Formation of reusable Au-acetonitrile polymers and N-doped graphene catalyst under UV light via submerged liquid plasma process

Abstract

In this study, acetonitrile polymers (ANPs) synthesized using a submerged liquid plasma (SLP) process were used for the direct reduction of Au³⁺ under ultraviolet (UV) light without the need for reducing or templating agents. Nitrogen-functionalized graphene (NFG) and ANPs, both synthesized via the SLP process were used to form a Au–ANPs–NFG nanohybrid. The pyridinic and pyrrolic nitrogen present in the NFG effectively chemisorbs or binds with ANPs through π–π or σ–π interaction. The ANPs provide excellent control over the Au nanoparticle formation size (∼5 nm), as confirmed by high-resolution transmission electron microscopy. High-resolution X-ray photoelectron spectra revealed that the difference in the chemical shift between Au 4f 5/2 and Au 4f 7/2 peaks was 3.7 eV, which confirms that the reduced form of Au⁰ was present in Au–ANPs–NFG. A UV-visible absorbance spectrum further confirms the reduction of Au³⁺ to Au⁰ under 254 nm UV light. The catalytic activity of the as-synthesized Au–ANPs–NFG was used for the selective oxidation of benzyl alcohol to benzaldehyde in both suspended and immobilized forms. The Au–ANPs–NFG immobilized on Pyrex glass resulted in 69% conversion of benzyl alcohol to benzaldehyde. The reuse of immobilized Au–ANPs–NFG led to 69%, 64%, and 61% successive conversions with a reaction time of 330 min.