Selective deposition of a MOF at the spikes of Au nanostars for SERS detection

In the pursuit of advancing molecular sensing through surface-enhanced Raman spectroscopy (SERS), the combination of plasmonic nanoparticles and metal-organic frameworks (MOFs) has emerged as a highly effective approach to enhance the sensitivity and selectivity of SERS substrates. However, most prior investigations have predominantly focused on MOF-coated plasmonic nanoparticles in core@shell or layer-by-layer configurations, leaving a notable knowledge gap in exploring alternative configurations. Herein we present a facile method to construct a particle-on-mirror architecture by selectively coating a MOF, zeolitic imidazolate framework-8 (ZIF-8), onto the tips of Au nanostars and subsequently depositing the resultant nanoparticles onto a Au film. This design integrates the electric field enhancement at the sharp tips and nanogaps, along with the molecular enrichment function within the porous MOF immobilized at the tips and nanogaps, leading to a substantial boost in the SERS signal intensity. Such a unique SERS platform enables consistent and outstanding SERS performance for analytes of different sizes. This work opens up a promising strategy for constructing multifunctional nanostructures for sensitive SERS detection in real-life scenarios.