Amperometric sensor based on ZIF/g-C3N4/RGO heterojunction nanocomposite for hydrazine detection

2D Z-scheme ZnIn2S4/g-C3N4 heterojunction based on photoelectrochemical immunosensor with enhanced carrier separation for sensitive detection of CEA

Semiconducting materials based on photoelectrochemical (PEC) sensors have been widely utilized for detection. Meanwhile, the sensitivity of the PEC sensor was limited by low-efficiency carrier separation. Thus, a novel sandwich-type PEC bioimmunosensing based on 2D Z-scheme ZnIn2S4/g-C3N4 heterojunction as a photosensitive material and BiVO4 as a photoquencher was designed for the sensitive detection of carcinoembryonic antigen (CEA). Firstly, the 2D ZnIn2S4/g-C3N4 structure provided a multitude of activated sites which facilitated the loading of the capture antibody (Ab1). Secondly, the Z-scheme heterojunction had a high redox capacity while promoting the rapid separation and migration of photogenerated electron-hole pairs (e-/h+). Thus it was able to consume more electron donors to a certain extent, resulting in a higher initial photocurrent. In addition, BiVO4 with large spatial potential resistance was introduced for the first time to realize signal amplification. BiVO4 could not only compete with substrate materials for electron donors, but also effectively prevent electron donors from contacting the substrate, further reducing the photocurrent signal. Under optimized conditions, the sensor had a favorable detection range (0.0001-100 ng/mL) to CEA and a low detection limit of 0.03 pg/mL. With high specificity, excellent stability, and remarkable reproducibility, this sensor provided a new perspective for constructing accurate and convenient PEC immunosensor for bioanalysis and early disease diagnosisdisease diagnosis.

Review on Surface-Modified Electrodes for the Enhanced Electrochemical Detection of Selective Serotonin Reuptake Inhibitors (SSRIs)

Selective serotonin re-uptake inhibitors (SSRIs) are one of the most commonly prescribed classes of antidepressants used for the treatment of moderate to severe depressive disorder, personality disorders and various phobias. This class of antidepressants was created with improved margins of safety. However, genetic polymorphism may be responsible for the high variability in patients' responses to treatment, ranging from failure to delayed therapeutic responses to severe adverse effects of treatment. It is crucial that the appropriate amount of SSRI drugs is administered to ensure the optimum therapeutic efficacy and intervention to minimise severe and toxic effects in patients, which may be the result of accidental and deliberate cases of poisoning. Determining SSRI concentration in human fluids and the environment with high sensitivity, specificity and reproducibility, and at a low cost and real-time monitoring, is imperative. Electrochemical sensors with advanced functional materials have drawn the attention of researchers as a result of these advantages over conventional techniques. This review article aims to present functional materials such as polymers, carbon nanomaterials, metal nanomaterials as well as composites for surface modification of electrodes for sensitive detection and quantification of SSRIs, including fluoxetine, citalopram, paroxetine, fluvoxamine and sertraline. Sensor fabrication, sensor/analyte interactions, design rationale and properties of functional material and the electrocatalytic effect of the modified electrode on SSRI detection are discussed.

Calf thymus ds-DNA intercalation with pendimethalin herbicide at the surface of ZIF-8/Co/rGO/C3N4/ds-DNA/SPCE; A bio-sensing approach for pendimethalin quantification confirmed by molecular docking study

Pendimethalin (PND) is a herbicide that is regarded to be possibly carcinogenic to humans and toxic to the environment. Herein, we fabricated a highly sensitive DNA biosensor based on ZIF-8/Co/rGO/C₃N₄ nanohybrid modification of a screen-printed carbon electrode (SPCE) to monitor PND in real samples. The layer-by-layer fabrication pathway was conducted to construct ZIF-8/Co/rGO/C₃N₄/ds-DNA/SPCE biosensor. The physicochemical characterization techniques confirmed the successful synthesis of ZIF-8/Co/rGO/C₃N₄ hybrid nanocomposite, as well as the appropriate modification of the SPCE surface. The utilization of ZIF-8/Co/rGO/C₃N₄ nanohybrid as a modifier was analyzed using. The electrochemical impedance spectroscopy results showed that the modified SPCE exhibited significantly lowered charge transfer resistance due to the enhancement of its electrical conductivity and facilitation of the transfer of charged particles. The proposed biosensor successfully quantified PND in a wide concentration range of 0.01-35 μM, with a limit of detection (LOD) value of 8.0 nM. The PND monitoring capability of the fabricated biosensor in real samples including rice, wheat, tap, and river water samples was verified with a recovery range of 98.2-105.6%. Moreover, to predict the interaction sites of PND herbicide with DNA, the molecular docking study was performed between the PND molecule and two sequence DNA fragments and confirmed the experimental findings. This research sets the stage for developing highly sensitive DNA biosensors that will be used to monitor and quantify toxic herbicides in real samples by fusing the advantages of nanohybrid structures with crucial knowledge from a molecular docking investigation.

Electrochemical Sensors Based on a Composite of Electrochemically Reduced Graphene Oxide and PEDOT:PSS for Hydrazine Detection

In this study, hydrazine sensors were developed from a composite of electrochemically reduced graphene oxide (ErGO) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), deposited onto a glassy carbon electrode (GCE). The structural properties, electrochemical characterization, and surface morphologies of this hydrazine sensor were characterized by Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). In addition, the proposed hydrazine sensor also demonstrates good electrochemical and analytical performance when investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and amperometry techniques under optimal parameters. Using these investigated parameters, DPV and amperometry were chosen as techniques for hydrazine measurements and showed a linear range of concentration in the range of 0.2-100 μM. The obtained limits of detection and limits of quantitation for hydrazine measurements were 0.01 and 0.03 μM, respectively. In addition, the proposed sensor demonstrated good reproducibility and stability in hydrazine measurements in eight consecutive days. This fabricated hydrazine sensor also exhibited good selectivity against interference from Mg²⁺, K⁺, Zn²⁺, Fe²⁺, Na⁺, NO₂ ^-, CH₃COO^-, SO₄ ^2-, Cl^-, ascorbic acid, chlorophenol, and triclosan and combined interferences, as well as it depicted %RSD values of less than 5%. In conclusion, this proposed sensor based on GCE modified with ErGO/PEDOT:PSS displays exceptional electrochemical performance for use in hydrazine measurements and have the potential to be employed in practical applications.

Determination of D&C Red 33 and Patent Blue V Azo dyes using an impressive electrochemical sensor based on carbon paste electrode modified with ZIF-8/g-C3N4/Co and ionic liquid in mouthwash and toothpaste as real samples

Synthetic azo dyes are widely used in a variety of industries, but many of them pose a risk to human health, particularly when consumed in large quantities. As a result, their existence in products should be closely monitored. D&C red 33 and Patent Blue V are mostly used in cosmetics, especially in toothpaste and mouthwashes. A novel carbon paste electrode modified with ZIF-8/g-C3N4/Co nanocomposite and 1-methyl-3-butylimidazolium bromide as an ionic liquid was employed as a highly sensitive reproducible electrochemical sensor for the simultaneous determination of these common dyes. ZIF structure has unique properties such as high surface area, suitable conductivity, and excellent porosity. The electrochemical behavior of the suggested electrode was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). To characterize the synthesized nanocomposites, scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were applied to investigate the structure of nanocomposites. Under the optimized conditions, the modified sensor offered a wide linear concentration range 0.08-10 μM (R2 = 0.9906) and 10-900 μM (R2 = 0.9932) with a low limit of detection of 0.034 μM. The value of diffusion coefficient (D), and the electron transfer coefficient (α) was calculated to be 310 × 10-5, and 0.9 respectively. This technique offered a successful performance for the determination of target analyte in the real samples with acceptable results between 96% and 107%.

A 2D/2D NiCo-MOF/Ti3C2 heterostructure for the simultaneous detection of acetaminophen, dopamine and uric acid by differential pulse voltammetry

A 2D/2D NiCo-MOF/Ti₃C₂ heterojunction is constructed as a non-enzymatic biosensor for the simultaneous electrochemical detection of acetaminophen (AP), dopamine (DA), and uric acid (UA) via differential pulse voltammetry. Benefiting from the synergistic effects of the high electrocatalytic activity of NiCo-MOF, the outstanding conductivity of Ti₃C₂, and the improved specific surface area of NiCo-MOF/Ti₃C₂, NiCo-MOF/Ti₃C₂ displays high sensing performance toward AP (0.01-400 μM), DA (0.01-300 μM), and UA (0.01-350 μM) in 0.1 M phosphate buffer (PB, pH 7.4) at working potentials of 0.346 V vs. SCE for AP, 0.138 V vs. SCE for DA, and 0.266 V vs. SCE for UA. Furthermore, the well-separated oxidation peak potentials allow for the simultaneous detection of the analytes, with detection limits of 0.008, 0.004, and 0.006 μM (S/N = 3), respectively. As a result of its considerable reproducibility and anti-interference and anti-fouling properties, NiCo-MOF/Ti₃C₂ was also developed into a practical sensing platform to detect AP, DA, and UA in serum and urine, presenting excellent recoveries of 98.1-102.2 %.