Nanotitania synthesis: The Preparation
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|
1.
|
Add 100-ml of anhydrous isopropanol [ (CH
3
)
2
CHOH ] to 2-ml of 2,4-pentanedione (C
5
H
8
O
2
) and stir covered for 20 minutes.
|
|
2.
|
Add 6.04-ml of titanium isopropoxide (Ti[(CH
3
)
2
CHO]
4
to the solution and stir for 3 hours.
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|
3.
|
Add 2.88-ml of distilled water and stir for another 2 hours.
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4.
|
The solution must then age for 12 hours, as the powder will precipitate out of solution at room temperature.
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5.
|
The remaining liquid should be decanted and the precipitate should be allowed to dry.
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6.
|
If you have access to X-ray diffraction, and some crystals on a slide, or a scanning electron microscope with an EDX device, analysis will provide identification. This will determine whether the product is titanium dioxide.
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Nanocrystalline Solar Cells: The Materials
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1.
|
(2) F-SnO
2
glass slides
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2.
|
Iodine and potassium iodide
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3.
|
Mortar and pestle
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|
4.
|
Air gun
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5.
|
Surfactant (Triton X-100 or dish washing detergent)
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6.
|
Colloidal titanium dioxide powder
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7.
|
Nitric acid
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8.
|
Blackberries, raspberries, citrus leaves
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|
9.
|
Masking tape
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10. Tweezers
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11. Filter paper
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12. Binder clips
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13. Various glassware
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14. Multi-meter
The photovoltaic cell has basically four main parts.
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|
1.
|
Nanolayer (nanotitania suspension)
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|
2.
|
Dye
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|
3.
|
Electrolyte
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4.
|
2 electrodes
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The nanolayer is the nanotitania. The dye can be juice extracted from raspberries, blackberries, or citrus leaves. The electrolyte is a solution of iodine/iodide. The two electrodes are conductive glass slides that have been coated with fluorine-doped tin oxide.
Preparation of the Electrolyte
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|
1.
|
Measure out 10-ml of ethylene glycol.
|
|
2.
|
Weigh out 0.127-g of I
2
and add it to the ethylene glycol and stir.
|
|
3.
|
Weigh out 0.83 g of KI and add it to the same ethylene glycol.
|
|
4.
|
Stir and sore in a container with a tight lid. This container should also be dark to retard light transmission through the glass.
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Preparation of the Dye
|
1.
|
Crush 5-6 berries in a mortar and pestle with 2-ml of deionized water.
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|
2.
|
Filter the solution with a coffee filter or any type of paper towel.
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Preparation of the Nanotitania Suspension
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|
1.
|
Add 9 ml (in 1 ml increments) of nitric or acetic acid (pH 3-4) to six grams titanium dioxide in a mortar and pestle.
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|
2.
|
Grinding for 30 minutes will produce a lump free paste.
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|
3.
|
1 drop of a surfactant is then added (Triton X-100 or dish washing detergent).
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|
4.
|
The suspension is then stored and allowed to equilibrate for 15 minutes.
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Image 03: forming a tape mold w/sample on a slide
Cell Fabrication Procedure
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1. After testing with a multimeter to determine which side is conductive, one of the glass slides is then masked off 1-2 mm on THREE sides with masking tape (Image 03). This is to form a mold.
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2. A couple of drops if the titanium dioxide suspension is then added and distributed across the area of the mold with a glass rod.
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3. The slide is then set aside to dry for one minute.
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4. After the first slide has dried the tape can be removed.
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5. The titanium dioxide layer needs to be heat sintered using a hot air gun that can reach a temperature of at least 450 degrees Celsius.
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6. This heating process should last 30 minutes.
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7. Allow the heat sintered slide to cool to room temperature.
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8. Once the slide has cooled, place the slide face down in the filtered dye and allow the dye to be absorbed for 5 or more minutes (image 04).
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9.
|
After the first slide has absorbed the dye, it is quickly rinsed with ethanol to remove any water and blotted dry with tissue paper.
|
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10. The two slides are then placed quickly in an offset manner together so that the layers are touching.
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11. Binder clips hold both slides together (image 05).
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12. One drop of a liquid iodide/iodine solution is then added. Capillary action will stain the entire inside of the slides.
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Image 04: face down in the filtered dye
Image 05: binder clips hold both slides together
Nanofabrication of Solar Cells equipment kit for each group containing:
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• small PV cell, at least 0.5v output, or several PV cells in series (found at most science supply companies and electronic stores)
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• several sheets of colored transparency film in various colors, including yellow and blue (office supply stores) Small pieces should be cut beforehand just to cover the PV cells.
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• 30 cm of thin electrical wire (use with alligator clips unless the meter leads have alligator clips on their ends)
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• DC ammeter (reads amps)
-
• DC volt meter
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• direct sunlight (desk lamp or flashlight could be substituted)
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• magnifying glass
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• aluminum foil
-
• protractor
-
• ice in sealed plastic bag
-
• goggles
Solar energy can be part of a mixture of renewable energy sources used to meet the need for electricity. Using photovoltaic cells (also called solar cells), solar energy can be used as direct current (DC) electricity or alternating current (AC) electricity or both. This electricity can be used at night by with a storage process, such as a battery. Batteries used for this purpose have a large storage capacity. Photovoltaic (PV) cells were developed in the 1950s as part of the space program.[8] They are made from silicon, a semiconductor. When light hits a PV cell, electrons move and travel along wires inside the PV cell, as electrons travel through the wiring in our homes. A PV cell changes sunlight into electricity by causing electrons to move toward the treated front surface of the cell. This creates an electron imbalance. When a connector like a wire joins the electron-reduced back and electron-increased front, a current of electricity flows between the negative front side and the positive back side. Photovoltaic systems are set up to maximize the Sun's light, and the system tracking angles can be changed for winter and summer, always facing the PV system south. Students are familiar with the PV cells used in most calculators. In fact, some students may wish to try some of the activities on a calculator PV cell for comparison. More possible future photovoltaic applications can be discussed with students.
