Search Results (801)

The rapid detection of organophosphorus (OP) compounds is crucial for safeguarding human health and ensuring food safety. This study presents a novel wearable electrochemical biosensor that integrates miniaturized screen-printed electrodes with wearable devices to achieve real-time, on-site OP detection. The biosensor was fabricated by constructing a screen-printed carbon electrode (SPCE) on a thermoplastic polyurethane (TPU) substrate, sequentially modified with graphene (GR), gold nanoparticles (AuNPs), and organophosphorus hydrolase (OPH), and finally encapsulated with Nafion. This SPCE/GR/AuNPs/OPH/Nafion configuration yields a highly flexible and portable device. The detection principle relies on the enzymatic hydrolysis of methyl paraoxon (MPOX) by OPH, generating p-nitrophenol (PNP), which is quantitatively measured via square wave voltammetry (SWV). The sensor exhibits a broad linear detection range (30–400 μM) with a strong linear correlation (R² = 0.995) and a low detection limit (0.321 μM). It demonstrates excellent selectivity against common interfering substances, including urea, sucrose, and various metal ions. Application to real-world samples such as cabbage and tap water yielded high recoveries (107.2% for cabbage and 101.2% for tap water), with relative standard deviations (RSDs) below 8%. Furthermore, the biosensor maintains robust flexibility and mechanical resilience, with less than 5% signal loss after 100 bending cycles, confirming its suitability for wearable applications and reliable operation under mechanical stress. This innovative, flexible electrochemical biosensor provides a powerful and reliable platform for rapid OP detection, particularly in complex testing environments. Full article

Nonsteroidal anti-inflammatory drugs such as phenylbutazone (PBZ) are among the most widely used medications globally due to their effectiveness in relieving pain and reducing inflammation. This study aims to detect PBZ with metallic particle-based electrochemical sensors using cyclic voltammetry (CV) in the presence of catechol as a redox probe. The approach focuses on evaluating the electrochemical behaviour of PBZ under different experimental conditions and optimizing the detection parameters to develop a simple, rapid, and cost-effective analytical method suitable for this pharmaceutical compound in lab practice. CV was performed using four types of screen-printed electrodes, each modified with different transitional metal particles, in potassium ferrocyanide/potassium ferricyanide, catechol, and catechol-PBZ solutions to study the electrochemical response and detection capability for PBZ. The best performance characteristics were obtained for the sensor modified with Ir particles that detect PBZ, with a linearity range of 0.01 to 1.00 μM and a detection limit of 1.53 nM. Additionally, Fourier-transform infrared spectroscopy (FT-IR) was used to characterize the PBZ in pharmaceuticals. The method using an iridium-modified sensor developed in this study allows the accurate detection of PBZ in pharmaceuticals with a relative error lower than 4%. Full article

The increasing demand for continuous physiological monitoring has accelerated the development of high-sensitivity wearable electrochemical platforms. This study reports the fabrication of a multi-analyte electrochemical sensor based on single-walled carbon nanotubes (SWCNTs) for the detection of sweat-associated metabolites. To facilitate efficient heterogeneous electron transfer, glucose oxidase (Gox), lactate oxidase (Lox), and urease (Ure) were immobilized onto the SWCNT network through π–π interaction using 1-pyrenebutanoic acid succinimidyl ester (PBSE), followed by additional stabilization via 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)/N-hydroxysuccinimide (NHS) coupling. The developed platform exhibited concentration-dependent resistance responses within the ranges of 0.02–0.20 mM for glucose, 20–100 mM for lactate, and 50–400 mM for urea under controlled experimental conditions. The resistance-based configuration enabled stable and reproducible signal modulation across these concentration intervals. Although direct testing with human sweat was not performed, the electrochemical behavior of key sweat-related metabolites was systematically evaluated as a preparatory step toward future wearable integration. Full article

Hematocrit (HCT) fluctuations and ambient temperature variations are two critical interference factors limiting the accuracy of electrochemical glucose test strips in self-monitoring of blood glucose (SMBG). In this study, a high-precision screen-printed glucose sensor incorporating in situ impedance-based HCT correction and temperature compensation was developed. The system employs a time-division multiplexing strategy, integrating a normalized thermodynamic model and an in situ impedance-based HCT correction algorithm, to achieve synergistic decoupling and precise compensation of temperature and HCT interferences. Experimental results demonstrate that after multi-parameter synergistic correction, the system exhibits excellent stability across a wide temperature range (10–35 °C) and a broad HCT range (10–70%). The accuracy indicators significantly surpass ISO 15197:2013 standards. In contrast, uncorrected measurements showed deviations ranging from approximately −80% to +30% due to HCT fluctuations. This multiple correction strategy effectively resolves systematic errors in whole blood testing without increasing electrode complexity or requiring pretreatment steps, providing a robust technical solution for high-precision, low-cost personal glucose monitoring. Full article

Electrochemical sensors are user-friendly devices designed for the rapid and straightforward detection of target analytes. Serotonin (5-hydroxytryptamine, 5-HT) is a key neurotransmitter and neuromodulator that regulates diverse neuronal processes. Using a custom-designed screen-printed carbon electrode (SPCE) incorporating ordered mesoporous carbon–bimetal oxides of Cu and Ni (CuO–NiO–OMC), rapid and real-time detection of 5-HT was achieved. The CuO–NiO–OMC structure featured highly active CuO and NiO catalytic sites that effectively promoted the irreversible oxidation of 5-HT (vs. Ag/AgCl reference electrode). The CuO–NiO–OMC/SPCE sensor, connected to a portable potentiostat, exhibited exceptional electrocatalytic performance for the oxidation of 5-HT, with a detection limit of 42.5 nM. The sensitivity was 1.56 A M⁻¹ cm⁻², and the linear dynamic range was 0.0–80.0 µM. The CuO–NiO–OMC/SPCE sensor also demonstrated outstanding selectivity in the presence of competing neurochemicals, including norepinephrine, epinephrine, dopamine, and glutamate, as well as high concentrations of tested biomolecules and inorganic ions. Furthermore, the practicality of the sensor was demonstrated using human serum and urine samples, with recovery percentages ranging from 91.1% to 98.3%. Thus, the CuO–NiO–OMC/SPCE sensor offers an effective approach for 5-HT sensing, thereby permitting molecular-level understanding of brain function. Full article

This study presents a low-cost, small-scale single-chamber microbial fuel cell (MFC) toxicity biosensor fabricated on a printed circuit board (PCB) and a 3D-printed chamber with a volume of 120 μL. The anode consists of a screen-printed carbon electrode on the PCB, while the air cathode is a carbon paper electrode. To address poor adhesion of microorganisms to the smooth anode surface, femtosecond laser processing was used to fabricate a micropore array with 40 μm pores on the electrode. This method can create micropores on the anode surface without damaging the screen-printed electrodes, the PCB substrate, or the pads. These micropores increase the anode’s surface area and hydrophilicity, allowing more microbial coatings to firmly adhere to its surface. In this study, the MFC utilised Rhizobium rosettiformans W3, extracted from activated sludge at a wastewater treatment plant, as the anode microorganism. Its aerobic nature simplifies the design of MFCs, enabling a single-chamber structure and miniaturisation. Using formaldehyde solution as a toxicity sample to test the biosensor’s performance, a 0.1% concentration significantly reduced the sensor’s output power. Full article

This study presents the development of a low-cost H₂ gas sensor made from a titanium dioxide–zinc oxide composite by means of a simple, cost-effective screen-printing method. The sensing material was created by mixing titanium dioxide and zinc oxide nanoparticles with an organic binder, which was screen-printed onto a glass substrate containing silver electrodes. These samples were then characterized using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The XRD results confirmed that the films boasted well-defined crystallinity, with predominant anatase and hexagonal ZnO phases, as well as uniformity of grains. Sensor performance was evaluated in a custom-built chamber at hydrogen concentrations of 100 to 1000 ppm and at operating temperatures of 100 °C, 200 °C, and 300 °C. The results indicate improved sensor performance as the operating temperature increased to 300 °C, with the best sensitivity values of 0.99, 1.17, and 1.31 at hydrogen concentrations of 100, 500, and 1000 ppm, respectively. The sensor showed stable and reproducible response characteristics, and its responses were retimed after a few hundred seconds. Low-cost fabrication, ease of processing, and reliable sensor performance make titanium oxide–zinc oxide composites promising candidates for hydrogen detection. Full article

Using disposable screen-printed electrodes faces major challenges when attempting to monitor a continuous process, especially in systems where there is pronounced adsorption, fouling, degradation, or in cases of irreversible electrochemical reactions. Methylene Blue (MB) exhibits some therapeutic properties and is commonly used as a redox reporter in DNA sensors, but is also considered a toxic pollutant in aquatic systems. MB demonstrates strong adsorption to carbon materials, which prevents its electroanalytical determination in multiple measurements with a single electrode. Our work details direct electrochemical determination of MB with only the native carbon screen-printed working electrode as sensing material and optimization of the analytical method. In batch mode, we significantly improved sensitivity and interelectrode reproducibility by introducing a prepolarization step, but successive measurements in lower concentrations were not feasible due to strong adsorption. A fully customizable, modular flow cell was 3D printed to allow in operando replacement of the planar screen-printed three-electrode system after measurement during continuous flow. As confirmed by mechanical properties testing, the rigid polyacrylate upper section of the flow cell provides structural stability, combined with a flexible TPU lower section which enables effortless sensor hot swapping and effective sealing during flow. With an optimized hot swapping flow detection method, MB was detected via square wave voltammetry with a sensitivity of 65.59 µA/µM and a calculated LOD of 7.75 nM, which outperforms similar systems from the literature. We envisage this approach can be integrated into low-cost continuous environmental monitoring systems or in-line quality control, especially in flow chemistry synthesis. Full article

This study presents a straightforward process for producing a hybrid ternary composite of silver nanoparticles (Ag NPs), small graphene oxide (s-GO), and zirconia (ZrO₂) and its use as an electrode material for electrochemical sensing. The physico-chemical properties of the ternary composite were analyzed by means of field emission scanning electron microscopy (FE-SEM), ultraviolet-visible (UV-vis) and FTIR spectroscopy, X-ray Photoelectron Spectrometry (XPS) and contact angle (CA) measurements. The synthesized hybrid nanomaterial was employed as an electrode modifier in the fabrication of a modified screen-printed carbon electrode (SPCE) and used for the simultaneous electrochemical sensing of key environmental pollutants such as hydroquinone (HQ) and catechol (CAT). The developed sensor exhibited linearity in the range of 0–100 µM for both HQ and CAT, with sensitivity values of 2640 µA·mM⁻¹·cm⁻² for HQ and 5120 µA·mM⁻¹·cm⁻² for CAT. The limits of detection (LOD) were 1.5 µM for HQ and 0.72 µM for CAT, respectively. The synergistic enhancement of electron transfer kinetics, the increased electroactive surface area, the strong anti-interference capability, and excellent reproducibility and stability establish these modified electrodes as promising candidates for environmental monitoring and real sample analysis. Full article

Ciprofloxacin (CIP) is an antibiotic that is widely used in humans and animals. However, the compound has been detected in animal-derived products and the environment due to its extensive use, causing serious concern for public health and environmental safety. The issue raises the urgent need to develop innovative techniques to monitor CIP. Therefore, this study aims to develop a simple and sensitive CIP sensor called the boron-doped diamond nanoparticle-modified screen-printed electrode (BDD NPs/SPE) and the nickel oxide nanoparticle-modified BDD NPs/SPE (NiO NPs/BDD NPs/SPE). NiO NPs were synthesized via green synthesis using Spatholobus littoralis Hassk. root extract as the reducing agent. The formation and characteristics of NiO NPs were then confirmed through a UV-Vis spectrophotometer, XRD, PSA, FT-IR, and XPS. The successful modification of SPE was confirmed through SEM-EDX, followed by measurements using square-wave voltammetry. The results showed that the modified SPE could detect CIP over a concentration range of 0.1–100 µM and produced a low detection limit of 0.109 µM for BDD NPs/SPE and 0.054 µM for NiO NPs/BDD NPs/SPE. The proposed method was successfully applied to the determination of CIP in commercial tablets, milk, and human urine, with a satisfactory % recovery from 95 to 100%. The current study successfully developed a simple yet highly sensitive sensor that enabled robust, reliable, and efficient detection of CIP, showing its strong potential for practical applications. Full article

Continuous plantar-pressure monitoring is important for objective gait analysis and early detection of abnormal loading; however, many existing solutions remain laboratory-bound (force plates and instrumented walkways) or rely on costly in-shoe multilayer sensor arrays. Here, we developed and optimized a fully screen-printed pressure-sensing insole based on carbon–polymer nanocomposite layers, with an emphasis on manufacturability and process control to bridge the gap between proof-of-concept force-sensitive resistor (FSR)-based insoles and scalable printed-electronics manufacturing workflows. Composite pastes containing carbon fillers (graphene nanoplatelets, carbon black, and graphite) were formulated to improve sensor repeatability and sensitivity. Sensors were characterized under compression loads from 100 N to 1300 N, showing a sensitivity of 10.5 ± 2.8 Ω per 100 N and a sheet-to-sheet coefficient of variation of 22.1% in resistance response. The effects of paste composition, screen mesh density, electrode layout, and lamination on sensitivity and repeatability were systematically evaluated. In addition, correlation analysis of resistance values from integrated quality-control meanders proved useful for monitoring screen-printing process stability. The final insole integrates printed carbon sensing pads and contacts, a dielectric spacer, and an adhesive layer in a thin, flexible format suitable for integration with wearable electronics. In practical static-load tests, repeated manual placement of weights yielded coefficients of variation as low as 4% at 500 g and a detection limit of ~0.1 N, comparable to a very light finger touch. These results demonstrate that low-cost screen-printed electronics can provide robust pressure sensing for wearable plantar-pressure monitoring. Full article

Benzisothiazolinone (BIT) is a commonly used biocide in water-based products, which can enter the environment from household and personal care products, as well as from leaching off building facades and roofs due to rainfall, eventually reaching rivers through stormwater runoff and raising ecological concerns due to its high aquatic toxicity. Detecting benzisothiazolinone, particularly in the environment is crucial due to health and regulatory requirements. This study explores electrochemical techniques and conductive nanomaterials for detecting BIT in environmental samples. Carbon- and gold-based screen-printed electrodes (SPEs) with distinct morphologies were investigated: carbon electrodes as nanoparticles (SPE-C) and single-wall carbon nanotubes (SPE-SWCNTs), and gold electrodes as nanoparticles (SPE-Au-BT) and thin films (SPE-Au-AT). Cyclic voltammetry and square-wave voltammetry (SWV) were optimized, with SWV demonstrating superior sensitivity—showing a two-order improvement with carbon-based electrodes and a 30-fold enhancement with gold-based electrodes. The lowest detection limits were 40 nM for carbon and 80 nM for gold nanoparticle-based electrodes. SPE-C achieved good recovery in river water, confirming its effectiveness for BIT monitoring with minimal interference from common ions or saccharin. These sensors can be easily used for everyday detection and monitoring of BIT in river water, ensuring a screening programme that supports the development of adequate regulatory guidelines. Full article

We report a highly sensitive and interference-free electrochemical sensor for dopamine (DA) detection in the presence of uric acid (UA) and ascorbic acid (AA), based on an in situ deposited graphitic carbon nitride (g-C₃N₄) and polymethyl thymol blue (PMTB) nanohybrid modified screen-printed carbon electrode (SPCE). The as-fabricated g-C₃N₄/PMTB/SPCE was thoroughly characterized using various physicochemical techniques. The electrochemical behavior of the modified electrode was systematically investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The g-C₃N₄/PMTB/SPCE exhibited excellent electrocatalytic activity toward the selective oxidation of DA under optimized experimental conditions, including pH and scan rate. Interference-free detection of DA in the presence of AA and UA was achieved using DPV and chronoamperometric methods, revealing a wide linear concentration range, an ultralow limit of detection, and high sensitivity. Furthermore, the practical applicability of the proposed sensor was validated by determining DA in artificial biofluid samples, including blood serum, and urine. The recovery results obtained good agreement with those obtained using high-performance liquid chromatography (HPLC), confirming the reliability and accuracy of the developed sensing platform. Full article

Enzyme-free flexible glucose sensors hold great promise in the field of wearable health monitoring. However, their performance is limited by the balance between the catalytic interface activity and stability. This paper reports a strategy for interface gradient roughening of screen-printed carbon electrodes (SPCE) via controllable electrochemical exfoliation (EE). It systematically reveals the inherent relationships among the degree of EE treatment, electrode morphology, surface chemistry, and electrochemical performance. On this basis, the deposition of gold nanoparticles (AuNPs) with high density and uniform distribution is achieved, and a high-performance flexible enzyme-free glucose sensor is constructed. The study finds that EE treatment can significantly increase the true surface area of the electrode and introduce abundant oxygen-containing functional groups, thus effectively reducing the charge transfer resistance. Nevertheless, excessive exfoliation leads to the degradation of the conductive network, indicating the existence of a critical “performance window”. The EE-SPCE optimized with 150 cycles has both a high active area and good electrical conductivity, providing an ideal deposition substrate for AuNPs, increasing their distribution density by approximately 158% and reducing the average particle size to 125 nm. The fabricated AuNPs/EE-SPCE sensor exhibits excellent performance in glucose detection: it has a high sensitivity of 550.766 μA·mM⁻¹·cm⁻² in the range of 0.1–3 mM, a detection limit of 0.0998 mM, a wide linear range, excellent selectivity, long-term stability, and good mechanical flexibility. This research not only develops an efficient and scalable method for constructing flexible sensing interfaces but also clarifies the trade-off relationship among “roughening–conductivity–catalytic performance” at the mechanistic level, providing an important theoretical basis and a general strategy for rationally designing high-performance flexible electrochemical devices. Full article

Two approaches are described for construction of a screen-printed planar electrode (SPE) for potentiometric determination of iodide ion. The first, involves preparation and application of iron(II) bathophenanthroline tetraiodoplumbate complex ([Fe(bphen)₃][PbI₄]), as a sensitive and selective electroactive sensing material in a potentiometric electrode for iodide determination. The second is the use of a nano-sized poly(aniline-co-thiophene) (PANI-co-PT) as a solid-contact material in a planar miniaturized configuration. The SPE displays a Nernstian response for iodide ion with a calibration slope of −58.81 ± 0.69 mV/decade (R² = 0.9998) over a wide concentration range (9.17 × 10⁻⁷–6.94 × 10⁻³ mol/L), low detection limit (6.09 × 10⁻⁷ mol/L), rapid response time (5.0 ± 1.0 s) and long-life span (75 ± 3.0 d). The use of PANI-co-PT solid-contact layer significantly improves the ion-to-electron transduction, eliminates the formation of undesired thin water layer between the sensing membrane and the conducting substrate, prevents membrane delamination, enhances potential stability with a significantly reduced potential drift (8.32 ± 0.12 µV/min) and displays high redox capacitance (2.560 ± 0.040 mF). Water contact angle measurements confirm the increased hydrophobicity of the modified membrane electrode (from 44 ± 0.8° to 93 ± 1.4°) and demonstrate the membrane ability to repel moisture and further stabilize the sensor response. The proposed sensor is successfully integrated into a flow injection analysis (FIA) system to enable real-time and continuous iodide monitoring with high precision, high sample throughput and applicability for quality control of pharmaceuticals and environmental monitoring. Full article