Facile Synthesis of Ordered Mesoporous Zirconia for Electrochemical Enrichment and Detection of Organophosphorus Pesticides

Zr-based metalloporphyrin MOF probe for electrochemical detection of parathion-methyl

An electrochemical (EC) sensor based on metalloporphyrin metal-organic framework (MOF) for the detection of parathion-methyl (PM) has been developed. The prepared MOF-525(Fe) exhibits great signal enhancement toward the electrochemical detection of PM owing to its unique structural properties and electrochemical activities. Under optimal experimental conditions, the as-prepared MOF-525(Fe) based EC sensor exhibited excellent PM sensing performance with a wide linear detection range (0.1 μM-100 μM) and low limit of detection (LOD, 1.4 nM). Compared to its corresponding Fe metalloporphyrin (linker), MOF-525(Fe) exhibited a superior sensitivity (28.31 μA cm-2·μM-1), which is 3.7 times higher than the sensitivity of FeTCPP linker (7.56 μA cm-2·μM-1) towards PM. The improved performance is associated with the high specific surface area and the large pore channels of MOF-525(Fe) facilitating a better interaction between PM and the Fe metalloporphyrin active sites, especially in the lower concentration range. Moreover, a possible affinity of the PM molecules toward Zr6 clusters may also contribute to the selective enrichment of PM on MOF-525(Fe). This EC sensor further demonstrated high selectivity in the presence of interfering molecules. The recovery results further confirm accurate PM sensing in actual samples, which suggests promising applications for the rapid detection of environmental organophosphates by metalloporphyrin MOFs.

Unleashing the electrochemical performance of zirconia nanoparticles on valve-regulated lead acid battery

The electrochemical act of valve-regulated lead acid batteries can be enhanced by conductive materials like metal oxides. This work aims to examine the preparation and influence of zirconia on poly(vinyl alcohol) based gel valve-regulated lead acid battery. Characterizations like Fourier transform infrared spectroscopy, ionic conductivity, water retention study, cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge-discharge techniques were done. The optimized gel system exhibited a discharge capacity of 198.45 μAh cm-2 at the current density of 0.6 mA cm-2. The battery cell with an optimized gel matrix displayed a maximum discharge capacity of 22.5 μAh at a current of 20 μA. After 500 continuous cycles, the battery attained a discharge capacity retention of 91 %. The presence of zirconia will increase the electrochemical performance of gel valve-regulated lead acid batteries.

Effects of additives on the performance of a laser-induced graphene sensor modified with ZrO2 nanoparticles for OP detection

In this study, a simple and portable electrochemical sensor based on laser-induced graphene (LIG) has been developed to systematically investigate the feasibility of LIG as an electrode to detect organophosphorus pesticides (OPs). It proves that the LIG-based electrode has a relatively high electrochemically active surface area (ECSA) and heterogeneous electron transfer (HET) of 0.100 cm2 and 0.000825 cm s-1, respectively. In addition, zirconium dioxide nanoparticles (ZrO2 NPs) have been modified on the electrode with three different binders, β-cyclodextrin (β-CD), chitosan (CS) and Nafion, to improve the adsorption capacity of the electrode toward OPs, and the effect of the binders on the performance of the as-fabricated sensor has been investigated in detail. The results show that β-CD increases not only the electrochemically active surface area of the electrode but also the redox peak current of methyl parathion (MP). To evaluate the sensitivity of the sensor, differential pulse voltammetry (DPV) curves have been tested in solutions containing different concentrations of MP using ZrO2-β-CD/LIG as an electrode, which shows a detection range of 5-200 ng ml-1 and a detection limit of 0.89 ng ml-1. In summary, the LIG-based sensor has a low detection limit, high sensitivity and good interference resistance, and thus has tremendous potential for the detection of pesticides in the environment.

Novel Additive Manufactured Multielectrode Electrochemical Cell with Honeycomb Inspired Design for the Detection of Methyl Parathion in Honey Samples

The development and increase in the number of crops recently have led to the requirement for greater efficiency in world food production and greater consumption of pesticides. In this context, the widespread use of pesticides has affected the decrease in the population of pollinating insects and has caused food contamination. Therefore, simple, low-cost, and quick analytical methods can be interesting alternatives for checking the quality of foods such as honey. In this work, we propose a new additively manufactured (3D-printed) device inspired by a honeycomb cell, with 6 working electrodes for the direct electrochemical analysis of methyl parathion by reduction process monitoring in food and environmental samples. Under optimized parameters, the proposed sensor presented a linear range between 0.85 and 19.6 μmol L^-1, with a limit of detection of 0.20 μmol L^-1. The sensors were successfully applied in honey and tap water samples by using the standard addition method. The proposed honeycomb cell made of polylactic acid and commercial conductive filament is easy to construct, and there is no need for chemical treatments to be used. These devices based on 6 working electrodes array are versatile platforms for rapid, highly repeatable analysis in food and environment, capable of performing detection in low concentrations.

Improved charge-transfer resonance in graphene oxide/ZrO2 substrates for plasmonic-free SERS determination of methyl parathion

This work reports a sensitive SERS substrate based on graphene oxide (GO) and quantum-sized ZrO₂ nanoparticles (GO/ZrO₂) for label-free determination of the organophosphate pesticide methyl parathion (MP). The enhanced light-matter interactions and the consequent SERS effect in these substrates resulted from the effective charge transfer (CT) mechanism attributed to synergistic contributions of three main factors: i) the strong molecular adherence of the MP molecules and the ZrO₂ surface which allows the first layer-effect, ii) the relatively abundant surface defects in low dimensional ZrO₂ semiconductor NPs, which act as intermediate electronic states that reduce the large bandgap barrier, and iii) the hindered charge recombination derived from the transference of the photoinduced holes to the GO layer. This mechanism allowed an enhancement factor of 8.78 × 10⁴ for GO/ZrO₂-based substrates, which is more than 5-fold higher than the enhancement observed for platforms without GO. A detection limit of 0.12 μM was achieved with an outstanding repeatability (variation ≤4.5%) and a linear range up to 10 μM, which is sensitive enough to determine the maximal MP concentration permissible in drinking water according to international regulations. Furthermore, recovery rates between 97.4 and 102.1% were determined in irrigation water runoffs, strawberry and black tea extracts, demonstrating the reliability of the hybrid GO/ZrO₂ substrate for the organophosphate pesticides quantification in samples related to agri-food sectors and environmental monitoring.

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.

Highly Efficient Transfer Hydrogenation of Biomass-Derived Furfural to Furfuryl Alcohol over Mesoporous Zr-Containing Hybrids with 5-Sulfosalicylic Acid as a Ligand

The catalytic transfer hydrogenation of biomass-derived furfural to furfuryl alcohol under mild conditions is an attractive topic in biorefinery. Herein, mesoporous Zr-containing hybrids (Zr-hybrids) with a high surface area (281.9−291.3 m2/g) and large pore volume (0.49−0.74 cm3/g) were prepared using the biomass-derived 5-sulfosalicylic acid as a ligand, and they were proven to be highly efficient for the Meerwein−Ponndorf−Verley reduction of furfural to furfuryl alcohol at 110 °C, with the highest furfuryl alcohol yield reaching up to 97.8%. Characterizations demonstrated that sulfonic and carboxyl groups in 5-sulfosalicylic acid molecules were coordinated with zirconium ions, making zirconium ions fully dispersed, thus leading to the formation of very fine zirconia particles with the diameter of <2 nm in mesoporous Zr-hybrids. The interaction between the 5-sulfosalicylic acid ligands and zirconium ions endowed mesoporous Zr-hybrids with relatively higher acid strength but lower base strength, which was beneficial for the selective reduction of furfural to furfuryl alcohol. A recycling study was performed over a certain mesoporous Zr-hybrid, namely meso-Zr-SA15, demonstrating that the yield and selectivity of furfuryl alcohol remained almost unchanged during the five consecutive reaction cycles. This study provides an optional method to prepare hybrid catalysts for biomass refining by using biomass-derived feedstock.

Mesoporous Materials-Based Electrochemical Biosensors from Enzymatic to Nonenzymatic

Mesoporous materials have drawn more and more attention in the field of biosensors due to their high surface areas, large pore volumes, tunable pore sizes, as well as abundant frameworks. In this review, the progress on mesoporous materials-based biosensors from enzymatic to nonenzymatic are highlighted. First, recent advances on the application of mesoporous materials as supports to stabilize enzymes in enzymatic biosensing technology are summarized. Special emphasis is placed on the effect of pore size, pore structure, and surface functional groups of the support on the immobilization efficiency of enzymes and the biosensing performance. Then, the development of a nonenzymatic strategy that uses the intrinsic property of mesoporous materials (carbon, silica, metals, and composites) to mimic the behavior of enzymes for electrochemical sensing of some biomolecules is discussed. Finally, the challenges and perspective on the future development of biosensors based on mesoporous materials are proposed.

Analytical methods to analyze pesticides and herbicides

Presented in this paper is an annual review of literatures published in 2018 on topics relating to analytical methods for pesticides and herbicides. According to the different techniques, this review is divided into six sections, including extraction methods; chromatographic or mass spectrometric techniques; electrochemical techniques; spectrophotometric techniques; chemiluminescence and fluorescence methods; and biochemical assays. PRACTITIONER POINTS: Totally 134 relevant research articles are summarized. The review is divided into six parts according to the techniques. Chromatographic and mass spectrometric methods are the most widely used.