Thursday, May 14, 2015
Adventures in TEM
Last Tuesday I sprained my left ankle while playing tennis. Lucky me, I got to use crutches for four days, hobbling my way around campus with aching armpits and a really sore right leg. Now, normally, we perform most of our lab work sitting down at our lab bench so the physical status of my left ankle is not a concerning matter.
However, the day after I sprained it, we arrived in lab, eager to perform the long awaited TEM imaging of our gold nanoparticles and Professor Belcher informed us that we would have to hurry over to building 13. For reference, it took me over 20 minutes to get from Maseeh to Hayden Library (and a whole lot of huffing and puffing). There was no way I would be able to hurry over on my crutches.
Thankfully, someone came up with the brilliant idea of me being pushed around on one of the swivel-rolling chairs that we usually sit on for lab work. So I hopped onto one of the chairs (sans armrests, which I guess could have been dangerous, but oh well, we live life on the edge), and my wonderful lab partner Tara proceeded to push me down two floors, through the infinite (to the surprise of more than a couple of students), down another flight of stairs, over some asphalt, and finally to the long awaited TEM room.
The TEM was a hulking, off-white machine controlled by a massive control panel that looked like one of those mission control dashboards from Hollywood space movies. The long, cylindrical series of lenses extended well past the tops of our heads and though the room was a little cramped, our group of six people attempted to all squeeze in.
The person operating the TEM was apparently a solar cell expert who had been preparing them for years and operating this fine (and assuredly expensive) piece of equipment). He, along with Professor Belcher, talked us through some of the procedural steps as they prepped our copper meshes and focused the electron beam.
Finally, with the lights dimmed and our group metaphorically holding a collective breath, the first image appeared on the screen.
It looked like a blob. Like an amorphous, grayish, tentacle-like blob. Apparently it was mineralized phage with titania. But it mostly looked like a blob. Further searching, zooming, and focusing finally revealed a large black circle in the middle of the grayish blob.
We had found gold! The Blue team had used 12nm particles and on the computer screen before us was an image of a gold nanoparticle. The resolution was such that we could see straight lines across the particle, indicating the structural planes of the particle. Elemental analysis of their sample also confirmed the presence of gold, which was exactly what we were hoping for in our quest for the most efficient solar cell.
Finally, it was our turn. It was time for the Red team to kick butt in the looking-at-gold-nanoparticles department. Admittedly, we already knew that our efficiency had been abysmally low (as I have alluded to in previous posts), but we had hopes that it was simply due to poor doctor-blading (also described at length in Tara’s post). We had started with 5nm particles so Professor Belcher warned us that sometimes these could be very difficult to see, let alone find in the great, gray chaos.
There were a couple of false alarms here and there, Professor Belcher a self-proclaimed optimist, but ultimately, nothing was found. There were no visible particles, and certainly none as clear and striking as the gold nanoparticle we had just seen for the Blue team. We crossed our fingers for a good elemental analysis, but that also demonstrated a lack of gold presence. We were comforted by the fact that oftentimes, TEM imaging can take hours to fully explore the entire copper mesh, and that it was possible given more time, we would indeed have found the gold that we were looking for. But since we had only searched for 5-10 minutes, it was not surprising that our small particles were temporarily unfindable (I am optimistically excluding the possibility that they were in fact nonexistent).
Perhaps our solar cell failure was due not only to a nightmare of a doctor-blading experience, but to a lack of gold nanoparticles as well. There are so many questions that would need to be answered for us to determine exactly what went wrong, but we have our hypotheses.
Using the TEM was a really cool experience because we were looking at things only nanometers wide! Having access to all of these amazing pieces of equipment, like the solar simulator as well, has been a great and exciting opportunity, and though ultimately we didn’t find what we were looking for in our sample, we still had the chance to look at the results from all the other groups in the dropbox folder.
I also had a blast being wheeled back to lab on the wheely-chair. What else would lab partners be for, if not to wheel your crippled self through the infinite and back? (Oh yeah, science.)
Thanks Tara, I’m your number one fan.