Polydopamine@Gold Nanowaxberry Enabling Improved SERS Sensing of Pesticides, Pollutants, and Explosives in Complex Samples.

Surface-enhanced Raman scattering (SERS) is a promising analysis technique for detecting various analytes in complex samples due to its unique vibrational fingerprints and high signal enhancement. However, impurity interference and substrate unreliability are direct suppression factors for practical application. Herein, we synthesize polydopamine@gold (PDA@Au) nanowaxberry, where Au nanoparticles are deposited on the surface of PDA sphere with high density and uniformity. Seed-mediated synthesis is used for fabrication of nanowaxberry. Au seeds are deposited on the surface of PDA sphere, then I ion coordinating ligand is employed to form stable AuI4 - complex with AuCl4 - , which decreases reduction potential of AuCl4 - and avails formation of shell structure. Such nanowaxberry has high density of voids and gaps in three-dimensional space, which could absorb analytes and benefit practical SERS detection. Using malachite green as a model analyte, nanowaxberry realizes highly sensitive detection with low limit of detection (1 pM) and good reproducibility (relative standard deviation of about 10%). Meanwhile, the nanowaxberry is employed for practical detection of thiram, benzidine, and 2,4-dinitrotoluene in the environmental water, juice, apple peel, and soil. The high performance makes nanowaxberry to be potentially used for pesticides detection, pollutants monitoring, and forbidden explosives sensing in complex samples.