Electropolymerization Cycles Research Articles

Modification of rGO/ZIF-68 Based on Molecularly Imprinted Polymer Electrochemical Sensor for Detection of Acetamiprid

Molecular imprinting (MIP) is one of the most efficient strategies used to provide recognition materials with continuous good selectivity, commonly employed in electrochemical sensors as recognition elements or modifier agents[1]. In this study, a highly sensitive Molecularly Imprinted Polymer (MIP) sensor was developed and successfully utilized for acetamiprid recognition. The MIP was decorated onto the surface of a zeolitic imidazolate framework (ZIF-68) and reduced graphene oxide (rGO) composite modified with a glassy carbon electrode (GCE) to fabricate the GCE/rGO/ZIF-68/MIP electrode. Spectroscopic and microscopic analyses such as XRD, FT-IR, XPS, and SEM were employed to evaluate the composition and morphology of the surface of the GCE/rGO/ZIF-68/MIP electrode. The electrochemical characterization of the electrodes was performed using cyclic voltammetry (CV), Squarewave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS). Additionally, different parameters influencing the sensitivity of GCE/rGO/ZIF-68/MIP, such as the percentage of rGO, template:monomer ratio, number of electropolymerization cycles, pH, extraction and incubation time were optimized. Under optimal conditions, the MIP sensor exhibited a wide linear range, low detection limit, as well as good reproducibility, stability, and selectivity, and it was successfully used for the determination of pesticide in real solutions. The sensor was applied to real samples for the acetamiprid pesticide, and successful recovery values were obtained. Keywords: Electrochemical sensor; Molecularly imprinted polymer (MIP); Acetamiprid.

An epitope imprinted electrochemical sensor for highly sensitive and selective determination of prostate-specific antigen.

Asimple method forhighly selective and sensitive prostate-specific antigen (PSA) detection using a molecularly imprinted electrochemical sensor ispresented. The sensor was developed through an epitope imprinted strategy combined with electrochemical measurement techniques. An epitope molecularly imprinted polymer (EMIP) film was constructed on a AuNPs-coated gold electrode surface through electropolymerization, utilizing the C-terminus epitope of PSA (KWIKDTIVANP) as the template molecular and o-phenylenediamine as the functional monomer. The characteristics of EMIP film were investigated by using a scanning electron microscope and electrochemical test methods, including electrochemical impedance spectroscopy and cyclic voltammetry. Key parameters such as electropolymerization cycles, elution and rebinding times, and the molar ratio of template molecular to functional monomer were systematically optimized. The sensor demonstrated a detection limit (LOD) of 0.31 fg/mL and exhibited an excellent linear response towards PSA concentration ranging from 1.0 fg/mL to 0.1 µg/mL. Furthermore, the EMIP sensor showed excellent selectivity against other biological macromolecules, such as bovine serum albumin, human serum albumin, alpha-fetoprotein, and carcinoembryonic antigen. With recoveriesbetween 95.89 and 106.04% for PSA detection in human serums theEMIP/AuNPs/AuE electrochemical sensor showed great potential in real sample analysis.

Innovative Molecularly Imprinted Electrochemical Sensor for Selective Nanomolar Detection of the Anti-COVID-19 Medication Molnupiravir

For the first time, a green ecofriendly approach is applied, to develop a molecularly imprinted polymer (MIP) electrochemical for the assay of the oral anti-viral molnupiravir (MLN) in various matrices as confirmed by referring to analytical eco-scale, green analytical procedure index (GAPI), Raynie and Driver, analytical greenness metric (AGREE), and national environmental index (NEMI). AuNPs were chronoamperometry deposited on the glassy carbon electrode surface (GCE) using 0.01 gm ml−1 gold solution (HAuCl4.3H2O) in 0.5 M H2SO4 at a constant potential of −0.4 V for 60 s. Then, the MIP was created by electropolymerizing OPDA on the surface of AuNPs GCE using cyclic voltammetry in the potential range between −0.5 and +1 V for 15 cycles (scan rate: 50 mV.s−1). To optimize the sensor’s performance, factors such as number of electropolymerization cycles, template: monomer ratio, binding and rebinding time, pH of rebinding buffer, extraction solvent, deposition time of Au nanoparticles, order of deposition on the electrode; surface, as well as differential pulse voltammetry parameters including accumulation potential and time, and potential step, were all investigated. The detection limit was set at 0.00098 ng ml−1 (3 × 10−12M) and the linearity range of MLN was between 0.033 ng ml−1 and 164 ng ml−1 (1 × 10−10–5 × 10−7 M). The MIP sensor was employed for MLN determination in its pharmaceutical product (capsules), spiked human plasma, and human urine samples with mean recovery % ± mean relative standard deviation (RSD) (99.82% ± 0.53), (99.88% ± 0.62), and (97.90% ± 0.70), respectively. The investigated sensor provided good reproducibility, repeatability, and durability. Acceptable selectivity regarding MLN when mixed with structurally comparable compounds was proved with mean recovery % ± mean RSD (97.10% ± 0.03). Additionally, when molnupiravir was exposed to oxidative, hydrolytic, and thermal stress conditions, good results in stability-indicating studies served as an indicator of sensor selectivity. The developed electrode is coupled with a portable potentiostat, making it a promising point-of-care diagnostic platform for on-site measurements.

Disposable Molecularly Imprinted Polymer-Modified Screen-Printed Electrodes for Rapid Electrochemical Detection of l-Kynurenine in Human Urine.

l-Kynurenine (l-Kyn) is an endogenous metabolite produced in the catabolic route of l-Tryptophan (l-Trp), and it is a potential biomarker of several immunological disorders. Thus, the development of a fast and cheap technology for the specific detection of l-Kyn in biological fluids is of great relevance, especially considering its recent correlation with SARS-CoV-2 disease progression. Herein, a disposable screen-printed electrode based on a molecularly imprinted polymer (MIP) has been constructed: the o-Phenylenediamine monomer, in the presence of l-Kyn as a template with a molar ratio of monomer/template of 1/4, has been electropolymerized on the surface of a screen-printed carbon electrode (SPCE). The optimized kyn-MIP-SPCE has been characterized via cyclic voltammetry (CV), using [Fe(CN)6)]3-/4- as a redox probe and a scanning electron microscopy (SEM) technique. After the optimization of various experimental parameters, such as the number of CV electropolymerization cycles, urine pretreatment, electrochemical measurement method and incubation period, l-Kyn has been detected in standard solutions via square wave voltammetry (SWV) with a linear range between 10 and 100 μM (R2 = 0.9924). The MIP-SPCE device allowed l-Kyn detection in human urine in a linear range of 10-1000 μM (R2 = 0.9902) with LOD and LOQ values of 1.5 and 5 µM, respectively. Finally, a high selectivity factor α (5.1) was calculated for l-Kyn toward l-Trp. Moreover, the Imprinting Factor obtained for l-Kyn was about seventeen times higher than the IF calculated for l-Trp. The developed disposable sensing system demonstrated its potential application in the biomedical field.

Electropolymerization of Polydopamine at Electrode-Supported Insulating Mesoporous Films.

Bioinspired, stimuli-responsive, polymer-functionalized mesoporous films are promising platforms for precisely regulating nanopore transport toward applications in water management, iontronics, catalysis, sensing, drug delivery, or energy conversion. Nanopore technologies still require new, facile, and effective nanopore functionalization with multi- and stimuli-responsive polymers to reach these complicated application targets. In recent years, zwitterionic and multifunctional polydopamine (PDA) films deposited on planar surfaces by electropolymerization have helped surfaces respond to various external stimuli such as light, temperature, moisture, and pH. However, PDA has not been used to functionalize nanoporous films, where the PDA-coating could locally regulate the ionic nanopore transport. This study investigates the electropolymerization of homogeneous thin PDA films to functionalize nanopores of mesoporous silica films. We investigate the effect of different mesoporous film structures and the number of electropolymerization cycles on the presence of PDA at mesopores and mesoporous film surfaces. Our spectroscopic, microscopic, and electrochemical analysis reveals that the amount and location (pores and surface) of deposited PDA at mesoporous films is related to the combination of the number of electropolymerization cycles and the mesoporous film thickness and pore size. In view of the application of the proposed PDA-functionalized mesoporous films in areas requiring ion transport control, we studied the ion nanopore transport of the films by cyclic voltammetry. We realized that the amount of PDA in the nanopores helps to limit the overall ionic transport, while the pH-dependent transport mechanism of pristine silica films remains unchanged. It was found that (i) the pH-dependent deprotonation of PDA and silica walls and (ii) the insulation of the indium-tin oxide (ITO) surface by increasing the amount of PDA within the mesoporous silica film affect the ionic nanopore transport.

The development, validation, and optimization of a SWAdSV method for the simultaneous determination of epinephrine and uric acid in real samples using a poly(L-cysteine) modified SPCE sensor

This work demonstrates the development, optimization, and method validation of a square-wave adsorption stripping voltammetry (SWAdSV) method for the simultaneous determination of epinephrine (EP) and uric acid (UA) using a poly(L-cysteine) (pLC) film modified screen-printed carbon electrode (pLC-SPCE). The pLC film was deposited by the electropolymerization of L-cysteine (LC). The successful deposition of pLC was confirmed by time-of-flight secondary ion mass spectrometry. A comparison was made between a bare SPCE and a pLC-SPCE for the analysis of EP and UA. In order to improve the electroanalytical performance of the pLC-SPCE sensor, the parameters of the square-wave (SW) technique, such as amplitude, frequency, and potential step, as well as the pH of the 0.1 M PBS solution, the concentration of the LC, the number of cycles for electropolymerization, the deposition potential, and the deposition time, were optimized. Subsequently, the SWAdSV method was validated for the limit of detection (LOD), the limit of quantification (LOQ), the linear concentration range, accuracy, and precision. The method had a very low LOD and LOQ, i.e. 10.0 µg/L and 19.8 µg/L for both analytes, respectively. Two linear concentration ranges were obtained, i.e. from 49.0 µg/L to 326.1 µg/L and from 326.1 µg/L to 887.1 µg/L, for both analytes. The average recoveries and the relative standard deviations for both analytes were in a range from 94.4% to 108.4% (n = 6) and from 2.6% to 11.7% (n = 6), respectively, at the four EP and UA concentration levels tested. In addition, the effect of possible interferents, such as glucose, L-ascorbic acid, K+, Cl–, Ca2+, SO42–, Mg2+, NH4+, C2O42–, and urea on the SW signal of EP and UA, were investigated. However, none of these compounds significantly affected the performance of the electroanalytical method. Finally, the applicability of the pLC-SPCE sensor was successfully demonstrated for the analysis of a pharmaceutical sample (an EP auto–injector) and human urine, proving accurate and precise analysis using the developed sensor.

Bio-Inspired Molecularly Imprinted Polymer Electrochemical Sensor for Cortisol Detection Based on O-Phenylenediamine Optimization.

This paper presents a comprehensive investigation of the various parameters involved in the fabrication of a molecularly imprinted polymer (MIP) sensor for the detection of cortisol. Parameters such as monomer concentration, electropolymerization cycles, pH, monomer-template ratio, template removal technique, and rebinding time were optimized to establish a more consistent and effective method for the fabrication of MIP sensors. Under the optimized conditions, the MIP sensor demonstrated a proportional decrease in differential pulse voltammetry peak currents with increasing cortisol concentration in the range of 0.1 to 100 nM. The sensor exhibited excellent sensitivity, with a limit of detection of 0.036 nM. Selectivity experiments using a non-imprinted polymer sensor confirmed the specific binding affinity of the MIP sensor for cortisol, distinguishing it from other steroid hormones. This study provides crucial insights into the development of a reliable and sensitive strategy for cortisol detection using O-PD-based MIPs. These findings laid the foundation for further advancements in MIP research.

Development of Levo-Lansoprazole Chiral Molecularly Imprinted Polymer Sensor Based on the Polylysine-Phenylalanine Complex Framework Conformational Separation.

The efficacies and toxicities of chiral drug enantiomers are often dissimilar, necessitating chiral recognition methods. Herein, a polylysine-phenylalanine complex framework was used to prepare molecularly imprinted polymers (MIPs) as sensors with enhanced specific recognition capabilities for levo-lansoprazole. The properties of the MIP sensor were investigated using Fourier-transform infrared spectroscopy and electrochemical methods. The optimal sensor performance was achieved by applying self-assembly times of 30.0 and 25.0 min for the complex framework and levo-lansoprazole, respectively, eight electropolymerization cycles with o-phenylenediamine as the functional monomer, an elution time of 5.0 min using an ethanol/acetic acid/H2O mixture (2/3/8, V/V/V) as the eluent, and a rebound time of 10.0 min. A linear relationship was observed between the sensor response intensity (ΔI) and logarithm of the levo-lansoprazole concentration (l-g C) in the range of 1.0 × 10-13-3.0 × 10-11 mol/L. Compared with a conventional MIP sensor, the proposed sensor showed more efficient enantiomeric recognition, with high selectivity and specificity for levo-lansoprazole. The sensor was successfully applied to levo-lansoprazole detection in enteric-coated lansoprazole tablets, thus demonstrating its suitability for practical applications.

An Electrochemical Sensor Based on Electropolymerization of β-Cyclodextrin on Glassy Carbon Electrode for the Determination of Fenitrothion.

An electrochemical sensor enabled by electropolymerization (EP) of β-cyclodextrin on glassy carbon electrode (β-CDP/GCE) is built for the determination of fenitrothion (FNT). The effects of the EP cycles, pH value, and enrichment time on the electrochemical response of FNT were studied. With the optimum conditions, good linear relationships between the current of the reduction peak of the nitroso derivative of FNT and the concentration are obtained in the range of 10-150 and 150-4000 ng/mL, with a detection limit of 6 ng/mL (S/N = 3). β-CDP/GCE also exhibits a satisfactory applicability in cabbage and tap water, with recovery values between 98.43% and 112%. These outstanding results suggest that β-CDP/GCE could be a new effective alternative for the determination of FNT in real samples.

Simultaneous determination of anthracene and phenanthrene using a poly-alizarin red S/carbon paste electrode

A polymer-based carbon paste electrode was constructed by electropolymerized Alizarin Red S (ARS) film on the carbon paste electrode (CPE) surface. The electrochemical properties of poly-ARS/CPE were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM) was utilized for electrode characterization. The electropolymerization cycles for the construction of the sensor and the supporting electrolyte were optimized. With 0.1 M LiClO4 as a supporting electrolyte, poly-ARS/CPE was able to generate oxidation peaks for anthracene (ANT) and phenanthrene (PHE), that were clearly defined and easily distinguished from one to another when operating in square wave voltammetry (SWV). In the simultaneous detection the linear ranges of ANT and PHE were within 80–1000 μM, with detection limits of 24 μM. The variation of peak parameters with scan rate was investigated to determine the nature of electrooxidation and the number of electrons involved in the electrode process. Poly-ARS/CPE was successfully utilized for the detection of ANT and PHE in different water samples and the obtained results suggested the selectivity, stability and reproducibility of the modified electrode.

Electrochemically based targeted metabolomics for uric acid, xanthine, and hypoxanthine in plasma samples for early diagnosis of acute renal failure after cardiopulmonary bypass using rGO-GCE

Cardiopulmonary bypass (CPB) may cause a systemic inflammatory reaction in patients during cardiac surgery due to the interaction of blood with heart-lung machine circuits. This inflammation may lead to organ failure. One of the most severe complications of cardiac surgery is the development of acute renal failure (ARF). Early diagnosis of ARF using fast, accurate, and sensitive methods may prevent ARF development. Therefore, we developed and validated an electroanalytical method for simultaneous analysis of three biomarker candidates, uric acid (UA), hypoxanthine (HXA), and xanthine (XA), from plasma samples. Their quantification was performed using reduced graphene oxide modified glassy carbon electrode (rGO-GCE) synthesized through rapid one-step electropolymerization. The characterization studies of rGO-GCE with cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscope (SEM) analyses showed a successful surface modification of GCE with rGO. The electrochemical oxidations of the biomarkers were examined using square wave voltammetry (SWV) with the rGO sensor in 0.1 M phosphate-borate (PB) buffer (pH 7). Various operational parameters, including pH and type of supporting electrolyte, instrumental parameters, electro polymerization cycles, and GO concentration, were optimized. Under optimum conditions, good linear responses were obtained for three metabolites (R2 > 0.99). The LOQ of the method was 0.12 μM for UA, 0.13 μM for XA, and 0.43 μM for HXA. The developed method was successfully applied to patient plasma samples of ARF (n = 9) and control (n = 17) collected at five-time points of CPB. The UA, HXA, and XA levels were significantly altered in ARF patients. The results showed the applicability of the developed method for early diagnosis of ARF developed after CPB.

Voltammetric sensor for COVID-19 drug Molnupiravir on modified glassy carbon electrode with electrochemically reduced graphene oxide

• There are no published reports for electrochemical determination of Molnupiravir in any matrix. • The first electrochemical validated, sensitive, cheap, easy and fast method for determination of Molnupiravir in pharmaceutical preparations. • Reduced GO has excellent conductivity, thermal and chemical stability for sensor application. A direct, simple, and sensitive method based on electrochemical deposition of reduced graphene oxide (rGO) on a glassy carbon electrode (GCE) using cyclic voltammetry (CV) was developed for Molnupiravir (MOL) quantitative analysis. Here, the electrochemical oxidation of MOL was examined using square wave voltammetry (SWV) and a well-defined peak at 0.2 V was measured against the Ag/AgCl reference electrode with the rGO sensor in Britton-Robinson pH 9 buffer. Various operational parameters for MOL analysis such as pH of supporting electrolyte, instrumental parameters, electropolymerization cycles, and GO concentration were optimized. The sensor exhibited a linear range from 0.09 to 4.57 μM with a detection limit of 0.03 µM. The electrochemical response of the rGO sensor was characterized by electrochemical impedance spectroscopy and CV. The character of current and reversibility of the electrode reaction, the number of electrons and protons transferred were studied by the CV method. The developed sensor was validated according to the International Council for Harmonisation (ICH) guidelines. Validation parameters, such as stability, linearity, sensitivity, accuracy, precision, recovery, robustness and ruggedness were evaluated according to the ICH requirements. The developed sensor was successfully applied for the quantification of MOL in capsule formulations.

A novel electrochemical sensor based on molecularly imprinted polymer nanocomposite platform for sensitive and ultra-selective determination of citalopram

• A novel sensing platform based on MIP/hNiNS/AMWCNT@GONRs composite was designed as the modifier for GCE. • For the first time the modified glassy carbon electrode (MIP/hNiNS/AMWCNT@ GONRs/GCE) was used to determine citalopram (CIT). • The sensor showed excellent selectivity and sensitivity towards determination of CIT. • The proposed sensor was applied successfully for determination of CIT in real samples. Citalopram (CIT) is an antidepressant of the selective serotonin reuptake inhibitor class widely used worldwide, so the development of analytical methods to determine it in real samples is essential for treatment purposes and drug development. This work presented an electrochemical-specific sensor for CIT based on the molecular imprinting technique. The sensor was fabricated by electropolymerizing molecularly imprinted polymer (MIP) film onto hollow nickel nanospheres (hNiNS)/activated multiwalled carbon nanotubes@graphene oxide nanoribbons (AMWCNTs@GONRs) composite modified glassy carbon electrode (GCE). The excellent synergistic effect of the combination of hNiNS and AMWCNTs@GONRs composite shows significantly enhanced electrocatalytic activity for CIT, which lead to high sensitivity of the sensor. The electropolymerized MIP provides specific imprinted sites, which can increase the selectivity for CIT. The preparation of the MIP/hNiNS/AMWCNT@GONRs/GCE was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and electrochemical methods, including cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical properties of the sensor were studied using differential pulse voltammetry (DPV) and CV. Main effective parameters on the performance of the imprinted electrodes such as electropolymerization cycles, pH buffer solution, incubation time and concentrations of template molecules were checked and optimized. The fabricated sensor displayed two linear dynamic ranges from 0.5 to 10 µM and 10 to 190 µM with a limit of detection (LOD, S/N = 3) of 0.042 µM. Examining the interfering effect of some structurally related compounds and some potential interferences existing in biological fluids on the analysis of citalopram showed that the designed MIP sensor could identify CIT selectively. Moreover, the constructed electrode exhibited good repeatability, reproducibility, stability and rapid response time for the electrochemical analysis of CIT. The presented sensor was successfully utilized for determining the CIT in real samples.

Molecularly imprinted polypyrrole film-coated poly(3,4-ethylenedioxythiophene):polystyrene sulfonate-functionalized black phosphorene for the selective and robust detection of norfloxacin

An efficient molecularly imprinted polymer (MIP) voltammetric sensor was prepared based on polypyrrole (PPy) imprinted film-bearing poly(3,4-ethylenedioxythiophene):polystyrene sulfonate-functionalized black phosphorene (BP-PEDOT:PSS) for the selective recognition and robust determination of norfloxacin. BP-PEDOT:PSS was prepared via a simple ultrasonic-assisted liquid-phase exfoliation as an efficient support for use in MIP electrochemical sensors. The imprinted PPy film was deposited onto the surface of BP-PEDOT:PSS via the potentiodynamic technique in the presence of norfloxacin, with the imprinting factor of 3.86 for norfloxacin. The morphologies and microstructures of the sensing materials were investigated using scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, and Raman spectroscopy. Additionally, parameters including the BP-PEDOT:PSS loading volume, norfloxacin:pyrrole molar ratio, electropolymerization cycles, template removal, solution pH, and time of electrode exposure to the analyte were optimized. Under optimal conditions, the response peak currents of norfloxacin correlated linearly to norfloxacin concentrations from 0.001 to 10 μM, with a limit of detection of 0.25 nM. The prepared imprinted sensor could effectively distinguish norfloxacin from other fluoroquinolone antibiotics with the selectivity coefficients of 5.4–17.3 and maintained stable, robust voltammetric responses for up to two weeks. Moreover, it successfully detected norfloxacin in pharmaceutical formulations and milk samples.

Molecularly imprinted sensor based on 1T/2H MoS2 and MWCNTs for voltammetric detection of acetaminophen

1T phase molybdenum disulfide (MoS2) possesses excellent electrical conductivity, 107 times higher than that of 2H phase MoS2. Thus, metallic 1T MoS2 is highly desirable for electrochemical analysis and catalysis. In this study, hybrid 1T/2H MoS2/multi-walled carbon nanotubes (MoS2/MWCNTs) composite was prepared by a facile and simple hydrothermal approach. Powder X-ray diffraction, field emission scanning and transmission electron microscopes, Fourier transform infrared spectroscopy, Raman spectroscopy, cyclic voltammetry (CV), and electrochemical impedance spectroscopy were used to characterize the composites. The results show that metallic 1T phase MoS2 was formed by the inductive effect of MWCNTs. The high conductivity and large specific surface area of hybrid 1T/2H MoS2/MWCNTs composite endow great catalysis activity in electrochemical analysis. Polypyrrole molecularly imprinted polymer (MIP) film imprinted with acetaminophen (AP) template was electrochemically deposited on glassy carbon electrode (GCE) modified by 1T/2H MoS2/MWCNTs (MoS2/CNTs/GCE) to construct MIP based sensor. The prepared MIP/MoS2/CNTs/GCE sensor shows a sensitive current response towards AP. Through the optimization of the ratio of monomer and template, CV electropolymerization cycles, CV elution cycles, incubation time, and pH, the accessible linear range of 0.01–300 μM was obtained with the limit of detection of 0.003 μM (S/N = 3) by differential pulse voltammetry. In addition, the prepared sensor shows great detecting robustness with excellent selectivity, anti-interference property, reproducibility, and stability. In the urine sample tests, the sensor shows desirable reliability with the recovery rate of 88.1–95.9%.

Electropolymerized Aniline-Based Stainless Steel Fiber Coatings Modified by Multi-Walled Carbon Nanotubes for Electroanalysis of 4-Chlorophenol.

In this paper, a stainless steel fiber coated electropolymerized aniline, without and with carbon nanotubes (SS/PANI and SS/PANI/CNT), along with CNTs modified carbon paste electrodes (CPEs), were prepared. The electrodes were characterized by differential pulse voltammetry (DPV) and applied for the detection of 4-chlorophenol (4-CP). For all the electrodes, the oxidative peak current showed a linear dependence on the 4-CP concentration in the range of 0.05–0.5 mmol/L with R2 ≥ 0.991. SS/PANI/CNT electrodes showed greater sensitivity for the detection of the 4-CP than the SS/PANI and CPEs. For all of the aniline-based stainless steel electrodes, both the LOD and LOQ decreased with the increase in the number of electropolymerization cycles. The lowest LOD (0.38 µmol/L) and LOQ (1.26 µmol/L) were observed for the SS/PANI/CNT electrode modified in aniline solution during 30 cycles. The methods were successfully applied to the analysis of 4-CP in real samples (tap water and river water). The results demonstrated the good agreement of the added and found concentrations of the 4-CP. The recovery and precision were from 95.12% to 102.24% and from 1.53% to 6.79%, respectively. The proposed electrodes exhibited acceptable reproducibility, admirable stability, and adequate repeatability and showed potential for the analysis of 4-CP in water.

Simultaneous analysis of catechol and hydroquinone by polymelamine/CNT with dual-template molecular imprinting technology

Dual-template molecularly imprinted polymer/carbon nanotubes/grassy carbon electrode (MIP/CNTs/GCE) was constructed by electropolymerizing a layer of bimolecular imprinted film with melamine (Mel) as functional monomer, hydroquinone (HQ) and catechol (CC) as template molecules on CNTs modified GCE. The morphology, structure and electrochemical properties of MIP/CNTs/GCE were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and electrochemical technology, respectively. The experimental parameters for the construction of sensor were optimized in detail, which includes the reagent molar ratio, the electropolymerization cycles, the elution time and the pH value of the electrolyte. Under the optimal conditions, the simultaneous detection of HQ and CC was realized via cyclic voltammetry (CV) and differential pulsed voltammetry (DPV). Compared with CNTs/GCE, molecularly imprinted membrane can significantly enhance its response current to HQ and CC. At the same time, both the linear range of HQ and CC measured by DPV are 10–100 μM, with the detection limits of 3.1 μM and 3.5 μM, respectively. The electrode also owned good reproducibility and stability. Finally, MIP/CNTs/GCE was successfully utilized for the detection of HQ and CC in river water.

Ternary Composite of Molybdenum Disulfide-Graphene Oxide-Polyaniline for Supercapacitor

The ever-increasing need for small and lightweight power sources for use in portable or wearable electronic devices has spurred the development of supercapacitors as a promising energy storage and conversion system. In this work, a simple, facile and easy-to-practice method has been developed to employ carbon paper (CP) as the support to coat molybdenum disulfide (MoS2) and graphene oxide (GO), followed by electrodeposition of polyaniline (PANI) to render CP/MoS2-GO-PANI. The preparation parameters, such as amounts of MoS2, GO and number of aniline electropolymerization cycles, have been optimized to render CP/MoS2-GO-PANI the best capacitive performance. The as-prepared optimal CP/MoS2-GO-PANI is characterized by X-ray powder diffraction, scanning electron microscopy, energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy. The supercapacitive properties of CP/MoS2-GO-PANI as an electrode have been evaluated electrochemically via cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy testing. CP/MoS2-GO-PANI delivers a specific capacitance of 255.1 F g−1 at 1.0 A g−1 and exhibits excellent rate capability under larger current densities. Moreover, a symmetrical supercapacitor is assembled and three are connected in series to power a light-emitting diode for ∼15 min, demonstrating the promising application potential of CP/MoS2-GO-PANI-based supercapacitor.

An electrochemical sensor for the determination of Luteolin using an alizarin red/carboxylic acid group functionalized carbon nanotube

A novel poly alizarin red (AR) film incorporating carboxylic acid group functionalized multiwall carbon nanotube (f-MWCNT) modified glassy carbon electrode (GCE) was first prepared for the determination of luteolin (Lut). Scanning and transmission electron microscopy were applied for characterization of the surface morphology of the modified electrodes and cyclic voltammetry was used to investigate the electrochemical properties of the proposed electrode towards the oxidation of Lut. Optimization of the experimental parameters was performed with regard to pH, drop-coating volume of f-MWCNT, electro-polymerization cycles of alizarin red, and different potentials of i-t. And the mechanism for Lut detection based on AR/f-MWCNT/GCE was investigated by electrochemical methods. The linearity between the oxidation peak current and the Lut concentration was obtained in the range of 0.5 to 45 μM with a detection limit of 0.17 μM (S/N = 3). In addition, the AR/f-MWCNT/GCE electrode displayed high selectivity, good stability and reproducibility, and also successfully determined Lut in drug samples.

Surfactant and Polymer Composite Modified Electrode for the Sensitive Determination of Vanillin in Food Sample

AbstractIn this work, the active poly (titan yellow) and octoxynol‐9 modified carbon nanotube paste electrode (PTOMCNPE) was prepared and characterized through a Field emission scanning electron microscope (FE‐SEM), Energy‐dispersive X‐ray spectroscopy (EDX), and Electrochemical impedance spectroscopy (EIS). PTOMCNPEpromotes the detection and quantification of vanillin (VA). The electrochemical parameters such as the number of electropolymerization cycles, effect of surfactant,pH, and scan rate were optimized to get an enhanced current signal for the targetmolecule. Under calibrated conditions, the concentration linearity for vanillin was obtained from 2.0‐40.0 μM using both cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The limitof detection(LOD) for VA was found to be 4.9×10−8 M and 9.31×10−8 M using DPV and CV, respectively. The stable and selective VA sensor was applied to food analysis with excellent recovery.