Pilot preparation study of gold nanoparticle-chitosan composite catalyst

Abstract

The wide range of applications of AuNPs is related to their different shapes and sizes, which are dependent on the synthesis process and reaction parameters. Therefore, the optimization of a novel and highly efficient approach to chitosan substrate decoration by AuNPs via covalent bonding using dialdehyde cellulose (DAC) is presented here. The covalent binding of AuDAC to chitosan nanofibers is mediated by a Schiff base reaction. This improves particle binding compared to conventional methods such as simple dip coating where AuNPs bind to the substrate only via weak interaction. In this work, initial attempts for the preparation of a composite material based on mixing the AuDAC solution with a chitosan solution were conducted. However, this process was found to be inefficient due to the inhomogeneous morphology of the resulting material, i.e., the formation of irregular chitosan micro-nanofibers and sheets sparsely decorated with AuDAC. Therefore, an optimized approach based on the binding of pre-made AuDAC nanoparticles to electrospun chitosan nanofibers was utilized. This method showed high binding efficiency and very dense decoration of nanofibers with AuDAC opposed to method involving mixing of chitosan and AuDAC solutions. Subsequently, the ability of the composite material in the form of a thin filtration layer to catalytically reduce 4-nitrophenol (4NP) to 4-aminophenol (4AP) was demonstrated. The efficacy of binding AuNPs to nanofibers was also compared to nanoparticles synthesized using another type of polysaccharide, specifically hyaluronic acid dialdehyde (DAH).