Kinetics-based design of a flow platform for highly reproducible on demand synthesis of gold nanoparticles with controlled size between 50-150 nm and their application in SERS and PIERS sensing

Abstract Seeded-growth synthetic protocols enable precise control of particle size and shape, crucial for many sensing applications. However, scaling-up these syntheses in a reproducible way is challenging, as minimal variation in process parameters such as seed size, concentration or reaction temperature can significantly alter the final product. Flow reactors enable tight control in the process parameters and high reproducibility of the synthesis, representing a potential technology to perform seeded-growth synthesis in large scale. This work reports the design of a flow platform for the controlled synthesis of spherical gold nanoparticles with size up to 150 n m through a seeded-growth approach, and their use in Surface Enhanced Raman Scattering (SERS) and Photoinduced Enhanced Raman Spectroscopy (PIERS). The particle growth kinetics were studied via in situ time-resolved UV-Vis spectroscopy. The spectroscopic data were fitted with a kinetic model, which was subsequently used for the design of the reactor. The kinetics-based design approach enabled fast translation of the growth synthesis in flow, eventually allowing the on demand flow synthesis of particles with controllable size, ranging from 50 to 150 n m , with high reproducibility and full precursor conversion. The particles were tested for SERS and PIERS for different substrates, including warfare agents and biomolecules, with enhancement factors between 10 3 and 10 8 depending on the analyte, demonstrating their potential for detection of various analytes.