Plasmonic Hybrid Mo/MoO₂ Nanospheres as Surface-Enhanced Raman Scattering Substrates for Molecular Detection

Here, the plasmonic Mo/MoO2 hybrid nanospheres have been fabricated through a simple hydrothermal self-assembly process. The Mo/MoO2 nanospheres assembled from plasmonic Mo and MoO2 nanoparticles have loose nanostructures and exhibit an enhanced surface plasmon resonance (SPR) effect in the visible-light range. The Mo/MoO2 nanospheres are used as surface-enhanced Raman spectroscopy (SERS) substrates for the detection of trace organic pollutants, such as rhodamine 6G (R6G), rhodamine B, and methylene blue, which exhibit ultrasensitive SERS activity. The minimum limit of detection for R6G is 1.0 × 10–10 M, and the highest enhancement factor is up to 6.2 × 107. The theoretical calculations and experimental results indicate that the extraordinary sensitivity is mainly ascribed to the synergistic plasmonic effects between Mo and MoO2 nanoparticles in the hybrid nanospheres, which lead to the strong electromagnetic coupling between substrates and target molecules. This study provides an approach to optimizing the SERS performance of semiconductor-based substrates.