Bioinspired One-Step Synthesis of Pomegranate-like Silica@Gold Nanoparticles with Surface-Enhanced Raman Scattering...

Gold-silica (Au-SiO₂) nanohybrids are of great technological importance, and it is crucial to develop facile synthetic protocols to prepare Au-SiO₂ nanohybrids with novel structures. Here we report the bioinspired synthesis of pomegranate-like SiO₂@Au nanoparticles (P-SiO₂@Au NPs) via one-step aqueous synthesis from chloroauric acid and tetraethyl orthosilicate mediated by a basic amino acid, arginine. Effects of chloroauric acid, tetraethyl orthosilicate, and arginine on the morphology and optical property of the products are investigated in detail. The P-SiO₂@Au NPs achieve tunable plasmon resonance depending on the amount of chloroauric acid, which affects the size and shape of the P-SiO₂@Au NPs. Finite-difference time-domain simulations are performed, revealing that the plasmon peak red-shifts with increasing particle size. Arginine serves as the reducing and capping agents for Au as well as the catalyst for SiO₂ formation and also promotes the combination of Au and SiO₂. Formation process of the P-SiO₂@Au NPs is clarified through time-course analysis. The P-SiO₂@Au NPs show good sensitivity for both colloidal and paper-based surface-enhanced Raman scattering measurements. They achieve enhancement factors of 4.3 × 10⁷-8.5 × 10⁷ and a mass detection limit of ca. 1 ng using thiophenol as the model analyte.