Au nanoparticles dispersed chitosan/ZnO ternary nanocomposite as a highly efficient and reusable visible light photocatalyst

The environmental pollution in particular contamination of surrounding and ground water are major concerns for regulation authorities and scientific community. In the current work, a novel visible light ternary photocatalytic structure based on mesoporous ZnO in combination with chitosan (CSN) and gold nanoparticles (AuNPs) was synthesized for serious water pollution issue. The Au@CSN/ZnO nanocomposite photocatalyst was developed through the sol-gel methodology followed by ultrasonication and photoreduction techniques. XRD investigation revealed the hexagonal wurtzite structure of ZnO, while XPS and FTIR measurements confirmed the formation of ternary nanocomposite among Au, CSN and ZnO. TEM analysis revealed the presence of AuNPs (5-15 nm), CSN sheets (micron size) and ZnO nanoparticles (20-120 nm) in designed ternary photocatalyst. Diffuse reflectance spectroscopy showed lowering in band gap energy from 3.1 to 2.87 eV as bare ZnO modified to Au@CSN/ZnO. The as-fabricated Au@CSN/ZnO nanocomposite was proven as a decidedly efficient photo-catalyst when employed on colorless insecticide imidacloprid (IMD) and on colored methylene blue (MB) dye under visible-light illumination. Efficient photocatalytic performance with 93.21% removal of insecticide only in 20 min was achieved, representing 211% more efficient than bare mesoporous ZnO. In addition, Au@CSN/ZnO nanostructure showed rapid removal of MB with almost complete destruction of complicated structure just in 12 min under visible light. Furthermore, the current-developed photocatalyst exhibited adequate stability and recyclability, which is beneficial for the practical application in environmental remediation.