Terahertz, Infrared, and UV-Vis Spectroscopy Study on Silver@Polyaniline Core@Shell Nanocomposites: Optical and Electronic Properties

We present transmission measurements on silver@polyaniline (Ag@PANI) core@shell nanocomposites over a wide frequency range from terahertz to ultraviolet (0.001-6.2 eV). The Ag@PANI core@shell nanocomposites were prepared using solid-state reaction by mixing aniline sulfate (ANS) with 2.5, 5, 7.5, and 10 wt % AgNO3. The nanocomposites were characterized by transmission electron microscope, ultraviolet/visible spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The optical conductivity sigma(omega) was fitted using the localization-modified Drude model together with the Lorentzian function. The incremental loading of AgNO3 leads to an increase in the Drude conductivity (sigma(LMD)) and decrease of the scattering rate (gamma(D)) due to the increase of electron delocalization of protonated quinoid imine units. In addition, the densities of states N-EF at the Fermi level are increased from 1.7 to 2.7 per eV per formula unit, while the conduction bandwidth W is decreased from 0.7 to 0.4 eV with increasing the AgNO3 from 2.5 to 10%. The optically determined band parameters suggest that the addition of AgNO3 modifies the energy state of the Ag@PANI core@shell nanocomposites close to the Fermi energy modifying the half-filled polaron band.