Diatoms: AFM Imaging of Natural Synthesis at the Nanoscale Application Note

Nanotechnology focuses on low-cost, high-throughput, directed synthesis of structures and devices at the nanoscale in order to address the requirements of a variety of applications. Microelectronics, for instance, offer more components per chip with faster response and lower power consumption. Nanometer-sized sensors for medical diagnostics, as well as magnetic storage systems of decreased size, also provide numerous advantages enabled by fabrication at the nanoscale. Although various synthetic strategies, including lithography, self-assembly, size reduction, and template deposition, have been developed to create devices at the nanoscale, these techniques do not exceed the accomplishments of natural systems. The study of natural systems, therefore, may offer valuable insight into how biology, through energy-efficient, low-temperature, mild reaction conditions, has developed mechanisms for reproducible nanoscale structure. Diatoms are an example of a natural system that utilizes such a mechanism. These unicellular photosynthetic algae, which are found in fresh water, salt water, and even in moist soil, extract silicon from orthosilicic acid in an aquatic environment to create an inorganic silica skeleton with nanoscale features. By removing the organic material from a diatom via acid cleaning with sulfuric acid, the silica cell wall is exposed and nanoscale features in the skeleton can be examined using high-resolution atomic force microscopy (AFM). From an environmental standpoint, diatoms are of particular interest to researchers. Because they are photosynthetic organisms, diatoms play an important role in global climate control by removing carbon dioxide from the atmosphere, thereby helping to keep greenhouse gases in check. As a major constituent of phytoplankton in the marine food chain, diatoms produce at least 40 % of the earth’s organic carbon each year. They are also responsible for producing roughly 20% of the oxygen we breathe, an amount equal to that produced by all of the earth’s terrestrial rain forests combined. Diatoms have existed since the Jurassic Period and deposits of fossilized diatoms, as diatomaceous earth (diatomite), are mined for commercial use in paints, abrasives, filters, and many brands of toothpaste