Highly Sensitive W18O49 Mesocrystal Raman Scattering Substrate with Large-Area Signal Uniformity

Although mesocrystals with ordered building units have great potential in many fields because of the large amount of organic molecules used as structure-directing agents during their synthesis process, severe matrix interference makes their surface-enhanced Raman scattering (SERS) properties rarely understood. Herein, a rapid (20 s) and green microwave synthetic route is developed for the 100 g scale preparation of plasmonic W18O49 mesocrystals with no additives. The ultrathin (1.5 nm) and oxygen vacancy-rich W18O49 nanowires as a building unit greatly improve the interface charge transfer, while the periodic mesocrystal structure significantly enhances the localized surface plasmon resonance effect and creates high-density electromagnetic hot spots among the nanowires. An outstanding enhancement factor of 1.2 x 10(7) and an ultralow detectable limit of 10(-11) M are achieved, and the single-molecule imaging is also realized on this mesocrystal-based SERS substrate. Moreover, the relative standard deviation of the fabricated large-area (2.2 cm(2)) SERS substrate is only 6.8%.

Automated summary

A rapid and green microwave synthetic route was developed for the preparation of plasmonic W18O49 mesocrystals with no additives. The ultrathin nanowires and oxygen vacancy-rich building units, along with the periodic mesocrystal structure, significantly enhanced the SERS properties, achieving outstanding enhancement factor and ultralow detectable limit. The large-area SERS substrate fabricated showed a low relative standard deviation, indicating good reproducibility.