Search Results (378)

Films of a Ni/Al-layered double hydroxide intercalated with reduced graphene oxide were deposited, by means of a simple and rapid electrochemical synthesis, on Pt electrodes previously submitted to a special cleaning procedure. The aim of the research was to determine whether the better electrocatalytic properties of the Ni(III)/Ni(II) couple, due to the presence of the carbon nanomaterial, as compared to the Ni/Al-LDH alone, could allow glucose detection at physiological pHs, as normally LDHs work as redox mediators in basic solutions. Chronoamperometric experiments were carried out by applying a potential of 1.0 V vs. SCE to the electrode soaked in solutions buffered at pHs from 5.0 to 9.0 to which glucose was continuously added. The steady-state currents increased as the pH solution increased, but at pH = 7.0 the modified electrode exhibited a fast and rather sensitive response, which was linear up to 10.0 mM glucose, with a sensitivity of 0.56 A M⁻¹ cm⁻² and a limit of detection of 0.05 mM. Our results suggest the potential application of Ni/Al-LDH(ERGO) composite for the non-enzymatic detection of glucose or other oxidizable analytes under biological conditions. Full article

A new approach in amperometric enzyme electrodes production based on all-electrochemically assisted procedures will be described. Enzyme (glucose oxidase) immobilization was performed by in situ co-crosslinking of enzyme molecules through electrophoretic protein deposition, assuring enzyme immobilization exclusively onto the transducer surface (Pt electrode). Analogously, the poor selectivity of the transducer was dramatically improved by the electrosynthesis of non-conducting polymers with built-in permselectivity, permitting the formation of a thin permselective film onto the transducer surface, able to reject common interferents usually found in real samples. Since both approaches required a proper and distinct electrochemical perturbation (a pulsed current sequence for electrophoretic protein deposition and cyclic voltammetry for the electrosynthesis of non-conducting polymers), an appropriate coupling of the two all-electrochemical approaches was assured by a thorough study of the likely combinations of the electrosynthesis of permselective polymers with enzyme immobilization by electrophoretic protein deposition and by the use of several electrosynthesized polymers. For each investigated combination and for each polymer, the analytical performances and the rejection capabilities of the resulting biosensor were acquired so to gain information about their sensing abilities eventually in real sample analysis. This study shows that the proper coupling of the two all-electrochemical approaches and the appropriate choice of the electrosynthesized, permselective polymer permits the easy fabrication of novel glucose oxidase biosensors with good analytical performance and low bias in glucose measurement from typical interferent in serum. This novel approach, resembling classical electroplating procedures, is expected to allow all the advantages expected from such procedures like an easy preparation biosensor, a bi-dimensional control of enzyme immobilization and thickness, interferent- and fouling-free transduction of the electrodic sensor and, last but not the least, possibility of miniaturization of the biosensing device. Full article

Celiac disease (CD), a human leukocyte antigen-associated disorder, is caused by gluten sensitivity and is characterized by mucosal alterations in the small intestine. Currently, its diagnosis involves the determination of serological markers. The traditional method for clinically determining these markers is the enzyme-linked immunosorbent assay. However, immunosensors offer sensitivity and facilitate the development of miniaturized and portable analytical systems. This work focuses on developing an amperometric immunosensor for the quantification of IgA antibodies against tissue transglutaminase (IgA anti-TGA) in human serum samples, providing information on a critical biomarker for CD diagnosis. The electrochemical device was designed on a polyimide substrate using a novel solid ink of wax and carbon nanofibers (CNFs). The working electrode microzone was defined by incorporating aminofunctionalized TiO₂ nanoparticles (TiO₂NPs). The interactions and morphology of CNFs/wax and TiO₂NPs/CNFs/wax electrodes were assessed through different characterization techniques. Furthermore, the device was electrochemically characterized, demonstrating that the incorporation of CNFs into the wax matrix significantly enhanced its conductivity and increased the active surface area of the electrode, while TiO₂NPs contributed to the immunoreaction area. The developed device exhibited remarkable sensitivity, selectivity, and reproducibility. These results indicate that the fabricated device is a robust and reliable tool for the precise serological diagnosis of CD. Full article

An important class of analytes are volatile organic carbons (VOCs), particularly aliphatic primary alcohols. Here, we report the straightforward modification of a commercially available carbon monoxide sensor to detect a range of aliphatic primary alcohols at room temperature. The mass transport mechanisms governing the performance of the sensor were investigated using diffusion in multiple layers of the sensor to model the response to an abrupt change in analyte concentration. The sensor was shown to have a large capacitance because of the nanoparticulate nature of the platinum working electrode. It was also shown that the modified sensor had performance characteristics that were mainly determined by the condensation of the analyte during diffusion through the membrane pores. The sensor was capable of a quantitative amperometric response (sensitivity of approximately 2.2 µA/ppm), with a limit of detection (LoD) of 17 ppm methanol, 2 ppm ethanol, 3 ppm heptan-1-ol, and displayed selectivity towards different VOC functional groups (the sensor gives an amperometric response to primary alcohols within 10 s, but not to esters or carboxylic acids). Full article

Nitrite (NO₂⁻) has long been recognized as a contaminant of concern due to its detrimental effects on both human health and the environment. As a result, there is a continuing need to develop sensitive, real-time, low-cost, and portable systems for the accurate detection of trace levels of NO₂⁻ in drinking water. We present a novel, low-cost, and easy-to-fabricate amperometric sensor designed for detecting low concentrations of NO₂⁻ in drinking water. The fabrication technique involves the electrodeposition of manganese and copper oxides onto a carbon working electrode. CuO and MnO₂ act synergistically as efficient catalysts for the electrooxidation of nitrite to nitrate (NO₃⁻) thanks to their complementary redox properties. The resulting sensor exhibits high catalytic activity toward the electrooxidation of NO₂⁻, with a sensitivity of 10.83 μA/µM, a limit of detection (LOD) of 0.071 µM, and a good linear dynamic concentration range (0.2–60 µM). The sensor’s performance was evaluated against potential interfering analytes (NO₃⁻, Cl⁻, NH₄⁺, and NH₂Cl), all of which showed negligible interference. Reproducibility (maximum standard deviation 2.91%) and repeatability (usable up to three times) were also evaluated. Full article

Amperometric biosensors (ABSs) and enzymatic biofuel cells (BFCs) share several fundamental principles in their functionality, despite serving different primary purposes. Both devices rely on biorecognition, redox reactions, electron transfer (ET), and advanced electrode materials, including innovative nanomaterials (NMs). ABSs and BFCs, utilizing microbial oxidoreductases in combination with electroactive NMs, are both efficient and cost-effective. In the current study, several laboratory prototypes of BFCs have been developed with bioanodes based on yeast flavocytochrome b₂ (Fcb₂) and alcohol oxidase (AO), and a cathode based on fungal laccase. For the first time, BFCs have been developed featuring anodes based on Fcb₂ co-immobilized with redox NMs on a glassy carbon electrode (GCE), and cathode-utilizing laccase combined with gold–cerium–platinum nanoparticles (nAuCePt). The most effective lactate BFC, which contains gold–hexacyanoferrate (AuHCF), exhibited a specific power density of 1.8 µW/cm². A series of BFCs were developed with an AO-containing anode and a laccase/nAuCePt/GCE cathode. The optimal configuration featured a bioanode architecture of AO/nCoPtCu/GCE, achieving a specific power density of 3.2 µW/cm². The constructed BFCs were tested using lactate-containing food product samples as fuels. Full article

Flow injection analysis (FIA) is widely used in drug screening, neurotransmitter detection, and water analysis. In this study, we investigated the electrochemical sensing performance of glassy graphene electrodes derived from pyrolyzed positive photoresist films (PPFs) via rapid thermal annealing (RTA) on SiO₂/Si and polycrystalline diamond (PCD). Glassy graphene films fabricated at 800, 900, and 950 °C were characterized using Raman spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM) to assess their structural and morphological properties. Electrochemical characterization in phosphate-buffered saline (PBS, pH 7.4) revealed that annealing temperature and substrate type influence the potential window and double-layer capacitance. The voltammetric response of glassy graphene electrodes was further evaluated using the surface-insensitive [Ru(NH₃)₆]^3+/2+ redox marker, the surface-sensitive [Fe(CN)₆]^3−/4− redox couple, and adrenaline, demonstrating that electron transfer efficiency is governed by annealing temperature and substrate-induced microstructural changes. FIA with amperometric detection showed a linear electrochemical response to adrenaline in the 3–300 µM range, achieving a low detection limit of 1.05 µM and a high sensitivity of 1.02 µA cm⁻²/µM. These findings highlight the potential of glassy graphene as a cost-effective alternative for advanced electrochemical sensors, particularly in biomolecule detection and analytical applications. Full article

The operating principle of a fuel cell is attracting increasing attention in the development of self-powered electrochemical sensors (SPESs). In this type of sensor, the chemical energy of the analyzed substance is converted into electrical energy in a galvanic cell through spontaneous electrochemical reactions, directly generating an analytical signal. Unlike conventional (amperometric, voltammetric, and impedimetric) sensors, no external energy in the form of an applied potential is required for the redox detection reactions to occur. SPESs therefore have several important advantages over conventional electrochemical sensors. They do not require a power supply and modulation system, which saves energy and costs. The devices also offer greater simplicity and are therefore more compatible for applications in wearable sensor devices as well as in vivo and in situ use. Due to the dual redox properties of hydrogen peroxide, it is possible to develop membraneless fuel cells and fuel-cell-based hydrogen peroxide SPESs, in which hydrogen peroxide in the analyzed sample is used as the only source of energy, as both an oxidant and a reductant (fuel). This also suppresses the dependence of the devices on the availability of oxygen. Electrode catalyst materials for different hydrogen peroxide reaction pathways at the cathode and the anode in a one-compartment cell are a key technology for the implementation and characteristics of hydrogen peroxide SPESs. This article provides an overview of the operating principle and designs of H₂O₂–H₂O₂ fuel cells and H₂O₂ fuel-cell-based SPESs, focusing on biomimetic and nanozyme catalysts, and highlights recent innovations and prospects of hydrogen-peroxide-based SPESs for (bio)electrochemical analysis. Full article

Electrochemical enzyme biosensors are extensively utilized in clinical analysis and environmental monitoring, yet achieving effective enzyme immobilization while maintaining high activity remains a challenge. In this work, we developed a flow-through enzyme biosensor system using a 3D-printed flow-through electrochemical cell fabricated from commercially available poly (lactic acid). After modification with thiacalixarene-functionalized oligo (lactic acids) (OLAs), the material enabled efficient immobilization of uricase on the inner surface of a replaceable reactor of the cell. Swelling and hydrolytic stability of OLAs in cone, partial cone, and 1,3-alternate conformations were studied, with 1,3-alernate conformation demonstrating superior stability and enzyme immobilization performance. The use of OLAs enhanced immobilization efficiency by over 30% and protected the reactor from swelling, hydrolytic degradation, and enzyme loss. The biosensor was validated for amperometric uric acid determination, with a screen-printed carbon electrode modified with carbon black and Prussian Blue. This modification reduced the cathodic potential for uric acid detection to –0.05 V. The biosensor exhibited a linear detection range of 10 nM to 30 μM with a detection limit of 7 nM, and it performed effectively in artificial urine and synthetic blood plasma. The novel cell design, featuring easy assembly and low-cost replaceable parts, makes this biosensor a promising candidate for routine clinical analysis and other practical applications. Full article

Graphene oxide (GO) and reduced graphene oxides (RGOs) show intrinsic electrocatalytic activity towards the electrocatalytic reduction of H₂O₂. Combining these materials with gold nanoparticles results in highly sensitive electrodes, with sensitivity in the nanomolar range because the electrocatalytic properties of GO and nanoparticles are synergistically enhanced. Understanding the factors influencing such synergy is crucial to designing novel catalytically active materials. In this contribution, we study gold nanostructures having shapes of nanospheres (AuNSs), nanourchins (AuNUs), and nanobowls (AuNBs) combined with GO or electrochemically reduced graphene oxide (ERGO). We investigate the amperometric responses of the hybrid layers to H₂O₂. The AuNUs show the highest sensitivity compared to AuNBs and AuNSs. All materials are characterized by electron microscopy and Raman spectroscopy. Raman spectra are deconvoluted by fitting them with five components in the 1000–1800 cm⁻¹ range (D*, D, D”, G, and D′). The interaction between nanoparticles and GO is visualized by the relative intensities of Raman bands (ID/IG) and other parameters in the Raman spectra, like various D”, D* band positions and intensities. The ID/IG parameter is linearly correlated with the sensitivity (R² = 0.97), suggesting that defects in the graphene structure are significant factors influencing the electrocatalytic H₂O₂ reduction. Full article

Bisphenol A (BPA) is a typical environmental estrogen that is distributed worldwide and has the potential to pose a hazard to the ecological environment and human health. The development of an efficient and sensitive sensing strategy for the monitoring of BPA residues is of paramount importance. A novel electrochemical sensor based on carbon black and carbon nanofibers composite (CB/f-CNF)-assisted signal amplification has been successfully constructed for the amperometric detection of BPA in foods. Herein, the hybrid CB/f-CNF was prepared using a simple one-step ultrasonication method, and exhibited good electron transfer capability and excellent catalytic properties, which can be attributed to the large surface area of carbon black and the strong enhancement of the conductivity and porosity of carbon nanofibers, which promote a faster electron transfer process on the electrode surface. Under the optimized conditions, the proposed CB/f-CNF/GCE sensor exhibited a wide linear response range (0.4–50.0 × 10⁻⁶ mol/L) with a low limit of detection of 5.9 × 10⁻⁸ mol/L for BPA quantification. Recovery tests were conducted on canned peaches and boxed milk, yielding satisfactory recoveries of 86.0–102.6%. Furthermore, the developed method was employed for the rapid and sensitive detection of BPA in canned meat and packaged milk, demonstrating comparable accuracy to the HPLC method. This work presents an efficient signal amplification strategy through the utilization of carbon/carbon nanocomposite sensitization technology. Full article

The use of hydrogen as fuel presents many safety challenges due to its flammability and explosive nature, combined with its lack of color, taste, and odor. The purpose of this paper is to present an electrochemical sensor that can achieve rapid and accurate detection of hydrogen leakage. This paper presents both the component elements of the sensor, like sensing material, sensing element, and signal conditioning, as well as the electronic protection and signaling module of the critical concentrations of H₂. The sensing material consists of a catalyst type Vulcan XC72 40% Pt, from FuelCellStore, (Bryan, TX, USA). The sensing element is based on a membrane electrode assembly (MEA) system that includes a cathode electrode, an ion-conducting membrane type Nafion 117, from FuelCellStore, (Bryan, TX, USA). and an anode electrode mounted in a coin cell type CR2016, from Xiamen Tob New Energy Technology Co., Ltd, (Xiamen City, Fujian Province, China). The electronic block for electrical signal conditioning, which is delivered by the sensing element, uses an INA111, from Burr-Brown by Texas Instruments Corporation, (Dallas, TX, USA). instrumentation operational amplifier. The main characteristics of the electrochemical sensor for hydrogen leakage detection are operation at room temperature so it does not require a heater, maximum amperometric response time of 1 s, fast recovery time of maximum 1 s, and extended range of hydrogen concentrations detection in a range of up to 20%. Full article

Enzyme-based portable amperometric biosensors are precise and low-cost medical devices used for rapid cancer biomarker screening. Sarcosine (Sar) is an ideal biomarker for prostate cancer (PCa). Because human serum and urine contain complex interfering substances that can directly oxidize at the electrode surface, rapid Sar screening biosensors are relatively challenging and have rarely been reported. Therefore, highly sensitive and selective amperometric biosensors that enable real-time measurements within <1.0 min are needed. To achieve this, a chitosan–polyaniline polymer nanocomposite (CS–PANI NC), a carrier for dispersing mesoporous carbon (MC), was synthesized and modified on a screen-printed carbon electrode (SPCE) to detect hydrogen peroxide (H₂O₂). The sarcosine oxidase (SOx) enzyme-immobilized CS–PANI–MC-2 ternary NCs were referred to as supramolecular architectures (SMAs). The excellent electron transfer ability of the SMA-modified SPCE (SMA/SPCE) sensor enabled highly sensitive H₂O₂ detection for immediate trace Sar biomarker detection. Therefore, the system included an SMA/SPCE coupled to a portable potentiostat linked to a smartphone for data acquisition. The high catalytic activity, porous architecture, and sufficient biocompatibility of CS–PANI–MC ternary NCs enabled bioactivity retention and immobilized SOx stability. The fabricated biosensor exhibited a detection limit of 0.077 μM and sensitivity of 8.09 μA mM⁻¹ cm⁻² toward Sar, demonstrating great potential for use in rapid PCa screening. Full article

This work presents the development of an amperometric biosensor for detecting aspartate aminotransferase (AST) activity in biological fluids using a platinum disk electrode as the working transducer. Optimal concentrations of substrates (aspartate, α-ketoglutarate) and the coenzyme (pyridoxal phosphate) were determined to ensure efficient biosensor operation. A semi-permeable poly-m-phenylenediamine membrane was applied to enhance selectivity against electroactive interferents. The biosensor demonstrated good stability (storage, continuous operation, and production reproducibility) and analytical performance (sensitivity 8.56 nA/min for 50 U/L AST, LOD 1 U/L, linear range 1–110 U/L). Testing with real samples showed a high correlation (R = 0.989) with spectrophotometric analysis, supporting its potential for further applications. Full article

We report the development of amperometric biosensors (ABSs) employing flavocytochrome b₂ (Fcb₂) coupled with nanoparticles (NPs) of noble metals on graphite electrode (GE) surfaces. Each NPs/GE configuration was evaluated for its ability to decompose hydrogen peroxide (H₂O₂), mimicking peroxidase (PO) activity. The most effective nanoPO (nPO) was selected for developing ABSs targeting L-lactate. Consequently, several Fcb₂/nPO-based ABSs with enhanced sensitivity to L-lactate were developed, demonstrating mediated ET between Fcb₂ and the GE surface. The positive effect of noble metal NPs on Fcb₂-based sensor sensitivity may be explained by the synergy between their dual roles as both PO mimetics and electron transfer mediators. Furthermore, our findings provide preliminary data that may prompt a re-evaluation of the mechanism of L-lactate oxidation in Fcb₂-mediated catalysis. Previously, it was believed that L-lactate oxidation via Fcb₂ catalysis did not produce H₂O₂, unlike catalysis via L-lactate oxidase. Our initial research revealed that the inclusion of nPO in Fcb₂-based ABSs significantly increased their sensitivity. Employing other PO mimetics in ABSs for L-lactate yielded similar results, reinforcing our hypothesis that trace amounts of H₂O₂ may be generated as a transient intermediate in this reaction. The presence of nPO enhances the L-lactate oxidation rate through H₂O₂ utilization, leading to signal amplification and heightened bioelectrode sensitivity. The proposed ABSs have been successfully tested on blood serum and fermented food samples, showing their promise for L-lactate monitoring in medicine and the food industry. Full article