Effect of citrate ratio and temperature on gold nanoparticle size and morphology

Gold nanoparticles (Au NPs) were synthesized by the citrate reduction method. The evolution of NP size and morphology was closely studied by varying temperature and citrate to gold precursor (Na3Ct/HAuCl4) ratio. The reaction temperatures below 100 °C were mainly studied. A Na3Ct/HAuCl4 ratio range of 1.25:1 to 4.33:1 was the focus of our investigation. The NP size and morphology was strongly influenced by the Na3Ct/HAuCl4 ratio, while the temperature played a subtle role. The reaction times were also monitored. The higher concentration samples required almost an order of magnitude longer reaction time compared to the low concentration samples.