Fabrication of cellulose nanocrystals (CNCs) in choline chloride-citric acid (ChCl-CA) solvent to lodge antimicrobial activity

Abstract

Surface-modified cellulose nanocrystals (CNCs) have gained substantial interest in industry. The renewability and abundance of the raw material to prepare CNCs make them a promising green material. In this study, two types of CNCs were prepared by sulfuric acid (H2SO4) and stepwise H2SO4 and choline chloride-citric acid (ChCl-CA) deep eutectic solvent-like (DES) treatments. The DES treatment led to esterification and further degradation of the CNCs. The obtained nanoparticles were distributed in size range of 50 nm to 500 nm and 20 nm to 70 nm for the H2SO4 and stepwise treatments, respectively. The effects of the nanoparticles on the mechanical properties, thermal stability, and antibacterial activity of poly(vinyl alcohol) (PVOH) were determined using a universal mechanical testing machine, thermogravimetric analysis (TGA), and the agar diffusion method. The results indicated that nanoparticles had good compatibility in PVOH at a concentration below 10%. The CNCs had greater effect on the mechanical properties and the thermal stability of films than the esterified CNCs. However, the CA modified CNCs showed more favorable antibacterial activity than the CNCs from H2SO4 treatment. Taking the mechanical properties, the thermal stability, and the antibacterial activity into consideration, 5% was selected as a suitable concentration for composite film preparation.