Reduction Peak Current Research Articles

Fabrication of nickel oxide/copper cobaltite/graphene quantum dot conductive ink as an electrode material for selective electrochemical detection of epinephrine

Wearable sensors and flexible electrodes are key components of point-of-care systems, facilitating enhanced accessibility and personalization in health monitoring. These technologies permit individuals to oversee their health status and enable healthcare professionals to remotely and in real time monitor patients’ health status more effectively. In this study, paper-based flexible screen-printed electrodes were constructed for the electrochemical determination of epinephrine (EP), which is crucial in the diagnosis of various diseases, with high selectivity and low detection limits. In a novel approach, nickel oxide (NiO), graphene quantum dots (GQD), and copper cobaltite (CuCo2O4) were employed in conjunctions for the first time in the development of conductive ink. The large surface area and high electrical conductivity of GQD, when combined with the electrocatalytic properties of NiO and CuCo2O4, resulted in the creation of a more efficient electroactive environment for electrochemical EP determination. The differential pulse voltammetry technique enabled the attainment of a limit of detection (LOD) of 11.66 nM within the 500–10 µM and 2–0.02 µM linear ranges. The reduction peak current of EP was examined throughout the analysis to eliminate the effects of possible interference species that may be present in real samples. Furthermore, the stable structures of GQDs and copper cobaltite enhanced the long-term performance of the sensors, and the combination of these materials increased the reproducibility and reliability of the sensors. Subsequently, the efficacy of the sensor was evaluated using real samples, specifically artificial sweat, and urine. The developed NiO/CuCo2O4/GQD/G/SPE sensor demonstrated satisfactory recovery values, with 94.5–110.5 %.

Efficient Peak Current Limit Strategy and Active Power Oscillation Reduction in a Three-Phase Grid-Interfaced PV-Battery System (GIPVBS) with Low Voltage Ride-Through Control

Efficient Peak Current Limit Strategy and Active Power Oscillation Reduction in a Three-Phase Grid-Interfaced PV-Battery System (GIPVBS) with Low Voltage Ride-Through Control

Tailoring glassy carbon electrode surface with FeBiO3 for electrochemical detection of dinitrophenol isomers

ABSTRACT This study presents a simultaneous, rapid, and highly sensitive electrochemical detection of 2,4- and 2,5-dinitrophenol isomers using an iron bismuth oxide (FeBiO3)-modified glassy carbon electrode (GCE). The FeBiO3-modified GCE exhibited superior electrochemical performance over bare GCE, Bi2O3-modified GCE, and Fe2O3-modified GCE, as demonstrated by electrochemical impedance spectroscopy (EIS) with the potassium ferricyanide (Fe(CN6)3-/4-) standard. The synthesised electrocatalyst FeBiO3 exhibited strong absorption both in the visible and UV regions of the spectrum, attributed to band gap transitions and charge transfer transitions linked to its Bi2O3 and Fe2O3 components. The morphology and the structure of the FeBiO3 were characterised using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD), while Fourier transform infrared spectroscopy (FTIR) was employed to analyse the functional groups attached to the surface of FeBiO3. Cyclic voltammetry (CV) clearly demonstrated an increased current and improved peak resolution for the reduction of 2,4- and 2,5-dinitrophenols at the FeBiO3/GCE, compared to the bare GCE. The mechanism shows that the reduction of 2,4- and 2,5-dinitrophenols occurs through interactions with the surface oxygen functional groups of FeBiO3, resulting in the stepwise reduction of their NO2 groups to hydroxyamino compounds and then to nitrosophenols. Using square wave voltammetry (SWV), the reduction peak currents were significantly improved, enhancing detection sensitivity beyond that reported in previous works. A linear range from 1 µM to 1 mm for the dinitrophenol isomers was established, with detection limits of 0.07 µM for 2,4-dinitrophenol and 0.09 µM for 2,5-dinitrophenol. The FeBiO3/GCE electrode showed interferences with mono-nitrophenols and mono-/di-chlorophenols in solution but maintained excellent long-term stability and reproducibility, allowing it to effectively detect dinitrophenol isomers in drinking water, tap water, and wastewater samples.

NiCoFeS/rGO nanozyme-mediated multifunctional homogeneous sensing system for ultrasensitive electrochemical assay of pesticides residues in fruits and vegetables

In this work, a homogeneous sensing platform was constructed for ultrasensitive electrochemical organophosphate pesticides (OPs) detection based on nano-enzyme NiCoFeS/rGO with high peroxidase-like activity. In the presence of H2O2, NiCoFeS/rGO catalyst oxidized o-phenylenediamine (OPD) to produce yellow OPDox with strong absorbance and reduction peak current. This activity could be inhibited by thiocholine (TCh) produced by acetylcholinesterase (AChE). However, presence of organophosphates (OPs) could inhibit AChE and reduce TCh production, enabling protect the peroxidase-like activity of NiCoFeS/rGO. So, according to the increased signal of OPDox, the content of OPs could be measured by colorimetric or electrochemical mode. Using electrochemical analysis mode and optimizing experimental conditions, the detection limit was low (9.74fg mL−1) and the linear range was wide (12.5fg mL−1-1.25 ng mL−1). The selectivity, stability reproducibility and practicability of the method were investigated. At the same time, the analysis results of colorimetric and electrochemical method for AChE and colorimetric method for OPs were preliminarily determined, respectively.

Investigation on the reaction progress of titanium and lead chloride in NaCl-KCl melt

The in-situ preparation of NaCl-KCl-TiClx molten salt electrolyte was investigated by replacement of PbCl2 and Ti in a NaCl-KCl melt at 750 ℃. The reaction progress of PbCl2(3.38 wt.%) with excess Ti was monitored in real-time by a series of electrochemical techniques such as cyclic voltammetry, square wave voltammetry, and open circuit chronopotentiometry. The thermodynamic calculation and electrochemical test results show that titanium ions are mainly generated in the form of Ti(III). The redox peak current of Pb(II) decreases rapidly and drops to below the detection limit of the electrochemical tests after 275 min. Simultaneously, the reduction peak current of Ti(III) increases rapidly from 0 to 75min, and reaches to the maximum value until 275 min. At this time, the replacement reaction has been completed, and the NaCl-KCl-TiClx(2≤x≤4) molten salt is obtained finally. Ti-Pb alloy was obtained by depositing at -1.0 V(vs. Ag/AgCl) for 30 min during the replacement process. Lead by-product of the replacement reaction was precipitated and collected. Electrolytic refining was carried out successfully using the NaCl-KCl-TiClx molten salt electrolyte prepared as described above. The results demonstrated that a stable NaCl-KCl-TiClx molten salt electrolyte can be obtained by the present method. The study provides a new thinking for the preparation of molten salt electrolyte containing titanium ions, and also provides theoretical references for the electrolytic refining of titanium and the preparation of titanium alloys by electrodeposition.

Adaptive Generalized Predictive Voltage Control of a Boost Converter for Peak Current Reduction in the Presence of Uncertainties

Adaptive Generalized Predictive Voltage Control of a Boost Converter for Peak Current Reduction in the Presence of Uncertainties

Molecular-Imprinting Assisted Polydopamine-Aptasensor On Carbon and Gold Nanomaterials Construct for The Haemophilia B Biomarker Detection

The study presents a comprehensive approach for enhancing the performance of a spiral micro-interdigitated electrode (spiral-μIDE) sensor for the detection of FIX protein. Electropolymerization using dopamine resulted in a molecular-imprinted polymer (polyDOP-μIDE-MIP) layer, which encapsulated the aptamer-FIX complex and was later leached to create cavities. Cyclic and linear-sweep voltammetry techniques were utilized for the MIP development and rebinding assessment. Linear sweep voltammetry demonstrated a linear relationship between FIX concentration and peak current reduction, with a limit of detection (LOD) of 0.250 picomolar. The sensor's sensitivity was determined as 2.613E-10 A.fM-1.μm-2. This work highlights the importance of nanomaterials integration, and electropolymerization in improving sensor performance. The integration of carbon and gold nanomaterials and the use of molecular imprinting contribute to the sensor's enhanced sensitivity and selective detection of FIX protein.

Bismuth-rich BiOBr/Bi24O31Br10/Ti3C2 polyheterojunction for visible photocatalytic degradation of dyes and Cr(VI) reduction and hydrogen production applications

The construction of bismuth-rich heterostructures is an important strategy to improve the performance of bismuth-based visible photocatalytic materials. In this study, the binary heterojunction BiOBr/Bi24O31Br10 (BOB) with efficient visible photocatalytic activity was constructed by in situ induced growth of BixOyBrz on the surface of BiOBr, and the multivariate heterojunction composite BiOBr/Bi24O31Br10/Ti3C2 (BOBT) was synthesized by using Ti3C2 as an electron acceptor. It was shown that the solvothermal pH, Bi/Br and calcination temperature had a strong influence on the composition and crystalline structure of BOBT. The optimized synthesis conditions were pH=8, Bi/Br=1/1 (molar ratio), and calcination temperature of 400℃. The introduction of Mxene significantly enhanced the visible-light responsiveness and photoelectric efficiency of BOBT. The visible light-catalyzed degradation of complex conjugated systems containing aromatic and azo structures by BOBT was synchronously accompanied by benzene ring opening, demonstrating an efficient visible light degradation capability. BOBT has a reduced reduction current peak compared to BOB, can rapidly reduce Cr (VI), and improves the photocatalytic hydrogen production efficiency by nearly three times compared to BiOBr without the addition of Pt additives. This study provides fundamental data for the construction of efficient bismuth-based visible photocatalytic materials and their applications.

Graphene nanoplatelets-polyaniline composite for the detection of cortisol

In this study, a highly selective Graphene oxide (GO)-Polyaniline (PANI) modified glassy carbon electrode (GCE) was fabricated and its electrocatalytic behaviour towards the electro-reduction of cortisol in human saliva was investigated. The synthesized nanocomposites were characterized using different analytical approaches. The electrochemical study of the PANI-GO modified electrode was analyzed by employing a cyclic Voltammetry (CV) study. The outcomes demonstrated a substantial enhancement in the reduction and oxidation current peaks of the modified GCE as associated to bare GCE, GO/GCE and PANI/GCE. Along with enhanced electronic properties, the biosensor displays the good selectivity and sensitivity, good reproducibility (95 %, n = 8), high stability (maintaining more than 95 % response even after 11 weeks of storage at −20C, 50 cycles), a wide linear range (100μ-10 mM) and small detection limit (30 μM). The utilization of PANI-GO in the electrode modification process may be attributed to these positive outcomes, given some of the amazing characteristics of the composite, such as its larger surface area, outstanding electrical conductivity, and good electrocatalytic behavior. Furthermore, the PANI-GO modified GCE was successfully validated by detecting cortisol in real human saliva samples using cyclic voltammetry, highlighting the effectiveness of the PANI-GO composite for non-invasive electrochemical cortisol detection.

Mesoporous silica nanoparticles decorated with C3N4 framework as a novel electrocatalyst for the design of a selective clonazepam sensor

In this study, a new chemical modifier based on copper nitrate hydroxide-containing mesoporous silica decorated with a C3N4 framework (MSN/C3N4/CNH) was developed to design a modified sensor for the determination of clonazepam (CZP). The resulting composite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDS), simultaneous thermal analysis (STA), Brunauer-Emmett-Teller (BET) and Barrett Joyner–Halenda (BJH) analyses. The fabricated electrochemical sensor which was designed with a new modified glassy carbon electrode (GCE) for CZP analysis, exhibits outstanding electrocatalytic activities toward the reduction of CZP. The results showed that significant sensitivity compared to existing methods improved with an excellent detection limit of 2.50 nmol L−1 for the CZP detection, and the modified electrode has high activity toward the oxidation and reduction of CZP, with an oxidation peak around 0.32 V, and a lower reduction peak around −0.78 V; at pH = 7.0. The effect of experimental and instrumental factors on the electrochemical sensor response was examined, and the cyclic voltammetric results confirmed the 4H+/4e− process in the electrochemical studies. Moreover, in differential pulse voltammetry, the reduction peak current was proportional toward the CZP concentration from 0.82 to 76.90 μmol L−1, at optimum conditions. The modified electrode showed good reproducibility, and repeatability with relative standard deviation values of 2.7% and 1.2%, respectively. The proposed method can be applied as a simple, selective, and precise method to determine CZP drug in real samples, with satisfactory results.

Multifaceted Functionalities of Bridge-Type DC Reactor Fault Current Limiters: An Experimentally Validated Investigation

With the ongoing expansion and interconnection of electrical power systems, alongside the rapid proliferation of renewable distributed generations (DGs), the short-circuit extent in the power grid is experiencing a significant rise. Fault current limiters (FCLs) have been introduced in an effort to address this issue, ensuring the robustness and sustainability of expensive power system components when confronted with short-circuit faults. Among the various types of FCLs, bridge-type DC reactor fault current limiters (BDCR-FCLs) have emerged as one of the most promising options. While BDCR-FCLs have shown excellent properties in limiting harmful short-circuit currents, they are also advantageous in other respects. This paper investigates the supplementary functionalities of BDCR-FCLs as a multifaceted device towards the enhancement of the quality of supplied energy in terms of total harmonic distortion (THD) reduction, power factor (PF) correction, peak current reduction for nonlinear loads, and soft load variation effects, as well as their capability to limit fault current. To this aim, the capabilities of BDCR-FCLs have been studied through various simulated case studies in PSCAD/EMTDC software V5.0.1, in addition to experimental tests considering an AC microgrid connected to a DC system. The experimental and simulation investigations verify the superior multifaceted functionalities BDCR-FCLs introduce in addition to their excellent fault current-limiting capabilities. The results show that PF improved by 6.7% and 7%, respectively, in simulation and experimental tests. Furthermore, the current THD decreased by 20% and 18% in the simulation and experiment, respectively.

Poly(L-lysine) modified glassy carbon electrode for sensitive electrochemical measurement of 2,3,5,6-tetramethylpyrazine

2,3,5,6-Tetramethylpyrazine (TMP), an organic compound with numerous potential health benefits, is extensively used in medical and food products. This research introduces a novel approach for the precise quantification of TMP by employing a poly(L-lysine) modified glassy carbon electrode (pLL/GCE). The pLL/GCE is fabricated through the electrochemical polymerization of L-lysine onto a glassy carbon electrode (GCE) surface. This modification enhances the electrode's electrocatalytic efficiency, resulting in a significant increase in the reduction peak current of TMP. Exploiting this distinctive property, we establish an electrochemical method for quantifying TMP using cyclic voltammetry (CV). Optimized conditions reveal a robust linear correlation between the reduction peak current of TMP and its concentration within two adjacent linearity ranges: 40.0 nmol/L to 1.0 μmol/L and 1.0 μmol/L to 100.0 μmol/L. Notably, this method achieves an impressive detection limit of 20.0 nmol/L. To validate the practicality of this approach, we analyzed various real-world samples, obtaining recovery rates ranging from 98.2% to 100.8%. The developed method holds significant promise for the determination of TMP in medical and food products, underscoring its potential for widespread application.

Polymerase incorporation of 4-nitrophenyl modified 2′-deoxyuridine-5′-triphosphates into double-stranded DNA for direct electrochemical detection

Three novel 2′-deoxyuridine-5′-triphosphates modified with 4-nitrophenyl groups via various linkers (dUTP-N1, dUTP-N2, and dUTP-N3) were tested as bearers of reducible electroactive labels as well as substrates suitable for enzymes used in polymerase chain reaction (PCR) and recombinase polymerase amplification (RPA) with a potential application to direct electrochemical detection of double-stranded deoxyribonucleic acid (dsDNA). In cyclic and square wave voltammograms on carbon screen printed electrodes, the labeled dUTP have demonstrated distinct reduction peaks at potentials of –0.7 V to –0.9 V (phosphate buffer, pH 7.4). The reduction peak currents of dUTP-N derivatives were found to increase with their molar concentrations. The dUTP-N3 with a double bond in the linker had the lowest reduction potential (about 100 mV less negative) among the derivatives studied. Further, dUTP-N nucleotides were tested as substrates in PCR and RPA to incorporate the electroactive labels into 90, 210, or 206 base pair long dsDNA amplicons. However, only a dUTP-N1 derivative with a shorter linker without the double bond demonstrated satisfactory compatibility with both PCR and RPA, though with a low reaction output of modified dsDNA amplicons (at 100% substitution of dTTP). The dsDNA amplicons produced by PCR with 85% substitution of dTTP by the dUTP-N1 in the reaction mixture were successfully detected by square wave voltammetry at micromolar concentrations at high square wave frequency.

Oxidized carboxymethyl cellulose/polyaniline-based hybrid nanocomposite for sensitive detection of environmentally hazardous nitrophenol in real samples

Present work aims at fabricating chemically active, reproducible, and reliable electrode material by Ag nanoparticles anchored oxidized-carboxymethyl cellulose (O-CMC) embedded Pani (Ag@Pani/O-CMC) based nanocomposite for the trace detection of 4-nitrophenol. The Ag@Pani/O-CMC was physiochemically characterized in detail using FTIR, SEM, TEM, UV–vis, XPS, and XRD to analyze functional groups, structural morphology, optical properties, and chemical compositions. Differential pulse voltammetry and cyclic voltammetry were adopted to explore the electrochemical performance of Ag@Pani/O-CMC modified glassy carbon electrode (Ag@Pani/O-CMC/GCE). The observed reduction peak current was proportional to the 4-NP concentrations with a high sensitivity (2.48 µA nM−1 cm−2) and displayed a detection limit of 0.58 nM and a good linear range of 10–100 nM. In addition, the sensor exhibited comparable sensing capability in real biological samples, including milk, mixed fruit juice, and tap water, with excellent recovery from 97.20 % to 101 %. It also depicted high repeatability as the current response remained at 84.52 % after 28 days of operation for 4-NP detection. This approach can be projected to result in the electrochemical sensor for safe industrial processing and environmental monitoring, which is expected to have good stability, excellent selectivity, and sensitivity for detecting traces of 4-NP in actual samples.

Simulation and fabrication of titanium dioxide thin films for supercapacitor electrode applications

Nanostructured thin-film electrode materials are proposed for supercapacitors due to their outstanding performance over bulk materials. In this work, we fabricated a TiO2 nanotube film over a titanium foil using a top-down approach for supercapacitor electrodes. We noticed that the fabricated nanotubes are uniform and well aligned, confirmed by FESEM; the TiO2 nanotube parameters were further simulated using COMSOL Multiphysics. Simulations show an areal capacitance of 1.19393 pF/cm2 with oxidation and reduction peak currents of 6.18921×10[Formula: see text] A and −6.0320×10[Formula: see text] A, respectively, at 10 mV/s scan rate. The as-prepared nanotubes show a poor areal capacitance of 1.0193 F/cm2, which is improved to 12.8764 F/cm2 at a scan rate of 10 mV/s, that is approximately 12.63 times with oxidation and reduction peak currents of 0.129 mA/cm2 and −0.105 mA/cm2, respectively, by performing an electrochemical etching. Further, the surface roughness of both as-prepared and etched samples is studied to comment on their surface area changes. The effect of the etched sample is studied, compared and validated with simulation, which reveals that the etched TiO2 nanotubes thin-film sample shows considerable similarity with the simulation results.

Eco-friendly electrochemical sensor for determination of conscious sedating drug “midazolam’’ based on Au-NPs@Silica modified carbon paste electrode

Benzodiazepines (BZDs) are a group of drugs prescribed for their sedating effect. Their misuse and addictive properties stipulate different authorities for developing simple, fast and accurate analytical methods for instantaneous detection. Differential pulse voltammetric technique (DPV) was utilized for the selective assay of midazolam hydrochloride (MDZ) in the pure, parenteral dosage forms and plasma samples. A chemically modified carbon paste electrode (CPE) was implemented during the study. The method depended on the electroreduction of MDZ on the surface of the electrode over a potential range of 0.0 V to −1.6 V. The electrode was fabricated using silica nanoparticles (Si-NPs) which were incorporated into the composition of the CPE and used to enhance the electrode performance. Then, to enhance the sensitivity of the method, a chronoamperometric modification step was applied for depositing gold nanoparticles (Au-NPs) on the carbon paste electrode surface. Modification with Au-NPs showed a higher reduction current peak for MDZ with well-defined peaks. Various parameters such as pH of the media and measurements scan rate were investigated and optimized to enhance the sensor sensitivity. The sensor showed a dynamic linear response over a concentration range of 4.0 × 10−7 M to 2.9 × 10−4 M of MDZ with a LOD of 2.24 × 10−8 M using 0.1 M acetate buffer (pH 5.6). The sensor was validated in accordance with the ICH guidelines regarding accuracy, precision and specificity for the selective assay of MDZ in the presence of excipients. A greenness evaluation was performed using three different assessment tools, namely, the “Green Analytical Procedure Index” (GAPI), the “Analytical Greenness metric” (AGREE) and the “Whiteness Analytical Chemistry tool” (WAC) using the RGB12 model.

Bio-based hierarchical vertically aligned 2D ZnO nanostructures for ultra selective electrochemical sensing of p-Chloroaniline

Herein, we report synthesis of hierarchical 2D vertically aligned nanostructures (VANs) of ZnO onto the surface of FTO glass via bioinspired route for targeted electrocatalytic sensing of p-Chloroaniline (p-CA). The phytochemicals present in vegetal extract of Sechiun edule were employed to grow and form stable ZnO VANs onto FTO (ZnO-VANs(bio)/FTO). The morphological characterizations of ZnO-VANs(bio)/FTO showed the formation of vertical nanostructures (length ∼ 820 nm) with high density and good crystallinity. It exhibited an increased surface roughness 2.2-fold higher than seeded FTO (ZnO@seed/FTO). The ZnO-VANs(bio)/FTO@pH7 electrode showed a decrease in electron transfer resistance from 7.78 to 3.02 MΩ with 1.2-fold increase in effective surface area than FTO(bare). The oxidation of p-CA included an irreversible one-electron oxidation mechanism with formal potential (E0) of 0.978 V vs. Ag/AgCl and standard heterogeneous rate constant (k) of 0.737 s−1. ZnO-VANs(bio)/FTO@pH7 exhibited remarkable electrocatalytic sensing of p-CA with low limit of detection (0.021 µM) and excellent sensitivity (0.194 µA·µM−1·cm−2) between a linear window of 2–200 µM. The detection limit of fabricated sensor for p-CA sensing was about 2-fold lower than FTO(bare). Chlorobenzene, carbendazim, profenofos, nitrite, 4-nitrophenol, bisphenol a, and mercury could not interfere p-CA sensing, and only 4.7% reduction in peak current was observed upto 9th cycle. The ZnO-VANs(bio)/FTO@pH7 could efficiently sense p-CA in spiked river and residential water samples, comparable with HPLC (max 4.6% deviation). Therefore, ZnO VANs synthesized in a bio-based route is a potential electrocatalyst for binder-free sensor development with high stability and low detection limit for sensing pesticides and their intermediates.

Development of a high-performance label-free electrochemical immunosensor for early cancer diagnosis using anti-CEA/Ag-MOF/GO/GCE nanocomposite

In order to detect carcinoembryonic antigen (CEA) as a tumor marker in lung cancer for early cancer diagnosis, this study aimed to develop a label-free electrochemical immunosensor based on the immobilization of an Anti-CEA antibody on a metal-organic framework (MOF)-graphene oxide nanocomposite modified glassy carbon electrode (Anti-CEA/Ag-MOF/GO/GCE). Ag-MOF/GO nanocomposite was prepared on the GCE surface using the ultrasonic irradiation method, and Anti-CEA antibody was subsequently immobilized on the surface. Analysis of the crystal structure and morphology of the modified electrode using FE-SEM and XRD revealed that the correct combination of GO nanosheets and Ag-MOF nanoparticles produced a high surface area to trap the antibodies. Electrochemical tests utilizing the CV and DPV methods revealed that the immunosensor's sensitivity, stability, and selectivity were improved by Anti-CEA/Ag-MOF/GO/GCE. Results showed that, with a detection limit of 0.005 ng/mL, the change in the reduction peak current was inversely correlated with the logarithm concentration of CEA in the range of 10-3 to 5000 ng/mL. The suggested CEA immunosensor's applicability in a human serum sample was investigated, and findings of analytical studies via standard addition technique for both ELISA and DPV assays revealed that significant agreement existed between the outcomes of the two assays. Additionally, the recoveries ranged from 99.00% to 99.25%, and all relative standard deviations (RSDs) for the sample detections were below 5.01%, indicating satisfactory accuracy in results measured with the proposed CEA immunosensor, indicating that the prepared CEA immunosensor in this study can be used in clinical applications and human fluids.

Lipopolysaccaride-binding peptides modified Au electrode for the sensitive detection of lipopolysaccharide in water

Lipopolysaccaride(LPS) is the main structural component of the outer membrane of Gram-negative bacteria and causes serious harm to people's health. Thus, in-time detection of LPS in environment is required. Herein, a new LPS electrochemical detection method was developed by using ferricenecarboxylic acid (FCA)-labeled LPS-binding peptide as biomolecular recognition element and electrochemical signal. Au nanoparticles were assembled on 1,6-hexanedithiol modified Au electrode through sulfhydryl groups, and FCA labeled the C-terminal cysteine of LPS-binding peptide was assembled on Au nanoparticles to achieve its immobilization on the electrode surface. In presence of hexaammineruthenium(II/III), a mediated process between ferricene and hexaammineruthenium(II) resulted in electrical signal amplification. The addition of LPS and the its binding with peptides will induce more hexaammineruthenium(III) to access electrode, resulting in the reduction peak current of the hexaammineruthenium(III) and oxidation peak current of ferrocene both increased. The increased electrochemical signals are used to indicate the concentration of LPS. As a result, a highly-sensitive electrochemical method was developed for the rapid determination of LPS. The linear range was from 1.25 to 30 pg mL−1, and the detection limit was 0.039 pg mL−1. It was used in detection of LPS in environmental water samples, and the results consisted with that obtained by Limulus method.

Highly sensitive determination of putrescine in pork by an electrochemical biosensor constructed with unfolded hemoglobin and diamine oxidase

Based on the principle that diamine oxidase (DAO) catalyzes putrescine to produce H2O2 and unfolded hemoglobin (uHb) has the good catalytic ability to H2O2, a highly sensitive electrochemical biosensor for the determination of putrescine was constructed. The biosensor was prepared through immobilizing uHb on the surface of clay modified glassy carbon electrode (GCE) by physical adsorption method, and then using 2.5% glutaraldehyde as cross-linking agent to fix DAO. In order to achieve the best results, the concentration of DAO, the type of peroxidase, the stability of modified electrode and the test conditions were optimized. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to characterize the preparation process of the sensor. Under the optimized conditions, the difference of reductive peak currents had good linear relationships with putrescine concentration in the ranges of 1.0 × 10−11-1.0 × 10−10 mol L−1 and 1.0 × 10−10-1.0 × 10−9 mol L−1 (r ≥ 0.997), respectively. The limit of detection (LOD) was 3.3 × 10−12 mol L−1 (S/N = 3). The developed electrochemical biosensor had good reproducibility, stability and sensitivity, and was successfully applied for the determination of putrescine in real pork samples.