Plasmonic MoO2 Nanospheres as a Highly Sensitive and Stable Non-Noble Metal Substrate for Multicomponent Surface-Enhanced Raman Analysis

Semiconductor-based surface-enhanced Raman spectroscopy is getting more and more attention because of its great price advantage. One of the biggest obstacles to the large-scale application of it is the poor stability. Here, we report that plasmonic MoO₂ nanospheres can be used as a highly sensitive and stable semiconducting-substrate material for surface-enhanced Raman scattering (SERS). By using the MoO₂ nanospheres as Raman substrates, a series of typical compounds with high attention can be accurately detected. This new non-noble metal substrate material shows a very high detection limit of 10^-8 M, and exhibits great near-field enhancement with one of the highest enhancement factor of 4.8 × 10⁶ reported to date. More importantly, the oxide with intermediate valence displays unexpected ultrahigh stability, which can withstand the corrosion of strong acid and strong alkali as well as 150 °C high temperature oxidation in air. Moreover, the accurate detection of multicomponent samples was also successful on this substrate. These results show that some simple metal oxides with intermediate valence may become sensitive and stable SERS substrate materials due to their abundant free electrons and structure that easily causes hot spots.