Dispersion Analysis of Polypyrrole and ZnO Nanocomposite Thin Film using SPR Techniques

Abstract

The dispersion analysis of any material is crucial for studying its structure and composition. The interaction of the structure of the material with electromagnetic energy is also determined by studying its dielectric or optical properties. For studying dielectric properties, optical approaches are favored over electrical techniques, and Surface Plasmon Resonance (SPR) is the most suited of all techniques. It is used as a result to investigate the optical and dielectric properties of dielectrics at metal-dielectric interfaces. Sol-gel followed by spin coating techniques are used to fabricate thin films of a polypyrrole (PPy) and zinc oxide (ZnO) nanocomposite. The films are prepared of two compositions (70%PPy+30%ZnO) and (80%PPy+20%ZnO) of thin films over a gold coated prism. The dielectric properties were examined by varying the excitation wavelength of the source in the visible range. In the Kretschmann arrangement, attenuated total reflection is used to note SPR reflectance curves. In the Kretschmann arrangement, a thin metal oxide film with a desired refractive index and dielectric constant is placed on an Au-coated prism. The current work makes use of a table top SPR measurement equipment that was created locally. According to SPR observations, the SPR reflectance curve for prism/Au/(70%PPy+30%ZnO)/air system is sharpest. Hence, SPR reflectance curves were also obtained for different source wavelengths varying from 407 nm to 633 nm for the system prism/Au/(70%PPy+30%ZnO)/air. Using the Fresnel's equations to fit experimental SPR data, the optical and dielectric properties of the nanocomposite thin films were calculated. Complex refractive index and dielectric constant are estimated. Refractive index dispersion curve plotted and fitted with Sellmeier equation to analyze the variation of wavelength dispersion of the dielectric properties of the prepared thin films.