Oxidation and reduction of multiwalled carbon nanotubes — preparation and characterization

This work presents the use of a modified titration (Boehm's) process which is a simple and efficient method to quantify functional groups formed on the surface of oxidized multiwalled carbon nanotubes (MWCNTs). The MWCNTs were synthesized via chemical vapor deposition (CVD) and were purified through a hydrochloric acid treatment. Purified material was oxidized in a mixture of nitric and sulfuric acids. A part of oxidized sample was reduced with sodium borohydrate (NaBH₄). Boehm's titration is a complimentary method to Fourier Transform Infrared spectroscopy (FT-IR) with which to investigate the changes to the surface of oxidized MWCNTs after the reduction process. The reduction process led to threefold increase in the hydroxyl group content. In addition, the pristine, oxidized and reduced samples were investigated by thermogravimetry analysis (TGA) and Raman spectroscopy.     

Graphene oxide: the mechanisms of oxidation and exfoliation

Graphene oxides (GOs) with large sheets and more perfect aromatic structure were prepared by a novel modified Hummers method. We demonstrated that the graphite did not need to be oxidized to such a deep degree as described in Hummers method because the space distance increased little when the oxidation proceeded to a certain extent and the obtained graphite oxides (GTOs) could be fully exfoliated to single layers with high thermal stability. The oxidation mechanism and chemical structure model of GO were proposed by analyzing the evolution of the functional groups with oxidation proceeded based on thermogravimetric analysis, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The layer spacing calculated by molecular dynamics simulations coincided with the X-ray diffraction results. Furthermore, the size distribution and thickness of GOs were also studied. The results confirmed that the GOs prepared by the modified method were fully exfoliated to uniform single layers, and this method may be important for efficient exfoliation of GTO to GO and large-scale production of graphene.     

Ozone-Mediated Functionalization of Multi-Walled Carbon Nanotubes and Their Activities for Oxygen Reduction Reaction

The functionalization of multi-walled carbon nanotubes(MWCNTs)by ozone treatment has been systematically investigated by using Raman spectroscopy,transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS),organic elemental analysis(OEA)and Boehm titration.The results showed that the functionalization process occurred at defective sites(opened mouths,tube caps,debris,etc.)before opening caps and truncating walls,and finally the graphitic structure was deteriorated.The surface oxygen content first increased with the treatment time but kept at around 8.0 wt%after 5 h.The analysis of the distribution of oxygen-containing groups revealed that phenolic hydroxyl was gradually converted to carboxyl and lactone.The carboxyl was found to play a pivotal role to reduce the over-potentials when we used the functionalized MWCNTs as the catalyst for oxygen reduction reaction(ORR).     

Synthesis and characterization of the isolated straight polymer chain inside of single-walled carbon nanotubes

In this paper, a novel molecular wire comprising an isolated straight polystyrene (PS) chain encapsulated by a single-walled carbon nantube (SWNT) was prepared. The interaction of the PS chain with the SWNTs was systematically characterized using transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and Raman spectroscopy.     

磷酸胆碱表面改性涤纶材料及抗凝血性研究

采用氧等离子体预处理涤纶材料（聚对苯二甲酸乙二醇酯,PET）表面,并通过紫外辐照在其表面接枝聚合丙烯酸,以接枝聚丙烯酸链中的羧基为反应位点,通过原子转移自由基聚合在PET表面进一步固定磷酸胆碱聚合物。经漫反射红外光谱及X射线光电子能谱分析测试表明,涤纶薄膜表面成功地固定了磷酸胆碱聚合物。经磷酸胆碱聚合物改性的涤纶表面亲水性得到改善,体外抗凝血性评价表明,固定磷酸胆碱的PET表面能够有效地抑制纤维蛋白原分子的变性,降低血小板粘附和激活。     

自组装和分散可逆的碳纳米管圆片

通过加热碳纳米管和强酸的混合物,使碳纳米管的憎水表面发生氧化.加热含经处理的碳纳米管的悬浮液,使之脱水,得到自组装的碳纳米管圆片,该圆片可直接分散.扫描电镜图显示该圆片由局部规则排列的碳纳米管构成;红外光谱和光电子谱分析表明在化学处理过程中,碳纳米管的表面产生了含氧官能团;虽然拉曼谱测出处理过程增加了缺陷,但是X射线衍射结果表明碳纳米管类似石墨的层状结构得到保留;同时研究了经处理的碳纳米管的热稳定性.这种自组装且可分散的碳纳米管圆片为研究碳纳米管结构材料和碳纳米管复合材料提供了有效途径.     

In situ synthesis of silver/chemically reduced graphene nanocomposite and its use for low temperature conductive paste

In this work, we succeeded in the synthesis of Ag/chemically reduced graphene (Ag/G) nanocomposite by a facile in situ one-pot solvothermal route. X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectra and Fourier transform infrared spectroscopy results revealed the formation of Ag and the reduction of graphite oxide to graphene during the one-pot process. Scanning electron microscopy observation indicated that spherical Ag particles with a size less than 100 nm are wrapped by graphene. The Ag/G nanocomposite was used in a low temperature conductive paste. Thermal analysis was conducted to determine the proper curing process of the Ag/G conductive paste. The Ag/G conductive paste that contains 0.6 wt% graphene exhibits low sheet resistance (22 mΩ/sq/25 µm) and good stability after cured at 150?°C for 30 min, which made us believe that the Ag/G nanocomposite is a promising candidate for conductive paste.     

Nanotrap and mass analysis of aromatic molecules by phenyl group-modified nanoparticle

To functionalize the surface of nanoparticles with phenyl groups for subsequent cross-linking with aromatic molecules by mutual interactions, we prepared functional nanoparticles (d = 3 nm) by silanization with phenyl-triethoxysilane. The nanoparticles had Fe(2)O(3) cores conjugated to phenyl groups; this was confirmed by Fourier transform infrared (FT-IR) spectroscopy and absorption spectrophotometry. The typical C-H and C-C peaks and the absorption at 240 nm, which corresponds to aromatic rings, were detected in the spectroscopic results for the phenyl group-modified nanoparticles. The nanoparticles could ionize aromatic (colchicine, reserpine, and bradykinin peptide) and nonaromatic (L-α-phosphatidylethanolamine,dioleoyl, and polyethylene glycol) molecules by nanoparticle-assisted laser desorption/ionization mass spectrometry. The nanoparticles worked as a selective trap and an ionization-assisting reagent in mass spectrometry for the aromatic molecular targets.     

In-situ preparation of binary-phase silver nanoparticles at a high Ag+ concentration

Stable and monodisperse silver nanoparticles (NPs) have been synthesized using high metal salt concentration (up to 0.735 M) through a simple but novel technique. It is based on one-step procedure that uses glycerol for reducing Ag+ in the presence of o-phenylenediamine (o-PDA) resulting the nanoparticles are in two forms (one water-soluble, the other a precipitated). The water-soluble phase contains NPs that have a bimodal size distribution (2-3 and 5-6 nm); the other comprises precipitated NPs, having a unimodal size distribution (2-3 nm). The water-soluble NPs are covalently bonded to the aromatic amine molecules to form isolated units, while the precipitated nanoparticles are embedded in the networks formed by cross-linking between COOH groups of hydroxypyruvic acid (oxidized form of glycerol) and NH2 groups of o-PDA molecules. We used transmission electron microscopy (TEM), UV-Vis spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) to characterize the silver products obtained.     

Chemical bonding of a-Ge1−xCx:H films grown by RF reactive sputtering

Amorphous hydrogenated germanium-carbon (a-Ge_1−xC_x:H) films were deposited by RF reactive sputtering pure Ge (1 1 1) target at different flow rate ratios of CH₄/(CH₄+Ar) in a discharge Ar/CH₄, and their composition and chemical bonding were investigated using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). XPS and FTIR results showed the content of germanium in the films decreased with the increase of the flow rate ratio CH₄/(Ar+CH₄), and the Ge-C, Ge-H, C-H bonds were formed in the films. The fraction of Ge-C, Ge-H, and C-H bonds was strongly dependent on the flow rate ratio. Raman results indicated that the films also contain both Ge-Ge and C-C bonding. Based on the change of the chemical bonding of a-Ge_1−xC_x:H films with the flow rate ratio CH₄/(CH₄+Ar), an optimal experimental condition for the application of infrared windows was obtained.     

Preparation and properties of novel epoxy/graphene oxide nanosheets (GON) composites functionalized with flame retardant containing phosphorus and silicon

2-(Diphenylphosphino)ethyltriethoxy silane (DPPES) was grafted onto the surface of graphene oxide nanosheets (GON) via a condensation reaction. X-ray photoelectron spectroscopy, X-ray diffractometry, Fourier transform infrared spectroscopy and Raman spectroscopy verify that DPPES did not only covalently bond to GON as a functionalization moiety, but partly restored its conjugated structure as a reducing agent. DPPES on graphene sheets oxide was observed by transmission electron microscopy, and contributed to the favorable dispersion of DPPES-GON in nonpolar toluene. Additionally, the flame retardancy and thermal stability of epoxy/DPPES-GON nanocomposites that contain various weight fractions of DPPES-GON were studied using the limiting oxygen index test, UL-94 test and by thermogravimetric analysis in nitrogen. The composites containing 10 wt% DPPES-GON can pass V-0 rating in UL-94 test. Adding 10 wt% DPPES-GON in epoxy greatly increased the char yield and LOI by 42% and 80%, respectively. Epoxy/DPPES-GON nanocomposites with phosphorus, silicon and graphene layer structures were found to exhibit much greater flame retardancy than neat epoxy. The synergistic effects among silicon, phosphorus and GON can improve the flame retardancy of epoxy resin.     

Investigation of jarosite process tailing waste by means of raman and infrared spectroscopy

The aim of this work was to identify and characterize three samples of jarosite process tailing waste in Mitrovica, Kosovo, using Raman and Fourier transform infrared (FTIR) spectroscopy. The identification is made based on the assignment of bands in the Raman and FTIR spectra. Both Raman and FTIR spectra show the fundamental stretching and bending vibration mode of SO₄^2–, OH^– and NH₄⁺ groups. The results obtained by the means of Raman and infrared spectroscopy are compared with cited reference data in order to sum the analysis of vibrational spectra.     

邻苯二甲酸氢钾在制备碱式硫酸镁纳米线过程中的机理研究

以邻苯二甲酸氢钾(KHpht)作为络合剂, 采用水热法制备出碱式硫酸镁(MOS)纳米线。通过电位滴定法分析了体系中pht ^2-与Mg ²⁺的络合作用, 并采用X射线光电子能谱(XPS)、傅里叶变换红外光谱仪(FT-IR)和透射电子显微镜(TEM)等表征手段对pht ^2-的吸附作用进行了研究。结果表明: pht ^2-与Mg ²⁺发生络合反应, 使得体系中游离的Mg ²⁺浓度大幅降低, 过饱和度也随之降低; MOS晶体表面存在着Mg-pht的化学键合作用, 由于各晶面的晶格排列方式不同, 使得pht ^2-在MOS晶体侧面吸附比例大于纵向生长面, 从而促进了高长径比MOS纳米线的生长。     

Structural changes of a pyrolytic graphite surface oxidized by electrochemical and plasma treatment

Pyrolytic graphite (PG) surfaces have been oxidized by electrochemical and oxygen plasma treatment. The oxidized PG surfaces have been studied by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared attenuated total reflection spectroscopy (FT-IR-ATR). Oxidation caused by the plasma treatment results in a small increment of the oxygen: carbon (O/C) ratio, compared to electrochemical treatment. Moreover, the increment of the O/C ratio for the plasma treated edge surface is smaller than that for the plasma treated basal surface. A steep gradient in oxygen concentration exists within the edge subsurface of PG for samples subjected to severe electrochemical treatment, as compared to those samples subjected to plasma treatment. For the electrochemical treatment, carbonyl, carboxyl, ester and lactone groups are introduced to the edge surface following relatively severe treatment. The ratio of ester and lactone groups to carboxyl groups increases with the extent of electrochemical treatment. For plasma treated samples, other types of oxygen-containing groups, which are probably keto-enol groups, are added to the edge surface, unlike during electrochemical treatment.     

退火温度对a-C:H膜结构及摩擦学性能的影响

为研究环境温度对含氢无定形碳(a-C:H)膜结构和性能的影响,将a-C:H膜在大气环境中进行高温退火处理,并借助红外光谱、拉曼光谱、X射线光电子能谱、3D表面分析仪和球盘摩擦试验机等手段对退火前后a-C:H膜的结构、组成和性能进行了系统地考察.研究发现,在较低的退火温度下(300℃),a-C:H膜结构无明显变化,而其内应力降低,摩擦学性能显著提高;在400℃和500℃下退火,膜结构发生明显变化并伴随严重氧化,同时摩擦学性能降低甚至完全失效.结果表明,退火温度的选择对a-C:H膜的结构、组成及性能具有重要影响.     

Facile synthesis of reduced graphene oxide nanosheets by a sodium diphenylamine sulfonate reduction process and its electrochemical property

We report a new method to convert graphene oxide (GO) to stable colloidal dispersion of reduced graphene oxide nanosheets (RGONS) using sodium diphenylamine sulfonate (SDAS) as a reductant, as well as itself and its redox product as the stabilizer. The as-prepared RGONS have been characterized by X-ray diffraction, Fourier transform infrared spectroscopy, UV–visible spectroscopy, thermo-gravimetric analysis, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy and Raman spectroscopy. The results indicate that the bulk of oxygen-containing functional groups from GO have been removed. Based on the cyclic voltammogram (CV) analyses, it is found that the RGONS-based material exhibits better electrochemical activity in sensing ascorbic acid than GO. The simple method provides a new efficient route for the synthesis of water-soluble RGONS on a large scale and novel composites.     

Iron-montmorillonite and zinc borate as synergistic agents in flame-retardant glass fiber reinforced polyamide 6 composites in combination with melamine polyphosphate

This paper presents a preliminary investigation on the effects of organically modified iron-montmorillonite (Fe-OMT) and zinc borate (ZnB) on thermal degradation behaviors and flame retardancy of melamine polyphosphate (MPP) flame-retarded glass fiber reinforced polyamide 6 (GFPA6). The samples were characterized using limiting oxygen index (LOI), UL-94 tests, thermogravimetric analysis (TGA), Fourier transform infrared coupled with the thermogravimetric analyzer (TG-FTIR) and Microscale Combustion Calorimeter (MCC) measurements. The residue after LOI test was also analyzed by Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) and Raman spectroscopy. A substitution of a certain fraction of MPP with ZnB or Fe-OMT can significantly improve the UL-94 rating of GFPA6/MPP composites from no rating to V0 rating, exhibiting excellent flame retardacny. Based on the investigations, different flame retardant mechanisms were proposed for the two effective flame-retardant formulations.     

Preparation and characterization of long-chain alkyl silane-functionalized graphene film

Functionalized graphene (FG) was prepared in one step by treating graphene oxide (GO) successively with hexadecyltrimethoxysilane and triethylamine. The FG sheets were subsequently assembled into a thin film by vacuum extraction filtering. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, X-ray diffraction, and Raman spectroscopy were employed to confirm the reduction and silane functionalization of GO to be simultaneously completed during the treatment. The presence of the long hexadecyl chain made the FG hydrophobic. The graphene film showed a high surface roughness, which consisted of many randomly stacked flakes, exhibiting a contact angle of up to 128.1°.     

Preparation and characterization of soluble and DBSA doped polyaniline grafted multi-walled carbon nanotubes nano-composite

Soluble and highly doped polyaniline (PANI) grafted multi-walled carbon nanotubes (MWNTs) nano-composite was synthesized by in situ oxidation polymerization, de-doping with ammonium hydroxide and doping the PANI-Emeraldine base (PANI-EB) grafted MWNTs nano-composite in N-methyl-2-pyrrolidinone (NMP) with Dodecyl benzene sulfonic acid (DBSA). Transmission electron microscope (TEM), Raman spectra, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and standard four-probe methods were employed to characterize morphology, chemical structure and electronic conductivity of the nano-composite. The results show that oxidized phenylamine groups of phenylamine groups contained MWNTs (p-MWNTs) initiate PANI polymerization on the surface of p-MWNTs. PANI coatings graft on the surface of p-MWNTs via amide bond forming homogeneous core (p-MWNTs)–shell (PANI) nano-structures. After doping PANI-EB grafted MWNTs nano-composite with DBSA, the attachment of soluble DBSA doped PANI chains on the surface of p-MWNTs via covalent bonding renders p-MWNTs compatible with polymer matrix and lead to DBSA doped PANI grafted MWNTs nano-composite soluble and stable in NMP. Owing to incorporation of p-MWNTs and chemical bridges between p-MWNTs and PANI chains, conductivity of DBSA doped PANI grafted MWNTs nano-composite at room temperature is increased by about two orders of magnitude over neat DBSA doped PANI.     

N1s Electron Binding Energies of CN_x Thin Films Grown by Magnetron Sputtering at Different Temperature

Carbon nitride thin films deposited using dc unbalanced magnetron sputtering system have been analyzed by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT1R) and Raman spectroscopy. The XPS data show that N1s binding states depend on substrate temperature Ts, in which the peak at 400.0 eV increases with Ts, whereas the peak at 398.3 eV decreases with Ts slightly On the basis of XPS, FT1R and Raman spectra, the assignment of N1s electron binding energies was made. The peak at 400.0 eV is attributed to N atoms bonded to sp2 coordinated C atoms. The peak at 398.3 eV is attributed to N atoms bonded to sp3 coordinated C atoms as well as N C bonds.