Surface-enhanced Raman spectroscopy (SERS) is a powerful technique that has found applications in many research fields. As promising alternatives to the current most popular plasmonic metal SERS
substrates, semiconductor SERS substrates have many appealing attributes. However, they permit signal enhancement only to analytes
adsorbed chemically on their surface, which means that semiconductor-based SERS can only be used for studying model analytes
such as dyes or thiols. Using volatile organic compounds (VOCs) as
an example, we demonstrate for the first time the detection of
non-adsorbing analytes on ZnO nanoparticles. Specifically, this
was achieved by coating ZnO nanoparticles with ZIF-8 shells, which
enriches VOC molecules and dampens the decay of the electromagnetic field around their surface, thereby significantly boosting their
electromagnetic enhancing capability such that it permits signal
enhancement for non-adsorbing analytes. Importantly, the MOFcoating strategy is universal, which means that it may enable the
detection of a wider variety of non-adsorbing analytes where conventional semiconductor-based SERS fails.