Inclusion of cobalt reinforced Ag doped SnO2 properties: electrical, dielectric constant, magnetic and photocatalytic insights

Cobalt as a second dopant played remarkable roles in enhancing the electrical conductivity, dielectric constant, ferromagnetic and photocatalytic properties of Ag doped SnO2 nanoparticles. Pure, Ag doped and Ag/Co codoped SnO2 nanoparticles were synthesized by co-precipitation method. Rietveld refinement analysis for XRD data confirmed the single phase nature in all SnO2 compositions with tetragonal rutile structure. The noticeable changes in the unit cell volume of SnO2 established for the successful incorporation of Ag and Co ions into its host lattice. SEM and TEM images clearly showed the formation of very fine spherical nanoparticles with uniform distribution. The binary dopants of Ag/Co ions induced blue shifts in SnO2 band gap due to Burstein-Moss effect. Notable increases in the electrical conductivity of (Ag, Co) codoped SnO2 samples compared to pure one were detected. The adsorption and desorption of the oxygen species on SnO2 surface have showed significant influences on the conductivity-temperature behavior. The dielectric constant as function of frequency was discussed based on the Maxwell-Wagner model. Sn0.97Ag0.01Co0.02O2 structure exhibited the highest dielectric constant of 3129 at low frequency (42 Hz). Also, insertion of Co plus Ag ions stimulated perfect ferromagnetic loops and enriched the magnetic parameters of SnO2. The enhanced ferromagnetism was discussed based on F-center exchange interaction between Co2+ ions via oxygen vacancies (up arrow Co2+-down arrow V-o-up arrow Co2+). Besides that, the load of Co ions made a high jump in the photocatalytic activity of Ag doped SnO2. High activity, 97%, for methylene blue (MB) degradation was realized through Sn0.95Ag0.01Co0.04O2 catalyst with practical efficiency stability for three cycles within 97-88%. Cobalt played a main role in the separation of the photogenerated electron-hole pairs plus oxygen vacancies formation which improved the photocatalytic activity.