Controlled electrochemical fabrication of large and stable gold nanorods with reduced cytotoxicity.

Gold nanorods (GNRs) are valued for their tunable surface plasmon resonance (SPR) and unique optical properties, but precise control over their size and shape remains challenging. Current synthesis techniques often yield polydisperse samples and require high concentrations of cytotoxic surfactants, limiting their biomedical applications. In this study, we introduce a novel electrochemical synthesis method that offers precise control of GNR characteristics by leveraging open circuit potential (OCP) data from colloidal synthesis. This approach involves the electrochemical growth of gold nano-seeds immobilized on fluorine-doped tin oxide (FTO) substrates, using physical vapor deposition (PVD) followed by thermal annealing to generate the Au seeds. This eliminates the need for seed solutions and significantly reduces surfactant usage. By optimizing electrochemical parameters, we produce uniform GNRs up to 700 nm in length, surpassing the typical 100 nm size from traditional methods. These larger GNRs exhibit superior optical and thermal properties, making them ideal for biomedical imaging, photothermal therapy, and applications requiring deeper tissue penetration. Their increased size also enhances stability, biosensing sensitivity, and circulation time, making them suitable for drug delivery and catalysis. This scalable method improves nanorod growth understanding while addressing cytotoxicity concerns.