Characterization of oxygen containing functional groups on carbon materials with oxygen K-edge X-ray absorption near edge structure spectroscopy

Surface functional groups on carbon materials are critical to their surface properties and related applications. Many characterization techniques have been used to identify and quantify the surface functional groups, but none is completely satisfactory especially for quantification. In this work, we used oxygen K-edge X-ray absorption near edge structure (XANES) spectroscopy to identify and quantify the oxygen containing surface functional groups on carbon materials. XANES spectra were collected in fluorescence yield mode to minimize charging effect due to poor sample conductivity which can potentially distort XANES spectra. The surface functional groups are grouped into three types, namely carboxyl-type, carbonyl-type, and hydroxyl-type. XANES spectra of the same type are very similar while spectra of different types are significantly different. Two activated carbon samples were analyzed by XANES. The total oxygen contents of the samples were estimated from the edge step of their XANES spectra, and the identity and abundance of different functional groups were determined by fitting of the sample XANES spectrum to a linear combination of spectra of the reference compounds. It is concluded that oxygen K-edge XANES spectroscopy is a reliable characterization technique for the identification and quantification of surface functional groups on carbon materials.     

Curing reaction and product properties of polysulfones terminated with active functional groups

The curing processes of maleimide-terminated polyether sulfone oligomers (M_n from 1100 to 3000) and ethynyl-terminated polysulfone prepolymers (M_n from 2600 to 12000) were investigated by means of DSC. The initial temperature of cure reaction is increased, and the apparent activation energy E_a of cure reaction is decreased as the M_n of the uncured prepolymer increases. On the basis of the T_g changes during the curing process, the kinetics of cure is proposed to be similar to a stepwise reaction, although the curing reaction is believed to proceed via a free radical chain mechanism. In this proposed reaction some initial reaction products with many branches and one remaining active functional group are formed first. The more these products occur, the more likely they can interreact to form a network. During the curing process the mobility of the active end group is restricted by the rigid polysulfone chain. Therefore, the reaction is mainly controlled by the movement of polymer, i.e., by the kinetics of diffusion. Films of these cured polymers were made by casting from solution. Their β relaxation peaks at low temperatures were examined by dielectric and dynamic mechanical measurements. The films made of the prepolymer with M_n > 3000 are flexible and foldable.     

Detection of low concentration oxygen containing functional groups on activated carbon fiber surfaces through fluorescent labeling

Covalent fluorescent labeling of surface species (FLOSS) was used to detect relatively low concentrations of surface functional groups (OH, COOH and CHO) on activated carbon fiber surfaces. The chromophores were attached to the surface through a reaction specific to each type of surface functional group. FLOSS indicated the presence of 8.7 × 10¹¹ COOH groups/cm² and 1.3 × 10¹² CHO groups/cm² on the ACF 25 fiber surface. Neither the infrared spectrum nor the X-ray photoelectron spectrum showed evidence of the existence of those low concentration groups. The concentration of OH groups on the fiber surface was lower than the detection limit (∼10¹⁰/cm²) of FLOSS under the present conditions. The FLOSS results for CHO and COOH groups were compared with the concentrations determined by Boehm titration (3.11 × 10¹³/cm² for CHO and 1.05 × 10¹³/cm² for COOH). The limited accessibility of the ACF surface to relatively large chromophores is one of the main reasons for the discrepancy between these two methods. FLOSS detects only exposed functional groups as opposed to functional groups hidden in small pores. This apparent limitation, however, highlights the surface sensitivity and specificity of FLOSS technique.     

Dendritic macromolecules containing several types of functional groups

Dendritic macromolecules containing several types of functional groups were successfully synthesized through divergent method. Poly(ethylene glycol) was functionalized using cyanuric chloride and it was reacted with p‐toluidine at room temperature and a macromolecule containing chloride and methyl functional groups (PEG‐Cl₂‐Me₂) was obtained. Substitution of chloride functional groups of PEG‐Cl₂‐Me₂ by hydroxyl functional groups led to a macromolecule containing methyl and hydroxyl functional groups (PEG‐Me₂‐OH₄). Hydroxyl functional groups of PEG‐Me₂‐OH₄ were reacted with cyanuric chloride and PEG‐Me₂‐Cl₈ was obtained. Finally, PEG‐Me₂‐Cl₈ was reacted with p‐aminophenol at room temperature and a macromolecule containing methyl, hydroxyl, and chloride functional groups (PEG‐Me₂‐(PhOH)₄‐Cl₄) was obtained. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

苯环为瑞基官能团的疏水型聚酰胺胺树状大分子的合成及性质

以乙二胺为中心核,丙烯酸甲酯为支化单体,苯甲醛为端基官能团,设计合成了一种疏水型的聚酰胺胺树状大分子.随着分子代数的增加,树状大分子在最大吸收波长处的吸收强度增加,而且最大吸收波长出现了红移现象,从248 nm红移到260 nm;树状大分子溶液的荧光强度随着树状大分子的代数增加而增加,同时荧光发射峰从454 nm蓝移到442 nm;产品能溶解于三氯甲烷和二氯甲烷,不溶于水、环己烷和苯.     

Photocatalytic functional cotton fabrics containing benzophenone chromophoric groups

In preparation of self‐decontamination clothing materials in high reactivities against toxic agents, photoactive benzophenone chromophoric groups were incorporated into cotton fabrics. The cotton fabrics were treated by using 4‐hydroxybenzophenone as a reagent, 1,2,3,4,‐butanetetra carboxylic acid (BTCA) as a crosslinker, and sodium hypophosphite as a catalyst. The fabric treatment was conducted by a pad‐dry‐cure method. The benzophenone chromophoric group incorporated cotton fabrics were characterized by FTIR, SEM, TGA, and so on. The results confirmed the expected structures of the benzophenone chromophoric group modified and BTCA crosslinked cotton fabrics. The treated cotton fabrics demonstrated radical reactivities and antibacterial activity under UV irradiation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Porous polymeric antimicrobial resin containing N-halamine functional groups

An effective and easily recovered porous divinylbenzene (DVB) cross-linked antimicrobial polymeric resin containing N-halamine functional groups, poly (styrene-co-N-(t-Bu)-N-chloro-acryl amide) (PSA-N-Cl) resin, has been synthesized by a suspension copolymerization of styrene and acrylic acid and DVB, an amination with tert-butylamine and triethylenediamine (TEDA), and then a facile chlorination in diluted NaOCl solution. The as-prepared porous DVB cross-linked PSA-N-Cl resin was characterized by Brunauer–Emmett–Teller (BET) analysis, field emission scanning electron microscopy (FE-SEM), Fourier Transform infrared spectroscopy (FTIR) and X-ray photoelectron spectra (XPS). BET analysis indicated that PSA-N-Cl resin has a very large surface area (124.9 m²/g) which is favorable for the quick water disinfection. Antibacterial tests showed that the as-prepared PSA-N-Cl resin possesses powerful antibacterial efficacies against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The as-prepared PSA-N-Cl resin was capable of about 7.95-log and 7.81-log reductions of E. coli and S. aureus within 1 and 3 min of contact times, respectively. Also, the regenerability and preliminary storage stability of the as-prepared PSA-N-Cl resin were investigated.     

Synthesis and properties of polysiloxanes containing mixed functional groups

An effective synthesis of polysiloxanes containing mixed functional groups was carried out using consecutive hydrosilylation of two different olefins. With the functionalization of polysiloxanes, we sought to obtain derivatives containing fluoroalkyl groups (with hydrophobic properties) and reactive groups capable of attaching a polysiloxane to the surface. Glycidyl and trimethoxysilyl groups were chosen for the study. All of the obtained derivatives were isolated and spectroscopically characterized. In the next stage of the study, glass plates were modified with functionalized polysiloxanes, both alone and with added silica sol, and their hydrophobic properties were determined by measuring contact angles. From the results, we determined the effect of functionalized polysiloxane structure on the hydrophobic properties of polysiloxane-modified surfaces.     

Modification of the adsorption properties of high surface area graphites by oxygen functional groups

The role of the concentration of oxygen functional groups on the surface of commercial high surface area graphite has been studied in this work. For this purpose, two samples of the parent HSAG have been both oxidized with aqueous HNO₃ solution and pyrolysed at 900 °C under an He flow, in order to remove surface oxygen groups. TPD results, in agreement with XPS experiments, reveal the existence of oxygen groups on the surface of the parent HSAG, whose concentration increases substantially after the oxidative treatment, whereas they disappear after the thermal treatment. The adsorption of different alkanes, aromatics and chlorohydrocarbons on the three samples were compared. Adsorption capacities were derived from the adsorption isotherms, whereas thermodynamic properties have been determined from chromatographic retention data. Both the capacity and the strength of adsorption decrease after the oxidative treatment of the graphites. For n-alkanes and cyclic compounds, it was demonstrated that the presence of oxygen surface groups affects their interaction in lower extension. In the adsorption of aromatics and double-bonded compounds, the influence of surface functionalization is more pronounced, since the removal of electrons from the π-electron system of the basal planes, weaken these forces.     

煤燃烧过程中碳、氧官能团演化行为

采用X射线光电子能谱（XPS）系统研究燃烧过程中准格尔褐煤及其煤焦颗粒表面中碳、氧的存在形态及演化过程.研究结果表明，准格尔褐煤颗粒表面含碳官能团中石墨化碳含量非常低，但同时具有一定含量的双键碳;含氧官能团中无机氧含量较低，有机氧含量相对较高.随着燃烧的进行，颗粒表面碳、氧官能团呈现不同的变化趋势.     

Glycerol-derived solvents containing two or three distinct functional groups enabled by trifluoroethyl glycidyl ether

Conversion of epichlorohydrin to glycidyl ethers creates versatile precursors that can be transformed into a variety of molecular species with glycerol skeletons, enabling the design of molecules with highly tailored functionalities. The synthesis of 2,2,2-trifluoroethyl glycidyl ether (TFGE, IUPAC name: 2-[(2,2,2-trifluoroethoxy)methyl]oxirane, CAS# 1535-91-7) was optimized to provide high yield/selectivity and good “green metrics.” TFGE was then used as a platform molecule in the synthesis of asymmetric glycerol 1,3-diether-2-alcohol derivatives, which were subsequently transformed to 1,2,3-triethers or 1,3-diether-2-ketones. The density, viscosity, and CO₂ solubility of each molecule were measured and compared with those of other glycerol-derived compounds as well as compounds with similar functional groups. Furthermore, quantum chemical calculations were performed to understand the structure–property–performance relationships of these molecules for CO₂ absorption. Based on the results in this work, we foresee that TFGE (and similar glycidyl ethers) would offer great flexibility in molecular design of green solvents and precursors to more complex compounds.     

COREX系统用煤燃烧过程中含氧官能团的转变研究

COREX是现有熔融还原方法中的主要工艺流程,该系统对煤质量有严格的要求。我们对系统运行中所涉及的主要煤种大同煤和兴隆庄煤燃烧行为进行深入研究。利用同步热分析仪（TG．DSC）研究高温条件下煤的热分解行为;通过电子扫描显微镜（SEM）观察了煤的微观结构,进行了岩相分析;通过傅里叶红外光谱仪（Frm）和湿式化学分析法,定性及定量的研究了煤中含氧官能团,尤其是热解过程中有机含氧官能基团的组分、数量、化学结构和转化机理。全面评价煤炭的质量,为系统稳定运行选用煤种,提高块煤利用率提供了理论基础。     

Viscoelastic behavior of hydroxyl terminated polybutadiene containing glycerin

Hydroxyl terminated polybutadiene (HTPB) is widely used as a propellant binder. A plasticizer is usually added to improve the processing properties, the mechanical properties, and the burning characteristics of the propellant. Glycerin was found to be an effective additive to improve these properties. The glycerin/HTPB blend was hard enough to act as a binder for the composite propellant when the glycerin/HTPB mole ratio was less than 10. Only a small quantity of glycerin was incorporated into the network structure of the cured HTPB. Most of the added glycerin physically entered the voids in the network of the cured HTPB. Addition of a small quantity of glycerin (mole ratio less than 0.1) significantly altered the network density and the viscoelastic properties of the blends. The properties were only slightly dependent on the amount of the added glycerin in the mole ratio range of 0.1–10. The dangling ends were formed in the HTPB network by the addition of glycerin and the network structure was loosened, thereby enhancing the mobility of the chain segment. The viscoelastic properties of the blends followed the time‐temperature superposition principle, and the properties were estimated accurately by the Williams‐Landel‐Ferry approach. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Detecting and quantifying oxygen functional groups on graphite nanofibers by fluorescence labeling of surface species

The ability to quantify functional groups on graphitic carbon nanofiber (GCNF) surfaces and to covalently attach ligands chemoselectively will aid in the development of functionalized GCNFs and potentially other carbon nanomaterials for applications in nanotechnology. Herein, we report the identification and quantification of functional groups on the surface of GCNFs using fluorescence labeling of surface species (FLOSS). Using reactions that are selective for specific functional groups and fluorescent dyes containing the dansyl group, surface aldehyde/ketone, carboxyl, and hydroxyl groups were identified and quantified in their total and relative amounts by FLOSS. Oxygen-containing functionality that was detected by FLOSS on nitric acid-oxidized GCNFs totaled approximately 2.5% of surface carbon, present as 0.9% aldehyde/ketone, 1.2% carboxyl groups on average, and 0.4% hydroxyl groups. The amounts of oxygen-containing functional groups on as-produced and demineralized GCNFs were much lower, amounting to no more than 0.05% of aldehyde/ketone groups on demineralized GCNFs and 0.3% of these groups on as-produced fibers. The FLOSS method has revealed information about the fiber surface that is not accessible by other methods, while also providing insight into the chemical reactivities of functional groups that can be used as sites for the attachment of ligands to give covalently functionalized materials.     

An FTIR study of australian coals: Characterization of oxygen functional groups

The FTIR data in the oxygen-hydrogen stretching and carbonyl stretching regions for 28 Australian coals and their liquefaction products have been investigated. It was found that for the higher rank coals and asphaltenes, the absorbance at 3200 cm⁻¹ correlates with the atomic O/C values and the acidic oxygen contents as measured by a non-aqueous titration technique. The technique of least-squares curve fitting was applied to deconvolute the carbonyl stretching region. The results showed that for the higher rank coals there were relationships between the amount of carbonyl functional groups present, as measured from the band areas, and the coal O/C values. Most brown coals with a high oxygen content (O/C > 0.26) contain less guest material and have a lower concentration of carbonyl groups both as acids and esters than brown coals with a lower oxygen content. They have a higher non-acidic oxygen content, principally as ethers.     

Importance of activated carbon's oxygen surface functional groups on elemental mercury adsorption

The effect of varying physical and chemical properties of activated carbons on adsorption of elemental mercury (Hg⁰) was studied by treating two activated carbons to modify their surface functional groups and pore structures. Heat treatment (1200 K) in nitrogen (N₂), air oxidation (693 K), and nitric acid (6N HNO₃) treatment of two activated carbons (BPL, WPL) were conducted to vary their surface oxygen functional groups. Adsorption experiments of Hg⁰ by the activated carbons were conducted using a fixed-bed reactor at a temperature of 398 K and under N₂ atmosphere. The pore structures of the samples were characterized by N₂ and carbon dioxide (CO₂) adsorption. Temperature-programmed desorption (TPD) and base-acid titration experiments were conducted to determine the chemical characteristics of the carbon samples. Characterization of the physical and chemical properties of activated carbons in relation to their Hg⁰ adsorption capacity provides important mechanistic information on Hg⁰ adsorption. Results suggest that oxygen surface complexes, possibly lactone and carbonyl groups, are the active sites for Hg⁰ capture. The carbons that have a lower carbon monoxide (CO)/CO₂ ratio and a low phenol group concentration tend to have a higher Hg⁰ adsorption capacity, suggesting that phenol groups may inhibit Hg⁰ adsorption. The high Hg⁰ adsorption capacity of a carbon sample is also found to be associated with a low ratio of the phenol/carbonyl groups. A possible Hg⁰ adsorption mechanism, which is likely to involve an electron transfer process during Hg⁰ adsorption in which the carbon surfaces may act as an electrode for Hg⁰ oxidation, is also discussed.     

Electrochemical oxygen reduction activity of intermediate onion-like carbon produced by the thermal transformation of nanodiamond

Onion-like carbon (OLC) is known to form as an intermediate structure when nanodiamond (ND) is heat treated at 1100–1500 °C. In this letter, we report on the electrochemical activity of its oxygen reduction reaction (ORR) when prepared at temperatures from 1000 to 2000 °C. The ORR activity is found to exhibit excellent correlation with the degree of defects, with OLC prepared at 1400 °C found to have the highest activity. This is attributed to the formation of curved graphitic layers containing edges during ND-OLC transformation, which function as active sites for the adsorption and subsequent reduction of oxygen.     

Differential adsorption of heavy metal ions by cotton stalk cation‐exchangers containing multiple functional groups

Esterification of cotton stalks with chlorosulfonic acid, phosphorus oxychloride, and their mixture was carried out with the aim to prepare cation exchangers for the removal of heavy metal ions from industrial waste water. Elemental analysis, Fourier transform infrared (FTIR) analysis, and sodium ions binding capacity were used to prove the occurrence of the esterification. The efficiency of the prepared cation exchangers to remove some heavy metal ions (strontium, arsenic, copper, and nickel) at different metal ion concentration, pH, contact time, and temperature was studied. The results showed that cotton stalks that contain both phosphate and sulfonate groups (phosphosulfonated cotton stalks) showed higher adsorption of the different heavy metal ions than cotton stalks containing sulfonate or phosphate on a separate basis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4124–4132, 2006     

Thermal stabilities of end groups in hydroxyalkyl terminated polydimethylsiloxane oligomers

Summary Thermal stabilities of α,ω-hydroxypropyl, α,ω-hydroxybutyl, α,ω-2-hydroxypentyl and α,ω-hydroxyhexyl terminated polydimethylsiloxane (PDMS) oligomers were studied. Hydroxypropyl and hydroxybutyl terminated polydimethylsiloxane oligomers showed degradation upon heating, through the loss of functional end groups as determined by FT-IR spectroscopy and gel permeation chromatography. α,ω-Hydroxyhexyl and α,ω-2-hydroxypentyl terminated polydimethylsiloxane oligomers were stable under similar conditions. Instability of the end groups is due to the back biting of the terminal silicon in the PDMS by the primary hydroxyl oxygen, leading to the formation of 5 and 6 membered, stable, heterocylic compounds. Loss of end groups also resulted in a dramatic increase in the molecular weights of the oligomers produced, as determined by gel permeation chromatography. Received: 19 January 1998/Revised version: 27 February 1998/Accepted: 5 March 1998