Covalent functionalization of single-walled carbon nanotubes with anthracene by green chemical approach and their temperature dependent magnetic and electrical conductivity studies

Single-walled carbon nanotubes (SWCNTs) were covalently functionalized with anthracene in molten urea by a green chemical approach. The anthracene functionalized single-walled carbon nanotubes (Ant-f-SWCNTs) were examined along with SWCNTs, using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, powder X-Ray diffraction (XRD), and scanning, and transmission electron microscopy. The observations revealed the functionalization of SWCNTs by anthracene. The temperature dependent magnetization (300–5 K) and electrical resistivity were also measured for both SWCNTs and Ant-f-SWCNTs. The electrical resistivity of Ant-f-SWCNTs at 300 K was found to be 1.27 KΩm, which is much lower than 388.55 KΩm for pristine. This indicated a 300 fold increase in conductivity at room temperature for Ant-f-SWCNTs when compared to SWCNTs. The temperature dependence of the conductivity provided an indication of the semiconducting behaviour.     

Single-molecule detection using surface-enhanced resonance Raman scattering and Langmuir-Blodgett monolayers

The Langmuir-Blodgett (LB) technique has been used to obtain spatially resolved surface-enhanced resonance Raman scattering (SERRS) spectra of single dye molecules dispersed in the matrix of a fatty acid. The experimental results presented here mimic the original electrochemical surface-enhanced Raman scattering (SERS) work where the background bulk water did not interfere with the detection of the SERS signal of molecules adsorbed onto the rough silver electrode. LB monolayers of the dye in fatty acid have been fabricated on silver island films with a concentration, in average, of one probe molecule per micrometer square. The properties of single-molecule spectroscopy were investigated using micro-Raman including mapping and global images. Blinking of the SERRS signal was also observed.     

Decoration of single-walled carbon nanotubes with Pt nanoparticles from an organometallic precursor

Carbon nanotubes (CNTs) are nanomaterials of high interest due to their unique structural, electrical, and mechanical properties. Carbon materials have been widely employed to support metallic nanoparticles for catalysis and electrochemical applications. In this work, we investigated the synthesis of platinum nanoparticles generated from the complex Pt₂(dba)₃ (tris(dibenzylideneacetone) diplatinum) and stabilized with a long alkyl chain amine, hexadecylamine (HDA) and supported on functionalized single-walled carbon nanotubes (SWCNTs). High resolution transmission electron microscopy (HRTEM) studies revealed isolated Pt nanoparticles (2?C3 nm) on SWCNTs. Powder X-ray diffraction (XRD) was used to assess the structure of Pt nanoparticles dispersed on SWCNTs assigned to Pt face-centered cubic (fcc). Additionally, infrared Fourier transform spectroscopy confirmed the presence of the stabilizer at the surface of the Pt nanoparticles even after the purification step and functional groups at the surface of pre-treated SWCNTs. This synthetic method may be an alternative route to prepare small size Pt nanoparticles supported on functionalized SWCNTs.     

Combined electron microscopy and spectroscopy characterization of as-received,acid purified,and oxidized HiPCO single-wall carbon nanotubes

Single-wall carbon nanotubes (SWCNTs) are very important materials due to their combination of unique structure, dimension, strength, chemical stability, and electronic properties. Nevertheless, SWCNTs from commercial sources usually contain several impurities, which are usually removed by a purification process that includes reflux in acids and strong oxidation. This strong chemical procedure may alter the nanotube properties and it is thus important to control the extent of functionalization and oxidation during the purification procedure. In this report, we provide a comprehensive study of the structure and physical composition of SWCNTs during each step of the purification process. Techniques such as Raman spectroscopy, transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and Infrared spectroscopy were used to track the SWCNTs structure, in terms of length and diameter distribution, and surface chemical modifications during each purification stage.     

单壁碳纳米管的光解法功能化及其对分散性能的影响(英文)

将单壁碳纳米管分散到溶有光引发剂2-羟基-2-甲基-1-苯基-1-丙醇的四氢呋喃溶液中,在紫外光辐照下,光引发剂裂解生成2-羟基异丙基自由基。通过自由基的偶合反应,2-羟基异丙基自由基偶合到碳纳米管表面。用UV-Vis光谱、FTIR、拉曼光谱、TGA-MS及HRTEM等表征方法,证实在单壁碳纳米管表面引入了羟基。UV-Vis光谱上范霍夫吸收峰的消失表明碳纳米管表面被功能化。羟基化的SWCNTs样品在FTIR光谱中出现的3420cm-1(O—H键)、2930和2859cm-1(烷基C—H键)峰进一步证实了碳纳米管的功能化。拉曼光谱显示,随着SWCNTs的功能化,其切向模式吸收带与杂碳原子吸收带的相对比值(IG/ID)下降。TGA-MS的m/z59峰(400℃)揭示了SWCNTs上存在着异丙醇基团。HRTEM和溶解数据表明,光解改性有助于碳纳米管管束间缠结的解开,进而提高了其在有机溶剂中的溶解性,并且在一定程度上保持了碳纳米管的结构。     

Functionalization of single-walled carbon nanotubes by citric acid/oxygen plasma treatment

A safe and simple method of functionalizing single-walled carbon nanotubes (SWCNTs) has been developed, that significantly increases their dispersibility in water. SWCNTs in pure ethanol are treated with a supersonic homogenizer and dried. Then they are wetted with weak citric acid solution. Finally an RF (13.56 MHz) citric acid/oxygen plasma reaction is carried out under optimum conditions. As a result, hydrophilic functional groups attach onto the SWCNT surfaces, which enhance their dispersibility in water. The attachment of functional groups is identified by the FT-IR spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis. The dispersibility and dispersion stability are studied by the precipitation tests, UV-visible spectroscopy, and transmission electron microscopy. These functionalized SWCNTs are expected to be used in various applications.     

功能石墨烯改性水性聚氨酯及其性能

以氧化石墨烯(GO)为原料,通过聚乙烯亚胺(PEI)接枝改性和水合肼还原,制备出了功能化石墨烯(FG-PEI),并将其与水性UV固化聚氨酯(WPU)乳液复合,制备FG-PEI/WPU复合涂层。采用FTIR、XRD、Raman、XPS、SEM、TEM等测试分析表征FG-PEI的结构,测定了FG-PEI的导电性,并考察了FG-PEI在水中的分散性,研究FG-PEI用量对WPU胶膜的力学性能和导电性能的影响及其热稳定性。结果表明,FG-PEI在保持较好水溶性的条件下,其电导率并未明显下降,并随着FG-PEI在WPU基体中用量的增加,WPU胶膜的表面电阻率逐渐降低,拉伸强度不断增加,断裂伸长率降低,经FG-PEI改性后,WPU的热稳定性得到提高。研究表明,FG-PEI改性WPU可提高胶膜的导电性,使其兼具良好的综合性能。     

A simple and rapid method to graft hydroxyapatite on carbon nanotubes

Herein a simple and effective approach is introduced to functionalize single walled carbon nanotubes (SWCNTs) by in-situ grafting of hydroxyapatite (HA). The pristine SWCNTs were chemically activated through introduction of carboxylic groups on their surfaces by refluxing in the mixture of H(2)SO(4) and HNO(3). The resulting carboxylated SWCNTs were further utilized for grafting of HA. The Fourier transform infrared and Raman spectroscopic studies demonstrated the formation of HA and its grafting over SWCNTs. The phase composition of HA and existence Ca(2+) and PO(4) (3-) ions were studied using X-ray diffraction and energy dispersive X-ray analyses, respectively. The surface morphology of functionalized SWCNTs was analyzed using scanning electron microscopy and transmission electron microscopy. Thermogravimetric analysis confirmed the existence of HA on SWCNTs by exhibiting different thermogram for pure HA and functionalized SWCNTs. Overall this method produced uniform grafting of low crystalline HA on carboxylated SWCNTs with strong interfacial bonding.     

可降解碳纳米管/聚乳酸复合材料的制备及性能

利用丙交酯的开环聚合反应成功地制备了单壁碳纳米管/聚乳酸复合材料, 研究了其降解性和热稳定性。通过红外光谱(FTIR)、 Raman光谱、 热失重分析(TGA)和扫描电子显微镜(SEM)研究, 证明乙二醇功能化的单壁碳纳米管能够参与丙交酯的开环聚合反应, 并在碳纳米管侧壁成功接枝聚乳酸链, 得到的复合材料在碱性溶液中容易降解。差示热分析(DSC)表明, 功能化单壁碳纳米管/聚乳酸复合材料的玻璃化转变温度与纯聚乳酸相比有所提高。      

Preparation of covalently functionalized graphene using residual oxygen-containing functional groups

When fabricated by thermal exfoliation, graphene can be covalently functionalized more easily by applying a direct ring-opening reaction between the residual epoxide functional groups on the graphene and the amine-bearing molecules. Investigation by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and transmission electron microscopy (TEM) all confirm that these molecules were covalently grafted to the surface of graphene. The resulting dispersion in an organic solvent demonstrated a long-term homogeneous stability of the products. Furthermore, comparison with traditional free radical functionalization shows the extent of the defects characterized by TEM and Raman spectroscopy and reveals that direct functionalization enables graphene to be covalently functionalized on the surface without causing any further damage to the surface structure. Thermogravmetric analysis (TGA) shows that the nondestroyed graphene structure provides greater thermal stability not only for the grafted molecules but also, more importantly, for the graphene itself, compared to the free-radical grafting method.     

One-step functionalization of graphene via Diels--Alder reaction for improvement of dispersibility

Good dispersibility of graphene in a medium or matrix is a critical issue in practical applications. In this work, graphene was functionalized using N-(4-hydroxyl phenyl) maleimide (4-HPM) via the Diels–Alder (DA) reaction by a one-step catalyst-free approach. The optimal reaction condition was found to be 90 °C for 12 h using dimethylformamide (DMF) as the solvent. FTIR, Raman spectroscopy, XPS and EDS proved that 4-HPM moieties were successfully grafted onto the surface of graphene. UV-vis and TGA confirmed that the grafting amount of 4-HPM was 3.75%–3.97% based on the mass of graphene. Functionalized graphene showed excellent dispersion stability when dispersed in common solvents such as ethanol, DMF, water, tetrahydrofuran and p-xylene. Meanwhile, functionalized graphene also exhibited pH sensitivity in aqueous due to the phenolic hydroxyls from the 4-HPM moieties. As a result of good dispersion stability and pH sensitivity, compared with graphene, functionalized graphene had better adsorption capacity for methylene blue (MB) from aqueous solution.     

High-quality single-walled carbon nanotubes synthesis by hot filament CVD on Ru nanoparticle catalyst

We investigated the single-walled carbon nanotubes (SWCNTs) growth on Ru nanoparticle catalyst via hot filament assisted chemical vapor deposition (HFCVD) with two independent W filaments for the carbon precursor (methane) and the hydrogen dissociation respectively. The Ru nanoparticles were obtained following a two-step strategy. At first the growth substrate is functionalized by silanisation, then a self assembly of a ruthenium porphyrin complex monolayer on pyridine-functionalized metal oxide substrates. We have studied the impact of the filaments power and we optimized the SWCNTs growth temperature. The as grown SWCNTs were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and Raman spectroscopy. It was found that the quality, density and the diameter of SWCNTs depends on the filament and growth temperature. Results of this study can be used to improve the understanding of the growth of SWCNTs by HFCVD.     

Semi-quantitative analysis of gentian violet by surface-enhanced Raman spectroscopy using silver colloids

The viability of the application of surface-enhanced Raman spectroscopy (SERS) to the semi-quantitative analysis of the triphenylmethane dye gentian violet was examined by using activated borohydride-reduced silver colloids. Raman and SERS spectra of aqueous solutions of gentian violet at different pH values were acquired for the first time and equally intense SERS signals were obtained at both acidic and alkaline pH values. Two maxima intensities observed in the pH profile revealed the presence of different ionization states of the dye. The pH conditions for SERS were optimized over the pH range 1 to 12 and the biggest enhancement for SERS of this charged dye was found to be at pH 2.0; thus, this condition was used for semi-quantitative analysis. A good linear correlation was observed for the dependence of the signal intensities of the SERS bands at 1620 cm(-1) (R = 0.999) and 1370 cm(-1) (R = 0.952) on dye concentration over the range 10(-6) to 10(-4) mol/L, using laser excitation at 514.5 nm. At concentrations of dye above 10(-2) mol/L, the concentration dependence of the SERS signals is nonlinear. This is explained as due to the precipitation of metallic silver as well as due to saturation caused by complete coverage of the SERS substrate. A series of intensities of the band at 1620 cm(-1) measured from dye molecules proved that the single-molecule limit of gentian violet is attained at the concentration of 10(-9) mol/L.     

Surface-Enhanced Raman Scattering Detection of pH with Silica-Encapsulated 4-Mercaptobenzoic Acid-Functionalized Silver Nanoparticles

Sensors based upon surface-enhanced Raman spectroscopy (SERS) are attractive because they have narrow, vibrationally specific spectral peaks that can be excited using red and near-infrared light which avoids photobleaching, penetrates tissue, and reduces autofluorescence. Several groups have fabricated pH nanosensors by functionalizing silver or gold nanoparticle surfaces with an acidic molecule and measuring the ratio of protonated to deprotonated Raman bands. However, a limitation of these sensors is that macromolecules in biological systems can adsorb onto the nanoparticle surface and interfere with measurements. To overcome this interference, we encapsulated pH SERS sensors in a 30 nm thick silica layer with small pores which prevented bovine serum albumin (BSA) molecules from interacting with the pH-indicating 4-mercaptobenzoic acid (4-MBA) on the silver surfaces but preserved the pH-sensitivity. Encapsulation also improved colloidal stability and sensor reliability. The noise level corresponded to less than 0.1 pH units from pH 3 to 6. The silica-encapsulated functionalized silver nanoparticles (Ag-MBA@SiO(2)) were taken up by J774A.1 macrophage cells and measured a decrease in local pH during endocytosis. This strategy could be extended for detecting other small molecules in situ.     

The synthesis and fluorescence quenching properties of well soluble hybrid graphene material covalently functionalized with indolizine

Chemically functionalized graphene-indolizine functionalized graphene (IMG) sheets, which can be well dispersed in different organic solvents over four months without obvious aggregation, are obtained through a 1,3-dipolar cycloaddition to graphene with pyridinium ylide. The properties of IMG sheets are investigated using a thorough set of measurements including UV-visible spectroscopy, Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy (PL), transmission electron microscopy (TEM), atomic force microscopy (AFM) and cyclic voltammetry (CV), and a tagging technique has exhibited the distribution of functional groups on the graphene surface. The IMG sheets show very strong quenching by a factor of ～ 93.4% to that of indolizine, which is attributed to the fluorescence resonance energy transfer (FRET) from indolizine molecules to few-layer graphene sheets. The CV method also proved the catalytic properties of IMG sheets in some redox systems.     

A surfactant dispersed SWCNT-polystyrene composite characterized for electrical and mechanical properties

Single wall carbon nanotubes (SWCNTs) were dispersed in polystyrene (PS) at 0.1, 0.2, 0.3 and 1.0 wt.% (weight percent) concentrations using a surfactant assisted method. The resulting nanocomposites were characterized for their electrical conductivity, mechanical strength and fracture toughness properties. Results show a significant improvement in electrical conductivity with electrical percolation occurring by 0.2 wt.% SWCNT loading and the SWCNT-PS nanocomposite fully conductive at 1.0 wt.%. Three-point bend tests showed a decline in flexural strength and break strain with the addition of 0.1 wt.% SWCNTs. Improvements in the flexural modulus, strength and break strain with increasing SWCNT wt.% content followed The fracture toughness of the SWCNT-PS nanocomposites, in terms of the critical stress-intensity factor K_IC, was reduced relative to the neat material. From optical and high resolution scanning electron microscopy the presence of the carbon nanotubes is shown to have an adverse effect on the crazing mechanism in this PS material, resulting in a deterioration of the mechanical properties that depend on this mechanism.     

Application of Raman multivariate curve resolution to solvation-shell spectroscopy

Raman spectroscopy and multivariate curve resolution (Raman-MCR) are combined to yield a powerful spectroscopic method for identifying solute-induced perturbations of solvent molecules. The principles and applications of the resulting solvation-shell spectroscopy are described and illustrated using both numerical model spectra and experimental Raman spectra, including water in acetone and aqueous OH(-), as well as of both neutral and ionic acetic acid solutions. The results illustrate the quantitative capabilities of Raman-MCR as a solvation-shell spectroscopy, including fundamental limitations arising from "intensity" and "rotational" ambiguities.     

Tailored SWCNT functionalization optimized for compatibility with epoxy matrices

We have modified single walled carbon nanotubes (SWCNTs) with well defined matrix-based architectures to improve interface interaction in SWCNT/epoxy composites. The hardener and two pre-synthesized oligomers containing epoxy and hardener moieties were covalently attached to the SWCNT walls by in?situ diazonium or carboxylic coupling reactions. In this way, SWCNTs bearing amine or epoxide-terminated fragments of different molecular weights, which resemble the chemical structure of the cured resin, were synthesized. A combination of characterization techniques such as Raman and infrared absorption (FTIR) spectroscopy, elemental analysis and coupled thermogravimetry-FTIR spectroscopy were used to identify both the functional groups and degree of functionalization of SWCNTs synthesized by the laser ablation and arc-discharge methods. Depending on the type of reaction employed for the chemical functionalization and the molecular weight of the attached fragment, it was possible to control the degree of functionalization and the electronic properties of the functionalized SWCNTs. Improved dispersion of SWCNTs in the epoxy matrix was achieved by direct integration without using solvents, as observed from optical microscopy and rheology measurements of the SWCNT/epoxy mixtures. Composite materials using these fillers are expected to exhibit improved properties while preserving the thermosetting architecture.     

Ester-functionalized single-walled carbon nanotubes via addition of haloformates

Herein, a versatile method to introduce ester functional groups to the surface of single-walled carbon nanotubes (SWCNTs) was defined. Ester-modified SWCNTs were prepared via the direct reaction of haloformates with reduced SWCNTs [(nBu–SWCNT ^n? ) Li _n ⁺ ] generated by n-butyl lithium. Ultraviolet–Visible–near infrared and Raman spectroscopy verified the evidence of covalent surface functionalization. Solubility of functionalized SWCNTs (f-SWCNTs) enhanced compared to purified SWCNTs. Gold tagging to positively charged SWCNTs displayed the presence and distribution of functional groups, confirming the conversion of esters into amides. f-SWCNTs were further characterized by thermo-gravimetric analysis coupled with mass spectrometry and fourier-transform infrared spectroscopy.     

Surfactant assisted dispersion of functionalized multi-walled carbon nanotubes in aqueous media

The dispersibility of unfunctionalized and three differently functionalized multi-walled carbon nanotubes (MWNTs) in the presence of anionic, cationic, and non-ionic surfactants was investigated. Significant differences in their dispersibility were revealed by UV–vis spectroscopy of the dispersed MWNTs. X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, streaming potential measurements as well as pH measurements were conducted to characterize the MWNTs and their dispersions. Based on this information, possible interaction mechanisms between the surfactants and the differently functionalized MWNTs are proposed in order to account for the distinct dispersibility observed. Aqueous sizings containing low weight fractions of MWNTs were used for on-line modification of glass fibre (GF) sizings and preparation of GF/polypropylene composites, resulting in enhanced mechanical properties.