Flexible Cascaded Wire-in-Cavity-in-Bowl Structure for High-Performance and Polydirectional Sensing of Contaminants in Microdroplets

To improve the drawback of surface-enhanced Raman scattering(SERS)sensors that are sensitive to excitation angles and realize the monitoringof contaminants in complex environments, we have proposed and prepareda cascaded wire-in-cavity-in-bowl (WICIB) structure on flexible polydimethysiloxane,with feasibility for plasmonic coupling. We demonstrated that theWICIB structure can serve as a highly sensitive, homogeneous, andstable SERS substrate for conventional detection. The plasmonic couplingand distribution of the enhanced electromagnetic field were evidentlyproven by finite element simulations, and the strong electromagneticfield was regulated around the wire and inside the cavity, which isvery beneficial for the polydirectional and in situ detection. By virtue of the triple synergistic enhancement effectand unique optical properties, we successfully achieved the in situ detection of the residual pollutant molecules, ziramand 2-naphthalenethiol, in microdroplets of apple juice and lake water.Accordingly, such a flexible SERS sensor exhibits great potentialin on-site environmental monitoring.

Automated summary

We have proposed and prepared a cascaded wire-in-cavity-in-bowl (WICIB) structure on flexible polydimethysiloxane to overcome the sensitivity to excitation angles in surface-enhanced Raman scattering (SERS) sensors and enable monitoring of contaminants in complex environments. The WICIB structure serves as a highly sensitive, homogeneous, and stable SERS substrate for conventional detection. Through finite element simulations, it was proven that plasmonic coupling and distribution of the enhanced electromagnetic field occur around the wire and inside the cavity, making it beneficial for polydirectional and in situ detection. By exploiting the triple synergistic enhancement effect and unique optical properties, we successfully achieved the in situ detection of residual pollutant molecules in microdroplets of apple juice and lake water, indicating the great potential of this flexible SERS sensor for on-site environmental monitoring.