基于多壁碳纳米管修饰电极的磺胺的电化学检测

运用线性扫描伏安法(LSV)研究了磺胺(SA)在多壁碳纳米管修饰电极(MWNTs/GCE)上的电化学行为,探讨并确定了修饰体积和浓度、支持基质种类、最佳pH值、富集电位和时间等磺胺的最佳检测条件。结果表明,在pH=8.0的Na2HPO4-NaH2PO4缓冲体系中,磺胺在多壁碳纳米管修饰电极上检测到一个不可逆的氧化峰,且在1.0×10-5².0×10-4mol/L浓度范围内,磺胺氧化峰电流与其浓度呈现良好的线性关系,线性回归方程为Ip(μA)=0.493 6×C(μmol/L)+9.984 1,相关系数为R=0.996 3,检测下限为8.0×10-6mol/L,平行测定的相对误差(RSD)小于1.463%(n=8),样品平均加标回收率为99.21%2.0×10-4mol/L浓度范围内,磺胺氧化峰电流与其浓度呈现良好的线性关系,线性回归方程为Ip(μA)=0.493 6×C(μmol/L)+9.984 1,相关系数为R=0.996 3,检测下限为8.0×10-6mol/L,平行测定的相对误差(RSD)小于1.463%(n=8),样品平均加标回收率为99.21%¹00.93%。     

聚甲基红膜修饰电极电化学检测盐酸环丙沙星

采用循环伏安法电聚合制备了聚甲基红膜修饰电极,并用线性扫描伏安法研究了盐酸环丙沙星(CPLX)在该修饰电极上的电化学行为,确定了聚合膜厚度、支持基质种类、最佳pH值、富集电位和时间等CPLX检测的最佳条件。结果表明,在pH=5.5的PBS缓冲体系中,CPLX在该修饰电极上出现一个不可逆的氧化峰,且在8.0×10~(-6)~1.0×10~(-4)mol/L范围内,氧化峰电流与其浓度呈现良好的线性关系,线性回归方程为Ip(μA)=0.618 93C(μmol/L)+57.191 04,R=0.998 1,检测下限为2.0×10~(-6)mol/L。平行测定的相对误差(RSD)小于1.325%(n=7),样品平均回收率分别为96.44%,99.82%和102.67%。     

羧化多壁碳纳米管/维生素B_(12)修饰电极测定多巴胺

制备了羧化多壁碳纳米管/维生素B12修饰玻碳电极,利用循环伏安法研究了多巴胺(DA)在此修饰电极上的电化学行为。结果表明,在pH为6.48的PBS缓冲溶液中,此修饰电极对DA有很强的电催化作用,明显增强了峰电流,峰电位差ΔEp由196 mV减小至69 mV,提高了电极反应的可逆性。在优化实验条件下,此修饰电极所测DA氧化峰电流与DA浓度在1.0×10-5~5.0×10-5mol/L及1.0×10-3~1.0×10-2mol/L范围内均呈线性,线性方程分别为y=373.78x+71.726(R2=0.995 8)和y=57.2x+365.22(R2=0.986 6),其中低浓度区的相关系数较高,应用于实际样品测定时结果较为满意。检测限可达8.0×10-8mol/L。     

Nafion/MWCNT修饰玻碳电极伏安法测定痕量镉

用阳极溶出伏安法考察了Nation/多壁碳纳米管(MWCNT)复合修饰玻碳电极测量痕量镉的优化条件.在pH 5.8的磷酸盐缓冲液中,当Cd2 在Nation/MWCNT修饰电极表面富集时间为3 min,电位扫速为150 mV/s时,该修饰电极在伏安图上能出现一灵敏的氧化峰,峰电位约为-0.78 V.利用该峰可以进行痕量镉的检测,峰电流与Cd2 浓度在8.0×10-10-1.0×10-8mol/L.的范围内呈良好线性关系,相关系数为0.999,检出限可达100×10-11mol/L(S/N=3).该法用于人发样品中镉含量的测定,平均回收率为98.7%.     

2,4,6-三氯苯酚在多壁碳纳米管修饰电极上的电化学行为研究

利用多壁碳纳米管较高比表面积、良好导电性和生物相容性等优良性能,制备多壁碳纳米管修饰玻碳电极,并研究2,4,6-三氯苯酚在多壁碳纳米管修饰电极上的电化学行为及其测定方法。采用滴涂法制备的多壁碳纳米管修饰玻碳电极作为工作电极,用循环伏安法测定2,4,6-三氯苯酚。结果表明,在最优的实验条件:pH=6.0的磷酸盐缓冲液,分散液的修饰量为5μL,扫描速率为50 mV/s下,2,4,6-三氯苯酚的浓度在10～110μmol/L内与对应的峰电流呈线性关系,相关系数为0.995 8,检出限为1.81×10^(-5)μmol/L。并且进行实际水样测试,回收率在95.72%～103.25%。所建立的检测2,4,6-三氯苯酚新方法灵敏度高、操作简单、测定线性范围宽,可用于2,4,6-三氯苯酚的快速检测。     

色氨酸在多壁碳纳米管-Nafion修饰玻碳电极上的电化学行为及测定

采用滴涂法制备了多壁碳纳米管-Nafion修饰玻碳电极(MWCNTs-Nafion/GCE),基于此修饰电极,建立了发酵液中色氨酸的电化学检测方法。结果表明:在pH 4.0的磷酸盐缓冲溶液中,色氨酸在MWCNTs-Nafion/GCE电极上有良好的响应,氧化峰电势为1.01 V,在5×10-7-2×10-4mol/L范围内,色氨酸氧化峰电流与其浓度呈良好的线性关系,线性方程为:Ip(10-6 A)=2.432×104 C(mol/L)+3.1452,R2为0.9973,检测限为2.7×10-8mol/L(S/N=3),回收率在98.3%~104.3%之间,相对标准偏差≤3.0%。该方法操作简单、结果稳定、选择性和灵敏度良好。     

碳纳米管修饰石墨电极的制备及应用

研究了多壁碳纳米管修饰石墨电极(MWNT/CE)的方法,并比较了不同修饰方法(嵌入法和涂层法)的修饰效果和修饰电极的稳定性.利用该修饰电极对马来酸噻吗洛尔(MET)的电催化作用,建立了一种新的电化学定量分析MLT的方法.在0.2 mol/L KNO3+0.1mol/L CH3COOH-CH3COONa(pH=4.82)体系中,MLT的浓度在2.3×10-5mol/L～5.8×10-4mol/L范围内时,氧化峰电流与浓度呈现良好的线性关系,线性相关系数为0.9996,检测限达5.6×10-6mol/L.该修饰电极用于含MLT药物样品的分析,八次平行测定结果的相对标准偏差为1.2%,样品回收率为95.1%～101.8%,结果令人满意.     

多壁碳纳米管修饰玻碳电极的制备及对苯二酚的测定

本文用多壁碳纳米管对玻碳电极进行修饰,制备修饰电极,确定最佳修饰层数。利用循环伏安法研究对苯二酚在修饰电极上的电化学行为,实验结果表明,修饰电极对对苯二酚具有较好的电催化能力。在磷酸缓冲溶液中测定对苯二酚,确定pH值、扫描速率等最佳检测条件,发现对苯二酚的氧化峰电流与浓度在8.0×10~(-6)~1.0×10~(-3)mol·L~(-1)范围内呈线性关系,检出限为1×10~(-7)mol·L~(-1),可用于模拟废水中微量对苯二酚的测定。     

多菌灵在多壁碳纳米管-聚4-(2-吡啶偶氮)间苯二酚膜修饰电极上的电化学行为及测定

制备了多壁碳纳米管-聚4-(2-吡啶偶氮)间苯二酚膜修饰电极,利用扫描电镜对新的复合膜修饰电极(PAR-MWNT/GCE)进行表征,研究了在多菌灵的循环伏安曲线以及它的差分脉冲伏安曲线。结果表明,该修饰电极对多菌灵具有良好的电催化作用。在8.0×10-6~2.06×10-4 mol/L浓度范围内,多菌灵的差分脉冲伏安法的峰电流和浓度呈现良好的线性关系,相关系数为0.997 11,检出限为2.5×10-7 mol/L(S/N=3)。PAR-MWNT/GCE复合物修饰电极可快速、简洁、方便的测定多菌灵的浓度。     

多巴胺在石墨烯/多壁碳纳米管电极上的电化学行为

采用滴涂法在玻碳电极上修饰氧化石墨烯及多壁碳纳米管,通过电化学还原方法制备石墨烯/多壁碳纳米管复合材料及相应修饰电极(ERGO/MWCNTs/GCE)。运用循环伏安法研究多巴胺(DA)在修饰电极上的电化学行为。研究表明:与裸玻碳电极相比,多巴胺在修饰电极上氧化峰与还原峰电位差为70 m V,峰电流显著提高,表明该电极对多巴胺具有较好的催化氧化作用。高浓度抗坏血酸的存在不影响多巴胺的测定。在优化实验条件下,多巴胺在4.8×10~(-7)~1.1×10~(-5)mol/L和1.1×10~(-5)~2.93×10~(-4)mol/L范围内呈良好的线性关系,检出限为8.7×10~(-8)mol/L,RSD为4.3%。     

Nanographite-reinforced carbon/carbon composites

Carbon/carbon composites (C/Cs) with nanographite platelets (NGP) filler in a matrix derived from phenolic resin were produced. Different weight concentration (0.5, 1.5, 3, 5 wt.%) NGP were introduced by spraying the NGP during the prepreg formation. The NGP-reinforced C/Cs were characterized for effect of NGP concentration on microstructure, porosity, interlaminar shear strength (ILSS), flexural, ultrasonic and vibration damping behavior. At 1.5 wt.% NGP C/C, the highest values of ILSS observed was 10.5 MPa (increased by 22%), flexure strength of 142.4 MPa (increased by 27%), flexural modulus of 59.2 GPa (increased by 68%) and porosity of 18.8% (reduced by 17.5%) in comparison to neat (without NGP) densified C/C. Ultrasonic testing revealed an average increase of 15% through the thickness Young’s modulus of NGP-C/C; (3.12 GPa at 1.5 wt.% NGP). A 20% average decrease in the damping ratio of the first four modes of vibration was observed in 1.5 wt.% NGP densified C/C. At low concentration (⩽1.5 wt.%) the NGP filled in the pores, cracks and debonded interface but at concentration higher than 1.5 wt.% NGP lost their effectiveness due to agglomeration. The required cycles for desired density/properties are projected to be less compared to neat C/C due to less porosity observed in ⩽1.5 wt.% NGP concentration C/C.     

Single-walled carbon nanotube buckypaper and mesophase pitch carbon/carbon composites

Carbon/carbon composites consisting of single-walled carbon nanotube (SWCNT) buckypaper (BP) and mesophase pitch resin have been produced through impregnation of BP with pitch using toluene as a solvent. Drying, stabilization and carbonization processes were performed sequentially, and repeated to increase the pitch content. Voids in the carbon/carbon composite samples decreased with increasing impregnation process cycles. Electrical conductivity and density of the composites increased with carbonization by two to three times that of pristine BP. These results indicate that discontinuity and intertube contact barriers of SWCNTs in the BP are partially overcome by the carbonization process of pitch. The temperature dependence of the Raman shift shows that mechanical strain is increased since carbonized pitch matrix surrounds the nanotubes.     

Pulsed electrodeposition of carbon nanotubes-hydroxyapatite nanocomposites for carbon/carbon composites

Carbon nanotubes-hydroxyapatite (CNTs-HA) composite coatings, which behaved like single composites, were synthesized by a combined method composed of electrophoretic deposition and pulsed electrodeposition. The phase compositions and the microstructure of the composite coatings were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectrometry (FTIR). Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) studies showed that the CNTs-HA composite coatings protected the bare carbon/carbon composites from corrosion in simulated body fluid (SBF) solution. The adhesion strength of CNTs-HA composite coating prepared by the combined method is 14.57±1.06 MPa achieved at the CNTs EPD time of 10 min. Compared to the other CNTs-HA composite coatings with different content of CNTs, the CNT-HA composite coating with the electrophoretic deposition of 10 min showed the best corrosion resistance. The morphology of CNTs-HA composite coatings immersed in SBF solution rendered the formation of HA crystallites. In addition, in vitro cellular responses to the CNTs-HA composite coatings were assessed to investigate the proliferation and morphology of mouse cells 3T3 cell line.     

Kinetics of pyrolytic carbon infiltration for the preparation of ceramic/carbon and carbon/carbon composites

Carbon/carbon and zeolite/carbon composites have been prepared by pyrolytic carbon infiltration of organic and inorganic substrates with different porous structures. The chemical vapour infiltration kinetics of these substrates has been studied in a thermogravimetric system at atmospheric pressure, using benzene as pyrolytic carbon precursor. The rate of pyrolytic carbon infiltration seems to depend on the porosity of the substrate available to the pyrolytic carbon precursor, irrespective of the nature of the substrate studied. Activation energy values of about 180 kJ/mol were found for the different substrates used in the temperature range of 700-800 °C, where the cracking reaction of benzene takes place, predominantly, in a heterogeneous form. At higher temperatures homogeneous reactions compete with heterogeneous ones and higher values of activation energies (280-380 kJ/mol) were obtained. The oxidation of the pyrolytic carbon deposited on the different substrates studied takes place in the same range of temperature, which suggests the presence of a similar pyrolytic carbon structure on substrates of different nature or a similar accessibility to the deposited layer.     

Microstructure of carbon/carbon composites reinforced with pitch-based ribbon-shape carbon fibers

Carbon/carbon composites were prepared with ribbon-shape pitch-based carbon fibers serving as reinforcement and thermosetting PFA resin and thermoplastic pitch as matrix precursors. The composites were heat treated to 1000, 1600 and 2700 °C. Microstructural transformations taking place in the reinforcement, carbon matrix, and the interface were studied using polarized optical and scanning electron microscopy. The fiber/matrix bond and ordering of the carbon matrix in heat-treated composites was found to vary depending on the heat treatment temperature of the fibers. Stabilized fiber cleaved during carbonization of resin-derived composites. In contrast, fibers retain their shape during carbonization of pitch matrix composites. Optical activity was observed in composites made with carbonized fibers; the extent decreases with increased heat treatment of the fibers. Studies at various heat treatment temperatures indicate that ribbon-shape fibers developed ordered structure at 1600 °C when co-carbonized with thermosetting resin or thermoplastic pitches.     

Porous carbon/carbon composites produced from carbon black and petroleum pitch

Granular porous carbon/carbon composites were prepared by mixing carbon black, petroleum pitch and a solvent, followed by granulating the mixture and carbonization of the resulting pellets in an inert atmosphere. The pore structure of this material is studied by mercury porosimetry and scanning electron microscopy. Based on the obtained results, a model for it is proposed. The effects of carbon black type used, filler/binder ratio, heat treatment temperature and mixing time on surface area, total pore volume and strength of the finished pellets were investigated. Comparison with activated carbons indicates that the investigated material can find industrial applications as a catalyst support and as an adsorbent for adsorption of large molecules due to the meso- and macroporous structure and low ash content.     

Friction behaviors of carbon/carbon composites with different pyrolytic carbon textures

Friction and wear properties of carbon/carbon (C/C) composites with a smooth laminar (SL), a medium textured rough laminar (RL) and a high textured RL pyrolytic carbon texture were investigated with a home-made laboratory scale dynamometer to simulate airplane normal landing (NL), over landing (OL) and rejected take-off (RTO) conditions. The morphology of worn surfaces at different braking levels was observed with scanning electron microscopy. The results show that C/C composites with RL have nearly constant friction coefficients, stable friction curves and proper wear loss at different braking levels, while friction coefficients of C/C composites with SL pyrolytic carbon decrease intensely and their oxidation losses increase greatly under OL and RTO conditions. Therefore, C/C composites with a high and medium textured RL pyrolytic carbon may satisfy the requirements of aircraft brakes. The good friction and wear properties of C/C composites with RL are due to the properties of RL, which leads to a uniform friction film forming on the friction surface.     

Mechanical behavior of two-dimensional carbon/carbon composites with interfacial carbon layers

Effect of interfacial carbon layers on the mechanical properties and fracture behavior of two-dimensional carbon fiber fabrics reinforced carbon matrix composites were investigated. Phenolic resin reinforced with two-dimensional plain woven carbon fiber fabrics was used as starting materials for carbon/carbon composites and was prepared using vacuum bag hot pressing technique. In order to study the effect of interfacial bonding, a carbon layer was applied to the carbon fabrics in advance. The carbon layers were prepared using petroleum pitch with different concentrations as precursors. The experimental results indicate that the carbon/carbon composites with interfacial carbon layers possess higher fracture energy than that without carbon layers after carbonization at 1000°C. For a pitch concentration of 0.15 g/ml, the carbon/carbon composites have both higher flexural strength and fracture energy than composites without carbon layers. Both flexural strength and fracture energy increased for composites with and without carbon layers after graphitization. The amount of increase in fracture energy was more significant for composites with interfacial carbon layers. Results indicate that a suitable pitch concentration should be used in order to tailor the mechanical behavior of carbon/carbon composites with interfacial carbon layers.