L-酪氨酸功能化多壁碳纳米管的制备及表征

采用L-酪氨酸作为修饰剂，制备了一种新型功能化的多壁碳纳米管，并对其进行了表征。红外光谱和电化学实验均证实碳纳米管和酪氨酸是通过酰胺键共价键合的。其中，循环伏安实验中0．22V处羧基峰的消失与红外光谱中1717cm^-1处N-酰化氨基酸的-C=O峰相对应，2931和2860cm^-1处的-CH2-的伸缩振动峰的出现证明了产物的形成。     

Influence of silver-decorated multi-walled carbon nanotubes on electrochemical performance of polyaniline-based electrodes

In this work, silver (Ag) nanoparticles were deposited on multi-walled carbon nanotubes (MWNTs) by chemical reduction while Ag-decorated MWNTs (Ag-MWNTs)/polyaniline (PANI) composites were prepared by oxidation polymerization. The effect of the Ag incorporated into the interface of the composites on the electrochemical performance of the MWNTs/PANI was investigated. It was found that highly dispersed Ag nanoparticles were deposited onto the MWNTs, and the Ag-MWNTs were successfully coated by PANI. According to cyclic voltammograms, the Ag-MWNTs/PANI exhibited significantly increased electrochemical performances compared to MWNTs/PANI and the highest specific capacitance obtained of MWNTs/PANI and 0.15 M Ag-MWNTs/PANI was 162 F/g and 205 F/g, respectively. This indicated that Ag nanoparticles that were deposited onto the MWNTs caused an enhanced electrochemical performance of the MWNTs/PANI due to their high electric conductivity, which resulted in an increase of the charge transfer between the MWNTs and PANI by a bridge effect.     

Application of multi-walled carbon nanotubes modified carbon ionic liquid electrode for electrocatalytic oxidation of dopamine

A simple, sensitive, and reliable method based on a multi-walled carbon nanotubes (MWNTs) modified carbon ionic liquid electrode (CILE) has been successfully developed for determination of dopamine (DA) in the presence of ascorbic acid (AA). The acid-treated MWNTs with carboxylic acid functional groups could promote the electron-transfer reaction of DA and inhibit the voltammetric response of AA. Due to the good performance of the ionic liquid, the electrochemical response of DA on the MWNTs/CILE was better than that of other MWNTs modified electrodes. Under the optimum conditions a linear calibration plot was obtained in the range 5.0×10(-8) to 2.0×10(-4) mol L(-1) and the detection limit was 1.0×10(-8) mol L(-1).     

基于多壁碳纳米管/壳聚糖多层膜修饰玻碳电极邻苯二酚的测定

改进了碳纳米管在壳聚糖溶液中的分散方法,制备了多壁碳纳米管/壳聚糖多层膜修饰玻碳电极,对比了不同修饰层数膜电极的循环伏安和电化学阻抗行为,5层多壁碳纳米管/壳聚糖膜修饰玻碳电极的电化学性能优良.在最优实验条件下,该修饰玻碳电极对邻苯二酚(CAT)有灵敏的响应,CAT浓度在3.99×10-6～9.09×10-4mol/L范围内与氧化峰电流呈良好的线性关系,检出限为2.39×10-6mol/L(S/N=3).该修饰玻碳电极性能稳定,测定4×10-5mol/LCAT溶液,RSD(n=10)为2.1%;15周后,该电极的响应值仅降低1.9%.     

Direct electrochemistry with enhanced electrocatalytic activity of hemoglobin in hybrid modified electrodes composed of graphene and multi-walled carbon nanotubes

A graphene (GR) and multi-walled carbon nanotubes (MWCNT) hybrid was prepared and modified on a 1-hexylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE). Hemoglobin (Hb) was immobilized on GR-MWCNT/CILE surface with Nafion as the film forming material and the modified electrode was denoted as Nafion/Hb-GR-MWCNT/CILE. Spectroscopic results revealed that Hb molecules retained its native structure in the GR-MWCNT hybird. Electrochemical behaviors of Hb were carefully investigated by cyclic voltammetry with a pair of well-defined redox peaks obtained, which indicated that direct electron transfer of Hb was realized in the hybrid modified electrode. The result could be attributed to the synergistic effects of GR-MWCNT hybrid with enlarged surface area and improved conductivity through the formation of a three-dimensional network. Electrochemical parameters of the immobilized Hb on the electrode surface were further calculated with the results of the electron transfer number (n) as 1.03, the charge transfer coefficient (a) as 0.58 and the electron-transfer rate constant (k_s) as 0.97 s⁻¹. The Hb modified electrode showed good electrocatalytic ability toward the reduction of different substrates such as trichloroacetic acid in the concentration range from 0.05 to 38.0 mmol L⁻¹ with a detection limit of 0.0153 mmol L⁻¹ (3σ), H₂O₂ in the concentration range from 0.1 to 516.0 mmol L⁻¹ with a detection limit of 34.9 nmol/L (3σ) and NaNO₂ in the concentration range from 0.5 to 650.0 mmol L⁻¹ with a detection limit of 0.282 μmol L⁻¹ (3σ). So the proposed electrode had the potential application in the third-generation electrochemical biosensors without mediator.     

A comparative study on properties of multi-walled carbon nanotubes (MWCNTs) modified with acids and oxyfluorination

In this study, the surface modification of multi-walled carbon nanotubes (MWCNTs) with acid and oxyfluorination has been examined. Acid treatment of multi-walled CNTs produces many functionalized groups on the surface of MWCNTs, such as C-N stretching and the asymmetric carboxylate group (-COO-). It can be concluded that nitrogen doping of the graphite sheets may take place and a C-N bond identical to the sp³-bonded carbon nitride may form during the acid treatment process. In addition, oxyfluorinated MWCNTs exhibit higher BET specific surface area and mesopore volume than those of the as-received and acid treated MWCNTs. Therefore, acid and oxyfluorination treatments are more effective methods for enhancing the chemical and textural properties of MWCNTs.     

Electrochemical behavior and determination of fluphenazine at multi-walled carbon nanotubes/(3-mercaptopropyl)trimethoxysilane bilayer modified gold electrodes

A novel multi-walled carbon nanotubes/(3-mercaptopropyl)trimethoxysilane (MPS) bilayer modified gold electrode was prepared and used to study the electrochemcial behavior of fluphenazine and determine it. Fluphenazine could effectively accumulate at this electrode and produce two anodic peaks at about 0.78 V and 0.93 V (versus SCE). The peak at about 0.78 V was much higher and sensitive, thus it could be applied to the determination. Various conditions were optimized for practical application. Under the selected conditions (i.e. 0.05 M pH 3.5 HCOOH-HCOONa buffer solution, 5 μl 1 mg ml⁻¹ multi-walled carbon nanotubes for Φ=2.0 mm electrode, accumulation at open circuit for 180 s), the anodic peak current was linear to fluphenazine concentration in the range from 5×10⁻⁸ to 1.5×10⁻⁵ M with correlation coefficient of 0.9984, the detection limit was 1×10⁻⁸ M. For a 1×10⁻⁵ M fluphenazine solution, the relative standard deviation of peak current was 2.51% (n=8). This method was successfully applied to the determination of fluphenazine in drug samples and the recovery was 96.4-104.4%. The electrode could be easily regenerated and exhibited some selectivity, but some surfactants reduced the peak current greatly. The modified electrode was characterized by alternating current impedance and electrochemical probe.     

普鲁士蓝/多壁碳纳米管修饰电极测定维生素C

利用电化学方法在多壁碳纳米管修饰的玻碳电极表面聚合一层普鲁士蓝,制备普鲁士蓝/多壁碳纳米管修饰玻碳电极,运用循环伏安法研究了维生素C(vc)在该修饰电极上的电化学行为.该修饰电极对Vc显示出快速的电化学响应和较好的电催化活性,在pH为4.0的磷酸盐溶液中,Ve浓度与其氧化峰电流在8.0×10-4～1.0×10-2 mol/L范围内呈现良好的线性关系,相关系数为0.9993,检测限为6.4×10-5mol/L.该电极具有较好的稳定性和重现性.     

Electro-deposition of platinum nanoparticles on 4-mercaptobenzene-functionalized multi-walled carbon nanotubes

A new method to electro-deposit platinum nanoparticles on the surface of multi-walled carbon nanotubes (MWNTs) functionalized with 4-mercaptobenzene has been described. X-ray photoelectron spectroscopy results reveal that 4-mercaptobenzene was attached to the surface of MWNTs. Transmission electron microscope and X-ray diffraction analysis confirm that platinum nanoparticles were highly dispersed on the surface of MWNTs, and the average size of the platinum particle is 4.2 nm. The electrocatalytic properties of the Pt/MWNT composite electrode for methanol oxidation were investigated by cyclic voltammetry, and the results show that the fabricated composites exhibit high catalytic activity and good long-term stability. The study provides a feasible approach to fabricate Pt/MWNT composite electrode for direct methanol fuel cell.     

Impact behaviour of polypropylene filled with multi-walled carbon nanotubes

Multi-walled carbon nanotubes/polypropylene composites were compounded using a twin-screw extruder. Here, nanotubes with different lengths, i.e. 1-2 μm and 5-15 μm, respectively, were applied at a constant volume content of 1%. Notched Charpy impact tests showed that toughening effects of nanotubes depended highly on testing temperatures. The impact resistance was notably enhanced at a temperature above the glass transition temperature of matrix. Longer nanotubes performed more effective in toughening compared to the shorter ones. The increment of impact resistance of nanotube-filled polypropylene was considered due to enhanced load-carrying capability and much-increased deformation of matrix. SEM fractography further revealed the toughening mechanisms in a micro-scale. The impact energy was improved via nanotube breakage and pullout, which likely led to a series of energy consuming actions. In addition, the smaller spherulite size induced by nanotubes would be favourable to the impact resistance partially.     

Sensitive and selective molecularly imprinted electrochemical sensor based on multi-walled carbon nanotubes for doxycycline hyclate determination

An electrochemical sensor for doxycycline hyclate(DC)detection with high sensitivity and good selectivity is reported.The sensor was fabricated by electro-polymerization of molecularly imprinted polymers(MIPs)in the presence of DC onto multi-walled carbon nanotubes modified glassy carbon electrode(MWCNTs/GCE).The MWCNTs can significantly increase the current response of the sensor,leading to enhanced sensitivity.The MIPs provide selective recognition sites for DC detection.The experimental parameters,such as the polymer monomer concentration,supporting electrolyte pH,the time for electro-polymerization and the incubation time of the sensor with DC were optimized.Under optimized experimental conditions,the sensor displayed a linear range of 0.05μmol/L-0.5μmol/L towards DC detection,with the detection limit of 1.3×10^-2μmol/L.The sensor was successfully applied for recovery test of DC in human serum samples.     

Study on electrochemical behavior of tryptophan at a glassy carbon electrode modified with multi-walled carbon nanotubes embedded cerium hexacyanoferrate

Electrochemical behavior of cerium hexacyanoferrate (CeHCF) incorporated on multi-walled carbon nanotubes (MWNTs) modified GC electrode is investigated by scanning electron microscopy (SEM) and electrochemical techniques. The CeHCF/MWNT/GC electrode showed potent electrocatalytic activity toward the electrochemical oxidation of tryptophan in phosphate buffer solution (pH 7.0) with a diminution of the overpotential of 240 mV. The anodic peak currents increased linearly with the concentration of tryptophan in the range of 2.0 × 10⁻⁷ to 1.0 × 10⁻⁴ M with a detection limit of 2.0 × 10⁻⁸ M (at a S/N = 3). And the determination of tryptophan in pharmaceutical samples was satisfactory.     

Effect of nitrogen-containing groups on enhanced capacitive behaviors of multi-walled carbon nanotubes

In this work, electrochemical properties of surface treated multi-walled carbon nanotubes (MWNTs) are studied in supercapacitors. Nitrogen and oxygen functional groups containing MWNTs are prepared by urea and acidic treatments, respectively. The surface properties of the MWNTs are confirmed by X-ray photoelectron spectroscopy (XPS) and zeta-potential measurements. The textural properties are characterized by N₂ adsorption/desorption isotherm at 77 K using the BET eqaution, BJH method, and HK method. The electrochemical properties of the MWNTs are accumulated by cyclic voltammetry, impedance spectra, and charge-discharge cycling performance in 1 M H₂SO₄ at room temperature. As a result, the functionalized MWNTs lead to an increase in capacitance as compared with pristine MWNTs. It suggests that the pyridinic and pyridinic-N-oxides nitrogen species have effects on the specific capacitance due to the positive charge, and thus an improved electron transfer at high current loads results, the most important functional groups affecting capacitive behaviors.     

Voltammetric determination of quercetin at a multi-walled carbon nanotubes paste electrode

Quercetin can effectively accumulate at multi-walled carbon nanotubes-paraffin oil paste electrodes (CNTPE) and cause a sensitive anodic peak at around 0.32 V (vs. SCE) in a 0.10 M phosphate buffer solution (pH = 4.0). Under optimized conditions, the anodic peak current is linear to quercetin concentration in the ranges of 2.0 × 10^− 9−1.0 × 10^− 7 M and 1.0 × 10^− 7−2.0 × 10^− 5 M, and the regression equations are i_p (μA) = 0.0017 + 0.928c (μM, r = 0.999) and i_p (μA) = 0.183 + 0.0731c (μM, r = 0.995), respectively. This paste electrode can be regenerated by repetitively cycling in a blank solution for about 2 min. A 1.0 × 10^− 6 M quercetin solution is measured for 10 times using the same electrode regenerated after every determination, and the relative standard deviation of the peak current is 1.7%. The method has been applied to the determination of quercetin in hydrolysate product of rutin and the recovery is 99.2–102.6%. In comparison with graphite paste electrode, carbon nanotubes-nujol paste electrode and carbon nanotubes casting film modified glassy carbon electrode, the CNTPE gives higher ratio of signal to background current and better defined voltammetric peak.     

多壁碳纳米管-分子印迹传感器测定盐酸克伦特罗

结合碳纳米材料和分子印迹技术,建立了以K3[Fe(CN)6]为探针测定盐酸克伦特罗的方法。以邻苯二胺为功能单体,盐酸克伦特罗为模板,采用电化学聚合法在多壁碳纳米管修饰电极表面制备了分子印迹薄膜。用乙腈水溶液可快速去除模板,得到多壁碳纳米管-分子印迹传感器。用循环伏安法、交流阻抗法和石英晶体微天平技术对印迹膜进行了表征,膜厚为12.3 nm。K3[Fe(CN)6]的相对峰电流与盐酸克伦特罗的浓度在4.0×10-8～6.6×10-6 mol/L范围内呈线性关系,检测限为8.1×10-9 mol/L。选择性实验表明传感器对结构类似物具有较强的抗干扰能力。此传感器可用于猪肉中盐酸克伦特罗的测定,加标回收率为101.3%～107.9%。     

An enhanced electrocatalytic oxidation and determination of 2,4-dichlorophenol on multilayer deposited functionalized multi-walled carbon nanotube/Nafion composite film electrode

The voltammetric (CV and DPV) behavior of multi-walled carbon nanotube/Nafion composite coupled with a glassy carbon electrode was investigated for the determination of 2,4-dichlorophenol. The structural and morphological evaluation by XRD and FESEM revealed that the acid treated MWCNT retained their morphology without any structural change. The existence of the possible functional groups was investigated by FTIR and Raman spectroscopy. Compared to bare GCE, a significantly reduced interfacial charge transfer resistance was noticed for MWCNT/Nafion/GCE by electrochemical impedance spectroscopy (EIS). The use of Nafion not only contributed to the non-covalent functionalization of MWCNT, but also protected the electrode surface against the polymerization of phenoxy radicals forming a passivating film. For MWCNT/Nafion/GCE, the combination of anti-passivating ability and excellent catalytic properties resulted in the rapid and direct electrochemical determination of 2,4-DCP. Under optimal experimental conditions, the DPV responses for MWCNT/Nafion/GCE is linear over the 1–150 μmol/L range with a detection limit (S/N = 3) of 0.01 μmol/L. The presence of many interfering species had no influence on the signals of 2,4-DCP. The proposed sensor was successfully tested for the determination of 2,4-DCP in tap water samples and the recovery was in the range of 99.0–102.5%.     

Cobalt hexacyanoferrate modified multi-walled carbon nanotubes/graphite composite electrode as electrochemical sensor on microfluidic chip

Nanomaterial-based electrochemical sensor has received significant interest. In this work, cobalt hexacyanoferrate modified multi-walled carbon nanotubes/graphite composite electrode was electrochemically prepared and exploited as an amperometric detector for microchip electrophoresis. The prepared sensor displayed rapid and sensitive response towards hydrazine and isoniazid oxidation, which was attributed to synergetic electrocatalytic effect of cobalt hexacyanoferrate and multi-walled carbon nanotubes. The sensitivity enhancement with nearly two orders of magnitude was gained, compared with the bare carbon paste electrode, with the detection limit of 0.91 μM (S/N = 3) for hydrazine. Acceptable repeatability of the microanalysis system was verified by consecutive eleven injections of hydrazine without chip and electrode treatments, the RSDs for peak current and migration time were 3.4% and 2.1%, respectively. Meanwhile, well-shaped electrophoretic peaks were observed, mainly due to fast electron transfer of electroactive species on the modified electrode. The developed microchip-electrochemistry setup was successfully applied to the determination of hydrazine and isoniazid in river water and pharmaceutical preparation, respectively. Several merits of the novel electrochemical sensor coupled with microfluidic platform, such as comparative stability, easy fabrication and high sensitivity, hold great potential for hydrazine compounds assay in the lab-on-a-chip system.     

多壁碳纳米管对质谱分析中的血清蛋白富集作用研究

通过多壁碳纳米管(MWCNTs)对临床血清蛋白提取物进行富集处理,经表面增强激光解析离子化飞行时间质谱(SELDI-TOF-MS)检测,发现MWCNTs对血清中小分子量蛋白(<20 kDa)具有很好的富集效果。同时还考察了内径、长度等参数对血清蛋白富集效果的影响。该方法可用于临床血清样本中低丰度的小分子量蛋白的检测。     

Effect of multi-walled carbon nanotubes on non-isothermal crystallization kinetics of polyamide 6

The non-isothermal crystallization behaviors of multi-walled carbon nanotubes (MWNTs)/polyamide 6 (PA6) composites were investigated by differential scanning calorimetry (DSC). Three methods, namely, Avrami, Ozawa and Mo, were carried out to analyze the non-isothermal crystallization data. The results showed that the MWNTs in PA6 acted as effective nucleation agents. However the crystallization rate of composites obtained was lower than that of the neat PA6. It is indicated that the presence of MWNTs influenced the mechanism of nucleation and the growth of PA6 crystallites.     

Thermal degradation behavior of multi-walled carbon nanotubes/polyamide 6 composites

This paper focuses on the thermal degradation behavior of multi-walled carbon nanotubes (MWNTs)/polyamide 6 (PA6) composites under air and nitrogen atmosphere using thermogravimetric analysis (TGA). The results show that the dispersion of amino-functionalized MWNTs (f-MWNTs) in PA6 is more homogeneous than purified MWNTs (p-MWNTs). The presence of MWNTs improves the thermal stability of PA6 under air obviously, but has little effect on the thermal degradation behavior of PA6 under nitrogen atmosphere. The activation energies for degradation under air, E_a, estimated by Kissinger method, are 153, 165 and 169 kJ/mol for neat PA6, p-MWNTs/PA6 and f-MWNTs/PA6 composites, respectively. The p-MWNTs/PA6 composites show two-step degradation not only under air but also under nitrogen atmosphere, however, neat PA6 and the f-MWNTs/PA6 composites exhibit two-step degradation only under air.