SPR studies on optical fiber coated with different plasmonic metals for fabrication of efficient biosensors

Abstract

In the recent years, there have been numerous reports on study of Surface Plasmon Resonance (SPR) in different Plasmonic metals. Optical – fiber based SPR sensors have gained much attention over the years because of their copious advantages over conventional Prism coupled SPR sensors, including miniaturization, ability to perform remote sensing etc. In the present work, Optical – fiber based Surface Plasmon studies are performed on metal – air interface with different Plasmonic metals. Four different metals chosen for the current work are as follows: Gold (Au), Silver (Ag), Aluminum (Al) and Copper (Cu). Thermal Evaporation technique is utilized to deposit the Au, Ag, Al and Cu metal thin films. XRD, AFM and UV–Visible spectroscopy are used for the determination of the structural, morphological and optical characteristics of the deposited metal thin films. SPR transmittance curve is obtained for different metals and their observed SPR wavelength (λspr) matches very well with the reported values. The performance of these metals for their application in SPR based biosensors, was assessed in terms of the Full Width at Half Maxima (FWHM) and minimum transmitted intensity (Tmin) of their SPR transmittance curves and it was found that Ag (50 nm thickness) possesses the least FWHM whereas Au (40 nm thickness) has the lowest Tmin. Suitability of both Ag and Au is discussed for sensing applications and it was concluded that Au (40 nm thickness) is a better candidate for the realization of efficient biosensors.