Tuning the Refractive Index and Optical Band Gap of Silk Fibroin Films by Electron Irradiation

S Asha,Y Sangappa,Sanjeev Ganesh

doi:10.1155/2015/879296

Abstract

TheBombyx morisilk fibroin (SF) films were prepared by solution casting method and effects of electron beam on the optical properties and optical constants of the films have been studied by using UV-Visible spectrophotometer. Optical properties like optical band gapEg, refractive indexn, extinction coefficientk, optical conductivityσopt, and dielectric constantsε∗of virgin and electron irradiated films were determined by using UV-Visible absorption and transmission spectra. It was found that the reduction in optical band gap and increase in refractive index with increasing radiation dosage was observed. It is also observed from results that there is increase in dielectric constants with increasing photon energy. The observed optical changes have been tried to be correlated with the structural changes, revealed through FT-IR spectroscopy. The present study is quite important for tailoring the optical responses of SF films as per specific requirements.

Highlights

IntroductionSilk fibroin (SF) is found to be well suited for optical applications in film form with free standing materials of thickness between 20 and 100 μm
We have reported the influence of 8 MeV electron irradiation effects on the optical properties and optical constants of silk fibroin films
It is used to estimate the value of optical energy band gap (Eg) in polymers

Summary

Introduction

Silk fibroin (SF) is found to be well suited for optical applications in film form with free standing materials of thickness between 20 and 100 μm. This is possible due to regenerated silk fibroin in the solid state containing extremely stable β-pleated sheets. These secondary structures are stabilized by interchain hydrogen bonding in which every amino acid is laterally bonded twice to its nearest neighbor chain segments. Silk fibroin in film form has been recognized as a suitable biopolymer for the development of optical devices [11], optical waveguides [12], luminescent solar concentrators [13], 2D, 3D optical elements-holograms, lenses, optical gratings, and antireflective coatings [14, 15]

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Conclusion