Modulating the Energy-Band of Metal Oxide@Metal–Organic Framework Core–Shell Nanoparticles for Enhanced Raman Sensing

Surface-enhanced Raman scattering spectroscopy (SERS) can provide molecular fingerprint peaks of the vibration information with great specificity and sensitivity. It is widely used in biomedical and chemical fields. Semiconductor-based substrates represent a hot spot in the field of SERS beyond conventional noble metals, and metal–organic frameworks are rarely realized for SER detection. Here, we modulate the energy-band structures of metal–organic frameworks (MOFs) further by metal oxides (MOs) to match the energy band of a target analyte. We construct MOF-encapsulated metal oxide core–shell nanoparticles (MO@MOFs) as substrates for Raman enhancement. Attributed to the high structural tailorability of both core and shell, a series of energy-band structures have been created. We perform SERS detection of rhodamine b (RhB) on MO@MOF and find that the enhanced factor of Fe 3 O 4 @MOF(Co) and TiO 2 @MOF(Ni) reach as high as 10 8 and 10 6, respectively, with low detection limits of 10 –8 M, much lower than that using the corresponding MOFs. The SERS enhancement is based on mechanisms including charge transfer, interband and molecule resonances, and ground-state charge-transfer interactions. This work will promote the application of semiconductor-based nanomaterials with special modularity for surface-enhanced Raman scattering substrates.