Chronocoulometry Research Articles

Preparation of Cu nanolayers by magnetic field-assisted electrodeposition and research on the nucleation and growth mechanism

Electrodeposition technology is widely used in the surface treatment of copper foil, and the core of this technology is roughening and curing treatment. During the electrodeposition process, the deposited layers often exhibits some problems, such as coarse grain size, uneven thickness and difficult control of crystal morphology. The magnetohydrodynamic (MHD) effect of magnetic field can obviously control the electrodeposition of Cu and improve the micro-morphology and performance of deposited layers. In this paper, Linear Sweep Voltammetry (LSV), Cyclic Voltammetry (CV) and Chronocoulometry (CC) curves were adopted to investigate the electrochemical behavior of deposited Cu in ultra-high acidity sulfate systems under different magnetic field conditions. The nucleation and growth mechanism were discussed, and the micro-morphology of deposited layers was analyzed. The results show that the electrodeposition of Cu follows the three-dimensional (3D) growth mechanism of progressive nucleation and diffusion control under the static condition, and the deposits appear cylindrical shape formed by spherical agglomerated. The magnetic field significantly improves the mass transfer rate, and the deposited layers will be more uniform and dense, following 3D growth mechanism under the electrochemical control. With the increasing of magnetic field intensity, the nucleation mechanism gradually shifts from progressive to transient nucleation. At the early stage of nucleation, the high-intensity magnetic field can significantly increase the number of grains and refine them, obtaining uniform and dense deposited nanolayers.

A dual-mode electrochemical biosensor based on GO-Fe3O4 doped PEDOT nanocomposite for the ultrasensitive assay of microRNA

MicroRNA, as a distinctive biomarker, plays a crucial role in the early prognosis and diagnosis of numerous severe diseases. However, due to its inherent properties such as low abundance, small size, and high sequence similarity, the sensitive and accurate detection of microRNA remains a major challenge. Herein, a dual-mode electrochemical biosensing platform was developed for microRNA detection, based on poly(3,4-ethylenedioxythiophene) (PEDOT) doped with graphene oxide-Fe3O4 (GO-Fe3O4) nanocomposite. The GO-Fe3O4/PEDOT composite demonstrated a porous microstructure, outstanding conductivity, and robust catalytic activity towards nitrite. It was electrodeposited onto the electrode surface in a one-step process using the cyclic voltammetry method (CV). The microRNA biosensor was obtained by anchoring DNA with amino groups to the GO-Fe3O4/PEDOT layer through the formation of amide bonds. The designed dual-mode microRNA biosensor demonstrated a broad linear range spanning from 10−15 M to 10−6 M, with low detection limits of 5.18 × 10−15 M and 7.36 × 10−15 M when using chronocoulometry (CC) and amperometric i-t curve (i-t) modes, respectively. Furthermore, a dual-mode electrochemical biosensor has been successfully developed and utilized for the detection of microRNA in human serum, demonstrating its potential for precise and sensitive microRNA detection and its practical application value in clinical medicine.

Electrochemical analysis of extracellular electron transfer process of Pseudomonas aeruginosa NEJ07R using pyocyanin on a carbon electrode

Indirect extracellular electron transfer (IEET), or mediated electron transfer (MET), is a process that has attracted attention for its application in electrochemical-microbial technologies for power generation, wastewater treatment, or electrofermentation. Pseudomonas aeruginosa is a bacterium known to carry out IEET because it produces its own redox mediator (RM), pyocyanin (PYO), which has electrochemical properties such as a high electron transfers rate and low resistance to charge transfer. However, other physical processes, such as PYO adsorption on the electrode, can alter that function. In this work, interaction parameters and adsorption-free energy values were determined to obtain an adsorption mechanism on a carbon-based electrode. Furthermore, the effect of PYO addition and its adsorption were studied in the IEET process of P. aeruginosa NEJ07R. The electrochemical profiling of PYO by cyclic voltammetry (CV) and chronocoulometry (CC) measurements allowed the calculation of the Laviron interaction parameter (ν'gθT). Since the values of ν'gθT > 0, it was determined that PYO maintains attractive interactions with the surface in cathodic and anodic reaction. Moreover, the low interaction free energies (ΔG0' ≈ −2.91 ×10−5 ± 1.28 ×10−8 kJ/cm3 and -−2.92 ×10−5 ± 2.74 ×10−8 kJ/cm3 for reduction and oxidation, respectively) suggests that the interactions are weak. As for the IEET of P. aeruginosa NEJ07R, the microbial catalysis process on a carbon cloth electrode was confirmed by adding PYO to the electrochemical cell. Electrochemical and FT-IR characterization confirmed the adsorption of PYO on the surface, so it is proposed that P. aeruginosa NEJ07R takes advantage of PYO adsorption to carry out IEET.

Multi-Walled Carbon Nanotube Array Modified Electrode with 3D Sensing Interface as Electrochemical DNA Biosensor for Multidrug-Resistant Gene Detection.

Drug resistance in cancer is associated with overexpression of the multidrug resistance (MDR1) gene, leading to the failure of cancer chemotherapy treatment. Therefore, the establishment of an effective method for the detection of the MDR1 gene is extremely crucial in cancer clinical therapy. Here, we report a novel DNA biosensor based on an aligned multi-walled carbon nanotube (MWCNT) array modified electrode with 3D nanostructure for the determination of the MDR1 gene. The microstructure of the modified electrode was observed by an atomic force microscope (AFM), which demonstrated that the electrode interface was arranged in orderly needle-shaped protrusion arrays. The electrochemical properties of the biosensor were characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). Chronocoulometry (CC) was used for the quantitative detection of the MDR1 gene. Taking advantage of the good conductivity and large electrode area of the MWCNT arrays, this electrochemical DNA sensor achieved a dynamic range from 1.0 × 10-12 M to 1.0 × 10-8 M with a minimal detection limit of 6.4 × 10-13 M. In addition, this proposed DNA biosensor exhibited high sensitivity, selectivity, and stability, which may be useful for the trace analysis of the MDR1 gene in complex samples.

Effect of ultrasonic field on the mechanism of electrodeposited Cu nucleation and growth

Electrodeposition technology is widely used in the surface treatment of copper foil. The unique “mechanical disturbance effect” and “cavitation effect” of ultrasonic field can effectively control the electrodeposition process of Cu and improve the quality of electrodeposited layer. In this paper, Linear Sweep Voltammetry (LSV), Cyclic Voltammetry (CV), Chronoamperometry (CA) and Chronocoulometry (CC) were used to study the electrochemical behavior of electrodeposited Cu in ultra-high acidity sulfate systems under different ultrasonic field powers. The nucleation and growth mechanism of Cu were discussed, and the surface morphology of electrodeposited layer was analyzed. The results show that the electrodeposition of Cu under the static condition (0 W) follows the diffusion controlled progressive nucleation and 3D growth mechanism, and the deposits are in the cylindrical shape with spherically agglomerated. The ultrasonic field significantly improves the mass transfer rate in the electrodeposition process, and the fine dispersion effect is obvious. The uniform and dense micro-nano layers are formed, following the 3D growth mechanism. With the increasing of ultrasonic field power, the nucleation mechanism gradually changes from the diffusion controlled progressive nucleation to the electrochemistry controlled instantaneous nucleation. In addition, there appear peeling, grooving and local microcracks on the electrodeposited layer under higher ultrasonic power condition, and it is easier to form a smooth and uniform electrodeposited layer with the ultrasonic power of 60 W compared to that with the ultrasonic power of 100 W.

Nickel electrodeposition from deep eutectic solvents containing copper ions at a high temperature

In the current study, the electrodeposition of nickel in the presence of various concentrations of copper ions was studied in a eutectic-based ionic liquid, i.e., 1:2 choline chloride (ChCl):ethylene glycol (EG), which is called Ethaline, at 90 °C. The electrodeposition process was conducted in the presence of additional additives such as nicotinic and boric acids. The electrolyte solution was characterized using a conductivity test and UV–vis analysis. The electrodeposition process is highlighted using cyclic voltammetry (CV) and chronocoulometry (CC). The deposited nickel was subjected to a hardness test and different X-ray techniques, such as SEM, XRD and EDX analysis. The effect of the copper ion concentration on the quality of the electrodeposit was highlighted. It was found that the electrodeposition of nickel from the eutectic-based ionic liquid in the presence of copper ions improved the surface quality, minimized roughness, and promoted consistent surface morphology. The significant difference in the deposit morphology is discussed in the context of metal speciation and mass transport differences between the aqueous and ionic liquids.

Hierarchical Biobased Macroporous/Mesoporous Carbon: Fabrication, Characterization and Electrochemical/Ion Exchange Properties

With the goal of improving the mechanical properties of porous hierarchical carbon, cellulosic fiber fabric was incorporated into the resorcinol/formaldehyde (RF) precursor resins. The composites were carbonized in an inert atmosphere, and the carbonization process was monitored by TGA/MS. The mechanical properties, evaluated by nanoindentation, show an increase in the elastic modulus due to the reinforcing effect of the carbonized fiber fabric. It was found that the adsorption of the RF resin precursor onto the fabric stabilizes its porosity (micro and mesopores) during drying while incorporating macropores. The textural properties are evaluated by N2 adsorption isotherm, which shows a surface area (BET) of 558 m2g-1. The electrochemical properties of the porous carbon are evaluated by cyclic voltammetry (CV), chronocoulometry (CC), and electrochemical impedance spectroscopy (EIS). Specific capacitances (in 1 M H2SO4) of up to 182 Fg-1 (CV) and 160 Fg-1 (EIS) are measured. The potential-driven ion exchange was evaluated using Probe Bean Deflection techniques. It is observed that ions (protons) are expulsed upon oxidation in acid media by the oxidation of hydroquinone moieties present on the carbon surface. In neutral media, when the potential is varied from values negative to positive of the potential of zero charge, cation release, followed by anion insertion, is found.

Effect of adsorption of pyocyanin on the electron transfer rate at the interface of a glassy carbon electrode

Redox mediators (RM) are an alternative to improve the performance of microbial electrochemical systems (MES) as they help significantly to develop the indirect electron transfer. However, their use is limited when the redox processes between the RM and the electrode surface are not thoroughly understood. The adsorption, the intermolecular interactions with the electrode, and the effects on charge transfer kinetics are important issues in MES such as microbial sensors, microbial electrosynthesis or microbial fuel cells, but are rarely analyzed. Pyocyanin, considered an RM, may present these features due to its chemical structure. Today, the electrochemical studies indicate that pyocyanin can presents adsorption processes on glassy carbon electrodes. However, the effects of adsorption on electron transfer rate and changes as a function of pyocyanin concentration have not yet been studied. Therefore, this work presents an electrochemical study of pyocyanin to determine the effect of concentration and adsorption on the electron transfer rate at a glassy carbon electrode. Analysis of the electrochemical profiles obtained by cyclic voltamperometry (CV) indicates that there is an effect of concentration (C*) on the heterogeneous electron transfer rate constant (k0) since the criterion ΔEp varies as a function of C*. In addition, the peak proportionality parameter Ipa/Ipc and the voltamperometric function Ip/v½ help deduct the adsorption to the electrode. Experimental data obtained by chronocoulometry (CC) and CV, indicate that k0 = 5.7 × 1011 m/s and Rct = 3.40 × 10−16 Ω under the C* = 0.14 mM condition, while k0 = 1.10 × 103 m/s and Rct = 1.60 × 10−7 Ω under the C* = 0.49 mM condition. The differences in k0 and Rct values at different values of C* are due to an accumulation of pyocyanin on the electrode surface in the inner Helmholtz plane (IHP), preventing the electron transfer of bulk-dissolved pyocyanin molecules present in the outer Helmholtz plane (OHP) region. The varying values of α, indicate that a part of the energy of the redox reaction could be employed for the adsorption processes. As for the interactions at the electrode, the values of the Laviron parameter (ν'gθT) indicate that attraction interactions between the pyocyanin molecules and the electrode dominate, since the values of ν'gθT are higher than 0. The results of this study will provide a comprehensive understanding of the redox cycle of pyocyanin. The information will be useful for the future development of electrochemical-microbial systems since that the interactions mediator-electrode may be an operational variable to facilitate their practical applications in environmental, sensing and electrosynthesis areas.

Rosa Damascena mediated ZnO-Red Ochre nanocomposite for the electrochemical determination of 5-Fluorouracil

In this study, ZnO-Red Ochre nanocomposite was green synthesized by Rosa Damascena (RD) extract (RDZRONCs). Proton Induced X-ray Emission microanalysis (Micro-PIXE) and X-ray diffraction (XRD) pattern confirmed the presence of hematite (Fe2O3), and quartz (SiO2) mineral phases in the Red Ochre (RO) nanoclay. In addition, the XRD pattern shows the ZnO, ZnFe2O4, SiO2, Fe2O3, and Si phases in the RDZRONCs that were green synthesized with natural RD extract and RO. The RDZRONCs were used to modify the carbon paste electrode (CPE) for the electrochemical determination of the anticancer drug 5-fluorouracil (5-FU). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques were employed to investigate the surface behavior of modified CPE (RDZRONCs/CPE). The electrochemical behavior of 5-FU at the RDZRONCs/CPE was exanimated by CV, differential pulse voltammetry (DPV), chronoamperometry (CA), and chronocoulometry (CC). Based on the DPV technique, a linear relationship between peak current and concentration of 5-FU was obtained in the dynamic range of 0.05–140.0 μM and with a detection limit equal to 0.0016 μM. The selectivity of RDZRONCs/CPE for 5-FU was studied in the presence of different inorganic and organic species. Also, the content of 5-FU was measured in real samples by RDZRONCs/CPE.

Electrocatalytic oxidation of NADH at graphene-modified electrodes based on electropolymerized poly(thionine-methylene blue) films from nature deep eutectic solvents

• Electropolymerization of PTH-MB films in ternary nature deep eutectic solvents. • PTH-MB NADES and ERG have a synergistic effect on the oxidation of NADH. • The prepared PTH-MB NADES -ERG electrode has excellent NADH electrocatalytic oxidation performance. • Sensitive detection of NADH in artificial urine samples. In this paper, a sensing platform for the electrocatalytic oxidation of nicotinamide adenine dinucleotide (NADH) was proposed. It was prepared by the electropolymerization of poly(thionine-methylene blue) (PTH-MB) in ternary nature deep eutectic solvent (NADES) on a glassy carbon electrode (GCE) that was modified with electrochemically reduced graphene oxide (ERG). The modified electrode was denoted as PTH-MB NADES -ERG/GCE. Cyclic voltammetry (CV), chronocoulometry (CC), electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), Raman spectroscopy, and Ultra Violet-Visible Spectroscopy (UV–Vis) were used to characterize the preparation processes. The electrochemical performances of the electrode in NADH oxidation were studied via CV and current-time methods. The NADH oxidation overpotential was lower on PTH-MB NADES -ERG/GCE compared to that on GCE, ERG/GCE, and PTH-MB NADES /GCE. The PTH-MB NADES -ERG/GCE showed excellent electrocatalytic activity for NADH oxidation with a linear range of 0.51–3333.33 µM (R 2 = 0.9534) and a detection limit of 0.159 nM. The sensor was further tested for NADH determination in artificial urine samples, showing promising biomedical applications.

Monoclinic WO3 nanosheets-carbon nanotubes nanocomposite based electrochemical sensor for sensitive detection of bisphenol A

• WO 3 -CNT nanocomposite was hydrothermally prepared and used as a novel sensing material. • WO 3 -CNT/GCE has enhanced electro-oxidation peak current and reduced potential for BPA. • Improved surface area, good electron transfer and reproducibility of the sensor. • WO 3 -CNT/GCE sensor for BPA has two linear ranges with low detection limit (16.3 nM) • Admirable performance of the sensor for the practical applicability in real samples. A novel and sensitive electrochemical sensor based on monoclinic tungsten trioxide (WO 3 ) nanosheets-carbon nanotubes nanocomposite (WO 3 -CNT) modified glass carbon electrode (GCE) is developed for the direct detection of endocrine disruptor bisphenol A (BPA) in textile sample for the first time. The electrochemical behavior of BPA on the resultant WO 3 -CNT/GCE sensor is investigated using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and chronocoulometry (CC). Under the optimized conditions, the proposed sensor can be adopted to the quantification of BPA using differential pulse voltammetry (DPV), and the electro-oxidation peak current is proportional to the BPA concentration in the range of 0.03–3.0 μM and 3.0–100 μM with a correlation coefficient of 0.9993 and 0.9992, respectively. Moreover, the proposed sensor with a detection limit of 16.3 nM (S/N = 3) exhibits good reproducibility, selectivity and stability, and can be successfully applied to detect the BPA concentrations in real samples (textile, plastic and tap water) with satisfactory recovery (99.4%-110.1%). The present strategy on the hybridization of CNTs and WO 3 enables more opportunities for the electrochemical detection of BPA in the practical applications.

Dual-Mode electrochemical biosensors based on Chondroitin sulfate functionalized polypyrrole nanowires for ultrafast and ultratrace detection of acetamiprid pesticide

The inappropriate and excessive use of pesticides poses a great challenge to human health. It is necessary to analyze pesticide residues efficiently, economically and quickly to minimize the risk of public safety issues. Herein, a dual-mode biosensor was proposed for ultrafast and ultratrace detection of acetamiprid (ACE). The polypyrrole nanowires (PPyNWs) was prepared using the guidance of CS by electrochemical method, which showed large electroactive surface area, excellent conductivity and high stability. After immobilization of ACE aptamer onto CS/PPyNWs, the biosensor can be effortlessly prepared. The ACE concentration can be measured by both the signal decrease of the chronocoulometry (CC) method and the chronoamperometry (CA) method. The dual-mode biosensor exhibited ultrafast detection speeds of 0.5 s and 2 s across 9 and 6 orders of magnitude linear ranges through CC and CA, respectively. More importantly, the biosensor was successfully applied to detect ACE residues in soil samples, proving the feasibility of the dual-mode biosensor for ACE detection in complex samples.

A sensitive electrochemical sensor manufactured from multi-wall carbon nanotubes-polyethylenimine nanocomposite for malachite green detection

Due to the high toxicity of malachite green (MG), it is of great significance to determine MG in aquaculture for the sake of food safety and human health. In this study, multi-walled carbon nanotubes (MWCNTs)-polyethylenimine (PEI) composites were modified on the surface of a glassy carbon electrode (GCE). Morphology of the modified electrode was observed by scanning electron microscopy (SEM). The ability of the sensor in detecting MG was investigated by chronocoulometry (CC), cyclic voltammetry (CV) and by differential pulse voltammetry (DPV). The experimental results indicated an excellent catalytic performance of the modified electrode in MG oxidation. The peak current of MG obtained on the MWCNTs-PEI/GCE has been enhanced greatly compared with that of MWCNTs/GCE. A large linear range from 0.01 μM to 6.0 μM and a relatively low limit of detection of 2.58 nM were observed under the optimum conditions. In addition, this sensor shows many advantages in MG detection with samples of water and fish, such as good accuracy and reproducibility, excellent anti-interference ability and rapid response, and the recoveries obtained were between 95.5% and 104.0%.

A Novel Electrochemical Sensor Based on Reduced Graphene Oxide–TiO2 Nanocomposites with High Selectivity for the Determination of Hydroxychloroquine

A simply sensitive sensor based on a reduced graphene oxide–TiO2 nanocomposite modified glassy carbon electrode (RGO–TiO2/GCE) was developed for the electrochemical determination of an antimalarial drug, hydroxychloroquine (HCQ). The modified electrode was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Electrochemical test showed that the RGO–TiO2 electrode had stronger electrochemical activity and higher effective real surface area than that of TiO2 electrode and bare electrode. The electrochemical response of RGO–TiO2 nanocomposite modified electrode toward HCQ oxidation was studied by CV, chronoamperometry (CHA), chronocoulometry (CHC) and square-wave voltammetry (SWV). Interestingly, RGO–TiO2/GCE indicated an excellent electrocatalytic activity for HCQ. Under the optimal experimental conditions, a linear relationship between the peak current and the concentration was obtained, ranging from 0.25 to 500 μM, with the detection limit (S/N = 3) of 12.5 nM and quantification limit (S/N = 10) of 0.97 μM. Furthermore, the proposed sensor was successfully applied to the determination of HCQ in pharmaceutical (tablets) samples. In summary, the developed sensor was low cost and efficient, making it potentially attractive for practical sample analysis application of HCQ.

Ultrasensitive electrochemical determination of trace ceftizoxime using a thin film of Preyssler nanocapsules on pencil graphite electrode surface modified with reduced graphene oxide

An ultrasensitive electrochemical sensor for the selective voltammetric measurement of trace ceftizoxime (CFX) was described. Modification of a pencil graphite electrode (PGE) was first done with the reduced graphene oxide (r-GO) and, afterward, Preyssler nanocapsules (PNCs) were generated onto the r-GO/PGE. The surface morphology of the synthetic compounds has been evaluated using FT-IR, FE-SEM, TEM, and SEM techniques. Adsorptive differential pulse voltammetry (AdDPV), cyclic voltammetry (CV), chronocoulometry (CC) and electrochemical impedance spectroscopy (EIS) were employed to investigate the CFX electrochemical characteristic on the modified electrode (PNCs/r-GO/PGE). The electron transfer coefficient (α) between PNCs/r-GO and PGE was calculated using the obtained CV. Also, chronocoulometry experiments were performed in the absence and presence of CFX to calculate diffusion coefficient (D) and capacity of adsorption (ΓS) of CFX for PNCs/r-GO/PGE thin film. Under the optimized conditions, the calibration curve of the CFX has a linear concentration range from 1.0 × 10−11 to 3.0 × 10−8 M (R2 = 0.9993) and a detection limit of 1.8 pM. The developed electrochemical sensor shows greater sensitivity than the earlier reported techniques for the CFX measurement. The sensor was successfully utilized to determine the trace amounts of CFX in pharmaceutical and blood serum with suitable recoveries.

Surface, optical and electrochemical performance of indium-doped ZnO/WO3 nano-composite thin films

Great demand on replacing emission and pollution-free materials for energy storage by traditional fossil fuels has led to investigating of high-performance electrochromic materials. Nano-composite for electrochromic device may be a good choice. In this paper, stack-structured indium-doped ZnO/WO3 nano-composite thin films were deposited on glass, indium-doped tin oxide (ITO) and fluorine-doped tin oxide (FTO)-coated glass substrates, respectively. Surface, optical and electrochromic (EC) performance of the prepared nano-composite films has been investigated. Electrochromic impedance spectroscopy (EIS), cyclic voltammetry, repeating chronoamperometry (CA) and chronocoulometry (CC) measurements were taken. The Raman spectroscopy measurement shows that high-intensity peaks are related to ZnO wurtzite structure for all substrates. In the CA measurement, the rate of Li+ transfer between surface and electrolyte was faster for films coated onto ITO substrate. In addition, the intercalation/deintercalation of Li+ was obviously found faster for films onto ITO substrate due to roughness, structure differences than the other sample. As an advantage of our nano-composite material, the absence of current decay in the both coloration and bleaching stages has proved superiority and stability of films as well as indium contribution. The reversibility of stack-structured InZnO/WO3 nano-composite films was computed as 30 and 50% for the film with ITO and FTO substrates. The highest coloration efficiency value has calculated as 80 and 69 cm2/C for nano-composite thin films deposited onto FTO substrate @ 632 and 550 nm, respectively. Warburg impedance element values were determined from the equivalent circuit model. Also, calculated charges were determined for bleaching or coloring process for all films.

Novel synthesis of poly(2-acryloyloxyethyl ferrocenecarboxylate) as quasi-reversible redox-active gel polymer electrolytes

In this research, the electrochemical behavior of poly(2-acryloyloxyethyl ferrocenecarboxylate) (PAEFc) synthesized via an atom transfer radical polymerization (ATRP) strategy was investigated in a series of tetrabutylammonium perchlorate (TBAP)/acetonitrile vs. Ag/AgNO3 system. In comparison, series of PAEFc electrolyte with specific molecular weight and depositing concentration were analyzed via cyclic voltammetry (CV) method. Furthermore, chronocoulometry (CC) technology has been employed on the dynamic electron/mass transfer mechanism and the determination of kinetic parameters (diffusion coefficients, reaction rate constant, etc.). Finally, it is demonstrated that anodic and cathodic process of PAEFc was controlled by diffusion and adsorption–diffusion, respectively. Meanwhile, the kinetic parameters of the typical quasi-reversible redox process were obtained, of which the apparent activation energy (Ea) and pre-exponential factor (A) were 121.38 kJ mol−1 4.28 × 1018 s−1, respectively.

Multi-Channel Immunoassay System with Electrochemical Detection Toward Point-of-Care Diagnostics Using Magnetic Nanoparticles

Multi-Channel Immunoassay System with Electrochemical Detection Toward Point-of-Care Diagnostics Using Magnetic Nanoparticles

Highly electrochemical performance of Ni-ZIF-8/ N S-CNTs/CS composite for simultaneous determination of dopamine, uric acid and L-tryptophan

The accurate simultaneous determination and quantification of biological small molecules including dopamine (DA), uric acid (UA) and L-tryptophan (L-Trp) are necessary to diagnose or monitor possible disease, which further provide important information about the interaction between these analytes during the physiological processes. In this present work, a novel and rapid electrochemical sensor toward the simultaneous determination of dopamine (DA), uric acid (UA) and L-tryptophan (L-Trp) was prepared based on modification of Ni-ZIF-8/N S-CNTs/CS composite upon the bare glassy carbon electrode. The electrochemical response of DA, UA and L-Trp on the Ni-ZIF-8/N S-CNTs/CS/GCE was explored via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), chronocoulometry (CC) and differential pulse voltammetry (DPV) techniques. The results illustrated that these three analytes displayed the well-resolved and intense electrochemical signals on the designed electrode, owing to the synergic effect originating from Ni-ZIF-8 with highly porous framework structure and N S-CNTs with excellent conductivity. The voltammetric response of Ni-ZIF-8/N S-CNTs/CS/GCE indicated its outstanding electrocatalytic performance for the electrochemical reaction of DA, UA and L-Trp with a wide linear ranges of 8∼500 μM, 1∼600 μM and 5∼850 μM and low detection limits of 0.93, 0.41 and 0.69 μM, respectively. More importantly, the proposed sensor was successfully applied to measure DA, UA and L-Trp in the real samples, meaning that the present method delivered great potential in the field of routine sensing applications.

A novel electrochemical DNA biosensor for transgenic soybean detection based on triple signal amplification

A novel electrochemical DNA biosensor was developed and MON89788 of soybean transgenic gene sequence was detected based on a strategy of rolling circle amplification (RCA) and gold nanoparticle cube (AuNPC)-labeled multiple probes. First, the mercapto-modified capture DNA was immobilized on the surface of the Fe3O4@Au magnetic nanoparticles via an Au–S bond, and the capture DNA was opened and complementarily hybridized with the target DNA to form a double-stranded DNA. In the 10 × reaction buffer, Exonuclease III (ExoIII) specifically recognized and sheared the double-stranded DNA to release the target DNA, which led to the next round of reaction. Afterward, AuNP cube-loaded ssDNA (AuNPC/DNA) was added with the rolling circle reaction with the help of Phi29 DNA polymerase and T4 ligase. Finally, [Ru(NH3)6]3+ was attracted directly by the anionic phosphate of ssDNA via electrostatic interaction. The determination was carried out by using chronocoulometry (CC), and the CC signal was recorded. The mass amount of DNA strands extended infinitely on the AuNPs cube and numerous [Ru(NH3)6]3+ were absorbed, thus the detected signal was highly amplified. The corresponding CC signal showed a good linear relationship with the logarithm of the target DNA concentration in the range of 1 × 10−16 to 1 × 10−7 mol L−1, with a detection limit of 4.5 × 10−17 mol L−1. Specific gene sequence of MON89788 in soybean samples was determined, and the recoveries ranged from 97.3% to 102.0%. This sensor is one of the most sensitive sensors for genetic sequence assessment at present. Moreover, it demonstrates good selectivity, stability, and reproducibility.