Exploration of cucurbituril-mediated SERS plasmonic nanoarrays with sub-nanometer gaps

The uneven distribution of hotspots and the challenges associated with precise analyte localization within these hotspots present significant hurdles in the field of surface-enhanced Raman scattering (SERS). Here, at the water-oil interface, gold nanoparticles (AuNPs) interconnected by cucurbiturils[8] (CB[8]) with sub-nanometer gaps (AuNPs:CB[8]) were organized into plasmonic arrays. This arrangement was engineered to generate highly efficient hotspots. The CB[8] molecules, serving a dual role, not only facilitated the assembly of AuNPs with sub-nanometer (~ 1 nm) gaps to create intense plasmonic hotspots but also acted as molecular traps, enabling the precise localization of molecules within these hotspots. By comparing the enhancement effect of probe molecule on Au nanofilm, AuNPs:CB[8] colloids, and AuNPs:CB[8] nanofilm, it was found that the SERS intensity of the E1 characteristic peak in AuNPs:CB[8] nanofilm is five times higher than that on Au nanofilm, and more than 10⁴ times higher than that of AuNPs:CB[8] colloids. The gaps are also accessible to different electronegativite molecules, such as estrone, p-aminoazobenzene, or methylene blue, which are captured at the plasmonic hotspots by the interaction of CB[8]. The method was employed for the practical detection of artificial antioxidant butylated hydroxyanisole (BHA), which has a weak Raman scattering cross-section, by coupling it with a reaction to enhance its SERS effect. The detection limit of BHA in soybean oil sample is 5.89 × 10^-8 mol/L, with the recovery range 85.1-115%. In conclusion, this hot-spot design and molecular capture approach will offer a highly effective method for detecting weak Raman scattering cross-section molecules and holds great promise for practical applications in the future.