纳米碳管修饰铂结合溶胶-凝胶固定酶制备高性能胆碱生物传感器

为了提高胆碱传感器的灵敏度和抗干扰性,以纳米碳管修饰铂电极为基础电极,采用溶胶-凝胶法固定胆碱氧化酶(ChOx),构建了电流型胆碱检测生物传感器,对纳米碳管修饰电极的电化学特征进行分析,得知纳米碳管的引入不仅使电极对H2O2的催化电流增大,同时降低了电催化所需的恒定电位。讨论了缓冲液介质、pH值、酶负载量对传感器响应的影响。研究表明,所制备的传感器在pH 7.2、电位为0.15V条件下对氯化胆碱的线性响应范围为5.0×10-6~1.0×10-4mol/L;检出限为5.0×10-7mol/L;灵敏度为9.48μA/mmol/L。传感器的稳定性好,经过1个月,仍可保持初始电流的85%。抗干扰能力有很大提高。用于人体血清中的胆碱浓度测定,结果令人满意。     

层层自组装制备基于多壁碳纳米管的胆碱生物传感器

以经混酸处理的多壁碳纳米管(MWCNTs)修饰铂(Pt)电极,在此基础上固定(PAA/PVS)3复合膜,采用层层自组装技术将高分子聚电解质PDDA与胆碱氧化酶交替组装在已修饰的电极上,构建了电流型胆碱生物传感器。实验结果表明,MWCNTs的引入使电极对H2O2的催化电流明显增大,制成的酶电极可以有效控制酶量的使用,酶膜组装层数为8时最优,对胆碱的线性响应范围为5×10-7～1×10-4mol/L;灵敏度为12.53μA/mmol;响应时间为7.60s;检出限为2×10-7mol/L(S/N=3)。传感器的抗干扰能力强,稳定性好,30d时的响应电流值仍保持最初的89.5%。3次平行实验的RSD为3.64%。     

基于巯基乙酸与离子液体共修饰的过氧化氢生物传感器的研究

采用静电组装技术,将离子液体[Bmim]PF6与辣根过氧化物酶(HRP)交替固定在巯基乙酸修饰的金电极表面,制备了(HRP/[Bmim]PF6)n多层组装膜,并通过电化学阻抗谱(EIS)和傅立叶红外反射光谱(ATR-FTIR)对制备的组装膜进行了表征.以对苯二酚为电子媒介体,过氧化氢在(HRP/[Bmim]PF6)2双层组装膜传感器上的线性范围为1.6×10-6 ～2.5×10-3 mol/L,检出限为5.7×10-7 mol/L(S/N=3),达到95%稳态电流用时少于5 s,Kappm值为0.048 mmol/L,表明所固定的酶具有较高的生物活性.     

基于三维有序大孔金电极的过氧化氢无酶传感器

采用反相胶体-晶体模板技术以及电化学沉积法制得了三维有序大孔金膜修饰电极,并对修饰电极进行了表征,在此基础上构建了新型的H2O2无酶传感器。研究表明,此传感器在1×10-6～5.5×10-5mol/L和8×10-5～1.3×10-3mol/L范围内对H2O2还原峰电流有良好的线性响应;检出限为3.3×10-7mol/L(S/N=3),具有良好的稳定性和重现性。     

基于聚亚甲基蓝和碳纳米管/辣根过氧化物酶的有机过氧化物传感器

本文结合层层组装法和电化学聚合法,制备了电子介体聚亚甲基蓝(PMB)修饰的碳纳米管(CNTs)/辣根过氧化物酶(HRP)多层膜有机过氧化物传感器。利用电化学阻抗表征了(CNTs/HRP)n的层层组装过程,探讨了不同HRP层数对传感器响应的影响,并研究了传感器对有机过氧化物过氧化氢叔丁基、过氧化氢异丙基苯的电催化还原性能。该传感器对过氧化氢叔丁基的线性检测范围为1.75×10-5～7.25×10-3mol/L,检测限为1.36×10-6 mol/L;对过氧化氢异丙基苯的线性检测范围为3.87×10-6～1.47×10-3 mol/L,检测限为6.48×10-7 mol/L。     

基于纳米材料、聚电解质制备高性能乙醇生物传感器

以明胶包埋法作为乙醇氧化酶(AOX)的酶固定化方法,在比较多壁纳米碳管(MWCNTs)、纳米金、纳米氧化铁3种纳米材料的基础上,选择加入增效最明显的多壁纳米碳管提高灵敏度,在电极表面自组装聚丙烯胺盐酸盐/聚磺化乙烯硫酸盐(PAA/PVS)膜提高抗干扰性,制备出一种高灵敏度抗干扰性电流型乙醇生物传感器(Pt/(PAA/PVS)2PAA-MWCNTs/AOX)。本传感器灵敏度为1.04μA/(mmol/L),在2.5×10-5~2.5×10-3mol/L浓度范围内呈良好线性关系,线性方程为:I(μA)=0.2199 1.0400C(乙醇,mmol/L),r=0.9939;检出限为2.5×10-5mol/L;RSD<5%,稳定性好、抗干扰能力强。     

基于静电吸附甲苯胺蓝和纳米金固定过氧化物酶生物传感器的研究

以玻碳电极为基底,电聚合邻氨基苯甲酸(ABA),使其形成带负电的界面,通过分子间静电作用力,自组装一层带正电荷的电子媒介体甲苯胺蓝(TB),再通过媒介体的氨基吸附纳米金,最后静电吸附固定辣根过氧化物酶制备出H2O2传感器。探讨了膜聚合时间、媒介体组装时间、pH、温度、工作电位对电极响应的影响。在优化的实验条件下,该传感器对H2O2电流响应与其浓度为1.5×10-5~1.3×10-3mol/L范围内呈线性关系;检出限为5.6×10-6mol/L。此外,该传感器具有较低的工作电位,能有效地消除抗坏血酸等的干扰。     

基于壳聚糖膜固定双酶的胆碱传感器的研究

提出了一种基于壳聚糖膜固定辣根过氧化物酶 胆碱氧化酶的胆碱传感器的制备方法。该传感器以电聚合于玻碳电极的硫堇作为电子传递介体,在pH6. 8,外加电压-0. 2V(vs.SCE)条件下,其峰电流与浓度范围 5. 0×10-5 ~3. 0×10-3 mol/L的胆碱呈良好的线性响应;检出限为 1. 0×10-5 mol/L。传感器有良好的选择性和稳定性,使用一月后,仍能保持其初始活性的 80%。     

对乙酰氨基酚在L-半胱氨酸修饰金电极上的不可逆双安培测定

在裸金电极上制备了L-半胱氨酸自组装膜修饰电极(L-Cys/SAM-CME),研究了对乙酰氨基酚(AP)在L-Cys/SAM-CME上的电化学行为,结果发现该修饰电极对AP的氧化具有催化作用,与裸金电极相比,氧化峰电位降低了68mV,峰电流增大了1.2×10-5A。本文探讨自组装膜修饰技术用于构建不可逆双安培法的可行性,利用对AP在L-Cys/SAM-CME上的催化氧化和高锰酸钾在裸金电极上的还原构建双安培检测体系,建立了在外加电压为0V条件下流动注射双安培法直接测定对AP的方法。在0V外加电压下,0.05mol/L硫酸载液中,测得对AP的峰电流与其浓度在2.0×10-7mol/L~2.0×10-4mol/L范围内呈良好的线性关系(r=0.9986,n=13),检出限为9.4×10-8mol/L。连续测定1.00×10-4mol/L的AP溶液20次,电流值RSD为1.90%,进样频率为80样/h。     

去甲肾上腺素在3-氨基-5-巯基-1,2,4-三唑修饰金电极上的电化学行为及研究

本文通过自组装的方法制备了3-氨基-5-巯基-1,2,4-三唑(TA)修饰金电极。X射线光电子能谱表明,3-氨基-5-巯基-1,2,4-三唑是通过形成S-Au键而组装到Au电极表面。研究了去甲肾上腺素在该自组装膜电极上的电化学行为。实验结果表明:在pH 4.5的0.1 mol/L BR缓冲溶液中,膜电极对去甲肾上腺素的电化学氧化具有明显的催化作用,其氧化峰电流与去甲肾上腺素的浓度在2.0×10-6~1.9×10-4mol/L范围内呈良好线性关系。方法检出限为4.0×10-7mol/L。     

Supramolecular Assemblies of Nucleoside Functionalized Carbon Nanotubes: Synthesis,Film Preparation,and Properties

Nucleoside‐functionalized multi‐walled carbon nanotubes ( N‐MWCNTs ) were synthesized and characterized. A self‐organization process using hydrogen bonding interactions was then used for the fabrication of self‐assembled N‐MWCNTs films free of stabilizing agents, polymers, or surfactants. Membranes were produced by using a simple water‐dispersion‐based vacuum‐filtration method. Hydrogen‐bond recognition was confirmed by analysis with IR spectroscopy and TEM images. Restoration of the electronic conduction properties in the N‐MWCNTs membranes was performed by removing the organic portion by thermal treatment under an argon atmosphere to give d‐N‐MWCNTs . Electrical conductivity and thermal gravimetric analysis (TGA) measurements confirmed the efficiency of the annealing process. Finally, oxidative biodegradation of the films N‐MWCNTs and d‐N‐MWCNTs was performed by using horseradish peroxidase (HRP) and low concentrations of H₂O₂. Our results confirm that functional groups play an important role in the biodegradation of CNT by HRP: N‐MWCNTs films were completely biodegraded, whereas for d‐N‐MWCNTs films no degradation was observed, showing that the pristine CNT undergoes minimal enzyme‐catalyzed oxidation This novel methodology offers a straightforward supramolecular strategy for the construction of conductive and biodegradable carbon nanotube films.     

水溶性多壁碳纳米管/铜酞菁染料自组装薄膜的制备与表征

Water soluble multi-wall carbon nanotubes (MWCNTs) were prepared via chemical oxidation. Under ultrasonication,the chemically treated MWCNTs can be dispersed in water to form colloids. The MWCNTs were characterized by FT-IR spectra. The FT-IR spectra reveal the presence of carboxylic groups on the nanotubes. The functional groups can improve the nanotubes-solubility in water. Alcian Blue 8GX (AB), a quaternary ammonium dye of the copper phthalocyanine group, was dissolved in water and used to form electrostaticcally self-assembled multilayer films. The MWCNT/AB composite films were characterized by UV-vis absorption spectra as well as AFM and fluorescence spectrum. The experimental results show that the MWCNT/AB composite films can be produced easily. Compared to those of the AB aqueous solutions, composite films exhibit pronounced differences in the absorption and fluorescence spectra, which suggests that AB molecules aggregated in the composite film, and that a charge transfer might exist between AB molecules and the MWCNTs.     

Electroanalysis of Bisphenol A at a Multiwalled Carbon Nanotubes‐gold Nanoparticles Modified Glassy Carbon Electrode

A sensitive electrochemical method was developed for the determination of bisphenol A (BPA) at a glassy carbon electrode (GCE) modified with a multiwalled carbon nanotubes (MWCNTs)‐gold nanoparticles (GNPs) hybrid film, which was prepared based on the electrostatic interaction between positively charged cetyltrimethylammonium bromide (CTAB) and negatively charged MWCNTs and GNPs. The MWCNT‐GNPs/GCE exhibited an enhanced electroactivity for BPA oxidation versus unmodified GCE and MWCNTs/GCE. The experimental parameters, including the amounts of modified MWCNTs and GNPs, the pH of the supporting electrolyte, scan rate and accumulation time, were examined and optimized. Under the optimal conditions, the differential pulse voltammetric anodic peak current of BPA was linear with the BPA concentration from 2.0×10^?8 to 2×10^?5 mol L^?1, with a limit of detection of 7.5 nmol L^?1. The proposed procedure was applied to determine BPA leached from real plastic samples with satisfactory results.     

复合方式对MWCNTs/TiO2纳米复合薄膜光电化学性能的影响

采用溶胶-凝胶法制备了不同复合方式的系列多壁碳纳米管(multi-walled carbon nanotubes, MWCNTs)/TiO2纳米复合薄膜电极. 通过SEM表征了薄膜的表面形貌, 并测定了MWCNTs引入前后对TiO2晶型结构和光吸收性能的影响以及不同复合方式的纳米复合薄膜的光电化学特性. 结果表明, MWCNTs/TiO2纳米复合薄膜表面形成无序多孔的形貌, 其光谱吸收边可拓展到可见光区; MWCNTs底层分布的纳米复合薄膜比纯TiO2表现出更好的光电活性, 而MWCNTs在表层分布及均匀分布的纳米复合薄膜的光电活性相对较差. 依据载流子分离原理探讨了不同复合方式对纳米复合薄膜光电性能的影响, 底层分布MWCNTs的纳米复合薄膜由于MWCNTs有效地收集传递电子并阻止载流子的复合从而提高了光电化学活性.     

Enhanced oxygen reduction at Pd catalytic nanoparticles dispersed onto heteropolytungstate-assembled poly(diallyldimethylammonium)-functionalized carbon nanotubes

Both Keggin-type phosphotungstic acid (HPW) and Pd are not prominent catalysts towards the oxygen reduction (ORR), but their composite Pd-HPW catalyst produces a significantly higher electrochemical activity for the ORR in acidic media. The novel composite catalyst was synthesized by self-assembly of HPW on multi-walled carbon nanotubes (MWCNTs) via the electrostatic attraction between negatively charged HPW and positively charged poly(diallyldimethylammonium (PDDA)-wrapped MWCNTs, followed by dispersion of Pd nanoparticles onto the HPW-PDDA-MWCNT assembly. The as-prepared catalyst was characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). TEM images show that Pd nanoparticles were uniformly dispersed on the surface of MWCNTs even when the Pd loading was increased to 60 wt%. Electrochemical activity of the catalysts for the ORR was evaluated by steady state polarization measurements using a rotating disk electrode. Compared with the acid treated MWCNTs, Pd nanoparticles supported on the HPW-assembled MWCNTs show a much higher ORR activity that is comparable to conventional Pt/C catalysts. The high electrocatalytic activities could be related to high dispersion of Pd nanoparticles as well as synergistic effects originating from the high proton conductivity of HPW. The Pd/HPW-PDDA-MWCNTs system as the cathode catalyst in proton exchange membrane fuel cells is demonstrated.     

Nanohybrid Materials Consisting of Poly[(3‐aminobenzoic acid)‐co‐(3‐aminobenzenesulfonic acid)‐co‐aniline] and Multiwalled Carbon Nanotubes for Immobilization of Redox Active Cytochrome c

The development of a new surface architecture for the efficient direct electron transfer of positively charged redox proteins is presented. For this reason different kinds of polyaniline terpolymers consisting of aminobenzoic acid (AB), aminobenzenesulfonic acid (ABS) and aniline (A) with different monomer ratios were synthesized. The P(AB‐ABS‐A) were grafted to the surface of multiwalled carbon nanotubes (MWCNTs). FTIR measurements prove the covalent binding to the carboxylic groups of the MWCNTs while conductivity tests show an increase in the conductivity of the nanohybrid in comparison to the polymers. The [MWCNT‐P(AB‐ABS‐A)] nanohybrids were used for the immobilization of redox active cytochrome c (cyt.c). The positively charged protein can electrostatically interact with the negatively charged nanohybrid. Cyclic voltammetry (CV) shows an increase in the protein loading on [MWCNT‐P(AB‐ABS‐A)] coupled to cysteamine modified gold electrodes in comparison to non‐grafted MWCNTs. A further increase in the sulfonation degree of P(AB‐ABS‐A) leads to an enhanced current output of the modified electrodes. The redox activity of the polymer decreases after the immobilization of the cyt.c on the nanohybrid. For the first time polymers covalently grafted to the surface of MWCNTs are used in a biosensor.     

Voltammetric study on pristine and nitrogen-doped multi-walled carbon nanotubes decorated with gold nanoparticles

Films consisting of pristine multi-walled carbon nanotubes (MWCNTs) and nitrogen-doped MWCNTs (N-MWCNTs) were fabricated by means of chemical vapor deposition and chemically decorated with gold nanoparticles (AuNPs). Optical microscopy and image analysis reveal that the deposited AuNPs have diameters of 50–200 nm and 100–400 nm, respectively. The AuNP-modified films of MWCNTs and of N-MWCNTs were initially investigated with respect to their response to the ferro/ferricyanide redox system. The N-MWCNTs/AuNPs exhibit lower detection limit (0.345 μM) for this redox system compared to that of MWCNTs/AuNPs (0.902 μM). This is probably due to the presence of nitrogen that appears to enhance the electrocatalytic activity of MWCNTs. The findings demonstrate that the electrochemical responses of both films are distinctly enhanced upon deposition of AuNPs on their surfaces. The detection limits of MWCNTs/AuNPs and N-MWCNTs/AuNPs systems are lower by about 43 % and 27 %, respectively, compared to films not modified with AuNPs. The electrocatalytic activity of the films towards the oxidation of ascorbic acid (AA), uric acid (UA), and dopamine (DA) was studied. The findings reveal that N-MWCNTs/AuNPs represent a powerful analytical tool that enables simultaneous analysis of AA, UA, and DA in a single experiment.

Electrostatic‐Assembly of Carbon Nanotubes (CNTs) and Polymer Particles in Water: a Facile Approach to Improve the Dispersion of CNTs in Thermoplastics

Summary: A facile and organic‐solvent‐free method for preparing thermoprocessable multiwalled carbon nanotube (MWCNT)‐filled thermoplastics is presented. MWCNTs are oxidized, neutralized, and then assembled with cationic soap‐free poly(methyl methacrylate) (PMMA) particles directly in water. The spontaneous electrostatic coupling between the negatively charged MWCNTs and positively charged PMMA particles, and the viscoelastic and thermomechanical behavior of the nanocomposites, are investigated. The electrostatic coupling interactions improve the dispersion of nanotubes and facilitate the formation of filler networks in the polymer matrix.

Preparation of nanocomposites of oxidized MWCNTs and positively charged PMMA particles through electrostatic assembly.     

Electrochemical determination of bisphenol A based on PHD/MWCNTs modified glassy carbon electrode

A novel electrochemical sensor for the determination of bisphenol A (BPA) was fabricated by block polyelectrolyte composite films, which composed of diblock polyelectrolyte poly (2-hydroxyethyl methacrylate)-b-poly (2-(dimethylamino) ethyl methacrylate) (PHEMA-b-PDMAEMA, noted as PHD in the later content) and multi-walled carbon nanotubes (MWCNTs). The tertiary amino groups of PDMAEMA can be protonated at physiological pH. The protonated PDMAEMA can thus interact with the negatively charged BPA through electrostatic attraction to increase the BPA sorption capacity and enhance the ability for highly sensitive detection of BPA. The PHD/MWCNTs composite films combine the electrocatalytic property of MWCNTs and the electrostatic attraction of protonated PHD. Because of the above-mentioned excellent property of the composite films, the PHD/MWCNTs/glassy carbon electrode exhibited good electrocatalytic activity to electrooxidation of BPA. The wide linear response range of the BPA sensor was from 4.56 × 10^?5 g L^?1 to 2.28 × 10^?2 g L^?1 with a lower detection limit of 2.28 × 10^?6 g L^?1 (S/N = 3) and high sensitivity 2442.86 μA L g^?1 cm^?2. The current reached the steady-state current with a shorter response time less than 4 s. The proposed method was successfully applied to determine BPA in real samples (PVC food package, milk, tap water and pond water) and satisfactory results were obtained. These results indicated that the block polyelectrolyte composite have potential applicability of the BPA sensor.     

Luminescent Blooming of Dendronic Carbon Nanotubes through Ion‐Pairing Interactions with an EuIII Complex

A multiwalled carbon nanotube (MWCNT) scaffold was covalently functionalized with a second‐generation polyamidoamine (PAMAM) dendron, presenting four terminal amino groups per grafted aryl moiety. These reactive functions were alkylated to obtain a positively charged polycationic dendron/carbon nanotube system ( d‐MWCNTs?Cl ), which eventually underwent anion exchange reaction with a negatively charged and highly luminescent Eu^III complex ( [EuL₄]?NEt₄ , in which L =(2‐naphtoyltrifluoroacetonate)). This process afforded the target material d‐MWCNTs?[EuL₄] , in which MWCNTs are combined with red‐emitting Eu^III centers through electrostatic interactions with the dendronic branches. Characterization of the novel MWCNT materials was accomplished by means of TGA and TEM, whereas d‐MWCNTs?Cl and d‐MWCNTs? [EuL₄] further underwent XPS, SEM and Raman analyses. These studies demonstrate the integrity of the luminescent [EuL₄]^? center in the luminescent hybrid, the massive load of the cationic binding sites, and the virtually complete anion‐exchange into the final hybrid material. The occurrence of the ion‐pairing interaction with MWCNTs was unambiguously demonstrated through DOSY NMR diffusion studies. Photophysical investigations show that MWCNTs?[EuL₄] is a highly soluble and brightly luminescent red hybrid material in which MWCNTs act as photochemically inert scaffolds with negligible UV/Vis absorption, compared with the grafted Eu complex, and with no quenching activity. The high dispersibility of MWCNTs?[EuL₄] in a polymer matrix makes it a promising luminophore for applications in material science.