The rising demand for multifunctional coatings in healthcare, smart textiles, and filtration technologies has driven interest in polymer-based thin films with integrated antibacterial, mechanical, and electrical properties. This study presents a scalable Layer-by-Layer (LbL) nanocoating approach using water-soluble polyelectrolytes and carbon nanotubes (CNTs). Branched polyethylenimine (BPEI, pKa ~9.5) and poly(acrylic acid) (PAA, pKa ~4.5) were selected as the polycation and polyanion, respectively, exhibiting pH-dependent ionization behavior. Optimal LbL conditions were achieved at pH 10 for BPEI and pH 4 for PAA to ensure strong electrostatic interactions and robust multilayer formation. CNTs were incorporated into the PAA solution to form conductive interlayers, enhancing both electrical conductivity and mechanical durability.
Antibacterial activity was assessed using Staphylococcus aureus (ATCC 6538), following the KS K 0693 standard. BPEI, PAA, and PAA+CNT solutions were tested, with all showing inhibition zones. BPEI exhibited the strongest antibacterial effect due to its high positive charge density. Subsequently, 20 bilayers of coatings were deposited on glass coverslips via spray-assisted LbL using BPEI/PAA and BPEI/PAA+CNT. Samples underwent three post-treatments: untreated, UV exposure, and autoclaving. All coated samples maintained antibacterial activity, with CNT-containing films retaining efficacy even after sterilization, suggesting synergistic antibacterial effects from CNT–microbe interactions.
Surface analysis revealed increased roughness and interfacial adhesion in CNT-containing coatings, contributing to improved durability and reusability. Electrical measurements confirmed enhanced conductivity, highlighting their potential in smart interfaces, antistatic films, and biosensing platforms.
This work demonstrates a versatile and scalable strategy for developing multifunctional antibacterial nanocoatings using pH-tuned LbL assembly and CNT integration, offering promising applications in biomedical, industrial, and consumer-oriented technologies.
