Development Of Electrochemical Sensors Research Articles

An antifouling electrochemical biosensor using self-signal for Salmonella typhimurium direct detection in food sample

Eating food contaminated by foodborne pathogens can lead to illness. The development of electrochemical sensors for pathogen detection has received widespread attention. However, the analytical performance of electrochemical sensors is inevitably affected by the non-specific adsorption of molecules in the sample. Moreover, the external signal probes might be affected by the complex components in the sample accompanied with signal suppression. This work presents an electrochemical aptasensor for Salmonella typhimurium detection based on the self-signal of poly-xanthurenic acid and the antifouling ability of chondroitin sulfate. The detection time was 60 min. The linear range was from 101 to 107 CFU/mL, and the detection limit was 3 CFU/mL. The biosensors presented good repeatability and storage stability. And the biosensors has been successfully applied in milk and orange juice. This strategy is expected to be applied in the design of other antifouling biosensors, to achieve rapid detection of pathogens and ensure food safety.

Efficient 2-Nitrophenol determination based on ultra-sonochemically prepared low-dimensional Au-nanoparticles decorated ZnO-chitosan nanocomposites by linear sweep voltammetry

In this study, linear sweep voltammetry (LSV) was implemented for the sensitive detection of 2-nitrophenol (2-NP) in phosphate buffer solution (PBS) at pH 7.00 with lab-made nanocomposite materials for environmental remediation. Initially, a flat glassy carbon electrode (GCE) modified using the inorganic-organic binary Au-NPs@ZnO/CTSN(Chitosan) nanocomposites (NCs) was used as a working electrode (WE). The NCs of Au NPs@ZnO/CTSN were basically prepared by an ultra-sonochemical process and fabricated on a GCE using conducting coating binder such as PEDOT:PSS. Before the electrochemical examination, the Au NPs@ZnO/CTSN NC was fully characterized by Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Energy-dispersive X-ray Spectroscopy (EDS), Brunauer-Emmett-Teller (BET), X-Ray Diffraction analysis (XRD), High-Resolution Transmission Electron Microscopy (HRTEM), and X-Ray Photoelectron Spectroscopy (XPS) to analyze the functional, morphological, structural, elemental, surface area, crystallinity, and binding energy analyses. A linear concentration range (LDR) of 2-NP from 15⁓150 μM was evaluated by LSV in room conditions. From the slope of the calibration curve, the sensor sensitivity was calculated and found to be 20.9905 μAμM−1cm−2. At signal/noise ratio of 3, the lower limit of detection (LOD) is obtained as 0.45 ± 0.023 μM. Additionally, pH optimization, sensor-probe characterization, stability, and validity are fully analyzed in identical conditions by LSV. Besides this, the assembled 2-NP sensor probe as Au NPs@ZnO/CTSN NCs/PEDOT:PSS/GCE for validity test was performed elaborately and found the reliable and satisfactory results. This is a new approach to the development of electrochemical sensors for environmental chemical analysis using an electrochemical process with gold-nanoparticle decorated ZnO-chitosan for the safety of environmental and healthcare fields on a broad scale.

Development of surface molecular-imprinted electrochemical sensor for palmitic acid with machine learning assistance

Palmitic acid (PA) is a kind of saturated high fatty acid, which is involved in physiological safety and food quality. A surface molecularly imprinted polymer (MIP) electrochemical sensor was prepared on MXene surface using dopamine (DA) as functional monomer. The electrode was modified with gold nanoparticles (AuNPs), ferrocene-graphene oxide-multiwalled carbon nanotubes (Fc-GO-MWCNT) composite to enhance the electroactive area and conductivity. The sensor was characterized by scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), electrochemical impedance spectroscopy (EIS) and Differential pulse voltammetry (DPV), respectively. The parameters concerning this assay and various regeneration conditions have been carefully studied. The sensor can detect PA in the range of 1 nM-1 mM (R2 = 0.995), the limit of detection (LOD) is 0.48 nM (S/N = 3), and the limit of quantification (LOQ) is 1.61 nM. The artificial neural network (ANN) model in machine learning is further used to analyze the data collected by the sensor. The results show that the back propagation (BP) neural network in ANN is more suitable for the intelligent analysis of PA. The practicality of the sensor was confirmed by detecting PA in pork samples. This is the first MIP-based electrochemical sensor for PA, and it has great potential in practical applications.

Electrochemical detection of regorafenib using a graphite sheet electrode modified with nitrogen-doped reduced graphene oxide nanocomposite

Regorafenib (RGF) is a multi-kinase inhibitor drug used for treating various cancers, posing challenges for detection in biological samples due to low solubility and stability. This paper presents a novel electrochemical sensor based on a monolith reduced graphene oxide (M-RGO) nanocomposite modified graphite sheet electrode. M-RGO was synthesized via a hydrothermal method and characterized extensively. The electrochemical performance was assessed using cyclic voltammetry and differential pulse voltammetry. The sensor demonstrated exceptional electrocatalytic activity for RGF oxidation, featuring two linear response ranges (31 nM to 600 nM and 600 nM to 920 nM) with a detection limit of 1.7 nM. The sensor exhibited good selectivity, stability, and reproducibility. Successful application in determining RGF in human serum and urine samples demonstrated the potential of M-RGO nanocomposite as a promising material for the development of electrochemical sensors for pharmaceutical analysis.

Thiourea‐Modified Multiwalled Carbon Nanotubes as Electrochemical Biosensor for Ultra‐Precise Detection of Dopamine

Functionalized multi‐walled carbon nanotubes (MWCNTs) have enticed remarkable attention in the field of electrochemical sensing applications. Dopamine (DA) is a monoamine neurotransmitter released in the brain acting as a chemical messenger that communicates messages between nerve cells and the rest of the body. Therefore, there is a significant technological urge for the development of electrochemical sensors for DA in body fluids. In this context, nitrogen‐functionalized MWCNTs (TM‐CNT600) were fabricated by thermal annealing of carboxylic acid functionalized MWCNTs with thiourea at 600 oC under N2 atmosphere. The XPS spectrum reveals the presence of nitrogen‐containing functionalities in the as‐prepared TM‐CNT600. FTIR results show the presence of ‐OH, C‐N and C‐S functional groups. XPS further corroborates the FTIR results and quantifies the predominant functional groups in as‐prepared material. The material was investigated as a potential electrochemical sensor for the detection of dopamine (DA). In the case of TM‐CNT600/GCE, a linear relationship for DA concentration was observed in the range of 10.7 ‐ 24.2 μM with the limit of detection (LOD) of 1.42 μM using linear sweep voltammetry (LSV). These results highlight the potential of TM‐CNT600 modified GCE as an efficient sensor for the electrochemical detection of DA in body fluids.

Carbons confined silver nanoclusters decorated carbon fiber electrodes toward electrochemical sensor of dihydroxyphenol and heavy metal ions

The development of electrochemical sensors based on noble metals has presented remarkable opportunities and challenges for the detection of trace phenols and heavy metal ions. However, the high costs of precious metals hinder the practical implementation of electrode materials. Enhancing the utilization efficiency of precious metals on the electrode surface is a crucial step toward improving electrochemical sensors based on these valuable materials. In this study, the morphology and utilization rate of silver nanoparticles were regulated by decorating nanofilms with different dimensions on carbon fiber electrodes. Specifically, the polypyrrole-derived carbon film coating enabled the material to have a large electroactive area and silver loading capacity. Simultaneously, the limiting effect of graphene quantum dots formed silver nanoparticles into silver clusters and achieved excellent electrochemical detection performance for dihydroxyphenol and heavy metal ions. Compared with silver nanoparticles, silver clusters provide higher electrocatalytic power and atomic utilization of silver. This study provides technical support for the trace analysis of environmental pollutants.

Development of a novel sensor for the detection of donepezil hydrochloride as Alzheimer's disease drug utilizing CuO-TiO2 hybrid nanostructures

In this study, donepezil hydrochloride (DZ HCl), a crucial medication for the treatment of Alzheimer's disease, is detected using a new sensor built on CuO-TiO2 hybrid nanostructures. The sensor showed improved performance characteristics with a computed limit of quantitation of 0.211 and a limit of detection of 0.063. These qualities included improved stability, selectivity, and sensitivity. The fabrication process demonstrated repeatability, with a 4.27% relative standard deviation. After 10 successive readings, the sensor maintained 95% of its initial response, demonstrating its long-term stability. By quantifying DZ HCl in urine samples, the practical applicability of the sensor was confirmed. Remarkably, the sensor achieved a remarkable recovery rate of 97.00–99.41% and a suitable relative standard deviation range of 3.29–4.71%. The results of this work contribute to the development of trustworthy electrochemical sensors for medicinal chemicals and have prospective uses in pharmacological, biological, and therapeutic fields.

Unraveling the Potential of a Nanostructured Tungsten–Tungsten Oxide Thin Film Electrode as a Bioresorbable Multichemical Wound Healing Monitor

AbstractRecent advancements in wearable technology have led to a new era of intelligent wound dressings capable of monitoring vital healing biomarkers. While a significant leap from traditional gauze dressings, these innovations still necessitate periodic removal and disposal. Bioresorbable electrochemical sensors have emerged as a promising and sustainable solution, offering continuous monitoring of critical wound healing biomarkers in real‐time and in situ, followed by their full physiological resorption. The current challenge lies in the susceptibility of metallic electrodes to harsh electrolytic biofluids, hindering the development of viable transient electrochemical sensors. This study pioneers a bioresorbable electrochemical material and unique architecture comprising engineered sputtered tungsten (W) plus tungsten oxide (WOx) thin films, taking advantage of their high catalytic activity and uniquely gradual biodissolution. While a bare W film electrode detached from the wafer substrate within 5 hours of soaking, an annealed W‐WOx electrode showcases a notable electrochemical stability at body temperature, for up to several days. The latter reliably senses multiple analytes during 24‐hour room‐temperature tests. These findings underscore the potential of annealed W plus WOx electrodes in future bioresorbable wound management systems.

Non-enzymatic glucose sensor using mesoporous carbon screen-printed electrodes modified with cobalt phthalocyanine by phase inversion

The development of non-enzymatic glucose electrochemical sensors is still required to be used for the determination of glucose in complex biological media. This study presents a straightforward and remarkably efficient tool for the preparation of highly stable and sensitive glucose electrochemical sensors based on the deposition of cobalt phthalocyanine (CoPc) onto mesoporous carbon screen-printed electrodes (MCs). Results show that the MC electrochemical activation (aMC) followed by phase inversion (PI), which consisted of drop casting of CoPc in dimethylformamide onto a wetting electrolyte leading to the electrode aMC-CoPc/PI, enhanced sensitivity towards glucose determination in complex media. The beneficial need for MC surface activation and PI has been explored by scanning electron microscopy, energy dispersive X-ray spectroscopy, Raman spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The aMC-CoPc/PI electrode exhibited the highest electrocatalytic activity of the series (namely, MC-CoPc, MC-CoPc/PI and aMC-CoPc) towards glucose oxidation. By using square wave voltammetry technique, the aMC-CoPc/PI glucose electrochemical sensor demonstrated a sensitivity of 22.3 µA mM−1 and a low detection limit of 27.4 µM (S/N = 3) in a linear dynamic range of 0.1 to 3.5 mM. Additionally, it also displayed high selectivity, robust stability, repeatability and reproducibility toward the quantification of glucose concentration in complex samples such as horse serum, intravenous glucose saline solution and culture medium for sperm cells.

Methanol detection with Au-nanoparticles decorated-PPyC-SnO2 nanocomposites using PEDOT:PSS polymer by differential pulse voltammetry

In this approach, sensitive development of methanol electrochemical sensor based on Au-nanoparticles decorated polypyrrole carbon with tin dioxide nanocomposites (Au NPs-PPyC-SnO2 NCs) were prepared and deposited onto glassy carbon electrode (GCE) to make sensor probe using PEDOT:PSS polymer as a conducting binder. The newly developed Au NPs-PPyC-SnO2 NCs were prepared through wet chemical and photo-reduction techniques in lab-made experimental scales, resulting in a morphology that promotes electrochemical reactions for detecting unsafe methanol under ambient conditions using three-electrode systems by differential pulse voltammetry (DPV). The sensor exhibited higher sensitivity (4.2373 µAµM-1cm−2), lower limit of detection (LOD; 2.39 ± 0.12 µM), and a wide linear detection range (LDR; 30.0 to 300.0 µM), which measured from the slope of the calibration curve from concentration variation analyses by considering the active surface area of the coated GCE. To validate its practical application, the fabricated Au NPs-PPyC-SnO2 NCs/GCE sensor electrode was tested for several real samples. It was found a satisfactory performance in the detection of methanol that was observed by using the electrochemical DPV technique with the recovery approach for the fabricated Au NPs-PPyC-SnO2 NCs/GCE sensor probe. It has introduced a new route for the sensitive detection of target methanol with gold-decorated nanocomposite materials in the protection of environmental and ecological fields using an electrochemical approach on a large scale.

Electro-sensing of biocide and its applications based on the Ru-doped TiO2 and reduced GO nanocomposite fabricated electrode

In this study, we utilized a carbon paste electrode (CPE) that had been modified with reduced graphene oxide nanoparticles (rGO) and ruthenium-doped TiO2 nanoparticles (Ru–TiO2) to conduct an electrochemical investigation of triclosan (TCS). To characterize the synthesized Ru–TiO2 nanoparticles, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were utilized. Electrochemical impedance spectroscopy was employed to characterize the fabricated Ru–TiO2/rGO/CPE and bare CPE. “The heterogeneous rate constant, the pH study, the accumulation time, the scan rate, and the concentration fluctuation were investigated. Combining several electrocatalytic modifiers allows for the development of effective electrochemical sensors. Ru–TiO2 and rGO nanostructures are two examples of these modifiers. As a result of its great sensitivity, selectivity, and application to the measurement of TCS, nanostructured Ru–TiO2 and rGO are highly recommended in this research. At a pH of 9.2 in PBS, the sensitivity range of a Ru–TiO2/rGO/CPE was investigated by testing its response to a calibration plot of TCS concentrations ranging from 1.0 × 10−8 M to 2.2 × 10−7 M. Voltammetric techniques such as square wave voltammetry (SWV) and cyclic voltammetry (CV) were used to determine the electrochemical components that comprise TCS. The developed sensor was also employed to detect and analyze TCS levels in actual samples, including those of fruits, vegetables, water, and soil.”

Simple Fabrication of Mesoporous Praseodymium Cerate via an Eco-Friendly Route for Development of Carbendazim Electrochemical Sensor

Abstract This study introduces an easy and efficient ultrasonic-assisted approach for the preparation of mesoporous praseodymium cerate (MS-Pr2Ce2O7) by employing maltose as a novel and eco-friendly capping agent. Some techniques such as field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used for the characterization of nanoparticles. For the detection of carbendazim (CBZ), a new electrochemical sensor based on the modified screen-printed electrode (SPE) has been presented. The modification of the electrode surface was made using of praseodymium cerate. Cyclic voltammetry (CV) has been utilized to study the electrochemical behavior of the MS-Pr2Ce2O7/SPE and better electrochemical performance was observed compared to bare SPE for the oxidation of CBZ. The optimization of pH and accumulation time was done. Under optimized conditions (pH=7 and accumulation time:160 s), the oxidation peak currents that responded to CBZ concentration between 0.01 and 175.0 µM exhibited a linear relationship (R2 = 0.9977) and the detection limit was calculated 4.6 nM. In addition, MS-Pr2Ce2O7/SPE showed high stability and repeatability. At last, real sample tests of the MS-Pr2Ce2O7/SPE were validated by applying them to the detection of CBZ in vegetable samples, which were found to be promising in our preliminary experiments.

Nonenzymatic Potentiometric Detection of Ascorbic Acid with Porphyrin/ZnO-Functionalized Laser-Induced Graphene as an Electrode of EGFET Sensors.

Laser-induced graphene (LIG) has emerged as a highly versatile material with significant potential in the development of electrochemical sensors. In this paper, we investigate the use of LIG and LIG functionalized with ZnO and porphyrins-ZnO as the gate electrodes of the extended gate field effect transistors (EGFETs). The resultant sensors exhibit remarkable sensitivity and selectivity, particularly toward ascorbic acid. The intrinsic sensitivity of LIG undergoes a notable enhancement through the incorporation of hybrid organic-inorganic materials. Among the variations tested, the LIG electrode coated with zinc tetraphenylporphyrin-capped ZnO nanoparticles demonstrates superior performance, reaching a limit of detection of approximately 3 nM. Furthermore, the signal ratio for 5 μM ascorbic acid relative to the same concentration of dopamine exceeds 250. The practical applicability of these sensors is demonstrated through the detection of ascorbic acid in real-world samples, specifically in a commercially available food supplement containing l-arginine. Notably, formulations with added vitamin C exhibit signals at least 25 times larger than those without, underscoring the sensors' capability to discern and quantify the presence of ascorbic acid in complex matrices. This research not only highlights the enhanced performance of LIG-based sensors through functionalization but also underscores their potential for practical applications in the analysis of vitamin-rich supplements.

Recent Trends in Nanomaterial Based Electrochemical Sensors for Drug Detection: Considering Green Assessment.

An individual's therapeutic drug exposure level is directly linked to corresponding clinical effects. Rapid, sensitive, inexpensive, portable and reliable devices are needed for diagnosis related to drug exposure, treatment, and prognosis of diseases. Electrochemical sensors are useful for drug monitoring due to their high sensitivity and fast response time. Also, they can be combined with portable signal read-out devices for point-of-care applications. In recent years, nanomaterials such as carbon-based, carbon-metal nanocomposites, noble nanomaterials have been widely used to modify electrode surfaces due to their outstanding features including catalytic abilities, conductivity, chemical stability, biocompatibility for development of electrochemical sensors. This review paper presents the most recent advances about nanomaterials-based electrochemical sensors including the use of green assessment approach for detection of drugs including anticancer, antiviral, anti-inflammatory, and antibiotics covering the period from 2019 to 2023. The sensor characteristics such as analyte interactions, fabrication, sensitivity, and selectivity are also discussed. In addition, the current challenges and potential future directions of the field are highlighted.

Gold nanowires-based sensor for quantification of H2O2 released by human airway epithelial cells

Hydrogen peroxide (H2O2) is a biomarker relevant for oxidative stress monitoring. Most chronic airway diseases are characterized by increased oxidative stress. To date, the main methods for the detection of this analyte are expensive and time-consuming laboratory techniques such as fluorometric and colorimetric assays. There is a growing interest in the development of electrochemical sensors for H2O2 detection due to their low cost, ease of use, sensitivity and rapid response. In this work, an electrochemical sensor based on gold nanowire arrays has been developed. Thanks to the catalytic activity of gold against hydrogen peroxide reduction and the high surface area of nanowires, this sensor allows the quantification of this analyte in a fast, efficient and selective way. The sensor was obtained by template electrodeposition and consists of gold nanowires about 5 μm high and with an average diameter of about 200 nm. The high active surface area of this electrode, about 7 times larger than a planar gold electrode, ensured a high sensitivity of the sensor (0.98 μA μM−1cm−2). The sensor allows the quantification of hydrogen peroxide in the range from 10 μM to 10 mM with a limit of detection of 3.2 μM. The sensor has excellent properties in terms of reproducibility, repeatability and selectivity. The sensor was validated by quantifying the hydrogen peroxide released by human airways A549 cells exposed or not to the pro-oxidant compound rotenone. The obtained results were validated by comparing them with those obtained by flow cytometry after staining the cells with the fluorescent superoxide-sensitive Mitosox Red probe giving a very good concordance.

Voltammetric behavior of solifenacin succinate on gold, glassy carbon and boron-doped diamond electrodes: Stability testing and determination

The anticholinergic drug, solifenacin, is frequently used for the treatment of the urological tract for urinary incontinence, and urinary frequency. The development of reliable and effective solifenacin electrochemical sensors is of great importance for the pharmaceutical industry and clinical practice. In this work, the electrochemical behavior of solifenacin succinate (SOL) was studied using three different working electrodes: gold (Au), glassy carbon (GCE) and boron-doped diamond electrode (BDDE). The cyclic voltammetric (CV) measurements performed in 0.05 M NaHCO3 indicated that the SOL oxidation process is irreversible and diffusion-controlled at all investigated working electrodes. Afterwards, the testing of SOL electrochemical stability and the possibility of its electrochemical degradation was performed at the Au electrode by the cycling of the potential during 3 h and continuously to 6 h. It was shown that the SOL was electrochemically transformed into another electroactive species and its degradation was excluded. For electroanalytical application, the anodically pretreated BDDE (+2.0 V; 30 s) was selected. Various experimental parameters were optimized, including the pH of the aqueous Britton-Robinson (B-R) buffer as a supporting electrolyte (from pH 2.0 to 11.98) and the most intensive peak of the target analyte was at pH 11.0, so this pH value was chosen as the optimum for further measurements. Based on the correlation of the SOL peak intensity and different concentrations, the developed differential pulse voltammetric (DPV) method was characterized by a linear concentration range from 0.041 to 2.50 µM, with a correlation coefficient of 0.999, and a relative standard deviation of 0.3 %. Taking into account the sensitivity of the developed DPV method towards the electrochemical oxidation of SOL, a very low detection limit of 0.012 µM in the model system was achieved. The BDDE showed adequate selectivity for SOL in the presence of the investigated interferents. The obtained results indicate that the BDDE with an optimized DPV method could be applied for the trace-level electroanalytical determination of SOL in human urine sample with excellent recovery and reproducibility.

PH-Tuned Enantioselectivity Reversal in a Defective Chiral Metal Organic Framework.

The introduction of chirality into easy-scalable metal-organic frameworks (MOFs) gives rise to the development of advanced electrochemical sensors. However, integrating chirality by directly connecting metal ions and chiral ligands is unpredictable. Postmodification synthesis is a common method for synthesizing chiral MOFs, but it reduces the size of chiral channels and poses obstacles to the approach of chiral guest molecules. In this work, missing connection defects were introduced into the chiral MOFs through defect engineering strategies, which enhance the recognition of the target enantiomers. pH can tune enantioselectivity reversal in defective chiral MOFs. The chiral MOFs show enantioselectivity for d-Trp at pH = 5 and l-Trp at pH = 8. From the results of zeta potential, regardless of pH 5 or 8, the chiral MOF has a positive potential. The chiral MOFs are positively charged, while tryptophan is negatively charged when pH = 8. The difference in the positive and negative charge interactions between the two amino acids and chiral MOFs leads to chiral recognition. However, the difference in π-π interaction between chiral MOF and Trp enantiomers mainly drives chiral recognition under pH = 5. This study paves a pathway for the synthesis of defective chiral MOFs and highlights the pH-tuned enantioselectivity reversal.

Metal organic framework (MOF): Synthesis and fabrication for the application of electrochemical sensing

Metal-organic frameworks (MOF) are a class of porous hybrid materials of metal ions linked by organic bridging ligands. These materials consist of different families of crystalline frameworks with metal ions and metal-ion clusters linked by the coordination bonds with suitable organic ligands. These porous materials possess high surface area, variable pore sizes, various functions, and excellent thermal stability. As a result, these unique and tailored MOF materials found varied applications in electrochemical sensor development. The review critically examines the approach to synthesizing a wide range of MOF compounds. The utilization of MOF in fabricating a small-scale sensor device demonstrates the ability to detect various water contaminants in aquatic environments. Moreover, it showcased an in-depth advancement in sensor and device development utilizing MOFs materials. The efficient use of electrochemical sensors is discussed critically and presents these studies’ challenges and future perspectives.

Accurate and Rapid Determination of Ammonium in Water by Voltametric Analysis on a Novel Modified Electrode

The development of efficient and sensitive electrochemical sensors is of crucial for a wide range of applications, including environmental monitoring, chemical analysis, and biomedical diagnostics. In this study, we present on the development and characterization of a novel of electrochemical sensor, based on a silver/poly 1-aminoanthraquinone/glassy carbon modified electrode (Ag/PAAQ/GC), with high sensitivity and selectivity for the detection of ammonium ions (NH4 +) in water. The Ag/PAAQ/GC electrode was prepared by a simple and low- cost electrochemical co-deposition method, which enabled for a uniform and stable deposition of PAAQ and Ag ions on the surface of the GC electrode. The resulting electrode exhibited excellent electrocatalytic activity in the oxidation of NH4 + ions. The performance of the Ag/PAAQ/GC electrode as an electrochemical sensor for NH4 + was evaluated using square wave voltammetry (SWV) in aqueous solutions. The results showed that the Ag/PAAQ/GC electrode exhibited a linear response to NH4 + in a concentration range of 0.01 to 9 mgL−1, with a detection limit of 3 μgL−1 and a sensitivity of 0.0413 μA.Lmg−1. In addition, the Ag/PAAQ/GC electrode showed excellent selectivity for NH4 + over interfering ions such as K+, Na+, Ca2+, and Mg2+. Overall, our results show that the Ag/PAAQ/GC electrode is a promising platform for the development of advanced electrochemical sensors for the detection of NH4 + in water. Due to its high sensitivity, selectivity and stability, the Ag/PAAQ/GC electrode is suitable for a wide range of environmental and analytical applications, e.g., water quality monitoring, wastewater treatment and fertiliser analysis. The precision of the method was tested by analysing sixteen measurements of the same NH4 + concentration, yielding standard deviation (RSD) of 1.78%. Good recovery values were obtained when measuring spiked tap water samples analysed by the classical Colorimetric Nessler reagent methods and measuring natural water by the ion-selective electrode.

One-step prepared of e-Gelatin-CNTs nano-composite fiber modified carbon fiber microelectrode for continuous dopamine monitoring: Characterization, biocompatibility evaluation and in vivo experiment

Fabricating electrochemical sensor capable of stable sensing in complex organism's environment will undoubtedly underpin key in the development of implanted electrochemical sensor. However, nonspecific protein adsorption can greatly reduce sensing sensitivity of electrode due to the abundance of protein in vivo. Herein, we aim to fabricating a modified layer of good protein adsorption resistance. The nano-composite fibers from gelatin with good hydrophily and multiwall carbon nanotubes (CNTs) for constructing on the surface of carbon fiber microelectrode using one-step electrospinning technology (e-Gelatin-CNTs/CFME). A comprehensive discussing on the protein adsorption resistance of e-Gelatin-CNTs/CFME that are, through the use of SEM, AFM, water contact angle, UV–vis, cyclic voltammetry and I-T. The resulting electrochemical sensor revealed stable sensing sensitivity in protein solution, a slightly decrease (0.02nA/μM). Furthermore, the sensor was successfully used for the detection of DA in human blood. More remarkable, e-Gelatin-CNTs nano-composite fibers presented excellent biocompatibility, which could meet the biosafety as implantation materials in vivo. This work provided a platform for the development of implantable electrochemical sensor.