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22 April 2016 Enhancement of scattering from nanoparticles using substrate effect
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Proceedings Volume 9724, Plasmonics in Biology and Medicine XIII; 97240V (2016)
Event: SPIE BiOS, 2016, San Francisco, California, United States
Scattering cross-section of metal nanoparticles is enhanced due to Localized Surface Plasmons Resonance (LSPR) permitting the observation of single metal nanoparticles as small as 40 nm using dark-field microscopy. Single particle resolved measurements allow the study of reactions happening on the nanoparticle surface involving an ultra-low number of reactant molecules to understand stochastic effects in reactive systems. Here we report a method to enhance the intensity of resonantly scattered light by using appropriately designed substrates. Specifically, we show that by using a multi-layer dielectric substrate with its high reflectance window spanning the LSPR resonance position, one can increase the intensity of scattered light by nearly an order of magnitude. We took three substrates namely Silicon, glass and the multilayer dielectric mirror. Disk shaped gold nanostructures with sizes ranging from 80 nm – 300 nm were fabricated using electron beam lithography on all three substrates. Sizes of individual nanostructures were determined by atomic force microscopy (AFM) and the dark-field image of each nanostructure was taken with an optical microscope. It was observed that the intensity of light scattered by single nanparticles was roughly an order magnitude larger than that from Silicon and glass substrates. We used a numerical scheme based on Discrete Dipole Approximation to computationally validate our results. The numerical results matched the experiments quite well. The substrate enhanced scattering signal will useful to improve the signal to noise ratio in single particle resolved measurements.
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Krishnendu Chakraborty, Abhay Tiwari, Manoj M. Varma, and Murugesan Venkatapathi "Enhancement of scattering from nanoparticles using substrate effect", Proc. SPIE 9724, Plasmonics in Biology and Medicine XIII, 97240V (22 April 2016);

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