Silver shells of 20 nm thickness have been deposited on silica particles of 200 nm diameter with narrow size distribution. Silver nanoshells dispersed in water exhibit a strong surface plasmon resonance band at 443 nm. This band was found to be very sensitive to rabbit immunoglobulin G antibodies, which were anchored on the nanoshells. These in turn could be utilized to detect the presence of small (approximately 5) to large numbers (approximately 10(9)) of Escherichia coli in water. The protocol presented here proves to be a specific, rapid, reliable, and inexpensive method to detect E. coli.
Plasmons are collective oscillations of electrons that have been exploited in many applications by manipulating and guiding light at resonant frequencies. The transition from understanding the origin and fundamentals of surface plasmon resonance to its many revolutionary applications has been intriguing. Advances in nanofabrication techniques over the last few years have led to variety of applications such as high-resolution plasmon printing, nanoscale waveguides, biodetection at the single-molecule level and enhanced transmission through sub-wavelength apertures, which are all examples of plasmon-assisted nanophotonics. Fundamental aspects of the surface plasmon resonance underlie enticing applications in nanophotonics.
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