Electron-Donating Benzenethiols Direct Rapid Formation of Plasmonic Gold Nanoflowers

Gold nanostructures with branched morphologies exhibit strong plasmonic properties, enabling advanced biosensing and biochemical applications. Here, we report a rapid and scalable synthesis of gold nanoflowers (AuNFs) using modified benzenethiols as both reducing and capping agents. Benzenethiols bearing electron-donating substituents promoted rapid Au³⁺ reduction and anisotropic branch growth, completing particle formation in less than 10 s without seed preparation or organic-aqueous transfer steps. The resulting AuNFs had abundant plasmonic hot spots and intrinsic Raman reporters, serving as dual-modality probes for colorimetry and surface-enhanced Raman scattering (SERS). When integrated into lateral flow assays, AuNFs markedly enhanced analytical sensitivity. In oxycodone detection, limits of detection reached 4.48 pg/mL (colorimetry) and 0.38 fg/mL (SERS), representing 700-fold and 1,200-fold improvements, respectively, over spherical gold nanoparticles. This performance enabled accurate quantification of oxycodone in plasma samples from murine addiction models. The developed method provides a practical route for preparing high-performance plasmonic nanomaterials for applications in biosensing, catalysis, and analytical chemistry.