Mold resistance of bamboo treated with copper complexes-grafted silica gel and its microdistribution in treated bamboo

Bamboo is readily discolored by mold fungi, which greatly limits its applications. An effective antifungal agent, copper(II) chloride (CuCl2)-grafted silica gel, was prepared by a sol-gel process using tetraethoxysilane (TEOS)/3-aminopropyltriethoxysilane (APTES) mixtures. The elemental composition and the chemical combinations of homogeneous sol mixture (HSM) and bamboo were determined via Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy with energy-dispersive X-ray spectrometry (SEM-EDS). The mold resistance of bamboo treated with HSM, alkaline copper quat (ACQ), chromated copper arsenate (CCA), and purified water was characterized by an indoor mold test. The micro-morphology of bamboo treated with HSM was investigated using scanning electron microscopy (SEM). HSM penetrated into the bamboo vessels, and formed xerogels, which was able to coordinate copper(II) cations. SEM-EDS investigations suggest that Si-O-Cu linkages may be formed through an exchange reaction between silanol groups and copper complexes. The bamboo samples treated with HSM showed highly efficient mold resistance due to a good penetration of HSM. Furthermore, no fungal hyphae were found in the structure of HSM-treated bamboo after a 5-week mold test. The copper complexes grafted to silica gel developed in this work provide an efficient antifungal agent for a wide range of potential applications in bamboo protection.