Submitted by Kyle Grice / DePaul University on Wed, 06/13/2018 - 23:23
My Notes
Description

This is a nanochemistry lab I developed for my Junior and Senior level Inorganic Chemistry course. I am NOT a nano/matertials person, but I know how important nanochemistry is and I wanted to make something where students could get an interesting introduction to the area. The first time I ran this lab was also the first time I made gold nanoparticles ever! 

We do not have any surface/nano instrumentation here (AFM, SEM/TEM, DLS, etc... we can access them at other universities off-campus but that takes time and scheduling), so that was a key limitation in making this lab. 

While it was made for an upper-division course, I think It could be adapted and implemented at many levels, including gen chem. I do not spend much time on nano in the lecture (none in fact), so this lab was made to have students learn a bit about nanochemistry somewhere in inorganic chemistry. We have one 10-week quarter of inorganic lecture and lab, offered every spring quarter.

This lab takes approximately 2-3 hours if students are well prepared and using their time well, but is usually spread over 2 days. Students are concurrently doing experiments for another lab or two because we have a lab schedule that overlaps multiple labs, and can do these during one day or across two days. The lab space is an organic chemistry laboratory, so we have access to the usual lab synthetic equipment

Students in thelaboratory write lab reports,which are the due the week after the last day of the lab experiment. In the lab report they use their UV-Vis data to calculate information about the AuNP. 

The lab has been posted, as well two photos from students' ferrofluids (these were posted with permission on our departmental blog). A rubric has been posted as a faculty-only file. I have also included a student submission that received over 90% on the lab with their identifying information removed. Students write and introduction and need to cite journal articles in their report, so they are expected to do reading on nanochemistry topics outside of the lab period as they write their reports. 

I am sure the lab can be improved, this was what i came up with the materials and time I had. I plan on continuing to revise and edit it as time goes on. Any suggestions are very welcome! 

Attachment Size
Lab 3 - Nano 2017 KAG.docx 28.48 KB
ferrofluid.png 106.7 KB
ferrofluid2.png 68.63 KB
Learning Goals

A student should be able to perform a chemical laboratory experiment safely and follow proper lab notebook protocol.

A student should be able to determine the average size of AuNPs from spectroscopic data and primary literature.

A student should determine atomic and nano-scale information from physical properties.

A student should be able to construct a lab report in the style of an ACS article (Students in my lab wrote lab reports for each experiment). 

Equipment needs

For this experiment, you  need

The chemical materials - HAuCl4, trisodium citrate, 

Heating/stirring plates

Glassware

UV-Vis spectrometer (mainly Vis)

A laser pointer

Strong magnets (the stronger and larger the better)

Implementation Notes

The syntheses are relatively straightforward, although we've had some problems getting "spikes" for the ferrofluid. Anecdotally, adding the reagents and doing the steps faster tends to give better "spiking". Some students just see a blob moving around in response to the magnet, which was fine in terms of their report. 

The AuNP synthesis can also be done with an ultrasonicator or by addition of sodium borohydride, among other methods. We don't have them make a calibration curve of chloride addition, but that could be a possibility.  

I like having a pre-made solution of a red oroganic dye to shine the laser pointer through to compare versus the laser shining through the AuNP solution. 

One year, the AuNP synthesis was going very slow. We realized it was because the Au(III) was diluted in acid, so it was protonating the citrate. Boiling for a while before adding the citrate solution helped fix this problem.

KAuCl3 is also a good source of Au(III) for this lab. 

Time Required
2 hours
Evaluation
Evaluation Methods

Students are evaluated on their participation in lab, lab safety, lab notebook pages, and a lab report turned in a week after the last day of the experiment. 

Evaluation Results

This lab was first run in spring of 2016, and again in spring of 2017 and 2018 (a different instructor carried out the lab in 2018). 

In general, students do well on the lab report and seem to enjoy the experiment.They often need guidance when interpreting the Analytical Chemistry article and selecting the correct equations. Discussing their values with them in office hours ("does that make sense?") helps them understand their calculations. 

A sample lab report that scored above 90% is included in the faculty-only files. 

Creative Commons License
Attribution, Non-Commercial, Share Alike CC BY-NC-SA
Chip Nataro / Lafayette College

Kyle,

We did the Au portion of this lab in my foundations inorganic course this morning. The synthesis part worked really well. The yellow solution of the HAuCl4 (which I assumed was aqueous although the lab doesn't exactly state that) immediately turned colorless upon addition of the sodium citrate (also presumed to be aqueous). After a few seconds it turned to a grey/black color and then finally to a deep red. Then the problems started. Partially due to the crappy old UV-Vis I was using (running Windows older than my students) and part of the issue was with the salt addition. I'm okay with some vagueness in the lab for the students, but the instructor could use a little more guidance (at least this instructor could). Roughly how concentrated is the salt solution? At first I figured it could be extremely dilute. That didn't seem to change much. So we went more aggressive and that seemed to get some change in color to more of a blue-purple. It was a lot of guesswork on my part. I saved the samples and we are going to throw them on a slide and see what XRD tells us in a few weeks. My guess is that we won't get squat out of it but what the heck?

Tue, 02/25/2020 - 10:34 Permalink
Chip Nataro / Lafayette College

Another comment Kyle. In the student report and the lab instructions I think there is an error in the calculations of the number of atoms in the nanoparticles. You provide the equation N = ((pi)(rho)D3/(6 x M)) x Na. It took me a minute to figure out how you got 6. Essentially this equation is getting you moles of gold which you multiple by Na to get atoms. That's fine.So the top part of the equation is density (rho) times volume. In the bottom of the equation is the mass to mole conversion accounting for the number of atoms in the cell. You say treat the particle as a sphere. That's all well and good. So, you are using the equation V = 4/3 (pi) r3. Diameter is of course 1/2 the radius. So tracking the numbers, you get a 4 up top from the 4/3 and in the denominator your get 3 (from 4/3) x 2 (from the 1/2 diameter) x 4 (from 4 gold atoms in a FCC unit cell). The problem is that you need r3 in the volume formula and thus it needs to be (diameter/2)3. So the real equation here should be N = ((pi)(rho)D3/(24 x M)) x Na or better yet just convert the diameter to radius and get N = ((pi)(rho)r3/(3 x M)) x Na.

Tue, 03/31/2020 - 10:00 Permalink