Study On The Interfacial Characteristic Of Antifungal TiO₂-based Nanocrystals For Bamboo

Bamboo is an abundant natural resource in China.It has excellent physical and mechanical properties,and it has been extensively used as decoration and building material.However,bamboo is readily infected with fungi because of its abundant sugar,starch and protein content,which greatly restricts its utilization.To develop a highly effective environmentally sound antifungal agent for bamboo,ZnO-TiO₂/bamboo and Fe-doped TiO₂/bamboo have been synthesized,respectively.The morphology,crystallinity,and chemical structure of the specimens have been investigated by SEM?EDS?XRD?XPS?ESR?UV-VIS.The interfacial binding mechanism of TiO₂ with bamboo and with ZnO was studied.According to the Chinese Standard GB/T 18261-2013,the antifungal activities of ZnO-TiO₂ bamboo were investigated under indoor and outdoor conditions,respectively.The antifungal activities of Fe-doped TiO₂ thin films bamboo were investigated under outdoor conditions.Furthermore,the mechanism of the antifungal behavior has been verified.The main results can be summarized as follows:?1?The interfacial characterization of flower-like ZnO-TiO₂ bamboo and the antifungal capacity under indoor conditions:The obtained TiO₂ had a pure anatase phase.There are two modes of interfacial bonding between bamboo and TiO₂ nanocrystals:1)the bamboo substrate combined with anatase TiO₂ by a hydrogen bonding;2)ligand exchange reaction between F^- and �OH.The F^-ions on the TiO₂ surface combined with[Zn?NH₃?₄]²⁺ via electrostatic adsorption,contributing to the formation of a flower-like ZnO microstructure,and were then deposited on the TiO₂ thin films.Moreover,the antifungal activities of the samples against the hybrid fungi group were investigated during a three-month period under dark conditions.The results showed that the fungi began to grow on pristine bamboo on the 5th day,the face infection value up to 100 on the 9th day;In TiO₂/B,the fungi began to grow gradually on the third week,with the infection value up to 100 after 10 weeks.The ZnO-TiO₂ bamboo exhibited a 12-week inhibition.?2?The interfacial characterization of cross-linked ZnO-TiO₂ bamboo and the antifungal capacity under outdoor conditions:The ZnO-TiO₂-layered double-nanostructures with the average thickness of 20?m have been synthesized on bamboo surfaces.The cross-linked wurtzite ZnO nanostructures with an average thickness of approximately 0.14?m were uniformly distributed on the anatase TiO₂ surface.During a two-month antifungal test conducted in an outdoor environment,the fungi began to grow after one week on pristine bamboo and three weeks on ZnO bamboo and TiO₂ bamboo.There was an infected area of 100%after four weeks for pristine bamboo and six weeks for ZnO bamboo,while there was an infected area of 43% after eight weeks for TiO₂ bamboo.By comparison,there was no visible fungal growth on ZnO-TiO₂ bamboo until the end of the test.The electron spin resonance?ESR?technique has demonstrated that the reactive oxygen species of �O₂^-and�OH were produced from the ZnO-TiO₂ surface under visible light irradiation.This large quantity of �O₂^- compared to�OH is considered to be mainly responsible for the inactivation of fungi.Additionally,the limiting oxygen index?LOI?has increased from 25.6% to 30.2% after being covered with a ZnO-TiO₂ coating,which revealed a significant enhancement of its flame-retardant property.?3?The interfacial characterization of Fe-doped TiO₂ bamboo and the antifungal capacity under outdoor conditions:All of the as-prepared TiO₂ nanoparticles on the bamboo surface were anatase phase.The Fe-doped TiO₂ thin films were found to grow on the bamboo surface by the self-aggregation of nanoparticles with an average diameter of about 9.7 nm and a surface area of about 90.96 m² g^-1.The antifungal activity of the samples was investigated under natural weather conditions.Compared with pristine bamboo and TiO₂ bamboo,the Fe-doped TiO₂ bamboo exhibited much higher inhibition ability to fungi under the natural environment,which is due to the fact of the red shift of the absorption edge and the band gap of was decreased,extending the light response of TiO₂ to the visible light region and improving its light absorption performance.