Do you know him by the white speck on his nose oron the back. But one day, a white ointment that protects your skin from sunburn may begin to produce electricity on the roof of your house or car. Many people know that zinc oxide is a key ingredient in sunscreen and diaper powder. But it also acts as a semiconductor that can be used in new types of solar cells, optical gas sensors and ultraviolet lasers, as well as in the production of hydrogen gas, which could replace oil as a fuel source for cars and trucks.
Scientists coated a smooth surface with oxidezinc and heated to 400 degrees Celsius. Then they covered the first layer with polymer and used an electron beam to punch holes in it. Zinc oxide and patterned mask were then placed in a bottle of zinc salt and other chemicals dissolved in pure water. Then the solution was heated. Zinc and water reacted only inside the holes, so nanorods formed only in these holes. After removal of the polymer, a forest of nanorods remained.
Growing nanorods according to a certain pattern,scientists can create photonic crystals - special structures that capture light. Photonic crystals can be used to create more efficient ultraviolet lasers or optical gas sensors that can change color when a specific gas is present.
Such a sensor may, for example, detectdangerous amounts of carbon monoxide. Or it can be used to detect trace gases that should not be, for example, ethylene in fruit storages, since the presence of ethylene can spoil the fruit, says Hassanpur.
Zinc oxide nanorods will be a valuable assetfor gas sensors, since they can change in a predictable way when exposed to various gases. Although such sensors can be created from nanorods that are not located in a particular pattern, careful design of nanorod positioning is necessary to create more sensitive devices.
Zinc oxide nanorods can beused to create more efficient solar cells and cheap hydrogen fuel cells. Since zinc oxide absorbs energy from sunlight, the placement of nanorods in water causes the absorbed energy of the sun to break bonds between oxygen and hydrogen atoms in water molecules to form hydrogen gas.
This hydrogen can be collected and then used.as fuel, ideally to replace gasoline or other fossil fuels. By conserving hydrogen, engineers could easily transfer it as fuel to a consumer, such as a hydrogen automobile.