Edge-Functionalization of Pyrene as a Miniature Graphene via Friedel-Crafts Acylation Reaction in Poly(Phosphoric Acid)

The feasibility of edge-functionalization of graphite was tested via the model reaction between pyrene and 4-(2,4,6-trimethylphenyloxy)benzamide (TMPBA) in poly(phosphoric acid) (PPA)/phosphorous pentoxide (P(2)O(5)) medium. The functionalization was confirmed by various characterization techniques. On the basis of the model study, the reaction condition could be extended to the edge-functionalization of graphite with TMPBA. Preliminary results showed that the resultant TMPBA-grafted graphite (graphite-g-TMPBA) was found to be readily dispersible in N-methyl-2-pyrrolidone (NMP) and can be used as a precursor for edge-functionalized graphene (EFG).     

One-pot purification and functionalization of single-walled carbon nanotubes in less-corrosive poly(phosphoric acid)

As-received commercial single-walled carbon nanotubes (SWCNTs) were treated in mild, inorganic polyacid, viz. polyphosphoric acid (PPA) with or without additional phosphorous pentoxide (P₂O₅) at 130, 160, and 190 °C. Unlike the treatment in strong acids such as nitric acid/sulfuric acid mixtures, nitric acid and hydrochloric acid, PPA with or without additional P₂O₅ could selectively remove the tenacious carbonaceous and metallic impurities with little or no damage to the basic frameworks of SWCNTs and crystalline carbon materials. Since the medium PPA/P₂O₅ is known for an efficient “direct” Friedel-Crafts acylation using a carboxylic acid instead of a carboxylic acid chloride, it provides the advantage of combining both purification and functionalization steps into a one-pot process in manufacturing of functionalized SWCNTs.     

Highly efficient recovery of bioactive ingredients from solid waste of onions onto functionalized SWCNTs supported on amberlite nanocomposite

Preparation of single-walled carbon nanotubes (SWCNTs) with carboxylic (–COOH) acid was executed by functionalization with amine functional groups (–NH2). The obtained functionalized SWCNTs were supported by macroporous resin (amberlite XAD-7HP). The synthesized nanocomposite has been characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) methods. FTIR analysis indicates that functionalized SWCNTs supported onto the amberlite resin were synthesized successfully. The surface morphology of the nanomaterial was also successfully embedded into the amberlite of the functionalized SWCNTs. Huge solid residues of onions are produced as agricultural and food wastes each year. The related biowaste includes biologically active phenolic compounds which have positive effects with strong antioxidant properties on human health when properly isolated and concentrated. In the present research, functionalized SWCNTs have been utilized for the separation of bioactive phenolics from onion waste extracts. Equilibrium (Langmuir, Freundlich and Toth) and kinetic (pseudo-first order, pseudo-second order, intraparticular diffusion and Elovich) models have been applied for analysis and representation of data. Pseudo-second-order model is in good agreement with the experimental data. On the other hand, the equilibrium findings were represented best with Freundlich isotherm model. Additionally, thermodynamic indicators have also demonstrated that the current system is a spontaneous and exothermic chemisorption process.     

Carbon nano-tube supported Pt–Pd as methanol-resistant oxygen reduction electrocatalyts for enhancing catalytic activity in DMFCs

This work tries to study the problem of methanol crossover through the polymer electrolyte in direct methanol fuel cells (DMFCs) by developing new cathode electrocatalysts. For this purpose, a series of gas diffusion electrodes (GDEs) were prepared by using single-walled carbon nanotubes (SWCNTs) supported Pt–Pd (Pt–Pd/SWCNT) with different Pd contents at the fixed metal loading of 50 wt%, as bimetallic electrocatalysts, in the catalyst layer. Pt–Pd/SWCNT was prepared by depositing the Pt and Pd nanoparticles on a SWCNTs support. The elemental compositions of bimetallic catalysts were characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES) system. The performances of the GDEs in the methanol oxidation reaction (MOR) and in the oxygen reduction reaction with/without the effect of methanol oxidation reaction were investigated by means of electrochemical techniques: cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS). The results indicated that GDEs with Pt–Pd/SWCNT possess excellent electrocatalytic properties for oxygen reduction reaction in the presence of methanol, which can originate from the presence of Pd atoms and from the composition effect.     

Modification of fluorinated single-walled carbon nanotubes with aminosilane molecules

Single-walled carbon nanotubes (SWCNTs) modified with amino groups were prepared via chemical addition of fluorine on the carbon nanotube surface by plasma treatment. The amino termination makes possible to realize hybrid nanostructures made out of SWCNTs and alkoxy-silane (3′-(aminopropyl)tri-ethoxysilane (APTES)) molecules. The functionalization of the SWCNTs was evidenced by transmission electron microscopy, infrared spectroscopy and thermogravimetric measurements. It was found that the application of a dc electric field enhances the assembly of APTES modified SWCNTs into ordered films with rectifying diode behavior.     

Dispersion of non-covalently functionalized single-walled carbon nanotubes with high aspect ratios using poly(2-dimethylaminoethyl methacrylate-co-styrene)

Single-walled carbon nanotubes (SWCNTs) with high aspect ratios were well dispersed in organic solvents to form stable suspensions using poly(2-dimethylaminoethyl methacrylate-co-styrene) (poly(DMAEMA-co-St)). The polymeric dispersant poly(DMAEMA-co-St) was synthesized in various compositions by atom transfer radical polymerization. The structures and the compositions of the poly(DMAEMA-co-St) were confirmed by ¹H NMR spectroscopy. The stability and dispersion of the functionalized SWCNTs with high aspect ratios in suspension were observed by dispersion stability analysis, transmission electron microscopy, scanning electron microscopy, and atomic force microscopy. The existence of unbundled SWCNTs was confirmed by Raman and ultraviolet/visible/near-infrared spectroscopy. Finally, SWCNT transparent conductive films with high transmittances and low sheet resistances were prepared on a poly(ethylene terephthalate) substrate using a spin-coating method.     

Preparation of nanocrystalline titanium carbonitride coatings using Ti(N(Et)<Subscript>2</Subscript>)<Subscript>4</Subscript>

Titanium carbonitride films with a thickness of 80–150 nm have been synthesized by low pressure chemical vapor deposition from a gas mixture of tetrakis(diethylamino)titanium and ammonia at temperatures of 773–973 K. The film properties have been studied by spectroscopy (IR, XPS, and EDS), scanning electron and atomic force microscopy, and ellipsometry. The studies have shown that the films consist of polycrystals with a size of 15–80 nm; their structure contains chemical bonds of titanium with atoms of carbon, nitrogen, and oxygen. The film composition is consistent with the data of the previously performed thermodynamic modeling of the deposition of different condensed phases in the Ti-C-N-H-O system. As the deposition temperature increases in the range under study, the refractive index of the films increases from 2.1 to 2.7.     

High-dielectric constant percolative composite of P(VDF-TrFE) and modified multi-walled carbon-nanotubes

To develop a high-dielectric constant composite of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] and multi-walled carbon-nanotubes (MWCNTs) with desirable homogeneity, MWCNTs were treated with a nitro-sulfuric acid by ultrasonication. The chemically modified MWCNTs (a-MWCNTs) were characterized by Fourier transform infrared spectroscopy and a back-titration procedure. Improvement of the dispersibility of a-MWCNTs in polymer matrix, in comparison with unmodified MWCNTs in P(VDF-TrFE), was confirmed by field emission scanning electron microscopy. Electric behavior of the composites with different volume fraction of dispersed carbon nanotubes can be described by percolation theory, as well as the Maxwell–Wagner–Sillars mechanism. The percolation threshold (f _c ) of composites with a-MWCNTs (f _c  = 0.0308) is larger than that of composites with MWCNTs (f _c  = 0.0216) due to better dispersion of a-MWCNTs in matrix and the reduction of aspect ratio of a-MWCNTs occurred in the modification procedure. The composite with 2.98 vol% (close to the percolation threshold) of a-MWCNTs has a dielectric constant of 592 at 100 Hz and room temperature.     

Fabrication of single-wall carbon nanotubes within the channels of a mesoporous material by catalyst-supported chemical vapor deposition

Diameter-controlled single-wall carbon nanotubes (SWCNTs) have been synthesized using Co, Fe/Co and Rh/Pd alloy nanoparticles trapped within the one-dimensional channels of a mesoporous materials (Folded Sheets Mesoporous material: FSM-16) by catalyst-supported chemical vapor deposition (CCVD) using ethanol as carbon source at 973-1173 K. The SWCNTs synthesized are characterized by transmission electron microscopy, Raman spectroscopy and photoluminescence spectroscopy. The yield, diameter distribution and quality of the SWCNTs strongly depend on the reaction temperature during CCVD. The product synthesized at 1173 K contains only SWCNTs, in marked contrast to those synthesized at lower temperatures. As the reaction temperature decreases, the relative abundance of multi-wall carbon nanotubes against SWCNTs significantly increases, whereas the mean diameter of SWCNTs increases as reaction temperature increases. The results show that a careful control of the reaction temperature is crucial to fabricate diameter-controlled SWCNTs from the channels of FSM-16.     

The influence of single-walled carbon nanotube functionalization on the electronic properties of their polyaniline composites

The “in situ” preparation and characterization of composites of polyaniline (PANI) and single-walled carbon nanotubes (SWCNTs) are reported. To improve the dispersion and compatibility with the polymer matrix the raw SWCNTs were modified following different routes. SWCNTs oxidized by chemical or thermal treatments (nitric acid and air oxidation, respectively) were subjected to covalent functionalization with octadecylamine (ODA). SWCNT/PANI composites were prepared either from just oxidized SWCNTs, or from ODA functionalized SWCNTs. Temperature-programmed desorption, elemental analyses, ultraviolet-visible (UV-vis), UV-vis with near infrared and Raman spectroscopy, X-ray diffraction, scanning and transmission electron microscopy and conductivity measurements were used to characterize the functionalized SWCNT materials, dispersions and composites. The PANI composite prepared from air oxidized SWCNTs showed the best electrical conductivity indicating a better interaction with polyaniline than ODA functionalised SWCNTs. The improvement of conductivity is attributed to the doping effect or charge transfer of quinoide rings from PANI to SWCNTs.     

Single Walled Carbon Nanotubes Exhibit Dual-Phase Regulation to Exposed Arabidopsis Mesophyll Cells

Herein we are the first to report that single-walled carbon nanotubes (SWCNTs) exhibit dual-phase regulation to Arabidopsis mesophyll cells exposed to different concentration of SWCNTs. The mesophyll protoplasts were prepared by enzyme digestion, and incubated with 15, 25, 50, 100 μg/ml SWCNTs for 48 h, and then were observed by optical microscopy and transmission electron microscopy, the reactive oxygen species (ROS) generation was measured. Partial protoplasts were stained with propidium iodide and 4'-6- diamidino-2-phenylindole, partial protoplasts were incubated with fluorescein isothiocyanate-labeled SWCNTs, and observed by fluorescence microscopy. Results showed that SWCNTs could traverse both the plant cell wall and cell membrane, with less than or equal to 50 μg/ml in the culture medium, SWCNTs stimulated plant cells to grow out trichome clusters on their surface, with more than 50 μg/ml SWCNTs in the culture medium, SWCNTs exhibited obvious toxic effects to the protoplasts such as increasing generation of ROS, inducing changes of protoplast morphology, changing green leaves into yellow, and inducing protoplast cells' necrosis and apoptosis. In conclusion, single walled carbon nanotubes can get through Arabidopsis mesophyll cell wall and membrane, and exhibit dose-dependent dual-phase regulation to Arabidopsis mesophyll protoplasts such as low dose stimulating cell growth, and high dose inducing cells' ROS generation, necrosis or apoptosis.     

Side-chain polyesters derived from adipoyl chloride and α-(bis(2-hydroxyethyl)amino)-ω-(4'- methoxybiphenyl-4-oxy) alkanes

Summary A series of polyesters derived from adipoyl chloride and α-(bis(2-hydroxy ethyl)amino)-ω-(4'-methoxybiphenyl-4-oxy)alkanes with different spacer lengths (Cn-diol, n=6,8,10) have been synthesized and characterized by NMR spectroscopy, SEC, DSC, and X-ray spectroscopy. All polyesters have a narrow distribution of molar masses (1.3–1.5), melting temperature of 55–62°C, and they melt in a narrow temperature range of 7–11°C. Although no liquid crystalline phase transitions were found, an ordered structure was observed by XRD experiments and was ascribed to a crystal smectic phase. Received: 7 June 2001/ Revised version: 1 September 2001/ Accepted: 26 September 2001     

Modulation of Cyclins,p53 and Mitogen-Activated Protein Kinases Signaling in Breast Cancer Cell Lines by 4-(3,4,5-Trimethoxyphenoxy)benzoic Acid

Despite the advances in cancer therapy and early detection, breast cancer remains a leading cause of cancer-related deaths among females worldwide. The aim of the current study was to investigate the antitumor activity of a novel compound, 4-(3,4,5-trimethoxyphenoxy)benzoic acid (TMPBA) and its mechanism of action, in breast cancer. Results indicated the relatively high sensitivity of human breast cancer cell-7 and MDA-468 cells towards TMPBA with IC₅₀ values of 5.9 and 7.9 μM, respectively compared to hepatocarcinoma cell line Huh-7, hepatocarcinoma cell line HepG2, and cervical cancer cell line Hela cells. Mechanistically, TMPBA induced apoptotic cell death in MCF-7 cells as indicated by 4′,6-diamidino-2-phenylindole (DAPI) nuclear staining, cell cycle analysis and the activation of caspase-3. Western blot analysis revealed the ability of TMPBA to target pathways mediated by mitogen-activated protein (MAP) kinases, 5′ adenosine monophosphate-activated protein kinase (AMPK), and p53, of which the concerted action underlined its antitumor efficacy. In addition, TMPBA induced alteration of cyclin proteins’ expression and consequently modulated the cell cycle. Taken together, the current study underscores evidence that TMPBA induces apoptosis in breast cancer cells via the modulation of cyclins and p53 expression as well as the modulation of AMPK and mitogen-activated protein kinases (MAPK) signaling. These findings support TMPBA’s clinical promise as a potential candidate for breast cancer therapy.     

A simple and highly effective process for the purification of single-walled carbon nanotubes synthesized with arc-discharge

We developed a simple and highly effective process for the purification of single-walled carbon nanotubes (SWCNTs) synthesized with arc-discharge. The new process consists of two steps: (i) ultrasonic filtration of an aqueous acid solution of the SWCNTs, and (ii) heat-treatment at 430 °C for 1 h under a moisture-saturated N₂ atmosphere. This simple process results in the remarkably effective removal of impurities such as amorphous carbon, carbon nanoparticles, and metallic catalysts. Further, the whole purification process can be completed within 5 h, which is much faster than conventional acid purification processes, which require 50 h, and much less destructive than other conventional purification methods. In a gram-scale purification, the proposed purification method gave us 150 mg of purified SWCNTs with the purity of 96.2 wt% out of 1.0 g of as-prepared SWCNTs, which corresponds to ∼72% yield as for the initial composition of SWCNTs in the as-prepared soot. Field emission scanning electron microscopy, high resolution transmission electron microscopy, thermogravimetric analysis, X-ray diffractometry, and Raman spectroscopy were used to determine the effects of the new purification process on the SWCNTs.     

FTIR and Raman Spectroscopy of Carbon Nanoparticles in SiO2, ZnO and NiO Matrices

Coatings of carbon nanoparticles dispersed in SiO₂, ZnO and NiO matrices on aluminium substrates have been fabricated by a sol–gel technique. Spectrophotometry was used to determine the solar absorptance and the thermal emittance of the composite coatings with a view to apply these as selective solar absorber surfaces in solar thermal collectors. Cross-sectional high resolution transmission electron microscopy (X-HRTEM) was used to study the fine structure of the samples. Raman spectroscopy was used to estimate the grain size and crystallite size of the carbon clusters of the composite coatings. X-HRTEM studies revealed a nanometric grain size for all types of samples. The C–SiO₂, C–ZnO and C–NiO coatings contained amorphous carbon nanoparticles embedded in nanocrystalline SiO₂, ZnO and NiO matrices, respectively. Selected area electron diffraction (SAED) showed that a small amount of Ni grains of 30 nm diameter also existed in the NiO matrix. The thermal emittances of the samples were 10% for C–SiO₂, 6% for the C–ZnO and 4% for the C–NiO samples. The solar absorptances were 95%, 71% and 84% for the C–SiO₂, C–ZnO and C–NiO samples, respectively. Based on these results, C–NiO samples proved to have the best solar selectivity behaviour followed by the C–ZnO, and last were the C–SiO₂ samples. Raman spectroscopy studies revealed that both the C–ZnO and C–NiO samples have grain sizes for the carbon clusters in the range 55–62 nm and a crystallite size of 6 nm.     

Synthesis of poly-p-phenylenebenzobisthiazole used for fabrication of a thermostable, high-modulus fibre

A method was developed for synthesis of poly-p-phenylenebenzobisthiazole (PPBT) from 2,5-diamino-1,4-dimercaptobenzene diphosphate (DADMB) and terephthalic acid (TPA) in a solution of polyphosphoric acid (PPA) with a 12–15 wt. % concentration of PPBT with a molecular weight of 34,000–38,600 ([η] = 24.5–28.8 dl/g). It was shown that a high concentration of P₂O₅ in PPA, which should be 85.5–86.5 wt. % at the end of the reaction, is one of the basic conditions for obtaining a high-molecular-weight polymer from DADMB diphosphate and TPA. The synthesized liquid-crystalline polymers with a high molecular weight and concentration of 14–15 wt. % in PPA solution were used in the form of polycondensation solutions for spinning high-modulus PPBT fibres. Translated fromKhimicheskie Volokna, No. 6, pp. 35–39, November–December, 1998. We would like to thank L. P. Mil'kova for participating in the x-ray diffraction studies and discussing the results.     

Biodegradation of Single-Walled Carbon Nanotubes in Macrophages through Respiratory Burst Modulation

The biodegradation of carbon nanotubes (CNTs) may be one of major determinants of the toxic outcomes in exposed individuals. In this study, we employed a macrophage/monocyte model, Raw264.7, to investigate the feasibility of regulating the biodegradation of three types of single-walled carbon nanotubes (SWCNTs) (pristine, ox-, and OH-SWCNTs) by respiratory burst modulation. An artificial fluid mimicking the enzymatic reactions of respiratory burst was constituted to reveal the role of respiratory burst played in SWCNT biodegradation. The biodegradation of SWCNTs were characterized by Raman, ultraviolet-visible-near-infrared spectroscopy, and transmission electron microscopy. Our results showed significantly accelerated biodegradation of ox-SWCNTs and OH-SWCNTs in macrophages activated by phorbol myristate acetate (PMA), which could be prevented by N-acetyl-l-cysteine (NAC), whereas p-SWCNTs were resistant to biodegradation. Similar tendencies were observed by using the in vitro enzymatic system, and the degradation rates of these SWCNTs are in the order of OH-SWCNTs > ox-SWCNTs >> p-SWCNTs, suggesting a pivotal role of respiratory burst in accelerating the biodegradation of SWCNTs and that defect sites on SWCNTs might be a prerequisite for the biodegradation to occur. Our findings might provide invaluable clues on the development of intervention measurements for relieving the side effects of SWCNTs and would help to design safer SWCNT products with higher biodegradability and less toxicity.     

A facile route for the preparation of novel optically active poly(amide–imide)/functionalized zinc oxide nanocomposites containing pyromellitoyl-bis-l-phenylalanine moieties

In the present investigation, at first, the surface of zinc oxide (ZnO) nanoparticles was treated with a silane coupling agent of γ-methacryloxypropyltrimethoxy silane (KH570), which introduces organic functional groups on the surface of ZnO nanoparticles. Secondly, optically active poly(amide–imide) (PAI) was synthesized via solution polycondensation of N,N′-(pyromellitoyl)-bis-phenylalanine diacid chloride 1 (M-1) with 4,4′-diaminodiphenylsulfone 2 (M-2). The polycondensation of diacid chloride with aromatic diamine was carried out with N,N-dimethylacetamide/triethylamine systems. Finally PAI/ZnO nanocomposites (NCs) containing 4, 8, and 12% of nanoparticles were successfully fabricated through ultrasonic irradiation technique. The obtained NCs were characterized by Fourier transform-infrared (FT-IR) spectroscopy, thermogravimetry analysis, X-ray powder diffraction, UV–Vis spectroscopy, scanning electron microscopy (SEM), field emission-scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The FT-IR spectroscopy indicated that the silane coupling agent was anchored on the surface of ZnO nanoparticles. SEM, FE-SEM, and TEM images were showed ZnO nanoparticles were dispersed homogeneously in PAI matrix.     

Controllable synthesis of single- and double-walled carbon nanotubes from petroleum coke and their application to solar cells

Single- and double-walled carbon nanotubes (SWCNTs and DWCNTs) have been controllably synthesized by an arc discharge in different atmosphere using petroleum coke as carbon source. The morphology and properties of two kinds of carbon nanotubes (CNTs) synthesized with Fe as catalyst were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, UV–visible spectroscopy, inductively coupled plasma optical emission spectrometer, thermogravimetric analysis and infrared spectroscopy. In the He gas atmosphere only SWCNTs were found to be synthesized by arc discharge in contrast to the case in Ar gas atmosphere in which only DWCNTs were formed, In addition, properties of solar cells based on both kinds of CNTs and n-type Si are examined under illumination of light emission diode (LED). It is found that the performance of solar cells depends significantly on the type of CNTs, i.e., SWCNTs-based solar cells show better performance under LED illumination with wavelengths in the range of 400–940 nm than the case of DWCNTs which exhibit high performance under illumination of the 1310 nm infrared light.     

Parametric study of atmospheric-pressure single-walled carbon nanotubes growth by ferrocene–ethanol mist CVD

Uniform web-like films consisting single-walled carbon nanotubes (SWCNTs) were deposited on a silicon substrate using the chemical vapor deposition (CVD) of ferrocene–ethanol mist at atmospheric pressure (∼ 1 atm). The tiny mist was generated using a high-frequency ultrasonic vibration. The effects of various parameters including deposition position in the reactor, temperature, ferrocene/ethanol ratio, flow rate of carrier gas (argon), and deposition time on the formation of SWCNTs was investigated using high-resolution scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. The worm region outside the furnace was found to be a suitable position for the formation of SWCNT films. The furnace temperature and the flow rate of carrier gas were found to determine the diameter and crystallinity of nanotube. The ferrocene concentration in ethanol strongly influenced the amount of impurity particles in the material. Moreover, the intensity of metallic tail in D-band was found to decrease with increasing the flow rate, showing a possibility of the formation of semiconducting SWCNTs. Results of this study can be used to improve understanding of the growth of SWCNTs by floating catalyst CVD of alcohol mist.