Highly Sensitive W<sub>18</sub>O<sub>49</sub> Mesocrystal Raman Scattering Substrate with Large-Area Signal Uniformity
Yuting Ye, Chao Chen, Wentao Li, Xingzhou Guo, Haifeng Yang, Haomin Guan, Hua Bai, Wei Liu, Guangcheng Xi
Abstract
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 × 107 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 cm2) SERS substrate is only 6.8%.