Copper complexes grafted to functionalized silica gel as wood preservatives against the brown rot fungus Coniophora puteana

Wood modification with siloxanes bearing amino groups with copper-linking function was carried out by a sol–gel process. Tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES) were the main components. Two different procedures were followed: a two-step process (impregnation with the TEOS/APTES mixture followed by dipping into a copper sulphate solution) and a one-step process (impregnation with a homogeneous sol mixture of TEOS, APTES and copper (II) chloride). The obtained materials were characterized by infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy dispersive X-ray microanalysis. The determination of copper content before and after leaching was performed by atomic absorption spectroscopy. The efficacy against the brown rot fungus Coniophora puteana was tested by an accelerated procedure. SEM analyses showed that silicon penetrated into wood, while copper is effectively drawn into wood only in the one-step treatment. Copper fixation to the silica gel proved to be adequately strong. Both sol–gel treatments gave good protection against Coniophora puteana.