Chemistry Blog

Breaking Stuff for Science

Most chemists will agree, a chemical spill on the floor is one of the most annoying things to have to deal with in a lab. With LBL policy, you have to adhere to the SWIMS protocol: Stop work, Warn others, Isolate the area, Monitor yourself, Stay in the area. Not to mention using the correct spill kit, dealing with all the paperwork of the spill and the opening of the spill kit, explaining to the safety people what happened and why (hopefully) it wasn’t your fault, etc.

Aside from making sure your people are competent and well trained, not much is often done to prevent spills. Engineering controls such as secondary containment, fume hoods, capped reagent bottles, etc. work well when people remember and plan to use them. All too often, we see good chemists forgo extra safety steps for speed or just plain old laziness. Sometimes, people get badly hurt not because they were bad chemists or bad scientists, but because they really needed to catch the 6:40 train that day.

What we need are more safety devices that prevent the accident caused by a failure of the preventative safety measures from being very dangerous. For example, take these safety-coated reagent bottles from VWR. They have some plastic coating (PVC I think) outside of the glass to prevent spills even if the glass shatters. Sure some solvents would eat through the coating, but it would still buy you time to contain the spill, or evacuate the room if necessary.

Recently, with LBL’s current safety kick, our lab ordered 40 of these babies to replace our older reagent bottles. Interestingly though, the coating is really hard to see. In fact, when we first examined the bottles there was a dispute between some lab members as to whether we received the correct shipment or not.

Here is how the bottle looked, next to a typical graduate student size scale:

Being scientists however, Mitch and I knew that we couldn’t just take VWR’s word that we now had safety-coated reagent bottles.  We needed to test whether it really had the safety-coating, whether the coating would actually stay intact after an impact strong enough to break the glass inside, and whether the coating would feel weird if we poked with our finger.







So, using my safety training, I put the reagent bottle into a plastic bag, and put the plastic bag inside a phototray. Note the secondary and tertiary containment.






I went and found a big wrench, donned my safety goggles, lab coat, nitrile gloves and put the soon to be destroyed bottle durability testing apparatus into a fume hood with the sash half open.  I then proceeded to smash it to pieces. It was a good day of science.

Here is the result after a good beating. The safety-coating is quite clearly visible now, along with the area where the hole would be, if the coating wasn’t still covering it. The interior glass shattered as expected, but the safety-coating simply flexed a bit and recovered. Also, no sharp pieces of glass pierced the coating, so the contents of the bottle would have been contained. It took a significant amount of effort with some sharp tweezers to illustrate the intact film of the coating. We also confirmed our hypothesis that poking the film with our finger would feel weird. The bottle met our expectations in all tested categories. It also looked really cool and took a great picture.

So in our effort to make the lab safer, we tested and confirmed the usefulness of these safety-coated reagent bottles in an easily repeatable scientific experiment. Tests would have been done in triplicate, however funding was abruptly cut off when we attempted to share our findings with others in the lab.  We recommend the safety-coated bottles for use throughout the chemistry lab. All waste was disposed of in coordinance with EH&S protocol.

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Microgrippers. Because Scalpels are so 20th Century

The Gracias‘ microgripper video is now on Metacafe for those that have never seen it. The video shows a microgripper sliding down a test tube and grabbing a sample of cow tissue. The device is thermally triggered to close, and is magnetically driven. The video is shown below, there is no sound.

Tetherless Microgrippers Grabs Tissue Sample

Link to paper for those interested: Tetherless thermobiochemically actuated microgrippers

A digested version of this research was written up by Lewis Brindley for the RSC Chemistry World: Micro-machines get a grip

Mitch

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Edible Solar Cells?

I got a heads-up from Blake Farrow about turning donuts and tea into solar cells. They do a good job balancing goofiness with fun and satire. Enjoy the youtube video.

*We at Chemistry Blog fully support the development of nuclear energy and not the sad destruction of our powdered donut resources.

They also supplied an abriged version for the nanotation video contest: Nanotechnology Brings Us Delicious New Solar Cells

Our previous ACS Nano Contest coverage: The Nano Song

Mitch

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Magnetic Levitation: Because TLC Plates are so 20th Century

Mirica et al. had an awesome JACS communication out last week. They use magnets to track the progress of reactions. A schematic is shown below.

By using a paramagnetic solution (GdCl₃) and polymeric beads as their solid support, they monitor the progress of reactions as a function of their beads’ height. The setup is very sensitive to the density (g/ml) of the beads, thus as the beads are chemically modified the height changes. The beads cluster together when they are mostly all starting material or product. They spread out as different beads take different amounts of time to become fully reacted. Some images from their paper and supporting information really highlight this effect.

Reprinted with permission from the American Chemical Society: Journal of the American Chemical Society (Dec. 2008).

What else can we use magnets in the lab for, ideas anyone?

Link to article: Using Magnetic Levitation To Distinguish Atomic-Level Differences in Chemical Composition of Polymers, and To Monitor Chemical Reactions on Solid Supports

Mitch

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Linear-Motor from Carbon Nanotubes

A recent paper this week by Somada et al. regarding making a linear-motor from carbon nanotubes piqued my interest.^[NanoLett] The general design idea is to encapsulate a piece of carbon nanotube material within a larger carbon nanotube. If done correctly you can end up with a configuration as shown below.

The cargo, in yellow, transverses the carbon nanotube and rests in either position A or position B. An abridged summary of their observations is as follows: 1) From observing the system for 170 s the cargo traveled back-and-forth seven times; 2) The cargo was never filmed in between positions A and B, indicating the movement was less than the frame rate (0.5 s). From this information I can construct a likely energy landscape for this system.

Mitch’s hypothetical potential energy map for the linear-motor.

The diagram replicates the observation that the cargo at room temperature will be trapped at either position A or B. It also explains why it’s never seen between A or B, as there is no energy minimum for it to rest in. Lets assume every ~20 s there is randomly enough thermal energy to kick the system over the barrier, and that this accessible energy exists for less than 0.5 s. Then you would expect the cargo to be able to move either to A or B, and to do it faster than the shutter speed.

This is an interesting system for analysis, but it’s not a motor. Or conversely, it is as much a motor as ethane is a useful rotor. Just because thermal energy provides the means for things to happen it doesn’t mean it generates usable work. There is no way to construct a usable motor or any device from this system, but it’s a first step in that direction. I suspect if the authors raised the temperature they would see the cargo undergoes random walk motion. Thermal energy yields a random linear-motor.

Link to article: A Molecular Linear Motor Consisting of Carbon Nanotubes

Update 1: Tim Reid also covered it at Nature Chemistry — Nanotube motors: Sliding and spinning

Mitch

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NanoDonuts

Some delictable pictures of nano-donuts from Mumtaz et al.^{[macromolecules]}

For those interested, they used poly(3,4-ethylenedioxythiophene) (PEDOT) with varying weight percent of pyrrole grafting.

Future work should be Nano-Puka Necklaces or Nano-Cheese Danishes. J/K

Link to paper: Synthesis of PEDOT Nano-objects Using Poly(vinyl alcohol)-Based Reactive Stabilizers in Aqueous Dispersion

Mitch

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ACS Day2: Graphene Ribbons

Dresselhaus of MIT did a review of her many years in carbon nanostructures. She also presented some of her recent work with different types of graphene ribbons. Specifically, for the zigzag case shown below the electronic structure will be highly metallic while the armchair graphene will have a more traditional semiconductor electronic structure.

From graphene to nanotubes to graphene again and now nano ribbons what’s next for the nanostructure field? Gold nanotubes anyone…

More Info: Crystalline Graphene Nanoribbons (thanks to Excimer)

Mitch

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Light Powered Motor and Experiment Vlogging

Most of you probably read the last issue of C&EN with the spiffy carrot loving cover story (good for me because I love carrots, but have never tried those ugly-looking BetaSweets). Inside, however, there was an extremely interesting little article in the “Science and Technology Concentrates” about light-driven pulleys turning a plastic motor.

Now photo mobile polymer materials have been around for quite a while, at least from my perspective seeing as how I wasn’t even in highschool when the big Nature paper came out. Some might remember the Nature 1999 Sep 9;401(6749):152-5 Koumura et al. paper titled “Light-Driven monodirectional molecular rotor”. Although back then, the rotation was monodirectional around a C-C double bond in a chiral, helical alkene. It was activated by UV light or a change in temperature and the motor was based on light-induced cis-trans isomerizations that caused 180 degree rotations followed by thermally controlled helicity inversions, which basically nullified half a rotation. Four isomerizations resulted in 1 complete cycle.

Well this was pretty darn cool but we’ve come a long way since then. As expected, and as Koumura said, structurally modified chiral alkenes played the central role in the development of these molecular motors that were beginning to interest the MEMS people (MEMS stands for Micro-Electromechanical Systems…I am pretty sure).

In J Am Chem Soc. 2003 Dec 10;125(49):15076-86, ter Wiel MK et al. introduced the worlds smallest artificial light-driven motor using 28 carbon atoms and 24 hydrogen atoms.

Reprinted with permission from American Chemical Society: Journal of the American Chemical Society (Nov. 2003).

It also had a dramatic speed increase over the original designs, at a whopping 18s half-life at the fastest step. Even if it wasn’t going to be turning any relevant loads any time soon, it was a dramatic improvement over the original concept 4 years earlier. Still, even though some clever O-chem tricks made the motor better, it still operated on the same 4-step cycle that Koumura’s did back in 99′. Even recently, in Org. Biomol. Chem., 2008, 6, 507 – 512, DOI: 10.1039/b715652a, Pollard et al. report on substituting naphthalene moieties for phenyl moieties, in order to better control the speed of the motors, and to enable the design and synthesis of more complex systems.

Meanwhile, the MEMS people came up with interesting designs similar to this:

“A five micron wide resin structure, with a shape resembling a lawn sprinkler, rotates when illuminated by a laser beam. Tiny rotors like this one may someday power micromechanical systems (MEMS), or twist molecules to measure their mechanical properties.” Reported by: Péter Galajda; Pál Ormos, Applied Physics Letters, 8 January, 2001.

There was quite a bit of work done focusing on creating rotors that responded to laser light, although the practical applications of such devices aren’t as numerous as the devices that…well don’t require a coherent, collimated, polarized light beam to operate. Or at least they weren’t until Peidong Yang’s came around with his nanolasers.

Unfortunately, all of these motors share the drawback of being unidirectional. It was until recently, with Ikeda’s et al. paper in Angew. Chem. Int. Ed. 2008, 47, 4986, that a very cool and new method for directly converting light into mechanical work. Basically they drew on the fact that azobenzene derivatives, when incorporated into liquid crystals, can have an isotropic phase transition induced isothermally by irradiation with UV light to cause trans–cis photoisomerization, and that the reverse transition can be induced by irratiation with visible light to cause cis-trans back-isomerization. This photoinduced phase transition
led to successfully reversible deformations of liquid crystal elastomers containing azobenzene chromophores just by changing the wavelength of the incident light.

Now this by itself doesn’t a motor make. There was one large problem: the liquid crystal elastomer had to be made into a film or “belt” for a motor. However, the LCE film by itself wasn’t mechanically strong enough and tended to crack after short light irradiation at high intensities. So to fix this issue, they simply laminated the LCE film with flexible polyethylene sheets. I love this type of simple solution to what could have been a convoluted problem. This is very much like what Mitch and I tend to do.

*Note that they did do a study of increasing light intensity and it’s correlation to the mechanical force generated by the film. They found that “the maximum force and the increment rate of the generated force are enhanced with an increase of the light intensity.”*

So what happened? Well check this out:

Thats right. That is an actual light-driven motor NOT on the micro-scale. The diameter of those pulleys are 10mm on the left and 3 mm on the right. Sure it isn’t going to be competing in any races at the moment, but it could still be amazingly useful in the future. Light, straight to DC? That would be pretty darn awesome.

PS. Tomorrow is the first day of the experiment Mitch and I are running. Since we can, we will be broadcasting the first live cyclotron experiment out over the interweb. This may be one of the first live nuclear physics experiments broadcasted. Other then that, it is just cool. SO we will have it up all 24 hours as a “live vlog”.

Feel free; hell feel obligated to stop by, leave a comment, chat, ask questions, offer constructive or destructive criticism, whatever. Maybe ACS will pick this up as a new way to present new research: present it as it happens! Live!!!

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