anchoring and growth of TiO 2 nanocrystalline, according to the previous reports [26][27][28]. ...
Supercapacitor-like Na-ion batteries have attracted much attention due to the possessing high energy density of batteries and power density of capacitors. Titanium dioxide (TiO2), is a promising anode material. Its performance is however seriously hindered by its low electrical conductivity and the sluggish diffusion of sodium ions (Na⁺) in the TiO2 matrix. Herein, this work combines porous TiO2 nanocubes with carbon nanotubes (CNTs) to enhance the electrical conductivity and accelerate Na⁺ diffusivity for Na-ion batteries (NIBs). In this composite, an interwoven scaffolded TiO2/CNTs framework is formed to provide abundant channels and shorter diffusion pathways for electrons and ions. The in-situ X-ray diffraction and cyclic voltammetry confirm the low strain and superior transport kinetics in Na⁺ intercalation/extraction processes. In addition, the chemically bonded TiO2/CNTs hybrid provides a more feasible channel for Na⁺ insertion/extraction with a much lower energy barrier. Consequently, the TiO2/CNTs composite exhibits excellent electrochemical performance with a capacity of 223.4 mAh g⁻¹ at 1 C and a capacity of 142.8 mAh g⁻¹ at 10 C (3.35 A g⁻¹). The work here reveals that the combination of active materials with CNTs can largely improve the utilization efficiency and enhance their sodium storage.
... Induction of carboxyl and chlorine on MWCNTs could increase the carrying capacity and reduce the complications symptoms on healthy cells. 16 Moreover, timely detection and the right administration of the appropriate antibiotics could enhance the ability to recover. In contrast, aging, being infected with HIV, and having ...
Background
Tuberculosis (TB) has always been recognized as one of the fatal infectious diseases, which is caused by Mycobacterium tuberculosis (M.tb). Isonicotinic acid hydrazide or isoniazid (INH) is one of the most commonly utilized drugs in the treatment of TB. Patients need to take 300 mg daily of INH for 6 months in combination with another anti-TB drug and tolerate several side effects of INH. On the other hand, the emergence of resistant strains of anti-TB antibiotics is one of the major problems in the treatment of this disease. So, antimicrobial drug delivery by nanofluids could improve the efficacy, and reduce the adverse effects of antimicrobial drugs. The purpose of this study was to perform a novel method to synthesize INH-conjugated multi-wall carbon nanotubes (MWCNTs) for more effective drug delivery, as well as, TB treatment.
Methods
INH-conjugated functionalized MWCNTs were prepared, using a reflux system. The characterization of the obtained nano-drug was performed by the elemental analyses of total nitrogen, hydrogen, carbon and sulfur (CHNS), Raman spectroscopy, Fourier transform infrared (FTIR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) methods. The nanofluid of nano-drug was prepared by the ultrasonic method, and the related antibacterial effect studies were carried out on the two strains of M.tb.
Results
The antimicrobial effect of INH-conjugated MWCNTs was found to be much better at low concentrations than the pure drug in all of the strains.
Conclusion
Since one of the main antimicrobial mechanisms of MWCNTs is through the destruction of the bacterial cell wall, in addition to its antimicrobial effects, it increased the drug delivery of INH at lower doses compared to drug alone. So, the nanofluid, containing INH-conjugated MWCNTs, had a better lethal effect on a variety of M.tb strains than that of the drug alone.
... Single-walled carbon nanotubes (SWCNTs) have been considered candidates for applications in biotechnology and biomedicine [1,2], and in particular for neural applications [3,4]. When chemically functionalized with polyethylene glycol (PEG), SWCNTs render water solubility [5]. These colloidal solutes, SWCNT-PEG, have been used to modulate the morpho-functional properties of two main neural cell types, neurons [6] and astrocytes [7], in culture. ...
We used single-walled carbon nanotubes chemically functionalized with polyethylene glycol (SWCNT-PEG) to assess the effects of this nanomaterial on astrocytic endocytosis and exocytosis. We observed that the SWCNT-PEG do not affect the adenosine triphosphate (ATP)-evoked Ca2+ elevations in astrocytes but significantly reduce the Ca2+-dependent glutamate release. There was a significant decrease in the endocytic load of the recycling dye during constitutive and ATP-evoked recycling. Furthermore, SWCNT-PEG hampered ATP-evoked exocytotic release of the loaded recycling dye. Thus, by functionally obstructing evoked vesicular recycling, SWCNT-PEG reduced glutamate release from astrocytes via regulated exocytosis. These effects implicate SWCNT-PEG as a modulator of Ca2+-dependent exocytosis in astrocytes downstream of Ca2+, likely at the level of vesicle fusion with/pinching off the plasma membrane.
... Also, high dispersion of the CNT distribution can be achieved by CNT surface modification due to the covalent bonding of functional groups [41][42][43][44][45]. In situ polymerization in the presence of covalently functionalized CNTs not only provides the formation of a homogeneous nanostructure, but also prevents phase micro-separation. ...
Hybrid nanocomposites based on electroactive polydiphenylamine-2-carboxylic acid (PDPAC) and single-walled carbon nanotubes (SWCNTs) were obtained for the first time. Polymer-carbon nanomaterials were synthesized via in situ oxidative polymerization of diphenylamine-2-carboxylic acid (DPAC) in the presence of SWCNTs by two different ways. Hybrid SWCNT/PDPAC nanocomposites were prepared both in an acidic medium and in the heterophase system in an alkaline medium. In the heterophase system, the monomer and the SWCNTs are in the organic phase (chloroform) and the oxidant (ammonium persulfate) is in an aqueous solution of ammonium hydroxide. The chemical structure, as well as the electrical and thermal properties of the developed SWCNT/PDPAC nanocomposite materials were investigated.
... The efficient way to progress the dispersion of SWCNTs is by functionalization of CNTs, which helps prevent the aggregation [106]. As a substitute, covalent functionalization is more reactive and has an enriched affinity with chemical species such as functional architectures and polymers [107]. ...
... The previous research has shown that a derivative of SWNTs polymerized by PEG both increases the solubility of the SWNTs and decreases the activation of macrophages in response to the SWNTs in vivo [96][97][98][99]. In the study by Belyanskaya et al. [61], the introduction of PEG to the SWNTs had no effect on the peroxidase-induced degradation of the nanotubes. ...
... Riggs et al. [144] prepared poly (vinyl acetate-co-vinyl alcohol) (PVAc-VA) grafted SWCNTs composites through ester linkages where sidewall of the SWCNT is acyl chloride activated. CNTs can be siliconfunctionalized and it can be done by ring opening reaction of functionalized polydimethyl siloxanes (PDMS) in the presence of acid modified MWCNTs [145]. The obtained silicon functionalized CNTs are very viscous in nature and almost tar-like at room temperature. ...
... The advantage of this approach is that preformed polymer units of known molecular weight and polydispersity can be used, thus guaranteeing strict conformational symmetry regulation (Spitalsky et al., 2010). Several grafting to reactions are employed to modify the CNTs, such as direct ester linkage between oxidized CNTs and polymer (Fernando et al., 2005;Zhao et al., 2005); amide linkage between CNTs and polymer (Lin et al., 2002;Hu et al., 2005); nucleophilic additions or coupling reactions (Blake et al., 2006;Xie et al., 2007); cycloaddition (Li et al., 2005(Li et al., , 2006; and cyclosubstitution (Li and Adronov, 2007). In addition to such chemical reactions, polymers can also be grafted through an ultrasonication mediated approach, where defects on the CNT sidewalls are created that act as reactive sites for organic materials to covalently couple (Koshio et al., 2001). ...
Since their discovery, carbon nanotubes (CNTs) have been regarded as a fascinating feat of human contrivance. These lightweight materials feature a large aspect ratio and are bestowed with incredible mechanical properties, as well as high flexibility and high electrical conductivity, which have endeared them to be actively researched over the last decade in pertinence to high-end electrical and communication related applications. However, the use of CNTs in their bulk form results in a poor translation of their inherent properties, limiting technological advancement to macroscopic formats. To exploit their endogenous attributes, it becomes crucial to composite CNTs with engineering polymers (e.g., thermoplastics, elastomers, conjugated polymers) or natural polymers to obtain nanocomposites with augmented benefits. In this chapter, we present the different strategies adopted for surface modifications of CNTs, which are necessary for their efficient interactions with any polymer of interest. Also, insights into different strategies opted for the fabrication of nanocomposite matrices to achieve intercalative and exfoliative structures are also presented. The physical properties of thus fabricated polymer/CNT nanocomposites are also discussed with emphasis on their mechanical, thermal, electrical, rheological, and optical attributes. The chapter also focuses on a few recent advanced applications of these nanocomposites in the domains of microelectronics, including efficient energy storage devices and health care applications with special impetus on targeted drug delivery systems and tissue engineering applications.
... Amino functional groups of the PEI molecule can undergo a nucleophilic addition reaction. The PEG chain contains an oxygen atom to form a hydrogen bond [18]. These properties make the gas-sensitive properties of the four polymers different, and the selective identification of VOCs can be achieved by constructing a gas sensor array. ...
... Amino functional groups of the PEI molecule can undergo a nucleophilic addition reaction. The PEG chain contains an oxygen atom to form a hydrogen bond [20]. These properties make the gas-sensitive properties of the four polymers different. ...
Sensitive detection of volatile organic compounds (VOCs) is significant for environmental monitoring and medical applications. In this work, multi-walled carbon nanotubes (MWCNTs) and polyethylene glycol (PEG) that have good adsorption for VOCs, were sprayed layer by layer on an interdigitated electrode (IDE) to build a sensitive VOCs gas sensor. The relative resistance change (△R/R) when the sensor was exposed to VOCs was measured. The sensor showed high sensitivity to acetone, ethanol, isopropanol and isoprene with fast response (110 ± 5 s) and recovery (152 ± 5 s) at room temperature, and the lower detection limit (LDL) of the sensor reached 9 ppm. With the micro-fabricated IDE structure, the sensor can be easily built into an electric nose for VOC recognition and measurement.
Long cycle life and high energy/power density are imperative to energy storage systems. Polyaniline (PANI) has shown great potential as an electrode material but is limited by poor cycling and rate performance. We present a molecular design approach of binding short-chain aniline trimers (ATs) and carbon nanotubes (CNTs) through the formation of amide covalent linkages enabled by a simple laser scribing technique. The covalently coupled AT/CNT (cc-AT/CNT) composite retains 80% of its original capacitance after 20 000 charge/discharge cycles, which readily outperforms long-chain PANI/CNT composites without covalent connections. The compact AT/CNT heterointerfaces produce fast charge/discharge kinetics and excellent rate capability. The flexible symmetric quasi-solid-state devices can be stably cycled beyond 50 000 cycles, at least 5 times longer than most PANI/CNT-based symmetric supercapacitors reported to date. This molecular design of durable conducting polymer-based electrode materials enabled by laser irradiation presents a feasible approach toward robust advanced energy storage devices.
Tissue engineering is an arrangement of bioactive molecules, cells, and scaffolds for the reconstruction of injured tissues. Functionalized carbon nanotubes (CNTs) have emerged in the present time as pioneering components for the fabrication of the next‐generation scaffolds to reconstruct injured tissue. Polymer‐functionalized CNTs could exhibit various properties, including higher compatibility and ability of complexation with polymer matrix, improved dispersibility in different solvents, and responsivity to environmental stimuli. Furthermore, CNTs have broadly been investigated for their potential in tissue engineering because of their exceptional mechanical, physicochemical, and thermal features as well as suitable biocompatibility. CNTs based scaffolds have acquired significant recognition because of their brilliant attributes, which offer a synthetic but feasible microenvironment for chondrogenic differentiation, and cell proliferation. In this chapter, we aim to give an overview of the structural, physicochemical characteristics along with interactions and biodegradation of CNTs‐based polymeric scaffolds with the biomolecules and outline their impacts on the extracellular matrix in the regeneration of neural, cardiac, bone, and cartilage tissue engineering. This chapter also provides a current state of information accessible investigating the utilization of the polymeric composites comprising CNTs and the development of the 3D scaffolds as well as the directions of future research and challenges.
For ages, carbon has been used in technology and in human existence, both as a single entity and in many forms. Since prehistoric times, carbon-based substances such as graphite, charcoal, and carbon black have been employed as writing and drawing materials. Conjugated carbon nanomaterials, including carbon nanotubes, fullerenes, activated carbon, and graphite, have been used as energy sources over the past two and a half decades due to their unique properties. Because of their amazing chemical, mechanical, electrical, and thermal capabilities, carbon nanostructures have lately found usage in a range of sectors, including drug administration, electronics, composite materials, sensors, field emission devices, and energy storage and conversion. Carbon nanoparticles (when employed as energy materials) are thought to be an adequate and promising way to mitigate the hazard. Subsequently, these materials’ astounding properties, as well as the best possibilities for greener and harmless to the ecosystem combination strategies and modern-scale creation of carbon nanostructured materials are irrefutably significant and can consequently be viewed as a point of convergence of numerous researchers and specialists in the twenty-first century. This book chapter tries to summarize recent advances in their synthesis, properties, and applications as described in the literature
The research of carbon nanotubes (CNTs) has contributed to basic science and is playing leading roles in potential applications, including nanomedicine. In particular, CNTs have been proposed as nanocarriers for cancer therapeutics. This study reviews the advantages and potential challenges of using CNTs in chemotherapy drug-delivery formulations. We mainly focus on tumor-targeted systems prepared with hyaluronic acid and folic acid because of their biocompatibility, low cost, ease of conjugation to targeting agents, and specificity for pathologic cells. The relevance of these CNTs-based tumor-targeted drug-delivery systems is discussed for cisplatin, carboplatin, doxorubicin, gemcitabine, salinomycin, chlorin e6, and paclitaxel. An extensive and diversified list of methodologies for preparing these drug-delivery systems provides a rationale for definite protocols to attain comparability between conjugates prepared from different formulations. Hence, the scope of various CNTs-based tumor-targeted drug-delivery systems was reviewed from a perspective relating to the opportunities of using CNTs in chemotherapeutics and the challenges associated with developing formulations for human use. (c) 2022 American Chemical Society.
Reaction of PhNCS with the polyetheramine Jeffamine® M600 H2NCHMeCH2(OCHMeCH2)nOCH2CH2OMe gave the polyether-functionalised thiourea PhNHC(S)NHCHMeCH2(OCHMeCH2)nOCH2CH2OMe. Neutral bis(phosphine) platinum(II) and palladium(II) complexes [M{SC(NPh)N(CHMeCH2(OCHMeCH2)nOCH2CH2OMe)}(PPh3)2], containing the thiourea dianion ligand, were prepared by reaction of [MCl2(PPh3)2] (M = Pt, Pd) with the thiourea and Me3N base in refluxing methanol. Closely related cationic complexes containing thiourea monoanion ligands were isolated by addition of NaBPh4 to the reaction mixtures. Corresponding organo-ruthenium, -iridium and -rhodium complexes were prepared by the reaction of [(η⁶-p-cymene)RuCl2]2 or (Cp*MCl2)2 (M = Ir, Rh; Cp* = η\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\eta$$\end{document}⁵-C5Me5) with the thiourea. Positive-ion ESI mass spectrometry was shown to be a convenient and powerful technique for the investigation of these complexes. A model Rh complex was also prepared from the short-chain analogue PhNHC(S)NHCH2CH2OMe.
Deterioration of water quality is a desperate threat worldwide. Industrial development regularly added a vast amount of organic and inorganic contaminants to water. Therefore, eradicating these contaminants is highly essential for the well-being of biotic components. Adsorption-assisted technologies are among the most benign and principally used due to their higher efficiencies at lower costs and independence of complex technological supports. Carbon nanomaterials, such as activated carbons, carbon nanotubes, graphene-based materials, and carbon dots have been broadly adopted as adsorbents because of their outstanding surface characteristics. Researchers worked a lot on activation procedures and chemicals to achieve an ultrahigh surface area (above 3000 m²/g) to increase the adsorption efficiency. Further, cross-linked carbon nanotubes exhibited much-selected adsorption to organics. Carbon dots, a new type of carbon-based nanomaterials emerged as excellent adsorbents when introduced into the polymers matrix and provided promising platforms for the removal of metal ions. Also, graphene oxide and other oxidized forms of carbon being rich in functional groups are reported to exhibit excellent adsorption capacities as high as 2564 mg/g at 25 °C for basic and cationic compounds.
Here, we reviewed the various types of pollutants found in aquatic biota with some basics on fundamentals and mechanistic features of adsorption, adsorption efficiency regulating factors. The article emphasized the performances of carbon nanomaterials and associated nanocomposites for the adsorption of various pollutants. The review also addresses the essential issues for the technical development and commercial application of carbon-assisted materials as nano adsorbents for water decontamination.
This chapter deals with nanoreinforced thermoset resins. Use of various types of nanofillers namely layered silicate, carbon nanotube, graphene, polyhedral oligomeric silsesquioxanes, silver nanoparticle, block copolymers for preparing thermoset nanocomposite are presented. The concept of simultaneous toughening and reinforcement is also covered. The mechanism of toughening of thermoset matrix using nanomaterials is elaborated. A brief review of recent advances in the field of polymer nanocomposite is presented. The research activities on addressing the issues of dispersion of nanoparticles and interfacial bonding are reviewed critically.
Grafting polymerization based on polypropylene glycol (PPG) and styrene (St) was synthesized with different composition of styrene using the free radical technique in the presence of potassium persulphate as an initiator. The grafted copolymers (PPG-g-St) used different styrene composition (65/15, 65/25, 65/35), respectively. The grafted copolymers were investigated through FTIR (Fourier-transform spectroscopy), Differential scanning calorimeter and thermogravimetric analyzer. FTIR showed new peaks at 1450 cm-1 and 1135 cm-1 due to the grafting process of St on PPG. Thermal stability of grafted copolymer increases by increasing the ratio of styrene, while Tg decreases by increasing the ratio of styrene.
Radiation-induced enteropathy is a major clinical challenge during radiotherapy. Resveratrol displays beneficial pharmacological activities; however, low oral bioavailability limits its effectiveness. This study aims at preparing methacrylic acid (MAAc) functionalized multi-walled carbon nanotubes (MWCNTs-MAAc) as carriers for pH triggered controlled release of resveratrol in an effort to improve the drug therapeutic potential. MWCNTs-MAAc were prepared using radiation technique and then characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier transform-infrared (FT-IR) spectroscopy. In vitro drug release profile at different pH values was analyzed. Furthermore, the designed RES-MWCNTs-MAAc nanocomplex was evaluated against radiation-induced enteropathy in rats. Oral administration of RES-MWCNTs-MAAc restored colonic redox state and elevated antioxidant enzymes activities glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) and reduced colonic inflammatory mediators tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interferone-γ (IFN-γ) contents in addition to declining the intrinsic apoptotic pathway as evidenced by down-regulation of Bax and caspase-3 proteins expression accompanied by up-regulation of Bcl-2 protein expression. RES-MWCNTs-MAAc was more efficient than free resveratrol due to the delivery system that allowed prolonged resveratrol release at target site. Thus, this formulation could serve as a beneficial anti-inflammatory approach for patients during radiotherapy.
A simple, quick, effective turn-on fluorescence assay for the determination of fipronil (FIP) was built based on the yellow fluorescence of FAM-aptamer and excellent quenching capability of the oxidized single-walled carbon nanohorns (The oxidized SWCNHs). Oxidized SWCNHs with the great advantage of good dispersibility in solution were generated by link to carboxyl group and were added to a specific FAM-aptamer at an optimal concentration to form an "on-off" oxidized SWCNH/FAM-aptamer fluorescent sensor. The structures of the oxidized SWCNHs were verified, and the comprehensive properties were evaluated by characterization techniques. This paper has exploited oxidized SWCNHs as a quenching agent to detect fipronil for the first time. Under the optimized conditions, the limit of detection (LOD) for fipronil was 3 nM, and the recovery of fipronil varied from 88.6% to 112.7% in different real samples with relative standard deviations (RSDs) not more than 5%. The developed method could be successfully applied for the determination of fipronil in tap water, honey and corn samples.
Dielectric elastomer actuators (DEAs) are soft, electrically powered actuators that have no discrete moving parts, yet can exhibit large strains (10%–50%) and moderate stress (∼100 kPa). This Tutorial describes the physical basis underlying the operation of DEA's, starting with a simple linear analysis, followed by nonlinear Newtonian and energy approaches necessary to describe large strain characteristics of actuators. These lead to theoretical limits on actuation strains and useful non-dimensional parameters, such as the normalized electric breakdown field. The analyses guide the selection of elastomer materials and compliant electrodes for DEAs. As DEAs operate at high electric fields, this Tutorial describes some of the factors affecting the Weibull distribution of dielectric breakdown, geometrical effects, distinguishing between permanent and “soft” breakdown, as well as “self-clearing” and its relation to proof testing to increase device reliability. New evidence for molecular alignment under an electric field is also presented. In the discussion of compliant electrodes, the rationale for carbon nanotube (CNT) electrodes is presented based on their compliance and ability to maintain their percolative conductivity even when stretched. A procedure for making complaint CNT electrodes is included for those who wish to fabricate their own. Percolative electrodes inevitably give rise to only partial surface coverage and the consequences on actuator performance are introduced. Developments in actuator geometry, including recent 3D printing, are described. The physical basis of versatile and reconfigurable shape-changing actuators, together with their analysis, is presented and illustrated with examples. Finally, prospects for achieving even higher performance DEAs will be discussed.
At present treatment methods for cancer are limited, partially due to the solubility, poor cellular distribution of drug molecules and, the incapability of drugs to annoy the cellular barriers. Carbon nanotubes (CNTs) generally have excellent physio-chemical properties, which include high-level penetration into the cell membrane, high surface area and high capacity of drug loading by in circulating modification with bio-molecules, project them as an appropriate candidate to diagnose and deliver drugs to prostate cancer (PCa). Additionally, the chemically modified CNTs which have excellent 'Biosensing' properties therefore makes it easy for detecting PCa without fluorescent agent and thus targets the particular site of PCa and also, Drug delivery can accomplish a high efficacy, enhanced permeability with less toxic effects. While CNTs have been mainly engaged in cancer treatment, a few studies are focussed on the diagnosis and treatment of PCa. Here, we detailly reviewed the current progress of the CNTs based diagnosis and targeted drug delivery system for managing and curing PCa.
Clean and accessible water for all has been defined by the United Nations as a major goal to promote sustainability in a planet with improved life quality. However, the growth of population and global industry processes are having a massive impact on the water quality. The presence of organic pollutants in water and wastewater, such as pharmaceuticals, organic dyes and by-products of industrial processes, is a major issue. Conventional wastewater treatments are still limited, and, consequently, it is crucial to design innovative cleaning technologies such as heterogeneous photocatalysis with nanomaterials. Here we review mechanisms and applications of carbon-based nanostructures for heterogeneous photocatalysis applied to water purification. In particular, we present recent developments in synthetic routes and surface modification of carbon nanostructures aiming at their use under visible light irradiation. As such, carbon-based nanostructures decorated with distinct phases have been investigated, such as semiconductor compounds and polyoxometalates. The photocatalytic efficiency of hybrid nanocomposite materials is attributed to improved light harvesting and reduced recombination of photo-generated charge carriers. Furthermore, the recovery of photocatalysts by using assisted magnetic separation is presented as a promising strategy of reusability.
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.
Imidazolium-based ionic liquids (ILs) have been perceived as a promising candidate for bridging polyaniline (PANI) on well-dispersed carbon nanotubes (CNTs) via formation of IL-stabilized multiwalled carbon nanotubes (MWCNTs) dispersion in which outer walls of CNTs, as well as benzene rings of the aniline monomer and the growing polymer, have been potently effective in such procurement. The sulfonated water-soluble PANI-[C16C1im]Cl-MWCNT nanocomposites (SPANI-IL-MWCNTs) are directly deposited on a graphite-based current collector using a simple and cost-effective electrophoretic deposition (EPD) method. The SPANI-IL-MWCNT electrodes exhibit remarkable electrochemical performance compared to SPANI-MWCNTs in the absence of imidazolium-based ILs. The symmetric supercapacitor (SSC) devices are fabricated using SPANI-IL-MWCNT as the electrode and the electrochemical properties of the SSC devices are investigated. The electrochemical results demonstrate that the SPANI-IL-MWCNT SSC devices exhibit an outstanding energy density (59.3 Wh·kg–1) at a reasonable power density of 187.5 W·kg–1. It also represents remarkable cycling durability (retaining almost over 83.5% of its initial capacitance after 6000 charge–discharge cycles). Findings in this work provide convincing evidence that hierarchical SPANI-IL-MWCNTs could be a potential candidate as an ideal electrode material for high-performance energy storage systems.
Carbon-based nanomaterials such as carbon nanotubes (CNTs) have become the most promising materials in biomedical, electronic and aerospace applications. When added to polymers, they can enhance the properties and the utility of the polymers to a large extent. This is because of their superior thermo-mechanical and electrical properties which can be effectively transferred to the resulting composites with their proper dispersion in the polymer matrix. But the uniform dispersion of CNTs in various polymer matrices is the major challenge faced by scientists. This paper critically reviews the different chemical strategies adopted for grafting polymers onto the CNTs which ultimately leads to better polymer-filler interaction and optimum filler dispersion for the development of high-performance polymer nanocomposites. This review also discusses the synthesis, properties, and applications of polymer grafted CNTs and their composites.
Regenerative medicine has taken advantage of several nanomaterials for reparation of diseased or damaged tissues in the nervous system involved in memory, cognition, and movement. Electrical, thermal, mechanical, and biocompatibility aspects of carbon-based nanomaterials (nanotubes, graphene, fullerenes, and their derivatives) make them suitable candidates to drive nerve tissue repair and stimulation. This review article focuses on key recent advances on the use of carbon nanotube- (CNT-) based technologies on nerve tissue engineering, outlining how neurons interact with CNT interfaces for promoting neuronal differentiation, growth and network reconstruction. CNTs still represent strong candidates for use in therapies of neurodegenerative pathologies and spinal cord injuries.
We introduce a simple and eco-friendly synthesis of multiwalled carbon nanotubes with silver nanoparticles as a MWCNT-Ag hybrid. A solution is made of MWCNTs and AgNO3 in polyethylene glycol, where the silver nitrate gets reduced into AgNPs in the presence of MWCNTs. We have studied the effect of concentration and temperature on the hybrid nanostructure formation. Formation of MWCNT-Ag composite was confirmed through UV–Vis, transmission electron microscope images, and the Raman studies. The nonlinear optical properties of the hybrids were examined using Z-scan technique using the second harmonic at 532 nm of Nd:YAG laser operated at 10 Hz and pulse duration of 6 ns. The experimental results also revealed that surface enhanced Raman scattering enhancement depends on the temperature during synthesis of hybrid nanoparticles, size, and concentration of AgNPs. The nonlinear absorption exhibits reverse saturable absorption behaviour due to the excited state absorption process.
Nanocomposite membranes of sulfonated polyether ether ketone (sPEEK) are prepared with polyaminobenzene sulfonic acid grafted single-walled carbon nanotubes copolymer (PABS-SWCNT) and its zwitterion interactions are studied. The nanocomposite membranes are prepared through solution cast technique using PABS-SWCNT as additive in different weight % (0.1, 0.15, and 0.2) ratio. The additive and nanocomposite membranes are characterized for its surface morphology, composition, thermal and physico-chemical properties. The nanocomposite membrane comprising optimized content of PABS-SWCNT (0.15 wt %) shows improved proton conductivity and reduced methanol crossover resulting in enhanced DMFC peak power density of 150 mW cm⁻² in comparison to 110 mW cm⁻² for sPEEK and 80 mW cm⁻² for Nafion® 117 respectively. The improved durability till 100 h for sPEEK/PABS-SWCNT (0.15 wt %) compared to sPEEK and Nafion-117 confirms its viability in DMFC application.
Polypropylene (PP)/multi-walled carbon nanotubes (MWNTs) nanocomposites with excellent toughness and ductility pose significant challenges because of the severe aggregation of MWNTs in non-polar PP matrix due to the incompatibility. In this work, lithium bis(trifloromethanesulfonyl) imide (Li-TFSI) and maleic anhydride grafted polypropylene (MAPP) have been simultaneously introduced to modify MWNTs for the homogenous dispersion in PP matrix. The surface of MWNTs has strong “π-cation” interactions with the Li⁺ ions of Li-TFSI. At the same time, Li-TFSI can promote the ring-opening of the maleic anhydride and form coordination with the newly formed carboxylate. Therefore, the combination of Li-TFSI/MAPP enhanced the compatibility between PP and MWNTs. The Li-TFSI/MAPP modified MWNTs can be dispersed uniformly in the polypropylene. The elongation at break and the toughness of the nanocomposites with the 3 wt % modified MWNTs are 800% and 26 kJ/m², respectively. The values are significantly higher than those of the samples (200% and 22 kJ/m²) at the same MWNTs loading. The strategy paves new possibility to fabricate high performance PP nanocomposites.
Nanomedicine has allowed for emerging advances in imaging, diagnostics and therapeutics. Regenerative Medicine has taken advantage of a number of nanomaterials for reparation of diseased or damaged tissues in the nervous system involved in memory, cognition and movement. Electrical, thermal, mechanical and biocompatibility aspects of carbon-based nanomaterials (nanotubes, graphene, fullerenes and their derivatives) make them suitable candidates to drive nerve tissue repair and stimulation. This review article focuses on recent advances on the use of carbon nanotube (CNT)-based technologies on nerve tissue engineering; outlining how neurons interact with the nanomaterials interface for promoting neuronal differentiation, growth and network reconstruction for their possible use in therapies of neurodegenerative pathologies and spinal cord injuries.
Conducting polymers (CPs) characteristically form polarons, bipolarons, or solitons and exhibit low band-gap energies. These properties make them to be suitable materials for applications in sensors, semiconductors, anticorrosion coatings, batteries, and display devices, among others. This chapter focuses on the electronics, electrochemistry, and processability of some commonly used CPs in the recent past – namely, polyaniline (PANI), polypyrrole (PPy), polythiophene (PTh), poly(3,4-ethylenedioxythiophene) (PEDOT), and polyfuran (PFu). Also included in the chapter are conducting dendritic star copolymers and polymeric nanocomposites incorporating single-walled and multiwalled carbon nanotubes.
Nanotechnology is the science and engineering concerned with the design, synthesis, characterization, and application of materials and devices that have a functional organization in at least one dimension on the nanometer (nm) scale, ranging from a few to about 100 nm. Nanotechnology is beginning to help advance the equally pioneering field of stem-cell research, with devices that can precisely control stem cells (SCs) and provide nanoscaled-biodegradable scaffolds and magnetic tracking systems. SCs are undifferentiated cells generally characterized by their functional capacity to both self-renew and to generate a large number of differentiated progeny cells. The characteristics of SCs indicate that these cells, in addition to use in developmental biology studies, have the potential to provide an unlimited supply of different cell types for tissue replacement, drug screening, and functional genomics applications. Tissue engineering at the nanoscale level is a potentially useful approach to develop viable substitutes, which can restore, maintain, or improve the function of human tissue. Regenerating tissue can be achieved by using nanobiomaterials to convey signals to surrounding tissues to recruit cells that promote inherent regeneration or by using cells and a nanobiomaterial scaffold to act as a framework for developing tissue. In this regard, nanomaterials such as nanofibers are of particular interest. Three different approaches toward the formation of nanofibrous materials have emerged: self-assembly, electrospinning, and phase separation [1]. Each of these approaches is unique with respect to its characteristics, and each could lead to the development of a scaffolding system. For example, self-assembly can generate small-diameter nanofibers in the lowest end of the range of natural extracellular matrix (ECM) collagen, while electrospinning is more useful for generating large-diameter nanofibers on the upper end of the range of natural ECM collagen. Phase separation, on the other hand, has generated nanofibers in the same range as natural ECM collagen and allows for the design of macropore structures. Specifically designed amphiphilic peptides that contain a carbon alkyl tail and several other functional peptide regions have been synthesized and shown to form nanofibers through a self-assembly process by mixing cell suspensions in media with dilute aqueous solutions of the peptide amphiphil (PA) [2,3]. The challenges with the techniques mentioned above are that electrospinning is typically limited to forming sheets of fibers and thus limiting the ability to create a designed three-dimensional (3D) pore scaffold, and selfassembling materials usually form hydrogels, limiting the geometric complexity and mechanical properties of the 3D structure. Another class of nanomaterials includes carbon nanotubes (CNTs), which are a macromolecular form of carbon with high potential for biological applications due in part to their unique mechanical, physical, and chemical properties [4,5]. CNTs are strong, flexible, conduct electrical current [6], and can be functionalized with different molecules [7], properties that may be useful in basic and applied biological research (for review see [8]). Single-walled carbon nanotubes (SWNTs) have an average diameter of 1.5 nm, and their length varies from several hundred nanometers to several micrometers. Multiwalled carbon nanotube (MWNT) diameters typically range between 10 and 30 nm. The diameters of SWNTs are close to the size of the triple helix collagen fibers, which makes them ideal candidates for substrates for bone growth. As prepared CNTs are insoluble in most solvents, chemical modifications are aimed at increasing their solubility in water and organic solvents.
A new soluble conducting polymer has been found that promises to be useful both in understanding conducting polymer chemistry and in new industrial applications. The compound ortho-methoxyaniline can be polymerized by both chemical and electrochemical methods and gives, using either method, a highly colored material with a conductivity of 3.0 S and good solubility in a number of inorganic and organic solvents. The soluble polymer was analyzed using a variety of common experimental techniques including u.v.-visible and infrared spectroscopy, proton magnetic resonance spectroscopy and gel permeation chromatography. Cyclic voltammetry of a polymethoxyaniline film showed a reversible spectrum of two oxidation peaks and two reduction peaks. Molecular weight studies show that poly-o-methoxyaniline exists as a very monodisperse polymer with Mw of 2200.
Polyaniline/single wall carbon nanotube composites were prepared to be used as printable conductors for organic electronics devices. We show here that the high aspect ratio of single wall carbon nanotubes enables percolation into a conducting network at extremely low nanotube concentration. The nature of the transport mechanism is revealed by the temperature dependence of the conductivity of these percolating composites. We demonstrate here that these thin composite films are printable via laser ablation with high resolution while retaining appropriate conductivity. The utility of these findings is illustrated by printing structures, which could serve as a source and drain with 7 μm channel and 2 S/cm conductivity for use in plastic transistors.
Stable multi-walled carbon nanotubes (MWNTs) ethanol suspension in the 1 wt.% concentration is obtained used only 20 dmb% copolymer as dispersant. The stability and adsorption behaviors of MWNTs ethanol suspension with copolymer have been studied. The Zeta potential of MWNTs in ethanol suspension is determined over a range of pH. The adsorption isotherms are of Langmuirian type. The interactions between copolymer and MWNTs are discussed based on the adsorption density results. Scanning electron micrograph is found to exhibit large difference between the morphology of nanotubes resulting from the suspensions without and with copolymer. The high ΔG°sp value and intense adsorbability in this study are considered as evidences for the chemical interaction between copolymer and MWNTs. Mechanism of the MWNTs suspension stability with copolymer is discussed. The detailed description of the surface chemistry can be used as a guide for designing efficient dispersant.
A water-soluble externally (HCl)-doped conducting polyaniline (ED-SPAN) is prepared by such a simple synthetic method that emeraldine salts are sulfonated by chlorosulfonic acid in dichloroethane at 80°C and subsequently hydrated in water at 100°C. Sulfonating any emeraldine salts (counter anion X− = Cl−, SO42−, and BF4−) or emeraldine base results in the production of HCl-doped sulfonated polyaniline, where HCl dopant from hydrolysis of chlorosulfonic group exchanges with the original dopant. The degree of sulfonation, namely, sulfur-to-nitrogen (S/N) ratio, can be controlled by adjusting the amount of chlorosulfonic acid. With increasing S/N ratio from 0.65 to 1.3, the solubility in neutral water increases from 22 to 88 g/l and the four-probe conductivity for a compressed pellet decreases from 0.023 to 1.7 × 10−5 S/cm, showing sulfonation-induced undoping.
The synthesis of poly(m-aminobenzene sulfonic acid) homopolymer (PABS), by aniline initiated polymerization of m-aminobenzene sulfonic acid using ammonium persulfate oxidation has been attempted. The water soluble polymer PABS thus synthesized was characterized by IR, UV, TG-DSC, 1H-NMR, SEM and ESR spectroscopic techniques. A co-ordinated IR and thermal analysis (TG, DSC) indicate that thermal desulfonation occurs preferentially in PABS–Na compared to PABS, commencing at 310°C and 370°C, respectively. The steric hindrance due to the large ortho substitution causes lowering of conductivity of PABS and its Na-salt which was found to be 5.4×10−5 S/cm and 2.4×10−6 S/cm, respectively. The ESR spectra show that the polymer to be strongly paramagnetic with a g value of 2.0013.
Poly(2,5-dimethoxyaniline) (PDMA) is obtained either from chemical oxidation with ammonium peroxydisulfate or from electro-oxidation of the corresponding monomer in aqueous hydrochloric acid. UV-Vis, 1H NMR and FT-IR spectroscopic data, and voltammetric studies are presented to demonstrate that the chemically and electrochemically prepared PDMA samples have essentially the same properties. The voltammetry of PDMA-coated electrodes is described. It is shown that the PDMA film efficiently catalyses the proton-dependent benzoquinone-hydroquinone couple. Studies of the electropolymerization of PDMA from different aqueous acids reveal that the anion determines the surface morphology of the film deposited on the electrode. Preliminary results of the dependence of PDMA conductivity on pH are also presented.
Sulfonated polyaniline (SPAN) was synthesized by sulfonation of polyaniline (PANI) base with fuming sulfuric acid. Thin films were cast from polymer solutions in basic media. The polymer films were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible–near-infrared spectroscopy, scanning electron microscopy (SEM) and cyclic voltammetry. XPS in combination with FTIR showed that the preparation procedure led to ca. 47% sulfonation of an otherwise unchanged polyaniline backbone. The NIR spectra of SPAN films showed a polaron band at higher energies than with polyaniline. This is in agreement with the lower conductivity of SPAN as compared with polyaniline. SEM micrographs of the SPAN films showed a compact globular morphology. Electrodes modified with thin SPAN films exhibited two redox steps, both in aqueous and in non-aqueous electrolytes. The specific charge stored in SPAN films was found to be ca. 37 A h kg–1 in aqueous solution (only the first redox step) and ca. 68 A h kg–1 in non-aqueous media (both redox steps). A practical SPAN–Li battery could have 50% more specific energy than a PANI–Li battery. The optical spectra of SPAN films exhibited bands at 310, 450 and 750 nm, the intensities of which changed during the redox process. The absorption coefficients of SPAN (emeraldine base state) solutions had values of a= 410 at 313 nm and a= 239 at 563 nm. The suitability of SPAN for use as a cation-insertion material for battery and electrochromic applications is discussed.
The bimolecular rate constant for the reaction of H + SO2 --> products (1) was determined to be k(1) = 1.0 x 10(-11) exp(-66.1 kJ(.)mol(-1)/RT) cm(3) molecules(-1) s(-1) in the temperature range of 1400-2200 K by measuring the temporal profiles of H atoms behind the reflected shock Of C2H5I/SO2/Ar mixtures. The rate constant obtained in this study is in good agreement with that calculated using the rate constants of the reverse reaction OH + SO --> H + SO2 and is also consistent with the rate constants predicted by the master equation analysis.
Poly(ethylene oxide) (PEO), soluble in both water and many organic solvents, is grafted onto single-walled carbon nanotubes (SWNTs), and aggregation behaviors of the resulting PEO-graft-SWNT in solutions and in Langmuir−Blodgett (LB) films are investigated. SWNTs, cleaved by acid, are dispersed relatively well in DMF and water, but poorly in chloroform and THF. PEO-graft-SWNT was synthesized by treating acid-cut SWNTs with SOCl2, followed by a reaction with monoamine-terminated PEO in a DMF and water medium. Atomic force microscopy reveals that PEO and SWNT segments take expanded and extended conformations when freshly prepared PEO-graft-SWNTs are cast from water. When PEO-graft-SWNTs are dispersed in chloroform, each SWNT segment collapses into a globular aggregate. Aging the chloroform dispersion produces self-organized structures detectable by light scattering. Langmuir−Blodgett films made from this aged solution afford a surface-micelle structure in which the coagulated collapsed SWNT core is surrounded by extended PEO patches. Addition of DMF to this chloroform solution re-expands the SWNT segments, although not completely. These results demonstrate that the conformation of SWNTs can be controlled by solvent quality as if they are ordinary hydrocarbon-based block copolymers. Yet, the conformational change is not completely reversible, and coagulation, rather than entanglement, becomes the major event even at locally concentrated regions.
We have prepared new soluble conducting polymer-dye composite and photovoltaic cells with three different architectures using soluble conducting polymer (CP) as hole transport material and N, N '- diphenyl glyoxaline -3, 4, 9, 10 - perylene tetracarboxylic acid diacidamide (PV) as electron transport material. These architectures comprise a single-layer structure (ITO/CP+PV/A1) and a double-layer structure (ITO/CP+PV/PV/A1) as well as a three layer structure (ITO/CP+C-60/CP+PV/PV/A1). Electrical and optical properties of soluble conducting polymer-dye composite, current-voltage (W) characteristics and photocurrent spectra have been discussed. Our results show that soluble conjugated polymer composite represents a new class of organic semiconducting materials that can be used to manufacture photovoltaic cells.
The pH of aqueous solutions in the vicinity of a thin self-doped conducting polyaniline electrode was electrochemically modulated using both cyclic voltammetry and step potential techniques. Changes in pH were measured directly by using a microcombination pH probe. The experimental results demonstrate that the polymer behaves as a proton ejector during oxidation and a proton absorber during reduction. This potential-controlled pH change near the polymer coated electrode may be applied to many fields benefitting from electronic control of the proton environment near an electrode surface, for example, control of enzyme activity.
Schottky diodes were fabricated using aluminum/neutralized-sulfonated-polyaniline (SPAN) junctions. I–V and C–V measurements were made, and the barrier height (ΦB) and the background concentration (NB) were determined to be 0.8 V and 4×1017/cm3, respectively. Using these diodes as gate control, depletion-mode thin-film transistors were fabricated with a source and drain made of gold Ohmic contacts. The transistors were characterized by I–V measurements, and the carrier mobility determined from devices operating in the ∣VG∣>∣VDS∣ “linear” regime was about 0.01 cm2/V s. This high value of mobility could be attributed to the spherulitic (partially ordered) structures observed in the SPAN thin films. Field-effect transistors were also fabricated on SPAN films deposited on an n-doped silicon substrate acting as the gate electrode with a thermally grown oxide layer. A reasonably high on/off ratio ( ∼ 4×103) was measured in these devices. © 1998 American Institute of Physics.
Single-walled carbon nanotube (SWNT) reinforced polymer composite membranes have been fabricated using the electrospinning technique. Nanofibers with a diameter in the range 50−100 nm were obtained by electrospinning SWNT-filled polystyrene composites. TEM observations revealed incorporation of small SWNT bundles oriented parallel to the nanofiber axis. As-prepared (AP) and ester (EST) functionalized SWNTs have been electrospun with polyurethane (PU) to demonstrate the effect of the chemical functionalization of SWNTs on the mechanical properties of SWNT-reinforced composites. The tensile strength of EST-SWNT-PU membranes is enhanced by 104% as compared to electrospun pure polyurethane membranes, while an increase of only 46% was achieved incorporating AP−SWNT in the polyurethane matrix. The tangent moduli of AP- and EST-SWNT-PU membranes were found to be respectively 215% and 250% higher than the control polyurethane membranes.
In this communication, we show that aryldiazonium salts can react efficiently with individual SDS-coated SWNTs in water to form aryl functionalized SWNTs. Remarkably, the resulting SWNTs have up to 1 in 9 carbons along their backbones bearing an organic moiety and they remain unbundled throughout their entire lengths, even with these relatively small functional moieties.
Poly(vinyl alcohol) (PVA) composite films using poly(vinyl pyrrolidone) (PVP) and sodium dodecyl sulfate (SDS)-covered, well dispersed single wall carbon nanotubes (SWNT) exhibit significant improvement in tensile strength and modulus as compared to the control PVA and PVA/PVP/SDS films. The evidence of load transfer to the nanotubes in the composite film has been obtained from the shift in the Raman SWNT D* band peak position.
We report a rapid, quantitative procedure for the evaluation of the carbonaceous purity of bulk quantities of as-prepared single-walled carbon nanotube (SWNT) soot by the utilization of solution-phase near-IR spectroscopy. The procedure starts with two steps of homogenization followed by solution/dispersion spectroscopy of a representative part of the bulk sample. The purity is evaluated against a reference sample by utilizing the region of the second interband transition (S22) for semiconducting SWNTs. The procedure is found to be capable of reliably analyzing the carbonaceous purity of a 10-g batch of SWNTs produced by the electric arc discharge method to within 3%.
We report a simple process to solubilize high weight fraction single-wall carbon nanotubes in water by the nonspecific physical adsorption of sodium dodecylbenzene sulfonate. The diameter distribution of nanotubes in the dispersion, measured by atomic force microscopy, showed that even at 20 mg/mL 63 ± 5% of single-wall carbon nanotube bundles exfoliated into single tubes. A measure of the length distribution of the nanotubes showed that our dispersion technique reduced nanotube fragmentation.
The solubilization of oxidized carbon nanotubes has been achieved through derivatization using a functionalized organic crown ether. The resultant synthesized adduct yielded concentrations of dissolved nanotubes on the order of 1 g/L in water as well as in methanol, according to optical measurements. The nanotube−crown ether adduct can be readily redissolved in 10 different organic solvents at substantially high concentrations. Characterization of these solubilized adducts was performed with 1H NMR spectroscopy; 7Li NMR was also used to examine the ability of the crown ether's macrocyclic ring to bind Li+ ions. The solutions were further analyzed using UV−visible, photoluminescence, and FT-IR spectroscopies and were structurally characterized using atomic force microscopy (AFM) and transmission electron microscopy (TEM). Adduct formation likely results from a noncovalent chemical interaction between carboxylic groups on the oxidized tubes and amine moieties attached to the side chain of the crown ether derivative.
Single-walled carbon nanotubes (SWNT) were covalently modified with DNA via carbodiimide-assisted amidation, yielding a highly water-soluble adduct. The specific and nonspecific interactions between DNA and SWNTs were examined by UV−vis spectroscopy and confocal fluorescence microscopy. Fluorescence imaging of individual bundles shows that the SWNT−DNA adducts hybridize selectively with complementary strands with minimal nonspecific interactions with noncomplementary sequences.
Soluble samples of single-wall and multiple-wall carbon nanotubes that are functionalized by lipophilic and hydrophilic dendra can be defunctionalized in homogeneous solutions under base- and acid-catalyzed hydrolysis reaction conditions. The results provide strong evidence for the ester linkages in the functionalization of carbon nanotubes.
Water solubilization of single-walled carbon nanotubes (SWNTs) has been achieved by functionalizing the SWNT with glucosamine. The grafting of glucosamine to the nanotubes was attained by producing acyl chloride on the carboxylic groups associated with the nanotubes. Subsequently, amide bonds were formed between the glucosamine and the SWNT. This grafting results in solubility of SWNT in water, which ranges from 0.1 to 0.3 mg/mL, depending on temperature.
Atomic scale imaging using scanning tunneling microscopy has been used to investigate the morphology and structure of high molecular weight polymers attached to carbon nanotubes. A surprising degree of regularity is observed in the attached polymers, suggesting a “nanotube-driven” crystallization process is present. The symmetries of this crystalline state of the polymer are directly determined by the underlying nanotube's chirality. Tunneling spectroscopy further demonstrates that the crystallization of the polymer onto the nanotube results in modifications to the nanotube's electronic structure, as would be expected from a strong polymer−tube interaction. The assembly of nanoscale organics into objects with such perfect order clearly foreshadows the construction of large-scale nanoarchitectures with order over many lengths scales.
Carbon nanotubes are functionalized by bovine serum albumin (BSA) proteins via diimide-activated amidation under ambient conditions. The nanotube-BSA conjugates thus obtained are highly water-soluble, forming dark-colored aqueous solutions. Results from characterizations using atomic force microscopy (AFM), thermal gravimetric analysis, Raman, and gel electrophoresis show that the conjugate samples indeed contain both carbon nanotubes and BSA proteins and that the protein species are intimately associated with the nanotubes. Bioactivities of the nanotube-bound proteins are evaluated using the total protein micro-determination assay (the modified Lowry procedure). The results show that the overwhelming majority (90%) of the protein species in the nanotube-BSA conjugates remain bioactive.
Carbon nanotubes were solubilized via functionalization with poly(propionylethylenimine-co-ethylenimine). The diimide-activated amidation reaction for the functionalization was found to be significantly improved in both efficiency and yield by sonication under ambient conditions. It was also found that depending on the duration of sonication the nanotubes were shortened to different lengths in the functionalization reactions. The method allows relatively efficient preparation of solubilized carbon nanotubes of potentially a selectable average length.
Single-wall carbon nanotubes pack into crystalline ropes that aggregate into tangled networks due to strong van der Waals attraction. Aggregation acts as an obstacle to most applications, and diminishes the special properties of the individual tubes. We describe a simple procedure for dispersing as-produced nanotubes powder in aqueous solutions of Gum Arabic. In a single step, a stable dispersion of full-length, well separated, individual tubes is formed, apparently due to physical adsorption of the polymer.
Single-walled and multiple-walled carbon nanotubes were functionalized with a polystyrene copolymer, poly(styrene-co-p-(4-(4‘-vinylphenyl)-3-oxabutanol)). The functionalization reaction conditions were designed for the esterification of the nanotube-bound carboxylic acids. The polymer-attached carbon nanotubes are soluble in common organic solvents, making it possible to characterize the samples using not only solid-state but also solution-based techniques. The solubility has also allowed an intimate mixing of the functionalized carbon nanotubes with polystyrene. Results from the characterization of the functionalized carbon nanotubes, including the chemical and thermal defunctionalizations of the soluble samples, and the fabrication of polystyrene−carbon nanotube composite thin films using a wet-casting method are presented and discussed.
The layer-by-layer molecular-level manipulation of conjugated polyions has been successfully utilized to fabricate ultrathin multilayer films and multilayer heterostructures. Through a process involving the alternate spontaneous adsorption of oppositely charged polymers from dilute aqueous solutions, multilayer thin films were fabricated from a variety of different bilayer combinations including conjugated/nonconjugated polyion bilayers, conjugated/conjugated polyion bilayers, and precursor polymer/conjugated polyion bilayers. UV-vis absorbance measurements revealed that in all cases the bilayer deposition process was linear and highly reproducible from layer to layer. Kinetic studies showed that the equilibrium adsorption of a polyion layer is reached within about 10 min and the process can be carried out onto different substrate surfaces. The typical bilayer thickness ranges from approximately 10 to 25 Angstrom and can be readily controlled by variations in such parameters as solution concentration, pH, doping level, and ionic strength.
Electrostatic interactions between shortend multiwall carbon nanotubes (sMWNCNTs) and polyelectrolytes were presented. An experimental foundations of sMWCNTs suspensions' colloidal stability in aqueous media was analyzed. The rheology of sMWCNTs and polyelctrolyres in solution indicated interactions of the charged species. The results allowed to understand the functionalization of sMWNCNTs, to manipulate sMWNCNT/polyelectrolyte composites for various applications and to control the stability and electrostatic interactions of sMWNCNTs in water.
Nanocomposites of multiwalled carbon nanotubes (MWNTs) embedded in poly(o-anisidine) (POAS) were synthesized by oxidative polymerization and characterized using a combination of various techniques. The Langmuir monolayer behavior of POAS−carbon nanotubes (CNTs) conducting polymer was investigated at the air−water interface. The Langmuir−Schaefer (LS) films of POAS−MWNTs were prepared at a subphase of pH. A uniform deposition of monolayers was studied by optical and quartz crystal microbalance techniques, respectively. The nature of the anions in electrochemical investigations revealed significant changes in the redox properties of the POAS−MWNTs LS films. The cyclic voltammetric study revealed a highly electrochemical resistive LS film. The photoelectrochemical current transient of POAS−MWNT LS films was investigated in different electrolytic solutions.
This study demonstrates a novel approach toward development of advanced chemical sensors based on chemically functionalized single-walled carbon nanotubes (SWNTs). SWNTs with covalently attached poly(m-aminobenzene sulfonic acid), SWNT-PABS, have shown improved sensor performance for detection of NH3. Compared to purified SWNTs, devices fabricated with SWNT-PABS have shown more than 2 times higher change of resistance upon exposure to NH3. Importantly, the SWNT-PABS sensors rapidly recover their resistance when NH3 is replaced with nitrogen. Exposure to NH3 induces significant changes in the electronic structure of SWNT-PABS, which allow detection of NH3 at concentrations as low as 5 ppm. Thin film deposited between interdigitated electrodes was explored as a device configuration for development of gas sensors.
The measurement of the bulk purity of single-walled carbon nanotubes (SWNTs) is an important outstanding problem. We report a solution-phase near-IR (NIR) spectroscopic study of a range of carbon materials with an emphasis on SWNTs, and we show that NIR spectroscopy is an extremely powerful tool in the assessment of the carbonaceous purity of SWNTs. We demonstrate the applicability of Beer's law for all of the carbon materials included in this study within a range of concentrations in dimethylformamide (DMF), and we are able to solve for the effective extinction coefficients. By analyzing the areal absorptivities of the second interband transition of semiconducting SWNTs for a number of samples of differing purities, we are able to derive an absolute molar extinction coefficient for the carbonaceous impurities in SWNT samples. We demonstrate significant progress toward the establishment of an absolute scale for the bulk carbonaceous purity of SWNTs.
We report a systematic evaluation of the use of refluxing nitric acid as a purification treatment for electric arc-produced single-walled carbon nanotubes (SWNTs), by using a combination of thermogravimetric analysis (TGA) and near-infrared (NIR) spectroscopy. Nitric acid is the standard reagent for purification of SWNTs and has traditionally constituted the first step in many different purification schemes. It has been suggested that nitric acid removes the transition metal catalyst that is used in the production of the SWNTs together with amorphous carbon. Under all conditions, we find that nitric acid destroys SWNTs to produce amorphous carbon while reducing the amount of transition metal catalyst remaining in the sample. Thus, nitric acid is suitable for removing the catalyst from SWNT samples, but only at the expense of a significant destruction of the SWNTs.
Single-walled carbon nanotubes (SWNTs) were solubilized by attaching functional groups to the nanotube-bound carboxylic acids in the esterification and various amidation reactions. The solubility made it possible to not only characterize the functionalized SWNT samples in solution but also quantitatively measure the UV/vis/NIR absorption spectra of the samples. The nanotube contents in the soluble samples were determined in terms of NMR signal integrations in reference to internal standards and through thermal gravimetric analyses. The absorptivity results thus obtained are similar for SWNTs in the different functionalized samples. For the near-infrared absorption band corresponding to the first pair of van Hove singularities in the electronic density of states for semiconducting SWNTs, the peak absorptivity is 0.5−2.2 (mg/mL)-1 cm-1. The absorption properties of SWNTs are apparently insensitive to changes in the sample environment, such as the functionalization with significantly different groups. The effects of scattering on the accurate determination of absorptivity are discussed.
Multiple-walled carbon nanotubes (MWNTs) produced using the chemical vapor deposition method were functionalized via attaching aminopolymer poly(propionylethylenimine-co-ethylenimine) to the nanotubes. Two different reaction conditions based on acylating the nanotube-bound carboxylic acids and on directly heating nanotubes in the polymer melt were used and compared. Both methods were effective in the nanotube functionalization, and the polymer-attached MWNTs were found to be soluble in many common organic solvents and in water. Results from the characterization of the functionalized nanotube samples using electron microscopy, optical spectroscopy, NMR, and thermal analysis techniques are presented and discussed.
Full and shortened single-walled and multiple-walled carbon nanotubes were suspended in water to form stable suspensions in the presence of a surfactant. Optical limiting properties of the suspensions were determined for 532-nm pulsed laser irradiation, and the results were comparable with those of carbon black aqueous suspension. Solubilization of the shortened carbon nanotubes was achieved by attaching the nanotubes to highly soluble poly(propionylethylenimine-co-ethylenimine) or by functionalizing the nanotubes with octadecylamine. The soluble carbon nanotube samples formed homogeneous solutions in room-temperature chloroform. Optical limiting properties of these solutions were also determined for 532-nm pulsed laser irradiation, and the results were found to be quite different from those of the carbon nanotube aqueous suspensions. Apparently, the carbon nanotubes exhibit significantly weaker optical limiting responses in homogeneous solutions than in suspensions. Mechanistic implications of the experimental results are discussed.
Sulfonated polyaniline (SPAN) is a self-doped conducting polymer. It has a high water solubility and a novel pH-dependent DC conductivity that is of interest for fundamental science and also for applications in such areas as rechargeable battery and pH control technologies. We report here the extensive characterization and details of synthesis of a new form of sulfonated polyaniline (LEB-SPAN) which shows novel or significantly improved chemical and physical properties. LEB-SPAN has a high sulfur to nitrogen ratio (S/N) of 0.75, 50% larger than that previously reported for EB-SPAN, S/N 0.50. This change in composition leads to significant alteration of the properties including an order of magnitude increase in the room temperature DC conductivity to 1 S·cm-1, nearly double the solubility in water, and a completely different pH dependence of the oxidation potential (E1/2). For LEB-SPAN the DC conductivity is unaffected by pH over the range 0 ≤ pH ≤ 14, strikingly different from the behavior of both parent polyaniline and EB-SPAN which become insulating for pH ≥3 and ≥7.5, respectively. Temperature-dependent DC conductivity and EPR measurements for LEB-SPAN reveal a lower activation energy for the conductivity and a higher density of states at the Fermi energy as compared with EB-SPAN. The dramatic differences in the pH dependence of the DC conductivity, cyclic voltammetry (CV), FTIR, and UV−vis results for LEB-SPAN and EB-SPAN are shown to be a consequence of the much higher S/N ratio in LEB-SPAN. We propose and describe a novel quasi-random oxidation model for the electrochemical oxidation of polyaniline and its derivatives at the microscopic level. This model quantitatively describes many of the phenomena and physical properties found in the polyanilines including the origin of the defect states and the in situ EPR signal during CV potential scans. Also the statistical nature of this model suggests its general applicability to the oxidation process of other conducting polymers. Computer simulations based on this model are presented and show good agreement with the in situ EPR/CV data reported earlier. In addition, other models are proposed to interpret the reported experimental differences in the pH dependence of E1/2 among LEB-SPAN, EB-SPAN, and its parent polyaniline samples. Mechanisms for the new sulfonation route are proposed.
The water-soluble self-acid-doped conducting polyaniline poly(aniline-co-N-propanesulfonic acid aniline) (PAPSAH) with an oxidation level of about 0.5 in aqueous solution and as a solid film has been characterized. Elemental analysis and spectroscopic data show that almost each amine nitrogen (approximatly 50% of the total nitrogen) in the polymer is linked with a -(CH2)(3)SO3H group, in which the proton is capable of doping the quinoid unit of the polymer. Titration analysis and spectroscopic data of the polymer in aqueous solution and as a solid film, respectively, show that suprisingly the fractions of -(CH2)(3)SO3H groups that protonate (dope) the imine nitrogens to give semiquinone radical cations are equal in both cases, about 0.66 (equivalent to the doping level, 0.33). However, the free spins in the aqueous solution are more localized than those in the solid film. The fractions of proton, about 34%, that do not participate in the doping have no effect on the conductivity of the film. As the doping level is reduced by increasing the degree of neutralization, the conductivity drops by a factor of 10(4) at the doping level of zero. The conductivity, UV-vis spectroscopy, and X-ray diffraction pattern of the polymer, in comparison with those of HCl-doped polyaniline, exhibit that the decreases of polaron delocalization and structural order result from the steric hindrance imparted by the substituent alkanesulfonic acid. The conductivity of PAPSAH film (at 25 degrees C, 10(-2) S/cm) increases with temperature from -50 degrees C (10(-8) S/cm) to +110 degrees C (10(-1) S/cm) due to thermal activation, and decreases with temperature from 110 to 170 degrees C (10(-5) S/cm) due to thermal undoping accompanied by the loss of some polarons. After the heating scan, the conductivity at room temperature drops by a factor of 10(3). Cyclic voltammetry of the polymer coated on a platinum electrode in aqueous acid solutions shows two redox reactions between -0.2 and +0.8 V vs SCE. The two oxidation potentials are dependent on pH in the range -0.05 to +2.09. During the redox process; the PAPSAH film exhibits reversible color changes from pale yellow to green to blue as in the case of polyaniline.
Poly(o-toluidine), poly(m-toluidine), and poly(o-ethylaniline) have been synthesized chemically and electrochemically. The polymers were characterized by elemental analysis, UV-vis spectroscopy, and cyclic voltammetry. Elemental analysis data suggest that the protonated polymers are derived from bases containing ca. 37-54% oxidized (imine) units. Upon treatment with 1 M HCl, conductivities of the polymers increase dramatically from ca. 10-8 S/cm to ca. 10-1 S/cm for polytoluidines and to ca. 10-3S/cm for poly(o-ethylaniline). The conductivities, UV-vis spectra, and electrochemical reactions of the polymers are compared with those of polyaniline and are shown to be consistent with a reduction in π-conjugation of the alkyl derivatives caused primarily by steric effects.
Electric-arc produced as-prepared single-walled carbon nanotube (AP-SWNT) films have been purified by a selective oxidation process. The purification is monitored by near-infrared (NIR) spectroscopy, which gives a quantitative estimate of relative purities. This technique also gives an estimate of the change in relative amounts of SWNTs and amorphous carbon impurities after each purification step, thereby providing accurate and selective control over the oxidation process. Oxidation was carried out by reaction in flowing oxygen at different temperatures and for different durations of time; the purity was evaluated after each oxidation step and compared to the starting as-prepared film. The purities and amounts of SWNTs and carbonaceous impurities were monitored as a function of oxidation temperature and time. Optimization of the process allowed a 3-fold improvement in the AP-SWNT purity with almost quantitative retention of the SWNT portion of the sample. A purification efficiency is defined, which is expressed as the ratio of the fraction of SWNTs retained to the fraction of impurities retained in the sample after application of the purification process.
Preparation of carbon nanotube (CNT)/alumina composites by a simple colloidal processing method has been reported in this paper. The surface modification process of carbon nanotubes was characterized by means of zeta potential measurements and TEM microscopy. The addition of only 0.1 wt % carbon nanotubes in the alumina composite increases the fracture toughness from 3.7 to 4.9 MPa·m1/2. Microstructure characterization, performed by SEM, showed that the bridging effect on cracks, the tight bonding between CNTs and alumina matrix, and the pullout of CNTs from matrix are possible mechanisms leading to the improvement of the fracture toughness.
Lipophilic and hydrophilic dendra which are terminated with long alkyl chains and oligomeric poly(ethylene glycol) moieties, respectively, were synthesized, and these dendron species were used to functionalize single-wall (SWNT) and multiple-wall (MWNT) carbon nanotubes via amidation and esterification reactions. The functionalized carbon nanotube samples are, depending on the functionalities, soluble in common organic solvents, such as hexane and chloroform, and water to form colored homogeneous solutions. Characterizations using NMR, electron microscopy, and optical spectroscopic techniques show that the homogeneous solutions contain carbon nanotubes. A preliminary understanding of the structural features and properties of these soluble dendron-functionalized SWNTs and MWNTs is discussed in terms of results from the characterizations, the defunctionalization reactions, and the trapping of metal nanoparticles by the functionalized nanotubes in solution.
Polyaniline/multiwalled carbon nanotube composite films were prepared by the in-situ and ex-situ methods. As such, the composites exhibited an order of magnitude increase in electrical conductivity over neat polyaniline (PANI). Infrared spectroscopy studies how for the first time that multi-walled and single-walled carbon nanotubes (MWNTs) affect both the free N-H environment and quinoid units along the polymer backbone and perhaps describe the strong interactions between the nanotubes and PANI.
Communication: The solubility properties of single-walled carbon nanotubes (SWNTs) and the factors that control the dissolution of these materials have been investigated in detail. The authors report a number of strategies that lead to soluble SWNTs, in particular the covalent attachment of long alkyl chains to the carboxylic acid-terminated SWNTs shown in the Figure (produced by the purification process) via formation of amides and by formation of zwitterions by an acid-base reaction.
The chemical copolymers of m-aminobenzene sulfonic acid with O-anisidine (POABSA) and O-toluidine (POTBSA) have been synthesized. Polymers are water soluble and self-doped. The peak in IR spectra at 1100–1160 cm−1 shows the presence of SO3 group in the polymer backbone. Self-doped copolymers exhibit a strong and wide range of polaron absorption at 772–943 nm in m-cresol, due to the conformational changes induced by polymer solvent interaction. Copolymers also display a strong polaron transition in m-cresol with LiCl. Salt acts as a pseudo-doping agent and extends ‘coil-like’ conformations. The highest thermal activation is monitored at 70 °C, above that temperature (<100 °C) overcompensation of thermal activation effect is observed. The electrical conductivity of copolymers is low (10−4 to 10−5 S cm−1), caused by strong steric effect between SO3 and OMe/Me groups.
Probe Beam Deflection and Quartz Crystal Microbalance were used to study the ion exchange mechanism of polyaniline (PANI) and sulfonated polyaniline (SPAN). Anions are predominantly used as charge compensating species in the first oxidation step of PANI at high pH (>2). Protons plus anions are expelled during the second oxidation step. In the case of SPAN, protons are expelled during the first and second oxidation step. In a nonaqueous electrolyte anions are exchanged during both oxidation steps of PANI, while expulsion of cations seems to be the dominant flux during SPAN oxidation. The charge density of SPAN is found to be ca. 44Ah/kg. The electrochromic properties of SPAN are similar to those of PANI.
Poly(m-aminobenzene sulfonic acid) (PABS), was covalently bonded to single-walled carbon nanotubes (SWNTs) to form a water-soluble nanotube–polymer compound (SWNT–PABS). The conductivity of the SWNT–PABS graft copolymer was about 5.6 × 10–3 S cm–1, which is much higher than that of neat PABS (5.4 × 10–7 S cm–1). The mid-IR spectrum confirmed the formation of an amide bond between the SWNTs and PABS. The 1H NMR spectrum of SWNT–PABS showed the absence of free PABS, while the UV/VIS/NIR spectrum of SWNT–PABS showed the presence of the interband transitions of the semiconducting SWNTs and an absorption at 17 750 cm–1 due to the PABS addend.