Spectrophotemetry of Metal Nanoparticles

This activity has students chemically synthesize gold and silver nanoparticles, measure the spectra of light absorption and transmission by these particles, compare these spectra to those of known-sized particles, and then estimate the size distribution of the particles they have made. By using the interaction of light with their nanoparticles, students will measure the size of particles much smaller than the smallest things they can see with an optical microscope. This lab is designed to help students gain an appreciation of the unique ways that matter may behave at the nanoscale.  Students will also gain understanding of the relationship between energy and the frequency of light, and in the use of a spectrophotometer as a means of analyzing particle suspensions of different concentrations. The first class period should be used to introduce students to nanotechnology and quantum dots, and to synthesize the gold and silver nanoparticle samples. The second part of this activity will be used to conduct the spectrophotometry, collect data, and analyze the results. If the teacher does not have access to a spectrophotometer, one can be accessed at the Remotely Accessible Instruments for Nanotechnology (RAIN) that allows educators to freely and remotely access instruments including spectrophotometers (https://nano4me.org/remoteaccess).