The family of carbon nanotubes is large. There can be single walled carbon nanotubes (SWNTs), which are like a rolled up sheet of graphene - a monolayer of carbon bonded into a tubelike structure or they could be multiwalled carbon nanotubes, which have concentric layers of these graphene tubes. These carbon nanotubes can have large aspect ratios (length to width) or could be cut into ultra short carbon nanotubes. In fact, carbon nanotubes come in thousands of different molecular weights and isomers.One of the most interesting characteristic of Carbon Nanotubes is how dependent the material properties are on small changes in structure. For example, small changes in the way that the carbon atoms align results in the difference between the SWNT being a metal or a semiconductor. This difference in the way the carbons align is called Chirality. Here is an easy way to demonstrate what chirality is. Take a transparency sheet with graphene's structure copied on it and connect two ends to form a cylinder. That is the model of one kind of carbon nanotube with the chiral index of (n, m) where n is the number of carbon atoms across the grid (at the center of each hexagonal structure on your transparency) and m would be zero since you havent moved down the matrix. If you want to make another kind of nanotube, you need to twist the graphene transparency and make a new tube that has a constant diameter. Scientists discovered an odd trend. When (n-m) is divisible by 3 (the product is an integer) then the SWNT is metallic, otherwise it is a semiconductor. Small changes in the arrangement of carbon atoms affects the electronic nature of these materials.Make your own Carbon Nanotube by printing out this graphene sheet and trying different rollups.  Notice how the diameter changes.  See More

I am writing this blog as I procrastinate writing the final exam for myBioNano class this fall. During the class, student picked current peerreviewed journal articles and presented them in a short Pecha Kuchaformat. This means presenting 20 PPT with 20 sec per slide. Topicsranged from applications of gold nanoparticles for lung cancerdetection, the effects of feeding Buckyballs to mice, and antimicrobialproperties of nanosilver. Students in the class were required to readthe papers chosen by their classmates and write up a list of questions(collected for a grade). I thought the format worked out well. Veryshort presentations followed by fairly animated dialogue (for a 9:30 AMclass).Since the students chose the articles, some were veryfamiliar to me but some were quite unexpected. One of the moreinteresting topics that I learned about was making tectosquares thatare RNA sequences that self assemble into ladder-like nanostructures.In the paper listed below, they used nanogold particles to quantify thespacing. Very Elegant. Controlled Spacing of Cationic Gold Nanoparticles by Nanocrown RNAAlexeyY. Koyfman,§,† Gary Braun,§ Sergei Magonov,‡ Arkadiusz Chworos,§Norbert O. Reich,§,† and Luc Jaeger*,§,† J. AM. CHEM. SOC. 2005, 127,11886-11887See More

I woke up this morning feeling maybe smaller, maybe less energized. Infact, a new study in Nature calculates that the proton is 4% smallerthan previously thought or as this Scientific American headline reads"proton shrinks in size"http://www.scientificamerican.com/article.cfm?id=proton-shrinks-in-size.So perhaps my jeans really do fit better today because my protons aresmaller than they were last week. What do these studies imply?Does this mean that we don't understand the basic structure of the atomas well as we thought? Does a 4% difference matter? Perhaps therewas a calculation error and this newest technology that was used in thisexperiment is just off somewhat. Since now the Rydberg constant wouldnow be different, does this through a glitch into the whole concept ofquantum theory? Should we care? While protons are measured infemtometers are a lot smaller than nanometers (1000times), all matter iscomposed of protons, electrons and neutrons. So when someone says yourprotons are smaller than they thought, you should take note.See More

just put some Saran wrap on leftovers. Was it Saran or some cheaperknock off? Does it matter? Probably not, since my family will eat ittomorrow regardless (they are not picky). However, if you were packing aproduct to be shipped around the world, like an expensivepharmaceutical product or even an inexpensive snack, you would care.Time is money - esp. when it is sitting on a store shelf. Howdoes this relate to the esoteric term, nanocomposites? The cause of mostfood spoilage is are either microbial or chemical- specificallyoxidation. Microbes are relatively large (micron sized), so plasticfilms easily act as a barrier. A molecule of oxygen, however, is verysmall (more than 1000 times smaller than a microbe) and can betransported through plastics (also known as polymers) easily. Thistransport or permeability depends on the solubility of oxygen (or howwell it dissolves) in the polymer and its ability to diffuse or movethrough the polymer. Different polymers have vastly differentgas transport properties and cheap polyethylene (Glad wrap) is much morepermeable to gases than polyvinylidene chloride (Saran wrap). However,if you look at the packaging after you finish those chips from thevending machine, you will see that they have an additional layer ofaluminum foil that really prevents gas transport. Recently ithas been found that when polymers are sequentially prepared intonanometer thick layer cakes, the barrier properties of the materialsimprove. Because polymers are glass-like structures, they tend tochange or relax over time. This relaxation basically allows the polymermolecules to get closer together and this more compact structure blocksthe transport of gas through the material. So controlling thenanostructure of polymer films could increase the shelf life of productsand potentially eliminate the need for the expensive aluminum layer inpackaging. More specifically, a composite in a combination ofmaterials. A polymer with nanosized additives would be called ananocomposite. Adding nanosized particles to polymers can increase itsstrength, decrease its weight and improve its barrier properties (or howwell it blocks oxygen). The nanosized material could be relativelyinert clay materials or potentially antioxidant or antimicrobialparticles.While many people think of packaging as eithersomething for marketing or something that is waste issue, and indeedboth are true, good packaging prevents food spoilage and protects theactivity of pharmaceutical products. Every day we pack a lunch, saveleftovers, open a container from the store. Whether we like it or not,packaging is a part of our everyday lives.See More