Silkworm Cocoon‐Templated Hierarchical Co 3 O 4 for Non‐Enzymatic Electrochemical Detection of H 2 O 2

In this work, a novel non-enzymatic hydrogen peroxide sensor, Ag@zeolitic imidazolate framework-67 (Ag@ZIF-67)/glassy carbon electrode (GCE), was fabricated by a simple method at room temperature. The morphology and structure of Ag@ZIF-67 were investigated by scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, Fourier transform infrared spectroscopy, powder X-ray diffraction, atomic absorption spectrophotometry, and N2 absorption isotherms, which indicated that core-shell Ag@ZIF-67 was successfully synthesized with a porous rhombic dodecahedron structure. Electrochemical investigations demonstrated that the Ag@ZIF-67/GCE had strong electrocatalytic activity towards hydrogen peroxide reduction with a low detection limit of 1.5 μM (S/N = 3), a fast response time of 3 s, and three different linear relationships in the ranges of 5.0 μM-275 μM, 775 μM-2775 μM, and 4775 μM-16 775 μM with sensitivities of 27 μA mM-1 cm-2, 13 μA mM-1 cm-2, and 5.3 μA mM-1 cm-2, respectively. Moreover, the fabricated sensor exhibited an excellent recovery rate in real sample analysis of medical hydrogen peroxide disinfectant. These results proved that Ag@ZIF-67/GCE is an effective electrochemical sensor for detecting hydrogen peroxide.

Generally, ascorbic acid (AA) is a potent reducing and antioxidant agent that regulates in fighting against bacterial infections as well as detoxifying reactions, which is functioned in the formation of collagen in fibrous tissue, teeth, bones, connective tissue, skin, and capillaries. Up to date, electrochemical enzymatic sensor are significantly used for enzymatic AA detection that exhibits an excellent selectivity, high reliability and handled under physiological conditions. However, considering some intrinsic dis-advantages of using enzymes, such as high fabrication cost and poor stability, non-enzymatic AA sensors have attracted increasing research interest in recent years owing to their low cost, high stability, fast response, and low detection limit. Moreover, the development of nanotechnology has also offered new opportunities to develop the nanostructured sensor probes for enzyme-less AA sensing applications. With beneficial advantages, ternary-doped metal oxides have gathered an extensive effort in the development of cost-effective sensors with high stability, sensitivity and quick response for the determination of selective AA by enzyme-free detection. In this approach, the mixed metal oxides of CdO/SnO2/V2O5 micro-sheets (MSs) were prepared by facile wet-chemical method in alkaline phase at low temperature. Later, it was subjected to detail characterize by using various methods such as XPS, FESEM, EDS, and XRD. The slurry of prepared MSs in ethanol was deposited initially onto the surface of glassy carbon electrode (GCE) to make a thin film with conducting nafion (5% suspension in ethanol) adhesive to result the working electrode of proposed AA sensor probe. The sensor sensitivity (21.3354 μA μM−1 cm−2) is calculated by using the slope (0.6742 μA μM−1) of the calibration curve by considering the active surface area of GCE (0.0316 cm2) in the linear dynamic range (LDR; 0.1 nM to 0.01 mM). The limit of detection (LOD) (98.64 ± 4.98 pM) is obtained from the calibration curve. The proposed AA electrochemical sensor exhibits short response time, good reproducibility and successive outcome during the investigation of the real biological samples. The development of enzyme-free AA sensor by using CdO/SnO2/V2O5 MSs onto GCE is simple as well as reliable and practically able to detect the biological stuffs for the safety of human health in the field of biomedical and sensor technology.

For improving the stability of the modified interface and response sensitivity, synergistic effect of a cationic surfactant of tetraoctylammonium bromide (TOAB), carboxylic acid functionalized multi-walled carbon nanotube (MWCNT) and Hemin was used to fabricate a novel non-enzyme electrochemical sensor. TOAB as an ion-pair reagent interacts with carboxyl groups on MWCNT and Hemin to reduce electrostatic repulsion and improve the π−π stacking interaction between MWCNT and Hemin, which were proved by UV-vis spectrophotometry and electrochemical technique. Moreover, TOAB matrix provided a hydrophobic surrounding required for reversible electrochemical redox of Hemin on a glassy carbon electrode (GCE) in aqueous solution. MWCNT further promoted the electron transfer between Hemin and electrode surface. Consequently, the proposed sensor based on TOAB/MWCNT@Hemin/GCE exhibited higher response sensitivity comparing with those of TOAB/Hemin/GCE and MWCNT@Hemin/GCE. Using hydrogen peroxide (H2O2) as a target analyte for evaluating the performance of the sensor, a high sensitivity of 1.37 μA μM−1 cm−2 and low limit of detection (LOD) of 0.26 μM were obtained on the TOAB/MWCNT@Hemin/GCE in a linear range from 0.82 to 278.6 μM. The rapid, simple, stable, and sensitive sensing platform supplies great promising applications in electrochemical analysis and paves a new avenue for constructing the non-enzyme electrochemical sensor.

Na,O-co-doped-graphitic-carbon nitride (Na,O-g-C3N4) for nonenzymatic electrochemical sensing of hydrogen peroxide

5-Amino-2-mercapto-1,3,4-thiadiazole coated nitrogen-doped-carbon sphere composite for the determination of phenolic compounds

Comparison of electrochemiluminescence and amperometric detection of lipid hydroperoxides

Hydrogen peroxide (H2O2) plays a significant role in biological and environmental systems. Therefore, it is crucial to develop an efficient biosensor for H2O2 determination, which is important in environmental monitoring and biomedical diagnostics. In this work, we have synthesized an amine functionalized, single-layered Ti3C2Tx MXene (NH2-S-Ti3C2Tx), which was modified over a glassy carbon electrode (GCE) to construct NH2-S-Ti3C2Tx/GCE. Thus obtained NH2-S-Ti3C2Tx/GCE was utilized as a platform for the covalent cross-linking of water-soluble horseradish peroxidase (HRP) enzyme through a glutaraldehyde coupling reaction to form HRP/NH2-S-Ti3C2Tx/GCE. The fabricated HRP/NH2-S-Ti3C2Tx/GCE biosensor demonstrated a well-defined redox peak with a formal potential of -0.45 V, corresponding to the FeIII/FeII redox center of HRP. Additionally, the designed biosensor has been employed towards the electrocatalytic detection of H2O2 under both static and dynamic conditions. The HRP/NH2-S-Ti3C2Tx/GCE sensor displayed a broad linear range of 20 µM to 1160 µM with a low limit of detection of 5.3 µM and a high sensitivity of 0.078 µA mM-1 cm-2. The reported sensor demonstrated excellent analytical performance due to direct electron transfer through the covalent immobilization of HRP over NH2-S-Ti3C2Tx. Furthermore, the sensor was employed for the real-time detection of H2O2, and it portrayed good recovery results.

• A SrMoO 4 /f-CNFs-based sensor was successfully fabricated for DPA detection. • The sensor showed a wide linear range with low detection limit and good selectivity. • The SrMoO 4 /f-CNFs/GCE exhibited good repeatability, reproducibility, and stability. • DFT calculations revealed energy levels and electron transfer sites of DPA. • Sensor applicability was validated in food and water samples with good recovery. Diphenylamine (DPA) is widely employed as an anti-scald agent for post-harvest fruit preservation. Despite its effectiveness, excessive DPA residues pose serious concerns due to their potential to contaminate water sources via agricultural runoff, leading to environmental pollution and health risks. Therefore, the development of reliable and sensitive methods for DPA detection is essential for ensuring food safety and environmental protection. In this study, an advanced electrochemical sensor was developed by modifying a glassy carbon electrode (GCE) with a nanocomposite consisting of strontium molybdate (SrMoO 4 ) and functionalized carbon nanofibers (f-CNFs). The synergistic interaction between SrMoO 4 and f-CNFs significantly enhanced the electrocatalytic activity and conductivity of the sensor. The fabrication strategy aimed to exploit these properties to achieve high sensitivity and selectivity in DPA detection. The fabricated SrMoO 4 /f-CNF-modified GCE sensor demonstrated excellent analytical performance, including high sensitivity (0.46 μA μM -1 cm -2 ), a low detection limit (2.09 nM), a wide linear range (0.005 to 1381.5 μM), and strong selectivity, stability, and reproducibility, with successful detection of DPA in spiked food and environmental samples yielding recovery rates of 94–99 %, confirming its suitability for real-time monitoring in food safety and environmental applications.

Fabrication, characterization and performance evaluation of an amplified electrochemical sensor based on MOFs nanocomposite for leukemia drug Imatinib determination

A colorimetric and ratiometric fluorescent probe for metabisulfite detection and its application in food safety analysis.

In-situ electrochemical deposition of cobalt hexacyanoferrate (CoHCF) on graphene oxide (GO) and its application for the electrocatalytic hydrazine determination in real samples are described in this research study. Co2+ is immobilized on GO and the resulting material, GO-Co2+ is coated on the surface of glassy carbon (GC) electrode. The fabricated electrode (GC/GO-Co2+) is subjected to a continuous potential cycling in the range of 0.0–1.0 V which results in the formation of a thin CoHCF film on the surface of GO coated on the GC electrode (abbreviated as GC/GO-CoHCF). The synthesized GO-CoHCF composite material is characterized by Fourier transform infrared and scanning electron microscopy. GC/GO-CoHCF electrode electrocatalytically oxidizes hydrazine at low overpotential (0.63 V) and this phenomenon is subsequently utilized for the sensitive determination of hydrazine in aqueous solutions. It exhibits a wide linear calibration range (0.1–400 µM), high sensitivity (0.93 µA µM−1 cm−2) and low limit of detection (17.5 nM) for the determination of hydrazine. Further, this electrode is employed for hydrazine determination in real samples.

The widespread use of nitrofurantoin (NFT), a nitrofuran-based antibiotic commonly prescribed for urinary tract infections (UTIs), has raised concerns due to its potential side effects, including neurological and gastrointestinal toxicity. Monitoring NFT levels in biological fluids such as urine is critical to ensuring patient safety and therapeutic efficacy. In this study, we developed a novel electrochemical sensor based on a nanocomposite of iron oxide (α-Fe₂O₃) and hexagonal boron nitride (h-BN) for the selective and sensitive detection of NFT in human urine samples.The α-Fe₂O₃/h-BN nanocomposite was synthesized via a hydrothermal method, with humic acid serving as a stabilizing agent. The morphology, structure, and composition of the composite were comprehensively characterized using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), elemental mapping (E-Map), X-ray diffraction (XRD), and UV–Visible spectroscopy. The FE-SEM analysis confirmed the formation of spherical α-Fe₂O₃ nanoparticles uniformly anchored on the hexagonal sheets of h-BN. XRD patterns validated the crystalline nature of both components, while UV–vis spectra and Tauc plots revealed a blue shift and bandgap widening in the composite due to quantum confinement effects and increased microstrain, confirming the successful integration of materials.For sensor fabrication, the α-Fe₂O₃/h-BN nanocomposite was drop-cast onto a pre-treated glassy carbon electrode (GCE). The modified GCE demonstrated enhanced electrochemical properties, as evaluated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and amperometry (AMP). The nanocomposite-coated electrode exhibited a significantly improved cathodic peak current and reduced overpotential (−0.49 V) for NFT reduction, indicating superior electrocatalytic activity compared to bare and h-BN-only modified GCEs. EIS analysis further confirmed the enhancement in charge transfer capabilities due to the presence of the nanocomposite.The electrochemical detection of NFT was carried out using amperometry, where the sensor showed two linear response ranges: from 0.025 to 0.45 µM and from 0.70 to 22.95 µM. The sensor achieved an outstanding detection limit of 15 nM and a rapid response time of 2 seconds, with a calculated sensitivity of 2.36 µA µM⁻¹ cm⁻². Scan rate studies revealed that the electrochemical reduction of NFT on the α-Fe₂O₃/h-BN/GCE was diffusion-controlled, as evidenced by the linear relationship between the square root of the scan rate and the peak current.To evaluate its real-world applicability, the sensor was tested for NFT detection in human urine samples using the standard addition method. The recovery rates ranged from 99.47% to 99.93%, and the relative standard deviation (RSD) values were all below 0.5%, confirming excellent accuracy and repeatability. Furthermore, interference studies involving common urine constituents (e.g., urea, uric acid, NaCl, oxalic acid) revealed minimal impact on NFT detection (<4% signal deviation), showcasing the sensor’s high selectivity.The stability and reproducibility of the sensor were also validated. After 50 consecutive CV cycles, the sensor retained approximately 70% of its initial response, indicating commendable operational stability. Repeatability tests conducted with five independently prepared sensors showed a relative standard deviation of 3.72%, reflecting strong fabrication consistency.The high-performance characteristics of this sensor—low detection limit, fast response, high selectivity, and successful detection in real samples—are attributed to the synergistic effect between α-Fe₂O₃ nanoparticles and h-BN nanosheets. The integration of these materials creates a porous and conductive interface that facilitates efficient electron transfer and increases surface area for NFT adsorption. Moreover, including humic acid during synthesis promotes the uniform anchoring of α-Fe₂O₃ on h-BN, enhancing the composite's overall stability and electrocatalytic activity.This work is among the first to employ α-Fe₂O₃/h-BN nanocomposites for the electrochemical detection of nitrofurantoin. The results demonstrate its potential as a robust, cost-effective, and non-invasive diagnostic tool for monitoring antibiotic levels in biological fluids. Beyond NFT detection, the synthesized nanocomposite is promising for broader biosensing, environmental monitoring, and point-of-care diagnostics applications. Keywords: Nitrofurantoin, Electrochemical Sensor, α-Fe₂O₃, Hexagonal Boron Nitride, Human Urine, Amperometry, Nanocomposite, Urinary Tract Infections Figure 1

The aim of the present study is to report an alternative technique of creating nickel oxide (NiO) nanofibers, manufactured by facile and economical electrospinning process. The crystallinity nature of NiO nanofibers is investigated by X‐ray diffraction (XRD). Nanofibers morphology is examined by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The diameter of the nanofibers is varying from of 100–150 nm. Furthermore, Selected Area Electron Diffraction (SAED) pattern revealed that NiO nanofibers are exhibiting a single phase crystalline structure. The NiO nanofibers modified glassy carbon electrode (GCE) showed an excellent performance towards the electrocatalytic oxidation of hydrogen peroxide (H 2 O 2 ). This sensor showed a wide range of detection from 10 μM to 50 mM, low limit of detection 0.33 μM and high sensitivity 42.09 μA μM −1 cm −2 for H 2 O 2 detection. The entire analysis reaffirms the suitability of NiO nanofibers as one of the futuristic sensing material for H 2 O 2 detection.

In this work, a signal amplification strategy was designed by the fabrication of a highly sensitive and selective electrochemical sensor based on nickel-copper-zinc ferrite (Ni0.4Cu0.2Zn0.4Fe2O4)/carboxymethyl cellulose (CMC)/graphene oxide nanosheets (GONs) composite modified glassy carbon electrode (GCE) for determination of omeprazole (OMP). The one-step synthesized Ni0.4Cu0.2Zn0.4Fe2O4/CMC/GONs nanocomposite was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy and X-ray diffraction techniques. Then, the Ni0.4Cu0.2Zn0.4Fe2O4/CMC/GONs/GCE was applied to study the electrochemical behavior of the OMP. Electrochemical data show that the Ni0.4Cu0.2Zn0.4Fe2O4/CMC/GONs/GCE exhibits superior electrocatalytic performance on the oxidation of OMP compared with bare GCE, GONs/GCE, CMC/GONs/GCE and MFe2O4/GCE (M = Cu, Ni and Zn including single, double and triple of metals) which can be attributed to the synergistic effects of the nanocomposite components, outstanding electrical properties of Ni0.4Cu0.2Zn0.4Fe2O4 and high conductivity of CMC/GONs as well as the further electron transport action of the nanocomposite. Under optimal conditions, the Ni0.4Cu0.2Zn0.4Fe2O4/CMC/GONs/GCE offers a high performance toward the electrodetermination of OMP with the wide linear-range responses (0.24-5 and 5-75 μM), lower detection limit (0.22 ± 0.05 μM), high sensitivity (1.1543 μA μM-1 cm-2), long-term signal stability and reproducibility (RSD = 2.54%). It should be noted that the Ni0.4Cu0.2Zn0.4Fe2O4/CMC/GONs/GCE sensor could also be used for determination of OMP in drug and biological samples, indicating its feasibility for real analysis.

Two-dimensional metal-organic framework (MOF) crystalline materials possess promising potential in the electrochemical sensing process owing to their tunable structures, high specific surface area, and abundant metal active sites; however, developing MOF-based nonenzymatic glucose (Glu) sensors which combine electrochemical activity and environmental stability remains a challenge. Herein, utilizing the tripodic nitrogen-bridged 1,3,5-tris(1-imidazolyl) benzene (TIB) linker, Co2+ and Ni2+, two 2D isomorphic crystalline materials, including Co/Ni-MOF {[Co (TIB)]·2BF4} (CTGU-31) and {[Ni(TIB)]·2NO3} (CTGU-32), with a binodal (3, 6)-connected kgd topological net were firstly synthesized and fabricated with conducting acetylene black (AB). When modified on a glassy carbon electrode, the optimized AB/CTGU-32 (1:1) electrocatalyst demonstrated a higher sensitivity of 2.198 μA μM-1 cm-2, a wider linear range from 10 to 4000 μM, and a lower detection limit (LOD) value (0.09 μM, S/N = 3) compared to previously MOF-based Glu sensors. Moreover, AB/CTGU-32 (1:1) exhibited desirable stability for at least 2000 s during the electrochemical process. The work indicates that MOF-based electrocatalysts are a promising candidate for monitoring Glu and demonstrate their potential for preliminary screening for diabetes.