Eating Carbon Nanotubes

Fathi Moussa

Lon Wilson

Last year I covered Khodakovskaya et al.’s paper regarding the benefits of growing tomatoes in carbon nanotubes (CNT).^[CB] At the time I was concerned with the potential health risks associated from eating carbon nanotubes, but today in ACS Nano my concerns are alleviated. A paper from Lon Wilson’s and Fathi Moussa’s research groups discusses the effects from administering oral doses of carbon nanotubes (concentrations as high as 1g of CNT per kg body weight) to Swiss mice.^{[ACS Nano]} The authors summarize their work the best.

CNT materials did not induce any abnormalities in the pathological examination. Thus, under these conditions, the lowest lethal dose (LD_Lo) is greater than 1000 mg/kg b.w. in Swiss mice.

So feel free to eat all the CNTs you want in lab, assuming they are not functionalized, you do it only once, and you limit yourself to single walled carbon nanotubes. I think partly because the results of the oral administration of CNTs went without any interesting side effects to present, the authors also looked into what happens when you inject CNTs into the peritoneal cavity of mice.

The image on the left is the control while the image on the right is 14 days after injecting mice with CNTs at a concentration of 1g CNT per kg of mouse. Although it looks sickly, the mice injected with the high concentration of CNTs did not die. Well…, not from the CNTs anyways.

Link to paper: In Vivo Behavior of Large Doses of Ultrashort and Full-Length Single-Walled Carbon Nanotubes after Oral and Intraperitoneal Administration to Swiss Mice (ACS Nano)

Mitch

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This Message Will Self-Heal in 3, 2, 1…

Cassandra Fraser

Recently, Cassandra Fraser’s group reported on a very cool property, reversible mechanochromic luminescence, observed in an easy to make material.^[JACS] The molecule of interest is the difluoroboron complex of avobenzone (BF₂AVB), that UV absorbing molecule in your sunscreen minus the boron and fluorines.

In broad general language, mechanochromic luminescence describes the ability of some materials to change colors after scratching under UV light. The image below shows BF₂AVB coated on weighing paper (A), a cotton swab is used to write “Light” (B), the surface is hit with a heat-gun (C), the surface is ready to be written on again with a cotton swab (D).

The image brings up all kinds of creative ways to write secret messages, especially as the letters will fade over time even without using a heat gun. But before the CIA intelligence wonks in the audience get ahead of themselves the material doesn’t seem to be completely reversible at room temperature without annealing.

…even a small mechanical perturbation, such as a slight touch with the tip of a cotton swab, changed the green-blue BF2AVB film emission to yellow. The yellow emission gradually reverted back to green again at room temperature, with much faster recovery at elevated temperature. The written regions were no longer readable after annealing.

The field has, in short order, gotten tantalizingly close to a 100% reversible mechanochromic luminescent material at room temperature. Congrats!

Link to article: Polymorphism and Reversible Mechanochromic Luminescence for Solid-State Difluoroboron Avobenzone

Sam covered one of the first entrants to reversible mechanochromic luminescence a year ago: reversible mechanochromic luminescence is cool

Mitch

Update and Correction: Cassandra Fraser has corrected me, apparently the wording of the paper was just awkward to my ear, the material is fully reversible at room temperature!

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NanoPropulsion

Stephen J. Ebbens

Jonathan Howse

The current state of the art in nanopropulsion devices was recently reviewed by Ebbens and Howse in an article last Friday.^[SoftMatter] A short summary of the nano- systems is presented below with video action shots when I could find them.

The Whitesides

Catalyst: Pt
Fuel: H₂O₂
Propulsion: Bubble propulsion
Terrain: Aqueous meniscus
Max Speed: 2 cm/s
Mitch’s Name: The Karl Benz (since it was the first)
Article: Autonomous Movement and Self-Assembly

The Sen-Mallouk-Crespi

Catalyst: Pt
Fuel: H₂O₂
Propulsion: Self electrophoresis/Interfacial tension
Terrain: Settled near boundary in aqueous solution
Max Speed: 6.6 um/s
Mitch’s Names: The Ford Mustang of nanopropulsion. (It is a hot rod, get it?)
Article: Catalytic Nanomotors: Autonomous Movement of Striped Nanorods

The Jones-Golestanian

Catalyst: Pt
Fuel: H₂O₂
Propulsion: Pure self diffusiophoresis
Terrain: Free aqueous solution
Max Speed: 3um/s
Mitch’s Name: The Volkswagen Beetle
Article: Self-Motile Colloidal Particles: From Directed Propulsion to Random Walk

The Mano-Heller

Catalyst: Glucose oxidase and Biliruben oxidase
Fuel: Glucose
Propulsion: Self electrophoresis
Terrain: Aqueous meniscus
Max Speed: 1 cm/s
Mitch’s Name: The Komatsu Truck (because it is huge)
Article: Bioelectrochemical Propulsion

The Feringa

Catalyst: Synthetic catalse
Fuel: H₂O₂
Propulsion: Bubble/interfacial
Terrain: Acetonitrile solution
Max Speed: 35 um/s
Mitch’s Name: The F150 (has some exhaust issues)
Article: Catalytic molecular motors: fuelling autonomous movement by a surface bound synthetic manganese catalase

The Sen-Mallouk

Catalyst: Pt (CNT) (+cathodic reactions at Au)
Fuel: H2O2/N2H4
Propulsion: Self electrophoresis
Terrain: Settled near boundary in aqueous solution
Max Speed: 200 um/s
Mitch’s Names: The Ford Mustang GT (has more kick than the regular version)
Article: Bipolar Electrochemical Mechanism for the Propulsion of Catalytic Nanomotors in Hydrogen Peroxide Solutions

The Feringa v2

Catalyst: Glucose oxidase and catalse
Fuel: Glucose
Propulsion: Local oxygen bubble formation
Terrain: Free aqueous buffer solution
Max Speed: 0.2–0.8 um/s
Mitch’s Name: The Chevrolet Nova (more hot rod action)
Article: Autonomous propulsion of carbon nanotubes powered by a multienzyme ensemble

The Gibbs-Zhao

Catalyst: Pt
Fuel: H₂O₂
Propulsion: Bubble release mechanism
Terrain: Aqueous solution
Max Speed: 6 um/s
Mitch’s Name: The Rover
Article: Autonomously motile catalytic nanomotors by bubble propulsion

The Bibette

Engine: External magnetic field
Propulsion: Flagella
Terrain: Aqueous solution
Max Speed: unknown
Mitch’s name: The BMW Mini E (because there is no such thing as a magnetic car)
Article: Microscopic artificial swimmers

The Sagués

Engine: External magnetic field
Propulsion: Doublet rotation coupling with boundary interactions
Terrain: Settled near boundary in aqueous solution
Max Speed: 3.2 um/s
Mitch’s Name: The Smart ED
Article: Magnetically Actuated Colloidal Microswimmers

The Fischer

Engine: External magnetic field
Propulsion: Propeller drive
Terrain: Aqueous solution
Max Speed: 40 um/s
Mitch’s Name:
Article: Controlled Propulsion of Artificial Magnetic Nanostructured Propellers

The Najafi-Golestanian

Engine: Conformation changes in linking units
Propulsion: Time irreversible translations
Terrain: Free solution
Max Speed: ?
Mitch’s Name: The Eternal Concept Car
Article: Propulsion at low Reynolds number

Some devices that were not included by the authors of the review article, but should definitely be included in any list like this are below:

The Gracias

Engine: External magnetic field
Propulsion: Brute Force
Terrain: Aqueous solution
Max Speed: ?
Mitch’s Name: The Truck Cranes
Article: Tetherless thermobiochemically actuated microgrippers

Tetherless Microgrippers Grabs Tissue Sample – Watch today’s top amazing videos here

The Nelson

Engine: External electromagnetic fields
Propulsion: Flagella
Terrain: ?
Max Speed: 18 um/s
Mitch’s Name: The Tesla Roadster (simply awesome)
Article: Characterizing the Swimming Properties of Artificial Bacterial Flagella

Artificial Sperm – Watch more funny videos here

Link to Review Article: In pursuit of propulsion at the nanoscale

Mitch

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Close up Pictures of Stir Bars (with a Wide Angle Lens!)

A while ago, we had an offer from ASPEX, a microanalysis company, to provide a free SEM scan of an object of our choosing (that post being a follow up to our M&M mystery post).  The stir bar won and was sent away, never to return.

The results are in, and they are as cool as expected.  Analyst Ben Abraham captured several images of our very, very old stir bar, with corresponding chemical composition analysis.  The stir bar contains several elements, some expected, some not.  At various sampling points around the stir bar, carbon, oxygen, aluminum, silicon, iron, sodium, magnesium, sulfur, chlorine, calcium, zinc, fluorine, and chromium (!)  were identified.  Clearly, after several good years of wear and tear, the surface of the stir bar becomes irregular and several impurities remain on the stir bar.

As a follow up, it would be interesting to see what a brand new stir bar looks like.  Also, it would be interesting to see what two old stir bars look like after a lifetime of cleaning by only soap and water, versus one cleaned regularly with aqua regia or piranha mix or some such cleaning solution.  I don’t know how this analyzed stir bar was cleaned.  Most likely soap and water.

Make sure you click over to the ASPEX site to see the rest of the images and results.  You can also check out the rest of the site, including their desktop SEM.

PS, if you don’t get the joke in the title, watch this.

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The Birth of NanoAgriculture

Mariya Khodakovskaya

Alexandru Biris

There has been a lot of concern over the health effects arising from the burgeoning field of nanotechnology, David Barden covered one such paper focusing on nanotube production in Highlights in Chemical Science earlier this month.^[HCS] What hasn’t been as discussed are the potential health benefits of carbon nanotubes (CNTs). In a paper released yesterday in ACS Nano, Mariya Khodakovskaya & Alexandru Biris (+coauthors) found that tomato seeds grown in a medium of carbon nanotubes germinated and grew more efficiently than their control group brethren.^{[ACS Nano]} This result is spectacularly seen from the image below.

After 27 days of growth.

The tomatoes grown in carbon nanotubes weighed more, grew longer stems, and matured faster. The authors reason this is due to the carbon nanotubes facilitating water intake, however the evidence provided doesn’t prove this beyond a reasonable doubt. Although I wouldn’t recommend eating these tomatoes just yet, one could still use the increase in plant biomass and efficiency for biofuels and related projects.

Link to paper: Carbon Nanotubes Are Able To Penetrate Plant Seed Coat and Dramatically Affect Seed Germination and Plant Growth

Mitch

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Bismuth Photochemistry

Claus Feldmann

I love simple and elegant systems and that is exactly what Andreas Luz and Claus Feldmann have reported in the Journal of Materials Chemistry yesterday.^[JMaterChem] Luz & Feldmann found that when exposing a capped vial of a colorless solution of bismuth chloride dissolved in diethylene glycol to sunlight a black suspension forms. When this black suspension is exposed to air and shook a few times it turns colorless again. The process is shown below.

The chemistry involved is expected to be thus: light causes the solvent to reduce the bismuth to the metallic form, and subsequent exposure to air reoxidizes the system back to BiCl₃,

First Step

• Reduction:
• Oxidation:

In essence they have a solar and oxygen driven battery, a fact not lost on them because they go on to make a battery. They measure a few hundred millivolts out of their device, but without other data like current and power it is too difficult to judge the system wholistically.

There are many potential uses for the system, one off the top my head would be a visual method of detecting when oxygen has leached into your solvent or precious air sensitive materials.

Link to paper: Reversible photochromic effect and electrochemical voltage driven by light-induced Bi⁰-formation

Mitch

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Metallic Flagella

Bradley Nelson

The control of metallic flagella with magnetic fields is the subject of a recent paper by Li Zhang and Bradley Nelson.^[NanoLett] The synthetic approach is a top-down process, and an image of a pre-released flagellum is shown below.

Although typical bacteria like E. Coli are 1-2 μm long, this system is still a fascinatingly model of the motion of objects at low Reynolds numbers. The head of the artificial bacterium is composed of thin films of chromium, nickel, and gold. While the helical body is a composite of layers of indium gallium arsenide, gallium arsenide, and chromium. Motion is controlled by using three orthogonal electromagnetic coil pairs at 1-2 mT and a frequency of 5-35 Hz. A video of two of their flagella in action is shown below.

A couple of other videos showing the ability of the authors to steer the flagella are provided here: 1 flagellum, 3 flagella.

This system is a fascinating example of precise control of small devices that do not require outside chemical or photo sources. These systems have enormous promise and will likely comprise the type of motion the first nanorobots will utilize. One should couple this system to Gracias’ current generation of microgrippers for even more awesomeness.

Link to the article is here: Characterizing the Swimming Properties of Artificial Bacterial Flagella

Mitch

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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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