Rapid detection of five pesticide residues using complexes of gold nanoparticle and porphyrin combined with ultraviolet visible spectrum

Color and fluorescence orthogonal dual-functional visual turn-on sensing for acidic and alkaline glyphosate and additive

In this work, benefitting from the sensitive pH-responsiveness of both meso-tetra-(4-sulfonatophenyl) porphyrin (TPPS4) and calixpyridinium, and their controllable strong noncovalent interactions, the first orthogonal dual-functional visual sensor for simultaneously and separately detecting acidic and alkaline substances without interference by using UV-Vis absorption and fluorescence emission spectra with both "turn on" signal changes was constructed by the supramolecular assembly of calixpyridinium with TPPS4. Color and fluorescence orthogonal dual-functional visual "turn-on" sensing for acidic and alkaline glyphosate and additive by calixpyridinium-TPPS4 sensor was further practically applied. The preparation of this sensor is quite simple in an environmentally friendly water medium. Only 2 μM calixpyridinium and 3 μM TPPS4 are needed to construct this assembly sensor. This sensor has a good biocompatibility, a high selectivity and sensitivity. Moreover, calixpyridinium-TPPS4 sensor can also be applied as a thermal switch and a light controlled anti-counterfeit material.

Research Status in the Use of Surface-Enhanced Raman Scattering (SERS) to Detect Pesticide Residues in Foods and Plant-Derived Chinese Herbal Medicines

Surface-enhanced Raman scattering (SERS) technology has unique advantages in the rapid detection of pesticides in plant-derived foods, leading to reduced detection limits and increased accuracy. Plant-derived Chinese herbal medicines have similar sources to plant-derived foods; however, due to the rough surfaces and complex compositions of herbal medicines, the detection of pesticide residues in this context continues to rely heavily on traditional methods, which are time consuming and laborious and are unable to meet market demands for portability. The application of flexible nanomaterials and SERS technology in this realm would allow rapid and accurate detection in a portable format. Therefore, in this review, we summarize the underlying principles and characteristics of SERS technology, with particular focus on applications of SERS for the analysis of pesticide residues in agricultural products. This paper summarizes recent research progress in the field from three main directions: sample pretreatment, SERS substrates, and data processing. The prospects and limitations of SERS technology are also discussed, in order to provide theoretical support for rapid detection of pesticide residues in Chinese herbal medicines.

Gold Nanoparticles-Based Colorimetric Assays for Environmental Monitoring and Food Safety Evaluation

Recent years have witnessed an exponential increase in the research on gold nanoparticles (AuNPs)-based colorimetric sensors to revolutionize point-of-use sensing devices. Hence, this review is compiled focused on current progress in the design and performance parameters of AuNPs-based sensors. The review begins with the characteristics of AuNPs, followed by a brief explanation of synthesis and functionalization methods. Then, the mechanisms of AuNPs-based sensors are comprehensively explained in two broad categories based on the surface plasmon resonance (SPR) characteristics of AuNPs and their peroxidase-like catalytic properties (nanozyme). SPR-based colorimetric sensors further categorize into aggregation, anti-aggregation, etching, growth-mediated, and accumulation-based methods depending on their sensing mechanisms. On the other hand, peroxidase activity-based colorimetric sensors are divided into two methods based on the expression or inhibition of peroxidase-like activity. Next, the analytes in environmental and food samples are classified as inorganic, organic, and biological pollutants, and recent progress in detection of these analytes are reviewed in detail. Finally, conclusions are provided, and future directions are highlighted. Improving the sensitivity, reproducibility, multiplexing capabilities, and cost-effectiveness for colorimetric detection of various analytes in environment and food matrices will have significant impact on fast testing of hazardous substances, hence reducing the pollution load in environment as well as rendering food contamination to ensure food safety.

Copper-Modified Double-Emission Carbon Dots for Rapid Detection of Thiophanate Methyl in Food

The detection of food safety and quality is very significant throughout the food supply. Stable dual-emission copper-modified fluorescent carbon dots (Cu-CDs) were successfully synthesized by a simple and environment-friendly hydrothermal, which was used for the real-time detection of pesticide residues in agricultural products. By optimizing the reaction conditions, Cu-CDs showed two emission peaks, with the highest fluorescence intensities at 375 and 450 nm. The structure, chemical composition and optical properties of Cu-CDs were investigated by XRD, TEM and IR. The results showed that thiophanate methyl (TM) could induce fluorescence quenching of Cu-CDs with no other ligands by the electron transfer through π-π stacking. The synchronous response of the dual-emission sensor enhanced the specificity of TM, which showed remarkable anti-interference capability. The fluorescence quenching degree of Cu-CDs had a good linear relationship with the TM concentration; the low detection limit for a pear was 0.75 μM, and for an apple, 0.78 μM. The recoveries in the fruit samples were 79.70–91.15% and 81.20–93.55%, respectively, and the relative standard deviations (RSDs) were less than 4.23% for the pear and less than 3.78% for the apple. Thus, our results indicate the feasibility and reliability of our methods in detecting pesticide residues in agricultural products.

Colorimetric assay based on peroxidase-like activity of dodecyl trimethylammonium bromide-tetramethyl zinc (4-pyridinyl) porphyrin for detection of organophosphorus pesticides

A simple and sensitive colorimetric assay for detecting organophosphorus pesticides (OPs) was developed based on 3,3',5,5'-tetramethylbenzidine (TMB)/hydrogen peroxide (H₂O₂)/dodecyl trimethylammonium bromide (DTAB)-tetramethyl zinc (4-pyridinyl) porphyrin (ZnTPyP). In this system, based on the peroxidase-like activity of DTAB-ZnTPyP, H₂O₂ decomposes to produce hydroxyl radicals, which oxidize TMB, resulting in blue oxidation products. The OPs (trichlorfon, dichlorvos, and thimet) were first combined with DTAB-ZnTPyP through electrostatic interactions. The OPs caused a decrease in the peroxidase-like activity of DTAB-ZnTPyP due to spatial site blocking. At the same time, π-interactions occurred between them, and these interactions also inhibited the oxidation of TMB (652 nm), thus making the detection of OPs possible. The limits of detection for trichlorfon, dichlorvos, and thimet were 0.25, 1.02, and 0.66 μg/L, respectively, and the corresponding linear ranges were 1-35, 5-45, and 1-40 μg/L, respectively. Moreover, the assay was successfully used to determine OPs in cabbage, apple, soil, and traditional Chinese medicine samples (the recovery ratios were 91.8-109.8%), showing a great promising potential for detecting OPs also in other complex samples.

Sensitive detection of ferbam by coupling solid phase microextraction with surface enhanced Raman spectroscopy based on Au nano-glass capillary

In this study, we developed an innovative approach that combines solid phase microextraction (SPME) with surface-enhanced Raman spectroscopy (SERS) to detect pesticide ferbam rapidly. An Au nano-glass capillary was fabricated by coating template-freely synthesized three-dimensional network Au nanostructures (3D-NW AuNSs) on the roughened surface of glass capillary and used for SPME and SERS respectively. Significant Raman signals were obtained by the SPME-SERS method, followed by detection of ferbam in water and orange juice samples with only 1 min SPME process. Results showed that Au nano-glass capillaries could achieve the detection of ferbam with limit of detection of 0.05 μg/L, and coefficient of determination (R²) of 0.9913. The recovery of predicted results was in the range of 88.46-103.29% and the relative standard deviation (RSD) was 3.5-8.2%. This study demonstrated potential capability of the SPME-SERS method for rapid (within 1 min) and sensitive detection of organic compounds in complex matrices. The SERS-active Au nano-glass capillary is easy to carry and operate, and is expected to play a role in the detection of trace pollutants.

Stability Studies of Magnetite Nanoparticles in Environmental Solutions

In the presented paper, studies of magnetite nanoparticle stability in selected environmental solutions are reported. The durability tests were performed in four types of liquids: treated and untreated wastewater, river water, and commercial milk (0.5% fat). Nanoparticles before and after deposition in the testing conditions were measured by transmission electron microscopy, X-ray diffraction, infrared spectroscopy, and Mössbauer spectroscopy. The amount of Fe atoms transferred into the solutions was estimated on the basis of flame atomic absorption spectroscopy. The analysis of the obtained results shows good stability of the tested nanoparticles in all water solutions. They do not change their structure or magnetic properties significantly, which makes them a good candidate to be used as, for example, detectors of specific compounds or heavy metals. On the other hand, studies show that particles are stable in environmental conditions for a long period of time in an unchanged form, which can cause their accumulation; therefore, they may be hazardous to living organisms.

Identification of a new Talaromyces strain DYM25 isolated from the Yap Trench as a biocontrol agent against Fusarium wilt of cucumber

Fusarium equiseti is a pathogenic fungus of plant root rot, and there are few studies on the biocontrol strains of plant wilt caused by F. equiseti. Hence, we conducted a screening and antimicrobial characterization study of marine-origin biocontrol fungi from water samples of the Yap Trench. A new Talaromyces strain DYM25 was screened from water samples of the Yap Trench in the western Pacific Ocean, and its potential as a biocontrol agent against Fusarium wilt of cucumber was studied. 18S rRNA and ITS gene sequencing verified that strain DYM25 belongs to the genus Talaromyces. The growth of F. equiseti was inhibited by strain DYM25 through the antibiosis effect. A preliminary test was first conducted to examine the bioactive stability of filtered DYM25 broth against F. equiseti under various conditions, including high temperature, UV light, alkaline environment, and the presence of metal ions, which indicated its potential as a bio-control agent. The results of the pot experiment showed that F. equiseti caused cucumber wilt, which could be mitigated using the fermentation broth of strain DYM25 (52.9 %). On the other hand, the alkaloid chromogenic reaction showed that the alkaloid salts present in the crude n-butanol extracts were most likely the major components that might have an antimicrobial effect. Therefore, Talaromyces sp. DYM25 represents a new species that can be used as a novel biocontrol agent against cucumber wilt.

Wavelength selection of terahertz time-domain spectroscopy based on a partial least squares model for quantitative analysis

Terahertz spectroscopy, combined with chemometric methods, has proved to be an effective tool in the quantitative analysis of many substances. However, current research has mainly focused on comparing different algorithms under the full spectrum. In fact, the full spectrum is not only composed of characteristic features of the samples, but also many types of noises. Hence, the accuracy of the quantitative analysis may be unsatisfactory if the full spectrum is selected. In this paper, a wavelength selection method based on partial least squares and absorption peak was proposed and an efficient frequency band was determined in the quantitative analysis of three types of pesticides, i.e., 6-benzylaminopurine, 2, 6-dichlorobenzonitrile, and imidacloprid. By introducing two parameters, the sum of peak intervals (Si) and peak width, the most efficient peak was selected from multiple peaks and the specific peak width was given with the aid of particle swarm optimization. We concluded that the most efficient absorption peak for quantitative analysis corresponding to the largest Si and full width near one-half maximum could characterize full spectrum information precisely. Comparing before and after wavelength selection, the correlation coefficient (R) of the three pesticides have increased from 0.9671, 0.9705, 0.9884 to 0.9921, 0.9934, and 0.9957. In conclusion, the proposed wavelength selection method was demonstrated to be very efficient for the quantitative analysis of the pesticide mixtures, which also could be helpful in the analysis of other multicomponent mixtures with absorption peaks.