Fe2O3@Au core/shell nanoparticle-based electrochemical DNA biosensor for Escherichia coli detection

A Fe₂O₃@Au core/shell nanoparticle-based electrochemical DNA biosensor was developed for the amperometric detection of Escherichia coli (E. coli). Magnetic Fe₂O₃@Au nanoparticles were prepared by reducing HAuCl₄ on the surfaces of Fe₂O₃ nanoparticles. This DNA biosensor is based on a sandwich detection strategy, which involves capture probe immobilized on magnetic nanoparticles (MNPs), target and reporter probe labeled with horseradish peroxidase (HRP). Once magnetic field was added, these sandwich complexes were magnetically separated and HRP confined at the surfaces of MNPs could catalyze the enzyme substrate and generate electrochemical signals. The biosensor could detect the concentrations upper than 0.01 pM DNA target and upper than 500 cfu/mL of E. coli without any nucleic acid amplification steps. The detection limit could be lowered to 5 cfu/mL of E. coli after 4.0 h of incubation.     

Sensitive electrochemical immunoassay for chlorpyrifos by using flake-like Fe3O4 modified carbon nanotubes as the enhanced multienzyme label

A highly sensitive electrochemical immunoassay of chlorpyrifos (CPF) was developed by using a biocompatible quinone-rich polydopamine nanospheres modified glass carbon electrode as the sensor platform and multi-horseradish peroxidase-flake like Fe₃O₄ coated carbon nanotube nanocomposites as the signal label. Due to the quinone-rich polydopamine nanospheres, the platform exhibited excellent fixing capacity by simple coating of sticky polydopamine nanospheres and subsequent oxidization. By coprecipitation of Fe³⁺ and Fe²⁺ on polydopamine modified carbon nanotubes (CNTs) with the aid of ethylene glycol (EG), the flake-like Fe₃O₄ coated CNTs (CNTs@f-Fe₃O₄) were synthesized and chosen as the carrier of multi-enzyme label due to the high loading of secondary antibody (Ab₂) and horseradish peroxidase (HRP) and also the peroxidase-mimic activity of Fe₃O₄. Under the optimum conditions, the immunosensor can detect CPF over a wide range with a detection limit of 6.3 pg/mL. Besides, the high specificity, reproducibility and stability of the proposed immunosensor were also proved. The preliminary application in real sample showed good recoveries, indicating it holds promise for fast analysis of CPF in aquatic environment.     

基于氧化铒石墨烯氧化物复合纳米材料的葡萄糖氧化酶直接电化学性能及对葡萄糖的检测

将稀土纳米材料Er₂O₃用于构建葡萄糖生物传感器。Er₂O₃和氧化石墨烯形成复合基底,将葡萄糖氧化酶（GOD）固载在玻碳电极表面。首先利用SEM和XRD技术对所制备的Er₂O₃和氧化石墨烯纳米材料进行表征。利用EIS和CV对整个生物传感器制备过程进行表征。Er₂O₃的存在能有效地保持GOD的生物活性并加速其与电极之间的电子传递。由于Er₂O₃和氧化石墨烯之间的协同效应,使得制备的传感器在CV图中呈现一对明显的氧化还原峰,证实GOD和电极之间的直接电子传递性能。当用于对葡萄糖的电催化氧化时,传感器的CV响应随着葡萄糖浓度的增加而变弱。在葡萄糖浓度为1~10 mmol·L^-1范围内,CV响应值与葡萄糖浓度成线性关系。此外,传感器具有好的稳定性和重现性。     

基于氧化铒-石墨烯氧化物复合纳米材料的葡萄糖氧化酶直接电化学性能及对葡萄糖的检测

将稀土纳米材料Er₂O₃用于构建葡萄糖生物传感器。Er₂O₃和氧化石墨烯形成复合基底,将葡萄糖氧化酶（GOD）固载在玻碳电极表面。首先利用SEM和XRD技术对所制备的Er₂O₃和氧化石墨烯纳米材料进行表征。利用EIS和CV对整个生物传感器制备过程进行表征。Er₂O₃的存在能有效的保持GOD的生物活性并加速其电子传递速率。由于Er₂O₃和氧化石墨烯之间的协同效应,使得制备的传感器具有一对良好的氧化还原峰,证实GOD和电极之间的直接传递性能。当用于对葡萄糖的电催化氧化时,传感器的CV响应随着葡萄糖浓度的增加而变弱。在葡萄糖浓度为1~10 mmol·L^-1范围内,CV响应值与葡萄糖浓度成线性关系。此外,传感器具有好的稳定性和重现性。     

Composite film of carbon nanotubes and chitosan for preparation of amperometric hydrogen peroxide biosensor

A new amperometric biosensor for hydrogen peroxide was developed based on cross-linking horseradish peroxidase (HRP) by glutaraldehyde with multiwall carbon nanotubes/chitosan (MWNTs/chitosan) composite film coated on a glassy carbon electrode. MWNTs were firstly dissolved in a chitosan solution. Then the morphology of MWNTs/chitosan composite film was characterized by field-emission scanning electron microscopy. The results showed that MWNTs were well soluble in chitosan and robust films could be formed on the surface. HRP was cross-linked by glutaraldehyde with MWNTs/chitosan film to prepare a hydrogen peroxide biosensor. The enzyme electrode exhibited excellent electrocatalytic activity and rapid response for H₂O₂ in the absence of a mediator. The linear range of detection towards H₂O₂ (applied potential: −0.2 V) was from 1.67 × 10⁻⁵ to 7.40 × 10⁻⁴ M with correction coefficient of 0.998. The biosensor had good repeatability and stability for the determination of H₂O₂. There were no interferences from ascorbic acid, glucose, citrate acid and lactic acid.     

基于一维DNA组装磁性纳米探针的夹心型安培免疫传感器研究

采用Fe3O4(核)/ZrO2(壳)纳米磁珠(ZMPs)标记待测物识别抗体,并用HRP酶封闭和DNA链接,建立了一类新型的"珠链状"一维磁性纳米探针制备方法。将甲胎蛋白(AFP)一抗固定于纳米金修饰的玻碳电极表面,构建了免疫电极(GCE?AFP Ab1)。基于该电极和上述合成探针,通过双抗体夹心法测定免疫产物上HRP酶对过氧化脲(CP)氧化对苯二酚反应的催化电流,研制了一类基于一维纳米结构组装的夹心型安培免疫传感器。研究表明:此一维纳米结构探针不仅大大增加了酶在电极表面的富集量,成倍扩增了催化电流,显著提高了传感器的灵敏度,而且易于通过外磁场与背景液可控分离,简化了分析步骤,并提高了结果的重复性。此传感器对AFP检测的线性范围为0.01~25 mg/L;检出限达4 ng/L(3σ),并被用于人血清中痕量AFP的测定,结果满意。     

氨蒸发诱导法制备纳米结构LiNi1/3Co1/3Mn1/3O2及其作为高功率型锂离子电池正极材料的性能

采用氨蒸发诱导法成功制备出纳米结构LiNi_1/3Co_1/3Mn_1/3O₂正极材料,借助X射线衍射（XRD）分析、扫描电镜（SEM）、透射电镜（TEM）、高分辨率透射电镜（HRTEM）、能量分散谱（EDS）和比表面测试等表征手段及恒电流充放电测试研究了其晶体结构、微观形貌和电化学性能. 研究表明该方法制备出的材料具有良好的α-NaFeO₂层状结构,阳离子混排程度低. 纳米片交错堆积而成核桃仁状形貌,片与片之间形成许多纳米孔,而且纳米片的侧面属于{010}活性面,能够提供较多的锂离子的脱嵌通道. 在室温下及3.0-4.6 V充放电范围内,该材料在电流密度为0.5C、1C、3C、5C和10C时放电比容量分别为172.90、153.95、147.09、142.16 和131.23mAh·g^-1. 说明其具有优异的电化学性能,非常有潜力用于动力汽车等高功率密度锂离子电池中.     

Sensitively electrochemical detection of the DNA damage in situ by electro-Fenton reaction based on Fe@Fe2O3 core-shell nanonecklace and multi-walled carbon nanotube composite

An electrochemical biosensor for mimicking the metal-mediated DNA damage pathway in situ was presented. The Fenton reagents (H₂O₂ and iron ion) for the DNA damage were generated in situ with a constant rate from the sensing film. H₂O₂ and iron ion reacted further together to yield hydroxyl radical, which attacked DNA in the film. These courses of DNA damage were just like those happened in organism. The DNA damage was detected by monitoring the differential pulse voltammetric response of an electrochemical indicator, Co(phen)₃³⁺. Another electrochemical indicator, Ru(NH₃)₆³⁺, was also used for monitoring the DNA damage as a complementary means and the minimal detectable amount of DNA damage was 0.16 μg. The biosensor had good reproducibility. After this biosensor was used for 11 times, 90% of the first detection signal was obtained.     

Ultrasonic synthesis of polyaniline nanotubes containing Fe3O4 nanoparticles

Polyaniline (PANI) nanotubes containing Fe₃O₄ nanoparticles were synthesized under ultrasonic irradiation of the aqueous solutions of aniline, ammonium peroxydisulfate (APS), phosphoric acid (H₃PO₄), and the quantitative amount of Fe₃O₄. It was found that the obtained samples had the morphologies of nanotubes. TEM images and selected area electronic diffractions showed that Fe₃O₄ nanoparticles were embedded in PANI nanotubes. We thought that the mechanism of the formation of PANI/Fe₃O₄ nanotubes could be attributed to the ultrasonic irradiation and the H₃PO₄-aniline salt template. The molecular structure of PANI/Fe₃O₄ nanotubes were characterized by Fourier transform infrared spectroscopy (FTIR), UV-vis absorption spectra and X-ray diffraction (XRD). The conductivity and magnetic properties of the PANI nanotubes containing Fe₃O₄ nanoparticles were also investigated.     

Preparation of TiO2 nanosheet-carbon nanotube composite as immobilization platform for both primary and secondary antibodies in electrochemical immunoassay

TiO₂ nanosheets (TNSs) were synthesized and deposited on multi-wall carbon nanotubes (MWCNTs) to form a nano-composite through a hydrothermal method, followed by the characterization with various spectroscopic and microscopic techniques. The TNS-MWCNT composite was then applied as not only an electrode scaffold to immobilize primary antibody, but also as a carrier to load secondary antibody and horseradish peroxidase (HRP). In both cases, bis(sulfosuccinimidyl) suberate sodium salt acted as an amino cross-linker to covalently bind the biomolecules on TNS-MWCNT composite through their surface primary amino groups. After the sandwich-type immunoreaction, HPR was quantitatively captured on the electrode surface via the binding between secondary antibody and antigen, and electrochemical response of the immunosensor was then amplified by a H₂O₂ mediated HRP catalytic reaction. Using α-Fetoprotein as a model analyte, a linear range between 0.005 and 320 ng mL⁻¹ with a detection limit of 2.0 pg mL⁻¹ was achieved by differential pulse voltammetry. The improved immunosensor performance could be attributed to the biocompatibility and high specific surface area of TNS, and excellent electrical conductivity of MWCNTs, which accelerated the electron transfer at the electrode surface.     

Bi2WO6/TiO2纳米管异质结构复合材料的多模式下的光催化活性比较

以TiO₂纳米管为模板,采用多组分自组装结合水热法制备Bi₂WO₆/TiO₂纳米管异质结构复合材料。通过多种技术如X射线衍射（XRD）,X射线光电子能谱（XPS）,N₂吸附-脱附,扫描电镜（SEM）,高分辨透射电镜（HRTEM）和紫外可见漫反射吸收光谱（UV-Vis DRS）考察所制备样品的组成、结构、形貌、光吸收和电子性质。Bi₂WO₆纳米片或纳米粒子分布在TiO₂纳米管上,形成异质结构。随后,通过在紫外、可见和微波辅助光催化模式下降解染料罗丹明B（RhB）来评价复合催化剂的光催化活性。与TiO₂纳米管和Bi₂WO₆相比,Bi₂WO₆/TiO₂-35纳米管在多模式下表现出更优异的光催化活性。与紫外和可见降解模式相比,Bi₂WO₆/TiO₂-35纳米管在微波辅助光催化模式下对RhB的降解效率最高。这种增强的光催化活性源于适量Bi₂WO₆的引入、纳米管独特的形貌特征和降解模式所引起的增强的量子效率。降解过程中的活性物种被证明是h⁺,·OH和·O₂^-自由基。而且,在微波辅助光催化模式下,可产生更多的·OH和·O₂^-自由基。     

A Simple Layer‐by‐Layer Assembly Strategy for a Reagentless Biosensor Based on a Nanocomposite of Methylene Blue‐Multiwalled Carbon Nanotubes

A simple layer‐by‐layer (LBL) assembly strategy was established for constructing a novel reagentless biosensor based on a nanocomposite of methylene blue multiwalled carbon nanotubes (MB‐MWNTs). A nanocomposite of MB‐MWNTs was obtained by direct premixing and possessed good dispersion in barbital‐HCl buffer. Through electrostatic interactions, the nanocomposite of MB‐MWNTs could alternately be assembled with horseradish peroxidase (HRP) on the Au electrode modified with precursor films. UV/Vis spectra and scanning electron microscopy (SEM) were applied to reveal the formation of the nanocomposite of MB‐MWNTs. The LBL assembly process was also verified by electrochemical impedance spectroscopy (EIS). The MB is a well‐established mediator and efficiently facilitated the electron shuttle between the HRP and the electrode, as demonstrated by the cyclic voltammetry (CV) measurements. The as‐prepared reagentless biosensor exhibited a fast response for the determination of hydrogen peroxide (H₂O₂) and reached 95% of the steady‐state current within 3 s. It was found that the linear response range of the reagentless biosensor for H₂O₂ was from 4.0 μM to 3.78 mM with a detection limit of 1.0 μM and a sensitivity of 22.5 μA mM⁻¹. The biosensor exhibited a high reproducibility and stability.     

A novel nonenzymatic hydrogen peroxide sensor based on MnO2/graphene oxide nanocomposite

A new electrocatalyst, MnO₂/graphene oxide hybrid nanostructure was successfully synthesized for the nonenzymatic detection of H₂O₂. The morphological characterization was examined by scanning electron microscopy and transmission electron microscopy. The MnO₂/graphene oxide based electrodes showed high electrochemical activity for the detection of H₂O₂ in alkaline medium. The nonenzymatic biosensors displayed good performance along with low working potential, high sensitivity, low detection limit, and long-term stability, which could be attributed to the high surface area of graphene oxide providing for the deposition of MnO₂ nanoparticles. These results demonstrate that this new nanocomposite with the high surface area and electrocatalytic activity offers great promise for new class of nanostructured electrode for nonenzymatic biosensor and energy conversion applications.     

A novel amperometric biosensor for the detection of nitrophenol

We report on a novel amperometric biosensor for detecting phenolic compounds based on the co-immobilization of horseradish-peroxidase (HRP) and methylene blue (MB) with chitosan on Au-modified TiO₂ nanotube arrays. The titania nanotube arrays were directly grown on a Ti substrate using anodic oxidation first; a gold thin film was then coated onto the TiO₂ nanotubes by an argon plasma technique. The morphology and composition of the fabricated Au-modified TiO₂ nanotube arrays were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Cyclic voltammetry and amperometry were used to study the proposed electrochemical biosensor. The effect of pH, applied electrode potential and the concentration of H₂O₂ on the sensitivity of the biosensor have been systemically investigated. The performance of the proposed biosensor was tested using seven different phenolic compounds, showing very high sensitivity; in particular, the linearity of the biosensor for the detection of 3-nitrophenol was observed from 3 × 10⁻⁷ to 1.2 × 10⁻⁴ M with a detection limit of 9 × 10⁻⁸ M (based on the S/N = 3).     

Glycated hemoglobin biosensing integration formed on Au nanoparticle-dotted tubular TiO2 nanoarray

Excessive glucose present in the blood of diabetic patients binds with the hemoglobin of red blood cells resulting in the formation of glycated hemoglobin (HbA_1c). Measurement of HbA_1c levels may help in identifying the efficacy of the ongoing treatment and hence provide a better control over the disease. In the present study, we have synthesized a sensitive and stable scaffold, which consists of Au nanoparticles (GNPs)-dotted tubular TiO₂, for the construction of an electrochemical HbA_1c biosensor. 12-phosphotungstic acid has been used as a reducer after depositing well-dispersed GNPs on TiO₂ nanotubes (TiO₂ NTs) and an electron mediator by accelerating the electron transfer between the conductor and protein. The fabricated electrode was characterized using scanning electron microscopy (SEM), cyclic voltammetry (CV), Fourier transform infrared spectroscopy (FTIR) and electrochemical impedance spectroscopic analysis (EIS). Biosensor exhibited low detection limit (0.5 μM), fast response time (3 s) and wide linearity (from 0.5 to 2000 μM). The working electrode was used 100 times over 4 months, when stored at 4 °C. The HbA1c biosensor was then effectively used to measure the % of HbA_1c in the blood of apparently healthy persons and diabetic patients.     

不同碳源合成Na2MnPO4F/C及其作为锂离子电池正极材料的性能

采用湿法球磨和原位热解碳包覆相结合的方法, 分别以硬脂酸、柠檬酸、聚乙二醇-6000 (PEG-6000)、β-环糊精为碳源, 制备了不同结构的Na₂MnPO₄F/C 复合材料, 并研究了它们作为锂离子电池正极材料的电化学行为. 通过X射线衍射(XRD)、扫描电镜(SEM)、BET比表面积测试、恒流充放电等表征手段, 比较和分析了产物的结构、形貌及电化学性能. 研究结果表明, 由不同碳源制备的材料在形貌和颗粒尺寸上有明显差异, 进而对它们的电化学性能造成很大影响. 影响电化学性能的关键因素在于材料一次颗粒的大小. 其中, 以柠檬酸为碳源制备的样品呈现出典型的微纳结构和最小的一次颗粒(10-40 nm). 并给出最佳的电化学性能: 在1.5-4.8 V电压范围内, 以5 mA·g^-1充放电电流获得的首次放电比容量约为80 mAh·g^-1, 且循环稳定性良好.     

Amperometric Immunosensor Based on Gold Nanoparticles/Fe3O4-FCNTs-CS Composite Film Functionalized Interface for Carbofuran Detection

In this paper, a novel amperometric immunosensor for the determination of carbofuran based on gold nanoparticles (GNPs), magnetic Fe₃O₄ nanoparticles-functionalized multiwalled carbon nanotubes-chitosan (Fe₃O₄-FCNTs-CS), and bovine serum albumin (BSA) composite film was proposed. First, GNPs were immobilized onto the glassy carbon electrode (GCE) surface, and then the magnetic Fe₃O₄ nanoparticles mixed with chitosan-functionalized multiwall carbon nanotubes (CS-FCNTs) homogeneous composite (CS-FCNTs-Fe₃O₄) was immobilized onto the GNPs layer by electrostatic interactions between amino groups of CS and GNPs. Because chitosan (CS) contains many amino groups, it can absorb more antibodies. FCNTs have high surface area, high electrical conductivity, and it can enhance the electron transfer rate; Magnetite (Fe₃O₄) nanoparticles can provide a favorable microenvironment for biomolecules immobilization due to their good biocompatibility, strong superparamagnetic property, and low toxicity; and GNPs possess high surface-to-volume reaction, stability, and high conductivity. Gold Nanoparticles/Fe₃O₄-FCNTs-CS composite film was constructed onto the GCE surface, which had significant synergistic effects toward immunoreaction signal amplification. The stepwise assembly process was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), respectively. Under the optimal conditions, the current response was proportional to the concentration of carbofuran ranging from 1.0 ng/mL to 100.0 ng/mL and from 100.0 ng/mL to 200 µg/mL with the detection limit 0.032 ng/mL. The proposed immunosensor exhibited good accuracy, high sensitivity, and stability, and it can be used for detection of carbofuran pesticide.     

Li3V2(PO4)3/C的P123辅助流变相法制备及电化学性能

以V₂O₅、NH₄H₂PO₄、LiOH、柠檬酸、三嵌段聚合物表面活性剂P123为原料, 用流变相(RPR)法制备了Li₃V₂(PO₄)₃/C正极材料. 用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)等方法表征, 结果表明: 材料为单一纯相的单斜晶体结构, 颗粒均匀并呈现珊瑚结构; 恒流充放电, 循环伏安(CV)及电化学交流阻抗(EIS)等电化学性能测试表明, 采用P123 辅助合成材料电化学性能明显优于未采用P123 辅助合成材料. 3.0-4.3 V放电区间, 0.1C充放电下P123 辅助合成Li₃V₂(PO₄)₃/C材料首次放电比容量为129.8 mAh·g^-1, 经过50 次循环后容量只衰减0.9%; 倍率性能及循环性能优异, 1C、10C、25C的首次放电比容量分别为128.2、121.3、109.1 mAh·g^-1, 50次循环后容量保持率分别为99.1%, 96.9%, 90.7%. 这归因于三嵌段聚合物P123 作为分散剂的同时也作为有机碳源在颗粒表面及间隙形成碳网络, 有利于材料导电率的改善, 降低了其电荷转移阻抗, 减小了电极充放电过程的极化现象.     

Significant enhancement of the photoelectrochemical activity of TiO2 nanotubes

In the present work, we report on a facile and effective approach to significantly enhance the photocatalytic activity of TiO₂ nanotubes. The TiO₂ nanotubes prepared by the electrochemical oxidation of titanium in dimethyl sulfoxide (DMSO) with 2% HF were treated in a methanol solution under UV light irradiation. In comparison with the untreated TiO₂ nanotubes, the treatment resulted in a dramatic increase in the donor density of the TiO₂ nanotubes by approximately 3 orders of magnitude. The treated TiO₂ nanotubes exhibited a 15-fold enhancement in photocurrent and a 6.8-fold increase in the photoelectrochemical degradation of 4-nitrophenol, significant for hydrogen generation and wastewater treatment.     

Bilayer lipid membrane biosensor with enhanced stability for amperometric determination of hydrogen peroxide

In this paper, a polydopamine (PDA) film is electropolymerized on the surface of bilayer lipid membrane (BLM) which is immobilized with horseradish peroxidase (HRP). The coverage of the PDA film on HRP/BLM electrode is monitored by electrochemical impedance spectroscopy (EIS). The electrocatalytic reduction of H₂O₂ at the PDA/HRP/BLM electrode is studied by means of cyclic voltammetry (CV). The biosensor has a fast response to H₂O₂ of less than 5 s and an excellent linear relationship is obtained in the concentration range from 2.5 × 10⁻⁷ to 3.1 × 10⁻³ mol L⁻¹, with a detection limit of 1.0 × 10⁻⁷ mol L⁻¹ (S/N = 3). The response current of BLM/HRP/PDA biosensor retains 84% of its original response after being stored in 0.1 mol L⁻¹ pH 7.0 PBS at 4 °C for 3 weeks. The selectivity, repeatability, and storage stability of PDA/HRP/BLM biosensor are greatly enhanced by the coverage of polydopamine film on BLM.