A new electrochemical sensor for highly sensitive and selective detection of nitrite in food samples based on sonochemical synthesized Calcium Ferrite (CaFe2O4) clusters modified screen printed carbon electrode

An ultra-sensitive electrochemical sensing platform based on nanoflower-like Au/ZnO array on carbon cloth for the rapid detection of the nitrite residues in food samples

In this work, we constructed an enhanced electrochemical signal sensing platform using Au/ZnO nanoflake arrays coated on carbon cloth for the rapid detection of nitrite in food. Based on a stepwise synthesis strategy of electrodeposition and magnetron sputtering technique, AuNPs were sputtered onto ZnO nanoflower-like array sheets. Combining the high catalytic performance of AuNPs with the morphology of ZnO significantly increased the surface area and electrocatalytic activity of the electrodes. The prepared sensor showed a linear response range of 0.2-4986 μΜ, a limit of detection of 0.09 μM, and a high sensitivity of 5677 μA mM-1 cm-2. It is worth noting that the sensor can precisely detect nitrite in the presence of interfering substances and has excellent stability and reproducibility. In addition, the nitrite residues in several food samples were analyzed using this method and spectrophotometric method, and the results of the two methods were not significantly different.

Photocatalytic removal of 2-chlorophenol from water by using waste eggshell-derived calcium ferrite

A new approach to recycling low-value eggshell food waste was to produce a CaFe₂O₄ semiconductor with a narrow band gap (E_g = 2.81 eV) via hydrothermal treatments of powdered eggshell suspended in aqueous ferric salt (Fe³⁺) solutions at varying Fe loadings. It was possible to obtain a single phase of CaFe₂O₄ without any Ca(OH)₂ and CaO impurities using an optimal Fe loading (30 wt% of Fe³⁺ by eggshell weight). The CaFe₂O₄ material was used as a photocatalyst for the breakdown of 2-chlorophenol (2-CP, a herbicide model chemical) as a pollutant in water. The CaFe₂O₄ with a Fe loading of 7.1 wt% exhibited a high 2-CP removal efficiency of 86.1% after 180 min of UV-visible light irradiation. Additionally, the eggshell-derived CaFe₂O₄ photocatalyst can be effectively reused, giving a high removal efficiency of 70.5% after the third cycle, without the requirement of regeneration processes (washing or re-calcination). Although radical trapping experiments confirmed that hydroxyl radicals were generated in the photocatalytic reactions, photogenerated holes play a significant role in the high 2-CP degradation efficiencies. The performance of the bioderived CaFe₂O₄ photocatalysts in the removal of pesticides from water demonstrated the benefits of resource recycling in the area of materials science and in environmental remediation and protection.

Preparation and Optical Properties of PVDF-CaFe2O4 Polymer Nanocomposite Films

In this work, a synthesis technique for highly homogeneous PVDF-CaFe₂O₄ polymer films direct from solution was developed. The structural characterizations were conducted using XRD, FTIR, and ESEM experimental techniques. The XRD characteristic peaks of CaFe₂O₄ nanoparticles revealed a polycrystalline structure. The average crystallite size for CaFe₂O₄ was calculated to be 17.0 nm. ESEM micrographs of PVDF nanocomposites containing 0.0, 0.25, 0.75, and 1.0 wt% of CaFe₂O₄ showed smooth surface topography. The direct E_dir and indirect E_ind band gap energies for the PVDF-CaFe₂O₄ nanocomposites were decreased with the additions of 0.0-1.0 wt% CaFe₂O₄. In addition, the refractive index (n₀) increased from 3.38 to 10.36, and energy gaps (E_g) decreased from 5.50 to 4.95 eV. The nonlinear refractive index (n₂) for the PVDF-CaFe₂O₄ nanocomposites was improved with the addition of CaFe₂O₄ nanoparticles, exceeding those reported in the literature for PVC, PVA, and PMMA nanocomposites. Therefore, the PVDF-CaFe₂O₄ nanocomposites are expected to take the lead in optoelectronic applications because of their unusual optical properties.

Revisiting the mechanisms of nitrite ions and ammonia removal from aqueous solutions: photolysis versus photocatalysis

Nitrite ions and ammonia are widespread forms of inorganic water pollutants. Nevertheless, the mechanisms of their photolytic and photocatalytic reactions under UV-A irradiation are still fully undisclosed, particularly, at different pH values under aerobic and inert atmospheres. Herein, we have studied the photolytic decomposition of nitrite ions under different conditions using 365 nm UV-A LED as a light source instead of mercury lamps that emit photons in the UV-B region and generate a lot of heat. The results indicated that the rate of nitrite disproportionation in the dark at pH ≤ 3.0 is remarkably high relative to the rate of the photolytic decomposition. At pH ˃ 3, the photolytic reaction is negligible and nitrite ions showed considerable stability. In contrast, the photocatalytic oxidation of nitrite ions over TiO₂ photocatalysts, namely, TiO₂P25, TiO₂UV100, and TiO₂ anatase/brookite mixture proceeds at pH ˃ 3.0. TiO₂ P25 exhibited the highest photocatalytic activity at pH 5. Interestingly, the photolytic simultaneous removal of nitrite ions and ammonia was possible at pH 9.0 in the absence of oxygen (Ar atmosphere). A 42.69 ± 0.66%, 27.75 ± 1.7%, and 32.74 ± 0.59% of nitrogen calculated based on nitrite, ammonia, and both of them, respectively, can be removed after 6 h of UV-A irradiation. The selectivity of N₂ evolution was 77.6%. The nitrogen removal rate was significantly reduced in the presence of TiO₂ photocatalyst evincing that TiO₂ photocatalysis is applicable for nitrite ions oxidation, whereas the photolytic process is better suited for the simultaneous removal of nitrite ions and ammonia.

Hydrothermal synthesis of CuFe2O4 nanoparticles for highly sensitive electrochemical detection of sunset yellow

The sunset yellow, as a synthetic food coloring azo dye, was detected in the present work using a new sensitive and selective sensor based on the modification of screen-printed electrode surface with Copper ferrite nanoparticles (CuFe₂O₄/SPE). Thus, a facile hydrothermal protocol was performed to prepare the CuFe₂O₄ nanoparticles, followed by characterization applying valid techniques, including Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and field-emission scanning electron microscopy (FE-SEM). Chronoamperometry, differential pulse voltammetry (DPV) and cyclic voltammetry (CV) were employed to determine the electrochemical behavior of as-fabricated sensor. According to the electrochemical findings, a greater anodic peak current was found for the sunset yellow oxidation on the CuFe₂O₄/SPE than that on the unmodified SPE. The electrocatalytic response for the sunset yellow oxidation on the CuFe₂O₄/SPE in phosphate buffer (0.1 M, pH = 7.0) was effective, with an excellent sensitivity (0.1919 μA μM^-1). There was a linear relationship between the voltammetric current and different sunset yellow concentrations (0.03-100.0 μM). The calculated limit of detection (LOD = 3Sb/m) for the sunset yellow was 0.009 μM.

Nickel -doped iron oxide nanoparticle-conjugated porphyrin interface (porphyrin/Fe2O3@Ni) for the non-enzymatic detection of dopamine from lacrimal fluid

Herein, we synthesized nickel (Ni)-doped iron oxide nanoparticles (Fe₂O₃). The presence of the dopant afforded anchoring sites for the porphyrinic hetero cavity of 5,10,15,20-(tetra-4-carboxyphenyl)porphyrin to produce the porphyrin/Fe₂O₃@Ni composite. The crystalline structure and morphology of porphyrin/Fe₂O₃@Ni were assessed using various tools including Fourier transform spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and Raman spectroscopy. Porphyrin/Fe₂O₃@Ni has proven to be an excellent dopamine (DA) probe material with good selectivity, reproducibility, stability and reliability owing to its clever morphology, which induces numerous active sites along with good active surface area. It consequently provides good accessibility to DA and allows for the smooth tunneling of electrons between the analyte and sensing interface. Meanwhile, the porphyrin molecules provide good carbon-based resilient support, inhibit the leaching of the electrode matrix and enhance electron shuttling, resulting in the robust oxidation of DA with amplified transduction signals. The designed porphyrin/Fe₂O₃@Ni interface showed a low detection limit (1.2 nm) with good sensitivity (1.2 nM) in the linear bounds of 10 μM to 3500 μM. Additionally, the interface was employed successfully to analyze DA from lacrimal fluid with good percentage recoveries (99.8% to 100.1%). We anticipate that such a design will simplify the in vitro screening of DA in rarely studied tear samples with sensitivity and selectivity.

Pd-Cu nanospheres supported on Mo2C for the electrochemical sensing of nitrites

The improper disposal in agricultural and industrial wastewater leads to high NO₂^- concentrations in the aquatic environment, which can cause cancer in humans and animals; thus, their quick and accurate detection is urgently needed to ensure public health and environmental safety. In this study, a reliable and selective electrochemical sensor consisting of Pd-Cu nanospheres (NSs) supported on molybdenum carbide was prepared via simple ultrasonication. Then, a glassy carbon electrode was realized using this composite (Pd-Cu-Mo₂C-modified GCE) to test its electrocatalytic sensing for NO₂^- in a 0.1 M phosphate-buffered solution (PBS) solution via cyclic voltammetry and amperometry; at a low oxidation potential, the anodic peak current of NO₂^- detected by this electrode was significantly higher than that of its unmodified and other modified electrodes. The sensor showed a broad linear response in the 5-165-nM NO₂^- concentration range, with a low detection limit (0.35 nM in 0.1 M PBS) and high sensitivity (3.308 μAnM^-1 cm^-2). Moreover, the fabricated electrode was successfully applied for detecting nitrites in sausages, river water, and milk, showing also good recovery.

New application for TiO2 P25 photocatalyst: A case study of photoelectrochemical sensing of nitrite ions

Developing photoelectrochemical (PEC) sensors based on photocatalytic materials has recently attracted great interest as an emerging technology for environmental monitoring. TiO₂ P25 is a well-known highly active photocatalyst, cheap, and produced commercially on a large scale. In the current work, a practical and durable TiO₂-based PEC sensor has been fabricated by immobilizing TiO₂ P25 nanoparticles at disposable screen-printed carbon substrates using drop-casting method. The fabricated PEC sensor has been applied for the anodic-detection and determination of nitrite (NO₂^-) ions under UV(A) light (LED, 365 nm) using chronoamperometry (CA) and differential pulse voltammetry (DPV). Linear calibration curves were obtained between the photocurrent responses and the concentrations of NO₂^- ions in the ranges of 0.1-5.0 and 0.5-10 mg L^-1 for CA and DPV, respectively. Surprisingly, the detection limits (sensitivities) of the fabricated sensor towards NO₂^- ions under light were enhanced by a factor of 4.75 (4.1) and 8.3 (37.4) for CA and DPV, respectively, in comparsion with those measured in the dark. It is found that the photo-excitation of TiO₂ facilitates the photooxidation of NO₂^- ions via the photo-generated holes whereas the photogenerated electrons contribute to the enhanced photocurrent and consequently the enhanced detection limit and sensitivity. The fabricated TiO₂-based PEC sensor exhibits a good stability, durability, and satisfying selectivity for NO₂^- ions determination. These results indicate that the TiO₂-based PEC sensor fabricated by utilizing cheap and commercially available components has great potential for being transferred from lab-to-factory.

Biosensing platform on ferrite magnetic nanoparticles: Synthesis, functionalization, mechanism and applications

Ferrite magnetic nanoparticles (FMNPs) are gaining popularity to design biosensors for high-performance clinical diagnosis. The fusion of information shows that FMNPs based biosensors require well-tuned FMNPs as detection probes to produce large and specific biological signals with minimal non-specific binding. Nevertheless, there is a noticeable lacuna of information to solve the issues related to suitable synthesis route, particle size reduction, functionalization, sensitivity towards targeted intercellular biological tiny particles, and lower signal-to-noise ratio. Therefore it allows exploring unique characteristics of FMNPs to design a suitable sensing device for intracellular measurements and diseases detection. This review focuses on the extensively used synthesis routes, their advantages and limitations, crystalline structure, functionalization, along with recent applications of FMNPs in biosensors, taking into consideration their analytical figures of merit and range of linearity. This work also addresses the current progress, key factors for sensitivity, selectivity and productivity improvement along with the challenges, future trends and perspectives of FMNPs based biosensors.

Highly Sensitive and Interference-Free Electrochemical Nitrite Detection in a 3D Printed Miniaturized Device

3D printing has a significant impact on various applications as it facilitates greater control over the designed shapes, leads to rapid prototyping and mass production with transferable designs at a lower cost. These attributes provide great versatility and thus make the devices industry-friendly. Herein, we demonstrate a simple and disposable 3D printed device, fabricated in single-step, as an electrochemical nitrite sensor using commercially available carbon loaded polylactic acid (PLA) filament. Nitrite, usually ingested through water and food, can be harmful when taken in excess. Thus, its efficient and accurate on-site detection becomes imperative. The device showed appreciable sensitivity and good selectivity towards nitrite having a limit-of-detection (LOD) of [Formula: see text]. Furthermore, the device has been shown to monitor nitrite in real soil and water samples with appreciable recovery values. Eventually, the device is capable to be multiplexed with varying soil parameters.

Magnetic nanomaterials based electrochemical (bio)sensors for food analysis

It is widely accepted that nanotechnology attracted more interest because of various values that nanomaterial applications offers in different fields. Recently, researchers have proposed nanomaterials based electrochemical sensors and biosensors as one of the potent alternatives or supplementary analytical tools to the conventional detection procedures that consumes a lot of time. Among different nanomaterials, researchers largely considered magnetic nanomaterials (MNMs) for developing and fabricating the electrochemical (bio)sensors for numerous utilizations. Among several factors, healthier and higher quality foods are the most important preferences of consumers and manufacturers. For this reason, developing new techniques for rapid, precise as well as sensitive determination of components or contaminants of foods is very important. Therefore, developing the new electrochemical (bio)sensors in food analysis is one of the key and effervescent research fields. In this review, firstly, we presented the properties and synthesis strategies of MNMs. Then, we summarized some of the recently developed MNMs-based electrochemical (bio)sensors for food analysis including detecting the antioxidants, synthetic food colorants, pesticides, heavy metal ions, antibiotics and other analytes (bisphenol A, nitrite and aflatoxins) from 2010 to 2020. Finally, the present review described advantages, challenges as well as future directions in this field.

Recent developments in voltammetric and amperometric sensors for cysteine detection

This review article aims to provide an overview of the recent advances in the voltammetric and amperometric sensing of cysteine (Cys). The introduction summarizes the important role of Cys as an essential amino acid, techniques for its sensing, and the utilization of electrochemical methods and chemically modified electrodes for its determination. The main section covers voltammetric and amperometric sensing of Cys based on glassy carbon electrodes, screen printed electrodes, and carbon paste electrodes, modified with various electrocatalytic materials. The conclusion section discusses the current challenges of Cys determination and the future perspectives.

Highly efficient degradation of metronidazole drug using CaFe2O4/PNA nanohybrids as metal-organic catalysts under microwave irradiation

Catalytic degradation based on microwave irradiation is an emerging technique which promises prompt and efficient catalytic degradation of organic pollutants. Calcium ferrite (CaFe₂O₄), poly(1-napththylamine) (PNA), and PNA/CaFe₂O₄ nanohybrids were synthesized via microwave-assisted technique. The properties of the as-prepared CaFe₂O₄, PNA, and PNA/CaFe₂O₄ nanohybrids were characterized by the thermogravimetric analysis (TGA), FTIR, XRD, SEM, and ultraviolet-visible spectrophotometry (UV-vis) analyses. The formation of inorganic-organic hybrids was confirmed by the FTIR and XRD studies. Loading of PNA was confirmed to be 8%, 16%, 32%, and 40% in CaFe₂O₄ which was established by TGA studies and the thermal stability was found to follow the order: CaFe₂O₄ > 8-PNA/CaFe₂O₄ > 16-PNA/CaFe₂O₄ > 32-PNA/CaFe₂O₄ > 40-PNA/CaFe₂O₄ > PNA. CaFe₂O₄ and PNA revealed band gap values of 3.42 eV and 2.60 eV respectively while for the PNA/CaFe₂O₄ nanohybrids, the values were found to be ranging between 2.46 and 3.00 eV. The PNA modified CaFe₂O₄ nanohybrids showed higher degradation efficiency towards metronidazole (MTZ) drug as compared with PNA and pure CaFe₂O₄. MTZ drug showed around 94% degradation within 21 min of microwave irradiation using 40-PNA/CaFe₂O₄ as catalyst. The enhanced catalytic activity was attributed to the high surface area of the nanohybrid catalyst as well as improved microwave catalytic activity of PNA. The reactive species responsible for degradation were confirmed by scavenger studies which formation of ^·OH and O₂^·- radicals. Recyclability tests showed that the 40-PNA/CaFe₂O₄ nanohybrid exhibited 86% degradation of MTZ (90 mg/l) even after the third cycle, which reflected higher reusability of the catalyst. The MTZ fragments were identified using liquid chromatography-mass spectrometry (LC-MS).

Film Carbon Veil-Based Electrode Modified with Triton X-100 for Nitrite Determination

A film carbon veil-based electrode (FCVE) modified with non-ionic surfactant Triton X-100 (TrX100) has been developed for nitrite determination. A new simple and producible technique of hot lamination (heat sealing) has been used for the FCVE manufacturing. The paper presents the findings of investigating the FCVE and the TrX100/FCVE by using voltammetry, chronoamperometry, and scanning electron microscopy. Modification of the electrode with TrX100 improves the hydrophilic property of its surface, which results in a larger electrode active area and higher sensitivity. Optimal conditions for nitrite determination with the use of the TrX100/FCVE have been identified. The linear range (LR) and the limit of detection (LOD) are 0.1–100 μM and 0.01 μM, respectively. The relative standard deviation (RSD) does not exceed 2.3%. High selectivity of the sensor ensures its successful application for the analysis of real samples (sausage products and natural water). The obtained results accord well with the results of the standard spectrophotometric method.

Impact of sonochemical synthesis condition on the structural and physical properties of MnFe2O4 spinel ferrite nanoparticles

Herein, we report sonochemical synthesis of MnFe₂O₄ spinel ferrite nanoparticles using UZ SONOPULS HD 2070 Ultrasonic homogenizer (frequency: 20 kHz and power: 70 W). The sonication time and percentage amplitude of ultrasonic power input cause appreciable changes in the structural, cation distribution and physical properties of MnFe₂O₄ nanoparticles. The average crystallite size of synthesized MnFe₂O₄ nanoparticles was increased with increase of sonication time and percentage amplitude of ultrasonic power input. The occupational formula by X-ray photoelectron spectroscopy for prepared spinel ferrite nanoparticles was (Mn_0.29Fe_0.42)[Mn_0.71Fe_1.58]O₄ and (Mn_0.28Fe_0.54) [Mn_0.72Fe_1.46]O₄ at sonication time 20 min and 80 min, respectively. The value of the saturation magnetization was increased from 1.9 emu/g to 52.5 emu/g with increase of sonication time 20 min to 80 min at constant 50% amplitude of ultrasonic power input, whereas, it was increased from 30.2 emu/g to 59.4 emu/g with increase of the percentage amplitude of ultrasonic power input at constant sonication time 60 min. The highest value of dielectric constant (ε') was 499 at 1 kHz for nanoparticles at sonication time 20 min, whereas, ac conductivity was 368 × 10^-9 S/cm at 1 kHz for spinel ferrite nanoparticles at sonication time 20 min. The demonstrated controllable physical characteristics over sonication time and percentage amplitude of ultrasonic power input are a key step to design spinel ferrite material of desired properties for specific application. The investigation of microwave operating frequency suggest that these prepared spinel ferrite nanoparticles are potential candidate for fabrication of devices at high frequency applications.

Hierarchical construction and characterization of lanthanum molybdate nanospheres as an unassailable electrode material for electrocatalytic sensing of the antibiotic drug nitrofurantoin

In this work, lanthanum molybdate nanospheres (LMNSs) were prepared by employing a co-precipitation methodology, and their electrochemical activity against nitrofurantoin (NF) was reported.

Simple synthesis of CoSn(OH)6 nanocubes for the rapid electrochemical determination of rutin in the presence of quercetin and acetaminophen

Schematic presentation of the synthesis of CoSn(OH)₆ nanocubes modified with SPCE towards the electrochemical detection of rutin.

Fluorometric determination of nitrite through its catalytic effect on the oxidation of iodide and subsequent etching of gold nanoclusters by free iodine

A method for sensitive detection of nitrite is presented. It is found that the red fluorescence of gold nanoclusters (with excitation/emission maxima at 365/635 nm) is quenched by traces of iodine via etching. Free iodide is formed by oxidation of iodide by bromate anion under the catalytic effect of nitrite. This catalytic process provides a sensitive means for nitrite detection. Under the optimal conditions, fluorescence linearly dropos in the 10 nM to 0.8 μM nitrite concentration range. The limit of detection is 1.1 nM. This is a few orders of magnitude lower than the maximum concentration allowed by authorities. Graphical abstract Schematic representation of a method for detection of nitrite via a redox reaction. Iodine was produced in the reaction and subsequently quenched the fluorescence from gold nanoclusters by etching their metallic cores, and a sensitive assay for nitrite down to 1.1 nM was developed.

Ultrasonic energy-assisted preparation of β-cyclodextrin-carbon nanofiber composite: Application for electrochemical sensing of nitrofurantoin

A simple ultrasonic energy assisted synthesis of β-cyclodextrin (β-CD) supported carbon nanofiber composite (CNF) and its potential application in electrochemical sensing of antibiotic nitrofurantoin (NFT) is reported. The elemental composition and surface morphology of the β-CD/CNF composite was validated through Field emission scanning electron microscopy, energy dispersive X-ray microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The uniform enfolding of hydrophilic β-CD over CNF enhance the aqueous dispersion and offer abundant active surface to the β-CD/CNF composite. Further, the electrocatalytic efficacy of the β-CD/CNF composite is utilized to fabricate an electrochemical sensor for the high sensitive quantitative detection of NFT. Under optimized analytical conditions, the sensor displays a broad working range of 0.004-308 µM and calculated detection limit of 1.8 nM, respectively. In addition, the sensor showcased a good selectivity, storage, and working stability, with amiable reproducibility. The point-of-care applicability of the sensor was demonstrated with NFT spiked human blood serum and urine sample with reliable analytical performance. The simple, cost-effective NFT sensor based on β-CD/CNF offered outstanding analytical performance in real-world samples with higher reliability.

A Facile Electrochemical Sensor Labeled by Ferrocenoyl Cysteine Conjugate for the Detection of Nitrite in Pickle Juice

Simple and facile electrochemical sensors for nitrite detection were fabricated by directly depositing ferrocenoyl cysteine conjugates Fc[CO-Cys(Trt)-OMe]₂ [Fc(Cys)₂] or Fc[CO-Glu-Cys-Gly-OH] [Fc-ECG] on screen-printed electrodes (SPEs). The modified carbon electrodes were characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Results indicated that Fc-ECG/SPE sensor showed enhanced current response and a lower overpotential than Fc(Cys)₂/SPE sensor for nitrite detection. Optimal operating conditions were estimated for nitrite detection by DPV. The concentration of nitrite showed a good linear relationship with the current response in the range of 1.0–50 μmol·L⁻¹ and with 0.3 μmol·L⁻¹ as the concentration for limit of detection. There were no interferences from most common ions. The development of this electrochemical sensor was used for nitrite detection in pickled juice with a R.S.D. lower than 2.1% and average recovery lower than 101.5%, which indicated that disposable electrochemical sensor system can be applied for rapid and precise nitrite detection in foods.

Facile, low-temperature synthesis of tungsten carbide (WC) flakes for the sensitive and selective electrocatalytic detection of dopamine in biological samples

Transition metal carbides have shown potential for use in electrochemical applications due to their excellent electronic conductivity, stability and electrocatalysis.

Sonochemical synthesis of molybdenum oxide (MoO3) microspheres anchored graphitic carbon nitride (g-C3N4) ultrathin sheets for enhanced electrochemical sensing of Furazolidone

Present strategy introduce the sonochemical synthesis of molybdenum oxide (MoO₃) microspheres anchored graphitic carbon nitride (g-C₃N₄) ultrathin sheets as a novel electrocatalyst for the detection of Furazolidone (FU). TEM results revealed that MoO₃ are microspheres with an average size of 2 µM and the g-C₃N₄ seems like ultrathin sheets. Owing to their peculiar morphological structure, g-C₃N₄/MoO₃ composite modified electrode provided an enriched electroactive surface area (0.3788 cm²) and higher heterogeneous electron transfer kinetics (K°_eff = 4.91×10^-2 cm s^-1) than the other controlled electrodes. It is obviously observed from the voltammetric studies that the proposed sensor based on g-C₃N₄/MoO₃ composite can significantly improve the electrocatalytic efficiency towards the sensing of FU. Due to the excellent synergic effect of g-C₃N₄/MoO₃ composite, can detect the ultra-level FU with a limit of detection of 1.4 nM and a broad dynamic range of 0.01-228 µM, which surpassed the many previously reported FU sensors. Hence, the proposed sensor was successfully applied to sensing the FU in human blood serum, urine and pharmaceutical samples, gained an agreeable recoveries.