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A fluorescent aptasensor was constructed for the high-sensitivity and high-selectivity detection of 17β-estradiol (E2) based on the fluorescence quenching effect of gold nanoparticles (AuNPs) on carbon quantum dots (CQDs) and the specific affinity of aptamers to targets. Under the optimal conditions (particle size of AuNPs = 39 nm, AuNPs amount = 200 μL, quenching time = 20 min, and fluorescence recovery time = 60 min), a good linear relationship was observed between the fluorescence recovery degree (y) of the sensor and the logarithmic value (x) of E2 concentration (2 × 10-5–2 × 10-9 mol/L), which was fitted with the following equation: y = 58.50x + 558.95 with a determination coefficient (R2) of 0.992. The detection of limit (LOD) of E2 was 3.4 × 10-10 mol/L. Finally, the aptasensor was successfully applied to the detection of E2 spiked in milk and environmental water samples with good recoveries of 89.67%‒113.36%, suggesting the potential for practical application.

A core-shell-satellite nanostructure surface-enhanced Raman scattering (SERS) substrate based on magnetic nanoparticles, metal-organic frameworks (MOFs) and gold nanoparticles (Ag NPs) was established and applied in the simple, rapid and sensitive detection of the organophosphorus pesticide triazophos in agricultural products. MIL-100(Fe)-coated Fe3O4 was prepared by low-temperature cyclic self-assembly method, and Ag NPs were in-situ grown on the surface of MIL-100(Fe)-coated Fe3O4 by silver mirror cycling. The SERS sensing of triazophos residues in apples was carried out. The logarithmic value (Y) of the characteristic peak intensity of triazophos was linearly related to the logarithmic value (X) of its concentration in the range of 0.05–10 mg/L, which was described by the following equation: Y = 0.573 8X + 2.804 (R2 = 0.980). The limit of detection (LOD) was as low as 11.9 mg/L. The recoveries of the developed method ranged from 90.07% to 103.27% at spiked concentrations of 2, 5, and 10 mg/L. Therefore, the prepared SERS substrate has great potential for application in the detection of pesticide residues in foods.

Objective: The development of a method for detecting pesticide residues based on surface enhanced Raman scattering (SERS) substrate of MXenes (Ti3C2Tx) of two-dimensional nanoparticle materials. Methods: Firstly, a single layer of negatively charged MXenes two-dimensional material was prepared by fluorine salt etching method, and then synthesized 30 nm of gold nanoparticles (AuNPs) modified by the positively charged surfactant CTAC, and AuNPs/MX- enes was prepared with MXenes loaded with AuNPs by electrostatic adsorption. Secondly, the concentration ratio of AuNPs and MXenes colloidal solutions was optimized with R6G as the Raman probe molecule. Thirdly, it is used for the detection of thiram. Results: The Raman enhancing factor of AuNPs/MXenes is 1.7xl05, which showed good SERS activity. A linear relationship was constructed between the strength of the thiram Raman characteristic peak at 1 379 cm-1 and the logarithm of the thiram pesticide residue concentration, and the standard curve was obtained: y=888x+l 151, the coefficient R2 was 0.986, and the detection limit was 0.051 ng/mL, which was lower than the national standard of 5 ng/mL. The QuEChERS method was used to pretreat the citrus samples, and the SERS detection of thiram residue in the real citrus samples was realized, and the recovery rate ranged from 101.1% to 122.0%. Conclusion: The SERS substrate prepared based on the MXenes structure has potential for thiram detection in citrus samples. [ABSTRACT FROM AUTHOR]