Fabrication of FeVO4/RGO Nanocomposite: An Amperometric Probe for Sensitive Detection of Methyl Parathion in Green Beans and Solar Light-Induced Degradation

Pesticide usage is one of the significant issues in modern agricultural practices; hence, monitoring pesticide content and its degradation is of utmost importance. A novel and simple one-pot deep eutectic solvent-based solvothermal method has been developed for the synthesis of FeVO₄/reduced graphene oxide (FeV/RGO) nanocomposite. The band gap of FeV decreased upon anchoring with RGO. Enhanced activity in the detection and photocatalytic degradation has been achieved in the FeV/RGO nanocomposite compared to pure FeV and RGO. FeV/RGO was used to modify glassy carbon electrode (GCE), and the fabricated electrode was evaluated for its electrochemical detection of methyl parathion (MP). The amperometric technique was found to be more sensitive with a 0.001-260 μM (two linear ranges; 0.001-20 and 25-260 μM) wide linear range and low limit of detection value (0.70 nM). The practical applicability of modified GCE is more selective and sensitive to real samples like river water and green beans. Photocatalytic degradation of MP has been examined using FeV, RGO, and FeV/RGO nanocomposite. FeV/RGO managed to degrade 95% of MP under solar light in 80 min. Degradation parameters were optimized carefully to attain maximum efficiency. Degradation intermediates were identified using liquid chromatography-mass spectrometry analysis. The degradation mechanism has been studied in detail. FeV/RGO could serve as a material of choice in the field of electrochemical sensors as well as heterogeneous catalysis toward environmental remediation.

Graphene/g-carbon nitride (GO/g-C3N4) nanohybrids as a sensor material for the detection of methyl parathion and carbendazim

The widespread use of methyl parathion (MP) and carbendazim (CBZ) as pesticide molecules for controlling pests and protect crops has added pollution issues; excess usage of these can lead to atmospheric pollution through contaminating water and soil sources. In the present study, detection of these compounds at the trace level was achieved by employing graphene oxide (GO) and graphitic carbon nitride (g-C₃N₄) nanohybrid electrode assembly (GO/g-C₃N₄/GCE). The X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), and Atomic Force Microscopy (AFM) techniques were also used to characterize the materials developed to reveal their purity, crystal structure, and morphology. The complete voltammetric behavior of these analytes was investigated using cyclic voltammetic (CV) and square wave voltammetry (SWV) techniques. The influence of pH was studied and it was noticed that electrochemical response was the highest at pH 7.0 for MP and at pH 4.2 for CBZ. Density Functional Theory (DFT) calculations could help us to understand the adsorption behavior of MP and CBZ onto the GO and g-C₃N₄ before their degradation due to the electrochemical reactions. SWV technique was helpful in the trace level detection of MP and CBZ. Linearity plots were obtained in the range of concentration from 8.0 × 10^-8 M to 1.0 × 10^-4 M with a limit of detection 0.824 nM for MP and 1.0 × 10^-8 M to 2.5 × 10^-4 M for CBZ with the detection limit of 2.82 nM. Significance of the developed method in the field of agricultural and environmental domains was successfully investigated by monitoring MP and CBZ in water and soil samples, and the obtained results suggested the selectivity, stability, and reproducibility of the newly developed GO/g-C₃N₄/GCE electrode assembly.

A FRET Approach to Detect Paraoxon among Organophosphate Pesticides Using a Fluorescent Biosensor

The development of faster, sensitive and real-time methods for detecting organophosphate (OP) pesticides is of utmost priority in the in situ monitoring of these widespread compounds. Research on enzyme-based biosensors is increasing, and a promising candidate as a bioreceptor is the thermostable enzyme esterase-2 from Alicyclobacillus acidocaldarius (EST2), with a lipase-like Ser-His-Asp catalytic triad with a high affinity for OPs. This study aimed to evaluate the applicability of Förster resonance energy transfer (FRET) as a sensitive and reliable method to quantify OPs at environmentally relevant concentrations. For this purpose, the previously developed IAEDANS-labelled EST2-S35C mutant was used, in which tryptophan and IAEDANS fluorophores are the donor and the acceptor, respectively. Fluorometric measurements showed linearity with increased EST2-S35C concentrations. No significant interference was observed in the FRET measurements due to changes in the pH of the medium or the addition of other organic components (glucose, ascorbic acid or yeast extract). Fluorescence quenching due to the presence of paraoxon was observed at concentrations as low as 2 nM, which are considered harmful for the ecosystem. These results pave the way for further experiments encompassing more complex matrices.

Recent Advances on Detection of Insecticides Using Optical Sensors

Insecticides are enormously important to industry requirements and market demands in agriculture. Despite their usefulness, these insecticides can pose a dangerous risk to the safety of food, environment and all living things through various mechanisms of action. Concern about the environmental impact of repeated use of insecticides has prompted many researchers to develop rapid, economical, uncomplicated and user-friendly analytical method for the detection of insecticides. In this regards, optical sensors are considered as favorable methods for insecticides analysis because of their special features including rapid detection time, low cost, easy to use and high selectivity and sensitivity. In this review, current progresses of incorporation between recognition elements and optical sensors for insecticide detection are discussed and evaluated well, by categorizing it based on insecticide chemical classes, including the range of detection and limit of detection. Additionally, this review aims to provide powerful insights to researchers for the future development of optical sensors in the detection of insecticides.

FRET-based Solid-state Luminescent Glyphosate Sensor Using Calixarene-grafted Ruthenium(II)bipyridine Doped Silica Nanoparticles

Calixarene-functionalized luminescent nanoparticles were successfully fabricated for the FRET-based selective and sensitive detection of the organophosphorus pesticide glyphosate (GP). p-Tert-butylcalix[4]arene was grafted on the surface of [Ru(bpy)₃ ]²⁺ incorporated SiNps to produce self-assembled nanosensors (RSC). FRET was switched on in the presence of GP by means of energy transfer due to binding with p-tert-butylcalix[4]arene grafted on the surface of the RSC. The FRET efficiency of the GP-RSC system was increased gradually with the addition of GP. The FRET efficiency was evaluated as 87.69 % and a high binding affinity was established by the binding constant value, 1.16×10⁷  M^-1 , using a Langmuir binding isotherm plot. The estimated limit of detection (LOD) was 7.91×10^-7  M, which was lower than the Environmental Protection Agency (EPA) recommendation. The probe also effectively responds to real sample analysis. The sensitivity and selectivity was realized due to the efficient FRET towards the fluorescence properties of the [Ru(bpy)₃ ]²⁺ complex.

l-Cysteine-capped CdTe quantum dots as a fluorescent probe for sequential detection of lysozyme and trypsin

A fluorescence assay for the sequential determination of lysozyme and trypsin was established based on l-cysteine capped CdTe quantum dots. Lysozyme with positive charges can interact with l-cysteine capped CdTe quantum dots. Lysozyme can be hydrolyzed into small fragments in the presence of trypsin, and the interaction between l-cysteine-capped CdTe QDs and lysozyme would be inhibited, which could be used for trypsin quantification.