Preparation of functionalized cellulose nanoparticles with tunable structure and properties via etherification in alkaline solutions

An alkali‑assisted strategy fabricated functionalized cellulose nanoparticles. • NaOH concentration determined the cellulose state and formation pathway. • Swollen cellulose formed nanoparticles by top-down disintegration after etherification. • Dissolved cellulose regenerated into nanoparticles by bottom-up assembly during dialysis. • QCNPs showed tunable properties and > 99% antibacterial activity. Developing efficient and sustainable strategies for fabricating functionalized cellulose nanoparticles with tunable structures and properties remains challenging. Herein, we report an alkali‑assisted strategy integrating freeze-thaw pretreatment, etherification, and dialysis to produce charged cellulose nanoparticles under mild alkaline conditions. At 1.5 wt% NaOH, cellulose mainly underwent swelling, and the formation of nanoparticles after etherification was consistent with a top-down disintegration process of swollen cellulose. At 5 wt% NaOH, cellulose was dissolved, and the formation of nanoparticles during dialysis was consistent with a bottom-up regeneration process. The introduced charged groups suppressed hydrogen-bond-driven re-aggregation during alkali removal. Using this strategy, tunable cationic quaternized cellulose nanoparticles (QCNPs) and anionic carboxymethylated cellulose nanoparticles (CMCNPs) were successfully prepared, with size ranges of 20–252 nm and 19–100 nm, respectively. Quaternized cellulose nanoparticles prepared in 5 wt% NaOH were obtained in high recovery (98%) with a high degree of substitution (DS = 0.98). In addition, QCNPs exhibited antibacterial activity above 99% against Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ). This strategy provides a general route to preparing cellulose nanoparticles with tunable structures and functionalities, offering a simple and versatile approach for the high-value utilization of cellulose. Download: Download high-res image (189KB) Download: Download full-size image