Simulation study of size and aggregation effect on colorimetric spherical gold nanoparticles

Abstract

Gold nanoparticles have considerably explored in science and technologies. A unique properties of gold nanoparticles is the appearance color due to plasmon effect. Experimentally, the color changes due to size and aggregation of gold nanoparticles in synthesis process or interaction with other chemicals. Comprehensive study on size and aggregation effect of colorimetric gold nanoparticles in liquid is important to do to provide fast observation of properties of gold nanoparticles. In this work, we focused on simulation study to observe size and aggregation effect on spherical gold nanoparticles dispersed in water. We used MNPBEM Toolbox to generate extinction cross section curves and used them to calculate color coordinates in color diagram CIE 1931. We successfully generated standard colorimetric plot of monodispersed spherical gold nanoparticles having diameter from 5 nm until 200 nm. The small size of spherical gold nanoparticles showed pink color and the color shifted to blue for larger particle. Furthermore, we analyzed calculated color coordinates for spherical gold nanoparticles in two aggregation configurations, which were triangle and line configurations. We found that aggregation of spherical gold nanoparticles significantly shifted appearance color. Aggregation of small size spherical gold nanoparticles shifted the color from pink to purple and dark red. Meanwhile, aggregation of medium and large spherical gold nanoparticles shifted the color from blue to pink. We believed that our simulated work could give fast observation on colorimetric spherical gold nanoparticles.