This in-class activity was created at the NSF-TUES sponsored workshop at Penn State, June 2013. It is based on the article from Ray Schaak’s group (Buck, Matthew R.; Bondi, James F.; Schaak, Raymond E. “A total-synthesis framework for the construction of high-order colloidal hybrid nanoparticles” Nature Chemistry 2012, 4, 37-44, DOI: 10.1038/NCHEM.1195), which Ray presented at the workshop.
This activity is designed to guide students through making predictions about an experimental outcome and designing control experiments. It requires some background knowledge on the part of the students and the instructor. For example, some familiarity with techniques used to characterize nanoparticles (transmission electron microscopy, X-ray powder diffraction, energy dispersive spectroscopy (EDS), and UV-vis spectroscopy) would help the students suggest experimental ways to distinguish the nanoparticle hybrids that could form. However, the activity could be included in lower-level courses as long as students have a rudimentary understanding of the analysis techniques.
The students complete the activity without consulting a copy of the article. They are given minimal information regarding starting materials (the metal, Pt, and Fe3O4 nanoparticles that are grown) and work in small groups. They are asked to brainstorm possible products, reason through which product is most likely to form, defend their answers, and suggest relevant experimental considerations (control experiments and characterization techniques).
By participating in this activity, students will be able to:
generate possible heteromer geometries and predict the most likely product using inorganic concepts
- design a series of control experiments to explain experimental results
The students are not given Schaak’s paper prior to this activity, but rather they are provided with a short background on the synthesis of colloidal hybrid nanoparticles. The Schaak group uses a common method of nanoparticle synthesis in which metal ions are reduced in high boiling point organic solvents in the presence of alkyl chain capping agents. When the metal ions are reduced, very small nanoparticles nucleate. Further metal ions are deposited on the surface of the tiny nanoparticles. The bulky capping agent molecules surround the growing nanoparticles, halting their growth and preventing them from aggregating into larger and larger particles. In the article highlighted here, Pt nanoparticles were synthesized, followed by the growth of a Fe3O4 component.
In a short “pre-activity lecture”, students are given a general aim of the researchers to connect three nanoparticles, Pt, Fe3O4, and Ag, and then separated into groups of 2–3 to answer the following questions. To create a more hands-on experience, provide three differently colored balls to each group. Instead of using colored balls, student could be asked to draw out their structures in a similar manner to Figure 1a from the paper.
The LO consists of a handout for students and a solutions document for instructors that contains additional information in bold-face that may help with leading discussions.
This LO could be done in conjunction with the related literature discussion "A Schaaking Development of Colloidal Hybrid Nanoparticles". We have envisioned doing this in-class activity first, then giving the students the paper and doing the literature discussion the following week.
A question on experiment design could be used on a later exam to assess student understanding.