Use of Chloroplasts and Anthocyanin in Photovoltaic Cells Hunter Porter, Brian Tetreault , and Jim Bidlack

1. Use of Chloroplasts and Anthocyanin in Photovoltaic Cells Hunter Porter, Brian Tetreault, and Jim Bidlack Department of Biology, University of Central Oklahoma, Edmond, OK 73034 Materials and Methods Solar Cell Construction Cells were constructed from mostly hand-made components, beginning with two glass plates coated with SnO. Coated plates were then taped down, leaving a window of space in the center. A TiO2 solution, consisting of 1.5 g of titanium(IV) oxide nanopowder, 3 mL of dilute acetic acid solution, .75 mL of Triton-X 100, and .3g of p-dihydroxybenzene, was then added to the cell and made into a smooth layer using a glass rod. Coated cell sides were then fired at 500 degrees Celsius to anneal the TiO2 and create a nano-crystalline structure. Cathodes were then made by coating an alternate SnO glass plate with a graphite lattice. Treatment cells had a specific solution applied to the white titanium layer on the anode, while controls received no coloration. A drop of Lugol’s solution was added as an electrolyte. Glass plates were lastly fastened together using rubber band, finishing the cell construction. Treatment Isolation and Application Multiple things were used as treatments, but chloroplasts isolated from spinach (Spinacia oleracea) were the main treatment condition. Chloroplasts were isolated by homogenizing 5 grams of finely diced spinach leaves in a sugar grinding solution, which was then centrifuged multiple times to pellet chloroplasts and allow removal of other cell parts. Chloroplasts were examined under light microscope to ensure limited damage and lack of free pigments (Fig. 1). Figure 1 : Chloroplast Extraction – 400x magnified Chloroplasts were then applied to cells using a drip method, depositing roughly 50 microliters of solution at a time and leaving to dry. Drip-coating was done daily for a week. The applied chloroplasts thoroughly colored the white titanium substrate (Fig. 2). Figure 2 : TiO2 treated with chloroplast solution – 400x magnified An aqueous anthocyanin solution was also used as a treatment, obtained from either purple heart (Tradescantia pallida) or from red cabbage (Brassica oleracea). Purple heart anthocyanin extractions were performed by boiling leaf tissue and then filtering out other materials, while red cabbage was pureed and then filtered. Both extracted solutions were boiled down to increase pigment concentration until a saturated solution was formed. Anthocyanin was applied to cells via the same drop method as the aforementioned chloroplast treatments. Some cells were also coated by soaking for a period of 3 days. Anthocyanin produced either reddish-purple (purple heart) or blue (red cabbage) colored substrates. Electrical Measurement and Recording Constructed solar cells were attached to a voltmeter by clips and tested for output in millivolts (Fig. 3). A circuit was then created to test power output using a rheostat to apply variable resistance and power curves were generated for each cell (Fig. 4). The average Pmax corresponding resistance was then chosen as the standard resistor for all trials. Data recording used a random block design, assigning cells randomly to one of two recording racks. The racks were affixed with 100k ohm resistors (determined as described previously), wires to a computer recorder, and clips to hold PV cells in place (Fig. 5). Voltage was recorded for a period of 30 days using Pico Log Recorder. Figure 3 (above):Voltmeter reading from cell Figure 5 (right): PV cells on testing rack Abstract An experiment was designed to determine the viability of using chloroplasts and concentrated anthocyanin in dye-sensitized solar (photovoltaic) cells. These cells were made using glass plates with a film of tin oxide; one coated with titanium dioxide embedded with pigment to serve as the anode and another coated with graphite to serve as the cathode. Anodes were soaked with chloroplasts extracted from spinach (Spinaciaoleracea), or anthocyanin derived from the leaves of purple heart (Tradescantiapallida) or anthocyanin from red cabbage (Brassica oleracea), in order to embed pigments within the titanium dioxide. A KI/I2 electrolyte solution was sandwiched between the anode and cathode cells and opposing ends were connected to a voltmeter which recorded output over time using a Pico Recorder. Use of chloroplasts in anodes showed promising results, with some cells yielding over 800 millivolts per cell, whereas application of concentrated anthocyanin to anodes produced an average of 400 to 600 millivolts. Both chloroplasts and anthocyanin treatments produced voltages that were significantly above control counterparts, which averaged about 100 millivolts per cell. A preliminary longevity test of anthocyanin showed a voltage increase over a period of 15 days. Longevity tests for chloroplast and concentrated anthocyanin cells are currently being investigated. Chloroplast Cell Power Curve Figure 4 : Power Curve Example – Chloroplast Cell Introduction “Gratzel’s cell is a remarkable innovation [which] … closely mimics natural photosynthesis” (Jayaweera, et al. 2007). Other projects have been conducted, such as using the energy generated by microorganisms, in sea water, breaking down carbon in the sediment to create electricity (Tender, et al. 2002). Dye-sensitized solar cells (DSSCs) have been proven to harness solar energy into useable electricity. The University of Central Oklahoma has specifically focused on creating DSSCs using organic pigments instead of man-made pigments. However, the application of living cells performing photosynthesis to a DSSC and its effects still require testing. The goal of the research is to determine whether or not living photosynthetic energy can be used to create more efficient DSSCs and if those cells can be maintained over a long period of time. Results and Discussion Quantitative Results While long term tests showed no significant difference (p>.05), voltage output difference between controls and anthocyanin cells at construction were significant (p<.05). Also, differences between chloroplast cells and controls at construction were significant (p<.05) (Fig. 6). Discussion Half of cells constructed (treatments; controls are assumed to follow) did not function. The difference was starkly noticeable in treatment cells; however, the differences were not noticed in controls. The reason for malfunction has yet to be ascertained. It is suspected to be a result of the cells being handmade and thusly subject to considerable human error on construction; more testing is required to confirm the hypothesis. A more easily repeatable procedure is under development, but was not ready in time for these trials. Titanium(IV) nanopowder forms large conglomerations which effect the ability to produce a quality nanocrystalline film. Options for higher quality particles are being investigated. Chloroplasts applied to factory made cells with less porous titanium structures did not adhere well and resulted in weak coloration. This prompted the use of homemade cells with potentially more human error over their mass produced alternative. Determining why roughly half of the created cells do not function is a priority. In order to advance research in this field, that level of failure is unacceptable past the early research phase. Many other organic pigments could be tested, as well as chloroplasts from different plant species or even cyanobacteria. So far, testing with other green vegetation has shown large differences in chloroplast concentration upon extraction. However, this data is not complete and requires further observations. Figure 6 : Table 1 – Data from cell construction Acknowledgements Funding for this project was provided by a Research, Creative, and Scholarly Activities (RCSA) grant from the Office of Research and Grants at the University of Central Oklahoma. Literature Cited Bidlack, James E. 2012. Plant Physiology Laboratory Manual Spring 2012. Jayaweera, P.V.V., Perera, A.G.U., Tennakone, K. 2007. Why Gratzel’s Cells Work So Well. InorganicaChimicaActa. Tender, Leanord M., Reimers, Clare E., Stecher III, Hilmar A., Holmes, Dawn E., Bond, Daniel R., Lowy, Daniel A., Pilobella, Kanoelani, Fertig, Stephanie J., Lovley, Derek R 2002. Harnessing microbially generated power on the seafloor.