An ionic liquid-assisted quantum dot-grafted covalent organic framework-based multi-dimensional sensing array for discrimination of insecticides using principal component analysis and clustered heat map

Covalent Organic Framework-Involved Sensors for Efficient Enrichment and Monitoring of Food Hazards: A Systematic Review

The food safety issues caused by environmental pollution have posed great risks to human health that cannot be ignored. Hence, the precise monitoring of hazard factors in food has emerged as a critical concern for the food safety sector. As a novel porous material, covalent organic frameworks (COFs) have garnered significant attention due to their large specific surface area, excellent thermal and chemical stability, modifiability, and abundant recognition sites. This makes it a potential solution for food safety issues. In this research, the synthesis and regulation strategies of COFs were reviewed. The roles of COFs in enriching and detecting food hazards were discussed comprehensively and extensively. Taking representative hazard factors in food as the research object, the expression forms and participation approaches of COFs were explored, along with the effectiveness of corresponding detection methods. Finally, the development directions of COFs in the future as well as the problems existing in practical applications were discussed, which was beneficial to promote the application of COFs in food safety and beyond.

Hollow-structured molecularly imprinted polymers enabled specific enrichment and highly sensitive determination of aflatoxin B1 and sterigmatocystin against complex sample matrix

The biotoxins with high toxicity have the potential to be manufactured into biochemical weapons, seriously threatening international public security. Developing robust and applicable sample pretreatment platforms and reliable quantification methods has been recognized as the most promising and practical approach to solving these problems. Through the integration of the hollow-structured microporous organic networks (HMONs) as the imprinting carriers, we proposed a molecular imprinting platform (HMON@MIP) with enhanced adsorption performance in terms of specificity, imprinting cavity density as well as adsorption capacity. The HMONs core of MIPs provided a hydrophobic surface that enhanced the adsorption of biotoxin template molecules during the imprinting process, resulting in an increased imprinting cavity density. The HMON@MIP adsorption platform could produce a series of MIP adsorbents by changing the biotoxin template, such as aflatoxin and sterigmatocystin, and showed promising generalizability. The limits of detection (LOD) of the HMON@MIP-based preconcentration method for AFT B1 and ST were 4.4 and 6.7 ng L^-1, respectively, and the method was applicable to food sample with satisfied recoveries of 81.2-95.1%. And the specific recognition and adsorption sites left on HMON@MIP by the imprinting process can achieve outstanding selectivity for AFT B1 and ST. The developed imprinting platforms hold great potential for application in the identification and determination of various food hazards in complex food sample matrices and contribute to precise food safety inspection.

High-precision luminescent covalent organic frameworks with sp2-carbon connection for visual detecting of nereistoxin-related insecticide

A new strategy for nereistoxin-related insecticide, cartap, detection in foodstuff and the environment is of great importance due to its poisoning of human beings through direct exposure or via biomagnification. Herein, a highly planar conjugated sp² carbon-connected COF (F-C_sp²-TT) was synthesized via Knoevenagel condensation reaction followed by the post-modification to develop a new platform for cartap visual detection in agricultural and food samples. The synergistic effect of highly planar conjugation and dense functional groups in the opened framework endowed F-C_sp²-TT with a high-precision luminescence sensing performance. Meanwhile, the exquisitely designed F-C_sp²-TT presented robust chemical stability, radiation stability, and good reproducibility. Benefiting from these advantages, high-precision luminescent F-C_sp²-TT achieves a low detection limit of 0.51 μg/L to cartap over the range of 1-300 μg/L (R²=0.9938), and the recoveries percentage in food products was calculated as 95.90%- 119.3%. More significantly, the smartphone-based high-precision platform by F-C_sp²-TT was established and successfully applied to portable monitoring of cartap and water content. Therefore, our work revealed the enormous potential of C_sp²-connected COF, which opened a new situation for insecticide detection.

Ultrahigh sensitivity nitrogen-doping carbon nanotubes-based metamaterial-free flexible terahertz sensing platform for insecticides detection

With the rapid advances in terahertz (THz) spectroscopy, metamaterial-free THz sensors have been of importance due to efficient cost, high sensitivity and overcoming the limited tunability of the optical constants of metals. Here, a metamaterial-free and flexible THz sensor based on nitrogen-doping carbon nanotubes (N-CNTs) coupled with signal-enhancing Au NPs was proposed for detecting nereistoxin-related insecticides (NRIs). Sensitivity and selectivity for NRIs detection have been realized over the range of 3.3-100 μg/L with good linear fitting (R² ≥ 0.9003) and LOD was 1.33 μg/L. Accuracy was validated by the recovery rates of 105.87-109.75% of NRI in spiked food-matrix sample. These results indicated the developed signal-enhancing THz method, validated by LC-MS/MS, exhibited high sensitivity and simplicity detection, which has noteworthy potential for applications in food safety and environment monitoring.

Temperature-Responsive Covalent Organic Framework-Encapsulated Carbon Dot-Based Sensing Platform for Pyrethroid Detection via Fluorescence Response and Smartphone Readout

In this paper, carbon dot (CD)-encapsulated 1,3,5-tris(4-formylphenyl)benzene (TFB)/2,5-dihydroxyterephthalohydrazide (DHTH) covalent organic frameworks (TDCOFs) grafted with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) (CDs@TDCOFs@PNIPAM) were fabricated for the detection of pyrethroids. CDs@TDCOFs@PNIPAM achieved a temperature-responsive "on/off" detection of pyrethroids based on the target-triggered electron-transfer mechanism. The detection limit of pyrethroids was as low as 0.69 μg/L in the wide linear range of 5-400 μg/L (R² > 0.9523). Simultaneously, CDs@TDCOFs@PNIPAM with red, green, and blue (RGB) fluorescence emissions were integrated with a smartphone-assisted device, enabling the visual smart quantitative detection of pyrethroids with a detection limit of 4.875 μg/L. Ultimately, agricultural products were chosen as actual samples to verify the applicability of both recognition modes, and the calculated recovery rate was 105.48-113.40%. Accordingly, CDs@TDCOFs@PNIPAM featuring temperature-responsive switching behavior and RGB fluorescence emission provided a promising analytical strategy for ensuring agricultural and food safety.