Tuesday, November 25, 2008

Our Self Assembled Universe

Often, after a presentation about the exiting developments in nanotechnology, a common question I am asked is "How are things made at the nanoscale?"

This is an insightful question because the person asking it has understood that at the nanoscale, where are working with molecules that are 80,000 times smaller than the diameter of a human hair, the idea of moving and attaching one molecule to another would be a tedious if not impossible task.

Other, more specific questions are:
"Are there nanomachines that build these nanomaterials?"
"How do we position the 60 carbons in a buckyball to get that soccer ball shape?"
"How long does this process take?"

The rather simple answer to these questions is that under certain conditions many molecules just self assemble - they make themselves. This process of self assembly is very fast and is analogous to molecules sticking together. Rather than forming covalent bonds, self assembly exploits weaker bonds (like hydrogen bonding) but because there are many many bonds, these self assembled structures can be very strong. Examples of naturally occurring self assembled structures include the collagen that makes up our bones and hair, DNA that codes our genes, and proteins - the stuff that makes us alive.

Self assembly happens at a very fast pace, at the speed of an electron, and millions of molecules can attach in very specific fashions using simple rules. Yet the result can be very intricate structures (like snowflakes) and new materials like buckyballs. To make buckyballs, we just have to blast carbon monoxide or another carbon source into a furnace that is at the right temperature and pressure for the carbons to take on its soccer ball shape because carbon is obeying some simple thermodynamic rules to minimize its energy. As nanotechnologists, our job is to understand what these rules are and try to create the environmental conditions that will promote nature's ability to build itself. We live in a self assembled universe.

Sunday, November 23, 2008

"My mother measures stuff when she makes a cake. How do you measure the atoms and molecules when you make a nanoproduct? Do you follow a recipe?"

This was a question poised to me by Science Weekly for an issue on Nanotechnology. I was thinking about it yesterday as I watched a CBS film crew record a synthesis procedure for Nanorust in our university cafeteria. Nanorust is a technology that may be used to clean water because the nanometer-sized iron oxide particles bind to toxins like arsenic and then can be removed with a low powered magnetic. The procedure to make nanorust was modified from a traditional laboratory protocol to a kitchen cooktop method by substituting household products like olive oil and measuring cups for the chemicals and tools were normally order specifically for the laboratory. The goal of this Nanorust project is to freely provide the recipe to individuals or companies in developing nations so that they can use this nanotechnology to solve one of the most important global challenges: clean water. And yes, it is a recipe. The difference between kitchen chemistry and laboratory chemistry is often just the language we use (a chemist might say “now we add the water soluble fatty acids” while a cook might just say “I need some soap”) and the tools that we use (a chemist might use a transmission electron microscope to look at their products while a cook might just use their eyes, nose and yes, tongues).
Here is the Nanorust protocol
Olive oil and rust for magnetite nanocrystals
Cafer T. Yavuz
A. Soap making Process

1. In a crystallization dish or a similar container, weigh 100 g. of the liquid oil (if not liquid gently melt it and keep as melted).
2. In a 50 mL vial (or a cup) weigh 15 g. of crystal drain opener (or caustic soda, or sodium hydroxide, or potash).
3. Add 30 mL of tap water and shake (or stir) until all solid is dissolved (CAUTION: solution gets hot!). While still warm pour it into the liquid oil.
4. Stir with a spoon (or a magnetic stirbar) for about 15 minutes (or until tracing occurs – tracing is the visible tracks of stirring).
5. Let it sit open to air in a hood (or ventilated area) to dry and cure for couple days (or a week).

B. Oleic acid from soap with commercial vinegar

1. Weigh the dried soap (i.e. 60 g.)
2. Check the vinegar’s acidity (i.e. 9%)
3. Use 1 mL of acid for every gram of soap (i.e. 60 mL of acid, 650 mL of commercial vinegar with 9% acidity)
4. combine them in an erlen (or a big glass/steel jar)
5. Heat and stir them until all the chunks are dissolved (it may boil – takes about 15-30 minutes)
6. Turn off the heating and cool the solution down. You should see the two layers separating from each other.
7. Separate the top yellowish layer by a separatory funnel (or a spoon, syringe, anything that works) into a clean glass/steel jar.
8. Heat and boil the yellowish cloudy solution until it clears
9. Cool down and store as Fatty Acid Mixture (FAM)

C. Magnetite nanocrystals from rust and fatty acids

1. Collect the rust by shaving off of the rusted tools.
2. Grind the rust into fine powder.
3. Mix 1 grams of rust with 20 grams of fatty acid mixture in a glass or steel container (erlen or pan) and provide stirring.
4. Cover the top of the container with a loose cap for proper ventilation (reaction smokes and steams). This method produces 50-90 nm nanocrystals but if you want to make them smaller (~15-20 nm) you have to use a steam/pressure cooker instead.
5. Start heating and timing. It should be cooked at around 2 hours (or less) until complete/dark black solution with little or no smoking.

D. Transferring oily magnetite nanocrystals into water

1. Grind 10 grams soap (made above) into a 100 mL of water
2. Boil the mixture to dissolve while vigorously stirring (takes about 20-30 minutes)
3. Filter off the undissolved soap
4. Take a spoonful (3-5 grams) of black waxy mixture into 40 mL of the soap-water solution
5. Stir and boil the mixture for 30 minutes (add more water if significant loss of water observed)
6. Filter the solution to get rid of unreacted magnetite
7. Magnetically separate the nanocrystals (time varies: smaller crystals need overnight or couple days, larger ones need couple hours)
8. Once on the magnet gently swirl some water on the crystals to clean them
9. Redissolve in water (or ethanol, etc.)

Sunday, November 16, 2008

What is this nanoed blog about?

On this blog, I hope to post answers to questions that I am frequently asked about nanoscience and engineering and share some the research findings on nanotechnology. I will also discuss science education in general - some of the problems and potential solutions as well as interesting articles and science activities that I come across.

For example,Sir Harry Kroto, who won the Nobel Prize in 1996 with Dr. Rick Smalley and Dr. Robert Curl, has a great video where he discusses the discovery at http://tinyurl.com/6q2jxm