Gold-dendrimer Nanocomposite Based Electrochemical Sensor for Dopamine

An electrochemical sensor for dopamine was developed by electrodepositing poly(propylene imine) (PPI) dendrimer and gold nanoparticles (AuNPs) onto a glassy carbon electrode (GCE). Electrochemical characterisation of the sensor was carried out by cyclic voltammetry and electrochemical impedance spectroscopy in ferri/ferrocyanide electrolyte. The nanocomposite electrode (GCE-PPI-AuNPs) showed improved electroactive surface area and electrochemical response over bare GCE. The sensor recorded a detection limit of 0.16 μM over a concentration range of 0.1 μM to 125 μM. The sensor was applied for dopamine detection in human serum samples and in the presence of interfering substances such as ascorbic acid and epinephrine.     

Molecularly Imprinted Electrochemical Sensor for the Detection of Organophosphorus Pesticide Profenofos

The presence of profenofos (PFF) in food has been strictly limited by legislation due to its genotoxic and toxic effects on health. It is therefore very important to establish simple and rapid analytical methods to detect traces of this insecticide. A reusable molecularly imprinted polypyrrole MIP(O-PPy) on a glassy carbon electrode (GCE) has been developed to measure PFF. The PPy was polymerized by cyclic voltammetry (CV) in the presence of template molecules (PFF) in an acidic solution on a GCE. The various experimental parameters such as film thickness, analyte/monomer ratio, and removal/rebinding requirements were examined and optimized. The signal of the redox probe (ferrocyanide/ferrocyanide) was used for the electrochemical detections. All steps of the sensor manufacturing, removal/rebinding of template molecules, and response to different PFF concentrations were tested by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The MIP sensor was able to detect PFF in the linear ranges of 1.0×10⁻⁹ to 1.0×10⁻⁶ M and 1.0×10⁻⁹ to 5.0×10⁻⁶ M, with detection limits, a signal-to-noise ratio (S/N) of three was used to estimate LOD, of about 1 nM using DPV and EIS, respectively. The MIP (PPy) GCE provided excellent PFF recognition performance and was successfully used to quantify PFF in sweet pepper samples, yielding recoveries not greater than 108 %.     

Study of the Electrochemical Behavior and Sensitive Detection of Pesticides Using Microelectrodes Allied to Square‐Wave Voltammetry

This work describes the application of gold and carbon fiber microelectrodes allied to square‐wave voltammetry for the study of the electrochemical behavior of the organophosphorous insecticides (methyl parathion and dichlorvos) and bipyridilium herbicides (paraquat and diquat), and the development of the sensitive methodology for their analytical determinations in natural water samples. The microelectrodes were lab‐made constructed and their electrochemical behavior was characterized by measuring the electrochemical response with a solution of potassium ferricyanide. The experimental and voltammetric conditions to obtain the best analytical signal, in terms of intensities and profile of the peak voltammetric, for four pesticides were optimized and the results were used to evaluate the type of the electrochemical redox process and to appraise the number of electrons covered in each reduction process that occurred for pesticides and also, to propose a possible redox mechanism for a reduction process of pesticides at microelectrodes. Analytical curves were constructed and presented the linear relationships between the peak currents and the concentration of pesticides, for this, the detection limits for pure water (laboratory samples) for four pesticides were calculated and presented values under 15 μg L^?1, lower than maximum limit for drinking water (100 μg L^?1) permitted by Brazilian Council for groundwater, indicating that the methodology could be employed to analyze those pesticides in natural water samples.     

对羟基苯甲酸酯分子印迹电化学传感器的研制

利用分子印迹技术,以对羟基苯甲酸乙酯为模板分子,甲基丙烯酸为单体,在玻碳电极表面原位聚合分子印迹聚合物敏感膜.采用方波伏安法对对羟基苯甲酸乙酯在该印迹电极上的电化学行为进行了研究,当响应时间为15 min时,0.95 V(vs SCE)处的峰电流与对羟基苯甲酸乙酯的浓度在2.0×10-6 ～2.0×10-4 mol/L范围内呈线性关系,检出限(S/N=3)为1.0 μmol/L,而相同条件下,对羟基苯甲酸乙酯在控制电极上的响应非常小并对浓度变化不灵敏;同时在印迹电极上氧化峰电位较在裸电极上发生了微弱正移.同一支印迹电极对对羟基苯甲酸乙酯响应值的RSD为4.3%(n=10).该印迹电极对尼泊金酯类具有良好的选择性,对对羟基苯甲酸甲酯、丙酯以及丁酯的选择性系数分别为1.89、1.70和2.01;对结构相似的苯酚、对羟基苯甲酸、对氨基苯甲酸等响应不灵敏,对结构差异较大的如维生素C等几乎无响应.用该分子印迹电极对实际样品进行分析,加标回收率大于90%.     

Facile Synthesis of Ordered Mesoporous Zirconia for Electrochemical Enrichment and Detection of Organophosphorus Pesticides

Highly crystallized mesoporous ZrO₂ nanomaterials were synthesized by solvent evaporation induced self‐assembly approach. Ordered mesoporous ZrO₂ nanomaterials were characterized by TEM, SEM, BET, XRD and UV‐Vis spectroscopy. The obtained nanomaterials exhibit the close‐packing mesopores with average pore size of 7 nm and a highly crystallized framework with tetragonal phase. A non‐enzyme electrochemical sensor based on ordered mesoporous ZrO₂ is established for selective detection of methyl parathion (MP). The online extraction of MP is firstly achieved by ZrO₂ modified electrode at open‐circuit potential for 5 min., and the sensitive detection of MP is performed by differential pulse voltammetry (DPV) method. By comparison, DPV responses of mesoporous ZrO₂ are 40 times and 25 times larger than that of mesoporous silica and mesoporous carbon with the similar pore structure, implying the specific affinity advantage of zirconia to phosphoric group. The quantitative analysis result shows that the voltammetric currents are linear with concentrations of MP ranging from 1 ng/ml to 2 μg/ml with a detection limit of 0.53 ng/ml. The sensor also exhibits good stability and high selectivity against interfering species. The excellent analytical performances are owed to the accessible and uniform mesoporous structures, highly crystallized frameworks of ZrO₂ and its specific affinity to phosphate groups.     

Sensitive and Selective Electrochemical Sensor Based on Molecularly Imprinted Polypyrrole Hybrid Nanocomposites for Tetrabromobisphenol A Detection

Abstract

A sensitive and selective electrochemical sensor based on electropolymerized molecularly imprinted polypyrrole and gold nanoparticles–multiwalled carbon nanotubes (AuNPs–MWCNTs) hybrid nanocomposites was developed for the determination of tetrabromobisphenol A (TBBPA). A glassy carbon electrode (GCE) was modified with MWCNTs, and the AuNPs–MWCNTs/GCE was prepared by an electrodeposition method in HAuCl₄ solution. The AuNPs–MWCNTs nanocomposite showed high electrocatalytic activity, good conductivity, and sufficient reactive sites for the direct electro-oxidation of TBBPA. The molecularly imprinted polymers (MIPs) as recognition elements were synthesized through in situ electro-polymerization of pyrrole as functional monomers in the presence of the TBBPA template molecules. Under the optimal conditions, the developed sensor exhibited good selectivity towards TBBPA compared with structural analogs, high sensitivity, and excellent producibility. The electrochemical responses of the sensor toward TBBPA were obtained in the linear range from 0.5?nM to 1?μM with a limit of detection equal to 0.24?nM at a signal-to-noise ratio of 3.     

有机磷农药酶生物传感器研究进展

酶生物传感器（EBS）以简单、廉价、易于微型化等优势成了有机磷农药（OPs）传统分析方法的最佳替代品。本文从识别OPs的酶及识别机理、电化学EBS、酶的固定化技术、高分子材料的酶固定载体不同角度综述了有机磷农药酶生物传感器研究近况,并重点介绍了一次性丝网印刷酶电极。     

A Simple,Efficient and Ultrasensitive Gold Nanourchin Based Electrochemical Sensor for the Determination of an Antimalarial Drug: Mefloquine

Mefloquine (MQ) is a quinoline based antimalarial drug, which is potent against multiple drug‐resistant Plasmodium falciparum . It is widely prescribed for the prophylactic treatment of malaria. Due to extensive usage of MQ, constant monitoring of the drug level in human body is of paramount importancein order to ensure that optimum drug exposure is achieved. The present work describes a gold nanourchins (AuNUs) based electrochemical sensor for the determination of MQ.AuNUs were synthesized via seed‐mediated method and characterized using ultraviolet‐visible spectroscopy, energy‐dispersive X‐ray spectroscopy, field emission scanning electron microscopy, zeta‐sizer and electrochemical techniques (electrochemical impedance spectroscopy and cyclic voltammetry). Fabrication of the sensor was done by drop‐coating the synthesized AuNUs onto a glassy carbon electrode. The fabricated sensor exhibited enhanced voltammetric response, which was attributed to the excellent conductivity and high surface area of AuNUs. Under optimum square wave voltammetric conditions, the sensor displayed two linear response ranges (from 2.0×10⁻⁹ to 1.0×10⁻⁶ M and from 1.0×10⁻⁶ to 1.0×10⁻³ M) with a detection limit of 1.4 nM. The electrode demonstrated good reproducibility, stability and selectivity over common interferents. The utility of the sensor was successfully assessed for quantification of the drug in pharmaceutical preparation and spiked human urine sample. Thus, the present study demonstrates a promising approach for determination of MQ with practical utility in quality control and clinical analysis.     

Electrochemical Sensor Based on Multi‐walled Carbon Nanotube/Gold Nanoparticle Modified Glassy Carbon Electrode for Detection of Estradiol in Environmental Samples

We report a rapid and simple method for sensing estradiol by electro‐oxidation on a multi‐walled carbon nanotube (MWCNT) and gold nanoparticle (AuNP) modified glassy carbon electrode (GCE). Compared with a bare GCE, AuNP/GCE and MWCNT/GCE, the composite modified GCE shows an enhanced response to estradiol in 0.1 M phosphate buffer solution. Experimental parameters, including pH and accumulation time for estradiol determination were optimised at AuNP/MWCNT/GCE. A pH of 7.0 was found to be optimum pH with an accumulation time of 5 minutes. Estradiol was determined by linear sweep voltammetry over a dynamic range up to 20 %mol L^?1 and the limit of detection was estimated to be 7.0×10^?8 mol L^?1. The sensor was successfully applied to estradiol determination in tap water and waste water.     

Electrochemical Assay of Methyl Parathion in Homogeneous Reaction Using Water Soluble Films with Immobilized Acetylcholinesterase

Water soluble poly (vinyl alcohol) (PVA) was used to prepare the enzyme membranes of acetylcholinesterase (AChE) for electrochemical assaying methyl parathion in water insoluble organic solvent. The immobilized enzyme was separated from electrode for the development of enzyme inhibition-based bioassays. This assay is simple and convenient where enzyme membrane is applicable for single use and the electrode for repeated use. The enzyme membranes can be used handily piece by piece and the released AChE performs catalytic reaction homogeneously. The inhibition percentage of AChE increases with the concentration of methyl parathion ranging from 0.1 to 1 mg/mL.     

硒化铅纳米粒子DNA电化学传感器检测花椰菜花叶病毒35S启动子基因序列

以水热法合成十六烷基三甲基溴化铵(CTAB)修饰的PbSe纳米粒子。在碳糊电极表面制备的PbSe纳米粒子壳聚糖(CHIT)复合膜上,实现了DNA的固定和杂交,并用循环伏安法和电化学交流阻抗法进行了表征。应用电活性分子亚甲紫(MV)作为杂交指示剂,以微分脉冲伏安法对转基因植物CaMV35S启动子基因片段进行测定,检测范围为5.0×10-11～5.0×10-6mol/L;检出限为1.6×10-11mol/L(3σ)。该传感器能很好地识别DNA互补序列、非互补序列和2碱基错配序列。     

A No-washing Point-of-Care Electrochemical Biosensor Based on CuS Nanoparticles for Rapid and Sensitive Detection of Neuron-specific Enolase

Electrochemical biosensors have made outstanding achievements in recent years. However, the single pursuit of sensitivity and accuracy sometimes cannot meet the detection requirements and achieve high-efficiency measurements. Therefore, no-washing biosensors have more practical advantages. In this work, a disposable point-of-care (POC) electrochemical biosensor was designed for the sensitive and fast detection of neuron-specific enolase (NSE). Fe₃O₄ and CuS nanoparticles were used as the substrate material for capturing Ab₁ and the signal probe for labeling Ab₂ respectively. The disposable syringe filter was introduced into the determination procedure for simple sample separation, which easily realized no-washing detection. Due to the syringe filters with 200 nm pore diameter could only allow the small nanoparticles of CuS−Ab₂ pass through, the large-sized immunocomplex of Fe₃O₄−Ab₁/NSE/CuS−Ab₂ were blocked on the membrane. The uncombined CuS−Ab₂ particles were pushed out from the syringe and would occur electron transfer between Cu²⁺ and Cu⁺ to generate a current signal detected by the Au electrode. Under optimal conditions, the no-washing biosensor shows a wide linear concentration range (100 fg mL⁻¹∼50 ng mL⁻¹) with the limit of detection of 33 fg mL⁻¹ (S/N=3). Additionally, the biosensor exhibited excellent selectivity, storage stability and reproducibility. The outstanding advantages of the no-washing biosensor make it more suitable for POC testing.     

A Simple and Novel Electrochemical Sensor Based on Phosphomolybdic‐Polypyrrole Film Modified Electrode for Highly Sensitive Detection of Cholic Acid

A simpe electrochemical sensor for detection of cholic acid (CA) was designed by modifying phosphomolybdate (PMo₁₂) doped polypyrrole (PPy) film on glassy carbon electrode (PMo₁₂‐PPy/GCE). The electrochemical behavior of CA on PMo₁₂‐PPy/GCE was investigated by cyclic voltammetry and 0.5 order differential voltammetry. The results indicated that CA had high inhibitory activity toward the peak currents of PMo₁₂‐PPy/GCE. The reduction peak currents were linearly related to the logarithmic value of the concentration of CA from 1.0×10^?7 to 1.0×10^?3 mol/L with a low detection limit of 1.0×10^?8 mol/L. The developed sensor exhibited excellent sensitivity, selectivity and stability for detection of CA, and it could be successfully applied to detect the level of CA in the urine samples. Moreover, the response mechanism of CA on the PMo₁₂‐PPy/GCE was discussed in detail.     

双酚A在纳米金-离子液体复合修饰电极上的电化学行为及测定

该文制备了纳米金-离子液体修饰电极(GNP-[BMIM]PF6/GCE),用红外光谱对GNP和[BMIM]PF6进行了表征.采用交流阻抗法研究了GNP-[BMIM]PF6/GCE的表面电化学特性,同时研究了双酚A(BPA)在该修饰电极上的循环伏安行为.结果表明,BPA在该修饰电极上出现1个氧化峰,无还原峰,为不可逆电化...     

二甲氧基硫代磷酸酯类农药多残留免疫分析方法研究

以二甲氧基硫代磷酸酯类农药为目标,设计合成了系列半抗原及抗原,制备了4种宽谱特异性抗体。研究结果表明,含不饱和烷烃手臂的半抗原所制备的抗体宽谱特异性优于含酰胺键手臂的半抗原所制备的抗体。采用目标待测物的特征次级结构作为包被半抗原可显著提高ELISA检测灵敏度。经条件优化建立的最佳间接竞争ELISA多残留检测方法可同时检测8种常用高毒农药,其检出限(LOD)在2.6～104μg/kg之间,符合相关限量标准要求。生菜样品药物添加平均回收率为73.9%～121.4%;平均相对标准偏差为10.6%～18.4%。菜心样品药物添加平均回收率为80.4%～121.2%;平均相对标准偏差为13.5%～24.4%。方法精密度均达到气相色谱法的检测水平。     

Iron(III)‐mediated Electrochemical Detection of Levofloxacin in Complex Biological Samples

We report the design of an electrochemical sensor capable of detecting levofloxacin (LEVX) in complex biological samples. This detection strategy is simple, fast, and does not require sample pretreatment or electrode modification. Unlike previously developed electrochemical LEVX sensors that require direct oxidation of LEVX, the sensing mechanism is based on the complexation reactions between LEVX and iron(III), resulting in a concentration‐dependent decrease in the iron(III) reduction peak current and a shift in the peak potential. These changes are presumably attributed to the decrease in the concentration of uncomplexed Fe(III) in the solution. The concentration‐dependent change in both the current and potential can be used for quantification of LEVX in various samples, including 50 % synthetic urine and 25 % synthetic human saliva. The limit of detection was estimated to be in the range of 1.5 to 2.3 μM, concentrations that are much lower than the concentration of LEVX found in urine and saliva samples of patients administered this drug for conditions such as urinary tract infection. With further optimization, this sensing strategy could find applications in clinical pharmacokinetic studies.     

A Highly Efficient Fluorescent Sensor Based on AIEgen for Detection of Nitrophenolic Explosives

The detection of nitrophenolic explosives is important in counterterrorism and environmental protection, but it is still a challenge to identify the nitroaromatic compounds among those with a similar structure. Herein, a simple tetraphenylethene (TPE) derivative with aggregation-induced emission (AIE) characteristics was synthesized and used as a fluorescent sensor for the detection of nitrophenolic explosives (2, 4, 6-trinitrophenol, TNP and 2, 4-dinitrophenol, DNP) in water solution and in a solid state with a high selectivity. Meanwhile, it was found that only hydroxyl containing nitrophenolic explosives caused obvious fluorescence quenching. The sensing mechanism was investigated by using fluorescence titration and ¹H NMR spectra. This simple AIE-active probe can potentially be applied to the construction of portable detection devices for explosives.     

Synthesis and Characterization of Bismuth-Silver Nanoparticles for Electrochemical Sensor Applications

Silver, bismuth, and bismuth-silver nanoparticles were synthesized and characterized by cyclic voltammetry, electrochemical impedance spectroscopy, ultraviolet-visible spectroscopy, infrared spectroscopy, Raman spectroscopy, and transmission electron microscopy to determine the electrochemical, optical, structural, and morphological properties of the nanomaterials. The silver, bismuth, and bismuth-silver nanoparticles were shown to have an average particle size of 10–30 nanometers by microscopy. The electrochemical results showed that the bismuth-silver nanoparticles exhibited good electrocatalytic activity that can be harnessed for sensor construction and related applications. The ultraviolet-visible, infrared, and Raman spectroscopy results confirmed the structural properties of the bismuth-silver nanoparticles. In addition, the microscopy and electron diffraction morphological characterization confirmed the nature of the bismuth-silver nanoparticles.     

A Prototype of Electrochemical Sensor for Measurements of Carbonyl Compounds in Air

The paper presents the results of investigation on a prototype sensor for measurements of benzaldehyde and formaldehyde in air. Sensitivity, limit of quantification and coefficient of selectivity of the sensor have been determined as a function of membrane thickness and electrode type using square wave voltammetry (SWV) technique. The working and counter electrodes were made of platinum and gold. Ionic liquids 1‐hexyl, 3‐methylimidazolium bis(trifluoromethanesulfonyl)imide constituted an internal electrolyte. Polydimethylsiloxane (PDMS) membrane separated gaseous medium from the electrolyte.     

基于碳复合Fe3O4纳米粒子的过氧化氢电化学传感器研究

本文以碳纳米粒子复合Fe₃O₄磁性纳米粒子构建新型过氧化氢电化学传感器,该传感器对过氧化氢有良好的电催化性能,过氧化氢浓度在1.00×10^-6 ~ 1.00×10^-3 mol·L^-1范围内与其氧化峰电流之间呈良好线性关系(R = 0.9980),检出限为6.60×10^-7 mol·L^-1. 该传感器具有良好的抗干扰能力、较高的重现性和稳定性.