title: The structural and optical constants of Ag2S semiconductor nanostructure in the Far-Infrared.
abstract: BACKGROUND
  In this paper a template-free precipitation method was used as an easy and low cost way to synthesize Ag2S semiconductor nanoparticles. The Kramers-Kronig method (K-K) and classical dispersion theory was applied to calculate the optical constants of the prepared samples, such as the reflective index n(ω) and dielectric constant ε(ω) in Far-infrared regime.
  
  
  RESULTS
  Nanocrystalline Ag2S was synthesized by a wet chemical precipitation method. Ag2S nanoparticle was characterized by X-ray diffraction, Scanning Electron Microscopy, UV-visible, and FT-IR spectrometry. The refinement of the monoclinic β-Ag2S phase yielded a structure solution similar to the structure reported by Sadanaga and Sueno. The band gap of Ag2S nanoparticles is around 0.96 eV, which is in good agreement with previous reports for the band gap energy of Ag2S nanoparticles (0.9-1.1 eV).
  
  
  CONCLUSIONS
  The crystallite size of the synthesized particles was obtained by Hall-Williamson plot for the synthesized Ag2S nanoparticles and it was found to be 217 nm. The Far-infrared optical constants of the prepared Ag2S semiconductor nanoparticles were evaluated by means of FTIR transmittance spectra data and K-K method. Graphical abstractThe Far-infrared optical constants of Ag2S semiconductor nanoparticles.
authors.affiliation: Department of Physics, Faculty of Science, Universiti Putra Malaysia, Serdang, Selangor 43400 UPM Malaysia ; Department of Materials and Ceramic Engineering (DEMaC), University of Aveiro, Campus Santiago, Aveiro, 3810-193 Portugal.
authors.forename: Reza
authors.initials: R
authors.lastname: Zamiri
authors.affiliation: Department of Chemistry, Faculty of Science, Najafabad Branch, Islamic Azad University, Najafabad, Isfahan Iran.
authors.forename: Hossein
authors.initials: H
authors.lastname: Abbastabar Ahangar
authors.affiliation: Department of Physics, Faculty of Science, Universiti Putra Malaysia, Serdang, Selangor 43400 UPM Malaysia.
authors.forename: Azmi
authors.initials: A
authors.lastname: Zakaria
authors.affiliation: Department of Physics, Faculty of Science, Universiti Putra Malaysia, Serdang, Selangor 43400 UPM Malaysia.
authors.forename: Golnoosh
authors.initials: G
authors.lastname: Zamiri
authors.affiliation: Department of Materials and Ceramic Engineering (DEMaC), University of Aveiro, Campus Santiago, Aveiro, 3810-193 Portugal.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Shabani
authors.affiliation: TEMA-NRD, Mechanical Engineering Department and Aveiro Institute of Nanotechnology (AIN), University of Aveiro, Aveiro, 3810-193 Portugal.
authors.forename: Budhendra
authors.initials: B
authors.lastname: Singh
authors.affiliation: Department of Materials and Ceramic Engineering (DEMaC), University of Aveiro, Campus Santiago, Aveiro, 3810-193 Portugal.
authors.forename: J M F
authors.initials: JM
authors.lastname: Ferreira
keywords: Crystal structure; Infrared spectroscopy; Nanostructures; Optical properties; Raman spectroscopy; Semiconductors