Silver nanoparticles and chitosan oligomers composites as poplar wood protective treatments against wood-decay fungi and termites

Abstract

This study focuses on Populus ×euramericana (Dode) Guinier, a globally distributed fast-growing tree. Despite its valuable wood, it exhibits low durability. The aim of this study was to assess the efficacy of a binary composite comprising silver nanoparticles (AgNPs) and chitosan oligomers (COS) in protecting P. ×euramericana ‘I-214’ wood against degradation caused by xylophagous fungi and termites through vacuum-pressure impregnation. The test material was carefully selected and conditioned following the guidelines of EN 350:2016, and impregnation was carried out in accordance with EN 113-1:2021. Five concentrations of AgNPs–COS composites were utilized. Biodeterioration resistance was evaluated based on EN 350:2016 for white (Trametes versicolor (L.) Lloyd) and brown (Coniophora puteana (Schumach.) P.Karst.) rot fungi, and EN 117:2012 for subterranean termites (Reticulitermis grassei Clément). The durability class and use class were assigned following EN 350:2016 and EN 335:2013, respectively. In comparison to the untreated control, the binary solution at its highest concentration (AgNPs 4 ppm + COS 20 g·L−1) demonstrated a notable reduction in weight loss, decreasing from 41.96 ± 4.49% to 30.15 ± 3.08% for white-rot fungi and from 41.93 ± 4.33% to 27.22 ± 0.66% for brown rot fungi. Furthermore, the observed termite infestation shifted from “heavy” to “attempted attack”, resulting in a decrease in the survival rate from 53.98 ± 10.40% to 26.62 ± 8.63%. Consequently, the durability classification of P. ×euramericana I-214 witnessed an enhancement from “Not durable” to “Slightly” and “Moderately durable” concerning decay fungi and termites, respectively. These findings expand the potential applications of this wood and substantiate the advantages of employing this environmentally friendly treatment.