A facile thermal decomposition approach for the synthesis of SiO2@ZnS core-shell nanoparticles and their application as effective adsorbent for the removal of congo red

Abstract

SiO2@ZnS core-shell nanoparticles in which mesoporous SiO2 acts as the core and ZnS acts as the shell were synthesized by a novel thermal decomposition approach. Various analytical techniques were used to prove their formation. XRD analysis proved the formation of cubic ZnS nanoparticles and amorphous SiO2 in the core-shell nanoparticles. Morphological studies, using FESEM and TEM, prove that the SiO2@ZnS consists of SiO2 as the core and ZnS as the shell. XPS study confirms the presence of Zn2+, S2−, Si4+ and O2− in the SiO2@ZnS core-shell nanoparticles. DRS studies suggest that the SiO2@ZnS core-shell nanoparticles absorb in UV region and the band gap of ZnS nanoparticles in SiO2@ZnS can be tuned by simply varying the amount of ZnS precursors. PL study confirms the presence of defect states in the SiO2@ZnS core-shell nanoparticles. The SiO2@ZnS core-shell nanoparticles were tested as adsorbent for the removal of congo red (CR) from an aqueous solution and it was observed that the SiO2@ZnS core-shell nanoparticles perform better as adsorbent compared to pure SiO2 and ZnS nanoparticles.