Abstract:

Objective: In order to prepare TiO₂@SiO₂-delignified wood(TiO₂@SiO₂-DW) with an enhanced photostability by suppressing photodegradation of remaining lignin in DW, SiO₂, a kind of UV light inert material, was coated on the surface of TiO₂ nanoparticles to form monodispersed TiO₂@SiO₂ with core@shell structure to suppress inherent photocatalytic activity of TiO₂, to remain UV shielding, Vis light transparent properties. Method: The monodispersed, anatase TiO₂ nanoparticles with size of about 8 nm, which modified with oleic acid, dispersed in cyclohexane, were prepared by liquid-solid-solution(LSS) method. Reverse microemulsion method was used to deposit SiO₂ onto the surface of as-prepared TiO₂ nanoparticles to form monodispersed TiO₂@SiO₂ with size of about 12 nm, core@shell structure, and a good dispersity in ethanol. The lignin was removed from natural wood by H₂O₂/HAc delignification method to form DW with well-preserved cellulose skeleton. TiO₂@SiO₂ was soaked/coated on the surface of DW, and subsequently mechanical pressing to form TiO₂@SiO₂-DW. TEM, XRD, FTIR, and UV-Vis were used to characterize morphology/monodispersity, crystallized phase, functional groups, and UV-Vis absorbance properties of both TiO₂ and TiO₂@SiO₂. SEM and EDS were used to demonstrate the coating of TiO₂@SiO₂ on the surface of DW. Parameters of L^*a^*b^* of DW and TiO₂@SiO₂ -DW were used to evaluate the photostability. Result: TEM images demonstrates that both TiO₂ and TiO₂@SiO₂ possess monodispersity with particle size of 8 and 12 nm, respectively. The photos reveal that both TiO₂ and TiO₂@SiO₂ have a good dispersity in cyclohexane and ethanol, respectively. XRD analysis indicates that the crystallized phase of TiO₂ core and SiO₂ shell are anatase and amorphous, respectively. UV-Vis reveals that, TiO₂@SiO₂ possess both UV shielding and Vis light transparent properties. Remaining lignin content of DW is as low as 0.8%. SEM/EDS and photos demonstrate that TiO₂@SiO₂ is uniformly coated on the surface of DW with original color and texture. The result of accelerating aging test indicates that, ΔE^* value of H₂O₂/HAc-DW and TiO₂@SiO₂-DW is 4.9±0.9 and 2.3±0.3, respectively, due to the contribution of both 0.8% remaining lignin content and UV shielding of TiO₂@SiO₂. Conclusion: Based on the strategy of delignification and UV shielding of TiO₂@SiO₂, TiO₂@SiO₂-DW shows an enhanced photostability, better than those of TiO₂-, antimony-doped tin oxide-, and organic UV shielding compound protected wood, DW, and transparent wood. The mechanical strength of TiO₂@SiO₂-DW is better than that of natural wood. We might provide an alternative solution to deposit SiO₂ shell on the surface of the other nanoparticles with monodispersity, size of about 8 nm, oleic acid modification, prepared via LSS method.

Key words: TiO₂@SiO₂, delignified wood(DW), photostability