1. Treat yourself to some powdered doughnuts and herbal tea. The powdered sugar on US-style doughnuts contains titanium dioxide (TiO2 or E171). This is a semiconductor that can be used to make solar cells. To extract the TiO2 in a useful form, first scrape off all the powder and put it in a cup of warm water. Stirring this will dissolve all the sugar (there is a lot of it).
2. Running the whitish water through a coffee filter will leave behind a white blob -- this is the precious TiO2, along with some unwanted fat.
3. Because the fat is useless for solar cells, you'll need to put the residue in a hot oven for a few hours to vaporise it. The TiO2 remains as nanoparticles, each around 100nm wide.
4. Throw these particles into high-proof ethanol (vodka will do: use 1ml per doughnut) and shake.
5. Now conductive glass is needed (tough to find, but indium-doped tin oxide is best). With an eye dropper or syringe, drop ten layers of the nanoparticle spirit on the glass, allowing it to dry with each layer. Then put it back in the oven.
6. This is now a solar cell, but it will work only with UV light (the bad kind). Here is where the tea comes in. Leave the nanoparticle solar cell sitting in a cup of hibiscus tea for a couple hours, and soon it will have absorbed the colour, shifting its useful range from UV (useless) to visible light.
7. To collect energy from this solar cell, you'll need a counter-electrode. Take another piece of conducting glass and use a dark pencil to cover the surface with graphite.
8. To get your electricity to your counter-electrode, a generous amount of iodine in high-proof alcohol works well as an electrolyte. Use one part alcohol to three parts Lugol's solution -- available from health stores and aquarium suppliers.
9. Cut a hole in some thin plastic or tape to use as a spacer, and place it on the nanoparticle cell. Drop some electrolyte on top, and quickly sandwich the two electrodes together with some bulldog clips.
10. You're done! A multimeter connected to both of the conducting electrodes should show about half a volt when in the sun.
This article was taken from the March issue of Wired UK magazine.
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