Surface-modified Carbon Research Articles

Surface-modified carbon nanotube coating on high-voltage LiNi0.5Mn1.5O4 cathodes for lithium ion batteries

Surface-modified carbon nanotubes were utilized as a coating for LiNi0.5Mn1.5O4 (LNMO) via a mechano-fusion method as a strategy to prevent unfavorable carbothermal reduction. Two types of carbon nanotubes were investigated as coating materials: carbon nanotubes (CNTs) and oxidized carbon nanotubes (OCNTs), which were prepared by a simple re-oxidation process. The samples coated with CNTs or OCNTs were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning and transmission electron microscopy, Raman spectroscopy, and elemental analyses. The OCNT-coated LNMO presented a highly enhanced discharge capacity retention (95.5%) and a coulombic efficiency of 99.9% after 80 cycles between 3.5 and 4.9 V (versus Li/Li+), whereas the CNT-coated LNMO exhibited poor retention of 47.2% and a coulombic efficiency of 95.3%. In addition, post-mortem XPS and electrochemical impedance spectroscopy (EIS) analysis proved that the OCNT coating improved the surface electrochemical stability and rate capability, whereas the CNT coating formed a thick resistive solid electrolyte interphase (SEI) film by accelerating the surface side reactions.

Hydrochromic Approaches to Mapping Human Sweat Pores.

Hydrochromic materials, which undergo changes in their light absorption and/or emission properties in response to water, have been extensively investigated as humidity sensors. Recent advances in the design of these materials have led to novel applications, including monitoring the water content of organic solvents, water-jet-based rewritable printing on paper, and hydrochromic mapping of human sweat pores. Our interest in this area has focused on the design of hydrochromic materials for human sweat pore mapping. We recognized that materials appropriate for this purpose must have balanced sensitivities to water. Specifically, while they should not undergo light absorption and/or emission transitions under ambient moisture conditions, the materials must have sufficiently high hydrochromic sensitivities that they display responses to water secreted from human sweat pores. In this Account, we describe investigations that we have carried out to develop hydrochromic substances that are suitable for human sweat pore mapping. Polydiacetylenes (PDAs) have been extensively investigated as sensor matrices because of their stimulus-responsive color change property. We found that incorporation of headgroups composed of hygroscopic ions such as cesium or rubidium and carboxylate counterions enables PDAs to undergo a blue-to-red colorimetric transition as well as a fluorescence turn-on response to water. Very intriguingly, the small quantities of water secreted from human sweat pores were found to be sufficient to trigger fluorescence turn-on responses of the hydrochromic PDAs, allowing precise mapping of human sweat pores. Since the hygroscopic ion-containing PDAs developed in the initial stage display a colorimetric transition under ambient conditions that exist during humid summer periods, a new system was designed. A PDA containing an imidazolium ion was found to be stable under all ambient conditions and showed temperature-dependent hydrochromism corresponding to a colorimetric change near body temperature. This feature enables the use of this technique to generate high-quality images of sweat pores. This Account also focuses on the results of the most recent phase of this investigation, which led to the development of a simple yet efficient and reliable technique for sweat pore mapping. The method utilizes a hydrophilic polymer composite film containing fluorescein, a commercially available dye that undergoes a fluorometric response as a result of water-dependent interconversion between its ring-closed spirolactone (nonfluorescent) and ring-opened fluorone (fluorescent) forms. Surface-modified carbon nanodots (CDs) have also been found to be efficient for hydrochromic mapping of human sweat pores. The results discovered by Lou et al. [ Adv. Mater. 2015 , 27 , 1389 ] are also included in this Account. Sweat pore maps obtained from fingertips using these materials were found to be useful for fingerprint analysis. In addition, this hydrochromism-based approach is sufficiently sensitive to enable differentiation between sweat-secreting active pores and inactive pores. As a result, the techniques can be applied to clinical diagnosis of malfunctioning sweat pores. The directions that future research in this area will follow are also discussed.

"Patchy" Carbon Nanotubes as Efficient Compatibilizers for Polymer Blends.

Surface-modified carbon nanotubes (CNTs) have become well-established filler materials for polymer nanocomposites. However, in immiscible polymer blends, the CNT-coating is selective toward the more compatible phase, which suppresses their homogeneous distribution and limits harnessing the full potential of the filler. In this study, we show that multiwalled CNTs with a patchy polystyrene/poly(methyl methacrylate) (PS/PMMA) corona disperse equally well in both phases of an incompatible PS/PMMA polymer blend. Unlike polymer-grafted CNTs with a uniform corona, the patchy CNTs are able to adjust their corona structure to the blend phases by selective swelling/collapse of respective miscible/immiscible surface patches. Importantly, the high interfacial activity of patchy CNTs further causes a significant decrease in PMMA droplet size with increasing filler content. The combined effect of compatibilization and homogeneous distribution makes patchy CNTs interesting materials for polymer blend nanocomposites, where next to the compatibilization, a homogeneous filler distribution is important to gain the desired materials property (e.g., reinforcement).

Easy approach to assembling a biomimetic color film with tunable structural colors

The self-assembly of silica microspheres into a close-packed array is a simple method of fabricating three-dimensional photonic crystal structural color films. However, the color is very dull because of the interferences of scattering and background light. In this study, we added a small quantity of surface-modified carbon black (CB) to the system of colloidal silica in n-propanol. The use of n-propanol as a dispersant is beneficial to the rapid development of photonic crystal films during the process of dip-coating. The doping of CB into silica microspheres can absorb background and scattering light, resulting in vivid structural colors.

Encapsulation of surface-modified carbon blacks by poly(sodium-p-styrenesulfonate) via a phase separation method

Carbon black (CB) encapsulated by poly(sodium-p-styrenesulfonate) (PSS) via a strong π–π interaction was prepared with the use of ethyl alcohol by a simple phase separation method. Surface treatment was carried out to provide CB particles a better dispersity in water before encapsulation. The result of Fourier transform infrared spectroscopy demonstrated the existence of PSS chains on the surface of coated CB. A nanoparticle with a core/shell structure was clearly observed by transmission electron microscope, while the Raman spectroscopy consequence displayed a structure change of CB after encapsulation. The result of thermal gravimetric analysis indicated that the particle size of CB and the introduction of ethyl alcohol during the experiment are of great importance to prepare hydrophilic carbon black with high encapsulation ratio. Compared to pristine CB, the encapsulated CB exhibited a superb stability in aqueous medium according to the consequence of centrifuging sedimentation.

Transport of Surface-modified Carbon Nanotubes through a Soil Column

Carbon nanotubes (CNTs) are widely manufactured nanoparticles, which are being utilized in a number of consumer products, such as sporting goods, electronics and biomedical applications. Due to their accelerating production and use, CNTs constitute a potential environmental risk if they are released to soil and groundwater systems. It is therefore essential to improve the current understanding of environmental fate and transport of CNTs. The transport and retention of CNTs in both natural and artificial media have been reported in literature, but the findings widely vary and are thus not conclusive. There are a number of physical and chemical parameters responsible for variation in retention and transport. In this study, a complete procedure of selected multiwalled carbon nanotubes (MWCNTs) is presented starting from their surface modification to a complete set of laboratory column experiments at critical physical and chemical scenarios. Results indicate that the stability of the commercially available MWCNTs are critical with their attached surface functional group which can also influence the transport and retention of MWCNT through the surrounding medium.

Transport of surface-modified carbon nanotubes through a soil column.

Carbon nanotubes (CNTs) are widely manufactured nanoparticles, which are being utilized in a number of consumer products, such as sporting goods, electronics and biomedical applications. Due to their accelerating production and use, CNTs constitute a potential environmental risk if they are released to soil and groundwater systems. It is therefore essential to improve the current understanding of environmental fate and transport of CNTs. The transport and retention of CNTs in both natural and artificial media have been reported in literature, but the findings widely vary and are thus not conclusive. There are a number of physical and chemical parameters responsible for variation in retention and transport. In this study, a complete procedure of selected multiwalled carbon nanotubes (MWCNTs) is presented starting from their surface modification to a complete set of laboratory column experiments at critical physical and chemical scenarios. Results indicate that the stability of the commercially available MWCNTs are critical with their attached surface functional group which can also influence the transport and retention of MWCNT through the surrounding medium.

Influence of the carbon nanotube surface modification on the microstructure of thermoplastic binders

The structural properties of polymer nanocomposites based on thermoplastic polyimides filled with surface-modified carbon nanotubes (CNT) have been studied by means of fully-atomistic molecular-dynamics simulations.

Enhanced performances of microbial fuel cells using surface-modified carbon cloth anodes: A comparative study

In this study, performances of two-chamber microbial fuel cells (MFCs) with surface-modified carbon cloth anodes by four methods are compared including soaking in aqueous ammonia (CC-A), electrolysis in phosphate buffer (CC-P), electrolysis in nitric acid (CC-N) and electrolysis in nitric acid followed by soaking in aqueous ammonia (CC-NA). It is found that performances of all these modified anodes are better than that of the bare one. The MFC with the anode modified by CC-NA yield the maximum power density of 3.20 ± 0.05 W m−2, which is 58%, 36%, 35% and 28% higher than those of the MFC with untreated anode (CC-C, 2.01 ± 0.02 W m−2), and treated by the CC-A (2.35 ± 0.15), CC-N (2.38 ± 0.02 W m−2) and CC-P (2.50 ± 0.08 W m−2) methods, respectively. The active biomass and EIS analysis for the anodes indicated that the highest power output of the CC-NA MFC may primarily attributed to the enhanced electron transfer resulting from the existence of quinoid groups on the CC-NA surface, rather than the biomass effect. Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopic analyses of the CC-NA anode further demonstrate that the formation of quinoid groups contributes to the improvement in the MFC performance by accelerating the electron transfer between electrochemically active bacteria (EAB) and the anode surface.

Insight into the activation of light alkanes over surface-modified carbon nanotubes from theoretical calculations

The activation and conversion of light alkanes (such as methane, ethane, propane and isobutane) has attracted more and more attention in both industrial and fundamental aspects. Compared to the traditional metal catalysts, carbon catalysts have environmental acceptability with inexhaustible resources. Considerable experimental work concerning the activation of light alkanes by surface-modified carbon nanotubes (CNTs) has been reported, however, both the active centers and the catalytic reaction mechanisms still remain unclear. In our theoretical calculations, a number of possible pathways for the activation of light alkanes over various types of oxygen-containing surface groups of surface-modified CNTs were theoretically explored. It was demonstrated for the first time that the diketone-like carbonyl groups residing in two neighboring phenyl rings at the edges or in the defects of CNTs show reactivity as high as the conventional metal oxide catalysts, and that the metallic CNTs usually have much higher catalytic reactivity with respect to the semi-conducting CNTs.

Application of surface-modified carbon powder in microbial fuel cells

The catalytic activity of surface-modified carbon powder, Vulcan XC-72R (XC), for the oxygen reduction reaction (ORR) at an air cathode in a microbial fuel cell (MFC) has been investigated. The effects of treatment with different chemicals such as nitric acid and ammonia on the chemical characteristics of XC were studied. The catalysts were characterized by Fourier transform infrared spectroscopy (FTIR), Boehm titration, and X-ray photoelectron spectroscopy. FTIR analysis showed that the functional groups of the materials were changed by chemical treatment, with nitric acid causing the introduction of oxygen-containing groups, and ammonia leading to the introduction of nitrogen-containing groups. Electrochemical measurements of MFCs containing various modified carbon materials as ORR catalysts were performed, and the results showed that chemically modified carbon materials are promising catalysts in MFCs. The introduction of nitrogen- and oxygen-containing surface functional groups onto carbon catalysts improved their catalytic activity toward the oxygen reduction reaction in microbial fuel cells.

Surface Modification of Carbon for High Power Density Biofuel Cell Using High-Surface-Area Electrode Made of Redox-Polymer-Grafted Carbon

Enzymatic biofuel cells can use a variety of fuels such as glucose and ethanol, and they have the potential to power portable devices near the body. However, power densities of biofuel cells were very low because of their low current density. Recent advances in designing three-dimensional conducting electrode materials have resulted in superior performances of current density of over 10 mA cm–2 even without addition of mediators in solution, as summarized in ref[1]. Considering the high intrinsic activity of enzymes, the current density can be increased further to reach 102 mA cm–2, a value comparable with that observed in conventional direct methanol fuel cells.We have proposed a high-surface-area three-dimensional biofuel cell electrode made of redox-polymer-grafted carbon to obtain high current density [2-4]. The rate-limiting step in mediated enzyme electrodes has been electron conduction via a redox polymer, which shuttles electrons from the enzyme to the electrode, due to the low apparent electron diffusion coefficient in the redox polymer [5]. In our electrode, the three-dimensional carbon electrode with high surface area and high electron conductivity plays the primary role in conducting electrons; thus, the electron conduction distance in the redox polymer was reduced, overcoming the rate-limiting step. Schematic illustration of this electrode is shown in Fig. 1. The effectiveness of the high-surface-area electrode was verified by experiments using the electrode as a glucose-oxidizing bioanode with glucose oxidase (GOx) [2,3], and a mathematical model [4]. The model calculation suggests that the rate-limiting step of apparent electron diffusion is overcome by using the proposed electrode even when the redox polymer has a low apparent electron diffusion coefficient, and an increase in the surface coverage of GOx allows an increase in the current density to the order of 102 mA/cm2. The reason of the low surface coverage of GOx in the experiments was then investigated, and shown to be mainly due to the deactivation of GOx upon adsorption on hydrophobic surface of carbon black [6]. Hence, to increase the current density to about 102 mA/cm2, the deactivation of enzymes upon physical adsorption on carbon black should be decreased.In this work, we modified surface of carbon black by physically mixing carbon black with hydrophilic materials and by chemical treatment to retain GOx activity upon physical adsorption on carbon black. Hydrophilic materials used was polyethylene glycol (PEG) with hydrophobic end-group, diacylglycerol-PEG. Chemical treatment was acid-treatment using a mixed solution of nitric acid and sulfuric acid followed by graft-polymerization of poly(2-acrylamido-2-methylpropane sulfonic acid) (pAMPS). Surface-modified carbon black was then stirred in GOx solution to adsorb GOx, and the amount of the enzyme adsorbed on carbon black was evaluated using HPLC.Figure 2 shows the adsorbed amount of GOx compared with the amount of GOx in solution mixed with the surface-modified carbon black. Under the condition where GOx fully adsorbed to unmodified carbon black, surface modification by diacylglycerol-PEG, and acid-treatment with following graft polymerization of pAMPS effectively prevented the adsorption of GOx onto carbon black.In summary, the surface treatment of carbon black to make hydrophilic surface is effective in reducing the physical adsorption of GOx, and thus has a possibility to realize high-power density biofuel cells by preventing deactivation of enzymes upon physical adsorption onto carbon.

카본블랙의 표면개질이 중합토너의 특성에 미치는 영향

Carbon black was surface-modified to prepare styrene-based suspension polymerized toner with excellent carbon black dispersibility inside toner particles. Carbon black was oxidized first to introduce hydroxyl groups on the surfaces, then esterification between the hydroxyl groups and carboxyl groups of organic acids (oleic acid, palmitic acid, acrylic acid) was followed to obtain organically surface-modified carbon black. The surface-modification of carbon black was confirmed by FTIR. Apparent carbon black dispersibility in the monomer mixture of the binder resin was tested and the particle size of dispersed carbon black was measured by particle size analyzer. Optical micrographs showed that carbon black dispersibility inside toner particles was improved considerably when the carbon black surfacemodified with oleic acid was used. The polymerized toner prepared with the carbon black surface-modified with oleic acid showed ideal particle size and size distribution as a toner.

Evaluation of Effect of Various Nanofillers on Technological Properties of NBR/NR Blend Vulcanized Using BIAT-CBS System

Owing to processing ease and resistance to oils and chemicals, NBR is widely used in many industries. But since neat NBR has only poor tensile properties, it is better to use suitable blends of NR and NBR after incorporating appropriate nanoingredients before vulcanization. It is well established that nanoparticles can be easily dispersed in a more uniform pattern in polymer matrix, thereby enhancing the technological properties of the elastomer vulcanizate. Since there are no systematic comparative studies on technological properties of NBR/NR blend containing different nanoingredients, efforts have been made in this study to investigate cure and technological properties like tensile properties, tear resistance, compression set, hardness, abrasion loss and swelling value of NBR/NR (80/20) blend vulcanizates containing stearic acid-coated nano-zinc oxide (ZOS), nano-BIAT, nano-silicate-coated CaCO3, PEO-coated calcium silicate, and surface-modified carbon nanotubes (CNT). XRD and electron microscopy have been used for morphological analysis. The nano ingredients were effective in enhancing the technological properties of the vulcanizates. Among the nanofillers, modified CNT was found to impart superior properties to NBR/NR blend due to more intercalation.

CARBON NANOTUBES AND NANO-Ce–Zr OXIDES SUPPORTED H3PW12O40 FOR EFFECTIVE ADSORPTION–DECOMPOSITION OF NOx

Surface-modified carbon nanotubes (CNTs) and nano- Ce–Zr mixed oxides (CZO) were prepared and employed initially as supports of H3PW12O40 (HPW) for NO x adsorption–decomposition. Both CNTs and nano-CZO are favorable supports for HPW. After loading with HPW, the NO x adsorption efficiency increases, especially for HPW/CZO in which the highest adsorption efficiency can achieve 98% at the HPW loading of 70%, much higher than that of single HPW. NO x adsorption efficiency can be influenced considerably by catalyst preparing conditions, in particularly, ethyl alcohol is superior to water as solvent for HPW loading onto CNTs; the –OH containing CNTs shows better promotion effect on the adsorption of NO x than that containing –COOH when using absolute ethyl alcohol as solvent; mechanical grinding method is superior to incipient impregnation method in loading HPW onto the support of CZO. For both catalysts of HPW/CNTs and HPW/CZO, with the increase of HPW loading, the NO x adsorption efficiency tends to reach a peak value before dropping down. Heated from 150°C to 450°C at a rate of 50°C/min, the adsorbed NO was found to decompose into N2 , O2 and N2O , and yields of N2 being 21.8% and 27.3%, respectively for HPW/CNTs and HPW/CZO were obtained.

Modification of Zr-doped titania nanotube arrays by urea pyrolysis for enhanced visible-light photoelectrochemical H2 generation

Zr-doped TiO2 nanotube arrays (Zr-TiO2-NT) and TiO2 nanotube arrays (TiO2-NT) were prepared via anodic oxidation of titanium foils in ethylene glycol solution and modified by heat treatment in the presence of urea pyrolysis products at 400°C. Zr doping changes the morphology of Zr-TiO2-NT and its conduction band edge shifts negatively compared with that of TiO2-NT. For the modification of Zr-TiO2-NT in the presence of urea pyrolysis products, Zr doping can not only enhance the polymerization degree of the surface-modified carbon nitride polymers but also promote the N doping. The modified TiO2-NT and Zr-TiO2-NT films exhibit significant photocurrent responses upon visible light irradiation. Zr doping improves markedly the visible-light photoelectrochemical H2 production of the modified Zr-TiO2-NT.

Synthesis of modified carbon nanotube-reinforced thiazole dyes/silica hybrid materials

A series of novel hybrid materials prepared via the sol–gel process is synthesized from carbon nanotubes, tetraethoxysilane, and heteroaryl 2-aminothiazole azo dyes. The starting material thiazole is synthesized from thiourea, acetophenone, and iodide to obtain 4-phenyl-2-aminothiazole. 4-phenyl-2-aminothiazole, which is a coupling component, is coupled with p-methoxyaniline, which is a diazo component, in an ice bath to produce heterocyclic 4-phenyl-2-aminothiazole azo dyes. Hybrid materials composed of carbon nanotube/SiO2/thiazole azo dyes are synthesized via the sol–gel process using a precursor system. Heterocyclic 4-phenyl-2-aminothiazole azo dyes undergo a hydrolysis-condensation reaction with an appropriate proportion of surface-modified carbon nanotubes under a catalyst, at a constant ratio of vinyltriethoxysilane to tetraethoxysilane. The structures of these hybrid materials composed of carbon nanotube/SiO2/thiazole azo dyes are characterized using thermogravimetric analysis, Fourier transform-infrared spectroscopy, Raman spectroscopy, 29Si-nuclear magnetic resonance spectroscopy, and energy-dispersive X-ray spectroscopy.

Binary oxide-doped Pt/RuO2–SiOx/C catalyst with high performance and self-humidification capability: The promotion of ruthenium oxide

A multifunctional catalyst for fuel cell applications, Pt/RuO2–SiOx/C, has been prepared by supporting platinum nanoparticles on surface-modified carbon black, fabricated by in situ hydrolysis of ruthenium and silicon precursors on pre-treated carbon black. The catalyst is extensively characterized by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The catalyst shows high activity toward methanol oxidation and oxygen reduction at room temperature. Notably, the addition of ruthenium oxide significantly improves the performance of MEAs under non-humidified conditions. The self-humidification performance of MEAs prepared with Pt/RuO2–SiOx/C (using optimized 3wt.% RuO2) as the anode catalyst is enhanced by over 20% compared to MEAs prepared with Pt/SiOx/C as the anode catalyst. It is suggested that the promotion of RuO2 may result from the high dispersion of platinum caused by adding ruthenium oxide, and the synergistic effect of ruthenium oxide.

Study on the friction and wear behavior of surface‐modified carbon nanotube filled carbon fabric composites

AbstractThe functionalization of multi‐walled carbon nanotubes (MWNTs) was achieved by grafting furfuryl amine (FA) onto the surfaces of MWNTs. Furthermore, the functional MWNTs were incorporated into carbon fabric composites and the tribological properties of the resulting composites were investigated systematically on a model ring‐on‐block test rig. Friction and wear tests revealed that the modified MWNTs filled carbon fabric composite has the highest wear resistance under all different sliding conditions. Fourier transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), and thermal gravimetric analysis (TGA) revealed that MWNTs were successfully functionalized and the modification led to an improvement in the dispersion of MWNTs, which played an important role on the enhanced tribological properties of carbon fabric composites. It can also be found that the friction and wear behavior of MWNTs filled carbon fabric composites are closely related with the sliding conditions such as sliding speed, load, and lubrication conditions. Copyright © 2010 John Wiley & Sons, Ltd.

Fabrication of uranium oxycarbide kernels and compacts for HTR fuel

Fabrication of uranium oxycarbide kernels and compacts for HTR fuel