Sunday, September 4, 2011

Molecular Motor

The Guinness World Record for the smallest electric motor currently stands at 200 nanometers, a human hair is about 300 times wider! Now Chemists at Tufts University's School of Arts and Sciences say they have developed the world's first single molecule electric motor, just 1 nanometer in diameter.

The molecular motor was produced when a butyl methyl sulfide molecule had been placed on a conductive copper surface and given an electrical charge. This sulfur-containing molecule had carbon and hydrogen atoms radiating off to form what looked like two arms, with four carbons on one side and one on the other. These carbon chains were free to rotate around the sulfur-copper bond.

The team determined that by controlling the temperature of the molecule they could directly impact the rotation of the molecule. Temperatures around 5 K, or about -450ºF, proved to be the ideal to track the motor's motion. The motor spins much faster at higher temperatures

Heather L. Tierney, Colin J. Murphy, April D. Jewell, Ashleigh E. Baber, Erin V. Iski, Harout Y. Khodaverdian, Allister F. McGuire, Nikolai Klebanov, E. Charles H. Sykes. Experimental demonstration of a single-molecule electric motor. Nature Nanotechnology, 2011; DOI: 10.1038/NNANO.2011.142

Further Reading
SI Unit Conversions
Temperature Conversions
Molecule Polarity
Intermolecular Forces
Molecular Mass (formula weight) Calculations
Percentage Composition
Empirical and Molecular Formula

Study Questions:
  1. Convert 200 nanometers to a diameter in
    • meters
    • micrometers
    • millmeters
    • decimeters
  2. Form the information in the article above:
    • What is the diameter of a human hair in nanometers?
    • What is the size ratio of the molecular motor to a human hair?
  3. Convert the following temperatures:
    • 5K to oC
    • 0K to oC
    • 100oC to K
    • 25oC to K
  4. On the molecular structure of butyl methyl sulfide:
    • identify the butyl group
    • identify the methyl group
  5. For a molecule of butyl methyl sulfide:
    • write the molecular formula
    • give the empirical formula
    • calculate the molecular mass
    • calculate the percentage composition

  6. Is butyl methyl sulfide a polar or non-polar molecule? Explain your answer.
  7. Do you expect butyl methyl sulfide to be water soluble? Explain your answer.

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