Surface Of Glassy Carbon Electrode Research Articles

A Sensitive Electrochemical Aptamer Sensor for Clenbuterol Detection Based on Au NPs/Fe3O4–NH2/GN Nanocomposite

Chronic ingestion of food containing clenbuterol (CLB) in the human body can cause acute poisoning. Thus, it is essential to develop a sensitive CLB detection way. Here, a novel electrochemical aptamer sensor based on aptamer/gold nanoparticles/amino magnetic ferric oxide/graphene nanosheets (aptamer/Au NPs/Fe3O4–NH2/GN) nanocomposite has been developed. The Fe3O4–NH2 nanoparticles were self-assembled on GN, and then Fe3O4–NH2/GN nanocomposite was coated on the glassy carbon electrode (GCE) surface. Afterward, Au NPs were electrodeposited on Fe3O4–NH2/GN nanocomposite to fix the aptamer by the Au–S bonds. When CLB was added to the solution, the aptamer will specifically recognize CLB, causing current changes. Under the optimized conditions, the sensor shows better electrochemical performance (linear range is [Formula: see text][Formula: see text]M to [Formula: see text][Formula: see text]M, the detection limit is [Formula: see text][Formula: see text]M ([Formula: see text])). It has been successfully applied to the detection of CLB in actual samples. The results show that the aptamer sensor has good selectivity, stability and repeatability, which will provide a novel idea for more sensitive and quicker CLB detection.

Gold nanoparticle-mediated molecularly imprinted electrochemical sensor MIP/AuNPs/GCE for highly sensitive and selective detection of neutral phosmet residues in fruits and vegetables

A novel electrochemical sensor MIP/AuNPs/GCE was developed by depositing gold nanoparticles and electropolymerizing molecularly imprinted film on the surface of glassy carbon electrode (GCE) for highly sensitive detection of neutral phosmet residues in fruits and vegetables. Scanning electron microscopy, energy dispersive spectroscopy, atomic force microscopy, cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the imprinted sensor. The results showed that the imprinted film on GCE was evenly prepared with better specific recognition of phosmet on MIP/AuNPs/GCE than that on bare GCE. Several parameters including deposition time, functional monomer and its molar ratio, scanning cycles, and elution time were optimized in detail. The linear range of the MIP/AuNPs/GCE prepared in this work was 0.020–4.0 nmol/L with limit of detection of 0.010 nmol/L, which was much lower than MIP/GCE (0.17 nmol/L). The identification mechanism of MIP/AuNPs/GCE for phosmet was also confirmed as adsorption-diffusion model with effective surface area increasing after mediated by AuNPs. Selectivity, reproducibility and repeatability of the MIP/AuNPs/GCE were acceptable. The recovery of applying the sensor to detect PM in real samples ranged from 91.40 % to 107.3 %, which agreed well with those of HPLC. The method of developing MIP/AuNPs/GCE sensor herein could be extended to detecting other neutral pesticide residues in food and environment.

Mxene-derived Na2O7Ti3 nanoribbon as a promising electrode material for the detection of ethyl paraoxon in complex matrices

This study reports the development of MXene (Ti3C2Tx) derived sodium titanate nanoribbon-based electrochemical sensor for pesticide detection. Titanium Carbide (Ti3C2) MXene-derived sodium titanate nanoribbon (MNR) was obtained by facile hydrothermal synthesis and characterized by powder X-ray Diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray analysis(EDS) and, high-resolution transmission electron microscopy (HR-TEM). The synthesized water-dispersed MNR was stabilized with Nafion and deposited on the surface of glassy carbon electrodes (GCE), which provide a symmetrical uniform electrode surface. Further, the electrodes were electrochemically characterized with cyclic voltammetry (CV), differential pulse voltammetry (DPV), linear sweep voltammetry(LSV), and electrochemical impedance spectroscopy (EIS). The electrochemical sensing of ethyl paraoxon was carried out in 0.1 M phosphate buffer (PB) by CV, LSV, and DPV. The developed electrochemical sensor exhibited a limit of detection (LOD) of 0.22 nM, a very wide detection range from 0.69 nM to 174.03 nM, and a reliable sensitivity of 0.707 µA/nM/cm2. Moreover, the developed sensor was also employed for the detection of ethyl paraoxon in real samples (vegetable extract spiked with the pesticide). The results suggest that the developed MNR-based sensor would be a potential approach for efficient and accurate detection of ethyl paraoxon in ambient samples, with minimal interference.

A magnetically fixed bifunctional monomer molecularly imprinted electrochemiluminescence sensor for specifically identifying thiabendazole in food

A magnetically fixed bifunctional monomer molecularly imprinted electrochemiluminescence (ECL) sensor (MIP/MMOF@g-C3N4/L-Aas/MGCE) was constructed to selective detection thiabendazole (TBZ). Fe3O4 modified by sulfonic acid group (–SO3H) acted as magnetic core to attract Co2+ to initiate the growth of ZIF-67 (MMOF). Graphitic carbon nitride nanosheets (g-C3N4) were doped into MMOF by inherent amino groups to prepare integrated magnetic ECL luminophore (MMOF@g-C3N4). MMOF@g-C3N4 was immobilized on the surface of magnetic glassy carbon electrode (MGCE) by using the superparamagnetism of Fe3O4, which enhanced the stability and reusability of ECL system. Sodium ascorbate (L-Aas) acted as co-reactant accelerators to further enhance ECL intensity. MIP prepared with TBZ as template molecule and o-phenylenediamine (oPD)/resorcinol (RS) as bifunctional monomers contained more imprinting sites, which can enhance the adsorption performance. The luminescence mechanism of magnetic ECL system was investigated, and the specific recognition mechanism of MIP recognition system was deeply explored. The linear range of the method was 1 × 10−9–5 × 10−5 mol L−1, and the detection limit was 3.77 × 10−10 mol L−1. A good recovery rate (80.08%–96.82%) was obtained in the actual sample detection, which was basically consistent with the detection results of High Performance Liquid Chromatography.

A TALE OF CAPTOPRIL DETECTION BASED ON AN ELECTROCHEMICAL MIP SENSOR

Objective: In this study, it was aimed to develop a voltammetric method using sensors prepared with the molecular imprinting technique for the detection of Captopril, an antihypertensive drug. Material and Method: With the molecular imprinting method, molecularly imprinted polymers were formed on the surfaces of glassy carbon electrodes. The analysis of Captopril was carried out using the differential pulse voltammetry method, and the performance of the sensor was examined. Result and Discussion: A linear analysis was performed up to 50 pM Captopril with a limit of detection value of 2.62 pM. Selectivity studies have shown that Captopril has a higher electrochemical response than other interfering substances, such as paracetamol, ascorbic acid, and L-proline.

Near-infrared photoelectrochemical and colorimetric dual-mode aptasensor for determining osteopontin based on Er-MOF nanoballs@gold nanoparticles and Au2Pt nanozymes

A near infrared photoelectrochemical (PEC) and colorimetric dual-mode aptasensor was fabricated for efficiently determining osteopontin (OPN). Er-MOFs and Au2Pt nanoparticles were successfully synthesized. The gold nanoparticles (AuNPs) modified Er-MOF (Er-MOFs@AuNPs) nanocomposites were introduced into the glassy carbon electrode (GCE) to construct a photoelectrochemical sensing interface. OPN aptamer (Apt1) was immobilized onto the Er-MOFs@AuNPs based photoelectrochemical platform through Au-S bond for the selectively recognizing osteopontin. Au2Pt-labeled OPN aptamer (Au2Pt-Apt2) was subsequently captured onto the OPN/Apt1/MOFs@AuNPs/GCE surface to form a sandwich sensing interface, leading to an enhancement on the photocurrent response. Interestingly, Au2Pt nanozyme which possesses peroxidase activity could produce a solution color change in the presence of 3,3′,5,5′-tetramethylbenzidine (TMB) and hydrogen peroxide. The variations of photocurrent response and absorbance can be employed for the quantitative detection of OPN. Under the optimal conditions, the PEC and colorimetric sensing strategies show linear responses towards OPN in the concentration range of 0.01 ∼ 25 ng mL−1 and 1 ∼ 850 ng mL−1, respectively. The calculated determination limits were 2.6 pg mL−1 and 0.04 ng mL−1. The PEC and colorimetric dual-mode sensing platform can provide no crosstalk results and can be mutually verified, thus effectively improving the accuracy and reliability for the determination of OPN.

Investigation of Electrochemical Properties and Behaviors of NBITEP Molecule; Availability of Sensor Electrode in Determination of Hg2+ with SWAdSV Technique

This Master's Thesis focuses on the synthesis and structural elucidation of 4-(2-((6-nitro-1h-benzo[d]imidazol-2-yl)thio)ethyl)phenol (NBITEP) molecule, along with its electrochemical behaviors. Electrochemical studies were carried out employing a glassy carbon (GC) electrode as the working electrode. The cyclic voltammetry (CV) technique was utilized for modification and characterization processes. Furthermore, the potential of the modified surface as a sensor electrode for Hg2+ ion detection was investigated using square wave adsorptive stripping voltammetry (SWAdSV). Detailed examinations were conducted in a phosphate buffer solution (PBS) medium specifically for Hg2+ ion detection, demonstrating the suitability of the reduced NBITEP modified GC electrode surface as a sensor electrode.

Efficient oxidation of hydrazine over electrochemically activated glassy carbon electrode surface: Kinetics and sensing performance

Hazardous chemical hydrazine (HZ) can enter the body through the skin and harm the kidneys and liver. Consequently, it is imperative to accurately determine HZ concentrations in samples. One significant challenge in the direct and sensitive detection of analytes is the higher oxidation overpotential and inferior voltammetric response over the conventional bare electrode surface, attributed to the passivation of the electrode surface. To address this issue, we electrochemically activated (oxidized) a pristine glassy carbon electrode (GCE) in a mild acidic medium. The activated GCE demonstrated improved HZ oxidation efficiency. The activated GCE exhibited a distinct redox pair in 0.1 M H2SO4 because of the growth of C=O groups onto the electrode surface during electrochemical oxidation. We characterized the GCE surface before and after the functionalization using electrochemical processes, Scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). This activated electrode surface was utilized for electrochemical HZ oxidation in an alkaline medium, revealing enhanced electrochemical performance compared to the pristine GCE regarding HZ oxidation following conventional Butler-Volmer kinetics. Thorough electrochemical analyses and characterizations of the sensor were performed utilizing techniques such as Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), Open Circuit Potential (OCP), Chronoamperometry (i-t curve), and Differential Pulse Voltammetry (DPV). The correlation between the current response and HZ concentration displayed an extensive linear dynamic range (LDR) spanning from 6 to 1000 μM, boasting a limit of detection (LOD) at 0.48 μM. The sensor's sensitivity was determined to be 3.1 μA μM−1 cm−2. The proposed activated GCE effectively reduces HZ oxidation overpotentials, thereby enhancing its potential application as an anode in direct hydrazine fuel cells.

Tailoring electrochemical properties of hydrogel by different types of graphene oxide

In this study, different concentrations of graphene oxides prepared according to Brodie’s and Hummers’ method (GOB and GOH, respectively) were integrated with mixture of citric acid and hydroxyethyl cellulose (HEC-CA). This three-component solution could be easily coated on glassy carbon electrode surface and thermally crosslinked, forming solid films of nanohybrid hydrogels (HEC-CA-GOB and HEC-CA-GOH). The coated electrodes were characterized by different electrochemical techniques, which revealed that, compared to GOB, GOH significantly hindered diffusion of electroactive species to the electrode surface. Furthermore, application of the electrodes coated with HEC-CA-GOB and HEC-CA-GOH as voltammetric detectors of toxic metals and histamine was investigated. For the former, a low amount (0.075 mg mL−1) of GOB in HEC-CA enhanced the voltammetric response towards Pb2+ and Cu2+ up to 6.5 and 10 times, respectively while effect of GOH was less sound. In histamine detection, 1 mg mL−1 GOB or GOH in HEC-CA improved the response of the electrodes towards the histamine by approximately 25 % and improved antifouling properties of the sensors. As a conclusion, adjusting of GO content in the hydrogel was shown as an interesting and facile tool for preparation of electrodes with wide range of properties adjustable such as to meet requirements of various applications.

Oxidative Stripping of Starch-AgNPs for Nanomolar Indirect Electrochemical Sensing of BSA Using an L-Cysteine Modified Glassy Carbon Electrode

In this study, an L-cystine-modified glassy carbon electrode (GCE) was developed as an electrochemical platform based on AgNP oxidative stripping for nanomolar indirect detection of bovine serum albumin (BSA) biomacromolecules. The Poly-L-Cys was formed by L-cysteine (L-Cys) monomers electro-polymerization on the GCE surface. L-Cys pending groups interacted with AgNPs through Ag-S chemical bonds while it interacted with BSA through van der Waals forces and hydrogen bonding. To characterize the bare GCE and GCE/L-Cys, cyclic voltammetry and electrochemical impedance spectroscopy were used. The oxidative stripping of AgNPs by the addition of BSA was monitored using linear sweep stripping analysis.

The relevance of the initial conditions in glassy carbon electrode sensing applications: the ferri/ferrocyanide redox reaction model system in aqueous solution

Carbon electrodes, especially the glassy carbon electrodes (GCE) are widely accepted as very versatile sensing platforms. However, correlating the behaviour of the ferri/ferrocyanide redox couple ([Fe(CN)6]3-/4−) with the GCE's surface modification is challenging. The surface modification can be achieved by applying a pre-conditioning electrochemical activation procedure. Hence, we report the investigation performed in order to provide further insights into the electrochemical behaviour of the commonly used redox probe in aqueous solutions. To that aim we took advantage of powerful and complementary electrochemical analytical techniques, like cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Thus, this work highlights the critical role of the GCE initial conditions for optimizing the charge transfer processes and therefore to improve the [Fe(CN)6]3-/4− performance in sensing applications. The best results were obtained in phosphate buffer saline solution with previous electrochemical activation by fast potential cycling between [-0.5 and +1.8] V (vs. Ag|AgCl (KCl sat.)). Finally, one can consider this an eco-friendly and simple procedure to be carried out in the lab, however, its use must be carefully optimized when exploring other systems, as highlighted herein.

Exploring the potential of SrTi0.7Fe0.3O3 perovskite/Chitosan nanosheets for the development of a label-free electrochemical sensing assay for determination of naproxen in human plasma samples

Naproxen is a nonsteroidal anti-inflammatory drug used to treat nonrheumatic inflammation, migraine, and gout. Therefore, the determination of naproxen in pharmaceutical and biological samples is of particular importance. In the present work, SrTi0.7Fe0.3O3 perovskite/Chitosan nanosheets were used to modify the surface of a glassy carbon electrode (GCE) for highly sensitive determination of naproxen. To ensure the successful synthesis of the perovskite nanosheets, morphological studies including scanning electron microscopy (SEM), Energy-dispersive X-ray (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) were carried out. The electrochemical investigations of naproxen on the modified surface of GCE were investigated and the limit of detection (LOD) and limit of quantification (LOQ) were acquired 0.50 and 1.67 μM, respectively. Additionally, the linear range (LR) of 1.99–130.84 μM was obtained for the oxidation of naproxen. The obtained results have been proved that the mentioned method is simple, sensitive, and specific with a short analysis time. The dominant analytical features of the designed sensor are possessing a low detection limit, excellent stability, repeatability, and high selectivity in the presence of naproxen. For investigation of the applicability of the designed assay in real sample analysis, human plasma samples have been examined and a recovery index was acquired 95%.

Label-free electrochemical sensing platform for sensitive detection of ampicillin by combining nucleic acid isothermal enzyme-free amplification circuits with CRISPR/Cas12a

The residue of ampicillin (AMP) in food and ecological environment poses a potential harm to human health. Therefore, a reliable system for detecting AMP is in great demand. Herein, a label-free and sensitive electrochemical sensor utilizing NH2–Co-MOF as an electrocatalytic active material for methylene blue (MB) was developed for rapid and facile AMP detection by combining hybridization chain reaction (HCR), catalytic hairpin assembly (CHA) with CRISPR/Cas12a. The surface of glassy carbon electrode modified with NH2–Co-MOF was able to undergo HCR independent of the AMP, forming long dsDNA complexes to load MB, resulting in strong original electrochemical signal. The presence of AMP could trigger upstream CHA circuit to activate the CRISPR/Cas12a system, thereby achieving rapid non-specific cleavage of the trigger ssDNA of HCR on the electrode surface, hindering the occurrence of HCR and reducing the load of MB. Significant signal change triggered by the target was ultimately obtained, thus achieving sensitive detection of the AMP with a detection limit as low as 1.60 pM (S/N = 3). The proposed sensor exhibited good stability, selectivity, and stability, and achieved reliable detection of AMP in milk and livestock wastewater samples, demonstrating its promising application prospects in food safety and environmental monitoring.

Three-dimensional cage based on porous Ni–Co–Cu phosphide as efficient and stable bifunctional electrocatalysts for overall water splitting

The development of cheap and high-performance dual electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in an electrolyte is of great importance. Tuning the electronic structure through heteroatom doping and increasing the catalytic sites through designing the morphology of nanostructures are the most popular approaches to enhance electrocatalytic performance. In recent years, with the development of nanotechnology and interface engineering, significant progress has been made in this field, but it is still challenging. Here three-dimensional porous NiCoCu–P cage were synthesized using a quick and easy method with the help of 26-face Cu2O as a sacrificial template, then it was phosphidated by a facile phosphidation heat treatment in N2 atmosphere and then for the electrochemical evaluations, the glassy carbon electrode surface (GCE) surface was modified with it. Taking advantage of these strategies, NiCoCu–P cage offer large surface area, fast electron/mass transfer and open channels for efficient gas release, which show improved electrochemical performance in alkaline environment and achieved an overpotential of −210 mV at 10 mA cm−2 for HER and 240 mV at 50 mA cm−2 for OER. Also, an overall water splitting device is assembled by two symmetric NiCoCu–P cage/carbon cloth as cathode and anode, that can provide a current density of 100 mA cm−2 at a cell voltage of less than 1.6 V.

Electrochemical Sensor Based on Electrodeposited Zinc-Aluminium Layered Double Hydroxide Modified Glassy Carbon Electrode for Chlorpromazine Sensing

Chlorpromazine functions as a potent dopamine D2 receptor antagonist, leading to adverse motor-related effects encompassing cataracts, musculoskeletal disorders, alterations in eyelid pigmentation, muscle contractions, and tremors-addressing the need for a reliable analytical tool, an electrodeposited thin film was synthesized on a glassy carbon electrode (GC) surface. This film comprised zinc-aluminium layered double hydroxide (Zn-Al LDH), with nitrate ions intercalated between the LDH layers. The electrocatalytic behavior of the resulting electrode (GC/Zn-Al LDH) in the oxidation and reduction of nitrogen and sulfur atoms within the thiazine ring structure of chlorpromazine was systematically studied using cyclic voltammetry. Evaluation of the electrode’s analytical response through diverse electroanalytical techniques demonstrated that the square wave voltammetry-assisted electrochemical sensor displayed a broad detection range for chlorpromazine (1 × 10−4 to 1 mM), with a sensitivity of 91.86 μA mM−1 and an impressive low detection limit of 16 × 10−6 mM. Furthermore, the performance of the developed electrode was assessed in detecting and quantifying chlorpromazine levels in simulated human urine samples through recovery studies. The results indicated satisfactory recovery rates, affirming the efficacy of the Zn-Al LDH-modified GC electrode. Noteworthy features of the electrochemical sensor included high surface coverage, improved electron transfer rate, reliable repeatability, and exceptional reproducibility. These characteristics collectively contribute to the sensor’s popularity for accurately detecting and quantifying of chlorpromazine in real-world samples.

Efficient Amperometric Detection of Ornidazole: An Antibiotic Drug Based on Rare-Earth Metal Oxide Entrapped with Graphene Nanosheets Nanocomposite

The use of nitro aromatic compounds for the treatment of protozoal infections as well as anaerobic bacteria is widespread. The global use of antiprotozoal drugs causes significant ecological impact on living systems. In this study, electrochemical detection of the antiprotozoal drug ornidazole (ODZ) was demonstrated through neodymium oxide/graphene nanosheets (Nd2O3/GNS) based electrocatalyst. This hybrid material was prepared with a sonochemical probe method. We characterized the Nd2O3/GNS nanocomposite using various analytical and spectroscopic techniques. For rapid ODZ drug determination, we used Nd2O3/GNS nanocomposite-based slurry to modify the glassy carbon electrode (GCE) surface. The electrocatalysis of ODZ using Nd2O3/GNS/GCE showed a good linear range (0.01–221 μM), excellent detection limit (0.001 μM), and high sensitivity, along with long-term stability. The practicality of the sensor electrode for ODZ was successfully determined in water and human urine samples, yielding satisfactory recoveries. Thus the results indicated that Nd2O3 with conductive carbon support including graphene, carbon nanotubes (CNT), carbon nanofibers, etc., can be used as a sensitive sensor electrode for the real-time detection of antibiotic drugs that cause human and environment by continuous consumption and improper disposal from the pharmaceutical industries, respectively.

Magnetic nanoparticles-based electrochemical aptasensor for the detection of enrofloxacin in chicken

Enrofloxacin (ENR) is widely applied in preventing and treating animal diseases and hence directly passed into animal-derived foods. Therefore, the detection of this drug in food samples must be strengthened to ensure food safety. In this work, a simple, sensitive electrochemical aptasensor for the detection of ENR was fabricated by using magnetic nanoparticles (MNPs) as carriers. The ENR aptamer was modified on the surface of MNPs to capture the ENR target or a biotin-complementary strand and then recognize streptavidin-horse radish peroxidase. Subsequently, the resulting MNPs were easily transferred onto the surface of magnetic glassy carbon electrode with the help of its integral magnet. Under optimal experimental conditions, a linear relationship between the variable of LSV current and the logarithm of ENR concentration in the range of 0.01–100 ng/mL was obtained with the limit of detection at 4.9 pg/mL. In addition, this method exhibited good stability, selectivity, reproducibility and was successfully applied in detecting ENR in spiked chicken samples with recoveries of 100.70%–108.96%. The proposed method is easy to fabricate and process; it is particularly suitable for food sample pretreatment and is beneficial in removing the interference of a complex matrix.

Fabrication of an affordable and sensitive corticosteroid-binding globulin immunosensor based on electrodeposited gold nanoparticles modified glassy carbon electrode

Herein, we fabricated an ultrasensitive electrochemical immunosensor for the quantitative detection of corticosteroid-binding globulin (CBG). CBG is a protein that regulates glucocorticoid levels and is an important biomarker for inflammation. A decrease in CBG levels is a key biomarker for inflammatory diseases, such as septic shock. To enhance the electrochemical performance and provide a large surface area for anti-CBG immobilization, we functionalized the glassy carbon electrode surface with AuNPs. Electrochemical characterization methods including cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to examine the construction of the fabricated immunosensor. The electrochemical signal demonstrated a remarkable sensitivity to the CBG antigen, with a detection range from 0.01 to 100 μg/mL and a limit of detection of 0.012 μg/mL, making it suitable for both clinical and research applications. This label-free immunosensor offers significant advantages, including high sensitivity, low detection limits and excellent selectivity, making it a promising tool for detecting CBG in complex biological samples. Its potential applications include early disease diagnosis, treatment monitoring and studying CBG-related physiological processes.

Polycarboxyl ionic liquid functionalized Yb-MOFs nanoballs based dual-wavelength responsive photoelectrochemical aptasensor for the simultaneous determination of AFB1 and OTA

Developing an accurate and precise approach for the simultaneous detection of ochratoxin A (OTA) and aflatoxin B1 (AFB1) is significant for food safety surveillance. Herein, a photoelectrochemical sensing platform was constructed based on polycarboxylic ionic liquid functionalized metal-organic framework integrated with gold nanoparticles (Yb-MOFs@AuNPs). Sulfhydryl functionalized hairpin DNA (hDNA) was immobilized on a Yb-MOFs@AuNPs modified glassy carbon electrode (GCE) surface through Au-S bond. After blocking residual active binding sites with BSA, gold nanoparticles-labeled AFB1 aptamer (AuNPs-Apt 1) and gold nanorods-labeled OTA aptamer (AuNRs-Apt 2) were introduced to construct a photoelectrochemical aptasensor for the simultaneous determination of AFB1 and OTA. Due to the surface plasmon resonance effect and the nanometer size effect of gold nanomaterials, the photoelectrochemical aptasensor can output photocurrent responses as being excited with different wavelengths at 520 nm and 808 nm, respectively. When the AFB1 and OTA concentration in the range of 0.001–50.0 ng mL−1, a good linear relationship between the photocurrent difference (ΔI) before and after recognizing targets and the logarithm of AFB1 or OTA concentration was obtained. The detection limits for AFB1 and OTA were 0.40 pg mL−1 and 0.19 pg mL−1, respectively. AFB1 and OTA in corn samples were detected simultaneously by the photoelectrochemical aptasensor.

Modification of Glassy Carbon Electrodes with Complexes of Manganese(II) with Some Phenanthroline Derivatives Immobilized in Nafion Layer.

Manganese(II) complexes with phenanthroline derivatives modified with different substituents were synthesized and incorporated into Nafion layers covering the surfaces of glassy carbon electrodes and were studied electrochemically. Formal potentials and apparent diffusion coefficients were calculated and discussed. The suitability for electrocatalytic oxidation of ascorbic acid and glycolic acid was examined. The surfaces of modified electrodes were characterized using atomic force microscopy.