Flexoelectric‐Effect‐Enhanced SERS Substrate for Ultrasensitive and Selective In Situ Sensing Devices

ABSTRACT Surface‐enhanced Raman scattering (SERS) has developed into a powerful detection technique. Nevertheless, further improvement of its sensitivity and quantification capability is required for in situ detection applications. Purely depending on optimizing precious metal nanostructures to improve the SERS enhancement has been developed for 50 years and reached the limit. In this research, we show that the flexoelectric effect can be used to further improve SERS enhancement via designing a multilayer structure composed of Ag film/BaFe 12 O 19 /BaTiO 3 /polydimethylsiloxane. When the flexible SERS substrate undergoes bending or deformation, a tunable polarization field is generated capable of amplifying the SERS signals by up to ten times and reducing the limit of detection by four orders of magnitude. Theoretical and experimental findings indicate that the flexoelectric field can effectively modulate the electron density of Ag, thereby synchronously enhancing the electromagnetic field intensity and improving the charge transfer efficiency. Moreover, the substrate demonstrates distinct enhancement effects on narrow‐bandgap and wide‐bandgap molecules, facilitating the selective detection of molecules with varying bandgaps. The applicability of the flexoelectric SERS substrate is verified through the in situ detection of pityrosporum, borax, and gibberellin in multiple scenarios. This research can deepen the understanding of SERS mechanisms and expedite its application process.