Adventures in Silver

Students synthesize silver nanoprisms following a protocol from J. Chem. Ed.  The students observe rapid color changes as the nanoparticles grow until they reach their final size.  Students then perform a second synthesis in which each group adds a different amount of KBr, which controls the final size--and thus the color--of the resulting nanoprism solutions.

Students perform uv-vis spectroscopy on their nanoprism solution to quantify the color of their nanoprisms. Before making the spectral measurement, they predict the wavelength range where their extinction peak should appear, using both the color wheel as well as a pre-made calibration curve that relates the extinction maximum to the volume of added KBr.

Students add their spectroscopy data to our poster-sized calibration curve to see how well their results agree with data from the Willets lab (black line).  We use different colored stickers so each class can see how their results compared to others.  It is always impressive to see how close the students' data agrees with our own results!

Students also perform a galvanic displacement reaction between a copper wire and a silver nitrate solution.  It takes a while, but the silver eventually takes on the more familiar physical properties in terms of color and lustre.

To convince the students that we are really transforming silver ions to silver metal, we demo the classic Tollens' reaction.  This provides a great way to discuss redox chemistry and physical properties--plus the resulting silver is really pretty!

Throughout the day, students get a lot of personal attention from members of the lab.  We not only talk about science, but also discuss college life and being a chemistry major.