Detection Of Pesticides Research Articles

Chlorophyll fluorescence in sentinel plants for the surveillance of chemical risk

This research aimed to develop natural plant systems to serve as biological sentinels for the detection of organophosphate pesticides in the environment. The working hypothesis was that the presence of the pesticide in the environment caused changes in the content of pigments and in the photosynthetic functioning of the plant, which could be evaluated non-destructively through the analysis of reflected light and emitted fluorescence. The objective of the research was to furnish in vivo indicators derived from spectroscopic parameters, serving as early alert signals for the presence of organophosphates in the environment. In this context, the effects of two pesticides, Chlorpyrifos and Dimethoate, on the spectroscopic properties of aquatic plants (Vallisneria nana and Spathyfillum wallisii) were studied. Chlorophyll-a variable fluorescence allowed monitoring both pesticides' presence before any damage was observed at the naked eye, with the analysis of the fast transient (OJIP curve) proving more responsive than Kautsky kinetics, steady-state fluorescence, or reflectance measurements. Pesticides produced a decrease in the maximum quantum yield of PSII photochemistry, in the proportion of PSII photochemical deexcitation relative to PSII non photochemical decay and in the probability that trapped excitons moved electrons into the photosynthetic transport chain beyond QA−. Additionally, an increase in the proportion of absorbed energy being dissipated as heat rather than being utilized in the photosynthetic process, was notorious. The pesticides induced a higher deactivation of chlorophyll excited states by photophysical pathways (including fluorescence) with a decrease in the quantum yields of photosystem II and heat dissipation by non-photochemical quenching. The investigated aquatic plants served as sentinels for the presence of pesticides in the environment, with the alert signal starting within the first milliseconds of electronic transport in the photosynthetic chain. Organophosphates damage animals' central nervous systems similarly to certain compounds found in chemical weapons, thus raising the possibility that sentinel plants could potentially signal the presence of such weapons.

Development of a novel HPLC-CDCL method utilizing nitrogen-doped carbon dots for sensitive and selective detection of dithiocarbamate pesticides in tea

In this study, S-methyl derivatives of dithiocarbamates (DTCs) were shown to significantly enhance chemiluminescence (CL) between Ce(IV) and efficient and environmentally friendly nitrogen-doped carbon dots (NCDs). Based on the elucidation of the CL mechanisms, an innovative approach involving high-performance liquid chromatography coupled with N-CDs and CL detection (HPLC-CDCL) was proposed. The developed method was successfully applied to the highly sensitive detection of three DTC fungicides (dimethyl dithiocarbamate, ethylene bisdithiocarbamate, and propylene bisdithiocarbamate) in tea. The recovery of the established method ranged 70.51–116.45%, with relative standard deviations (RSD) of <9.40%. The limit of detection (S/N = 3) was as low as 0.19 μg/L (as CS2), which is superior to the previous methods and comparable to UPLC-tandem mass spectrometry (MS/MS). Moreover, the proposed approach does not require solid-phase extraction and offers excellent selectivity. This study proposes a novel method for the detection of DTCs in the food safety and environmental fields.

Silver coated PS microsphere array SERS microfluidic chip for pesticide detection

Carbendazim and acetamidine are pesticides that widely used to control pests and diseases in oilseed rape. In this paper, a rapid, accurate and reliable method was proposed for the detection of carbendazim and acetamidine with SERS microfluidic chip technology. Ag-ps(Polystyrene microspheres) microsphere SERS substrate was prepared by spin coating and magnetron sputtering deposition of Ag. The enhancement factor of prepared SERS substrate was 2.4 × 1010. The SERS detection working curves were well fitted and the linear parameters R2 were 0.987 and 0.994, respectively. The limit of detection was 0.01 mg/mL. The use of SERS microfluidic chip to detect carbendazim and acetamidine is expected to provide a way for the detection of pesticide residues in crops, which has broad application prospects in the field of food safety.

Yolk-shell MOF-on-MOF hybrid solid-phase microextraction coatings for efficient enrichment and detection of pesticides: Structural regulation cause performance differences

Metal-organic frameworks (MOFs) based composites with different structure-activity relationships have been widely used in the field of organic pollutant adsorption and extraction. Here, two MOF-on-MOF composites with different structures (yolk-shell and core-shell) from homologous sources were prepared by a simple in-situ growth synthesis method and structural regulation. In order to verify the effect of composite structure on the extraction capacity, the adsorption performance of the yolk-shell structure (YS–NH2-UiO-66@CoZn-ZIF) and the core-shell structured (NH2-UiO-66@CoZn-ZIF) material were compared by using them as coating material of direct immersion solid-phase microextraction (DI-SPME) to enrich six pesticides in five matrices. The results showed that because of the unique hollow hierarchical structure, high specific surface area (930.68 m2 g−1), abundant and open active sites, and synergistic and complementary adsorption forces, YS-NH2-UiO-66@CoZn-ZIF composites had the maximum adsorption amount of 36.01–66.31 mg g−1 under the same experiment condition, which was 6.81%–34.26 % higher than that of NH2-UiO-66@CoZn-ZIF. In addition, the adsorption mechanism of the prepared materials was verified and elaborated through theoretical simulations and material characterization. Under the optimized conditions, the YS-NH2-UiO-66@CoZn-ZIF-coated SPME-HPLC-UV method had a wide linear range (0.241–500 μg L−1), a good linear correlation coefficient (R2 > 0.9988), a low detection limits (0.072–0.567 μg L−1, S/N = 3) and low quantification limits (0.241–1.891 μg L−1, S/N = 10). The relative standard deviations of individual fibers and different batches of fibers were 0.47–6.20 % and 0.22–2.48 %, respectively, and individual fibers could be recycled more than 104 times. This work provided a good synthetic route and comparative ideas for exploring the in-situ growth synthesis of yolk-shell composites with reasonable structure-activity relationships.

A novel competitive color-tone change fluorescence immunochromatographic assay for the ultrasensitive detection of pesticide and veterinary drug residues

One important challenge faced by competitive immunoassay techniques is the inability to visually distinguish weak color changes in the T-line during the detection of trace analyte concentrations. In this study, we introduced multi-color fluorescence into the immunoassay system and developed a novel competitive dual-channel color-tone change fluorescent immunochromatographic assay (CFICA) for the visual and quantitative detection of kanamycin (KAN) and carbendazim (CBZ). At the same time, we have developed matching, portable fluorescence-reading equipment, which can analyse the spectral data of the RGB channel individually and can effectively solve the problems of the traditional single-fluorescence reader – large reading error and poor detection sensitivity. After optimization, our CFICA, combined with the corresponding instrument, achieved low limits of detection (LOD) for KAN and CBZ, as low as 1.98 and 12.82 pg/mL, respectively. We believe that this CFICA detection system, with its high accuracy, low error, and multi-color detection capabilities, holds tremendous potential for visual and multi-channel competitive point-of-care testing.

Effective extraction of pyrethroid pesticides from cabbages using Fe3O4@NU-1000 and adsorption mechanism: An experimental and theoretical study

In this paper, a magnetic zirconium-based MOFs (Fe3O4@NU-1000) with good water stability was prepared for effective extraction of pyrethroid pesticides from vegetables. Characterization results showed Fe3O4@NU-1000 has a high specific surface area (435.34 m2·g−1) and a large pore size (4.88 nm), which provides abundant adsorption sites for pesticides molecules. Fe3O4@NU-1000 can achieve rapid magnetic separation from solution within 1 min, greatly reducing the extraction time of pyrethroid pesticides. The results of adsorption kinetics and isotherms showed that the adsorption process of pyrethroid pesticides on Fe3O4@NU-1000 was monolayer adsorption and physisorption. The maximum adsorption capacities of Fe3O4@NU-1000 for beta-cyfluthrin, lambda-cyhalothrin, permethrin, and bifenthrin were up to 1159.11, 1194.16, 1151.48, and 1181.74 mg·g−1, respectively. Molecular dynamics simulations showed that adsorption is driven by hydrophobic interaction. Van der Waals forces and hydrogen bonding accelerate pesticide molecules to approach the surface, and π–π interactions enable stable adsorption of pesticide molecules within the triangular and hexagonal micropores of NU-1000. DFT calculations confirmed that pesticide molecules predominantly adsorb stably within the pores of Fe3O4@NU-1000 through π–π interactions, with additional contributions from CH3–π and Cl–π interactions. Finally, a simple and sensitive method was established for the determination of pyrethroid pesticides in cabbage samples using Fe3O4@NU-1000 based magnetic solid-phase extraction and high-performance liquid chromatography. It provided low limit of detection (0.0011–0.0058 μg·mL−1), a wide linear range (1–25 μg·mL−1), and satisfactory recoveries (81.35–98.64 %), which can achieve effective extraction and trace detection. This study provides a magnetic MOFs material for extraction of pesticides and reveals its adsorptive mechanism at molecular level, which is helpful for rational design of more pretreatment materials for pesticides detection in complex food matrices.

Nanobiosensors based on on-site detection approaches for rapid pesticide sensing in the agricultural arena: A systematic review of the current status and perspectives.

The extensive use of chemical pesticides has significantly boosted agricultural food crop yields. Nevertheless, their excessive and unregulated application has resulted in food contamination and pollution in environmental, aquatic, and agricultural ecosystems. Consequently, the on-site monitoring of pesticide residues in agricultural practices is paramount to safeguard global food and conservational safety. Traditional pesticide detection methods are cumbersome and ill-suited for on-site pesticide finding. The systematic review provides an in-depth analysis of the current status and perspectives of nanobiosensors (NBS) for pesticide detection in the agricultural arena. Furthermore, the study encompasses the fundamental principles of NBS, the various transduction mechanisms employed, and their incorporation into on-site detection platforms. Conversely, the assortment of transduction mechanisms, including optical, electrochemical, and piezoelectric tactics, is deliberated in detail, emphasizing its advantages and limitations in pesticide perception. Incorporating NBS into on-site detection platforms confirms a vital feature of their pertinence. The evaluation reflects the integration of NBS into lab-on-a-chip systems, handheld devices, and wireless sensor networks, permitting real-time monitoring and data-driven decision-making in agronomic settings. The potential for robotics and automation in pesticide detection is also scrutinized, highlighting their role in improving competence and accuracy. Finally, this systematic review provides a complete understanding of the current landscape of NBS for on-site pesticide sensing. Consequently, we anticipate that this review offers valuable insights that could form the foundation for creating innovative NBS applicable in various fields such as materials science, nanoscience, food technology and environmental science.

Calixarene-Based Supramolecular Sensor Array for Pesticide Discrimination.

The identification and detection of pesticides is crucial to protecting both the environment and human health. However, it can be challenging to conveniently and rapidly differentiate between different types of pesticides. We developed a supramolecular fluorescent sensor array, in which calixarenes with broad-spectrum encapsulation capacity served as recognition receptors. The sensor array exhibits distinct fluorescence change patterns for seven tested pesticides, encompassing herbicides, insecticides, and fungicides. With a reaction time of just three minutes, the sensor array proves to be a rapid and efficient tool for the discrimination of pesticides. Furthermore, this supramolecular sensing approach can be easily extended to enable real-time and on-site visual detection of varying concentrations of imazalil using a smartphone with a color scanning application. This work not only provides a simple and effective method for pesticide identification and quantification, but also offers a versatile and advantageous platform for the recognition of other analytes in relevant fields.

Electrochemical Enrichment of Biocharcoal Modified on Carbon Electrodes for the Detection of Nitrite and Paraxon Ethyl Pesticide

Biocharcoal (BioC), a cost-effective, eco-friendly, and sustainable material can be derived from various organic sources including agricultural waste. However, to date, complex chemical treatments using harsh solvents or physical processes at elevated temperatures have been used to activate and enhance the functional groups of biochar. In this paper, we propose a novel easy and cost-effective activation method based on electrochemical cycling in buffer solutions to enhance the electrochemical performance of biocharcoal derived from almond shells (AS-BioC). The novel electrochemical activation method enhanced the functional groups and porosity on the surface of AS-BioC, as confirmed by microscopic, spectroscopic characterizations. Electrochemical characterization indicated an increase in the conductivity and surface area. A modified SPCE with activated AS-BioC (A.AS-BioC/SPCE), shows enhanced electrochemical performance towards oxidation and reduction of nitrite and paraxon ethyl pesticide, respectively. For both target analytes, the activated electrode demonstrates high electrocatalytic activity and achieves a very LOD of 0.38 µM for nitrite and 1.35 nM for ethyl paraxon with a broad linear range. The sensor was validated in real samples for both contaminants. Overall, the research demonstrates an innovative technique to improve the performance of AS-BioC to use as a modifier material for electrochemical sensors.

Effects of pesticide residues on the growth and yield of vegetables at Navrongo of Ghana

BackgroundThe constant use of pesticides on farmlands is a source of food poison and potential cause of disease to humans in most parts of Africa. The lack of in-depth knowledge on the choices of use of the pesticides and their applications by most farmers in our African communities is a key to unsafe food and unhealthy living. Furthermore, the impact of some of these pesticides on the growth and yield of vegetable crops is largely unexplored. The present research was conducted in the Tono Irrigation Dam area of Navrongo, Ghana, where vegetable cultivation holds substantial economic importance making it a critical aspect of the local economy. In this study, we identified prevalent pesticides used in Navrongo’s vegetable cultivation, quantified pesticide residues present in selected vegetables grown, and assessed the impact of the pesticides on the vegetable crops’ growth and yields.MethodsThirty vegetable farmers at the Tono Irrigation Dam Area, Navrongo were randomly selected, and interviewed face to face. Questionnaires were also employed for data acquisition. Vegetables were sampled by dividing the farmland of each of the vegetable types in to three equal portions, and from each of the three portions, one sample was collected which was then put together with the other two samples as one. The samples were packed in zip-lock bags and kept at a cold temperature (− 20 ℃) before being transferred to the laboratory where they were thawed, homogenized and then subjected to extraction. The extract obtained was subjected to a clean-up process and then analyzed on a GC–MS instrument for pesticide detection and quantification.ResultsThe interview revealed number of years of farmers’ engagemrent in vegetable cultivation from one to ten, and identified four key vegetable varieties grown by the farmers: Capsicum annuum (pepper), Abelmoschus esculentus (okra), Solanum aethiopicum (garden egg) and Solanum lycopersicum (tomato). The data acquired gave identities or names of eight pesticides that are applied on the cultivated vegetables or farmlands by the farmers, and a decision on the vegetables selected for analysis in this study. Furthermore, the study revealed dichlorodiphenyltrichloroethane (DDT), k-optimal, lindane, and lambda-cyhalothrin to be among the pesticides in use, with DDT being a non-degradable, and the most widely applied pesticide. Notably, the DDT, lindane, and hexachlorocyclohexane, residues exceeded safety limits set by the European Commission in pepper, garden egg and okra. Unfortunately, banned pesticides such as heptachlor and aldrin were detected in the cultivated vegetables. More alarmingly, the commonly used DDT and lambda-cyhalothrin in the vegetable cultivation were found to hinder seed germination and seedling vigor in an investigation.ConclusionsThe DDT, lindane, and hexachlorocyclohexane, residues detected in the pepper, garden egg and okra samples that exceeded safety limits render these vegetables unsafe for human consumption. The banned heptachlor and aldrin detected in the vegetables indicate long-lasting environmental contamination. The commonly used DDT and lambda-cyhalothrin in the vegetable cultivation found to hinder seed germination and seedling vigor, indicate their non-degradability and substantial growth impediments. This present study therefore underscores the urgent need for enhanced safety measures and informs pesticide practices to safeguard both crops and public health in the district. We recommend further research be conducted to assess the potential health implications associated with the cultivation and consumption of vegetables in Navrongo, Ghana.

Simple Synthesis of Cellulose-Based Nanocomposites as SERS Substrates for In Situ Detection of Thiram.

There is a growing interest in the use of flexible substrates for label-free and in situ Surface-enhanced Raman Spectroscopy (SERS) applications. In this study, a flexible SERS substrate was prepared using self-assembled Au/Ti3C2 nanocomposites deposited on a cellulose (CS) paper. The Au/Ti3C2 nanocomposites uniformly wrapped around the cellulose fibers to provide a three-dimensional plasma SERS platform. The limit of detection (LOD) of CS/Au/Ti3C2 was as low as 10-9 M for 4-mercaptobenzoic acid(4-MBA) and crystal violet (CV), demonstrating good SERS sensitivity. CS/Au/Ti3C2 was used for in situ SERS detection of thiram on apple surfaces by simple swabbing, and a limit of detection of 0.05 ppm of thiram was achieved. The results showed that CS/Au/Ti3C2 is a flexible SERS substrate that can be used for the detection of thiram on apple surfaces. These results demonstrate that CS/Au/Ti3C2 can be used for the non-destructive, rapid and sensitive detection of pesticides on fruit surfaces.

Results from the Danish monitoring programme on pesticide residues from the period 2012–2017 – frequencies and trends in detected pesticides

In order to assess compliance with maximum residue levels in foods and evaluate the exposure of the Danish population to pesticides, a comprehensive monitoring programme was conducted. The work from 2012-2017 involved testing pesticide residues in fruits, vegetables, cereals, animal product and processed commodities. The sampling strategy, mainly based on exposure calculations and previous findings, involved the collection of 13,492 samples primarily from fresh conventional and organic produces on the Danish market. The origin of the samples varied, with 34% being of Danish origin and 67% originating from EU and non-EU countries. The results revealed that residues in conventionally grown produce were detected in 54% of the fruit and vegetable samples, and 30% of the cereal samples. Additionally, residues above the maximum residue limits were found in 1.8% of these samples, most frequently in fruits. As previous years, more residues were found in samples of foreign origin compared to samples of Danish origin. Compared to earlier findings more than 40 pesticides were detected for the first time and including boscalid, imidacloprid, thiacloprid, etofenprox, and spinosad, all detected more than 100 times. The data shows that detection of PFAS pesticides has increased dramatically, from 24 in 2006 to 412 in 2022.

All-in-One Electrokinetic Strategy Coupled with a Miniaturized Chip for SERS Detection of Multipesticides.

Complexed and tiresome pretreatment processes have significantly impeded in-field analysis of environmental specimens. Herein, an all-in-one sample separation and enrichment strategy based on a compact charge-selective capture/nanoconfined enrichment (CSC/NCE) device is exploited for marker-free surface-enhanced Raman spectroscopy (SERS) detection of charged pesticides in matrix specimens. This tactic incorporating in situ separations, seizing, and nanoconfined enhancement can greatly elevate the effectiveness of sample pretreatment. Importantly, CSC/NCE with excellent adsorption performances and excellent plasmonic features facilitates concentration and signal amplification of electrically charged pesticides. With the introduction of an electric field on this integrated CSC/NCE, the matrix effect in samples could be significantly eradicated, and a distinct SERS response is witnessed for targeted analytes. Accurate quantification of multipesticides is achieved by synergizing the CSC/NCE chip and chemometrics, and the contents found by the CSC/NCE-based sensing strategy agree with those obtained from chromatography assays with relative deviations lower than 10%. The facile and versatile all-in-one tactic infused in a compact chip exhibits enormous potential for field-test application in chemical measurement and food safety.

Superior oxidase-mimetic activity of FeCo-NC dual-atom nanozyme for smartphone-based visually colorimetric assay of organophosphorus pesticides.

A colorimetric analysis platformhas been successfully developedbased on FeCo-NC dual-atom nanozyme (FeCo-NC DAzyme) for the detection of organophosphorus pesticides (OPPs). The FeCo-NC DAzyme exhibited exceptional oxidase-like activity (OXD), enabling the catalysis of colorless TMB to form blue oxidized TMB (oxTMB) without the need for H2O2 involvement. By combining acid phosphatase (ACP) hydrolase with FeCo-NC DAzyme, a "FeCo-NC DAzyme + TMB + ACP + SAP" colorimetric system was constructed, which facilitated the rapid detection of malathion. Thechromogenic system was appliedto detect malathion using a smartphone-based app and an auxiliary imaging interferogram device for colorimetric measurements, which have a linear range of 0.05-4.0 µM and a limit of detection (LOD) as low as 15 nM in real samples, comparable to UV-Vis and HPLC-DAD detection methods. Overall, these findings present a novel approach for convenient, rapid, and on-site monitoring of OPPs.

Construction of phosphatase-like COF-OMe@Valine-CeO2 nanozymes for ultrasensitive electrochemical detection of organophosphorus pesticides

Construction of highly-active artificial nanozymes for pesticides detection has great significance of human health and ecological systems. Herein, we have successfully designed a two-step approach to synthesize the TAPB-DMTP-COF (hereafter denoted as COF-OMe, TAPB, 1,3,5-tris(4-aminophenyl)benzene; DMTP, 2,5-dimethoxyterephaldehyde; COF, covalent organic framework)@Valine integrated cerium oxide nanozymes (COF-OMe@Valine-CeO2) with phosphatase-like activities, which can cleave phosphate bonds (PO) of organophosphorus pesticides (OPs) for the formation of electroactive p-nitrophenol (p-NP). In detail, the Ce (IV)/Ce (III) species serve as the active sites to polarize and hydrolyze PO bond in OPs, and the excellent adsorption performance of porous COF-OMe toward OPs could promote the hydrolysis process of PO. Moreover, the efficient charge transfer at the covalent interface of COF-OMe@Valine-CeO2 also contributed to this excellent catalytic process. By virtue of those advantages, the COF-OMe@Valine-CeO2 electrochemical platform was successfully applied in methyl-paraoxon (MP) detection. The resulting electrochemical sensors displayed high sensitivity, a wide linear response range of 0.034–76 μmol/L, and low detection limits of 0.011 μmol/L for MP. The research not only provides a preparation method for COF with excellent nanozyme activity, but broadens some new insights for the design of highly efficient nanozymes for on-time detection for OPs.

Evaluating the effectiveness of different household washing techniques for removal of insecticides from spinach and chickpea leaves by micellar liquid chromatography

In the past few decades, the employment of green analytical approaches in chromatographic method development has attracted the analytical separation community. The greenness of the developed method depends upon the toxicity of solvents and the amount of generated post-analysis waste generated. In this concern, micellar liquid chromatography (MLC) is a simple and rapid technique that generates very low toxic waste compared to traditional chromatographic pesticide detection methods. Here, MLC method has been validated and applied for the determination of monocrotofos (MCF), imidacloprid (ICP), dimethoate (DM) and profenofos (PFF) in spinach and chickpea leaves. The optimized mobile phase was 0.065 M SDS-2 % 1-propanol, 0.01 M NaH2PO4 buffered to pH 7. A C18 column was used for separation with a flow rate of 1 mL/min. The developed method has been validated following the guidelines of SANTE/11,312/2021 and ICH guidelines for; limit of quantification (0.05–0.20 mg/kg), linearity (r2> 0.997–0.999), precision (<6.3 %), accuracy (96.3 %–99.8 %) and robustness (<6) in real samples. ICP and MCF, apart from DM and PFF, were detected in the present work. After detecting insecticides in spinach and chickpea leaves both were washed with different household chemicals i.e. normal, lukewarm, common salt, lemon juice water and commercial ozonizer. Based on five washing techniques with insecticide concentration time intervals reduction rates were calculated for each washing treatment. The results show that lemon juice, common salt water, and ozonizer can be used as washing techniques for the reduction of superficial and systematic residues of ICP and MCF. Common salt and lemon juice water were better for washing over vinegar and potassium permanganate (KMnO4) as they enhance the colour of the green leafy vegetables and are available in every Indian kitchen. They can be easily used by lower socioeconomic classes who cannot afford KMnO4 and vinegar.

Cauliflower-like super-hydrophobic SERS substrate via two-step laser processing for acetamiprid detection

Residues of organic pesticides continue to accumulate in the human body through the food chain, posing a serious threat to health. Therefore, the efficient and sensitive detection of pesticide residues is crucial. Surface-enhanced Raman scattering (SERS), as a powerful spectroscopic technique, holds great potential for the trace detection of pesticides. In this study, a cauliflower-like SERS substrate fabricated via a two-step laser processing is proposed for highly sensitive detection of acetamiprid. The cauliflower-like structure features a large surface area, providing numerous hotspots and abundant adsorption sites for the target molecules. Furthermore, the rich micro/nano structures on the surface confer super-hydrophobicity properties to the substrate, effectively enriching the analyte and greatly enhancing the SERS performance. As a result, the cauliflower-like super-hydrophobic substrate demonstrates a detection limit as 10-15 M for the typical dye analyte (R6G), with an enhancement factor of 2.6 × 108. Additionally, the substrate exhibits excellent signal reproducibility with a relative standard deviation of 8.33 %. In practical pesticide detection, the detection limit for acetamiprid on orange is 10-4 g/L, significantly surpassing the national standard. In conclusion, the cauliflower-like super-hydrophobic substrate enhances the sensitivity, uniformity, reproducibility, and reliability of SERS signals in detection process, showing tremendous potential in the field of food safety.

Au-Ag nano-garlands as a versatile SERS substrate: Two-step synthesis realizes the growth of petal-shaped branches on hollow Au-Ag nanoshells

In this work, we synthesized Au-Ag alloy nano-garlands with multiple petal-like branches and internal cavities in two steps. First, we etched silver nanospheres with HAuCl4 to obtain Au-Ag alloy nanoshells with different shell layer thicknesses and hollow core sizes. After that, based on different nanoshells, 4-NTP was used as a shape-directing agent, HAuCl4 and AgNO3 as precursor raw materials, and AA as a reducing agent for the growth of petals to form Au-Ag bimetallic nano-garlands with multi-branching structure. The regulation of the branching morphology of the nano-garlands could be achieved by changing the amounts of 4-NTP and HAuCl4. The SERS activity of the nano-garlands could be further improved by changing the AA concentration, the size of nanoshells, and the Au/Ag ratio of the precursor raw materials. Because the bimetallic nano-garlands have hollow cavities and petal-like branches, there are couplings between the cavities and the branches, between the adjacent branches, and between the metals inside and outside of the cores, which can achieve a good enhancement of SERS. The highest SERS enhancement factor of Au-Ag bimetallic nano-garlands can reach 4.47×108, which can be used as a good candidate for SERS substrate for the trace detection of biomolecules, pesticides, and other substances.

Automated identification of pesticide mixtures via machine learning analysis of TLC-SERS spectra

Identification of components in pesticide mixtures has been a major challenge in spectral analysis. In this paper, we assembled monolayer Ag nanoparticles on Thin-layer chromatography (TLC) plates to prepare TLC-Ag substrates with mixture separation and surface-enhanced Raman scattering (SERS) detection. Spectral scans were performed along the longitudinal direction of the TLC-Ag substrate to generate SERS spectra of all target analytes on the TLC plate. Convolutional neural network classification and spectral angle similarity machine learning algorithms were used to identify pesticide information from the TLC-SERS spectra. It was shown that the proposed automated spectral analysis method successfully classified five categories, including four pesticides (thiram, triadimefon, benzimidazole, thiamethoxam) as well as a blank TLC-Ag data control. The location of each pesticide on the TLC plate was determined by the intersection of the information curves of the two algorithms with 100 % accuracy. Therefore, this method is expected to help regulators understand the residues of mixed pesticides in agricultural products and reduce the potential risk of agricultural products to human health and the environment.

Endosulfan pesticide detection using an electrochemical sensor based on molecularly imprinted polymer (MIP)

Abstract Pesticides and herbicides are active chemicals used to eradicate plant pests which constitute contamination if they exceed the threshold for the environment and humans. Molecularly Imprinted Polymer (MIP) is a technique for making polymers that are obtained from cross-linked polymers and have cavities that match the template, where the cavities function as a medium for mechanical interaction of molecules with the same size, shape, structure, and physicochemical properties. The polymer produced from the MIP technique is applied to the surface of the sensor material as an endosulfan detection. This research aims to create an endosulfan MIP to obtain a potentiometric MIP sensor capable of detecting endosulfan. The results showed that the optimum conditions for making MIP endosulfan were obtained with a composition of 6.02 mL of chloroform; 0.025 g endosulfan; 0.9 mL methacrylic acid (MAA); 1.57 mL ethylene glycol dimethacrylate acid (EGDMA); 0.07 g benzoyl peroxide with a heating time of 150 minutes at a temperature of 70 °C. The sensor performance test was carried out potentiometrically and it was found that the MIP endosulfan sensor that was made had sensitivity and stability in the concentration range of 0.01-1.0x10−6 ppm with a lifetime up to 90 days.