Pesticides Methomyl Research Articles

Pesticide residues in traditional and industrial honey marketed in Morocco and potential health risk

ABSTRACT This study evaluated the presence of the three pesticides methomyl (MET), carbendazim (CBZ) and chlorpyrifos-ethyl (CPE), as well as the degradation product of CPE (3,5,6-trichloro-2-pyridinol; TCP), in 44 honey samples from all 12 regions of Morocco. With a validated HPLC-UV method occurrence frequencies of 63.6% for MET, 54.5% for CBZ, 95.1% for CPE and 34.1% for TCP were obtained, even at concentrations higher than the maximum residue limits for MET, CPE and TCP. Based on the predominant pesticide, principal component analysis separated sampling regions into three groups. Risk assessment indicated that ingestion of these pesticides, alone or in combination, in honey did not pose a risk to consumers (HQ and HI < 1).

Environmental fate of methomyl pesticide in river water: Kinetic study, mathematical simulations and risk assessment

Methomyl (MET) is a pesticide widely used as an acaricide with toxic effects on aquatic organisms and humans. The environmental persistence of pollutants can be determined by different routes, including photochemical transformations driven by sunlight and photoproduced reactive intermediates such as HO•, 3CDOM* , and 1O2. Photolytic experiments were carried out under simulated solar radiation, revealing a low value of the direct photolysis quantum yield, ΦMET = (2.01 ± 0.62) × 10−4 mol Einstein−1. The second-order kinetic rate constants of the reactions between MET and HO•, 3CDOM* , and 1O2 were also measured using the competition kinetics approach; the values obtained were kMET, HO• = (1.42 ± 0.04) × 109 L mol−1 s−1, kMET,3CBBP* = (3.49 ± 0.87) × 108 L mol−1 s−1 and kMET, 1O2 = (3.36 ± 1.09) × 104 L mol−1 s−1, respectively. Kinetic mathematical simulations were used to predict the half-life and self-purification distance of MET in a river, considering phenomena as photodegradation, adsorption, biodegradation, geographical location, and water chemistry. The half-life of MET was estimated to be 82 h, with biodegradation making the largest contribution to the drop in MET concentration. The relative contribution of photochemical pathways to MET degradation in sunlit water will depend greatly on the irradiance conditions, water depth and the environmental characteristics of the water body, including the concentrations of organic matter, nitrate, nitrate and carbonate. Finally, the predicted risk coefficients, also based on QSAR models, confirmed that MET and its metabolite S-methyl-N-hydroxythioacetamidate pose a high risk to aquatic species.

Comparative study of green formulated nano-adsorbent based biopolymers and carbon activated with metal nanoparticles

Pesticide residue in agricultural wastewater is a concerning issue due to its potential impact on the environment and human health. While they can be effective in enhancing crop yields and quality, their improper use and disposal can lead to the contamination of water sources. Methomyl is a carbamate insecticide that has been conventionally used in agriculture to control a wide range of insect pests. In this study, adsorbents were formulated based on the combination of cellulose triacetate, activated carbon, ethylcellulose and different nanometals (AgNPs, ZnONPs, CuONPs and Al2O3NPs) to compare the efficiency of nanoparticles in such pesticide residue. The formulated adsorbents were characterized using ATR-FTIR, SEM and EDX before and after adsorption to evaluate the mechanism of adsorption. The presence of different functional groups on the prepared bio-adsorbents showed a great opportunity to capture the methomyl pesticide from wastewater. The maximum adsorption capacities were 85, 143, 175, 199 and 250 mg/g for EC/CTA/AC, EC/CTA/AC/Ag, EC/CTA/AC/Zn, EC/CTA/AC/Cu, and EC/CTA/AC/Al, respectively. The antimicrobial activity of prepared adsorbents was carried out. It showed a broad spectrum antimicrobial activity as well as good antifungal properties. The presence of Al2O3NPs was detected as a broad spectrum for both bacteria and fungi.

Removal of Pesticide Residues in Aqueous Solution by Adsorption Using Pineapple Peel Activated Carbon

The use of synthetic pesticides in crop protection generates dilute pesticide solution resulting from the cleaning of pesticide application equipment, also known as pesticide rinsate. If not disposed or treated properly, this may result to the contamination of surface water or groundwater. One of the possible management practices for pesticide rinsate is the use of activated carbon as an adsorbent. Activated carbon was prepared from pineapple peel using phosphoric acid through chemical activation. Characterization of the surface morphology through Scanning Electron Microscopy (SEM) confirmed the successful activation of the carbon. The resulting Pineapple Peel Activated Carbon (PPAC) was utilized as adsorbent in the removal of the carbamate methomyl in the pesticide rinsate. Analysis of the cleaned rinsate using a High-Performance Liquid Chromatograph confirmed the removal of 96.0-98.4% of methomyl residues in a 7.5 mg L-1 methomyl pesticide rinsate using a 0.5-1.0% w/v PPAC:rinsate ratio. This study showed that activated carbon could be successfully prepared from pineapple peel and used as an effective adsorbent for the remediation of pesticide rinsate to prevent the pollution of surface water or groundwater.

Effect of environmental level of methomyl on hatching, morphology, immunity and development related genes expression in zebrafish (Danio rerio) embryo

The extensive use of carbamate pesticides has led to a range of environmental and health problems, such as surface and groundwater contamination, and endocrine disorders in organisms. In this study, we focused on examining the effects of toxic exposure to the carbamate pesticide methomyl on the hatching, morphology, immunity and developmental gene expression levels in zebrafish embryos. Four concentrations of methomyl (0, 2, 20, and 200 μg/L) were administered to zebrafish embryos for a period of 96 h. The study found that exposure to methomyl accelerated the hatching process of zebrafish embryos, with the strongest effect recorded at the concentration of 2 μg/L. Methomyl exposure also trigged significantly reductions in heart rate and caused abnormalities in larvae morphology, and it also stimulated the synthesis and release of several inflammatory factors such as IL-1β, IL-6, TNF-α and INF-α, lowered the IgM contents, ultimately enhancing inflammatory response and interfering with immune function. All of these showed the significant effects on exposure time, concentration and their interaction (Time × Concentration). Furthermore, the body length of zebrafish exposed to methomyl for 96 h was significantly shorter, particularly at higher concentrations (200 μg/L). Methomyl also affected the expression levels of genes associated with development (down-regulated igf1, bmp2b, vasa, dazl and piwi genes), demonstrating strong developmental toxicity and disruption of the endocrine system, with the most observed at the concentration of 200 μg/L and 96 h exposure to methomyl. The results of this study provide valuable reference information on the potential damage of methomyl concentrations in the environment on fish embryo development, while also supplementing present research on the immunotoxicity of methomyl.

Human Poisoning with Methomyl and Cypermethrin Pesticide Mixture.

There is limited literature analyzing the outcome of human poisoning with methomyl and cypermethrin pesticide mixture. Between 2002 and 2018, a total of 63 patients intoxicated with methomyl, cypermethrin, or their pesticide mixture were treated at Chang Gung Memorial Hospital. The patients were categorized into three groups based on the type of pesticide, as methomyl (n = 10), cypermethrin (n = 31), or methomyl and cypermethrin (n = 22). Demographic, clinical, laboratory, and mortality data were obtained for analysis. The patients were aged 54.9 ± 18.9 years. Following ingestion, the patients experienced a wide range of clinical symptoms, including aspiration pneumonia (50.8%), acute respiratory failure (41.3%), acute kidney injury (33.3%), multiple organ failure (19.0%), emesis (19.0%), acute hepatitis (12.7%), diarrhea (7.9%), seizures (4.8%), lacrimation (4.8%), etc. After analysis, it was found that patients with methomyl and cypermethrin poisoning suffered higher incidences of acute respiratory failure (p < 0.001), aspiration pneumonia (p = 0.004), acute kidney injury (p = 0.011), and multiple organ failure (p < 0.001) than the other groups. Laboratory analyses revealed that patients with methomyl and cypermethrin poisoning had a higher creatinine level (p = 0.011), white blood cell count (p < 0.001), and neutrophil count (p = 0.019) than the other groups. A total of seven (11.1%) patients died. The average duration of hospitalization was 9.8 ± 10.0 days. In a multivariate logistic regression model, it was revealed that methomyl pesticide (p = 0.045) or methomyl and cypermethrin pesticide mixture (p = 0.013) were significant risk factors for acute respiratory failure. Nevertheless, no mortality risk factor could be identified. Therefore, the analytical results suggest that methomyl pesticide is the major contributor to the toxicity of methomyl and cypermethrin pesticide mixture poisoning. More research is needed.

Investigation on the adsorption of the carbamate pesticide methomyl from aqueous solution using modified co-beta zeolite particles

Adsorption of carbamate pesticide Methomyl by Co-Beta Zeolite particles prepared by wet ion-exchange method from aqueous solutions was studied. The effect of zeolite and pesticide concentrations, pH value, and sintering temperature on pesticide removal from an aqueous solution was studied. The change of methomyl concentration during the adsorption was followed using the UV-Visible spectrophotometer. Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS) revealed the modified zeolite morphology and elemental structure. The change of the adsorbent surface before and after dye removal was observed using the Fourier Transformation-infrared spectroscopy (FT-IR). The adsorption kinetics follows the pseudo-second-order kinetics model, and at optimal condition adsorption rate is k1 = 0.0166 g mg-1 min-1. The Langmuir, Freundlich, Temkin and Dubinin-Radushkovich adsorption isotherm models were used to describe the adsorption process. Thermodynamic parameters were also determined using experimental data. The thermodynamic study indicates that during pesticide adsorption is, chemisorption and physisorption are present at the same.

Methomyl, imbraclaobrid and clethodim induced cytomixis and syncytes behaviors in PMCs of Pisum sativum L: Causes and outcomes

Cytomixis is a common phenomenon observed in meiotic cells such as anther which is influenced by various factors. Use of pesticides is a common practice in agriculture. However, it is not known whether pesticides can induce cytomixis in plant cells and induce genetic variation. To understand this, the present study was planned to assess the cytomixis and syncytes behaviors in PMCs of Pisum sativum L. Seeds of P. sativum (Family: Fabaceae) were treated with different concentrations of commonly used pesticides methomyl (ME), imbraclaobrid (IM) and clethodim (CL). Seeds were treated with various concentrations (0.1, 0.2, 0.3, 0.4 and 0.5% of ME, IM and CL prepared in water) for 1 and 3 h. Effect of pesticides on pollen fertility, frequency of cytomixis, and kind of cytomixis cells was assessed. In the cytomixis cells, the cytomictic channel (CC) and direct fusion (DF), and various stages of meiosis (PI, MI, AI and TI) with cytomixis cells were observed. In addition, frequency of syncytes cell and their various stages of meiosis I (PI, MI, AI and TI) in pollen mother cells (PMCs) was assessed. During the microsporogenesis in P. sativum, the occurrence of cytomixis and syncytes at various stages of meiosis I were seen. The formation of cytoplasmic channels and direct fusing of pollen mother cells (PMCs) were both seen to cause cytomixis, with the former being more common than the latter. The percentage of PMCs with cytomixis and syncytes cells increased with increase in the concentration of pesticides. The result of the present investigation indicates that commonly used pesticides ME, IM, and CL have a significant effect on pollen fertility, frequency of cytomixis, and kind of cytomixis cells, the cytomictic channel (CC) and direct fusion (DF), in addition, frequency of syncytes cell and their various stages of meiosis I (PI, MI, AI and TI) in pollen mother cells (PMCs) on P. sativum.

Smartphone-coupled three-layered paper-based microfluidic chips demonstrating stereoscopic capillary-driven fluid transport towards colorimetric detection of pesticides.

The existence of pesticide residues in the hydrosphere, biosphere, and anthroposphere can cause acute or chronic diseases and deteriorate the environment. Therefore, efficient detection of pesticide residues is of great significance to prevent food poisoning, control food pollution, and protect human lives by recognizing their distribution and concentration. Herein, a novel smartphone-coupled three-layered paper-based microfluidic chip is proposed as a facile platform to detect the pesticides. The stereoscopic capillary-driven fluid transport is enabled by the three-layered microfluidic chip configuration. The detection mechanism is based on the enzyme inhibition reaction and the chromatic reaction. The detection results are obtained by a smartphone and figured out by colorimetric quantitative analysis. Taking advantages of the above merits, we demonstrate the utilization of this smartphone-coupled three-layered paper-based microfluidic chip for the effective analysis of typical pesticides (profenofo and methomyl). The linear ranges of profenofo and methomyl are 0.27-2.1μmol L-1 and 0.14-1.85μmol L-1, respectively. The corresponding limits of detection in the chips are 55nM and 34nM, respectively. The paper-based chips are also highly cost-effective with a total cost of 0.082 ¥ per piece. It can be anticipated that this technique will open new avenues for the mass fabrication of paper-based microfluidic chips and provide state-of-the-art methods in the field of analytical chemistry.

Postmortem sampling time effect on toxicity biomarkers in rats exposed to an acute lethal methomyl dose

Regulations often are imposing long postmortem times before autopsy leading to certain toxicity-unrelated changes in biomarkers, which in turn may affect the reliability of toxicity evaluation during forensic investigations. Since methomyl pesticide shows significant toxicity and is frequently encountered in poisoning cases, the current study evaluated different parameters in methomyl intoxicated rats at three different postmortem intervals (Hour 0, Hour 3 and Hour 6). Eighteen adult Sprague Dawley rats were poisoned with methomyl to simulate actual methomyl poisoning cases. The time of death was assigned as Hour 0. The animals were divided into 3 groups (n = 6) to collect blood and tissue samples at the selected time points. Body weight, relative organ weight, protein concentration, methomyl concentration and acetylcholinesterase activity (AChE) were assessed in blood and different tissues (liver, spleen, kidney, brain, eye, and bone marrow) to evaluate the effect of postmortem sampling time. Outcomes revealed significant decreases in methomyl concentration in blood and bone marrow with advanced sampling time (P < 0.001). Similarly, there were significant reductions in AChE activity in the kidney (P < 0.01), while the enzyme activity significantly increased in brain samples (P < 0.05). Findings illustrated the importance of sampling time in toxicity studies because it could alter experimental results and impact consequent interpretations, as well as it may alter postmortem biomarkers in related forensic cases.

Acute and Chronic Effects of Clothianidin, Thiamethoxam and Methomyl on Chironomus dilutus

Organism tolerance thresholds for emerging contaminants are vital to the development of water quality criteria. Acute (96-h) and chronic (10-day) effects thresholds for neonicotinoid pesticides clothianidin and thiamethoxam, and the carbamate pesticide methomyl were developed for the midge Chironomus dilutus to support criteria development using the UC Davis Method. Median lethal concentrations (LC50s) were calculated for acute and chronic exposures, and the 25% inhibition concentrations (IC25) were calculated for the chronic exposures based on confirmed chemical concentrations. Clothianidin effect concentrations were 4.89 µg/L, 2.11 µg/L and 1.15 µg/L for 96-h LC50, 10-day LC50 and 10-day IC25, respectively. Similarly, thiamethoxam concentrations were 56.4 µg/L, 32.3 µg/L and 19.6 µg/L, and methomyl concentrations were 244 µg/L, 266 µg/L and 92.1 µg/L. Neonicotinoid effect concentrations compared favorably to previously published 96-h and 14-day LC50 concentrations, and methomyl effect concentrations were within the acute survival range reported for Chironomus species and other organisms.

Response of Sex Steroid Hormone Synthesis Substrates in Serum and Testes of Male Tilapia (Oreochromis niloticus) Exposed to Methomyl and Its Recovery Pattern

The response of synthetic substrates of sex steroid hormones—cholesterol (CHO), pregnenolone (PREG), and progesterone (PROG)—in the serum and testes of male tilapia (Oreochromis niloticus) to the environmental estrogen pesticide methomyl (0.2, 2, 20, and 200 μg·L−1) was evaluated using static-water contact toxicity tests. The results showed that low methomyl concentrations (0.2 and 2 μg·L−1) had no significant effects on the contents of CHO, PREG, and PROG in the serum and testes of male tilapia (p &gt; 0.05). Consequently, the concentration of 2 μg·L−1 could be used as a preliminary reference threshold for the non-effective dose of methomyl in male tilapia. Exposure to high methomyl concentrations (20 and 200 μg·L−1) significantly inhibited the levels of CHO, PREG, and PROG in the serum and testes of male tilapia (p &lt; 0.05) and showed a dose–response relationship. Sex steroid hormone synthesis substrate damage to male tilapia caused by less than 20 μg·L−1 methomyl was reversible, while the damage caused by equal to or greater than 200 μg·L−1 methomyl was irreversible when tilapia were transferred to methomyl-free water for 18 days. Thus, a concentration of 200 μg·L−1 could be used as a reference threshold for irreversible damage caused by methomyl in male tilapia.

Pesticide residues in tomato crops in Western Algeria

ABSTRACT This study aimed to evaluate levels of pesticide residues commonly used on tomato crops in Western Algeria. It showed a significant use of pesticides, especially insecticides (47%) and fungicides (41%) among listed pesticides in crop fields. A total of 30 tomato samples were analysed using multi-residue analysis by liquid chromatography-tandem mass spectrometry (LC-MS/MS) after QuEChERS extraction. Five pesticides (difenoconazole, triadimenol, metalaxyl, chlorpyriphos and methomyl) were detected in 14 samples (47%). Among these five samples containing residues of two different types of pesticides. The levels ranged from 2.29 to 64.3 µg/kg. The methomyl residue in one sample was above the maximum limit (MRLs) set by the European Union. Our results indicate an excessive use of pesticides and undeniable non-compliance with good agricultural practices. Routine monitoring for pesticides is recommended to preserve consumer’s health.

Assessment of pesticide residues, exogenous heavy metals and essential minerals in spinach after cleaning with traditional methodologies

ABSTRACT Green leafy vegetables are a rich source of micronutrients but can usually contain contaminants such as pesticides and toxic heavy metals. In this work, we have evaluated the effectiveness of washing with tap water, vinegar-acidified water and basified water with sodium bicarbonate in eliminating three pesticides (methomyl, deltamethrin and lambda-cyhalothrin) and some exogenous heavy metals. The HPLC-UV method was validated for pesticides analysis in vegetable matrices using the QuEChERS method extraction. The results showed that a ca. of 57 to 71% and 73 to 97% of the 3 pesticides are removed after washing with acidified and basified water, respectively. On the other hand, the ICP-MS method was used for analysing heavy metals and essentials elements in spinach. Washing with both acidic and alkaline water removed a part of toxic heavy metals. The decrease in metals concentrations indicated that, probably, the metals contamination of vegetables was mainly through the foliar deposition. Acidified and basified water solubilise small particles containing these exogenous metals In conclusion, the performance of washing with the basic medium was better to remove pesticides and some of exogenous toxic heavy metals from the surfaces of spinach leaves and to preserve the essential elements of the plant.

Toxicological Impacts of Some Compounds on Massylaea vermiculata (O.F. Müller 1774), (Gastropoda: Helicidae) Under Laboratory Conditions.

&lt;b&gt;Background and Objective:&lt;/b&gt; Effect of some compounds such as Plant extracts (Techno oil and Berna Star), natural origin compounds (Top-nine, Repcar and Chitosan 5%) and classical chemical pesticides (methomyl and lambda-cyhalothrin) were studied against the terrestrial snail &lt;i&gt;Massylaea vertmiculata&lt;/i&gt; using the bait technique. Material and Methods: LC&lt;sub&gt;50&lt;/sub&gt; of the each tested compound of natural compounds were estimated after 14 days of treatment, while LC&lt;sub&gt;50&lt;/sub&gt; of pesticide were evaluated after 72 hrs of treatment. The impact of LC&lt;sub&gt;50 &lt;/sub&gt;of each tested compound on some biochemical parameters, total protein content, alkaline phosphatase (ALP) and acid phosphatase (ACP) activity were determined 48 hrs post treatment. &lt;b&gt;Results:&lt;/b&gt; The results revealed that the methomyl and lambda-cyhalothrin were the most effective compounds against test land snails, followed by Repcar, Top-nine and Techno oil, while Berna Star and Nema Ultra Chem come in the last rank. The pesticide compound methomyl was the most toxic one against the tested terrestrial snail species, while the Chitosan 5% was the least toxic one. The results showed that all tested compounds caused fluctuated effect whether increasing or decreasing on all the studies parameters such as total protein content, ALP and ACP activity as well. However, the Techno oil and the Berna Star caused sever decreasing on total protein content and ACP, followed by Top-nine, Repcar, Chitosan 5% (Nema Ultra Chem) and plant extracts. &lt;b&gt;Conclusion:&lt;/b&gt; The both tested natural compounds and plant extracts recorded satisfying results compared with methomyl and lambda-cyhalothrin effect and that can be used in the pest controlling programs against terrestrial snails to reduce the environmental pollution.

Removal of the pesticide methomyl contained in simulated effluent from equipment washing by adsorption in residual orange bagasse

This work consists of the study of methomyl removal, an extremely toxic carbamate pesticide, contained in aqueous solutions synthesized, by adsorption in residual orange bagasse from industrial juices processing. The adsorption kinetics was studied by obtaining the best fit for the model of pseudo-second order (R2= 0.949). The Langmuir isotherm model adjusted better to the experimental data confirming the adsorption in monolayers, without interaction among the adsorbate molecules. The scanning electron microscopy (SEM) revealed that particulate adsorbents have rather irregular surface, but with rigid structure and virtually no internal pores. The characterization of the functional groups by infrared spectroscopy (FTIR) revealed the presence of hydroxyl, Carbonyl and carboxylic groups on the adsorbents particles surface. Central composite rotational design 2x2 (DCCR 2x2) was used for the statistical study of the effects of pH and solid/liquid ratio (R) on the methomyl adsorption capacity in orange bagasse particles. The obtained mathematical model adjusted well to the experimental data (R2= 95%). In the studied intervals the highest values of adsorption capacity (q) were 3.73 and 3.43 (mg.g-1), obtained under the conditions of pH 6.0 with R 0.017 g.mL-1 and pH 4.5 with R 0.015 g.mL-1, respectively. Thus, it was possible to conclude that there was a greater adsorption in assays containing greater adsorbent mass in pH slightly acid.

Determination of Methomyl Residues in Bohe by Ultrahigh-Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS).

The aim of this work is to investigate the presence of methomyl pesticide residue and the rate of disappearance in mint cultivated in the aquaponics system based on the application of UPLC-MS to establish a safety time interval before crop harvesting. Results showed that an effective and sensitive method based on UPLC-MS has been used for the determination of methomyl pesticide residues in mint. The initial residue level was much higher in roots (79.52 μg/kg), and it can be decreased to 16.73 (after 15 days) μg/kg and 3.31 (20 days) μg/kg, while the least was detected on the mix leaves and stems (44.54 μg/kg), and it can be decreased to 15.35 (after 20 days). In our case, we suggest that a safety interval in the range of 15–20 days should be allowed after the detection of methomyl in water, and the concentration of methomyl was lower than the acceptable daily intake (ADI) of the China Food and Drug Administration (CFDA) (20 μg/kg).

Selective Detection of Methomyl Pesticide by a Catalytic Chemosensing Assay

The catalytic chemosensing assay (CCA), a new indicator displacement assay, was developed for selective detection of methomyl, a highly toxic pesticide. Trimetallic complex {[FeII (dmbpy)(CN)4 ]-[PtII (DMSO)Cl]2 -[RuII (bpy)2 (CN)2 ]} (1; dmbpy=4,4'-dimethyl-2,2'-bipyridine, bpy=2,2'-bipyridine) was synthesized as a task-specific catalyst to initially reduce and degrade methomyl to CH3 SH/CH3 NH2 /CH3 CN/CO2 . The thus-produced CH3 SH interacts with the trimetallic complex to displace the cis-[RuII (bpy)2 (CN)2 ] luminophore for monitoring. Other pesticides, including organophosphates and similar carbamate pesticides, remained intact under the same catalytic conditions; a selective sensing signal is only activated when 1 recognizes methomyl. Furthermore, 1 can be applied to detect methomyl in real water samples. In the luminescent mode of the assay, the method detection limit (MDL) of 1 for methomyl (LD50 =17 mg kg-1 ) was 1.12 mg L-1 .

Photodegradation and Box-Behnken design optimization for methomyl using Fenton process based on synthesized CuO nanocrystals via facile wet chemical technique

Nanocrystals of copper oxide (n-CuO) were synthesized using a simple cost-efficient wet chemical procedure and characterized via X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). The n-CuO produced was used as a reagent of Fenton reaction for the mineralization of carbamate methomyl pesticide in aqueous solution. The system parameters were examined with the objective of optimization using a Box-Behnken design (BBD). A mathematical model of the treatment process was developed, with a good regression coefficient (R2 = 99.7) for a removal efficiency of 99%, with a 15-min reaction time. Analysis of the experimental data suggested that the reaction kinetics were best described by a second-order reaction model. The thermodynamic parameters calculated suggested that the non-spontaneous nature of oxidation at high temperature which was corroborated by positive ΔG’ and negative ΔS’ values. Also, the positive ΔH’ values indicated that the reaction was exothermic. The low activation energy (37.7 kJ/mol) indicated the reaction proceeds at a low energy level.

Silver nanoparticle/bacterial nanocellulose paper composites for paste-and-read SERS detection of pesticides on fruit surfaces

This study aimed to develop an eco-friendly flexible surface-enhanced Raman scattering (SERS) substrate for in-situ detection of pesticides using biodegradable bacterial nanocellulose (BNC). Plasmonic silver nanoparticle- bacterial nanocellulose paper (AgNP-BNCP) composites were prepared by vacuum-assisted filtration. After loading AgNPs into BNC hydrogel, AgNPs were trapped firmly in the network of nanofibrous BNCP upon ambient drying process, resulting in 3D SERS hotspots within a few-micron depth on the substrate. The fabricated AgNP-BNCPs exhibited high SERS activity with good reproducibility and stability as demonstrated by the detection of 4-aminothiophenol and methomyl pesticide. Due to the optical transparency of BNCP, a direct and rapid detection of methomyl on fruit peels using AgNP-BNCPs can be achieved, demonstrating a simple and effective ‘paste-and-read’ SERS approach. These results demonstrate potential of AgNP-BNCP composites for user-friendly in-situ SERS analysis.