Continuous production of gold nanoparticles: towards industrial production

Abstract

Gold nanoparticles (AuNPs) have gained significant attention due to their applications in catalysis, sensing, electronics, diagnostics and therapeutics, necessitating scalable and reproducible production methods. Currently established protocols of the synthesis of AuNPs restrict up-scalability, thus preventing their industrialization into biomedical fields that could otherwise exploit their ground-breaking assets. This study explores a continuous hydrothermal process for the synthesis of AuNPs using gold trihydroxide (Au(OH)₃) as a chloride-free precursor, compatible with lab-made industrial-grade equipment. Batch synthesis was first used to determine optimal reaction conditions based on the Turkevich–Frens method, employing trisodium citrate as a reducing agent. These conditions were adapted to a continuous setup operating at high pressure (250 bar) and variable temperatures (100–400 °C). Under high pressure, well-dispersed AuNPs with different sizes and morphologies were successfully synthesized. Characterization of sizes, shapes and localized surface plasmon resonance confirmed successful particle formation and provided information about the dispersion state and optical properties. The system enabled steady AuNP production with minimal loss, demonstrating a promising route for scalable and controlled AuNP synthesis suitable for biomedical applications.