普鲁士蓝@石墨烯-壳聚糖纳米复合物用于构建microRNA电化学传感器的研究

制备了基于普鲁士蓝(PB)、石墨烯(GN)、壳聚糖(Chi)的纳米复合物(PB@GN-Chi),并将其修饰在玻碳电极表面制得microRNA电化学传感器。实验发现,GN可有效提高敏感膜的导电性能和比表面积,增强PB在电极表面的稳定性和传感器的重现性。通过戊二醛的交联作用,将氨基化的捕获探针(ssDNA)固载在PB@GN-Chi修饰的电极表面,并用于miR-21的检测。以透射电子显微镜对纳米复合物的形态进行表征,采用循环伏安法、示差脉冲伏安法对传感器的电化学特性进行研究。实验结果表明,该传感器具有良好的稳定性和重现性,在2.8~2.8×10~4pmol/L浓度范围内,响应电流与miR-21浓度的对数呈线性关系,检出限为0.87 pmol/L,可用于miR-21的检测。     

壳聚糖/多壁碳纳米管复合膜电化学手性识别色氨酸对映异构体

采用滴涂方式将羧酸化多壁碳纳米管(f-MWCNTs)修饰于玻碳电极(GCE)表面成膜,然后恒电位法在上述修饰电极表面电沉积壳聚糖(CS)膜,形成CS和f-MWCNTs复合膜修饰电极(CS/f-MWCNTs/GCE),并用于色氨酸(Trp)对映异构体的手性识别。采用扫描电子显微镜(SEM)表征了修饰电极表面形貌的差异,电化学阻抗(EIS)和循环伏安法(CV)研究修饰电极的电化学行为差异。差分脉冲伏安法(DPV)用于区别色氨酸(Trp)对映异构体,分离系数可达2.38。研究发现该修饰电极对L-Trp的DPV响应信号强于D-Trp,检测的线性范围为8.0×10~(-6)~4.0×10~(-3)mol/L,检出限(S/N=3)为5.0×10~(-6)mol/L。该方法简单、经济、快速,对发展其它手性化合物的检测方法提供了参考。     

利巴韦林原位聚合分子印迹电化学传感器的研制

利用原位聚合分子印迹技术,以3-氨基苯硼酸(3-ABBA)为功能单体,利巴韦林(RIB)为目标分子,以硼酸和顺式二醇在不同酸碱度条件下可逆形成环内酯键为原理,在玻碳电极表面原位聚合形成利巴韦林分子印迹膜,研制了测定利巴韦林的分子印迹电化学传感器。采用循环伏安法(CV)和差分脉冲法(DPV)对印迹膜性能进行研究。DPV测试表明:在最优实验条件下,利巴韦林的浓度在5.0×10~(-8)~1.0×10~(-5)mol/L范围内与峰电流呈良好的线性关系,相关系数(r~2)为0.995 3,检出限(S/N=3)为1.5×10~(-8)mol/L。特异性实验表明制备的传感器对利巴韦林的选择性良好。该分子印迹电化学传感器可用于食品中利巴韦林的检测。     

Stainless Steel Electrodes to Determine Biodiesel Content in Petroleum Diesel Fuel by Electrochemical Impedance Spectroscopy

The blending ratio of biodiesel in petroleum diesel has become one of the most important parameters to ensure the quality of diesel/biodiesel blend. This paper presents a fast and simple method based on electrochemical impedance spectroscopy to determine the biodiesel content in diesel fuel. Different from the method reported in the literature, using a pair of two identical screen printed carbon paste electrodes, in the present work we used two electrodes made from 304 stainless steel with dimensions of 0.8×0.3 cm for the EIS measurements. Improved results were obtained in terms of sensitivity, stability of measurements, electrode reuse, and cost. In this procedure the charge transfer resistance is proportionally related to the biodiesel content, which is used to construct a calibration curve for the analysis of biodiesel content. The procedure was validated by an official method, using two samples, being one of them, certified through an official interlaboratory program of the Brazilian government (Interlaboratory Program for Biodiesel of National Agency of Petroleum, Natural Gas and Biofuels (PIB)/ANP). Good results were obtained in terms of recovery (102.6 %‐102.8 %), precision (coefficient of variation lower than 2.3 %), limit of detection (0.24 %) and limit of quantification (0.80 %). These results indicate that this method is sufficiently suitable as an alternative method to the official method for determining biodiesel content in commercial diesel fuel.     

Simple and Inexpensive Electrochemical Platform Based on Novel Homemade Carbon Ink and its Analytical Application for Determination of Nitrite

In this work we present the development of a simple handmade approach for the easy fabrication of three‐electrode electrochemical devices based on newly in‐house developed carbon ink composed of graphite powder and polystyrene. Different proportions of graphite/polystyrene were investigated for the optimization of the ink. The counter and reference electrodes were produced using commercial carbon ink and silver glue. Scanning electron microscopy, electrochemical impedance spectroscopy and cyclic voltammetry were used to investigate the morphology and the electrochemical properties of the sensor. The results showed that the electroactive area of the optimized working electrode was ca . 2.35 times larger than its geometric area. The RSD values obtained for repeatability and reproducibility were 0.20% and 2.78%, respectively, which suggest no significant variation on the electrodes fabricated. The analytical feasibility of the electrode was tested through its application for the determination of nitrite in drinking water. The quantifications were successfully performed at levels below the maximum contaminant level established for nitrite. A limit of detection of 1.42 × 10⁻⁶ mol L⁻¹ and recoveries of ca . 103 % were achieved. The results were validated using ion‐chromatography technique with good agreement. The performance of the unmodified sensor proposed here on nitrite determination was better than some recently reported modified electrodes obtained through complex procedures.     

A Novel Photo‐Induced Electrochemical Biosensing Method Based on Fluorescent Labeled Molecular Beacon

A novel photo‐induced electrochemical biosensing method has been developed based on fluorescence quenching effect and electrochemical method. In this sensing strategy, the molecular beacon probes labeled with methylene blue were immobilized on the gold nanoparticles modified gold electrode surface firstly; then dopamine was assembled on the electrode surface through electrostatic interaction with gold nanoparticles. Under the continuous illumination, the fluorescence of the methylene blue was quenched by the gold nanoparticles before hybridization; after hybridization with the complementary DNA, methylene blue was far away from the gold nanoparticles and the fluorescence recovered, and then singlet oxygen was generated in the photosensitive reaction of methylene blue in the presence of dissolved oxygen. Singlet oxygen reacted with dopamine, which resulted in the reduction of concentration of the dopamine on the electrode surface. The current of the dopamine on the electrode was used for the sensing of the conformational change of molecular beacon and hence for the detection of target DNA.     

Tapioca Biofilm Containing Nitrogen‐doped Titanium Dioxide Nanoparticles for Electrochemical Detection of 17‐β Estradiol

A novel sensor architecture based on thin film of tapioca decorated within nitrogen‐doped titanium dioxide (N‐TiO₂) nanoparticles is reported. The nanostructures were characterized by scanning electron microscope, transmission electron microscope, X‐rays diffraction and voltammetric techniques. The proposed electrode was used for detection of low concentrations of 17‐β estradiol in without purification step, which was investigated by using linear sweep adsorptive stripping voltammetry. Under optimal conditions, the analytical curve was linear over a 17β‐estradiol concentration range of 9.9×10⁻⁶ to 1.4×10⁻⁵ mol L⁻¹, with a detection limit of 1.7×10⁻⁷ mol L⁻¹. The tapioca and N‐TiO₂ nanoparticles homogeneous film was applied for detection of 17‐β‐estradiol in tap water and synthetic urine samples, which presented satisfactory results.     

Fe_3O_4/RGO复合材料的制备及其电化学性能研究

以改进Hummers法合成的氧化石墨烯(GO)为前驱体,通过水热法结合烧结工艺制备了四氧化三铁/还原氧化石墨烯(Fe_3O_4/RGO)复合材料。利用X射线衍射(XRD)、拉曼光谱(Raman)、扫描电镜(SEM)、透射电镜(TEM)等手段对复合材料的理化性能进行表征;通过充放电测试、循环伏安(CV)和电化学阻抗谱(EIS)等技术,综合考察了材料的储锂性能及电化学性能增强机制。结果表明,在200和600 m A/g电流密度下,Fe_3O_4/RGO复合负极循环60次后的放电比容量分别保持在709和479 mAh/g,表现出良好的倍率性能;相较于纯Fe_3O_4负极,复合负极呈现出更优异的锂电性能,其电化学性能的改善得益于RGO能增强材料的电导性和结构稳定性。     

基于3D打印薄层池和流场形电极的镉离子流动检测系统

首次提出了流场形(FFS)电极的概念,并印制了FFS三电极体系.结合3D打印的薄层流通池(TLFC),采用方波溶出伏安法(SWSV),构建了镉离子(Cd2+)流动电化学检测系统.考察了电极形状、测量方式、流速、介质条件、富集时间等条件的影响.结果表明,此检测系统测量灵敏度高,重现性和稳定性好.在优化条件下,Cd2+浓度在2 ～ 100 μg/L范围内与溶出峰电流呈良好的线性关系,相关系数为0.997,检出限为0.5 μg/L.将本方法应用于环境水样和生物甲烷发酵液中痕量Cd2+的检测,结果与ICP-AES无显著性差异,加标回收率为90％ ～ 106％.     

二氧化硅纳米均孔膜修饰电极检测化妆水中的抗氧化剂

制备了氧化铟锡(ITO)电极支撑的二氧化硅纳米均孔膜,保留胶束模板在纳米通道内,得到二氧化硅和胶束复合膜修饰的电极,并将其用于化妆品中丁基羟基苯甲醚和叔丁基对苯二酚的电化学检测。该均孔膜孔径2.3 nm,具有精确的尺寸筛分能力;胶束尾部的碳氢长链提供了疏水微环境,能够在水溶液中快速萃取和富集疏水有机分子。该电极对两种抗氧化剂的检测均获得了较好的灵敏度、线性范围和检测限,加标回收率分别为96.4%和104%,表明该电化学传感器具有一定的应用潜力。