μA mM-1 Cm-2 Research Articles

Flexible Non-Enzymatic Glucose Sensors: One-Step Green Synthesis of NiO Nanoporous Films via an Electro-Exploding Wire Technique.

In this study, we successfully synthesized nickel oxide (NiO) nanoparticles (NPs), i.e., samples NiO 24V, NiO 36V, and NiO 48V, via an environmentally friendly one-step electro-exploding wire technique by employing three distinct voltage levels of 24, 36, and 48 V, respectively. Sample NiO 48V showed the most rugged surface and smallest particle size, which helped to enhance electrocatalytic properties. The highest Ni3+ content of sample NiO 48V contributed to the increasing redox current and rendering highly enhanced chemical reactions and thereby improving their electrochemical properties and electrocatalytic performance in the glucose oxidation processes in alkaline (0.1 M NaOH, pH = 13) media. The NiO 48V electrode showcased an excellent linear detection range spanning from 0.1 to 1 mM, featuring a remarkable sensitivity of 1202 μA mM-1 cm-2 and an exceptionally low limit of detection (LOD) value of 0.25 μM. Remarkably, NiO NPs exhibited exceptional long-term stability, commendable reproducibility, favorable repeatability, and outstanding selectivity. This study also highlights the excellent operational performance of the NiO 48V electrode in real-world samples, such as commercially available beverages and human urine, highlighting the practical nature of these nonenzymatic sensors in real-life scenarios for the food industries, clinical diagnostics, and biotechnology applications.

Electrochemical behavior and L-tyrosine sensing properties of nanostructured Cr, Sn and La-doped α-Fe2O3 interfaces

L-tyrosine (Tyr) is a promising biomarker for the diagnosis and monitoring of metabolic disorders and neurodegenerative diseases. This study reports on the electrochemical properties of α-Fe2O3 nanostructures doped with Cr, Sn and La, referred to as CrFeOx, SnFeOx and LaFeOx, respectively, and their application in the enzyme-free electrochemical Tyr sensors. These disposable sensors offer accurate Tyr concentration analysis at room temperature, addressing the limitations of current point-of-care diagnostic methods. The CrFeOx, SnFeOx, and LaFeOx nanostructures serve as selective agents for binding and recognizing Tyr, deposited onto disposable graphite pencil electrodes to form the electrochemical interface. The interfacial resistance, charge-transfer kinetics, mechanism, and reversibility are studied via extensive electrochemical measurements employing electro¬chemical impedance spectroscopy and cyclic voltammetry. Furthermore, differen¬tial pulse voltammetry demonstrates excellent Tyr sensing performance in the concen¬tration range of 0 to 80 μM with 2.65 µA µM-1 cm-2 sensitivity and 360 nM thres¬hold detection limit for the best-performing CrFeOx sensors. Hence, these α-Fe2O3-based sensor systems are practical and efficient for selective Tyr detection, offering potential advancements in personalized healthcare and early disease diagnosis.

A Wearable Electrochemical Sensor Based on Single-Atom Pt Anchored on Activated NiCo-LDH/Ti3C2Tx for Real-Time Monitoring of Glucose.

Wearable, noninvasive sweat sensors enable real-time monitoring of metabolites in human health management. However, the commercial enzyme-based and currently nonenzymatic glucose sensor represents sluggish glucose oxidation kinetics and a narrow sensing range. Rational design of sensitive materials is significant yet faces a huge challenge. Herein, we construct a single-atom Pt supported on NiCo-LDH/Ti3C2Tx heterostructures (Pt1-NiCo-LDH/Ti3C2Tx) as the nonenzymatic electrochemical glucose sensor sensitive materials for selective detection of glucose level in human sweat. The obtained Pt1-NiCo-LDH/Ti3C2Tx with improved structural stability and enhanced charge transfer efficiency shows a low oxidation peak potential of 0.49 V, high sensitivity of 506.6 μA mM-1 cm-2, a low detection limit of 0.035 μM, and long-term stability toward the glucose detection. The wearable sensor, coupled with a wireless transmission module and a signal processing chip, is used for real-time perspiration glucose monitoring during outdoor exercise. The result is comparable to that of high-performance liquid chromatography (HPLC). This research provides a new paradigm for designing a wearable nonenzymatic electrochemical glucose sensor, enabling noninvasive real-time monitoring of glucose concentrations in human sweat.

In-situ Electrochemical Synthesis of Ni/Ni(OH)2/Molecularly Imprinted Polymer Nanocomposite for High-Performance Glucose Detection

This study presents a novel non-enzymatic glucose sensor that synergistically combines the high catalytic activity of nickel hydroxide (Ni(OH)2) with the selective recognition of molecularly imprinted polymers (MIPs). The sensors were fabricated through an entirely in-situ synthesis directly on the electrode, comprising electrodeposition and oxidation of Ni/Ni(OH)2 nanoparticles and electropolymerization of a glucose-imprinted MIP layer using pyrrole and 3-aminophenyl boronic acid. The integrated MIP layer significantly enhanced selectivity against common interferents while amplifying glucose sensitivity. The resulting sensor demonstrated a high sensitivity of 1802 μA mM-1 cm-2 with a linear range from 0.04 to 2.6mM. Notably, the sensor exhibited remarkable stability, retaining 97.2% of its original sensitivity after 6 months of room-temperature storage. To extend the linear range, Nafion coatings at two concentrations were applied, achieving ranges up to 0.04 – 11.6mM with adjusted sensitivities. This innovative approach, leveraging MIPs to provide selectivity to electrocatalytic nanomaterials, offers a promising strategy for developing high-performance non-enzymatic sensors for glucose and other biomolecules in diabetes monitoring and beyond.

Fluid-Specific Detection of Environmental Pollutant Moxifloxacin Hydrochloride Utilizing a Rare-Earth Niobate Decorated Functionalized Carbon Nanofiber Sensor Platform

The development of precise and efficient detection methods is essential for the real-time monitoring of antibiotics, especially in environmental and biological matrices. This study aims to address this challenge by introducing a novel electrochemical sensor for the targeted detection of moxifloxacin hydrochloride (MFN), a fourth-generation fluoroquinolone. The sensor is based on a holmium niobate (HNO) and functionalized carbon nanofiber (f-CNF) nanocomposite, synthesized via a hydrothermal approach and subsequently characterized for its structural and electrochemical properties. When deposited onto a glassy carbon electrode (GCE), the HNO/f-CNF nanocomposite demonstrated exceptional electrochemical performance, as assessed using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The sensor exhibited remarkable sensitivity, with a detection limit of 0.034 μM, a quantification limit of 0.11 μM, and a sensitivity of 0.69 μA μM-1 cm-2. It also achieved a broad linear detection range from 0.001 μM to 1166.11 μM, making it highly effective for MFN detection across various complex matrices, including environmental waters, biological fluids, and artificial saliva, with recovery rates between 98.15% and 101.75%. The novelty of this work lies in the unique combination of HNO's catalytic properties and f-CNF's enhanced electron transport, establishing a highly selective and sensitive platform for MFN detection. This sensor not only advances the field of electrochemical sensing but also offers a promising tool for real-time environmental and pharmaceutical monitoring.

A Comparative Study on the Electrocatalytic Efficiency of Coupled (CuO-Co3O4) vs. Mixed (CuCo2O4) Metal Oxides: Probed by Hydrazine Oxidation and Sensitive Determination

This work reports the synthesis of copper- and cobalt-based coupled and mixed metal oxides (CuO-Co3O4 and CuCo2O4, respectively) utilizing a simple hydrothermal and calcination approach. CuO-Co3O4, CuCo2O4, and the control samples were characterized by powder X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray, and X-ray photoelectron spectroscopy. TEM and FE-SEM analyses of CuO-Co3O4 reveal the presence of two distinct morphologies: rod- and sphere-shaped particles (CuO and Co3O4, respectively). Further, CuO-Co3O4 was efficiently utilized as an electrocatalyst for the selective oxidation of hydrazine (Hyz). CuO-Co3O4 shows a high redox response compared to CuO, Co3O4, CuCo2O4, and the physical mixture of CuO and Co3O4 (CuO/Co3O4). This enhanced performance is attributed to the synergistic interaction between the metal ions caused by their close proximity and the increased exposure of surface active sites. CuO-Co3O4 shows a broad linear range (1-3500 µM), a low detection limit (0.29 µM), and high sensitivity (0.5756 µA µM-1 cm-2) for the Hyz determination. Kinetic parameters, for instance the diffusion coefficient and catalytic rate constant for Hyz oxidation were obtained using chronoamperometry. Additionally, CuO-Co3O4 was effectively utilized to analyze Hyz in real samples with acceptable recovery rates.

Nanobioengineered Al2O3 Core-Shell Nanoparticle Preparation Using Bauhinia Variegate Plant Extract for Efficient Photocatalysis and Electrochemical Sensing.

Core-shell-based nanomaterials have garnered considerable attention in the recent past not only in catalytic applications but also in their potentiality in selective and efficient sensing. Present research reports the first and successful biosynthesis of the core (c-Al2O3)-shell nanoparticles (NPs) using Bauhinia variegate blossom extract as reducing and capping agents. The synthesized c-Al2O3 NPs were characterized and utilized to fabricate nanobioengineered electrodes on indium tin oxide (ITO) substrates via electrophoretic deposition. Electrochemical analysis, including cyclic voltammetry and differential pulse voltammetry, revealed quasi-reversible processes with high electron-transfer rates (Ks = 0.66 s-1) and a diffusion coefficient (D = 5.84 × 10-2 cm2 s-1). The electrode exhibited a very high sensitivity (23.44 μA μM-1 cm-2) and a low detection limit (0.463 μM) for sodium azide (NaN3) over two linear ranges of 1-6 and 8-20 μM. Additionally, c-Al2O3 NPs demonstrated the effective photocatalytic degradation of crystal violet dye under visible light, following pseudo-first-order kinetics. The fabricated electrode showed excellent selectivity, stability, and reproducibility, highlighting its potential for environmental monitoring and clinical diagnostics.

Ruthenium(II) N-heterocyclic carbene polymer based sensors for detection of predatory drugs like ketamine and scopolamine.

The current demand in the field of abusive drug research is to have a highly sensitive and rapid method for detecting ketamine and scopolamine, which are frequently used in drug-facilitated sexual assaults administered via beverages and food. We report here the first electrochemical sensors of N-heterocyclic carbene (NHC) coordinated ruthenium organometallic 1-dimensional polymers and their multi-walled carbon nano tube (MWCNT)-based composite for detecting ketamine and scopolamine. The preparation of ruthenium NHC organometallics and the MWCNT composite as sensors offers significant advantages for electrochemical applications, with enhanced sensitivities of 121.979 and 3.273 μA μM-1 cm-2 for ketamine and scopolamine, respectively, and selectivity in sensing applications. The complex-carbon composite sensor has a low limit of detection i.e., 0.194 and 3.18 nM for ketamine and scopolamine identification, respectively. Alongside, the selectivity of the composite sensor was evaluated in the presence of other blood constituents, and the study evidenced remarkable discernment towards the title drugs. Furthermore, real-time analyses using the composite sensor demonstrated quantitative identification of ketamine and scopolamine. Therefore, this innovation has the potential to provide valuable tools for forensic investigations and address the urgent need for real-time detection of date rape drugs. This contribution demonstrates a robust proof-of-concept that emphasizes the importance of creating non-enzymatic, environmentally friendly, and cost-effective sensors for on-site sensing applications as point-of-care devices.

A Machine Learning Assisted Non-Enzymatic Electrochemical Biosensor to Detect Urea Based on Multi-Walled Carbon Nanotube Functionalized with Copper Oxide Micro-Flowers.

Detecting urea is crucial for diagnosing related health conditions and ensuring timely medical intervention. The addition of machine learning (ML) technologies has completely changed the field of biochemical sensing, providing enhanced accuracy and reliability. In the present work, an ML-assisted screen-printed, flexible, electrochemical, non-enzymatic biosensor was proposed to quantify urea concentrations. For the detection of urea, the biosensor was modified with a multi-walled carbon nanotube-zinc oxide (MWCNT-ZnO) nanocomposite functionalized with copper oxide (CuO) micro-flowers (MFs). Further, the CuO-MFs were synthesized using a standard sol-gel approach, and the obtained particles were subjected to various characterization techniques, including X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Fourier transform infrared (FTIR) spectroscopy. The sensor's performance for urea detection was evaluated by assessing the dependence of peak currents on analyte concentration using cyclic voltammetry (CV) at different scan rates of 50, 75, and 100 mV/s. The designed non-enzymatic biosensor showed an acceptable linear range of operation of 0.5-8 mM, and the limit of detection (LoD) observed was 78.479 nM, which is well aligned with the urea concentration found in human blood and exhibits a good sensitivity of 117.98 mA mM-1 cm-2. Additionally, different regression-based ML models were applied to determine CV parameters to predict urea concentrations experimentally. ML significantly improves the accuracy and reliability of screen-printed biosensors, enabling accurate predictions of urea levels. Finally, the combination of ML and biosensor design emphasizes not only the high sensitivity and accuracy of the sensor but also its potential for complex non-enzymatic urea detection applications. Future advancements in accurate biochemical sensing technologies are made possible by this strong and dependable methodology.

Fast preparing bioelectrode with conductive bioink for nitrite detection in high sensitivity and stability

Electrochemically active biofilms (EABs) for nitrite detection have high specificity, rapid response, operational simplicity, and extended lifespan advantages. However, their scale production remains challenging due to time-consuming and uniform preparation. In this study, a novel approach was proposed to fast fabricate an EAB biosensor with a synthetic biofilm electrode for nitrite detection. The biofilm electrode was prepared by coating bioinks with varying conductive materials onto the surface of the graphite sheets, showing short incubation time and good reproducibility. Incorporating conductive materials into the bioinks remarkably enhanced the maximum voltage of the first cycle of bioelectrode incubation, with an increase of up to 633% for carbon nanofibers. The nitrite reduction current was amplified by a factor of 2.97, due to the enhancement of extracellular electron transfer (EET). The developed nitrite biosensor exhibited a detection range of 0.1–15 mg NO2--N L−1, with a high sensitivity of 610.8 μA mM−1 cm−2, and a stabilization operation time of at least 280 cycles. This study not only provided valuable insights into conductive materials for synthetic biofilms but also presented a practical approach for the rapid preparation, scale production, and optimization of highly sensitive and stable EAB sensors.

Highly Specific Non-Enzymatic Electrochemical Sensor for the Detection of Uric Acid Using Carboxylated Multiwalled Carbon Nanotubes Intertwined with GdS-Gd2O3 Nanoplates in Human Urine and Serum.

Herein, the electrochemical sensing efficacy of carboxylic acid functionalized multiwalled carbon nanotubes (C-MWCNT) intertwined with coexisting phases of gadolinium monosulfide (GdS) and gadolinium oxide (Gd2O3) nanosheets is explored for the first time. The nanocomposite demonstrated splendid specificity for nonenzymatic electrochemical detection of uric acid (UA) in biological samples. It was synthesized using the coprecipitation method and thoroughly characterized. The presence of functional groups and disorder in the as-synthesized nanocomposite are confirmed using Fourier transform infrared spectroscopy and Raman spectroscopy. Furthermore, field emission scanning electron microscopy, high-resolution transmission electron microscope, X-ray powder diffraction, and X-ray photoelectron spectroscopy provides a clear understanding of the morphology, coexisting phases, and elemental composition of the as-synthesized nanocomposites. The differential pulse voltammetry technique was utilized to elaborate the electrochemical sensing of UA using a GdS-Gd2O3/C-MWCNT modified glassy carbon electrode (GCE), The sensor showed an enhanced current response by more than 2-fold compared to bare GCE. Also, the sensor's performance was further improved by dispersing the nanocomposite in an ionic liquid with the exceptional reproducibility (SD = 0.0025, n = 3). The fabricated UA sensor GdS-Gd2O3/C-MWCNT/IL/GCE demonstrated a wide linear detection range from 0.5-30 μM and 30-2000 μM, effectively covering the entire physiological range of UA in biological fluids with a limit of detection (LOD) of 0.380 μM (+3SD of blank) and a sensitivity of 356.125 μA mM-1 cm-2. Moreover, the electrodes exhibited storage stability for 2 weeks with decrease in zero-day current by only 4.5%. The sensor was validated by quantifying UA in 12 unprocessed clinical human urine and serum samples, and its comparison with the gold standard test yielded remarkable results (p < 0.05). Hence, the proposed nonenzymatic electrochemical UA sensor is selective, sensitive, reproducible, and stable, making it reliable for point-of-care diagnostics.

Electrochemical Detection of H2O2 Using Bi2O3/Bi2O2Se Nanocomposites.

The development of high-performance hydrogen peroxide (H2O2) sensors is critical for various applications, including environmental monitoring, industrial processes, and biomedical diagnostics. This study explores the development of efficient and selective H2O2 sensors based on bismuth oxide/bismuth oxyselenide (Bi2O3/Bi2O2Se) nanocomposites. The Bi2O3/Bi2O2Se nanocomposites were synthesized using a simple solution-processing method at room temperature, resulting in a unique heterostructure with remarkable electrochemical characteristics for H2O2 detection. Characterization techniques, including powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), confirmed the successful formation of the nanocomposites and their structural integrity. The synthesis time was varied to obtain the composites with different Se contents. The end goal was to obtain phase pure Bi2O2Se. Electrochemical measurements revealed that the Bi2O3/Bi2O2Se composite formed under optimal synthesis conditions displayed high sensitivity (75.7 µA µM-1 cm-2) and excellent selectivity towards H2O2 detection, along with a wide linear detection range (0-15 µM). The superior performance is attributed to the synergistic effect between Bi2O3 and Bi2O2Se, enhancing electron transfer and creating more active sites for H2O2 oxidation. These findings suggest that Bi2O3/Bi2O2Se nanocomposites hold great potential as advanced H2O2 sensors for practical applications.

Reusable gallium-based electrochemical sensor for efficient glucose detection

Among wearable sensing devices, electrochemical sensors are overwhelming in biochemical detection due to their simple design but high sensitivity. Most electrochemical sensors are disposable, which significantly impairs the service life. Here we present a reusable gallium (Ga)-based multi-layer electrochemical glucose biosensor to extend noninvasive monitoring of glucose in the interstitial fluid. This multilayer sensor includes Ga as a conductive interconnector, poly(3,4-ethylenedioxythiophene) as an electrode layer to prevent oxidation and metal leakage, a nano-Pt layer to enhance the electrochemical properties, and a nano-Prussian blue layer for reducing the hydrogen peroxide reduction potential. Most importantly, the biosensors can be renewed by automatically removing the modified nanocomposites via the electrolysis-induced bubbles and by electroplating without impairing the whole structure of the biosensor. The biosensor showed high sensitivity (24.6 μA mM-1 cm-2), wide linear range (0.01-26 mM), excellent stability (i.e., pH, long-term use) and superior selectivity, that is comparable to those of the current electrochemical tools for glucose detection. More importantly, incorporated with the reverse iontophoresis (RI), the Ga-based hybrid sensor was applied as a skin patch on mice for the in vivo noninvasive and continuous monitoring of ISF-borne glucose. The results showed a good correlation with that measured by blood glucometer. As a whole, this Ga-based electrochemical biosensor should endow new functions like biochemical analysis in biofluids for Ga-based soft bioelectronic sensing devices, in which almost are physical sensors. We believe that the reusability of electrochemically controllable processes may further inspire the development of more integrated and long-term stable gallium-based biosensing devices.

Brewer's Spent Grain-Cellulose-Coated Copper Electrode-Based Extended Gate Field-Effect Transistor for Nonenzymatic Glucose Detection toward Diagnosis of Diabetes Mellitus.

The demand for environmentally friendly, reliable, and cost-effective electrodes for glucose sensor technology has become a major research area in the paradigm shift toward green electronics. In this regard, cellulose has emerged as a promising flexible biopolymer solution with unique properties such as biocompatibility, biodegradability, nontoxicity, renewability, and sustainability. Because of their large surface area and porous structure, fibrous cellulose substrates quickly adsorb and disperse analytes at detection sites. This work focuses on utilizing glyoxal-treated cellulose (derived from brewer's spent grain (BSG)) for the fabrication of extended gate field-effect transistor (EGFET)-based glucose sensors. This investigation extends to the utilization of BSG-cellulose for glucose detection in biomimicking electrolytes (phosphate buffer saline) to facilitate glucose detection in human blood samples. The fabricated electrode demonstrates a linear range of glucose detection from 1 to 13.5 mM with a Langmuir adsorption coefficient (K) of 0.102. Also, its selectivity toward glucose over interfering molecules such as sucrose, fructose, ascorbic acid, and uric acid under physiological conditions has been demonstrated. This cellulose-based EGFET electrode exhibits a sensitivity of 6.5 μA mM-1 cm-2 with a limit of detection (LOD) of 0.135 mM. Computational studies by density functional theory calculations confirmed the higher binding affinity of glucose molecules with glyoxal-modified cellulose (-0.95 eV) than with pristine cellulose (-0.46 eV). Here, the novelty lies in the fabrication of electrodes with biodegradable catalysts and their integration into the EGFET configuration.

Ultrasensitive electrochemical detection of metronidazole using binder-free zinc-4,4'-oxybis(benzoic acid) MOF/GCE in real samples.

A novel electrochemical sensor is constructed by modifying the glassy carbon electrode (GCE) using a binder-free metal-organic framework of V-shaped linker 4,4'oxybis(benzoic acid) (OBA) and various transition metals (M-Zn, Mn, or Ni). The hydrothermally synthesized M-OBA MOFs demonstrated superior electron transfer ability and enhanced electro-reduction behaviour, making it highly effective for metronidazole (MTZ) detection. The optimized sensor demonstrated a linear response from 0.04 to 122.18 µM, a low detection limit (LOD) of 0.009 µM, and high sensitivity (0.48 µA µM-1 cm-2) using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The sensor also exhibited excellent selectivity in the presence of various ions, organic compounds, and other antibiotics. The Zn-OBA MOF sensor proves practical applicability for detecting MTZ in milk, honey, tap water, and MTZ tablets.

Schottky Interface Enabled Electrospun Rhodium Oxide Doped Gold for Both pH Sensing and Glucose Measurements in Neutral Buffer and Human Serum.

This study has focused on adjusting sensing environment from basic to neutral pH and improve sensing performance by doping electrodeposited gold (Au) with metal oxide for nonenzymatic glucose measurements in forming a Schottky interface for superior glucose sensing with detailed analysis for the sensing mechanism. The prepared sensor also holds the ability to measure pH with the identical electrospun metal oxide-electrodeposited Au, which composed a dual sensor (glucose and pH sensor) through applying chronoamperometry and open circuit potential methods. The rhodium oxide nanocoral structure was fabricated with an electrospinning precursor solution, followed by a calcination process, and it was mixed with electrodeposited nanocoral gold to form the Schottky interface by constructing a p-n type heterogeneous junction for improved sensitivity in glucose detection. The prepared materials were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectrometry (XPS), etc. The prepared materials were used for both pH responsive testing and amperometric glucose measurements. The rhodium oxide nanocoral doped gold demonstrated a sensitivity of 3.52 μA mM-1 cm-2 and limit of detection of 20 μM with linear range up to 3 mM glucose concentration compared to solely electrodeposited gold for a sensitivity of 0.46 μA mM-1 cm-2 and a limit of detection of 450 μM. The Mott-Schottky method was used for the analysis of an electron transfer process from noble metal to metal oxide to electrolyte in demonstrating the improved sensitivity at neutral pH for glucose measurements due to the Schottky barrier adjustment mechanism at an applied flat band potential of 0.3 V. This work opens a new venue in illustrating the metal oxide/metal materials in the glucose neutral response mechanism. In the end, human serum samples were tested against current commercial glucose meter to certify the accuracy of the proposed sensor.

An Enzyme-Encapsulated MOF@MOF Nanocomposite for Detecting H2O2 Derived From Superoxide Anion Released by Mitochondria of HeLa Cells.

In this work, a horseradish peroxidase (HRP)-encapsulated metal organic framework (MOF)@MOF nanocomposite is developed for detecting H2O2 converted by dismutation of superoxide anions released from live HeLa mitochondria. Initially, an HRP-polyacrylic acid cluster is incorporated on a mesoporous, peroxidase-like Cu/Co-1,4-benzenedicarboxylate (BDC) MOF platform to avoid structural change and deactivation of HRP through its interactions with MOF metal ions. Additionally, a Cu/Co-BDC(HRP)@1,3,5-benzenetricarboxyate (BTC) core-shell MOF/MOF structure, also with peroxide-like properties, serves as a protective matrix for HRP. Then, ultrathin porous carbon shells (UPCS) are adopted to improve the electrical conductivity of the MOF@MOF. The Cu/Co-BDC(HRP)@BTC|UPCS sensing platform exhibits two linear ranges of 0.05-1 µM and 1-1000 µM with a sensitivity of 172mA mM-1 cm-2 and 1.63mA mM-1 cm-2, respectively. A limit of detection of 0.057 µM, good selectivity and stability over 35 days for H2O2 detection are also achieved. After treating the mitochondrial complex with specific inhibitors, amperometric results at the sensing platform confirmed complex I and III within mitochondria as the main electron leakage sites in the electron transfer chains. Therefore, this sensing platform provides a tool that may aid in predicting and even developing treatments for some oxidative stress diseases caused by mitochondrial abnormalities.

Microfibrous Carbon Paper Decorated with High-Density Manganese Dioxide Nanorods: An Electrochemical Nonenzymatic Platform of Glucose Sensing.

Nanorod structures exhibit a high surface-to-volume ratio, enhancing the accessibility of electrolyte ions to the electrode surface and providing an abundance of active sites for improved electrochemical sensing performance. In this study, tetragonal α-MnO2 with a large K+-embedded tunnel structure, directly grown on microfibrous carbon paper to form densely packed nanorod arrays, is investigated as an electrocatalytic material for non-enzymatic glucose sensing. The MnO2 nanorods electrode demonstrates outstanding catalytic activity for glucose oxidation, showcasing a high sensitivity of 143.82 µA cm-2 mM-1 within the linear range from 0.01 to 15 mM, with a limit of detection (LOD) of 0.282 mM specifically for glucose molecules. Importantly, the MnO2 nanorods electrode exhibits excellent selectivity towards glucose over ascorbic acid and uric acid, which is crucial for accurate glucose detection in complex samples. For comparison, a gold electrode shows a lower sensitivity of 52.48 µA cm-2 mM-1 within a linear range from 1 to 10 mM. These findings underscore the superior performance of the MnO2 nanorods electrode in both sensitivity and selectivity, offering significant potential for advancing electrochemical sensors and bioanalytical techniques for glucose monitoring in physiological and clinical settings.

Construction of Cu2Y2O5/g-C3N4 Novel Composite for the Sensitive and Selective Trace-Level Electrochemical Detection of Sulfamethazine in Food and Water Samples.

The most frequently used sulfonamide is sulfamethazine (SMZ) because it is often found in foods made from livestock, which is hazardous for individuals. Here, we have developed an easy, quick, selective, and sensitive analytical technique to efficiently detect SMZ. Recently, transition metal oxides have attracted many researchers for their excellent performance as a promising sensor for SMZ analysis because of their superior redox activity, electrocatalytic activity, electroactive sites, and electron transfer properties. Further, Cu-based oxides have a resilient electrical conductivity; however, to boost it to an extreme extent, a composite including two-dimensional (2D) graphitic carbon nitride (g-C3N4) nanosheets needs to be constructed and ready as a composite (denoted as g-C3N4/Cu2Y2O5). Moreover, several techniques, including X-ray diffraction analysis, scanning electron microscopy analysis, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy were employed to analyze the composites. The electrochemical measurements have revealed that the constructed g-C3N4/Cu2Y2O5 composites exhibit great electrochemical activity. Nevertheless, the sensor achieved outstanding repeatability and reproducibility alongside a low limit of detection (LOD) of 0.23 µM, a long linear range of 2 to 276 µM, and an electrode sensitivity of 8.86 µA µM-1 cm-2. Finally, the proposed GCE/g-C3N4/Cu2Y2O5 electrode proved highly effective for detection of SMZ in food samples, with acceptable recoveries. The GCE/g-C3N4/Cu2Y2O5 electrode has been successfully applied to SMZ detection in food and water samples.

Fabrication of Nanobioengineered Interfaces Utilizing Quaternary Nanocomposite for Highly Efficient and Selective Electrochemical Biosensing of Urea.

Nanobioengineered interfaces have gained attention owing to their small size and high surface area-to-volume ratio for utilization as a platform for highly selective and sensitive biosensing applications owing to the integration of biological molecules with engineered nanomaterials/nanocomposites. In this work, a novel Ag-complex, [(PPh3)2Ag(SCOf)]-based quaternary Ag-S-Zn-O nanocomposites (NCs), was synthesized through an environmentally-friendly process. The results revealed the formation of the NCs with an average crystallite size and particle size of 36.08 and 40.22 nm, respectively. In addition, this is the first study to utilize such NCs synthesized via a single-source precursor method, offering enhanced sensor performance due to their unique structural properties. Further, these NCs were used to fabricate a urease (Ur)/Ag-S-Zn-O NCs/ITO nanobioengineered electrode for precise and sensitive electrochemical biosensing of urea. The interfacial kinetic studies revealed quasi-reversible processes with high electron transfer rates and linear current responses, indicating efficient reaction dynamics. A high diffusion coefficient and low surface concentration suggested a fast diffusion-controlled process, affirming the electrode's potential for rapid and sensitive urea detection. The biosensor demonstrated notable sensing properties such as high sensitivity (12.56 μA mM-1 cm-2) and a low detection limit (0.54 mM). The fabricated bioelectrode was highly selective and reproducible and demonstrated stability for up to 60 days. These results validate the potential of this nanobioengineered interface for next-generation biosensing applications, paving the way for advanced point-of-care diagnostics and real-time health monitoring.