**4. Conclusions**

To satisfy the improved requirement of safety food, a novel nano/micro-structured pesticide detection card was creatively fabricated by taking the electrospun fiber mat as the card matrix. This detection card has good storage stability and a low minimum detectable concentration, the application of which involves a short reaction time, simple operation, and minimum use of human and material resources as compared to the traditional detection approaches. In addition, experiments with real samples also demonstrated its feasibility and superiority on pesticide detection over the commercial card. More importantly, this detection method can even be performed by nonprofessional individuals, making it more in line with the market requirement. Therefore, the present study offers a new route for designing a rapid detection card for pesticides, which could promote the application of the electrospinning technique and nano/micro material in the agricultural and food industry.

**Supplementary Materials:** The following are available online at https://www.mdpi.com/article/10 .3390/foods10040889/s1, Figure S1: SEM images of electrospun fibers at different ratios of CH3OH to CHCl3 (the electrospinning conditions were: voltage of 13 kV, flow rate of 2.5 mL/h and distance of 13 cm); Figure S2: SEM images of electrospun fibers at different concentrations of PCL (the electrospinning conditions were: voltage of 13 kV, flow rate of 2.5 mL/h and distance of 13 cm); Figure S3: SEM images and fiber diameter distributions of PCL fibers under different electrospinning voltages (the electrospinning conditions were: flow rate of 2.5 mL/h and distance of 13cm); Figure S4: SEM images and fiber diameter distributions of electrospun PCL fibers under different flow rates (the electrospinning conditions were voltage 13 kV and distance 13 cm); Figure S5: SEM images and fiber diameter distributions of electrospun PCL fibers under different distances (the electrospinning conditions were: voltage of 13 kV and flow rate of 2.5 mL/h); Table S1: Effect of PCL concentration and volume ratio of CHCl3 to CH3OH on the properties of electrospinning solution.

**Author Contributions:** Conceptualization, K.F., M.-Y.Z.; formal analysis, K.F., M.-Y.Z. and Y.-S.W.; investigation, K.F., M.-Y.Z.; visualization, K.F.; writing—original draft, K.F.; writing—review and editing, M.-H.Z., H.W. and S.-Y.H. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Key Area R&D Program of Guangdong Province (No. 2019B020211002), the Collaborative Innovation Center for Sports of Guangdong Province (No. 2019B110210004), the Science and Technology Project of Guangzhou City (No. 201804010151), and the Natural Science Foundation of Guangdong Province (No. 2017A030313148).

**Data Availability Statement:** Data are contained within the article or supplementary material.

**Acknowledgments:** We acknowledge the Key Area R&D Program of Guangdong Province (No. 2019B020211002), the Collaborative Innovation Center for Sports of Guangdong Province (No. 2019B110210004), the Science and Technology Project of Guangzhou City (No. 201804010151), and the Natural Science Foundation of Guangdong Province (No. 2017A030313148) for financial support.

**Conflicts of Interest:** The authors declare no conflict of interest.
