The influence of particle size to diffusivity of nanogold particles based on Brownian motion

Diffusivity calculation has been conducted by many researchers in various methods. One ingenious and sample-efficient way to determine the diffusivity is the examination under the microscope by using microbead random movements, called Brownian motion, through the footage of its movements. This study was conducted to observe the diffusivity of nanogold particles towards the use of various microbead sizes. The one-micron-sized microbead was mixed into nanogold particles solution and prepared onto slide glass, so was the three micron-sized and five-micron-sized microbead. The footage of microbead movements for each size is then tracked and processed using MATLAB image processing to obtain the mean square displacement (MSD) of the microbead and then fitting it to time to find the sample diffusivity. As a result, the nanogold diffusivity observed using one-micron, three-micron, and five-micron-sized microbead is respectively around 5.66 x 10^-17 cm²s^-1, 3.45 x 10^-17 cm²s^-1, and 1.71 x 10^-17 cm²s^-1 . Thus, the nanogold diffusivity observed using one-micron-sized microbead is greater than three-micron and five-micron-sized microbead, which can be concluded that the bigger of microbead size used, the smaller diffusivity obtained.