Counting Gold: Using Atomic Force Microscopy to Characterize Gold Nanoparticles

Nanotechnology has been recognized as an important driver of the future economy, and so nanoscience is increasingly being incorporated into the undergraduate chemistry curriculum. This experiment includes the chemical synthesis, optical and chemical testing, and microscopic imaging of gold nanoparticles. Since nanoparticles are too small to measure with optical microscopy, this lab introduces students to atomic force microscopy (AFM). AFM is much more affordable than transmission electron microscopy (TEM). With AFM in dynamic mode, nanoparticles deposited onto a flat surface can be counted and measured with almost the same accuracy as TEM. The vast majority of the thousands of students whom we have taught experience success with this experiment. Introductory students (nonscience majors and general chemistry) work in small groups and experience hands-on demonstrations of the AFM instrument. At the advanced level, we have implemented this experiment in a “flipped” lab. For both student populations, we demonstrate an increase in enthusiasm for science and an understanding of nanotechnology.