Lisa Jo Beard
Fairview High School
Honors Chemistry, Agricultural Chemistry, Advanced Placement Chemistry, Physics, Advanced Placement Chemistry

Dr. Kane Jennings, Polymer Thin Films Lab

My lab experience in Vanderbilt’s Polymer Thin Films lab was an extension and continuation of the two year summer research conducted by former RET teacher Susan Lee who helped develop a wet electrochemical cell that produced a measureable current when a light was applied to an electrode coated with Photosystem 1 (PS1).  The science behind this accomplishment is due to the energy from a light source (such as the sun) exciting the electrons in the p-700 molecule.  It is named p-700 because the absorption of light on the PS1 molecule occurs at 700 nm.  Once excited, the p-700 molecule loses an electron and becomes p-700⁺.  It is this phenomenon that is being explored as a possible alternative energy source because of the exponential potential of harvesting the sun’s energy at an economically fiscal price.

During my research experience, I took the results of the PS1 wet cell to try to create a dry cell which would give comparable results.  My first dry cell design included copper plating a gold plated silicon wafer, depositing silver on the site designated for PS1, adding a polymer as an insulator that would grow on the copper only, evaporating PS1 on top of the silver, and adding a conductor on top.  This first dry cell did not produce impressive results.  My second dry cell design was depositing silver on the gold in the place PS1 was evaporated, incorporating the use of a hydrogel that had a mediator solution to help in the transfer of electrons in the PS1 to the conductor.  I used different concentrations of mediator solutions in each trial to compare mediator effectiveness.  The results improved, but still were not impressive.  My third dry cell design was a “wet-dry cell” design.  I deposited silver in the assigned spot for the PS1 evaporation.   I affixed a silicate polymer thin film on top of the gold plate as an insulator.  A hole was cut out of the polymer where the PS1 was deposited.  This hole created a cavity in which a mediator solution was injected once the conductor was attached to the top.  This cell produced promising results!

In addition to researching PS1 dry cell design, I also investigated the effectiveness of a modified extraction process to increase the yield in the PS1 extraction from spinach.  I cut spinach in small pieces avoiding the veins until I had a 50.000 gram sample.  The sample was placed in a blender with a buffer that aided the reduction process of PS1.  The sample was then centrifuged and the liquid in the top layer was discarded.  A column buffer was added to a 3 cm diameter column that was packed with a significant increase of hydroxylapatite from previous PS1 extraction procedures.  This modification was made to find out if this will increase PS1 yield.  It is important to note that the column buffer aids in the process of oxidizing the PS1.  The PS1 was collected and stored in a -80C freezer.  The result of this process was a significant increase in PS1 yield, however, a possible increase contamination of chlorophyll in the end product.

I plan to use my eye awakening experience to teach the connection between photonic energy, photosynthesis, and electrochemical cells.  The curriculum I have design has students using spinach to design an electrochemical cell that will power a calculator.  This engineering connection is to spark enthusiasm and ingenuity toward creating alternate energy sources in our world.