Carboxylated cellulose nanocrystals mediated flower-like zinc oxide for antimicrobial without activation of light

Abstract

Conventional light-driven antimicrobial strategies of zinc oxide (ZnO) are limited by inadequate illumination in dark environments. In this study, carboxylated cellulose nanocrystals (MCNC) mediated flower-like ZnO (C_0.1@Z) with self-promoted reactive oxygen species release under dark is fabricated. The adsorption of Zn²⁺ ions on MCNC prompts the growth of ZnO along the (002) crystal plane, forming a flower-like hybrid with superior dispersibility and oxygen vacancies compared to MCNC-free ZnO, which exposes the (100) plane. MCNC serves as an electron donor, increasing oxygen adsorption and electron transfer in C_0.1@Z. Consequently, the generation of superoxide anions through oxygen reduction without photoirradiation is significantly boosted, thereby amplifying in-dark antimicrobial activity of C_0.1@Z. Incorporating 2.5 % of C_0.1@Z into pulp to prepare optimal antimicrobial paper (P-C@Z_2.5) results in the prominent bactericidal and fungicidal effects against Staphylococcus aureus (99.8 %), Escherichia coli (99.9 %), Aspergillus niger (12.9 mm inhibition zone), and Botrytis cinerea (11.6 mm inhibition zone) in the absence of light. Additionally, P-C@Z_2.5 exhibited low toxicity to cells and significantly extended the shelf life of blueberries to over 21 days. Overall, this work provides a promising approach for designing an effective antimicrobial material in the absence of light to address bacterial colonization of food during dark storage.

Keywords: Antimicrobial; Cellulose nanocrystals; Fresh keeping; ZnO.