Ag@SiO2 Core-Shell Nanostructures: Distance-Dependent Plasmon Coupling and SERS Investigation.
Enhancement of Raman signals of pyrene due to the enhanced electric fields on the surface of silver nanoparticles has been investigated by controlling the thickness of the silica shell. Dimeric nanostructures having well-defined gaps between two silver nanoparticles were prepared, and the gap size (d) was varied from 1.5 to 40 nm. The molecules trapped at the dimeric junctions showed higher Raman signal enhancements when the gap was less than 15 nm due to the presence of amplified electric field, in agreement with our theoretical studies. The experimental Raman enhancement factors at the hot spots follow a 1/d(n) dependence, with n = 1.5, in agreement with the recent theoretical studies by Schatz and co-workers. Experimental results presented here on the distance dependence of surface enhanced Raman spectroscopy (SERS) enhancement at the hot spots can provide insight on the design of newer plasmonic nanostructures with optimal nanogaps.
†Photosciences and Photonics Group, National Institute for Interdisciplinary Science and Technology (NIIST), CSIR, Thiruvananthapuram, 695 019, India.
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Shanthil
‡School of Chemistry, Indian Institute of Science Education and Research-Thiruvananthapuram (IISER-TVM), CET Campus, Thiruvananthapuram, 695 016, India.
Reshmi
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Thomas
‡School of Chemistry, Indian Institute of Science Education and Research-Thiruvananthapuram (IISER-TVM), CET Campus, Thiruvananthapuram, 695 016, India.
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Swathi
†Photosciences and Photonics Group, National Institute for Interdisciplinary Science and Technology (NIIST), CSIR, Thiruvananthapuram, 695 019, India.|‡School of Chemistry, Indian Institute of Science Education and Research-Thiruvananthapuram (IISER-TVM), CET Campus, Thiruvananthapuram, 695 016, India.
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George Thomas
FDTD; SERS; electromagnetic enhancement; hot spot; plasmon coupling