Oxidation Peak Research Articles

Simultaneous Hg2+ and Pb2+ detection in water samples using an electrochemical aptasensor with dual signal amplification by exonuclease III and metal-organic frameworks

Heavy metal pollution in the environment has become a significant global concern due to its detrimental effects on human health and the environment. In this study, we report an electrochemical aptasensor for the simultaneous detection of Hg2+ and Pb2+. Gold nanoflower/polyethyleneimine-reduced graphene oxide (AuNFs/PEI-rGO) was introduced on the surface of a gold electrode to improve sensing performance. The aptasensor is based on the formation of a T-Hg2+-T mismatch structure and specific cleavage of the Pb2+-dependent DNAzyme, resulting in a dual signal generated by the Exo III specific digestion of methylene blue (MB) labeled at the 3′ end of probe DNA-1 and the reduction of the substrate ascorbic acid (AA) catalyzed by the signal label. The decrease of MB signal and the increase of AA oxidation peak was used to indicate the content of Hg2+ and Pb2+, respectively, with detection limits of 0.11 pM (Hg2+) and 0.093 pM (Pb2+). The aptasensor was also used for detecting Hg2+ and Pb2+ in water samples with good recoveries. Overall, this electrochemical aptasensor shows promising potential for sensitive and selective detection of heavy metals in environmental samples.

Electroanalytical analysis of phenol oxidation using bacteria immobilized by a polycaprolactone coating on the copper electrode surface

The copper electrode modified by bacteria immobilised by a polycaprolactone film was successfully developed by electropolymerisation for the purpose of determining the presence of phenol. Electrochemical techniques such as square-wave voltammetry (SWV), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the electrochemical properties of the Cu-polymer/bacteria electrode. The results show that the intensity of the phenol oxidation peak increases with concentration, allowing us to obtain good analytical results with DL of 2.156 × 10–7 M and QL which is 7.2 × 10–7 M , confirming that the biosensor has excellent electroanalytical activity for phenol oxidation, with good stability and a wide linear range. Our electrode is based on a easily available and inexpensive material, as well as on its simple preparation, which has demonstrated high performance for phenol.

A Novel Poly(cytosine)-Based Electrochemical Biosensor for Sensitive and Selective Determination of Guanine in Biological Samples.

The novel poly(cytosine)-modified glassy carbon electrode-based electrochemical sensor was fabricated potentiodynamically for the detection of Guanine (G) in clinical and biological samples. The surface of the electrode was successfully activated by electropolymerization, and about a 7.5-fold current improvement due to modification was achieved. From the analysis of the dependence of peak current and peak potential on a scan rate, a higher R 2 for the peak current on the square root of scan rate (R 2 = 0.999) than the dependence of peak current on scan rate (R 2 = 0.982) indicated that the oxidation of G at poly(cytosine)/GCE was predominantly diffusion controlled. The oxidative peak response of the electrode revealed a high linear range of G concentration (0.1-200 μM) under optimized conditions. The detection limit and limit of quantification were 6.10 and 20.13 nM, respectively, associated with the %RSD of under 1%. The validation of the developed electrochemical sensor for the determination of G was investigated by analyzing human urine DNA and serum samples with spike recovery results in the range of 98.20-103.70% with the interferent recovery percentage in the range of 97.86-103.10% containing 50-300% of potential interferents. The newly designed sensor demonstrated the highest level of performance for the G detection in real samples.

Novel Hybrid Copper-Based Electrode for Non-Enzymatic Electrochemical Lactic Acid Sensing in Milk Samples

A novel developed non-enzymatic electrochemical sensor was designed for the detection of lactic acid (LA) in perishable products, with a focus on monitoring milk spoilage. The sensor utilizes a hybrid copper-based electrode consisting of cuprous oxide (Cu2O), copper oxide (CuO), and copper hydroxide (Cu(OH)2), which collectively contribute to enhanced performance through their synergistic effects. Cyclic voltammetric studies revealed distinct oxidation peaks associated with LA detection, highlighting the superior catalytic effect of the Cu2O/CuO/Cu(OH)2 electrode compared to CuO alone. Further optimization of the metal loading on the electrode surface led to improve LA sensing properties. The sensor exhibited a wide linear response range (0.25–7 mM), high sensitivity (817.66 μA·mM−1·cm−2), and a low limit of detection (0.25 mM). Selectivity tests indicated negligible interference from common dairy product constituents, while stability tests showed consistent performance over a 3 week storage period (100% stability). The practical usability of the sensor was demonstrated through the quantitative analysis of LA in pasteurized milk, with recovery values ranging from 99.7% to 106.9%, confirming the feasibility of the sensor for real sample analysis. The developed multiphase copper-based electrode presents a promising platform for the sensitive and reliable detection of LA within the dairy industry.

Enhanced Cadmium Sensing in Fertilizer Samples using Zeolite-modified Graphite Electrode

The presence of heavy metals in fertilizers poses significant environmental and health risks, necessitating robust detection methods to ensure agricultural sustainability and food safety. This study focuses on synthesizing Na-P1 zeolite from coal fly ash and fumed silica wastes, employing it as a potent modifier in graphite electrodes to enhance the electrochemical detection of cadmium (II) in fertilizer samples. Through meticulous assessment using cyclic voltammetry (CV) in a potential window of −1.2 V to 0.5 V, square wave voltammetry (SWV) in a potential region of −1 V to 0.5 V, and electrochemical impedance spectroscopy (EIS) in a frequency ranging from 100 kHz to 10 mHz under open circuit potential polarization, the electrochemical performance of the zeolite-modified graphite electrode (ZGE) was evaluated. The optimization process involved fine-tuning various parameters such as paste composition, solution pH, scan rate, and analyte concentration. Real sample analysis confirmed the applicability of the method in fertilizer samples. Notably, in an HCl medium (pH = 1.0), the SWV oxidation peak of Cd(II) was observed at −0.56 V (vs SCE) with a deposition time of 20 s and a scan rate of 75 mV∙s−1. The ZGE exhibited a remarkable detection limit of 1 μM, a quantification limit of 5 μM, and a high sensitivity of 6.581 μA/μM.cm2 within a linear detection range of 10−3–10−6 M. These findings highlight the potential utility of Na-P1 zeolite in handheld analytic device manufacturing, offering promising applications in environmental monitoring, resource management, and water and soil resource remediation.

Electrochemically Grown Hole-Rich NiO(OH) Thin Films toward Hole-Mediated Very Fast and Selective Enzyme-Free Electrochemical Sensing of Dopamine under Simulated Environment.

This work aimed to develop an enzyme-free semiconductor-assisted electrochemical technique for the selective detection of the neurotransmitter dopamine. In this case, electrochemically grown nickel oxyhydroxide [NiO(OH)] thin films were chosen to fabricate the sensing platform, i.e., the electrodes. Chronoamperometry was used to deposit the films on indium tin oxide (ITO) coated glass substrates. The films were thoroughly characterized to establish their structure, composition, phase purity, and electrochemical attributes. Electrochemical sensing characteristics were investigated by means of cyclic and differential pulse voltammetry, steady-state amperometry, and electrochemical impedance spectroscopy. The effects of several interfering agents like glucose, sodium chloride, methanol, hydrogen peroxide, and paracetamol were also studied on the detection attributes of dopamine. Significantly high value of sensitivity (11.87 μA μM-1 cm-2) was obtained for dopamine sensing that was associated with a limit of detection (LoD) of 0.22 μM of dopamine. However, the sensitivity (2.51 μA μM-1 cm-2) and LoD (1.20 μM) obtained for serotonin were inferior compared to those of dopamine. The performance of the electrode toward dopamine sensing was not compromised either in the presence of only serotonin or a series of other electroactive interfering agents, which makes the electrode very much dopamine selective. The dopamine response time was 200 ms, which is notably fast. Extensive studies on the effect of temperature, pH and scan rate on the detection of dopamine by the developed electrode material have also been carried out. The developed electrodes were also found to be notably stable for dopamine detection with a decay of only 6.6% in oxidation peak current density after the 50th cycle. Real-life application of the developed electrode material was checked with urine samples from adult male humans and yielded encouraging results.

Preparation of C@C3N4/IL/AuNPS as a sensitive electrochemical sensor for the determination of doxorubicin

Carbon-doped graphitic carbon nitride (C@C3N4) was synthesized through a carbon self-repairing process from which a nanocomposite of C@C3N4, ionic liquid, and gold nanoparticles (C@C3N4/IL/AuNPs) was prepared and used as a sensor for Doxorubicin (DOX) detection. The charge transfer resistance of the glassy carbon electrode (GCE) was decreased from 1.9 to 0.1 kΩ after modification with C@C3N4/IL/AuNPs nanocomposite, while the GCE surface area was enlarged nearly two times by the presence of C@C3N4/IL/AuNPs. The reversible redox peaks were observed for DOX at GCE/C@C3N4/IL/AuNPs with high peak currents nearly 45 times that of the nascent GCE. Scan rate and pH effects revealed a pH-dependent adsorption-controlled process for DOX oxidation. A linear relationship between the oxidation peak current and DOX concentration in the 10–5000 nM range led to a low detection limit of 3 nM. The sensor was selective to measure DOX in real samples within the recovery percentage of 98.16–104.

Unprecedented and laborless polymer film of azorubin S for electrocatalytic sensing of nicotine in human serum and saliva

AbstractAn accurate, disposable and cost‐effective determination, and monitoring of nicotine in human bodily fluids such as serum and saliva is significant due to the deleterious effects on humankind. In this paper, it was reported an electrocatalytic sensing platform for nicotine determination with poly azorubin s film modified pencil graphite electrode qualified by electroanalytical techniques such as cyclic voltammetry and electrochemical impedance spectroscopy, electron beam based technique of scanning electron microscopy, and X‐ray based techniques including photoelectron spectroscopy and energy dispersive spectroscopy. The developed platform exhibited a 410 % signal increase compared to the bare pencil graphite electrode (280 % increase in current density over aPGE) for nicotine detection due to the improved charge transfer and conductivity characteristics of the polymer film. The oxidation peak at 700 mV was employed for nicotine detection with a good detection sensitivity of , a remarkable detection limit of 89 nM, and wide linear ranges of 0.25–3 μM and 5–100 μM. Furthermore, the electrochemical sensor showcases superb stability, selectivity and accuracy for the determination of nicotine in real samples of human serum and saliva.

An affordable and green voltammetric approach for the determination of sotalol in biological, environmental, and pharmaceutical samples

AbstractThis work outlines the development of a voltammetric method for a sensitive, rapid, and environmentally friendly determination of the antihypertensive sotalol (SOT) in several sample types employing the anodically pretreated boron‐doped diamond electrode. Cyclic voltammograms of SOT presented a well‐defined irreversible oxidation peak at 1.21 V (Ag/AgCl (3.0 mol L−1 KCl)) in Britton–Robinson buffer solution (pH 3.0). Figures of merits recommended by the validation guidelines were evaluated for the validation of the present method. Employing differential pulse voltammetry linearity of SOT was obtained in the concentration range of 0.39–4.22 μmol L−1 in 0.1 mol L−1 H2SO4 solution, with a limit of detection of 0.031 μmol L−1. The selectivity of the method was assessed against interferers and show relative standard deviation (RSD) values lower than 6 %. Recovery tests yielded percentages ranging from 93 % to 96 % in urine sample and from 100 % to 107 % in tap water sample. The proposed method was successfully applied in pharmaceutical, environmental, and biological samples offering a suitable green analytical chemistry profile.

A sensitive and selective voltammetric method for the detection of pyrogallol in tomato and water samples using platinum electrode modified with alizarin red S film.

In contrast to the hyperactive platinum electrode, ARS modified platinum electrode presents a remarkable inertness toward adsorption and surface processes and lends it for further voltammetric applications. Measuring pyrogallol levels in samples is significant for assessing their antioxidant activity, which is crucial for understanding their potential health benefits and ability to combat oxidative stress. In addition, the excess consumption of pyrogallol can have significant negative effects on human health. A voltammetric sensor has been developed for the determination of pyrogallol using ARS modified platinum electrode. The electrode was prepared by electrodeposition of alizarin red S on a platinum electrode using cyclic voltammetry with a potential scan range of - 0.4 to 1.2V against an Ag/AgCl quasi reference electrode for 60 cycles as optimum number of cycles. The modified electrode was characterized by CV and SEM techniques. This modified alizarin red S platinum electrode showed remarkable electrocatalytic performance and stability, resulting in a significant increase in pyrogallol oxidation current by 11.05% compared to the pyrogallol oxidative current at the unmodified platinum electrode. A well-defined oxidation peak was observed at ~ 0.40V. The sensor exhibited a low limit of detection (LOD) of 0.28µM and a linear standard curve covering the ranges of 1.0-40µM and 0.01-10.0mM pyrogallol. Extensive studies were performed to evaluate possible interferences from various organic and inorganic compounds and yielded satisfactory results that confirm the selectivity of the developed sensor for pyrogallol determination. In addition, the ARS-Pt electrode provided consistently reliable results for the accurate detection of pyrogallol in water and tomato samples.

A novel copper ion enhanced electrochemical DNA biosensor for the determination of epinephrine

A novel electrochemical biosensor was developed for the detection of epinephrine (EP) by immobilizing double-strand DNA (dsDNA) bound with copper ions on a gold electrode (Cu2+/dsDNA/MCH/AuE). The electrochemical behavior of EP at Cu2+/dsDNA/MCH/AuE was examined, and the results demonstrated a significant enhancement in the electrocatalytic oxidation peak current of EP due to the formation of a stable G-Cu(II)-G sandwich structure between Cu2+ and guanine at the modified electrode. The modification process of the electrode was characterized by scanning electron microscopy, infrared spectroscopy, electrochemical impedance spectroscopy, and differential pulse voltammetry. A study on the effect of pH in phosphate buffer solution on the electrochemical oxidation of EP indicated that the catalytic oxidation process was pH-dependent. A plot of catalytic current versus EP concentration exhibited a dual-linear relationship within two ranges: 1.0–12.5 μM and 12.5–1000.0 μM, with correlation coefficients of 0.995 and 0.997, respectively. The limit of detection was determined to be 47 nM (S/N = 3). According to the calculated Hill coefficient (0.99), it can be concluded that the electrocatalytic process followed the Michaelis-Menten kinetic mechanism. The maximum catalytic current Im was 25 μA, while the apparent Michaelis-Menten constant Km was 1.425 mM. These findings indicated excellent electrocatalytic activity of the modified electrode towards oxidation of EP. The developed biosensor successfully detected EP in spiked mouse serum as well as epinephrine hydrochloride injection with high selectivity, sensitivity, stability, and accuracy.

A Novel Electrochemical Sensor Based on Pd Confined Mesoporous Carbon Hollow Nanospheres for the Sensitive Detection of Ascorbic Acid, Dopamine, and Uric Acid.

In this study, we designed a novel electrochemical sensor by modifying a glass carbon electrode (GCE) with Pd confined mesoporous carbon hollow nanospheres (Pd/MCHS) for the simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA). The structure and morphological characteristics of the Pd/MCHS nanocomposite and the Pd/MCHS/GCE sensor are comprehensively examined using SEM, TEM, XRD and EDX. The electrochemical properties of the prepared sensor are investigated through CV and DPV, which reveal three resolved oxidation peaks for AA, DA, and UA, thereby verifying the simultaneous detection of the three analytes. Benefiting from its tailorable properties, the Pd/MCHS nanocomposite provides a large surface area, rapid electron transfer ability, good catalytic activity, and high conductivity with good electrochemical behavior for the determination of AA, DA, and UA. Under optimized conditions, the Pd/MCHS/GCE sensor exhibited a linear response in the concentration ranges of 300-9000, 2-50, and 20-500 µM for AA, DA, and UA, respectively. The corresponding limit of detection (LOD) values were determined to be 51.03, 0.14, and 4.96 µM, respectively. Moreover, the Pd/MCHS/GCE sensor demonstrated outstanding selectivity, reproducibility, and stability. The recovery percentages of AA, DA, and UA in real samples, including a vitamin C tablet, DA injection, and human urine, range from 99.8-110.9%, 99.04-100.45%, and 98.80-100.49%, respectively. Overall, the proposed sensor can serve as a useful reference for the construction of a high-performance electrochemical sensing platform.

Harmonize the Al doped CdO nano particles by two distinguishable technique worn as anode in Al-air battery

The development of an effective and economical anode is crucial for Al-air batteries. This article, describes the Al doped CdO nanomaterials that was created using the hydrothermal and sol-gel techniques, for optimization. The measurement of crystal size was done using X-ray diffraction. A scanning electron microscopy was used to examine the morphology of surfaces. The structure of the molecule and the strength of the link between Al doped CdO was revealed by the Fourier Transform infrared technique. Studies on electrochemical properties are determined by the voltammetry and GCD with a NaOH electrolyte. The electrochemical findings demonstrates that the sol-gel method used to prepared Al doped CdO had both oxidation and reduction peaks which indicates that this is one of the suitable electrode production method for an electrode in Al-air battery. The specific capacitance of the material synthesized was found to be the highest (289 F/g at 2 mA/g).

Effects of Postdeposition Annealing on the Electrical Properties of Cu2O/4H–SiC PiN Diodes

Copper oxide (Cu2O) is a promising p‐type material owing to its high absorption coefficient, suitable bandgap width, chemical stability, nontoxicity, and abundance. In this study, the effect of postdeposition annealing (PDA) on the electrical properties of Cu2O thin films deposited on silicon carbide (SiC) substrates is investigated. The films are subjected to PDA using radio‐frequency sputtering at various temperatures in air. During PDA, the Cu2O films are maintained at <300 °C and transitioned to cupric oxide (CuO) at 400 °C. The as‐deposited Cu2O film exhibits a low oxidation peak (Cu2+), whereas the phase‐transformed CuO films exhibit a higher binding energy with the emergence of satellite peaks. The rectification ratios of the Cu2O device annealed at 300 °C and CuO device annealed at 400 °C are determined as 2.02 × 107 and 1.01 × 105, respectively, denoting the substantial enhancement of approximately 55.04 for the Cu2O/SiC device and degradation of approximately 0.28 for the CuO/SiC device relative to their non‐annealed counterparts. Therefore, in this study, the significant improvement in the performance of Cu2O thin films with the meticulous deposition control of potential p‐type materials, such as Cu2O and CuO, for high‐throughput and low‐cost electronic applications is demonstrated.

Gold nanoparticles decorated kaolinite mineral modified screen-printed electrode: Use for simple, sensitive determination of gallic acid in food samples

The current study offers the nanomolar quantification of gallic acid (GAL) based on gold nanoparticles (AuNps) and kaolinite minerals (KNT) modified on a screen-printed electrode (SPE). The electrochemical behavior of GAL was performed using differential pulse voltammetry (DPV) in Britton Robinson (BR) buffer solution at pH 2.0 as a supporting electrolyte. Under the optimized DPV mode parameters, the oxidation peak current of GAL (at 0.72 V vs Ag/AgCl) increased linearly in the range between 0.002 μmolL−1 and 40.0 μmolL−1 with a detection limit of 0.50 nmolL−1. The effect of common interfering agents was also investigated. Finally, the applicability of the proposed method was verified by quantification analysis of GAL in black tea and pomegranate juice samples.

Electrochemical detection of antimalarial drug (Amodiaquine) using Dy-MOF@MWCNTs composites to prevent erythrocytic stages of plasmodium species in human bodies

Herein, we report on fabrication of dysprosium-based metal–organic framework (Dy-MOF)@multiwalled carbon nanotubes (MWCNT) composites modified with glassy carbon electrode (Dy-MOF@MWCNT/GC) as a working electrode for Antimalarial drug detection. Dy-MOF@MWCNT composites was prepared by sonochemical process along with ultrasonication. The composite structure, phase purity, morphology and composition of the composites were confirmed by X-ray diffraction, Scanning electron microscope, and X-ray photoelectron spectroscopy. Further, Dy@MWCNT composites were deposited on a glassy carbon electrode by drop casting method, and used as an electrode material to efficiently detect Amodiaquine (ADD) by electrochemical techniques such as CV and DPV. The as-prepared Dy@MWCNT composite material showed the oxidation peak current of ADD to be ∼ 60 % higher than other unmodified GC electrodes and showed a low charge transfer resistance (Rct) of 24 Ω. The Dy@MWCNT provided a broad linear range of 0.4 to 20 µM with a limit of detection of 0.377 μM and sensitivity of 1.817 μA.μM−1 for the detection of ADD. According to the pH study, the amount of electrons and protons involved in the electrochemical processes of ADD was calculated and a plausible mechanism for ADD electro-oxidation was proposed. Thus, the prepared sensor exhibited practical usefulness by determining the ADD drug in human urine samples. Hence, the results shows that the Dy@MWCNT- modified sensor has good electrocatalytic activity for the redox of ADD.

Development of an electroanalytical methodology for the identification and quantification of cocaine in samples seized using a carbon paste electrode modified with multi-walled carbon nanotubes

Among the drugs of abuse, cocaine (COC) is the second most commonly used worldwide due to its stimulating and psychoactive effects. Currently, this drug is classified, according to the World Drug Report (WDR), as an illicit substance and is frequently seized by law enforcement agencies. Additionally, it can cause social problems due to its abusive use. This study describes the development of an electroanalytical methodology using square wave voltammetry (SWV) associated with a single electrode of carbon paste modified with 10 % MWCNTs (multi-walled carbon nanotubes) to quantify COC in seized samples containing up to 20% cocaine (low purity index) in the state of Espírito Santo (Brazil). SWV parameters, including Es = 10 mV, a = 30 mV, and f = 15 Hz, were optimized utilizing a Britton-Robinson buffer solution of 0.1 mol/L (pH 10) as a supporting electrolyte through the implementation of experimental design (CCD). COC showed an oxidation peak at approximately 1.0 V, with low limits of quantification and detection (1.90 × 10−6 mol L−1 and 5.75 × 10−7 mol L−1, respectively), in the linear range from 2.36 × 10−6 mol L−1 to 1.38 × 10−5 mol L−1, with the proposed methodology. Thus, this research develops a fast and low-cost technique in favor of the police, allowing the R2 = 99%. The results obtained in the intraday calibration curves present a relatively low standard deviation (RSD < 8%), indicating a good repetition of the value production of an electrode for less than USD 1.42 per analysis.

Novel disposable screen-printed sensors based on copper oxide nanoparticles for sensitive voltammetric assay of antazoline

The fabrication and electroanalytical validation of a novel homemade screen-printed carbon electrode enriched with copper oxide nanoparticles (CuONPs/SPCEs) were demonstrated for sensitive and selective voltammetric determination antazoline (ANT) in eye drop solution and spiked serum samples. With a reported electrocatalytic activity, CuONPs catalyzed the oxidation of ANT at the electrode surface showing an irreversible anodic oxidation peak at 0.9 V under a diffusion-controlled electrode reaction. Based on the electroanalytical and molecular orbital calculation studies, oxidation of ANT molecule undergoes via oxidation of the aliphatic nitrogen atom within the ANT moiety. Linear calibration curves were illustrated covering the ANT concentration ranged from 0.01 to 3.819 µg mL−1 with and limit of detection 3 ng mL−1. The fabricated sensors enriched with CuONPs exhibited high fabrication and measurement reproducibility with a prolonged shelf lifetime (6 months). The electroanalytical approach presented adequate sensitivity and selectivity with a short analysis time, applying low-cost instrumentation and simple pretreatment protocol avoiding handling hazardous organic solvents. Trace ANT was monitored in the presence of different interfering species, degradation products, and xylometazoline hydrochloride (ZYL) in the co-formulated ophthalmic pharmaceutical samples. The CuONPs based voltammetric sensors were introduced as a reliable eco-friendly analytical tool for monitoring ANT in ophthalmic solutions and biological fluids with acceptable recovery values.

Simultaneous Dopamine and Serotonin Monitoring in Freely Moving Crayfish Using a Wireless Electrochemical Sensing System.

Dopamine (DA) and serotonin (5-HT) are neurotransmitters that regulate a wide range of physiological and behavioral processes. Monitoring of both neurotransmitters with real-time analysis offers important insight into the mechanisms that shape animal behavior. However, bioelectronic tools to simultaneously monitor DA and 5-HT interactive dynamics in freely moving animals are underdeveloped. This is mainly due to the limited sensor sensitivity with miniaturized electronics. Here, we present a semi-implantable electrochemical device achieved by integrating a multi-surface-modified carbon fiber microelectrode with a miniaturized potentiostat module to detect DA and 5-HT in vivo with high sensitivity and selectivity. Specifically, carbon fiber microelectrodes were modified through electrochemical treatment and surface coatings to improve sensitivity, selectivity, and antifouling properties. A customized, lightweight potentiostat module was developed for untethered electrochemical measurements. Integrated with the microelectrode, the microsystem is compact (2.8 × 2.3 × 2.1 cm) to minimize its impacts on animal behavior and achieved simultaneous detection of DA and 5-HT with sensitivities of 48.4 and 133.0 nA/μM, respectively, within submicromolar ranges. The system was attached to the crayfish dorsal carapace, allowing electrode implantation into the heart of a crayfish to monitor DA and 5-HT dynamics, followed by drug injections. The semi-implantable biosensor system displayed a significant increase in oxidation peak currents after DA and 5-HT injections. The device successfully demonstrated the application for in vivo simultaneous monitoring of DA and 5-HT in the hemolymph (i.e., blood) of freely behaving crayfish underwater, yielding a valuable experimental tool to expand our understanding of the comodulation of DA and 5-HT.

Electrochemical sensor based on nickel selenide/hydroxylated multiwalled carbon nanotubes nanocomposites for sensitive detection of maltol

An effective electrochemical sensor based on electrodeposition of nickel selenide nanoparticles (Ni3Se4) on the surface of a glass carbon electrode (GCE) modified with hydroxylated multiwalled carbon nanotubes (MWCNTs-OH) has been successfully developed for determination of maltol. The chemical composition and morphology of Ni3Se4/MWCNTs-OH composites are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) are employed to investigate the electrochemical behavior of maltol at Ni3Se4/MWCNTs-OH/GCE. Consequently, electrochemical sensor based on Ni3Se4/MWCNTs-OH/GCE for detection of maltol displays good electrocatalyst performance. The obtained oxidation peak current of maltol at Ni3Se4/MWCNTs-OH/GCE increases linearly with the increase in concentration of maltol in the range of 0.1 μM–2000 μM, and the calculated detection limit (LOD) is 17.5 nM (S/N = 3). In addition, the fabricated electrochemical sensor shows satisfactory stability, reliable reproducibility and excellent selectivity, and is successfully used to detect maltol in real samples with acceptable accuracy.