Efficient and tunable shape selective synthesis of Ag/CeO2 nanostructures modified highly stable SERS substrate for ultrasensitive detection of pesticides on the surface of an apple

Detection of pesticide residues from fruits and vegetables is of significant importance to ensuring human health and environmental safety. An efficient and tunable shape-selective synthesis of Ag/CeO2 nanostructures as an active flexible SERS substrate for the detection of thiram on an apple surface via a paste, peel off, and paste again process was performed. The well-controlled formation of silver assembled CeO2 microspheres constituting nanospheres and nanospindles with an average size of approximately 56 and 32 nm with anisotropic structures has been confirmed through morphological and crystallographic analysis. Interestingly, CeO2 (111) was strongly anchored in the Ag (111) matrix, which provides a more adequate pathway for rapid ion-electron transportation, as observed from the structural and chemical composition analysis. The detection of thiram on the surface of an apple using our proposed nanospindle SERS active substrate achieves a wide detection range from 10(-2) to 10(-9) M with a correlation coefficient of 0.9929 and a low detection limit of 27 nM at S/N = 3. In addition, the charge transfer mechanism between the Ag/CeO2 nanostructures and thiram molecules has also been proposed. We believe that the present work could provide novel ways to develop SERS active substrates for highly efficient onsite detection of pesticides on fruits in the near future.