In-situ growth of 3D Cu-MOF on 1D halloysite nanotubes/reduced graphene oxide nanocomposite for simultaneous sensing of dopamine and paracetamol

One-step electrodeposition of MWCNTs-Cu MOF films for the ratiometric electrochemical analysis of glyphosate

Sensitive and accurate determination of glyphosate (GLYP) is vital for food safety and environmental protection. Herein, a novel electrochemical ratiometric biosensor was designed for the accurate quantification of GLYP through one-step electrodeposition of MWCNTs-Cu MOF films. MWCNTs-Cu MOF nanostructures were directly electro-synthesized in situ on the electrode from the precursor solution. The combination of Cu MOFs with MWCNTs not merely improved the conductivity of MOFs, but also enhanced the sensitivity of the biosensor. Furthermore, Cu sites within Cu MOFs were turned into CuCl to further amplify the current signal and enable the specific recognition of GLYP through competing reactions with the transformation of CuCl into non-electroactive Cu-GLYP. Meanwhile, internal reference molecules of methylene blue (MB) were incorporated to improve the measurement accuracy of GLYP for reducing unpredictable measurement errors aroused by environmental deviations. The ratiometric electrochemical sensor exhibited a high linearity with the logarithmic value of GLYP concentration from 0.5 nM to 400 nM. The detection limit was estimated to be as low as 0.014 nM. Finally, the present sensor with ratiometric signal export was applied for GLYP analysis in real samples with high sensitivity and accuracy. The simplicity and reliability of the ratiometric sensor make it a worthy and powerful tool for food and environmental monitoring. This design strategy also provides an avenue for the development of simple and efficient biosensors for other substances.

Detection of paracetamol by a montmorillonite-modified carbon paste sensor: A study combining MC simulation, DFT computation and electrochemical investigations

This study aims to develop a suitable electrochemical electrode through the incorporation of potassium montmorillonite (MMTK10)clay into the carbon matrix for the direct and sensitive determination of paracetamol (PAR) in pharmaceutical formulations. Electrochemical characterization of the electrodes involves the use of techniques such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). The results reveal that the voltammetric response of PAR is linear over a wide concentration range (1.0-15 μM), with a low detection limit of 0.46 μM. Analytically, PAR recovery results were around 94%, indicating that the developed electrode is highly suitable for PAR detection in pharmaceutical formulation. Additionally, density functional theory (DFT) is employed to investigate the reactivity of PAR and explain the interaction process of PAR on the electrode surface at different pH values. A Monte Carlo simulations model is developed to provide a deeper understanding of the adsorption mechanism, particularly to comprehend molecular interactions and preferential orientations of PAR with MMT fractions at the electrode surface. Reduced Density Gradient is calculated and discussed using techniques such as Multiwfn and Visualization of Molecular Dynamics. The developed CPE-MMTK10 sensor provided a simple preparation method, rapid response, high sensitivity, reproducibility, strong selectivity, and extended stability. Moreover, there is a good correlation between most parameters calculated by DFT and experimental results, thereby reinforcing the validity of the theoretical approach in this study.

Fabrication of Strontium Molybdate with Functionalized Carbon Nanotubes for Electrochemical Determination of Antipyretic Drug-Acetaminophen

In recent years, there has been a significant interest in the advancement of electrochemical sensing platforms to detect antipyretic drugs with high sensitivity and selectivity. The electrochemical determination of acetaminophen (PCT) was studied with strontium molybdate with a functionalized carbon nanotube (SrMoO4@f-CNF) nanocomposite. The SrMoO4@f-CNF nanocomposite was produced by a facial hydrothermal followed by sonochemical treatment, resulting in a significant enhancement in the PCT determination. The sonochemical process was applied to incorporate SrMoO4 nanoparticles over f-CNF, enabling a network-like structure. Moreover, the produced SrMoO4@f-CNF composite structural, morphological, and spectroscopic properties were confirmed with XRD, TEM, and XPS characterizations. The synergistic effect between SrMoO4 and f-CNF contributes to the lowering of the charge transfer resistance (Rct=85 Ω·cm2), a redox potential of Epc=0.15 V and Epa=0.30 V (vs. Ag/AgCl), and a significant limit of detection (1.2 nM) with a wide response range of 0.01-28.48 µM towards the PCT determination. The proposed SrMoO4@f-CNF sensor was studied with differential pulse voltammetry (DPV) and cyclic voltammetry (CV) techniques and demonstrated remarkable electrochemical properties with a good recovery range in real-sample analysis.

Development of metal free carbon catalyst derived from Parthenium hysterophorus for the electrochemical detection of dopamine

Parthenium hysterophorus, one of the seven most hazardous weeds is widely known for its allergic, respiratory and skin-related disorders. It is also known to affect biodiversity and ecology. For eradication of the weed, its effective utilization for the successful synthesis of carbon-based nanomaterial is a potent management strategy. In this study, reduced graphene oxide (rGO) was synthesized from weed leaf extract through a hydrothermal-assisted carbonization method. The crystallinity and geometry of the as-synthesized nanostructure are confirmed from the X-ray diffraction study, while the chemical architecture of the nanomaterial is ascertained through X-ray photoelectron spectroscopy. The stacking of flat graphene-like layers with a size range of ∼200-300 nm is visualized through high-resolution transmission electron microscopy images. Further, the as-synthesized carbon nanomaterial is advanced as an effective and highly sensitive electrochemical biosensor for dopamine, a vital neurotransmitter of the human brain. Nanomaterial oxidizes dopamine at a much lower potential (0.13 V) than other metal-based nanocomposites. Moreover, the obtained sensitivity (13.75 and 3.31 μA μM-1 cm-2), detection limit (0.6 and 0.8 μM), the limit of quantification (2.2 and 2.7 μM) and reproducibility calculated through cyclic voltammetry/differential pulse voltammetry respectively outcompete many metal-based nanocomposites that were previously used for the sensing of dopamine. This study boosts the research on the metal-free carbon-based nanomaterial derived from waste plant biomass.

Electrochemically reduced graphene oxide films from Zn-C battery waste for the electrochemical determination of paracetamol and hydroquinone

Contributing to the development of sustainable electroanalytical chemistry, electrochemically reduced graphene oxide (ERGO) films obtained from residual graphite of discharged Zn-C batteries are proposed in this work. Graphite from the cathode of discarded Zn-C batteries was recovered and used in the synthesis of graphene oxide (GO) by the modified Hummer's method. The quality of the synthesized GO was verified using different characterization methods (FT-IR, XRD, SEM, and TEM). GO films were deposited on a glassy carbon electrode (GCE) by the drop coating method and then electrochemically reduced by cathodic potential scanning using cyclic voltammetry. The electrochemical features of the ERGO films were investigated using the ferricyanide redox probe, as well as paracetamol (PAR) and hydroquinone (HQ) molecules as model analytes. From the cyclic voltammetry assays, enhanced heterogeneous electron transfer rate constants (k⁰) were observed for all redox systems studied. In analytical terms, the ERGO-based electrode showed higher analytical sensitivity than the bare and GO-modified GCE. Using differential pulse voltammetry, wide linear response ranges and limits of detection of 0.14 μmol L^-1 and 0.65 μmol L^-1 were achieved for PAR and HQ, respectively. Furthermore, the proposed sensor was successfully applied to the determination of PAR and HQ in synthetic urine and tap water samples (recoveries close to 100%). The outstanding electrochemical and analytical properties of the proposed ERGO films are added to the very low cost of the raw material, being presented as a green-based alternative for the development of electrochemical (bio)sensors with unsophisticated resources.

Halloysite nanotube/black phosphorene nanohybrid modified screen-printed carbon electrode as an ultra-portable electrochemical sensing platform for smartphone-capable detection of maleic hydrazide with machine learning assistance

With the assistance of machine learning (ML), black phosphorene (BP) stabilized by silver nanoparticles (AgNPs) is used to modify halloysite nanotube (HNT) to obtain highly conductive nanomaterials, HNT/BP-AgNPs, which are morphologically characterized and elementally analyzed. Artificial neural network (ANN) and least squares support vector machine (LS-SVM) are adopted for the intelligent and rapid analysis of maleic hydrazide (MH). An ultra-portable electrochemical sensor bases on HNT/BP-AgNPs modifying screen-printed carbon electrode (SPCE), smartphone and mini-palm potentiostat for detection of MH in the linear range 0.7-55 μM with limit of detection (LOD) of 0.3 μM. For comparison, a traditional electrochemical sensor is fabricated by glass carbon electrode (GCE), desktop computer and large electrochemical potentiostat, and the linear range is 0.3-600 μM with low LOD of 0.1 μM. The ultra-portable electrochemical sensor combined with ML for the detection of MH in sweat potato and carrot gain satisfactory recoveries.

MOFs-Modified Electrochemical Sensors and the Application in the Detection of Opioids

Opioids are widely used in clinical practice, but drug overdoses can lead to many adverse reactions, and even endanger life. Therefore, it is essential to implement real-time measurement of drug concentrations to adjust the dosage given during treatment, keeping drug levels within therapeutic levels. Metal-Organic frameworks (MOFs) and their composite materials modified bare electrode electrochemical sensors have the advantages of fast production, low cost, high sensitivity, and low detection limit in the detection of opioids. In this review, MOFs and MOFs composites, electrochemical sensors modified with MOFs for the detection of opioids, as well as the application of microfluidic chips in combination with electrochemical methods are all reviewed, and the potential for the development of microfluidic chips electrochemical methods with MOFs surface modifications for the detection of opioids is also prospected. We hope that this review will provide contributions to the study of electrochemical sensors modified with MOFs for the detection of opioids.

One-step synthesized biogenic nanoparticles using Linum usitatissimum: Application of sun-light photocatalytic, biological activity and electrochemical H2O2 sensor

This study aimed to synthesize Ag NPs as a green catalyst for photocatalytic activity and to examine their biological activities. It was determined that they have high activity in catalytic and biological activities. The green synthesis which is an environmentally friendly and inexpensive method was used to synthesize Ag-NPs using Linum usitatissimum as a reducing agent. Transmission electron microscopy (TEM), infrared to Fourier transform infrared (FTIR) spectroscopy, UV-Visible (UV-Vis) spectroscopy, and X-ray diffraction (XRD) were used to characterize the Ag NPs. In UV-Vis examination, Ag-NPs had intense peaks in the 435 nm region. The antibacterial activity of Ag NPs was investigated, and Ag NPs showed a high lethal effect against S. aureus, E. coli, B. subtilis, and MRSA. In addition, Ag NPs were tested for anticancer activity against the HT-29 colon cancer cell line, MDA-MB-231 breast cancer cell line, healthy cell line L929-Murine Fibroblast cell Lines, and MIA PaCa-2 human pancreatic cancer cell line at various concentrations (1-160 μg/mL) and showed a high anticancerogenic properties against MDA-MB-231 cells. Ag NPs showed the ability of DNA cleavage activity. Also, the antioxidant activity of Ag NPs against DPPH was found to be 80% approximately. Furthermore, the photocatalytic activity of Ag NPs against methylene blue (MB) was determined to be 67.13% at the 180^th min. In addition, it was observed that biogenic Ag NPs have high electrocatalytic activity for hydrogen peroxide (H₂O₂) detection. In the sensor based on Ag NPs, linearity from 1 μM to 5 μM was observed with a detection limit (LOD) of 1.323 μM for H₂O_2. According to these results, we conclude that the biogenic Ag NPs synthesized using Linum usitatissimum extract can be developed as an efficient biological agent as an antibacterial and anticancer also can be used as a photocatalyst for industrial wastewater treatment to prevent wastewater pollution.

Advanced Nanomaterials-Based Electrochemical Biosensors for Catecholamines Detection: Challenges and Trends

Catecholamines, including dopamine, epinephrine, and norepinephrine, are considered one of the most crucial subgroups of neurotransmitters in the central nervous system (CNS), in which they act at the brain's highest levels of mental function and play key roles in neurological disorders. Accordingly, the analysis of such catecholamines in biological samples has shown a great interest in clinical and pharmaceutical importance toward the early diagnosis of neurological diseases such as Epilepsy, Parkinson, and Alzheimer diseases. As promising routes for the real-time monitoring of catecholamine neurotransmitters, optical and electrochemical biosensors have been widely adopted and perceived as a dramatically accelerating development in the last decade. Therefore, this review aims to provide a comprehensive overview on the recent advances and main challenges in catecholamines biosensors. Particular emphasis is given to electrochemical biosensors, reviewing their sensing mechanism and the unique characteristics brought by the emergence of nanotechnology. Based on specific biosensors' performance metrics, multiple perspectives on the therapeutic use of nanomaterial for catecholamines analysis and future development trends are also summarized.

A novel sensing platform for electrochemical detection of metronidazole antibiotic based on green-synthesized magnetic Fe3O4 nanoparticles

The spread of antibiotic resistant genes has become a serious global concern. Thus, the development of efficient antibiotic monitoring systems to reduce their environmental risks is of great importance. Here, a potent electrochemical sensor was fabricated to detect metronidazole (MNZ) on the basis of green synthesis of Fe₃O₄ nanoparticles (NPs) using Sambucus ebulus L. leaves alcoholic plant extract as a safe and impressive reducing and stabilizing agent. Several analyses such as X-ray diffraction (XRD), Fourier transform infrared spectrophotometer (FTIR), thermogravimetric analysis (TGA), field emission scanning electron microscope (FESEM), energy dispersive X-ray spectroscopy (EDX), and dynamic light scattering (DLS) confirmed the production of homogeneous, monodisperse, regular, and stable magnetite NPs with a spherical morphology. The as-prepared Fe₃O₄NPs were afterwards applied to evaluate the electrochemical activity of MNZ by merging them with graphene nanosheets (GR NSs) on the glassy carbon electrode (GCE). The GR/Fe₃O₄NPs/GCE represented extraordinary catalytic activity toward MNZ with two dynamic ranges of 0.05-5 μM and 5-120 μM, limit of detection (LOD) of 0.23 nM, limit of quantification (LOQ) of 0.76 nM, and sensitivity of 7.34 μA μM^-1 cm^-2. The fabricated sensor was further employed as a practical tool for electrochemical detection of MNZ in real aqueous samples.