Electrolyte- and Hydrodynamics-Controlled Potentiostatic Growth of Ag Nanodendrites on Metallic Ti for SERS Detection

Ag nanodendrites (AgNDs) were directly grown on nonanodized metallic Ti via potentiostatic electrodeposition (PED) to produce a simple and controllable SERS substrate. The effects of electrolyte composition and hydrodynamic conditions on dendritic growth were systematically investigated, revealing that the combined presence of a supporting electrolyte (NaNO₃) and magnetic stirring enables sustained tip-driven growth and hierarchical branching. An optimal dendritic architecture was obtained at 2.0 V for 60 s, yielding the highest SERS enhancement. The strongest responses were found to arise from an experimentally optimal morphological regime characterized by intermediate surface coverage (∼50-65%) and well-developed secondary branching, which maximizes hotspot density while preserving interbranch gaps. Postdeposition conditioning proved critical, as mild PBS conditioning (50 mM) effectively suppressed intrinsic background signals while preserving dendritic morphology and establishing a chemically compatible interface for subsequent molecular and biomolecular interactions. The optimized AgND/Ti substrate exhibited robust analytical performance, achieving a limit of detection (LoD) of 3 × 10^-8 M for Rhodamine 6G and consistent enhancement across chemically distinct dyes, including methylene blue and crystal violet. Beyond small-molecule detection, the substrate demonstrated compatibility with biomolecular SERS measurements and controlled surface functionalization. Biomolecular species produced reproducible amide-dominated spectral features, while MPA-EDC/NHS chemistry enabled stable covalent immobilization of monoclonal anti-α-fetoprotein antibodies (Ab-AFP) while maintaining a detectable and reproducible SERS response under the applied experimental conditions. Overall, these results establish clear morphology-performance and surface-functionality relationships in AgND/Ti substrates and highlight their potential as integrated platforms for molecular and biomolecular SERS-based detection.