Interpenetration of wood with NH2R-functionalized silica xerogels anchoring copper(II) for preservation purposes

Interpenetration of wood samples of pine sapwood (Pinus sylvestris L.) with hybrid inorganic–organic silica xerogels bearing amine functions able to coordinate copper(II) cations has been successfully carried out. These materials have been prepared by sol–gel processing TEOS/APTES mixtures inside the wood. Solid state ²⁹Si NMR data provide evidence that the interpenetrated xerogel material has the same degree of condensation of the corresponding xerogel formed outside the wood. Copper(II) is effectively vehiculated inside the wood by coordination linkages with two ammine functions well evidenced by ESR measurements. SEM/EDX investigations show that the chlorine/copper atomic ratio inside the wood is lower than that of the starting salt CuCl₂, suggesting an exchange reaction with silanol groups with the formation of Si–O–Cu linkages and HCl. This reaction could be promoted by the excess of amine functions with formation of ammonium chloride species which remain onto the surface of the wood and in the mother solution owing to a higher degree of condensation. Sodium silicate was tested in place of TEOS in order to have a cheaper and ethanol-free formulation. However, gel penetration results significantly lower than that of the corresponding formulation containing TEOS and preservation performance are lower than that of TEOS formulation against brown-rot fungal decay.     

Beech (Fagus orientalis) wood modification through the incorporation of polystyrene-ricinoleic acid copolymer with Ag nanoparticles

Today, there is a growing interest in eco-friendly processes that are greatly needed as a result of the worldwide problem of environmental pollution. In this study, ricinoleic acid was autoxidized in the presence of silver nitrate in order to prepare ricinoleic acid macroperoxide initiator with silver nanoparticles (PriciAg). Beech (Fagus orientalis Lipsky) sapwood samples were impregnated with the solution of PriciAg under vacuum in a small-scale impregnation container. Thermal polymerization of styrene with PriciAg was carried out inside the Beech sapwood samples leading to wood composite material containing polystyrene-g-ricinoleic acid with silver nanoparticles (Ag NPs). The decay test of wood treated with AgNPs against white-rot (Trametes versicolor) fungus was then investigated. Insect resistance was performed with Trichoferus holosericeus Rossi. In addition, the leaching test was carried out according to the EN 84 standard and silver content in leached water measured by inductively coupled plasma (ICP) analysis (AWPA A7). Chemical characterization of the modified wood was characterized using FTIR-ATR technique. The nano silver obtained via environmentally friendly processes exhibited high potential activity against white rot fungus. In addition, the AgNPs showed a higher resistance to leaching because of the polystyrene, as demonstrated by the resistance of treated samples to decay compared with that of the control. Leached and unleached test samples indicated the same mass loss after decay tests. FTIR spectra showed that characteristic peak values of polystyrene and ricinoleic acid appeared at 2980 cm^?1and 1728 cm^?1, respectively in the impregnated wood.

Graphical abstract