Hybridizing Black Phosphorus Nanosheets and Multishaped Silver Nanoparticles for Surface‐Enhanced Raman Scattering Detection of Rhodamine B in Chili Powder

Despite the low detection limits reported in previous surface‐enhanced Raman scattering (SERS) studies for Rhodamine B (RhB, a dye prohibited in food products because of its potential risk to human health even at very low concentrations), further improvement in sensitivity is still required for trace‐level analysis. In this work, a hybrid SERS substrate based on multishaped silver nanoparticles (MAgNPs) and black phosphorus nanosheets (BPNS) was developed as a simple and rapid method for the sensitive detection of RhB in chili powder (a spice widely consumed worldwide). The combination of the strong plasmonic effect of MAgNPs and the matching of energy levels between BPNS and RhB facilitates charge transfer, thereby improving the Raman response. The developed SERS substrate (MAgNPs/BPNS on Si wafer) achieved remarkable limits of detection: 8.2 × 10 −8 ppm (i.e., 82 parts‐per‐quadrillion) in standard solution and 6.9 × 10 −11 g/g in chili powder, with recoveries of 94.8%–99.5% and acceptable precision, demonstrating its potential for trace‐level RhB monitoring in practical food safety applications.