Exploring the interplay of LSPR and CT: Hierarchical shell thickness optimization for advanced SERS sensing using AgNW@ZIF-8 Core@Shell substrates

Synergistic surface-enhanced Raman spectroscopy (SERS) substrates, leveraging the combined strengths of electromagnetic enhancement (EM) and chemical enhancement (CM), have been extensively explored in the literature. In this study, we introduce a distinctive approach to fabricating core@shell structures, specifically employing silver nanowire @ zeolite imidazole framework-8 (AgNW@ZIF-8) as synergistic SERS substrates. Notably, these substrates offer meticulous control over shell thickness through a straightforward post-synthesis procedure. Utilizing Ag nanowires as the plasmonic core, selected for their broader localized surface plasmon resonance (LSPR) absorption range compared to nanoparticles, we encapsulate them within ZIF-8, a metal-organic framework (MOF) recognized for its proficient charge transfer (CT) properties. Our investigation encompasses the SERS performance across various Raman-active molecules, considering their diverse sizes and distinct frontier molecular orbitals (FMO) energy levels. Additionally, we systematically explore the influence of alterations in shell thickness on SERS outcomes and scrutinize the impact of probe orientation. This comprehensive study not only advances the understanding of synergistic effects intrinsic to MOFs-metal SERS substrates but also provides valuable insights for the rational design of highly sensitive substrates tailored for practical applications.