Pretty Science Pictures

 I did some more TEM work with my samples yesterday to see how I had been progressing with my lab work.  This week I got an "OK, you are making progress" from my labmates who were helping me with the microscope, rather than the "wow, you managed to mess up every sample you made" that I got last week (well, they said it more tactfully than this).  So, I'm pretty happy with that.  I always really like TEM pictures, even if the samples themselves aren't that great, so I thought I would post a couple here.

The first sample I've been working on making are magnetic iron oxide nanocrystals.  Iron oxide forms several phases and crystal arrangements, but it's important that I get 100% of the phase that I am looking for, Fe3O4.  On top of that, the crystals all need to be basically the same size.  That size is very small: about 10 nm across.  Finally, they also need to be monodisperse, which means that they're not all stuck together in one big clump but are each existing as their own separate little crystal.  Here's a picture of one of my samples from last week:

Terrible!  All different crystal sizes and they're all stuck together in that big dark clump in the middle.  Now, here is a much better one from this week:

So much nicer!  The particles are mostly homogeneous and really nicely spread out at the bottom.  And they're tiny (in the 5 to 10 nm range)!  Some of them are still stuck together but I should be able to fix that next week.  Still a problem though: my sample isn't a pure phase yet.  I want 100% Fe3O4 but instead I'm getting a mixture of Fe3O4 and FeOOH.  This is quite frustrating, because we can't really figure out how to get rid of the impurities yet. 

The really neat thing about high resolution TEM is that you can actually zoom in far enough to see the crystal planes in the particles.  In this closeup, each of the little crosshatch lines you can see is a crystal plane.

Neat!  This is a good way to quickly check if you sample is crystalline or not.  Another TEM capability is that is useful for this is selected area electron diffraction (SAED), which produces a pattern of either dots or rings that tell you about the degree of crystallinity of the sample as well as it's crystal structure.


The other main part of my project involves coating silica nanospheres with titania.  This process is made much more difficult by the fact that the titanium chemical that I use in the synthesis is air and water sensitive.  If I expose my reaction to air or water, titania condenses out of the solution very quickly.  Although I want to end up with titania in the end, I only want it to coat the silica spheres, and not end up all over the place in my sample.  Well, this is what happened to my sample last week:

See all the random stuff around the spheres?  That's rogue titania, which I do not want.  You can see that the spheres are also coated in titania - they look darker in the center because of the silica in the middle, and you can kind of see a ring around the edge which is the coating layer.  This can been seen a lot better in one of my pictures from this week:

Here, the edges are a little rough, but you can see the coating layer on the edges pretty well.  And much less random titania particles floating around in there.

Overall, nice to finally make some progress and feel like I'm starting to get the hang of things around here.