Asia-Pacific Forum on Science Learning and Teaching, Volume 7, Issue 2, Article 3 (Dec., 2006)
David D. KUMAR and Kimberly SCAROLA
Nanotechnology and Closed Captioned videos: Improving opportunities for teaching science to ESL students
Nanotechnology is one of the fastest growing fields in the world with considerable impact on all walks of life. Nanotechnology is an interdisciplinary technology for producing materials of extremely high precision and dimension of the order of 1-50 nm in diameter. As Rao (1999) described, “if you take a piece of solid matter (say a metal) containing an Avogadro number of atoms [6.022 x 1023 atoms in a gram mole of any chemical substance] and go on dividing it to smaller bits, you will ultimately end up with an atom of the substance. Before that, you will reach a stage of very tiny particles containing 100 to 10,000 atoms. Such particles with diameters of 1-50nm (10-500 Angstrom) are referred to as nanoparticles. Nanomaterials exhibit properties entirely different from bulk materials and constitute materials of the future” (p. 59). As bulk matter gets smaller in size, the ratio of surface atoms to unit mass increases (Table 1). (As an analogy, due to increased surface area finely powdered table salt crystals dissolve in water faster than the same quantity of bulk salt crystals.) A decrease in size facilitates the manifestation of more quantum effects in the form of optical, electrical, and magnetic properties (The Royal Society and The Royal Academy of Engineering, 2004).
Table 1. Size and Percent Surface Atoms
Particle Size Percent Surface Atoms 30 nm 5% 10 nm 20% 3 nm 50%
(Data Source: The Royal Society and The Royal Academy of Engineering, 2004)
Examples of nanotechnology include nanocrystals, quantum dots, and nanotubes. Combining two or more molecules of silica and aluminum, will result in the formation of nanocrystals used in commercial grade heat and rust resistant coatings. Nanocrystals of the order of 10nm in size with semiconductor properties are also known as quantum dots. Quantum dots take advantage of the size and arrangement of nanocrystals that affect the physical properties of materials such as color. For example, the color of nanogold is usually orange (<1nm) or red (3-30nm), depending on the size and arrangement of gold aggregates. Clear sunscreen containing nanosized zinc oxide particles allows the passage of visible light and absorbs ultraviolet rays. Bulk zinc oxide in regular sunscreen scatters visible light and appears white in color. Carbon nanotubes are allotropes of carbon (e.g., C60 Buckminsterfullerene) with diameters ranging from 1.2 nm to 30 nm exhibiting various chemical, physical, electrical and mechanical properties. They contain two-dimensional sheets of “graphenes” (graphites) rolled up into a tube with fullerene caps at the ends. Nanotubes are considered stronger than hardened steel and Kevlar. Carbon nanotubes are finding applications in a variety of technologies ranging from miniaturized telecommunication devices to water purification filters. Electronic fibers made of carbon nanotubes are potentially suitable for weaving in cell phone devices and computers as part of garments (Georgia Tech Research News, 2004).
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