( are ball-shaped and consist of a core o...)Study shows nanoshells ideal as chemical nanosensors

are ball-shaped and consist of a core of non-conducting glass that is covered by a metallic shell, typically either gold or silver. The metal shell "captures" passing light and focuses it, a property that directly leads to the enormous Raman enhancements observed. Furthermore, nanoshells can be "tuned" to interact with specific wavelengths of light by varying the thickness of their shells. This tunability allows for the Raman enhancements to be optimized for specific wavelengths of light. Discovered by Halas at Rice in the 1990s, nanoshells are already being developed for applications including cancer diagnosis, cancer therapy, diagnosis and testing for proteins associated with Alzheimer's disease, drug delivery and rapid whole-blood immunoassay. In the current study, Halas and former graduate student Joseph B. Jackson, now with Nanospectra Biosciences, Inc., created thin films of nanoshells deposited atop plates of glass. Films with various densities were studied, as were films containing both silver and gold nanoshells. Through painstaking analysis, Halas and Jackson showed that the nanoshells' 10 billion-fold increase in Raman effect was due entirely to the interactions of light with individual nanoshells. This is markedly different from the pattern exhibited by pure gold or silver nanoparticle films. In that case, the Raman enhancement is an aggregate effect, due to the presence of localized "junctions" or "hot spots" between metallic regions of the metallic film substrate. The finding that individual nanoshells can vastly enhance the Raman effect opens the door for biosensor designs that use a single nanoshell, something that could prove useful for engineers who are trying to probe the chemical processes within small structures such as individual cells, or for the detection of very small amounts of a material, like a few molecules of a deadly biological or chemical agent.
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Source:Eurekalert


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