Surface modification of bamboo with L-DOPA and PEI to promote stable nano-silver coating for antimicrobial applications

s Bamboo is a sustainable and renewable material. However, its high hydrophilicity and nutrient-rich composition make it highly susceptible to microbial colonization. In this study, a simple two-step strategy was employed to fabricate stable nano-silver particles (AgNPs) containing polymer composites on bamboo surfaces to enhance antibacterial and anti-mold properties. L-3,4-dihydroxyphenylalanine (L-DOPA) was modified onto the bamboo surface via self-polymerization, providing catechol groups capable of chelating and reducing Ag⁺ ions in situ to form AgNPs. The incorporation of polyethyleneimine (PEI) into the L-DOPA could further promote AgNPs formation and enhance stability of the composite coating. The resulting BT/L-D/PEI/Ag sample was systematically characterized by SEM, XRD, FTIR, XPS, EDS, and water contact angle measurements. The results confirmed that L-D/PEI/Ag polymer composites were successfully coated onto the bamboo surface, and the BT/L-D/PEI/Ag exhibited a significantly enhanced silver loading (6.68 wt%) compared to the BT/L-D/Ag (2.97 wt%), corresponding to a 125 % increase. The modified surface showed improved hydrophobicity with a contact angle of 94.7°, effectively inhibiting microbial adhesion. Antibacterial tests revealed that the BT/L-D/PEI/Ag achieved complete (100 %) inhibition against Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ), as well as superior antifungal activity against Aspergillus niger ( A. niger ). The synergistic interaction between L-D, PEI and Ag formed an efficient antimicrobial coating, providing a promising strategy for the development of high-value, antimicrobial bamboo materials for sustainable construction and consumer products.