Speaker
Description
Activated biochar was prepared from lignin by chemical activation with NaOH followed by carbonization at 600 °C for 2 h. The resulting biochar was washed with 1 M HCl and deionized water, dried, and dispersed in water using poly(vinyl pyrrolidone) (PVP) as a surfactant. Multilayer composite films were fabricated by combining a poly(methyl methacrylate-co-butyl methacrylate), p(MMA/BMA) (30/70 wt/wt), matrix with the lignin-derived biochar using a layer-by-layer (LbL) assembly approach. Spin coating deposition enabled the sequential formation of polymer (P) and biochar (B) layers, producing films with different architectures (P, B, P-B, P-B-P, and P-B-P-B). After each deposition step, the films were rinsed to remove loosely bound material and dried at 45 °C to ensure uniform layer formation. The optical properties of the multilayer films were investigated by UV–Vis spectroscopy, revealing characteristic π–π and π–π transitions of the polymer matrix in the UV region. Increasing the number of deposited layers, particularly those containing biochar, enhanced UV absorption while reducing optical transparency, indicating successful incorporation of biochar and increased surface coverage. Surface morphology examined by optical microscopy demonstrated that spin coating produced smooth and homogeneous films, with progressive encapsulation of the biochar particles by the polymer matrix as additional layers were deposited. Among all investigated architectures, the multilayer sandwich structure (P-B-P-B) exhibited the best sensing performance, showing a selective frequency decrease of 160 Hz upon exposure to a 0.02 mg/mL solution of 2,4-dimethylbenzoic acid, whereas the simpler film configurations showed no measurable response. These findings demonstrate the potential of lignin-derived biochar/polymer multilayer films as sustainable functional materials for selective adsorption and sensing applications.
Keywords: lignin-derived biochar, multilayer coatings, adsorption.