Impedance methods for electrochemical sensors using nanomaterials

This article presents an overview of electrochemical sensors that employ nanomaterials and utilize electrochemical impedance spectroscopy for analyte detection. The most widely utilized nanomaterials in impedance sensors are gold (Au) nanoparticles and carbon nanotubes (CNTs). Au nanoparticles have been employed in impedance sensors to form electrodes from nanoparticle ensembles and to amplify impedance signals by forming nanoparticle-biomolecule conjugates in the solution phase. CNTs have been employed for impedance sensors within composite electrodes and as nanoelectrode arrays. The advantages of nanomaterials in impedance sensors include increased sensor surface area, electrical conductivity and connectivity, chemical accessibility and electrocatalysis.     

Significance of nanomaterials in electrochemical sensors for nitrate detection: A review

Nanomaterial-enabled electrochemical sensors are designed as an economical, efficient, and user-friendly analytical tool for on-site and routine nitrate analysis over a wide range of environmental samples. The remarkable advances and tunable attributes of nanomaterials have greatly improved the analytical performance of electrochemical nitrate sensors. In this review, a comprehensive elucidation of the recent advances in nanomaterial-based electrochemical nitrate sensors is presented. The review firstly provides a general introduction, followed by typical electrochemical sensing methods. The next two sections detail various nanomaterials, including graphene derivatives, carbon nanotubes/fibers, metal/bimetal/metal oxide nanoparticles, and conducting polymers for modifying electrodes in enzymatic and non-enzymatic electrochemical nitrate sensors. Finally, the perspectives and current challenges in achieving real-world applications of nanomaterial-based electrochemical nitrate sensors are outlined.     

分子印迹电化学传感器测定L-色氨酸的研究

报道了一种由溶胶-凝胶法制备的分子印迹电化学传感器,并用于L-色氨酸的测定.印迹聚合物是由四乙氧基硅烷、甲基三甲氧基硅烷、苯基三甲氧基硅烷等聚合而成,L-色氨酸为模板分子.通过循环伏安法验证了印迹膜与模板分子的结合和去除.该传感器对L-色氨酸具有良好的选择性以及高的灵敏度,线性范围为1.0×10-9～1.0×10-5m...     

桑色素分子印迹传感器的制备与应用

以邻氨基酚( o-AP)为功能单体,桑色素为模板分子,基于分子间的相互作用力,在金电极表面电聚合制备具有特异性识别孔穴的桑色素分子印迹传感器膜。采用循环伏安法( CV)、差分脉冲伏安法( DPV)等研究了分子印迹膜的性能和分子印迹效应。探索了聚合膜配比及聚合扫描圈数对传感器性能的影响,优化了洗脱时间和印迹时间。比较了此传感器对其结构相似物的选择性响应,发现其对桑色素检测具有良好的选择性。在最佳实验条件下,此传感器对桑色素浓度定量测定范围为0.05~1.70μmol/L,线性方程为I(μA)=1.0800lgc(mol/L)+9.3599, R=0.9934,检出限为0.01μmol/L。用此传感器测定黑茶样品中桑色素的含量,加标回收率为104.0%~108.0%。     

葛根素分子印迹电化学传感器的制备及研究

以丙烯酰胺为功能单体,葛根素为模板分子,马来松香丙烯酸乙二醇酯为交联剂,采用循环伏安法合成了葛根素分子印迹膜,并以此为识别元件制备了葛根素电化学传感器。该传感器对葛根素具有高度的选择性和良好的敏感度,葛根素氧化峰电流与其浓度在6.0×10-8～1.6×10-3mol/L范围内呈良好的线性关系,检出限为2.0×10-8mol/L。将此传感器用于葛根素注射液和木瓜葛根片中葛根素的含量测定,回收率为97.7%～106.4%。     

Review: Carbon nanotube based electrochemical sensors for biomolecules

Carbon nanotubes (CNTs) have been incorporated in electrochemical sensors to decrease overpotential and improve sensitivity. In this review, we focus on recent literature that describes how CNT-based electrochemical sensors are being developed to detect neurotransmitters, proteins, small molecules such as glucose, and DNA. Different types of electrochemical methods are used in these sensors including direct electrochemical detection with amperometry or voltammetry, indirect detection of an oxidation product using enzyme sensors, and detection of conductivity changes using CNT-field effect transistors (FETs). Future challenges for the field include miniaturizing sensors, developing methods to use only a specific nanotube allotrope, and simplifying manufacturing.     

Synthesis and electrochemical applications of gold nanoparticles

This review covers recent advances in synthesis and electrochemical applications of gold nanoparticles (AuNPs). Described approaches include the synthesis of AuNPs via designing and choosing new protecting ligands; and applications in electrochemistry of AuNPs including AuNPs-based bioelectrochemical sensors, such as direct electrochemistry of redox-proteins, genosensors and immunosensors, and AuNPs as enhancing platform for electrocatalysis and electrochemical sensors.     

A strategy for improving the sensitivity of molecularly imprinted electrochemical sensors based on catalytic copper deposition

A novel method to improve the sensitivity of molecularly imprinted polymer sensors was developed. Oxytetracycline (OTC), which was selected as the template molecule, was first rebound to the imprinted cavities. Gold nanoparticles were then labeled with the amino groups of OTC molecules via electrostatic adsorption and non-covalent interactions. Copper ions were catalytically reduced by the gold nanoparticles, and copper was deposited onto the electrode. The deposited copper was electrochemically dissolved, and its oxidative currents were recorded by differential pulse voltammetry (DPV). OTC could be determined indirectly within the concentration range of 3.0 × 10⁻¹⁰ to 1.5 × 10⁻⁷ mol L⁻¹ with a detection limit of 6.8 × 10⁻¹¹ mol L⁻¹.     

Development and Characterization of an Electrochemical Sensor for Cinchonidine Detection Based on Molecularly Imprinted Polymer with Modified Rosin as Cross-linker

Molecularly imprinted polymers(MIPs) were applied as molecular recognition elements to an electrochemical sensor for cinchonidine(CD). A kind of MIP was synthesized with cinchonidine as template, modified rosin( ethylene glycol maleic rosinate acrylate) containing the skeleton of phenanthrene rings as cross-linker and methylacrylic acid as functional monomer. MIP membrane was prepared on a glassy carbon electrode for the determination of CD via free radical polymerization method. Electrochemical impedance spectroscopy(EIS) and cyclic voltammetry( CV) were used to characterize the membrane electrochemical behavior in electrode fabrication process. The experimental conditions were discussed. Under optimum conditions, it was found that the response of peak currents was linear to the concentration of CD in a range of 0.013―2.26 mmol/L. The detection limit for CD is 1 μmol/L, the relative standard deviation for 100 μmol/L CD is 1.34% and the incubation time is 2 min. The sensor was applied to the determination of CD in urine samples with satisfactory results.     

以马来松香丙烯酸乙二醇酯为交联剂的咖啡因分子印迹电化学传感器

以咖啡因为模板分子, 含菲环骨架的马来松香丙烯酸乙二醇酯为交联剂, 甲基丙烯酸为功能单体, 在玻碳电极表面以自由基热聚合的方式制备分子印迹聚合物敏感膜, 构建了测定咖啡因的新型分子印迹膜电化学传感器. 通过循环伏安法、 差分脉冲伏安法及电化学交流阻抗法研究了传感器对咖啡因的响应特性. 结果表明, 在最佳的实验条件下, 传感器的峰电流与咖啡因浓度在3.00×10^-3~2.73 mmol/L范围内呈现良好的线性关系, 检出限(S/N=3)为1.12×10^-4 mmol/L. 传感器具有良好的选择性和重现性. 将该传感器用于可口可乐饮料中咖啡因含量的测定, 平均回收率为98.7%.     

Facile and controllable one-step fabrication of molecularly imprinted polymer membrane by magnetic field directed self-assembly for electrochemical sensing of glutathione

Based on magnetic field directed self-assembly (MDSA) of the ternary Fe₃O₄@PANI/rGO nanocomposites, a facile and controllable molecularly imprinted electrochemical sensor (MIES) was fabricated through a one-step approach for detection of glutathione (GSH). The ternary Fe₃O₄@PANI/rGO nanocomposites were obtained by chemical oxidative polymerization and intercalation of Fe₃O₄@PANI into the graphene oxide layers via π–π stacking interaction, followed by reduction of graphene oxide in the presence of hydrazine hydrate. In molecular imprinting process, the pre-polymers, including GSH as template molecule, Fe₃O₄@PANI/rGO nanocomposites as functional monomers and pyrrole as both cross-linker and co-monomer, was assembled through N–H hydrogen bonds and the electrostatic interaction, and then was rapidly oriented onto the surface of MGCE under the magnetic field induction. Subsequently, the electrochemical GSH sensor was formed by electropolymerization. In this work, the ternary Fe₃O₄@PANI/rGO nanocomposites could not only provide available functionalized sites in the matrix to form hydrogen bond and electrostatic interaction with GSH, but also afford a promoting network for electron transfer. Moreover, the biomimetic sensing membrane could be controlled more conveniently and effectively by adjusting the magnetic field strength. The as-prepared controllable sensor showed good stability and reproducibility for the determination of GSH with the detection limit reaching 3 nmol L⁻¹ (S/N = 3). In addition, the highly sensitive and selective biomimetic sensor has been successfully used for the clinical determination of GSH in biological samples.     

Molecularly imprinted polymers (MIPs) combined with nanomaterials as electrochemical sensing applications for environmental pollutants

It is known that environmental pollution, which is the result of human-induced industrial, domestic, and agricultural practices, poses a threat to our planet. The increasing human population caused several problems such as water and air pollution, which have reached levels threatening human health. There are many different hazardous chemical and biological environmental pollutants in soil, air, and wastewater. It is extremely important to evaluate these health risks and detect these pollutants. The use of electrochemical methods for the detection of environmental pollutants comes to the forefront recently with advantages such as sensitivity, fast response, low cost, and practical use by miniaturization. The molecular imprinting technique is a popular method used for substance analysis by creating a cavity specific to the substance to be analyzed with the polymer used. The use of molecularly imprinted polymer in electrochemical methods and its modification with various nanomaterials bring advantages such as high selectivity, robustness, and sensitivity to electrochemical sensors. Here, the sensitive determination of environmental pollutants with different nanomaterial-modified molecularly imprinted polymer-based electrochemical sensors, the use of different polymerization techniques, and nano-sized modification agents in sensors are evaluated by reviewing recent studies in the literature.     

Recent advances in electrochemical sensors for antibiotics and their applications

The abuse of antibiotics will cause an increase of drug-resistant strains and environmental pollution,which in turn will affect human health.Therefore,it is important to develop effective detection techniques to determine the level of antibiotics contamination in various fields.Compared with traditional detection methods,electrochemical sensors have received extensive attention due to their advantages such as high sensitivity,low detection limit,and good selectivity.In this mini review,we summarized the latest developments and new trends in electrochemical sensors for antibiotics.Here,modification methods and materials of electrode are discussed.We also pay more attention to the practical applications of antibiotics electrochemical sensors in different fields.In addition,the existing problems and the future challenges ahead have been proposed.We hope that this review can provide new ideas for the development of electrochemical sensors for antibiotics in the future.     

Computational design and multivariate optimization of an electrochemical metoprolol sensor based on molecular imprinting in combination with carbon nanotubes

This work describes the development of an electrochemical sensor based on a new molecularly imprinted polymer for detection of metoprolol (MTP) at ultra-trace level. The polypyrrole (PPy) was electrochemically synthesized on the tip of a pencil graphite electrode (PGE) which modified whit functionalized multi-walled carbon nanotubes (MWCNTs). The fabrication process of the sensor was characterized by cyclic voltammetry (CV) and the measurement process was carried out by differential pulse voltammetry (DPV). A computational approach was used to screening functional monomers and polymerization solvent for rational design of molecularly imprinted polymer (MIP). Based on computational results, pyrrole and water were selected as functional monomer and polymerization solvent, respectively. Several significant parameters controlling the performance of the MIP sensor were examined and optimized using multivariate optimization methods such as Plackett–Burman design (PBD) and central composite design (CCD). Under the selected optimal conditions, MIP sensor was showed a linear range from 0.06 to 490 μmol L⁻¹ MTP, a limit of detection of 2.88 nmol L⁻¹, a highly reproducible response (RSD 3.9%) and a good selectivity in the presence of structurally related molecules. Furthermore, the applicability of the method was successfully tested with determination of MTP in real samples (tablet, and serum).     

A facile approach for synthesizing molecularly imprinted graphene for ultrasensitive and selective electrochemical detecting 4-nitrophenol

In this work, a novel and convenient strategy was developed to prepare molecularly imprinted polymers (MIPs) on the surface of graphene sheet. In this route, vinyl group functionalized graphene (GR/NVC) was first prepared by immobilizing 4-vinylcarbazole onto the surface of graphene via π–π interaction. The subsequent grafting copolymerization of methacrylic acid and ethylene glycol dimethacrylate in the presence of 4-nitrophenol (4-NP, template molecule) was carried out at GR/NVC surface, leading to the formation of GR/MIPs composite. The GR/MIPs composite was characterized by FTIR, fluorescence, TGA, SEM and AFM, and was used to fabricate electrochemical sensor for the detection of 4-NP. The electrochemical behavior of GR/MIPs sensor for 4-NP was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The effects of the preparation conditions, such as concentration of the NVC and template, the solution pH, and incubation time, were also optimized. Under optimized conditions, the DPV current response of GR/MIPs sensor was nearly 12 times than that of the GR/NIPs sensor. It also should be noted that as compared to traditional MIP, shorter response time and much higher current response were demonstrated. In addition, the GR/MIPs sensor could recognize 4-NP from its structural analogs, indicating the excellent selectivity of the GR/MIPs sensor. The peak current is linearly proportional to the concentration of 4-NP ranging from 0.01 μM to 100 μM and 200 μM to 1000 μM with a significantly low detection limit of 5 nM, a wider response range and lower detection limits as compared to most of the previously reported electrochemical sensors for 4-NP. Furthermore, the GR/MIPs sensor exhibits good stability with adequate reproducibility and has been successfully used to determine 4-NP in water samples.     

磁性石墨烯修饰辛基酚印迹传感器制备及应用研究

以辛基酚(4-OP)为模板分子,多巴胺为功能单体,采用电聚合技术在磁性石墨烯修饰碳电极表面制备对辛基酚具有高选择性与灵敏性的印迹电化学传感器。采用循环伏安法(CV)和差分脉冲伏安法(DPV)对此印迹传感器的电化学性能进行详细表征;采用扫描电子显微技术对修饰电极的形貌进行表征。结果表明,此印迹电化学传感器对辛基酚具有良好的特异识别性能。采用 DPV 法考察了孵化时间和洗脱溶剂对印迹传感器性能影响,结果表明,最佳孵化时间为14 min。此印迹电化学传感器的响应电流(△IR )与辛基酚在5.0×10-6~5.0×10-9 mol/ L 范围内浓度的负对数(-lgC)呈良好的线性关系,线性方程为△IR ( mA)=-0.25lgC(mol/ L)+2.35,检出限为3.64×10-10 mol/ L (S/ N=3)。此印迹电化学传感器对辛基酚具有良好的选择性和灵敏性,成功用于实际水样中辛基酚的检测,回收率为96.0%~104.0%。     

盐酸阿霉素分子印迹传感器的制备及识别特性

采用自组装以及电聚合的方法,在磷酸盐缓冲液(PBS)中以3,4-乙烯二氧噻吩(EDOT)为功能单体,盐酸阿霉素(DOX)为模板,在金电极表面电聚合制备DOX印迹敏感膜(MIPs),构建了一种选择性检测DOX的分子印迹电化学传感器.采用循环伏安法(CV)及交流阻抗法(EIS)对其性能进行了表征.优化实验条件后,在含0.005 mol/L K3[Fe(CN)_6]及0.1 mol/L KCl的PBS中,应用差分脉冲伏安法(DPV)测试了该传感器的响应性能.实验结果表明,该传感器检测DOX的线性范围为4.0×10~(-7)~1.0×10~(-6)mol/L,相关系数为0.9967,检出限(S/N=3)达6.5×10~(-8)mol/L;采用电化学洗脱法可使传感器再生,对DOX的测定具有良好重现性及稳定性;该传感器对于干扰物长春碱、放线菌素D及5-氟尿嘧啶有微弱的电流响应,显示出良好的选择性.将该传感器用于人体血样中盐酸阿霉素的分析,回收率为96.0%~106.7%,表明其具有潜在的实用价值.     

Recent advances in electrochemical sensors for the detection of 2, 4, 6-trinitrotoluene

2, 4, 6-Trinitrotoluene (TNT) is a frequently used explosive compound, and it easily gathers in soil and water during transportation, use, and storage. Except for the security issue, it also has high toxicity and mutagenic effect on the environment and all life forms. Thus, it is critical to develop high-efficiency sensing methods for the detection of TNT at trace levels with high sensitivity and selectivity. This brief review highlights the research progress of using electrochemical sensors to analyze TNT molecules in recent years. Specifically, this minireview mainly focuses on the recently developed nanostructured electrocatalysts and electrochemical methods combined with other techniques for electrochemical detection of TNT.     

分子印迹化学发光传感器在线检测牛肉与鸡肉组织中残留的磺胺嘧啶

以分子印迹作为识别体,制成高灵敏度和高选择性的化学发光传感器在线检测牛肉与鸡肉组织中残留的磺胺嘧啶。磺胺嘧啶作为靶分子,通过悬浮聚合制备了1～10μm的分子印迹聚合物。将分子印迹聚合物装入聚四氟乙烯管中,作为固相萃取柱,并联在八通阀上,用于在线选择吸附磺胺嘧啶。在最佳条件下,测得磺胺嘧啶线性范围7.0×10–9～9.0×10–7g/mL,方法的检出限为(3σ)2×10–10g/mL,11次平行测定3.0×10–8g/mL的磺胺嘧啶溶液的化学发光强度相对标准偏差为3.4%。方法能够用于检测肉类产品中残留的磺胺嘧啶。     

Molecularly Imprinted Poly-o-phenylenediamine Electrochemical Sensor for Entacapone

We have developed a molecularly imprinted polymer (MIP) electrochemical sensor for entacapone (ETC) based on an electropolymerised polyphenylenediamine (Po-PD) on a glassy carbon electrode (GCE) surface. The direct electropolymerisation of the o-phenylenediamine monomer (o-PD) was carried out with ETC as a template. The steps of electropolymerization process, template removal and binding of the analyte were tested by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) using [Fe(CN)₆]³⁻/[Fe(CN)₆]^{4 −} as a redox probe. The operation of the sensor has been investigated by differential pulse voltammetry (DPV). Under optimal experimental conditions, the response of the DPV was linearly proportional to the ETC concentration between 1.0×10⁻⁷ and 5.0×10⁻⁶ M ETC with a limit of detection (LOD) of 5.0×10⁻⁸ M. The developed sensor had excellent selectivity without detectable cross-reactivity for levodopa and carbidopa. The MIP sensor was successfully used to detect ETC in spiked human serum samples.