Surface functionalization of single-walled carbon nanombes using metal nanoparticles

Surface functionalization of suspended single-walled carbon nanotubes (SWNTs) using metal (Au) nanoparticles (NPs) is reported. SWNTs are grown on three-dimensionally patterned substrates by thermal chemical vapor deposition and successfully functionalized with Au NPs. Ethylendiamine is mainly used to functionalize SWNTs surface with amino groups before introducing Au NPs. From Raman scattering spectroscopy of the Au-functionalized suspended SWNTs, enhanced Raman scattering properties are obtained. The results suggest that the attached Au NPs may contribute to the enhancement of resonant phenomena. By measuring the electric properties after each functionalization process, it is found that Au NPs act as electron acceptor to the amine functionalized SWNTs.     

Effect of Curing and Functionalization on the Interface Thermal Conductance in Carbon Nanotube–Epoxy Composites

This study investigates the interface thermal conductance in a functionalized carbon nanotube (CNT)–epoxy composite system and how it is modified when the surrounding matrix is cured. We have used nonequilibrium molecular dynamics simulations to study the interface thermal conductance in both cured and uncured matrices, based on diglycidyl ether of bisphenol F (EPON-862) and diethylenetoluenediamine. The functionalization is modeled using a dynamic crosslinking algorithm and represents a realistic model of the matrix-filler interface. The thermal interface conductance increases linearly with the degree of functionalization up to the studied 2.5% due to stronger thermal coupling between functionalized CNT and the matrix. In addition, it was observed that curing of the matrix increases the interface conductance by 20% relative to the uncured matrix. This increase is attributed to an increase in thermal conductivity of cured epoxy resulting from relative enhancement in nonbonded interactions (originating from volume reduction) and structural rigidity during curing. Our results suggest that the interface conductance can be strongly influenced by the thermal properties of the bulk matrix as well as the interface chemistry of the additives such as CNTs.     

模板法制备纳米MnO2/CNT复合材料及其在锂电池中的应用

以P123为表面活性剂,采用软模板法合成MnO2/CNT纳米复合材料。采用X射线衍射、热重和差热分析、傅立叶变换红外光谱分析和高分辨率透射电子显微镜对样品进行表征。结果表明,样品为弱结晶的α-MnO2,直径约10nm,长30？50nm,它们附着在碳纳米管壁上。样品的电化学性能通过组成Li-MnO2进行电池充放电和电化学阻抗测试（EIS）,与纯二氧化锰相比,MnO2/CNT纳米复合材料具有更大的初始容量275.3mA·h/g和更好的倍率和循环性能。     

CNT/PEDOT core/shell nanostructures as a counter electrode for dye-sensitized solar cells

CNT/PEDOT nanostructures composed of carbon nanotube (CNT) cores and poly(3,4-ethylenedioxythiophene) (PEDOT) shells were synthesized by chemical oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) using FeCl₃ and dodecylbenzene sulfonic acid (DBSA) as the oxidant and surfactant, respectively. The resulting CNT/PEDOT nanostructures had a PEDOT layer thickness of 2–5 nm that exhibited not only higher polymerization yield but also enhanced thermal stability and electrical conductivity relative to pure PEDOT. N-Methyl-2-pyrrolidone (NMP)-based CNT/PEDOT paste containing polyvinylidene fluoride (PVDF) as a binder was painted directly onto fluorine-doped tin oxide (FTO) glass for use as a counter electrode (CE) material in dye-sensitized solar cells (DSSCs). While DSSCs made of pure CNT and PEDOT CE exhibited power conversion efficiencies of ～3.88% and 4.32% under standard AM 1.5 sunlight illumination, respectively, the cell efficiency was enhanced to ～4.62% with the CNT/PEDOT CE. This enhancement was due to the improved fill factor of the CNT/PEDOT-based DSSC realized by the increased electrical conductivity of the CNT/PEDOT composite.     

Surface functionalization of multi-walled carbon nanotubes via electron reduction of benzophenone by potassium metal

The covalent sidewall functionalization of multi-walled carbon nanotubes (MWCNTs) via the electron reduction of benzophenone by potassium metal is reported. Fourier transform infrared spectroscopy (FTIR) results show that diphenylcarbinol (DPC) groups were successfully grafted to the MWCNTs sidewalls after 10 days of reaction time. Raman and UV–vis spectroscopies reveal the presence of covalent sidewall functionalization. The percentage of residues for DPC-MWCNTs was found to be lower than that for pristine MWCNTs, which indicates the existence of functional groups on the sidewalls of DPC-MWCNTs. It is shown that the sidewall of the DPC-MWCNTs was covered by non-uniform layer of DPC, as observed by transmission electron microscopy (TEM). Results from Raman spectroscopy, FTIR, TGA, UV–vis spectroscopy and TEM confirm that the functionalization of the covalent sidewalls of MWCNTs was successfully performed by this method.     

Investigation of the interfacial reaction between multi-walled carbon nanotubes and aluminum

Aluminum (Al)/carbon nanotube (CNT) composite films were fabricated by sputtering pure Al on the surface of aligned multi-walled CNT arrays. Heat treatment was performed in the temperature range 400–950 °C. The interfacial reaction between the Al and the CNTs was investigated by annealing the samples at various temperatures. The results indicated that aluminum carbide (Al₄C₃) was formed at the interface between the Al and CNT layers, and microscopy observation revealed that the reaction generally occurred at locations containing an amorphous carbon coating, at defect sites, and at open ends of CNTs. Because the nanosized CNTs are precursors for carbide formation, the Al₄C₃ formed is also nanoscale in size. The carbide formed on the surface as well as on the tips of the CNTs improves the interfacial interaction between the CNTs and the Al layers. This also contributes to the enhancement of the mechanical properties of the composite. Our investigation demonstrated that chemical vapor deposited CNTs are a suitable candidate as reinforcing material for Al and other metal matrices.     

Vibrational properties of the electrochemically synthesized polyindole/single-walled carbon nanotubes composite

Electrochemical polymerization of indole in a LiClO₄/CH₃CN solution on a single-walled carbon nanotubes (SWNTs) film was studied by cyclic voltammetry, Raman scattering and FTIR spectroscopy. Comparing the cyclic voltammograms recorded on a blank Pt electrode with those obtained when carbon nanotubes films were previously deposited onto the Pt electrode, a down-shift of the indole reduction peak potential in the latter case was observed. Raman spectroscopy studies indicate that the electrochemical deposition of polyindole (PIN) onto the SWNT film results in a breaking of SWNT bundles into individual tubes. A covalent functionalization of SWNTs with PIN in the doped state is demonstrated by FTIR spectroscopy, when an increase in the intensity of the absorption band at 1045 cm^?1 is observed. Besides, Raman and FTIR studies performed on samples electrochemically prepared and thereafter post-chemically reacted with an NH₄OH solution, indicate both a roping process of individual tubes with PIN as a binding agent and a strong steric hindrance effect.     

Adsorption and inhibition effect of novel cationic surfactant for pipelines carbon steel in acidic solution

A new cationic surfactant was prepared and examined as an inhibitor for the corrosion of carbon steel in 1.0 M HCl solution using weight loss measurements, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The chemical structure of the prepared cationic surfactants has been proven by FTIR spectra. The inhibiting effect of the cationic surfactant as a result of the formation of the protective layer adsorbed on the carbon steel surface The adsorption of the inhibitor was discussed accordingly to the Langmuir isotherm. Polarization data indicated that the cationic surfactant is a mixed-type inhibitor.. The effect of temperature on the corrosion rate of carbon steel in1. 0 M HCl solution devoid of and containing the novel cationic surfactant was examined and thermodynamic parameters were computed. Some surface parameters were calculated and explained.     

Immobilization of DNA on nano-hydroxyapatite and their interaction with carbon nanotubes

Here we present a preliminary study on the interaction of bio-molecules (deoxyribonucleic acid (DNA) and nano-hydroxyapatite (HA)) with multi-wall carbon nanotubes (MWCNTs). Initially, nano-size hydroxyapatite was interacted with functionalized carbon nanotubes (FCNTs, HFCNTs) and then 100 base pair (bp) DNA was immobilized (DHFCNTs). Well-known acid treatment was used to functionalize the MWCNTs. The characteristic vibrational and stretching modes of hydroxyl and carbonyl group were observed at 3401, 1632 and 1708 cm^?1, validating fucntionalization. The existence of ³¹P and ¹H signals were measured by the solid state NMR spectroscopy for HA, HFCNTs and DHFCNTs which revealed the chemical interaction between HA powder and FCNTs. Appearance of an N 1s peak in the photoelectron spectra indicated the covalent attachment. Band deterioration is observed from slab gel-electrophoresis studies. Electrophoretic time study indicated that 20 min is required to run the DNA in column.     

Synthesis, characterization and microwave absorption property of doped polyaniline nanocomposites containing TiO2 nanoparticles and carbon nanotubes

As nanomaterial possessing moderate conductivity, magnetic and dielectric property, novel hexanoic acid (HA)-doped polyaniline (PAni) nanocomposites containing TiO₂ nanoparticles (dielectric filler) and carbon nanotubes, CNTs (magnetic fillers such as single-walled carbon nanotube, SWNT and multi-walled carbon nanotube, MWNT) were prepared by template free method. The PAni were characterized by UV, FTIR, X-ray diffraction (XRD), thermogravimetric (TGA) and scanning electron microscopy (SEM) analyses. Conductivity, magnetization, dielectric and microwave absorption properties of PAni were also investigated. The resulted nanorods/tubes as shown in SEM images clearly show that polymerization is proceeded in micelle/water interface through elongation. During template free method, TiO₂ and CNT exist in the center of Ani/HA micelle. The SEM images show that some of the CNT enwrapped with PAni layer indicate CNT are just packed underneath the PAni and never attacked by PAni. PAni/HA/TiO₂/SWNT with 20% of SWNT exhibits the best microwave absorption property (99.2% absorption) with reflection loss of −21.7 dB at 6 GHz due to its moderate conductivity (1.27 S/cm), magnetization (M_s = 1.01 emu/g), highest tan δ and heterogeneity.     

CO sensor based on polypyrrole functionalized with iron porphyrin

Polypyrrole (PPy) was chemically functionalized with 5,10,15,20-tetraphenyl-21H,23H-porphyrin iron(III) chloride (FeTPPCl) with special interest on noxious carbon monoxide (CO) gas in ppm level. Controlled functionalization of PPy was achieved with incorporation of various concentrations of porphyrin. The resulted semiconducting material was well characterized by different techniques such as UV–vis spectroscopy, FTIR, GFAAS, XRD, and EDAX. The functionalized polypyrrole material on interdigitated electrode was experienced an immediate increase in resistance when exposed to carbon monoxide gas at very low concentration. The CO gas interacted very fast with the FeTPPCl functionalized PPy at room temperature (RT) and then slowly saturated. The response of these materials was not unidirectional, but reverses to the original resistance level when CO was removed from the test chamber. The highest response factor (ΔR/R₀ × 100) and lowest response time (t₅₀) obtained are 12 and 169 s, respectively. An optimum level of doping (1 mol% of FeTPPCl) was established for the highest sensitivity and the detection level is as low as 100 ppm.     

Highly dispersible polymer-coated silver Nanoparticles

Highly dispersible silver nano-material was obtained by surface functionalization of silver nanoparticles with polylactic acid. The thiolation method was used for attaching carboxyl groups to the silver surface by treatment with 3-mercaptopropionic acid. The carboxyl groups were further activated by diisopropylcarbodiimide and reacted with polylactic acid. The functionalized nanoparticles contained 1.88 wt.% organic phase. While the as-received silver nanopowder exhibited poor colloidal stability in tetrahydrofuran, particle size analysis revealed that the functionalized material displayed high dispersibility in this solvent.     

Strengthening of C/SiC Composites by Electrophoretic Deposition of CNTs on a SiC Coating

The current study reports the enhancement of mechanical properties of carbon fiber-reinforced silicon carbide ceramic matrix composites (C/SiC CMCs) by the application of a carbon nanotube/silicon carbide (CNT/SiC) coating. CNTs were deposited on the surfaces of C/SiC composites using electrophoretic deposition (EPD), after which infiltration by SiC was achieved through a chemical vapor infiltration process. An EPD duration of 5 min was associated with a 40% increase in the ultimate flexural strength relative to that of composites with a pure SiC coating. The observed enhancement was rationalized by the microstructural observations of SiC infiltration into the porous CNT morphology and the subsequent formation of CNT/SiC layers on the surfaces of the composites and by the inherent toughness of the SiC whiskers. The flexural strength decreased with EPD durations greater than 5 min due to the formation of thick CNT meshes, which decreased the open porosity and thereby obstructed further SiC infiltration. This is a viable methodology for the improvement of mechanical properties of CMCs by the introduction of a ceramic coating containing CNT.     

Immobilization of avidin on the functionalized carbon nanotubes

Immobilization of avidin was carried out by functionalizing the multi-wall carbon nanotubes (MWCNTs). Treatment with nitric acid and sulfuric acid mixture (1:3, optimized ratio) leads to the functionalization of nanotubes as observed from Fourier transform infrared absorption spectroscopy (FTIR) measurements. Avidin was coupled with the solution of N-hydroxysuccinimide (NHS) and 1-ethyl-3-(3-dimethylamino propyl)-carbodiimide hydrochloride (EDC) and then immobilized on nanotubes. X-ray photoelectron spectroscopic (XPS) studies show a shift in the peak position of C 1s towards lower energy side and changes in the bands with treatment/immobilization. The shoulders and shift in photoelectron peak positions indicate the destruction of the graphite structure of the surface layer. SEM images showed that after functionalization, the nanotubes are seen with open ends, granular surface and are joined together. This indicates that after treatment, the CNTs reactivity increased at the ends as well as at the sidewalls. It is believed that the NHS often assist the carbodiimide coupling in the presence of EDC, reacts with the amine function to yield the amide bond. The carbodiimide catalyzes the formation of amide bonds between carboxylic acids and amines by activating carboxyl. The reaction of complex containing avidin can form a covalent bond with functionalized carbon nanotubes as observed from FTIR and XPS measurements.     

Synthesis and Characterization of Novel Sulfur-Functionalized Silica Gels as Mercury Adsorbents

This paper describes the synthesis, functionalization, and characterization of silica gels as mercury adsorbents. The synthesis was carried out according to the modified Stöber method using tetraethyl orthosilicate [TEOS], 3-mercaptopropyl trimethoxysilane [MPTMS] and bis(triethoxysilylpropyl) tetrasulfide [BTEPST] as precursors. The functionalization was carried out via co-condensation and impregnation methods using MPTMS, BTESPT, elemental sulfur [ES], and carbon disulfide [CS₂] as sulfur ligands. The choice of the sulfur ligands as precursors and functionalization agents was due to the existence of sulfur active groups in their molecular structures which were expected to have high affinity toward Hg(II) ions. The synthesized adsorbents were characterized by using scanning electron microscope, fourier transform infrared spectrophotometer, nitrogen adsorption/desorption, and energy dispersive X-ray diffractometer. The batch Hg(II) adsorption experiments were employed to evaluate the Hg(II) adsorption performances of the synthesized adsorbents under different pH values. The results revealed that the highest Hg(II) adsorption capacity was obtained for the SG-MPTMS(10) which was 47.83 mg/g at pH 8.5. In general, the existence of sulfur functional groups, especially MPTMS in the silica matrices, gave a significant enhancement of Hg(II) adsorption capacity and the sulfur functionalization via co-condensation method, which is potential as a superior approach in the mercury adsorbent synthesis.     

Polypyrrole coated carbon nanotubes: Synthesis,characterization, and enhanced electrical properties

We describe a simple approach to the synthesis of MWNT/polypyrrole nanotubes by the in situ chemical polymerization of pyrrole on the carbon nanotubes using ferric chloride as an oxidant. The effects of pyrrole concentration on the coating and properties of the resulting complex nanotubes were studied by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction, and thermal gravimetric analysis. The coated PPy layers could be controlled easily by adjusting a feed ratio of pyrrole to MWNTs. FT-IR results suggested an existence of interaction between the –COOH groups of chemically modified MWNTs and NH groups of the PPy. SEM and TEM studies indicated that each individual MWNT could be coated with PPy. The resultant nanotubes enhanced electrical conductivity compared to PPy and MWNT which was strongly influenced by the feed ratio of pyrrole to MWNTs.     

Composition and properties of functional groups on surface of carbon sorbents modified by aminocaproic acid

The composition and properties of functional groups on the surface of carbon sorbents modified with aqueous solutions of aminocaproic acid of different concentrations were studied using physicochemical analysis methods: including acid-base titration, the Kjeldahl method, scanning electron microscopy, X-ray microanalysis, and X-ray photoelectron spectroscopy. The initial carbon sorbent was shown to have almost no functional groups on its surface. It was ascertained that the surface functionalization of carbon sorbent results in a change in microstructure and an increase in the amount of oxygen- and nitrogen-containing groups with increasing concentration of the modifying agent followed by its further polycondensation on the surface. According to the XPS data, the formation of the bond between aminocaproic acid and the carbon surface of sorbents occurs via a carboxylic group.     

The effect of carbon nanotubes on biomineralization and solubility of calcium hydroxyapatite Ca10(PO4)6(OH)2

Toxic characteristics of carbon nanotubes (CNTs) were estimated through the modeling of interaction between CNTs and the inorganic component of osseous tissue of mammals—calcium hydroxyapatite Ca₁₀(PO₄)₆(OH)₂ (HA)—under the conditions of biomimetic formation of HA/CNT composites containing 0.1, 1, and 5 wt % CNT. Synthesis products were identified using the methods of chemical analysis, XRD, DTG, DTA, IRS, SEM, TEM, and DE. The effect of nanotubes on crystallographic and morphological characteristics of nanocrystalline HA and solubility of HA/CNT composites was determined.     

Batch-mode micropatterning of carbon nanotube forests using UV-LIGA assisted micro-electro-discharge machining

This paper reports batch-mode, three-dimensional micropatterning for arrays of vertically aligned carbon nanotubes, also known as CNT forests, based on dry micro-electro-discharge machining (μEDM). The process employs an array of copper electrodes microfabricated through an advanced UV-LIGA process enabled with a new photoresist system in combination with electroplating, providing a low-cost path to constructing high-density arrays of μEDM electrodes for high-throughput parallel processing. The fabricated arrays of 85-μm-tall electrodes are utilized to demonstrate and characterize planar dry μEDM for post-growth patterning of CNT forests in air. Die sinking and scanning processes are tested to show pattern transfers with a 4-μm tolerance and an average surface roughness of 230 nm. An elemental analysis suggests that contamination of the electrode material on the produced patterns is minimal. Key characteristics in the use of planar electrodes for batch processing of CNT forests are revealed through experimental analysis and discussed in detail. The results suggest that the investigated process is a promising approach toward offering a cost-effective manufacturing technology for future products functionalized with custom-designed microstructures of CNT forests.     

Hydrogen sensors based on carbon nanotubes thin films

Single-walled carbon nanotubes (SWNTs) produced by arc-discharge have been researched as resistive gas sensors for H₂ detection. Raw as well as modified single-walled carbon nanotubes were utilised as sensor material. Two types of modification treatments were carried out on the as grown SWNT material; chemical functionalization with palladium and doping with palladium by sputtering.CNTs were deposited on alumina substrates by airbrush. Two different alumina substrates (with and without heater element) were used to obtain the sensor devices.Conductance measurements were carried out in a N₂ constant flow for H₂ detection. The results demonstrate that the CNTs are p-type semiconductor materials, increasing their resistance with reducing gases. SWNTs functionalized with Pd show the best response when exposed to H₂ at room temperature.