Authors: Neha Mishra G V Pavan Kumar
Publish Date: 2011/12/10
Volume: 7, Issue: 2, Pages: 359-367
Abstract
Topillumination tipenhanced Raman scattering TITERS has recently emerged as a promising nearfield vibrational spectroscopy method that can be adapted on an upright optical microscope With a relatively simplified optics TITERS can probe both opaque and transparent samples making them a promising tool in nanoscale chemical analysis One of the critical components of TITERS is the plasmonic nanotip used to enhance the Raman spectroscopic signature Herein we numerically studied the nearfield optical properties of conventional gold tip 20 nm radius of curvature and two varieties of optical antennabased tips in the context of TITERS Optical antennabased tips included a 40nm gold nanoparticle attached to a dielectric tip and a 50nm equilateral gold nanotriangle attached to a dielectric tip We evaluated the Raman enhancement spectra as a function of experimental variables such as underlying substrate and angle of the tip with respect to substrate normal Our analysis revealed that conventional gold tip facilitates superior enhancement and optical antennabased tips facilitate superior spectral bandwidth and lateral resolution in TITERS configuration Tips with higher enhancement can be harnessed for ultrasensitive measurements and tips with broader spectral bandwidth can be utilized to enhance both Stokes and antiStokes component of the Raman spectra
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