Construction of a voltammetric sensor based on MIL-101 hollow cages for electrocatalytic oxidation and sensitive determination of nitrofurazone

Electrochemical detection of nitrofurazone using laser-engraved three-electrode graphene array

BACKGROUND

Nitrofurazone (NFZ) is a widely-used antimicrobial agent in aquaculture. The NFZ residue can be transmitted to humans through the food chain, and cause adverse health effects including carcinogenesis and teratogenesis. Until now, a number of modified electrodes have been developed for NFZ detection, however, there are some issues that need to be improved. For example, the reported detection sensitivity is relatively low, the modification procedure is complicated, and conventional three-electrode system is used. Therefore, it is quite important to develop new NFZ detection method with higher sensitivity, simplicity and practicality.

RESULTS

Herein, a kind of integrated three-electrode array consisted with porous graphene is easily prepared through laser engraving of commercial polyimide tape. Five kinds of graphene arrays were prepared at different laser power percentage (i.e. 30 %, 40 %, 50 %, 60 % and 70 %). It is found that their structure, morphology, fluffiness and porosity show great difference, consequently affecting the electrochemical performance of graphene arrays such as conductivity, active area and electron transfer ability. The engraved graphene array at 50 % laser power percentage (LIG-50 array) is superior owing to uniform 3D structure, abundant pores and high stability. More importantly, LIG-50 array is more active for NFZ oxidation, and significantly enhances the detection sensitivity. The linear range of LIG-50 sensor is from 0.2 to 8 μM, and the detection limit is 0.035 μM, which is successfully used in fish meat samples.

SIGNIFICANCE

A sensitive, portable and practical electrochemical sensor has been successfully developed for NFZ using laser-engraved graphene array. The demonstration using fish meat samples manifests this new sensor has good accuracy and great potential in application. This study could provide a new possibility for the design and fabrication of other high-performance electrochemical sensor for various applications in the future.

Disposable electrochemical sensor: Highly sensitive determination of nitrofurazone antibiotic in environmental samples and pharmaceutical formulations

The study presents the successful development of a new electrochemical sensor with low cost and disposability for application in nitrofurazone detection in environmental and pharmaceutical samples. The sensors were fabricated using materials obtained from local storage and conductive carbon ink. The modification of the screen-printed electrodes with the hybrid nanomaterial based on silver nanoparticles, carbon quantum dots, and carbon nanotubes showed synergistic contributions in the nitrofurazone electrooxidation, as observed in the wide linear range (0.008 at 15.051 μM), with a sensitivity of 0.650 μA/μM. The limit of detection obtained was 4.6 nM. Differential pulse voltammetry, cyclic voltammetry, X-ray photoelectron spectroscopy, X-ray diffraction analysis, and high-resolution transmission electron microscopy were used to evaluate the electrochemical and structural characteristics. Studies of possible interferences were considered with nitrofurazone in the presence of the ions and organic molecules. The results were satisfactory, with a variation of 93.3% ± 4.39% at 100% ± 2.40%. The low volume used in the analyses (50 μL), disposability, high sensibility, selectivity, and low limit of detection are advantages that make the proposed sensor an electrochemical tool of high viability for the NFZ detection in environmental matrices and pharmaceutical formulations.

Preparation of W-N-C single atom catalyst and Cu3(HHTP)2 metal-organic framework dual-decorated graphene nanoplatelet flexible electrode arrays for the rapid detection of carbendazim in vegetables

It is highly desirable to develop a low-cost and rapid detection method for trace levels of carbendazim fungicide residues, which would be beneficial for improving human health and mitigating environmental issues. Herein, isolated single tungsten atoms were implanted onto well-organized metal-organic framework (MOF)-derived N-doped carbons to form W-N-C single-site heterojunctions with ultrahigh electrocatalytic activity. The coupling of W-N-C with Cu3(HHTP)2, an electronically conductive MOF with a large surface area and porous structure, exhibited enhanced electrocatalytic performance for the oxidation of carbendazim (CBZ) when they were used for decorating graphene nanoplatelet flexible electrode arrays fabricated via template-assisted scalable filtration. A wide linear range (3.0 nM-50 μM) with an ultra-low detection limit of 0.97 nM and fast response was achieved for CBZ analysis. Moreover, the sensing platform has been utilised to monitor CBZ levels in vegetable samples with satisfactory recovery rates of 97.2-102% and a low relative standard deviation of 1.9%.

An efficient electrochemical sensor based on the Ce-MOF/g-C3N5 composite for the detection of nitrofurazone

The Ce-MOF/g-C3N5 composite was first constructed using a simple reflux method in an oil bath. Herein, we report that the electrochemical sensor fabricated based on this composite exhibits high performance in the detection of nitrofurazone. Interestingly, this sensor exhibits an extra-wide linear range of detection composed of two line segments (7-100 μM and 100-2913 μM), as well as a low detection limit (LOD) of 6.15 μM (S/N = 3) under optimal experimental conditions. Additionally, the sensor demonstrates exceptional selectivity, reproducibility and stability. More importantly, the proposed electrochemical sensor can effectively monitor nitrofurazone in real samples such as urea and tap water, and obtain ideal recoveries. The sensor has such excellent performance because of the synergistic effect of the two components in the Ce-MOF/g-C3N5 composite. Compared with Ce-MOF, the introduction of g-C3N5 effectively not only enhances the conductivity of Ce-MOF/g-C3N5 but also exposes more active sites, which is conducive to increasing the electrocatalytic activity to reduce nitrofurazone. This research contributes new scientific research ideas for fabricating ideal electrochemical sensors based on g-C3N5 and MOFs.

Hydrothermal synthesis of iron titanate hexagonal nanoplates for electrochemical detection of nitrofurazone

An electrochemical sensor is established using an iron titanate (FeTiO3) modified glassy carbon electrode (GCE) to detect nitrofurazone. Various microscopic and spectroscopic analysis was performed to reveal the properties of the prepared FeTiO3 hexagonal nanoplates. The FeTiO3/GCE presents enhanced electrochemical response to nitrofurazone at the peak reduction potential of - 0.471 V with a larger peak current than the bare GCE due to high electrical conductivity, enhanced specific surface area, and abundant active sites. The superior nitrofurazone detection performance includes the low limit of detection of 0.002 μM and the sensitivity of 0.551 µA µM-1 cm-2 in the linear concentration range of 0.01-162.2 μM. The reproducibility and selectivity studies of the FeTiO3/GCE show excellent results with a relative standard deviation of < 5%. The practicability of FeTiO3/GCE is confirmed by monitoring nitrofurazone in actual samples. This work demonstrates that perovskite-type FeTiO3 has great potential in real-world sample analysis, and provides a new way to develop high-performance electrochemical sensors.

A fluorescence nanoprobe of N-Acetyl-L-Cysteine capped CdTe QDs for sensitive detection of nitrofurazone

A method was established for detecting the content of nitrofurazone (NFZ) by fluorescence quenching of N-Acetyl-L-Cysteine (NAC) coated cadmium telluride quantum dots (CdTe QDs). By means of transmission electron microscopy (TEM) and multispectral methods such as fluorescence and ultraviolet visible spectra (UV-vis), the synthesized CdTe QDs were characterized. The quantum yield (φ) of CdTe QDs was measured as 0.33 by reference method. The CdTe QDs had a better stability, the RSD of fluorescence intensity was 1.51% in three months. NFZ quenching the emission light of CdTe QDs was observed. The analyses of Stern-Volmer and time-resolved fluorescence suggested the quenching was static. The binding constants (K_a) between NFZ and CdTe QDs were 1.14 × 10⁴ (293 K), 0.74 × 10⁴ (303 K) and 0.51 × 10⁴ (313 K) L mol^-1. The hydrogen bond or van der Waals force was the dominated binding force between NFZ and CdTe QDs. The interaction was further characterized by UV-vis absorption as well as Fourier transform infrared spectra (FT-IR). Using fluorescence quenching effect, a quantitative determination of NFZ was carried out. The optimal experimental conditions were studied and determined as following: pH was 7 and contact time was 10 min. The effects of reagent addition sequence, temperature and the foreign substances including some metals (Mg²⁺; Zn²⁺; Ca²⁺; K⁺; Cu²⁺), glucose, bovine serum albumin (BSA) and furazolidone on the determination were studied. There was a high correlation between the concentration of NFZ (0.40 - 39.63 μg mL^-1) and F₀/F with the standard curve F₀/F = 0.0262c + 0.9910 (r = 0.9994). The detection limit (LOD) reached 0.04 μg mL^-1 (3S₀/S). The contents of NFZ in beef and bacteriostatic liquid were detected. The recovery of NFZ was 95.13% - 103.03% and RSD was 0.66% - 1.37% (n = 5).

Beyond Pristine Metal-Organic Frameworks: Preparation of Hollow MOFs and Their Composites for Catalysis, Sensing, and Adsorption Removal Applications

Metal-organic frameworks (MOFs) have been broadly applied to numerous domains with a substantial surface area, tunable pore size, and multiple unsaturated metal sites. Recently, hollow MOFs have greatly attracted the scientific community due to their internal cavities and gradient pore structures. Hollow MOFs have a higher tunability, faster mass-transfer rates, and more accessible active sites when compared to traditional, solid MOFs. Hollow MOFs are also considered to be candidates for some functional material carriers. For example, composite materials such as hollow MOFs and metal nanoparticles, metal oxides, and enzymes have been prepared. These composite materials integrate the characteristics of hollow MOFs with functional materials and are broadly used in many aspects. This review describes the preparation strategies of hollow MOFs and their composites as well as their applications in organic catalysis, electrochemical sensing, and adsorption separation. Finally, we hope that this review provides meaningful knowledge about hollow-MOF composites and their derivatives and offers many valuable references to develop hollow-MOF-based applied materials.

Gadolinium molybdate decorated graphitic carbon nitride composite: highly visualized detection of nitrofurazone in water samples

In this work, a graphitic carbon nitride/gadolinium molybdate (g-C₃N₄/Gd₂MoO₆) composite manufactured glassy carbon electrode (GCE) was used to detect nitrofurazone (NFZ) at the trace level. A quick and inexpensive electrochemical sensor for NFZ analysis is described in this paper. The material structure and properties were determined by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and transmission electron microscopy. The GCE/g-C₃N₄/Gd₂MoO₆ electrode was studied using cyclic voltammetry and amperometry. The electrocatalytic studies of the GCE/g-C₃N₄/Gd₂MoO₆ electrode showed significantly improved detection of NFZ. The electrocatalytic studies of the GCE/g-C₃N₄/Gd₂MoO₆ electrode was significantly improved for the detection of NFZ than bare GCE, GCE/g-C₃N₄, and GCE/Gd₂MoO₆ modified electrodes. The linear response and the detection limit of NFZ were 0.006 μM (S/N = 3) and 0.02-2000 μM, respectively. The electrode sensitivity was identified as 2.057 μA μM^-1 cm^-2 under ideal experimental conditions. The modified electrode was able to detect NFZ even when there were 500-fold as many interfering ions present. The practical applicability of the electrode was tested in a variety of water samples, with satisfactory results. Overall, the NFZ sensor demonstrated satisfactory repeatability, stability, and reproducibility. Meanwhile, it has proven to be a reliable, stable, and practical platform for the analysis of NFZ in various water samples, with acceptable recoveries.

Advances of Drugs Electroanalysis Based on Direct Electrochemical Redox on Electrodes: A Review

The strong development of mankind is inseparable from the proper use of drugs, and the electroanalytical research of drugs occupies an important position in the field of analytical chemistry. This review mainly elaborates the research progress of drugs electroanalysis based on direct electrochemical redox on various electrodes for the recent decade from 2011 to 2021. At first, we summarize some frequently used electrochemical data processing and electrochemical mechanism research derivation methods in the literature. Then, according to the drug therapeutic and application/usage purposes, the research progress of drugs electrochemical analysis is classified and discussed, where we focus on drugs electrochemical reaction mechanism. At the same time, the comparisons of electrochemical sensing performance of the drugs on various electrodes from recent studies are listed, so that readers can more intuitively compare and understand the electroanalytical sensing performance of each modified electrode for each of the drug. Finally, this review discusses the shortcomings and prospects of the drugs electroanalysis based on direct electrochemical redox research.

Sensitive surface-enhanced Raman spectroscopy (SERS) determination of nitrofurazone by β-cyclodextrin-protected AuNPs/γ-Al2O3 nanoparticles

A novel surface-enhanced Raman spectroscopy (SERS) method for the determination of nitrofurazone was developed using AuNPs/γ-Al₂O₃ nanoparticles protected by β-cyclodextrin (β-CD) as substrate prepared in our lab. The optimum experimental conditions were obtained from single factor procedure and response surface modeling. A linear relationship (I_SERS = 508.96c + 31987.87, c: nmol L^-1, R² = 0.996) between SERS intensity and the concentration of nitrofurazone in the range of 3.3 - 667.0 nmol L^-1 was established, the limit of detection (LOD) was found at nmol L^-1 level (0.37 nmol L^-1 by 3S₀/S). The selectivity for the method was studied by the influences of foreign substances on the determination. The recoveries and RSD (n = 5) for the six meat samples were 95.1 % - 104.5% and 2.4 % - 4.8% respectively, which suggesting that the new SERS method was successfully to detecting nitrofurazone.

Engineering of core−shell Au nanorods@ZIF−8 electrocatalyst for sensitive voltammetric determination of 2−chlorophenol in aquaculture

Herein, polyvinylpyrrolidone−stabilized Au nanorods were controllably implanted into ZIF−8 to form well−uniformed AuNRs@ZIF−8 electrocatalyst with multicore−shell structure. After characterizing the chemical and physical properties, a novel electrochemical sensing platform was fabricated for 2−chlorophenol (2−CP) monitoring based on the AuNRs@ZIF−8 modified glassy carbon electrode. Due to the unique electrochemical property of AuNRs cores and ultra−porous architecture of ZIF−8 shell, the electrocatalyst would effectively accelerate the electron transfer and greatly improve the electrochemical response of 2−CP. Under the optimized experimental conditions, the oxidation peak current of 2−CP enhanced linearly with the increase of its concentration between 0.010 and 40 μM, and the limit of detection was 3.6 nM based on S/N = 3. Meanwhile, the prepared AuNRs@ZIF−8 electrode showed favorable stability, reproducibility, and selectivity, which could be applied to the accurate analysis of 2−CP in aquaculture with standard addition recovery ranging from 96.67% to 104.0%.

Electrochemical sensing of nitrofurazone on Ru(bpy)32+ functionalized polyoxometalate combined with graphene modified electrode

Nitrofurazone is forbidden to be used in aquaculture, but it is often used illegally because of its good bactericidal effect, and its content in animals is extremely low and difficult to detect directly. Hence, a functionalized polyoxometalate combined with graphene modified electrodes through layer-by-layer assembly has achieved a sensitive detection of nitrofurazone in a pH = 6 Na₂HPO₄-citrate buffer solution and its detection limit as low as 0.08952 μM. Nitrofurazone has accelerated its electron transfer through [Ru-PMo₁₂/PDDA-GO]₃ modified electrode, thus realizing its direct detection at low levels through actual samples. This study provides a new perspective for the direct detection of nitrofurazone by electrochemical methods, which is of great significance for the supervision of nitrofurazone and the improvement of the quality and safety of aquatic products.

Electrochemically functionalized graphene for highly sensitive detection of nitrofurazone

The electrochemically functionalized graphene nanosheets (EGS) possesses more oxygen-containing groups and higher defect level, showing superior electrochemical sensing performance.

Electrochemical characterization of and theoretical insight into a series of 2D MOFs, [M(bipy)(C4O4)(H2O)2]·3H2O (M = Mn (1), Fe (2), Co (3) and Zn (4)), for chemical sensing applications

The electrochemical sensing applications of a series of water-stable 2D metal–organic framework (MOF)-modified screen-printed carbon electrodes (SPCEs) are reported. The MOF materials in this study are [M(bipy)(C₄O₄)(H₂O)₂]·3H₂O, in which bipy = 4,4′-bipyridine and M = Mn, Fe, Co and Zn. The MOF materials are characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), showing that the MOFs have a layer-by-layer rod structure with a smooth surface. We use the nitrofurazone molecule as a probe to investigate the influence of the metal ions of MOFs on electrochemical sensing ability. Cyclic voltammetry demonstrated that the Mn-MOF electrode of interest delivered stronger signals than that of other electrodes. Through first-principles calculations, we also revealed that the change in the spin polarization of divalent metal ions passing from the free ion state to the MOF environment appeared to be significantly correlated with the enhancement in the peak response current. The theoretical and experimental results consistently indicate that Mn-MOF has the smallest bandgap and good sensitivity among these MOF materials. Accordingly, we proposed a simple model to illustrate this observation and disclosed the importance of the electron configuration of the transition metal constructing the MOF materials used in improving electrochemical sensing applications.

Framework-to-metal charge transfer of the MOF materials results in enhancing electrochemical sensing ability to nitrofurazone.

Improving sensitivity of antimicrobial drug nitrofurazone detection in food and biological samples based on nanostructured anatase-titania sheathed reduced graphene oxide

In this study, we have prepared anatase titanium (IV) oxide warped reduced graphene oxide nanocomposites (TiO₂-rGO NC) using ultrasonic methodology. The morphology of the TiO₂-rGO NC was studied using FESEM and TEM. In addition, XRD, Raman, thermogravimetric analysis (TGA) and XPS are used to analyze the crystallinity and chemical composition of the TiO₂-rGO NC. We have also investigated the electrochemical behavior of the as-prepared NCs with electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and different pulse voltammetry techniques (DPV). The TiO₂-rGO NC modified electrode shows the lower charge transfer resistance (R _ct ) of 62.87 Ω. Next, the glassy carbon electrode (GCE) was modified with sonochemically prepared TiO₂-rGO NC and used to determine the electrocatalytic reduction of nitrofurazone (NTF). Thus, the proposed sensor established the wider covering range (WCR) of 0.01 to 380 µM and an excellent detection limit of 2.28 nM. Finally, the TiO₂-rGO NC/GCE was applied to determine the NTF in real samples, including crayfish and human blood serum samples, which acquired good found and recovery values.