Rapid synthesis of gold nanoparticles with carbon monoxide in a microfluidic segmented flow system

A microfluidic reactor was developed to enhance the speed (reaction time <4 min) and control of the synthesis of gold nanoparticles (3-25 nm) with or without capping agents using carbon monoxide as gaseous reductant, which is easy to remove from the reaction mixture by venting. Gas-liquid segmented flow was formed inside a 1 mm inner diameter coiled flow inverter with aqueous gold precursor and the reducing gas to produce gold nanoparticles with polydispersity as low as 5%. The uncapped gold nanoparticles make the product attractive for surface-enhanced Raman scattering, and showed an average enhancement factor of 1.94 x 10(5). Various capping agents (tri-sodium citrate, polysorbate 80, oleylamine and poly(ethyleneglycol) 2-mercaptoethyl ether acetic acid) and different operational parameters were also tested, demonstrating that the proposed synthesis is flexible and can continuously produce a variety of gold nanoparticles, with potential for other applications.