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1.
Single‐walled carbon nanotubes (SWCNTs) have been functionalized with poly(γ‐benzyl‐L ‐glutamate) (PBLG) by ring‐opening polymerizations of γ‐benzyl‐L ‐glutamic acid‐based N‐carboxylanhydrides (NCA‐BLG) using amino‐functionalized SWCNTs (SWCNT‐NH2) as initiators. The SWCNT functionalization has been verified by FTIR spectroscopy and transmission electron microscopy. The FTIR study reveals that surface‐attached PBLGs adopt random‐coil conformations in contrast to the physically absorbed or bulk PBLGs, which exhibit α‐helical conformations. Raman spectroscopic analysis reveals a significant alteration of the electronic structure of SWCNTs as a result of PBLG functionalization. The PBLG‐functionalized SWCNTs (SWCNT‐PBLG) exhibit enhanced solubility in DMF. Stable DMF solutions of SWCNT‐PBLG/PBLG with a maximum SWCNTs concentration of 259 mg L?1 can be readily obtained. SWCNT‐PBLG/PBLG solid composites have been characterized by differential scanning calorimetry, thermogravimetric analysis, wide/small‐angle X‐ray scattering (W/SAXS), scanning electron microscopy, and polarized optical microscopy for their thermal or morphological properties. Microfibers containing SWCNT‐PBLG and PBLG can also be prepared via electrospinning. WAXS characterization reveals that SWCNTs are evenly distributed among PBLG rods in solution and in the solid state where PBLGs form a short‐range nematic phase interspersed with amorphous domains. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2340–2350, 2010  相似文献   

2.
The incorporation of single‐wall carbon nanotubes (SWCNTs) in cadmium arachidate film by means of the Langmuir‐Blodgett (LB) technique was investigated as a function of arachidic acid/SWCNT mass ratio at the air/water interface and in Langmuir‐Blodgett films. The behaviour at the air/water interface shows that SWCNTs act as an independent phase with respect to the cadmium arachidate. Deposition conditions are optimized when the weight ratio between the arachidic acid (AA) and SWCNTs is in the range 0.018:1 to 1:1. The general order of the LB multilayered structure was destroyed by the progressive density increase in SWCNT quantity as evidenced by X‐ray reflectivity (XRR) analysis. Scanning electron microscopy images indicated that when a multilayered structure was formed its layers consisted of SWCNT bundles stacked one over the other. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

3.
Elemental phosphorus displays an impressive number of allotropes with highly diverse chemical and physical properties. White phosphorus has now been filled into single‐wall carbon nanotubes (SWCNTs) from the liquid and thereby stabilized against the highly exothermic reaction with atmospheric oxygen. The encapsulated tetraphosphorus molecules were visualized with transmission electron microscopy, but found to convert readily into chain structures inside the SWCNT “nanoreactors”. The energies of the possible chain structures were determined computationally, highlighting a delicate balance between the extent of polymerization and the SWCNT diameter. Experimentally, a single‐stranded zig‐zag chain of phosphorus atoms was observed, which is the lowest energy structure at small confinement diameters. These one‐dimensional chains provide a glimpse into the very first steps of the transformation from white to red phosphorus.  相似文献   

4.
Polyethylene (PE) chains grafted onto the sidewalls of SWCNTs (SWCNT‐g‐PE) were successfully synthesized via ethylene copolymerization with functionalized single‐walled carbon nanotubes (f‐SWCNTs) catalyzed by rac‐(en)(THInd)2ZrCl2/MAO. Here f‐SWCNTs, in which α‐alkene groups were chemically linked on the sidewalls of SWCNTs, were synthesized by Prato reaction. The composition and microstructure of SWCNT‐g‐PE were characterized by means of 1H NMR, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetric analyses (TGA), field‐emission scanning electron microscope (FESEM), and transmission electron microscope (TEM). Nanosized cable‐like structure was formed in the SWCNT‐g‐PE, in which the PE formed a tubular shell and several SWCNTs bundles existed as core. The formation of the above morphology in the SWCNT‐g‐PE resulted from successfully grafting of PE chains onto the surface of SWCNTs via copolymerization. The grown PE chains grafted onto the sidewall of the f‐SWCNTs promoted the exfoliation of the mass nanotubes. Comparing with pure PE, the physical mixture of PE/f‐SWCNTs and in situ PE/SWCNTs mixture, thermal stability, and mechanical properties of SWCNT‐g‐PE were higher because of the chemical bonding between the f‐SWCNTs and PE chains. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5459–5469, 2007  相似文献   

5.
The effect of single walled carbon nanotube (SWCNT) fillers on the low temperature thermal properties and curing behavior of SWCNT‐silicone nanocomposite are reported for the first time. The SWCNT‐silicone composites were prepared by different mixing procedures and characterized by differential scanning calorimetry (DSC). Solution mix, with the aid of sonication and soaking achieved better dispersion of SWCNTs in the silicone. The adding of SWCNTs in polymer seriously hindered the curing of silicone elastomer. The hindrance increased with increasing concentration of SWCNT and the quality of dispersion. The glass transition temperatures (Tg) of the nanocomposites were found to be independent of the SWCNT addition, although, the steps in the heat capacity (Δcp) of the glass transition were smaller with increasing SWCNTs concentration. The melt crystallization behavior was strongly dependent on the concentration and dispersion of SWCNT in the polymer. The cooling scan showed that the higher concentration and the better dispersion of SWCNTs in the silicone resulted in higher percentage of melt crystallization of this nanocomposite. The correlation of the change of thermal properties to the dispersion of CNT in polymer may be used to determine the quality of SWCNT dispersion in silicone polymer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1845–1852, 2008  相似文献   

6.
Ruthenium polypyridyl complexes are widely used as light harvesters in dye‐sensitized solar cells. Since one of the potential applications of single‐wall carbon nanotubes (SWCNTs) and their derived materials is their use as active components in organic and hybrid solar cells, the study of the photochemistry of SWCNTs with tethered ruthenium polypyridyl complexes is important. A water‐soluble ruthenium tris(bipyridyl) complex linked through peptidic bonds to SWCNTs (Ru‐SWCNTs) was prepared by radical addition of thiol‐terminated SWCNT to a terminal C?C double bond of a bipyridyl ligand of the ruthenium tris(bipyridyl) complex. The resulting macromolecular Ru‐SWCNT (≈500 nm, 15.6 % ruthenium complex content) was water‐soluble and was characterized by using TEM, thermogravimetric analysis, chemical analysis, and optical spectroscopy. The emission of Ru‐SWCNT is 1.6 times weaker than that of a mixture of [Ru(bpy)3]2+ and SWCNT of similar concentration. Time‐resolved absorption optical spectroscopy allows the detection of the [Ru(bpy)3]2+‐excited triplet and [Ru(bpy)3]+. The laser flash studies reveal that Ru‐SWCNT exhibits an unprecedented two‐photon process that is enabled by the semiconducting properties of the SWCNT. Thus, the effect of the excitation wavelength and laser power on the transient spectra indicate that upon excitation of two [Ru(bpy)3]2+ complexes of Ru‐SWCNT, a disproportionation process occurs leading to delayed formation of [Ru(bpy)3]+ and the performance of the SWCNT as a semiconductor. This two‐photon delayed [Ru(bpy)3]+ generation is not observed in the photolysis of [Ru(bpy)3]3+; SWCNT acts as an electron wire or electron relay in the disproportionation of two [Ru(bpy)3]2+ triplets in a process that illustrates that the SWCNT plays a key role in the process. We propose a mechanism for this two‐photon disproportionation compatible with i) the need for high laser flux, ii) the long lifetime of the [Ru(bpy)3]2+ triplets, iii) the semiconducting properties of the SWNT, and iv) the energy of the HOMO/LUMO levels involved.  相似文献   

7.
Single‐wall carbon nanotubes (SWCNTs) have been added to high molecular weight poly(γ‐benzyl‐L ‐glutamate), or PBLG, to evaluate their effects on the polymer's shear piezoelectricity. While the addition of SWCNTs increased various PBLG physical properties such as electrical conductivity, dielectric constant, several mechanical properties, and electrostriction coefficient, the shear piezoelectricity remained constant up to a 0.3 wt % SWCNT concentration. The composite crystallinity, orientation, and SWCNT alignment (measured by X‐ray diffraction, birefringence, and polarized Raman spectroscopy, respectively) were found to be constant up to this same concentration, corroborating the shear piezoelectric findings. PBLG composites made with acid‐treated (and therefore less electrically conductive) SWCNTs exhibited similar shear piezoelectric behavior, indicating that neither the SWCNT type, concentration (up to the percolation threshold), nor electrical conductivity influences PBLG shear piezoelectricity. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010  相似文献   

8.
The addition of SH and OH groups to single‐wall carbon nanotubes (SWCNTs) was investigated employing first principles calculations. In the case of the semiconducting (10, 0) SWCNT the SWCNT‐SH binding energy is weak, 2–4 kcal/mol. However, for the metallic (5, 5) SWCNT it is larger, 7–9 kcal/mol. Thus metallic SWCNTs seem to be more reactive to SH than the semiconducting ones. Indeed, the (6, 6) SWCNT is more reactive to SH than the (10, 0) SWCNT, by 2–3 kcal/mol, something that can be explained only considering the electronic structure of the tube, because the (6, 6) has a larger diameter. The binding energies are larger for the addition of the OH group, 25 and 30 kcal/mol for the (10, 0) and (5, 5) SWCNTs, respectively. When a single OH or SH group is attached to the metallic SWCNTs, we observe important changes in the DOS at the Fermi level. However, when multiple SH groups are attached, the changes in the electronic and magnetic properties depend on the position of the SH groups. The small binding energy found for the SH addition indicates that the successful functionalization of SWCNTs with SH, SCH3, and S(CH2)nSH groups is mostly due to the presence of defects created after acid treatment and to a minor extent by the metallic tubes present in the samples. Perfect semiconducting SWCNTs showed very low reactivity against the SH group. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009  相似文献   

9.
Charged peptides and proteins disperse single‐wall carbon nanotubes (SWCNTs) in aqueous solutions. However, little is known about the role of their side chains in their interactions with SWCNTs. Homopolypeptide–SWCNT systems are ideal for investigating the mechanisms of such interactions. In this study, we demonstrate that SWCNTs are individually dispersed by poly‐L ‐arginine (PLA). The debundled SWCNTs exhibited a distinct fluorescence. The dispersibility of SWCNTs with PLA was greater than that of SWCNTs with poly‐L ‐lysine (PLL). Molecular dynamics simulations suggest that the side chains of PLA have stronger interactions with the sidewalls of SWCNTs compared with those of PLL. The guanidinium group at the end of the side chain of an arginine residue plays an important role in the interaction with SWCNTs, likely through hydrophobic, van der Waals, and π–π interactions. PLA can be useful as a tool for the dispersion of SWCNTs and can be used to non‐covalently anchor materials to SWCNTs with strong binding.  相似文献   

10.
Diels–Alder cycloaddition is one of the most powerful tools for the functionalization of single‐walled carbon nanotubes (SWCNTs). Density functional theory at the B3‐LYP level of theory has been used to investigate the reactivity of different‐diameter SWCNTs (4–9,5) in Diels–Alder reactions with 1,3‐butadiene; the reactivity was found to decrease with increasing SWCNT diameter. Distortion/interaction analysis along the whole reaction pathway was found to be a better way to explore the reactivity of this type of reaction. The difference in interaction energy along the reaction pathway is larger than that of the corresponding distortion energy. However, the distortion energy plots for these reactions show the same trend. Therefore, the formation of the transition state can be determined from the interaction energy. A lower interaction energy leads to an earlier transition state, which indicates a lower activation energy. The computational results also indicate that the original distortion of the SWCNTs leads to an increase in the reactivity of the SWCNTs.  相似文献   

11.
Residual metal impurities were exploited as reactants in the functionalization of the surface of single‐walled carbon nanotubes (SWCNT) with nickel hexacyanoferrate (NiHCF) by simple electrochemical cycling in ferricyanide solutions. This facile in situ electrochemical modification process provides intimate contact between NiHCF and SWCNTs that improves the stability of the redox property and reactivity of NiHCF. The characteristic redox behavior of NiHCF on SWCNT surfaces can be used as an electrochemical probe to access qualitative and quantitative information on unknown electroactive metal impurities in SWCNTs. Significantly, the NiHCF‐modified SWCNTs exhibit pseudocapacitive behavior, and the calculated specific capacitances are 710 and 36 F g?1 for NiHCF‐SWCNTs and SWCNTs respectively. Furthermore, NiHCF‐SWCNTs were transformed into Ni(OH)2/SWCNTs and used for enzymeless glucose oxidation.  相似文献   

12.
A non‐covalent double‐decker binding strategy is employed to construct functional supramolecular single‐wall carbon nanotubes (SWCNT)–tetrapyrrole hybrids capable of undergoing photoinduced electron transfer and performing direct conversion of light into electricity. To accomplish this, two semiconducting SWCNTs of different diameters (6,5 and 7,6) were modified via π–π stacking of pyrene functionalized with an alkyl ammonium cation (PyrNH3+). Such modified nanotubes were subsequently assembled via dipole–cation binding of zinc porphyrin with one ( 1 ) or four benzo‐18‐crown‐6 cavities ( 2 ) or phthalocyanine with four benzo‐18‐crown‐6 cavities at the ring periphery ( 3 ), employed as visible‐light photosensitizers. Upon charactering the conjugates using TEM and optical techniques, electron transfer via photoexcited zinc porphyrin and phthalocyanine was investigated using time‐resolved emission and transient absorption techniques. Higher charge‐separation efficiency is established for SWCNT(7,6) with a narrow band gap than the thin SWCNT(6,5) with a wide band gap. Photoelectrochemical studies using FTO/SnO2 electrodes modified with these donor–acceptor conjugates unanimously demonstrated the ability of these conjugates to convert light energy into electricity. The photocurrent generation followed the trend observed for charge separation, that is, incident‐photon‐to‐current efficiency (IPCE) of a maximum of 12 % is achieved for photocells with FTO/SnO2/SWCNT(7,6)/PyrNH3+: 1 .  相似文献   

13.
Single‐walled carbon nanotubes (SWCNTs) have been functionalized with poly(γ‐benzyl‐L ‐glutamate)s (PBLGs) having well‐defined polymer molecular weight (Mn = 7.5–21.1 kg·mol?1) and molecular weight distribution (PDI = 1.05–1.20) by a graft‐to method. Toluene solutions containing 5 wt % free PBLG and variable amounts of PBLG‐functionalized SWCNTs (PBLG‐SWCNTs) form gels at room temperature. Differential scanning calorimetry (DSC) analysis reveals that the gelation occurs thermoreversibly, in accord with previous studies on the pristine PBLG/toluene gels. The heat of gel melting (ΔHm) is slightly elevated for the composite gels compared with the pristine gel, which suggests enhanced interactions between PBLGs in the former. But the gelation temperatures of the composites are unaffected by the presence of PBLG‐SWCNTs. Small‐angle X‐ray scattering (SAXS) analysis of the composite and pristine gels at different temperatures by the Guinier method suggests that PBLG‐SWCNTs promote interactions between PBLG rods, as indicated by the larger PBLG bundle size with increasing PBLG‐SWCNT content in the gel and the melt state. W/SAXS analysis of the dry gels reveals that PBLG‐SWCNTs induce significant changes in the PBLG packing order, resulting in a nematic phase, in contrast to a weakly ordered smectic C phase containing tilted PBLG rods that is observed in the pristine gel. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011  相似文献   

14.
Theoretical investigation on local electronic structure and stability of the π–π stacking interaction of pyrazinamide (PZA) with armchair (5,5) and zigzag (9,0) single‐walled carbon nanotubes (SWCNTs) is performed using density functional theory (DFT). PZA is physisorbed onto nanotube sidewall through interaction of π orbitals of PZA and SWCNT and the enhanced structural stability of PZA/SWCNT systems is due to weak side‐on rather than the head‐on π‐interactions. The physisorption of PZA onto SWCNT sidewall is thermodynamically favored; as a consequence, it modulates the electronic properties of pristine nanotube in the vicinity of Fermi region and π–π stacked interactions is stronger in (9,0) SWCNT compared to (5,5) SWCNT. The density of states (DOS) analysis show that PZA contributes toward the enhancement of electronic states. Projected DOS and frontier orbital analysis in the vicinity of Fermi level region suggest the electronic states to be contributed from SWCNT rather than PZA. In addition, hybrid DFT calculation which includes the dispersion correction is employed to explain the non‐covalent π–π stacking interaction between PZA and SWCNT. The local density approximation and GGA results are compared with DFT‐D to explain near about accurately the weak nonbonded van der Waals interactions between PZA and SWCNTs. © 2012 Wiley Periodicals, Inc.  相似文献   

15.
A homopolymer iPP and a series of propylene‐ethylene random copolymers with a content of ethylene from 7 to 21 mol % were used as matrices to prepare single‐walled carbon nanotube (SWCNT) nanocomposites in a range of SWCNT concentration from 0.15 to 1 wt %. The solution blending and melt‐ compression molding procedures were kept identical for all nanocomposites. The poly(propylenes) have crystallinities ranging from 70 to 10%, and serve to test the role of SWCNTs acting as nucleants to preserve in the nanocomposites the uniform dispersion of SWCNTs after sonication. The major role of polymer crystallinity is to mediate toward a more open and more connected SWCNT network structure. Fast nucleation and growth of high crystalline matrices on multiple sites along the surface of the nanotubes prevents SWCNT clustering, and entraps the SWCNT network between the semicrystalline structure reducing the driving force of nanotubes to curl and twist. Depletion of crystallites in the less crystalline matrices (<35% crystallinity) leads to curled and poorly connected nanotubes. A consequence of the gradual loss of SWCNT connectivity is a decreased electrical conductivity; however, the change with crystallinity is not linear. Conductivity decreases sharply with decreasing crystallinity for SWCNT contents near the percolation region, while for contents approaching the plateau region the electrical conductivity is less sensitive to matrix crystallinity. The percolation threshold decreases rapidly for polymers with <~30% crystallinity and slowly levels off at crystallinities >~40%. At SWCNT concentrations of 0.15 wt %, SEM images of nanocomposites with the highest crystallinity matrix indicate debundled and interconnected nanotubes, whereas more disconnected and curled SWCNTs remain in the lowest crystallinity nanocomposites. Electrical conductivity in the former is relatively high, whereas the latter are insulators. Also discussed is the nucleating effect of nanotubes and restrictions of the filler to polymer chain diffusion in the crystallization of the polymers. SEM images and Raman spectra in the radial breathing modes region (100–400 cm?1) are complementary tools to extract the quality and details of the SWCNT dispersion in the nanocomposites. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2084–2096, 2010  相似文献   

16.
A supramolecular hybrid is prepared by the supramolecular surface modification of single‐walled carbon nanotube (SWCNT) with cationic β‐cyclodextrin‐tethered ruthenium complexes through a spacer molecule that contains both an adamantane and a pyrene moiety. By employing the supramolecular hybrid, spatially controllable DNA condensation along the SWCNT skeleton is achieved by anchoring cationic ruthenium complexes on the surface. Furthermore, because of the unique physiological properties of SWCNTs, the cationic supramolecular hybrid can be used as a nonviral gene delivery system with the ruthenium complexes as a fluorescent probe to monitor uptake of DNA by cells.  相似文献   

17.
Herein, we have developed a synthetic strategy for the covalent double functionalization of single‐walled carbon nanotubes (SWCNTs) with a combination of purine–pyrimidine and purine–purine nucleobase systems. The nucleobases were introduced on the sidewall of oxidized SWCNTs through 1,3‐dipolar cycloaddition and by amidation of the carboxylic acids located at the tips and defect sites of the nanotubes. The new nanohybrids were characterized by transmission electron microscopy, thermogravimetric analysis, FTIR and Raman spectroscopy, magic‐angle spinning NMR spectroscopy, and Kaiser test. The nucleobase/SWCNT conjugates can be envisaged for the modulation of the interactions with nucleic acids by means of base pairing, thereby opening new possibilities in the development of DNA/CNT nanobioconjugates.  相似文献   

18.
The interaction of single‐walled carbon nanotubes (SWCNTs) and α‐sexithiophene (6T) was studied by Raman spectroscopy and by in situ Raman spectroelectrochemistry. The encapsulation of 6T in SWCNT and its interaction causes a bleaching of its photoluminescence, and also small shifts of its Raman bands. The Raman features of the SWCNT with embedded 6T (6T‐peapods) change in both intensity and frequency compared to those of pristine SWCNT, which is a consequence of a change of the resonant condition. Electrochemical doping demonstrated that the electrode potential applied to the SWCNT wall causes changes in the embedded 6T. The effects of electrochemical charging on the Raman features of pristine SWCNT and 6T@SWCNT were compared. It is shown that the interaction of SWCNT with 6T also changes the electronic structure of SWCNT in its charged state. This change of electronic structure is demonstrated both for semiconducting and metallic tubes.  相似文献   

19.
A novel approach to solubilize single‐walled carbon nanotubes (SWCNTs) in the aqueous phase is described by employing supramolecular surface modification. We use cyclodextrin complexes of synthetic molecules that contain a planar pyrene moiety or a bent, shape‐fitted triptycene moiety as a binding group connected through a spacer to an adamantane moiety that is accommodated in the cyclodextrin cavity. The binding groups attach to the sidewalls of SWCNTs through a π–π stacking interaction to yield a supramolecular system that allows the SWCNTs to dissolve in the aqueous phase through the formed hydrophilic cyclodextrin shell. The black aqueous SWCNT solutions obtained are stable over a period of months. They are characterized through absorbance, static, and time‐resolved fluorescence spectroscopy as well as Raman spectroscopy, TEM, and fluorescence‐decay measurements. Furthermore, the shape‐fitted triptycene‐based system shows a pronounced selectivity for SWCNTs with a diameter of 1.0 nm.  相似文献   

20.
Arrays of polymer/SWCNT (single‐wall carbon nanotube) nanowires supported on a residual nanocomposite film are prepared by melt wetting using porous anodic aluminum oxide (AAO) as a template. The aggregation parameter of SWCNTs extracted from the analysis of their Raman radial breathing modes gives the highest value for native SWCNTs, indicating that they tend to organize into bundles giving rise to a high degree of aggregation. However, the lowest value achieved at the interface between the nanocomposite film and the nanoarray is explained considering that the forces acting during infiltration are able to disrupt the SWCNT bundles inducing nanotube dispersion. In addition, scanning the nanoarrays along the nanowires length by Raman microscopy has shown a diameter selection of SWCNTs by the AAO membrane. The results reported in this work reveal that it is possible to fabricate arrays of nanowires with homogeneous SWCNT distribution along tens of microns, optimizing nanotube dispersion.  相似文献   

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