Flexible, Reusable SERS Substrate Derived from ZIF-67 by Adjusting LUMO and HOMO and Its Application in Identification of Bacteria

Conventionally, surface-enhanced Raman spectroscopy (SERS)-active materials mainly include nanosized noble metals, semiconductors, or the complex of both, most of which are limited in practical applications because of their symbiotic materials, complex and difficult to control fabrication processes, and reuse and sampling challenges. To address these issues, novel SERS substrates have been developed in this study by anchoring zeolitic imidazolate framework-67 (ZIF-67) and derivatives of ZIF-67 to cotton fabric. The designed SERS substrates show extraordinary flexibility, an excellent enhancement factor, and reusable performance. By adjusting the lowest unoccupied molecular orbital and highest occupied molecular orbital of ZIF-67 through a doping process with different metal ions, the substrates exhibit a high enhancement factor of 6.07 × 10⁶ and a low limit of detection of 10^-8 M, as well as reusability resulting from photocatalysis. The enhancement process is studied based on charge transfer resonance, interband transition resonance, ground state charge transfer, and the light coupling effect. The results contribute to the approaches in designing SERS substrates by using ZIFs as unique SERS-active materials, and provide new insights into the development of novel SERS-active materials, along with promoting the use of SERS detection in the real world by improving the flexibility of substrates.