Continuous synthesis of gold nanoparticles and nanoplates with controlled size and shape under UV irradiation

Gold nanoparticles and nanoplates were synthesized through a continuous method under UV irradiation in the presence of citric acid and poly(vinylpyrrolidone) (PVP) at room temperature. Morphologies of obtained gold nanoparticles were mainly determined by experimental parameters, i.e., the concentration of PVP and the flow rate of solution. The spherical gold nanoparticles were synthesized at a higher solution flow rate (6 mL/min). The particle sizes evidently decreased from more than 10 to 2 nm with increasing concentration of PVP in solution. When PVP was absent in solution, gold nanoplates with obtuse triangle, hexagon and round shapes were synthesized under a lower solution flow rate, such as 0.5 mL/min.