Light Erasable Surface-Enhanced Raman Scattering Substrates based on the Metallic Molybdenum Dioxide Nanospheres

Surface-enhanced Raman scattering (SERS) is a powerful label-free technique for the identification of molecules and molecular structures at extremely low concentrations. However, in most cases, the analytes will remain on SERS substrates, making the substrate a disposable consumable. Here, we propose a light erasable SERS substrate based on the metallic molybdenum dioxide (MoO2) nanospheres. The MoO2 nanospheres present a remarkable localized surface plasmon resonance (LSPR) absorption peak centered at 800 nm. Profiting from the local field magnification induced by the LSPR, MoO2 exhibits excellent SERS detection sensitivity towards rhodamine 6 G (R6G), rhodamine B (RhB), methyl blue (MB), crystal violet (CV) and Malachite Green (MG), with a detection limit of 10-7 M and a maximum enhancement factor up to 5.4 × 104. Moreover, the metallic MoO2 nanospheres possess a high photothermal conversion efficiency of 70.1% and good photothermal stability. The temperature of the MoO2 surface can reach 438 °C under 808 nm laser irradiation with a power density of 2.5 W cm-2, exceeding the decomposition temperature of most organic molecules. Thus, the residual probe molecules can be completely removed from the MoO2 substrate in less than 7.5 minutes under laser irradiation without compromising its SERS sensitivity and reproducibility. We anticipate our work will pave a new avenue for the development of reusable and highly sensitive SERS substrates.