Science / Technology - Colloquium
Friday, February 22, 2008
4:00 PM-5:00 PM
Olin Hall
107
Fluorescent and plasmonic nanoparticles are increasingly used in cellular imaging applications because they fluorescence and scatter light so brightly that single nanoparticles can be observed over extended periods without bleaching. In addition, nanoparticles can act as a platform onto which many components can be loaded. By loading new components onto nanoparticle platforms, new properties are created with diverse applications. For example, using vapor deposition to coat a fluorescent nanosphere with a hemispherical half-shell of opaque metal breaks the nanosphere's optical symmetry so that it reflects and fluoresces light in an orientation-dependent manner. If the nanoparticle is magnetic, it aligns with an external magnetic and rotates to follow a rotating magnetic field.
The particle blinks as it rotates through bright and dark orientations. The blinking signal from these magnetically modulated optical nanoprobes
(MagMOONs) can be separated from unmodulated autofluorescence backgrounds.
The blinking frequency provides a measure of the local viscosity, while the fluorescence spectrum provides a measure of the concentration of chemicals that interact with the fluorophores in the nanosensors.
Plasmonic chemical nanosensors are another example of multifunctional nanoplatforms. In addition to serving as brightly scattering spatial labels, silver nanoprisms exhibit exquisite sensitivity to changes in local refractive index. When molecules adsorb to the nanoparticle surface, the resulting increase in local refractive index causes the nanoparticle extinction and scattering spectrum to redshift. Tracking this redshift in real-time facilitates the study of molecular binding kinetics and interactions. Overall, combinations of top-down and bottom-up nanofabrication processes provide control over nanoparticle optical, magnetic, and chemical properties allowing integration of features for a wide range of biomedical applications.
Cost: FREE
Sponsored by: WPI Physics Department, Dr. Stephan Koehler
Suggested Audiences: College
E-mail:
sak@wpi.edu
Phone: 508-831-5090
Last Modified: January 31, 2008 at 3:23 PM
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