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Fun With Quantum Mechanics: Scanning Tunneling Microscopes

Note:  Check out my new avatar!  Also, Chiral and I are in the process of updating the “about this blog” and blogrolls.

Credit to the Sykes Lab of Tufts University

A research-grade low pressure/temperature STM (top) and a portable laptop-capable STM (bottom)

I know what you’re thinking:  aren’t Scanning Tunneling Microscopes (STMs) hundreds of thousands or millions of dollars?  Who has that lying around, much less in grant money?     Well… almost nobody.

STMs do indeed cost a lot of money, but can tell you a whole lot of stuff about a surface.  They’re so expensive that a simple google search doesn’t yield any results for websites which sell STMs.  Going further, I found that DME-SPM sells a whole range of STMs.  However, the prices aren’t listed (kind of like an expensive restaurant, where you only get the price once the bill comes).  Not really too affordable.

However, if you have the cash, an STM can be a fun thing to have.  After all, who doesn’t want to see things on the atomic level?  One can move hydrogen atoms around under a Pd crystal or Xenon atoms on a metal surface.  This is done using an atomically sharp tip (and the electrons attached).  Using this method, Paul Weiss managed to spell out the PSU Logo on a Pd Crystal.  (He was also part of the team that wrote out the IBM Logo in Xenon atoms).

One of the coolest things about STMs is that you can get a gigantic apparatus which has space for liquid Helium and a super vacuum and can resolve images on a atomic level OR you can get a STM that can fit on your desk, plug into a laptop, and work at STP! Well, I had the chance recently to work with one of these STMs for a Quantum Mechanics lab.

Can you see individual monolayers?  Etch points?  Sections of C10 SAMs?

My very own STM image of SAMs on a Au surface!

My group made the road trip through time and space (well, really just space) to the Sykes lab of Tufts University, where we had the chance to explore the world of atoms.  This was especially fun considering my lab group consisted of myself, an undergrad interested in synthetic chemstry, and another undergrad currently researching inorganic chemistry but going to business school.  If you’ve keeping score, that equals exactly zero people who would be interested in Quantum Mechanics.  Even so, we all had a blast playing with an STM.  Predictably, we didn’t get to use the giant STM that the lab has (which uses liquid He to cool and contains a very, very strong vacuum).  Instead, we had the chance to use a portable STM that hooks right up to a laptop.  Using this setup, we analyzed surface-assembled monolayers (alkanethiols of C8 and C10 length) on a gold surface.  Pictures on the side.

If you were curious, you can get one of these desktop STMs for around $9000 (so told by a friend in the Sykes lab).  It’s on my graduation wish list for sure.  Check back soon for more posts – now that school is winding down, Chiral and I will be on CENtral Science more.  Also tune in next monday for a look at peptidomimetics!

Not at #ACSAnaheim, but still having fun in lab!

Tin foil, it just makes the world go 'round


Look at all that heating tape!

I hope you’re all having fun at the ACS conference.  Don’t forget to go to Disneyland, and know that we on the east coast are all thinking fondly of you.  This morning I’m “stuck” in lab doing some exciting assays and studying for a Biological Anthropology exam (which I’m taking for the social science credit, due to the fact that I can’t handle ‘regular’ social science classes).  The week before spring break, I got the chance to do a really fun Quantum lab – examining the fluorescence spectra of Iodine gas.  If you’ve ever done this lab, you know that you have to heat an evacuated chamber up to around 170C – much, much higher than is comfortable.  But you get some pretty cool pictures out of it!  These were taken with a DROID camera, so are not of the best quality.  I hope you can forgive me, blogosphere.

Everybody Needs A: Laser Pointer

Laser pointers, while not entirely necessary for undergrads, are nevertheless a whole lot of fun to play with.  And for formal presentations too, I guess. You can go in several different directions on this one.  I very often see the canonical cylindrical HeNe lasers that operate with a button on the top (left).  It is and maybe a little Spartan, as gadgets go.  Interestingly, these can either be powered in traditional laser fashion, or be an LED connected via blue tooth.   More recently, I’ve become partial to the laser pointers that also act to advance your slides (right).  They can be more expensive, but it’s up to you (or your PI) if the extra cost is worth the fun of not being tied to your computer during a presentation or lecture.

One can purchase laser pointers from almost anywhere, and unless you want something particularly fancy, you can get them for pretty cheap.  If you’re interested in colors, you can get laser pointers in the ubiquitous red or green, as well as violet, yellow, blue, and infrared (though I’m not so sure how that would be useful for everyday use…).  Though I’m sure a yellow laser pointer would really liven up any presentation, I can’t imagine that it would be generally accepted among our community.  Correct me if I’m wrong.

Another more interesting (and fun) direction is a high-power HeNe or GreNe (what people at my University call a green laser.  Not sure if that’s standard, per se).  While difficult to point specifically without the use of a ring-stand/clamp apparatus, high powered lasers are a whole lot more fun.  More importantly, you can go straight from a presentation to examining the effects of the photoelectric effect.  This brings us to our fun-quantum-mechanics-picture-of-the-day! A couple weeks ago, my quantum mechanics lab had the distinct pleasure of quantifying the photoelectric effect.  As you’d expect, this lab consisted of 3.5 hours of adjusting knobs in the dark, resulting in general delirium and sensitivity to light for the rest of the day.  The voltage-meter in the back reads 0.00 because (if you remember your quantum physics) a ‘stopping potential’ had been carefully applied the measure the work function of the collector electrode in this setup.  I apologize for the poor picture quality – this was done with a cell-phone camera!

However we get really cool pictures like the one to the left!

For other fun with GreNe lasers, check out Chiral’s post from a year ago!  His pictures are definately a little better quality than mine.  Also, check back soon for a post about the REU experience from a real live grad student who has gone through one!