Solar Cell Procedure:
1. Measure 0.5 g TiO2 powder in a clean mortar and pestle.
2. Add about 10 drops of dilute (1 M) acetic acid to powder and grind until you have a liquid-like paste.
3. Add 4-5 drops of surfactant and mix until all particles appear to dissolve or are completely suspended in the liquid.
4. Apply the TiO2 suspension to the conductive surface of a slide that has been masked with tape on 4 slides.
5. Smooth the paste with a glass rod until it is evenly spread as a thin layer on the surface of the slide. Be sure to remove bubbles. Remove tape. The slide should look like this, with the TiO2 layer in the center surrounded by clear glass on 4 sides.
6. Place slide in oven at 400˚C for 30 minutes. Slide will turn first brown and then white.
7. In the meantime, coat another conductive slide with carbon by passing the conductive side through a flame several times. The surface will appear black. Use a cotton swab to wipe carbon from the edges of the slide so that it covers the same area as the TiO2-coated slide.
8. Grind 2-3 raspberries on a watch glass. Add 1 mL deionized water and use a dropper to strain off the liquid; store liquid in a vial and refrigerate unused liquid.
9. After 30 minutes, remove TiO2 slide from heat. Allow to cool slowly about 20 minutes.
10. When slide is cool, use a dropper to add raspberry juice (about 6 drops) to surface of slide. Let sit for 5 minutes until the white layer turns a uniform dark purple color.
11. Wash excess raspberry juice from slide by rinsing gently first with deionized water and then with ethanol.
12. Air-dry slide and attach carbon coated slide so that the coated surfaces face each other. 4-5 mm of each plate should be exposed on both sides. The exposed ends will serve as contact points for negative and positive electrodes. Be careful not to scrape slide surfaces against each other.
13. Add electrolyte to slide by adding one or two drops at the exposed edge of a slide. The electrolyte will coat the slide surfaces through capillary action.
14. Wipe excess electrolyte from slides. The solar cell is now ready to test.