A novel electrochemical sensor based on molecularly imprinted polymers for caffeine recognition and detection

A sensitive and selective electrochemical sensor based on molecularly imprinted polymers (MIPs) was developed for caffeine (CAF) recognition and detection. The sensor was constructed through the following steps: multiwalled carbon nanotubes and gold nanoparticles were first modified onto the glassy carbon electrode surface by potentiostatic deposition method successively. Subsequently, o-aminothiophenol (ATP) was assembled on the surface of the above electrode through Au–S bond before electropolymerization. During the assembled and electropolymerization processes, CAF was embedded into the poly(o-aminothiophenol) film through hydrogen bonding interaction between CAF and ATP, forming an MIP electrochemical sensor. The morphologies and properties of the sensor were characterized by scanning electron microscopy, cyclic voltammetry, and differential pulse voltammetry. The recognition and determination of the sensor were observed by measuring the changes of amperometric response of the oxidation-reduction probe, [Fe(CN)₆]^3?/[Fe(CN)₆]^4?, on modified electrode. The results demonstrated that the prepared sensor had excellent selectivity and high sensitivity for CAF, and the linear range was 5.0?×?10^?10?~?1.6?×?10^?7?mol?L^?1 with a detection limit of 9.0?×?10^?11?mol?L^?1 (S/N?=?3). The sensor was also successfully employed to detect CAF in tea samples.     

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.     

Preparation and Application of Urea Electrochemical Sensor Based on Chitosan Molecularly Imprinted Films

A novel urea electrochemical sensor was constructed based on chitosan molecularly imprinted films which were prepared by potentiostatic electrodeposition of chitosan in the presence of urea followed by eluting with 0.1 M KCl. Various techniques were carried out to investigate the formation of molecularly imprinted polymer (MIP) films and the performance of the sensor. According to our expectation, the urea MIP electrochemical sensor showed excellent selectivity to urea among the structural similarities and co‐existences, high linear sensitivity to urea in the range from 1.0×10^?8 to 4.0×10^?5 M with a detection limit of 5.0×10^?9 M. Furthermore, the recovery ranged from 96.3 % to 103.3 % and therefore offered great potential for clinical diagnosis applications.     

Acetylene black paste electrode modified with molecularly imprinted polymers/graphene for the determination of bisphenol A

A novel nanocomposite of molecularly imprinted polymers and graphene sheets was fabricated and used to obtain a highly conductive acetylene black paste electrode with high conductivity for the detection of bisphenol A. The two‐dimensional structure and the chemical functionality of graphene provide an excellent surface for the enhancement of the sensitivity of the electrochemical sensor and the specificity of molecularly imprinted polymers to improve detection of bisphenol A. The synergistic effect between graphene and molecularly imprinted polymers confers the nanocomposite with superior conductivity, broadened effective surface area and outstanding electrochemical performance. Factors affecting the performance of the imprinted sensor such as molecularly imprinted polymers concentration, foster time and scan rate are discussed. The sensor successfully detects bisphenol A with a wide linear range of 3.21 × 10^?10 to 2.8 × 10^?1 g/L (R = 0.995) and a detection limit of 9.63 × 10^?11g/L. The fabricated sensor also possessed high selectivity and stability and exhibits potential for environmental detection of contaminants and food safety inspection.     

Molecularly Imprinted Electrochemical Luminescence Sensor Based on Enzymatic Amplification for Ultratrace Isoproturon Determination

A new molecularly imprinted electrochemical luminescence sensor (MIP‐ECL sensor) was developed for isoproturon (IPU) determination based on the competition reaction between IPU and glucose oxidase labeled IPU (GOD‐IPU). After competition, hydrogen peroxide produced by residual GOD‐IPU on the MIP reacted with luminol to emit electrochemiluminescence (ECL) signal. The ECL intensity decreased when the GOD‐IPU molecules were replaced by IPU molecules in the samples. IPU could be determined in the concentration range from 9×10^?11 mol/L to 5.1×10^?9 mol/L with a detection limit of 3.78×10^?12 mol/L. Water samples were assayed and recoveries ranging from 98.5 % to 102.1 % were obtained.     

Determination of Oxytetracycline with a Gold Electrode Modified by Chitosan-Multiwalled Carbon Nanotube Multilayer Films and Gold Nanoparticles

A molecularly imprinted electrochemical sensor was fabricated based on a gold electrode modified by chitosan-multiwalled carbon nanotube composite (CS-MWCNTs) multilayer films and gold nanoparticles (AuNPs) for convenient and sensitive determination of oxytetracycline (OTC). The multilayer of CS-MWCNTs composites and AuNPs were used to augment electronic transmission and sensitivity. The molecularly imprinted polymers (MIPs) were synthesized using OTC as the template molecule and o-phenylenediamine (OPD) as the functional monomer. They were modified on a gold electrode by electropolymerization. The electrochemical behavior of OTC at the imprinted sensor was characterized by cyclic voltammetry (CV), scanning electron microscopy (SEM), and amperometry. The molecularly imprinted sensor showed high selectivity and excellent stability toward OTC. The linear range was from 3.0 × 10^?8 to 8.0 × 10^?5 mol/L, with a limit of detection (LOD) of 2.7 × 10^?8 mol/L (S/N = 3). The developed sensor showed good recovery in spiked samples analysis.     

A Polypyrrole‐Imprinted Electrochemical Sensor Based on Nano‐SnO2/Multiwalled Carbon Nanotubes Film Modified Carbon Electrode for the Determination of Oleanolic Acid

A sensitive molecularly imprinted electrochemical sensor with specific recognition ability for oleanolic acid was synthesized by modification of multiwalled carbon nanotubes (MWNTs) decorated with tin oxide nanoparticles (nano‐SnO₂/MWNTs) and polypyrrole‐imprinted polymer on a carbon electrode. The morphology and electrochemical performance of the imprinted sensor were investigated by using scanning electron microscope (SEM), X‐ray diffraction (XRD), cyclic voltammetry (CV), linear sweep voltammetry (LSV) and amperometric i–t curve. The results showed that the imprinted sensor displayed excellent selectivity toward oleanolic acid. A linear relationship between the response currents and oleanolic acid concentrations ranging from 5.0×10^?8 g/L to 2.0×10^?5 g/L was obtained for the imprinted sensor. The limit of detection (LOD) of the imprinted sensor toward oleanolic acid was calculated as 8.6×10^?9 g/L at a signal to noise ratio (S/N) of 3. This imprinted sensor was successfully applied to the determination of oleanolic acid in Acitinidia deliciosa root samples.     

A Study of Preparation and Performance of a Dichlorvos Electrochemical Sensor Based on Molecularly Imprinted Technique

A new dichlorvos molecularly imprinted electrochemical sensor was prepared. The sensitive membrane sensor was fabricated by electro-polymerizing on an Au electrode surface using o-aminophenol as a monomer and dichlorvos as a template. The 5 mmol/L K₃[Fe(CN)₆] containing 0.1 mol/L KCl was used as the test background solution, while cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to study the properties of the senor. The changes of oxidation peak current versus dichlorvos concentration showed linearity in the range of 0.12–0.42 µmol/L (R ² = 0.9432) and 0.45–15 µmol/L (R ² = 0.9516) with a detection limit of 0.06 µmol/L (S/N = 3). Moreover, the selectivity and repeatability properties of the dichlorvos electrochemical sensor were examined. Results showed that the senor had excellent repeatability (RSD = 3.92%, n = 5), good selectivity to the dichlorvos in detection, and only a ten minute response time. Organophosphorus insecticides have some response signals in the detections.     

Electrochemical Sensor for trans‐Resveratrol Determination Based on Indium Tin Oxide Electrode Modified with Molecularly Imprinted Self‐Assembled Films

A voltammetric sensor for sensitive and specific determination of trans‐resveratrol (RES) were prepared based on immobilization of an RES‐imprinted film on the surface of functionalized Indium Tin Oxide (ITO) electrode, which was modified with γ‐methacyloxypropyl trimethoxysilane (γ‐MPS). Cyclic Voltammetry (CV) was presented to extract RES from the molecularly imprinted polymer film and RES were extracted rapidly and completely. The binding performance of the imprinted electrode with the template RES were investigated using differential pulse voltammetry (DPV). The results showed that the imprinted ITO film can give selective recognition to the template RES over that of structurally analogous molecules. A linear response to RES in the concentration range of 2.0×10^?6 M to 2.0×10^?5 M was observed with a correlation coefficient of 0.992, and the detection limit of the electrochemical sensor was 8.0×10^?7 M. Whereas, binding to the reference nonimprinted electrode, made in the same way but without the addition of template RES, there was almost no response to RES.     

Selective Electrochemical Determination of Dopamine with Molecularly Imprinted Poly(Carbazole‐co‐Aniline) Electrode Decorated with Gold Nanoparticles

Dopamine (DA) is a significant neurotransmitter in the central nervous system, coexisting with uric acid (UA) and ascorbic acid (AA). UA and AA are easily oxidizable compounds having potentials close to that of DA for electrochemical analysis, resulting in overlapping voltammetric response. In this work, a novel molecularly imprinted (MI) electrochemical sensor was proposed for selective determination of DA (in the presence of up to 80‐fold excess of UA and AA), relying on gold nanoparticles (Au_nano)‐decorated glassy carbon (GC) electrode coated with poly(carbazole (Cz)‐co‐aniline (ANI)) copolymer film incorporating DA as template (DA imprinted‐GC/P(Cz‐co‐ANI)‐Au_nano electrode, DA‐MIP‐Au_nano electrode). The DA recognizing sensor electrode showed great electroactivity for analyte oxidation in 0.2 mol L^?1 pH 7 phosphate buffer. Square wave voltammetry (SWV) was performed within 10^?4–10^?5 mol L^?1 of DA, of which the oxidation peak potential was observed at 0.16 V. The limit of detection (LOD) and limit of quantification (LOQ) were 2.0×10^?6 and 6.7×10^?6 mol L^?1, respectively. Binary and ternary synthetic mixtures of DA‐UA, DA‐AA and DA‐UA‐AA yielded excellent recoveries for DA. Additionally, DA was quantitatively recovered from a real sample of bovine serum spiked with DA, and determined in concentrated dopamine injection solution. The developed SWV method was statistically validated against a literature potentiodynamic method using a caffeic acid modified‐GC electrode.     

Highly Sensitive Molecularly Imprinted Sensor Based on Platinum Thin‐film Microelectrode for Detection of Chloramphenicol in Food Samples

A highly sensitive and selective electrochemical biomimetic sensor was fabricated for fast detection of chloramphenicol (CAP) in honey and milk samples. Platinum thin‐film microelectrode (Pt TFME), which could provide unique electrochemical properties and achieve measurement using very limited solution volumes, was surface‐modified by electropolymerizing o‐phenylenediamine. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the preparation process of CAP‐imprinted poly(o‐phenylenediamine) film and rebinding ability of CAP into the imprinted cavities. The electrochemical properties of the sensor were further investigated with square wave voltammetry (SWV) by using K₃Fe(CN)₆ as an electroactive probe. The current difference of oxidation peaks of K₃Fe(CN)₆ had a good linear relationship with the concentration of CAP in the range of 0.9–10 nM. The detection limit was 0.39 nM based on the signal to noise ratio of 3. The developed sensor was successfully applied to determine CAP in honey and milk samples, and the result was in good agreement with that obtained by high performance liquid chromatography‐mass spectrometry (HPLC‐MS). The sensor showed high sensitivity and excellent selectivity to CAP in comparison to other structurally related and/or normally existing antibiotics, and demonstrated great promise for the rapid quantification of CAP in real food samples and field analysis.     

Selective Electrochemical Determination of Salicylic Acid in Wheat Using Molecular Imprinted Polymers

Salicylic acid is a phytohormone, playing crucial roles in signal transduction, crop growth, and development, and defense to environmental challenges. In this study, a highly selective electrochemical sensor was designed and used to determine salicylic acid using molecularly imprinted polymers for recognition. The electrochemical sensor was fabricated via stepwise modification of gold nanoparticle–graphene–chitosan and molecularly imprinted polymers on a glassy carbon electrode. With electrochemical deposition, a gold nanoparticle–graphene–chitosan film was deposited on the glassy carbon electrode and enhanced the sensitivity. Molecularly imprinted polymers with adsorbed template salicylic acid were added to the surface of the modified electrode. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the modified electrodes. Salicylic acid in wheat was quantified by the sensor using the molecularly imprinted polymer/gold nanoparticle–graphene–chitosan/glassy carbon electrode. Concentrations of salicylic acid from 5?×?10^?10 to 5?×?10^?5?mol?L^?1 were determined showing that the developed sensor was suitable for the analysis of food.     

基于抗原决定基的胰岛素分子印迹电化学传感器

采用抗原决定基法制备了胰岛素电化学分子印迹传感器.以胰岛素C端多肽作为模板分子,定向自组装在Au电极上,以邻苯二胺为功能单体,电化学聚合制备分子印迹聚合膜.以NaOH为洗脱液,洗脱模板分子,形成的与胰岛素C端多肽三维结构相匹配的分子印迹孔穴能特异性识别胰岛素.重吸附胰岛素分子后,以K3[Fe(CN)6]/K4[Fe(CN)6]为探针,通过测量探针在电极表面产生的电流大小实现胰岛素的间接测定.在1.0 × 10-14~5.0 × 10-13 mol/L浓度范围内,传感器的电流响应值与胰岛素浓度呈良好的线性关系,检出限为7.24 × 10-15 mol/L(3σ).此传感器具有较好的选择性和稳定性,并成功用于血清样品中胰岛素的测定.     

Construction of a novel electrochemical sensor based on molecularly imprinted polymers for the selective determination of chlorpyrifos in real samples

We present a novel electrochemical sensor based on an electrode modified with molecularly imprinted polymers for the detection of chlorpyrifos. The modified electrode was constructed by the synthesis of molecularly imprinted polymers by a precipitation method then coated on a glassy carbon electrode. The surface morphology of the modified electrode was characterized by using field‐emission scanning electron microscopy and transmission electron microscopy. The performance of the imprinted sensor was thoroughly investigated by using cyclic voltammetry and differential pulse voltammetry. The imprinted electrochemical sensor displayed high repeatability, stability, and selectivity towards the template molecules. Under the optimal experimental conditions, the peak current response of the imprinted electrochemical sensor was linearly related to the concentration of chlorpyrifos over the range 1 × 10⁻¹⁰–1 × 10⁻⁵ mol/L with a limit of detection of 4.08 × 10⁻⁹ mol/L (signal‐to‐noise ratio = 3). Furthermore, the proposed molecularly imprinted electrochemical sensor was applied to the determination of chlorpyrifos in the complicated matrixes of real samples with satisfactory results. Therefore, the molecularly imprinted polymers based electrochemical sensor might provide a highly selective, rapid, and cost‐effective method for chlorpyrifos determination and related analysis.     

基于分子印迹电聚合膜的褪黑素传感器的研究

在弱酸条件下,以邻苯二胺为功能单体,褪黑素为模板,以电化学聚合物法在铂电极表面合成了性能稳定的褪黑素分子印迹聚合物膜.采用循环伏安法(CV)和差分脉冲法(DPV)对分子印迹传感器的识别性能进行了研究.结果表明:此传感器对褪黑素具有快的响应、良好的选择性和高的灵敏度.以K3Fe(CN)6为电子传递媒介,建立了一种差分脉冲伏安法(DPV)间接检测褪黑素的分析方法.在1×10-10～1×10-8 moL/L范围内,褪黑素的浓度与K3Fe(CN)6的相对峰电流变化呈良好的线性关系;检出限为1×10-11 mol/L(S/N=3).将此传感器应用于复合褪黑素及尿样中褪黑素含量的测定,加标平均回收率大于94％.     

Microspheres Sensor Based on Molecularly Imprinted Polymer Synthesized by Precipitation Polymerization

IntroductionSincethepiezoelectricbulkacousticwave (BAW)sen sorswereappliedinliquidphaseinthe 1980s ,manypapershavebeenreported .1,2 However,theapplicationofBAWsen sorsbasedonmasseffectislimitedbecauseoflackofthespecialselectivitytotheanalyte.Variousmethodshavebeenproposedtosolvethisproblem ,especiallytheapplicationofthebiomaterials .3Unfortunately ,theresultwasnotsogoodasexpected,duetotheinstinctdisadvantageofthebiomateri als ,e.g .,poorstability ,shortlifespan ,althoughpossess inghighselec…     

Using an Electrochemical MIP Sensor for Selective Determination of 1-Naphthol in Oilfield Produced Water

A molecularly imprinted polymer (MIP) sensor was successfully constructed on glassy carbon electrode for the determination of 1-naphthol (1-Nph). The sensor was constructed by electropolymerization on bare GCE in the presence of the target molecule. The recognition of 1-Nph was conducted indirectly using [Fe(CN)₆]^3−/4− as redox probe. The MIP sensor presented wide linear working range and limit of detection of 1.5×10⁻⁹ mol L⁻¹. The MIP sensor was applied for the determination of 1-Nph in oilfield produced water. The results obtained showed good selectivity and sensitivity of the proposed sensor in terms of 1-Nph quantification.     

Electrochemical Conversion of Magnetic Nanoparticles Using Disposable Working Electrode in a 3D‐Printed Electrochemical Cell

Exploration of new property/function of nanomaterials is always a strong impetus in the nanoscience field. Here, a new method of electrochemical conversion (ECC) of magnetic nanoparticles (MNPs) is proposed to endow MNPs with signal generation ability for sensing. Briefly, high potential was applied to split H₂O to generate acid, while Fe₃O₄ MNPs reacted with H⁺ and produce ferric/ferrous ions, which further reacted with K₄Fe(CN)₆ to yield Prussian blue (PB) through potential cycling. The ECC method worked well on both home‐made and commercial MNPs with different sizes. The generated PB possessed strong electrochemical activity for further applications. Interestingly, an uneven deposition of PB on working electrode and undesired contamination of the reference and counter electrodes were found when using commercial integrated three‐electrode chip. A 3D‐printed electrochemical cell was designed to facilitate the ECC and avoid drawbacks of commercial integrated electrode. The 3D‐printed electrochemical cell was proven to solve the problem above through spatial separation of electrodes and thus facilitated the ECC process. An electrochemical sensor for H₂O₂ detection based on the catalysis ability of ECC‐based PB exhibited a linear response from 5 μM to 1 mM, a high sensitivity of 269 μA mM^?1 cm^?2 and a low detection limit of 0.16 μM (S/N=3), which suggests its promising application prospect in electrochemistry‐related analysis.     

Investigating Electrochemical Stability and Reliability of Gold Electrode‐electrolyte Systems to Develop Bioelectronic Nose Using Insect Olfactory Receptor

This article aims to demonstrate an electrochemically stable and reliable gold electrode‐electrolyte system to develop an insect odorant receptor (Drosophila melanogaster Or35a) based bioelectronic nose. Cyclic voltammograms (CVs) and electrochemical impedance spectroscopy (EIS) of bare gold electrodes, after modification with the self‐assembled monolayer (SAM) of 6‐mercaptohexanoic acid (MHA) and after immobilization with Or35a integrated into the lipid bilayers of liposomes were conducted in the presence of four different redox probes. Potassium ferri/ferrocyanide [Fe(CN)₆]^3?/[Fe (CN)₆]^4? and hydroquinone (H₂Q) redox probes revealed variable and irreversible signals at the time scale of our measurements, with atomic force microscopy (AFM) images and x‐ray photoelectron spectroscopy (XPS) results suggesting gold surface etching due to the presence of CN^? ions in case of [Fe(CN)₆]^3?/[Fe (CN)₆]^4?. Although the hexaammineruthenium complex showed stable electrochemical behaviour at all stages of biosensor development, changes in CV and EIS readings after each surface modifications were insignificant. PBS buffer as a non‐Faradaic medium, was found to provide reliable systems for electrochemical probing of modified gold electrodes with Or35a/liposomes in aqueous media. Using this system, we have shown that this novel biosensor can detect its known odorant E2‐hexenal selectively compared to methyl salicylate down to femtomolar concentration.     

Imprinted Azorubine electrochemical sensor based upon composition of MnO<Subscript>2</Subscript> and 1-naphthylamine on graphite nanopowder

A new sensitive and selective molecularly imprinted electrochemical sensor was developed for Azorubine determination. This sensor was based on molecularly imprinted polymer composed of poly(1-naphthylamine), triphenylamine (as cross-linkers) and dispersed MnO₂ nanorod particles on graphite nanopowders. The structure of the prepared nanocomposite was characterized by X-ray powder diffraction, energy-dispersive X-ray spectroscopy, field emission scanning electron microscopy, transmission electron microscopy and Fourier transform infrared spectroscopy. Calibration curve of the imprinted sensor was linear in the concentration range 1–12 mg L^??1 with a detection limit of 0.57 mg L^??1. The application of the sensor was checked by the determination of Azorubine in a water sample.