Modification of hydrophobic/hydrophilic properties of Vulcan XC72 carbon powder by grafting of trifluoromethylphenyl and phenylsulfonic acid groups

Carbon supports (glassy carbon and Vulcan XC72 powder) were modified by electrochemical and spontaneous grafting of phenylsulfonic acid (PSA) or trifluoromethylphenyl (TFMP) groups via diazonium ion reduction. The effectiveness of the grafting was confirmed electrochemically, by XPS measurements and elemental analyses. The hydrophobic or hydrophilic character of carbon surfaces was evidenced by measuring the contact angles of drops of different liquids (water, ethylene glycol and glycerol) in heptane. The surface energy was calculated and it was found, for example, that spontaneous grafting of a glassy carbon surface by PSA groups led to an increase by a factor 20 of the surface energy compared with an unmodified glassy carbon surface. The study of the grafting of such groups on XC72 carbon powder indicated that a very low grafting ratio (in wt%) led to a significant change in the macroscopic properties of the powder. Thermogravimetric analysis coupled with mass spectroscopy measurements (TGA-MS) showed that these grafted layers were thermally stable even in the presence of dispersed platinum nanoparticles. It was shown by cyclic voltammetry that the carbon substrate modification did not affect the electrochemical behavior of platinum catalyst, since the same active surface area was determined on Pt-XC72, Pt-PSA-XC72 and Pt-TFMP-XC72 catalysts.     

Electrochemical characterization of adsorbed bilirubin oxidase on Vulcan XC 72R for the biocathode preparation in a glucose/O2 biofuel cell

A new biocathode was built and tested. It consisted of bilirubin oxidase adsorbed on Vulcan XC 72 R and immobilized into a Nafion^® matrix. The possibility of direct electron transfer between bilirubin oxidase and Vulcan XC 72 R was also demonstrated. The kinetics on biocathode were enhanced by including 2,2′-azinobis-3-ethylbenzothiazoline-5-sulfonic acid in the catalytic film. A first order reaction rate was observed for oxygen concentrations lower than 22%. A complete kinetic investigation of the system was shown. A biofuel cell test performed with this biocathode and Au₇₀Pt₃₀ nanoparticles as anode catalyst permitted to reach a power density of 170 μW cm⁻² at a cell voltage of 0.6 V, which is superior to what can be obtained with the concentric design.     

Thermally Pretreated 46% Pt/Vulcan XC72: Characterisation by TGA/DSC/TEM and Cyclic Voltammetry

We report a study of thermal stability and impact of thermal pretreatment procedures for 46% Pt/Vulcan XC72 (Tanaka) fuel cell catalyst. Stability in air and in inert gas (nitrogen, argon, helium) has been investigated by thermal gravimetric analysis (TGA), TGA‐mass spectrometry (TGA‐MS) and differential scanning calorimetry (DSC). Two distinct low temperature mass loss processes (100–200 and 285–300 °C) were observed, each exhibiting unique pretreatment temperature dependencies. TGA‐MS data in helium show fragment ions that suggest the thermal degradation processes are associated with decomposition of materials such as processing aids. Transmission electron microscopy (TEM) reveals a modest increase in average Pt nanoparticle size upon thermal pretreatment. After a pretreatment protocol based on TEM and thermal characterisation (300 °C/15 min, N₂), the electrochemically active surface area did not increase. At the kinetically controlled potential region (E >0.8 V) there was a small drop in current density for treated 46% Pt/C in comparison with as‐received catalyst. The slowing in ORR kinetics is significant. Apparently, the removal of organic components, which would improve mass transport, is negated by increased nanoparticle size.     

Fluorination of Vulcan XC-72R for cathodic microporous layer of passive micro direct methanol fuel cell

The effect of adding fluorinated Vulcan XC-72R into the microporous layer (MPL) of the cathode in a passive micro direct methanol fuel cell (μDMFC) has been investigated. Upon fluorination with fluoro-alkyl silane (FAS), the surface of XC-72R becomes more hydrophobic, as indicated by contact angle measurements. The performance of the membrane electrode assembly (MEA) is improved significantly when fluorinated Vulcan XC-72R is used in MPL of the cathode. The maximum power density of a passive μDMFC reached ca. 36.2 mW cm⁻² at room temperature, and the constant-current discharging test exhibits enhanced stability. Also observed is a decreased water transport coefficient (α), calculated from discharging test, attributable to the greater hydrophobicity resulting in higher liquid pressure on the cathode, which forces more water to flow back to the anode. Additionally, A.C. impedance analysis indicates that the improvement in performance results from the decrease of charge transfer resistance of the cathodic reaction.     

Kinetics and mechanism of oxygen reduction reaction at CoPd system synthesized on XC72

Studies are presented of the kinetics and mechanism of oxygen electroreduction reaction on CoPd catalysts synthesized on carbon black XC72. As shown both in model conditions and in the tests within the cathodes of hydrogen-oxygen fuel cells with proton conducting electrolyte, CoPd/C system features a higher activity, as compared to Co/C. The highest activity in the oxygen reduction reaction is demonstrated by the catalysts with the Pd:Co atomic ratio being 7:3 and 4:1. The structural studies (XPS and XRD, and also the data of CO desorption measurements) evidence the CoPd alloy formation, which is reflected in the negative shift of the bonding energy maximum as compared to Pd/C and in the appearance of the additional CO desorption maximums on the voltammograms. It is found by means of structural research that CoPd alloy is formed in the course of the catalyst synthesis which features a higher catalytic activity of the binary systems. Besides, CoPd/C catalyst is more stable in respect to corrosion than Pd supported on carbon black. The measurements on the rotating disc electrode and rotating ring-disc electrode evidence that CoPd/C system provides the predominant oxygen reduction to water in the practically important range of potentials (E > 0.7 V). The proximity of kinetic parameters of the oxygen reduction reaction on CoPd/C and Pt/C catalysts points to the similar reaction mechanism. The slow step of the reaction is the addition of the first electron to the adsorbed and previously protonated O₂ molecule. The assumptions are offered about the reasons causing the higher activity and selectivity of the binary catalyst towards oxygen reduction to water, as compared to Co/C. The studies of the most active catalysts within the fuel cell cathodes are performed.     

重氮化-水解法制备间甲酚的工艺研究

间甲苯胺经重氮化-水解制备了间甲酚。采用正交实验和单因素实验详细研究了重氮化工序和水解工序的各工艺参数(如酸的浓度、亚硝酸钠滴加速度、重氮盐滴加速度等)对间甲酚收率的影响,得出了最佳工艺条件。在最佳工艺条件下,间甲酚收率为84.04%,纯度可达98%以上。     

Polypropylene nanocomposites produced by in situ grafting of n‐butyl acrylate

Nanocomposites of polypropylene and organophilic clay are produced by in situ functionalization of PP with n‐butyl acrylate (BA) during melt mixing. Three strategies for incorporating materials into the mixer are analyzed and the effect of clay concentration is evaluated. The materials are examined by FTIR spectroscopy, X‐ray diffraction, scanning electron microscopy, differential scanning calorimetry, thermogravimetry, and rotational rheometry. The results show that all composites prepared in the presence of BA have similar intercalated clay structure, and that the largest degree of exfoliation is obtained using the sequential mixing technique. This method, which consists in adding the initiator and functionalizing agent to the molten polypropylene followed by the addition of the clay, also produces the largest reduction in molecular weight of the polymer and the largest increase of the elastic modulus. All polymers show similar crystallization and degradation processes. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42585.     

邻甲苯胺重氮化-水解制备邻甲酚工艺改进

以邻甲苯胺为原料,采用重氮化-水解法制备高纯度邻甲酚,通过正交实验和单因素实验对重氮化反应工艺条件进行了优化。实验结果表明,该反应的优化条件为：重氮化n（硫酸）：n（邻甲苯胺）=3．4：1．0,硫酸溶液质量分数为3％,亚硝酸钠溶液的质量分数为35％,加料速度为0．8mL／min,重氮液的滴加速度为20mL／min。此优化条件下,邻甲酚收率可达86．2％,纯度99．5％。     

高效液相色谱法测定焦磷酸三聚氰胺-焦磷酸哌嗪混合阻燃剂中的三聚氰胺

通过调节pH溶解样品,以离子对缓冲液及乙腈的混合液作为流动相,C18色谱柱作为分析柱,VWD可变波长紫外检测器作为检测器,应用高效液相色谱仪对焦磷酸三聚氰胺-焦磷酸哌嗪混合阻燃剂中的三聚氰胺含量进行了测定。结果显示,样品溶液中三聚氰胺质量浓度在0～80μg/mL范围内线性良好。重复测定相对标准偏差在1.2%以内,加标回收率在98.3%～104.0%。     

Preparation of polyaniline/vermiculite clay nanocomposites by in situ chemical oxidative grafting polymerization

BACKGROUND: Recently, conducting polymers have attracted much attention, since they have interesting physical properties and many potential applications, such as in conductive coating charge storage. Hence the synthesis of conducting polymer nanocomposites is also an area of increasing research activity. RESULTS: Vermiculites (VMTs) were successfully delaminated using an acid treatment. Polyaniline (PANI)/VMT nanocomposites were prepared by in situ chemical oxidative grafting polymerization. CONCLUSION: The chemical grafting of PANI/VMTs was confirmed by Fourier transform infrared and UV‐visible spectroscopy. The percentage of grafted PANI was 142.7 wt% as a mass ratio of the grafting PANI and charged nano‐VMTs, investigated using thermogravimetric analysis. In addition, characteristic agglomerate morphology of PANI was observed in the composites using scanning electron microscopy. Thermal analyses indicated that the introduction of VMT nanosheets had a beneficial effect on the thermal stability of PANI. The electrical conductivity of the nanocomposites was 3.9 × 10^?3 S cm^?1, a value typical for semiconductors. Copyright © 2009 Society of Chemical Industry     

Preparation and characterization of flame‐retardant melamine cyanurate/polyamide 6 nanocomposites by in situ polymerization

This article focuses on an improved method, i.e., improved in situ polymerization of ε‐caprolactam in the presence of melamine derivatives to prepare flame‐retardant melamine cyanurate/polyamide 6 (MCA/PA6) nanocomposites. The chemical structures of these synthetic flame retardant composites are characterized by Fourier‐transform infrared spectroscopy and X‐ray diffraction. Morphologies, mechanical properties, and thermal properties also are investigated by the use of transmission electron microscopy, mechanical testing apparatus, differential scanning calorimetry, and thermogravimetric analysis, respectively. Through transmission electron microscopy photographs, it can be found that the in situ‐formed MCA nanoparticles with diametric size of less than 50 nm are nanoscaled, highly uniformly dispersed in the PA6 matrix. These nanocomposites, which have good mechanical properties, can reach UL‐94 V‐0 rating at 1.6‐mm thickness even at a relatively low MCA loading level. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

饲料中三聚氰胺残留量高效液相色谱测定的研究

建立了饲料中三聚氰胺残留量的高效液相色谱分析方法,样品经反相柱分离后采用波长为245nm的紫外检测器进行检测,该方法具有准确、快速、高效的特点.三聚氰胺在1.0μg/～50μg/mL浓度范围内线性良好,相关系数为0.9996,回收率范围在94.75%～102.9%,相对标准偏差为2.92%～5.38%.     

A kinetic and rheometric investigation of hexamethylol melamine derivative on the cure of natural rubber compounds

Hexamethylol melamine (HMM) was characterized by Fourier transform infrared (FTIR) spectroscopy. The optimum dose of HMM in the presence of a sulfur accelerator in a natural rubber (NR)-filled compound was determined. The cure rate and kinetics of crosslink formation indicate that HMM enhances the first-order rate of vulcanization in an NR compound. The results reveal good mechanical properties of an HMM-based NR carbon black-filled vulcanizate. © 1997 John Wiley & Sons, Inc.     

In situ grafting MPEG on the surface of cell-loaded microcapsules for protein repellency

The protein repelled alginate-graft-BAT/chitosan/MPEG-norbornene (A_BCP_N) hydrogel microcapsules were achieved by copper-free click reaction between azides from BAT and alkylenes from norbornene. The MPEG modified polyelectrolyte microcapsules showed significant resistance to immune protein adsorption and good biocompatibility in vivo. Moreover, the mild reaction condition made it feasible that the microcapsules could be formed and modified in situ even when live cells were encapsulated, and precluded the damage cause by other violent modifications methods to transplanted cells or tissues.     

LC-MS/MS法测定乳制品中三聚氰胺

采用LC-MS/MS法测定乳制品中的三聚氰胺,具有灵敏度高、精确度好的优点.检测结果表明,在0.005 μg/mL～0.5 μg/mL,三聚氰胺质量浓度与峰面积呈良好的线性关系,相关系数r>0.999 8,回收率>85%,变异系数RSD<1.50%.     

Dyeing of chrome tanned collagen modified by in situ grafting with 2‐EHA and MAC

The aim of this study deals with the modification of the chrome tanned collagen (leather) by in situ grafting with 2‐ethyl hexyl acrylate (2‐EHA) and methacrylic acid (MAC) to improve its dyeability using Amecid Floxine 2GN (C.I. Acid Red 1) and Remazol Black B (C.I. Reactive Black 5). The optimum condition of in situ grafting has been evaluated. FTIR spectra of the ungrafted and the in situ grafted chrome tanned collagen showed that the corresponding band of the acrylate carbonyl ester occurs at 1730–1735 cm^?1 when compared with the ungrafted ones. The colorimetric data of the in situ grafted and dyed samples exhibited improvement in color shade, dye bath exhaustion, wash and light fastness relative to the ungrafted and dyed ones. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 174–179, 2006     

三聚氰胺共聚改性脲醛树脂固化性能研究

采用M(三聚氰胺)对低n[F(甲醛)]∶n[U(尿素)]比例的UF(脲醛树脂)进行改性,制备了MUF(M共聚改性UF);通过差示扫描量热(DSC)法表征了M的投料时间和比例对UF固化特性的影响,并对MUF的理化性能进行了评价。研究结果表明:随着M掺量的不断增加,MUF胶粘剂的固含量呈增长趋势,固化速率减慢,MUF中游离F含量显著降低。M投料时间对MUF的游离F含量、固含量和固化速率的影响不同,M在缩聚前期投料时,MUF的固含量较高,固化速率基本不变,游离F含量随M掺量增加而逐渐降低;当M在缩聚前期加入且w(M)=3%~4%(相对于U总质量而言)时,MUF中的羟甲基含量相对最低、MUF胶粘剂的综合性能相对最佳。     

High sensitive simultaneous determination of catechol and hydroquinone at mesoporous carbon CMK-3 electrode in comparison with multi-walled carbon nanotubes and Vulcan XC-72 carbon electrodes

The simultaneous voltammetric determination of catechol (CC) and hydroquinone (HQ) has been achieved at a mesoporous carbon CMK-3 modified electrode in phosphate buffer solution (pH 7.0). At the electrode both CC and HQ can cause a pair of quasi-reversible and well-defined redox peaks and their peak potential difference increases. In comparison with multi-walled carbon nanotubes (MWCNTs) and Vulcan XC-72 carbon modified electrodes the CMK-3 modified electrode shows larger peak currents and higher adsorbed amounts for the two dihydroxybenzene isomers. This is related to the higher specific surface area of CMK-3. Under the optimized conditions, the linear concentration ranges for CC and HQ are 5 × 10⁻⁷ to 3.5 × 10⁻⁵ M and 1 × 10⁻⁶ to 3 × 10⁻⁵ M, respectively. In the presence of 5 μM isomer, the linear concentration range of CC (or HQ) is 5 × 10⁻⁷ to 2.5 × 10⁻⁵ M (or 5 × 10⁻⁷ to 2.0 × 10⁻⁵ M). The sensitivity for CC or HQ is 41 A M⁻¹ cm⁻² or 52 A M⁻¹ cm⁻², which is close to that without isomer. The detection limits (S/N = 3) for CC and HQ are 1 × 10⁻⁷ M after preconcentration on open circuit for 240 s.     

Covalent attachment of pyridine-type molecules to glassy carbon surfaces by electrochemical reduction of in situ generated diazonium salts. Formation of ruthenium complexes on ligand-modified surfaces

In this study, pyridine, quinoline and phenanthroline molecules were covalently bonded to glassy carbon (GC) electrode surfaces for the first time using the diazonium modification method. Then, the complexation ability of the modified films with ruthenium metal cations was investigated. The derivatization of GC surfaces with heteroaromatic molecules was achieved by electrochemical reduction of the corresponding in situ generated diazonium salts. X-ray photoelectron spectroscopy (XPS) was used to confirm the attachment of heteroaromatic molecules to the GC surfaces and to determine the surface concentration of the films. The barrier properties of the modified GC electrodes were studied in the presence of redox probes such as Fe(CN)₆³⁻ and Ru(NH₃)₆³⁺ by cyclic voltammetry. Additionally, the presence of the resulting organometallic films on the surfaces was verified by XPS after the chemical transformation of the characterized ligand films to the ruthenium complex films. The electrochemical behavior of these films in acetonitrile solution was investigated using voltammetric methods, and the surface coverage of the organometallic films was determined from the reversible metal-based Ru(II)/Ru(III) oxidation waves.     

共价偶联法在玻片表面固定适配体的研究

以玻片为载体,采用共价偶联法对适配体进行了固定,考察了硅烷化试剂浓度、硅烷化反应温度和时间、适配体与玻片反应时间和温度、适配体浓度和长度对适配体固定率的影响,确定了适配体固定于玻片的最佳条件为:将浓度为1.59×10-5 mol·L-1的16个碱基的适配体涂抹在经4×10-3 mol·L-1硅烷化试剂45℃下处理30min的玻片表面上,在45℃下固定化反应120min,适配体固定率达62.05%。在此基础上初步探讨了固定有特异性适配体的玻片对水溶液中Hg2+的吸附,吸附汞的效率达49.84%。此方法操作简便、成本低廉,且能有效固定未经修饰的适配体,为利用适配体对水中重金属进行富集和去除的研究提供了参考。