My Summer Job

So, I started this summer with a poor idea of what I was to be researching and an even poorer conception of how I was going to go about actually doing it.

In simpler terms, my project begins with developing a democratic means of identifying carbon nanotubes. In the lon tem the project will develop more to studying the chemisty of the nanotubes. The research results will hopefully be of use by Smalley and his group as the quest on to produce, cut, grow, and spin the nanotubes into the magic material of our future.

A brief digression on carbon nanotubes:
Best of luck getting a good introuction to carbon nanotubes by google. What follows is a basic introduction but understand that there is so much more that is truly fascinating. Carbon nanotubes are essentially a strectched bucky ball (C_60). To make a good model, draw on a sheet of paper an interconnected mesh of hexagons. This two dimensional representation is called the "graphene sheet" and is the starting point for all the carbon nanotube theory. A nanotube is made by choosing two points and rolling the sheet so those two points connect. Through a simple means of numbering we can identify a nanotube by two vectores (n,m). These vectors determine the nanotubes chirality (description of its symetry) and a plethora of other properties. There are two particularly important species of nanotube: the armchair and zig-zag nanotubes. Thier importance arises from their achirality (actually being very very symetric istead of a degree of asymetry) and their physical properties such as high strength and conductivity. Armchair tubes have n=m so (n,n) is a armchair; zig-zag tubes have m=0 so (n,0) is a zig-zag tube.


Dr. Wiessman and others in the Center for Nanoscale Scence and Technology (CNST) at Rice, developed an ingenious method to identify many kinds of nanotubes via IR florescence. However, IR spectroscopy and Raman spectroscopy are an interesting balance. In general, a molecule that gives off lots of IR florescene gives reletively little raman signal and visa versa. The Wiessman group method is very fast and effective for most tubes, but not the armchair or zig-zag. My project aims to use UV Raman spectroscopy to measure the vibrational breathing modes of the nanotubes. Each different nanotube should have a characteristic Raman signal.

At least thats what I think I am aiming to do.

Currently, I am working to make sure that the experimental setup is working up to a known level of efficiency and accuracy. This is achieved by recreating the results of Erik Lotfi, a recently graduated graduate student of the Kinsey Lab group. His experiment was to look at the Dissociative Resonance Raman Spectra of ozone. This is the study of the physical processes that occur in the upper atomosphere as the ozone layer protects us from the UV rays of the Sun.

The experimental set up is as follows: an eximer laser to pump a tunable dye laser (this set up gives us the flexibilty to choose precisely our wavelengths), then an optical set up that uses a Beta - Barriam Borate crystal to double the frequency of the light (interesting physics in that!). Beyond that is all details of sample holders and computer data aquisistion.

I'll add more to this blog about developments in my experiment and further explanations as they develop.