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Flame retardant and visible light-activated Fe-doped TiO2 thin films were anchored to wood surfaces by a facile precipitation method for the photocatalytic degradation of gaseous formaldehyde. All of the as-prepared TiO2 thin films exhibited the anatase crystal structure and grew on the wood surfaces by the aggregation of nanoparticles with diameters ranging from 11 to 16 nm. The UV–vis diffuse reflectance spectroscopy (UV–vis DRS) results showed that the presence of a small amount of iron ions in the TiO2 matrix could significantly extend the optical responses in the UV to visible region. Compared to the pure TiO2/wood samples, the Fe-doped TiO2/wood samples exhibited higher photocatalytic activities under visible light irradiation. The optimum nFe/nTi molar ratio was 2.0 at. %. The electron spin resonance (ESR) tests further confirmed that the active oxygen species of OH and O2– that were generated on the Fe-doped TiO2/wood samples under visible light irradiation are responsible for the degradation of formaldehyde. The Fe-doped TiO2 samples also exhibited high stability and reusability after 6 cycles. Additionally, the limiting oxygen index of the original wood increased from 24.8% to 33.9% after it was coated with Fe-doped TiO2 thin films, indicating a significant improvement in its flame resistance.

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, flower-like ZnO microstructures supported on TiO2 thin films have been synthesized on bamboo surfaces by a facile two-step low-temperature hydrothermal method. According to the results of various analytical techniques, including X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared–attenuated total reflectance spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy, the bamboo substrate combined with anatase TiO2 by a hydrogen bonding or 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 a hybrid fungi group consisting of Trichoderma viride Pers. ex Fr (T. viride), Penicillium citrinum Thom (P. citrinum), and Aspergillus niger v. Tiegh (A. niger) were investigated during a three-month period under dark conditions. The results showed that pure TiO2 thin films coated on bamboo presented better antifungal activities, with a 21-day inhibition, than that of the pristine bamboo, with a 5-day inhibition. The flower-like ZnO microstructures supported on the TiO2 thin films bamboo exhibited effective antifungal capability, with a 90-day inhibition. The efficient antifungal behavior is due to the increased generation of reactive oxygen species (ROS) from the coatings by a possible synergistic effect between the ZnO and TiO2 nanoparticles in attacking fungi and causing their death.

TiO2-based photocatalytic disinfection has been proved as one of the feasible approaches for the control and inhibition of the growth of mould fungi on woody materials. However, the wide band gap of TiO2 (3.2 eV) limits the efficient absorption of sunlight in the visible region. In this study, visible-light-mediated antifungal bamboo based on Fe-doped TiO2 thin films was successfully fabricated through a facile one-step homogeneous precipitation method. XRD studies confirmed that all of the as-prepared TiO2 nanoparticles on the bamboo surface were anatase phase. 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 Fe-doped TiO2/bamboo samples looked identical to original bamboo as there was no essential effect on the optical properties of the bamboo surface. Moreover, the antifungal activity of the as-prepared samples against mould fungi was investigated under natural weather conditions. Compared with original bamboo and TiO2/bamboo, the Fe-doped TiO2/bamboo exhibited much higher inhibition ability to mould fungi under the natural environment, which is due to the fact of the red shift of the absorption edge of the Fe-doped TiO2 nanostructures on the bamboo surface. UV-vis DRS also revealed that the band gap of Fe-doped TiO2 nanostructures was obviously decreased, extending the light response of TiO2 from ultraviolet to the visible light region. The research result may provide a general and effective approach to prepare visible-light-driven photocatalysts used for inhibition of the growth of mould fungi on the surface of bamboo.

Flame retardant and visible light-activated Fe-doped TiO

The purpose of this study is to evaluate the influence of media treatments on color changes, dimensional stability, and cracking behavior of bamboo scrimber, which has many applications in construction. The bamboo scrimber specimens comprised bamboo bundles with a low molecular weight phenol formaldehyde resin which were manufactured via a cold-in and cold-out hot-pressing process. Small clear specimens were sampled and treated under ten different conditions: water immersion at 25°C, 63°C, and 100°C; oil immersion at 100°C and 150°C; air drying at 63°C, 100°C, and 150°C; and infrared drying at 100°C and 150°C. Then, tests were conducted to determine the color changes, dimensional stability, and cracking behavior of the bamboo scrimbers. The results showed that the bamboo scrimber specimens became darker after all treatment conditions, especially the oil treatments and infrared drying. The color of the oil-treated bamboo scrimbers was found to be more homogenous than the others. The dimensional stability of the bamboo scrimbers was more or less influenced by the water treatments, air drying, and infrared drying, and the oil-treated bamboo scrimbers were relatively stable. Moreover, during the 4-hour treatments, cracks were found in the bamboo scrimbers after air drying at 150°C or infrared drying at 100°C or 150°C.

Outdoor bamboo-fiber-reinforced composites (OBFRCs) with four different densities were prepared, and the microstructure and physicomechanical properties of pristine samples were evaluated. In addition, the surface color, glossiness, roughness, water absorption, and wettability of the samples were tested to investigate the effects of panel density on the extent of surface weathering due to ultraviolet radiation. The results showed that the OBFRCs exhibited excellent physical and mechanical properties, which improved with increasing density. However, increases in the density led to decreases in the hygroscopicity and dimensional stability of the OBFRCs. After weathering, the surface contact angle and surface roughness increased, and the dimensional stability improved. The surface glossiness, water absorption, and surface free energy decreased. A higher density resulted in improved color stability, which suggested that density played an important role in determining surface photodegradation properties. Thus, density-increasing treatments had positive effects on the physical and mechanical properties as well as the color stability and wettability of the OBFRCs, but they may negatively affect the roughness and dimensional stability. Based on service-performance and cost-minimization considerations, 1.1 g/cm3 was determined as the most appropriate density for general applications.

A facile method to synthesize ZnO-TiO2-layered double-nanostructures with the average thickness of 20 &mu, m on a bamboo substrate was proposed to improve the antifungal and flame-retardant properties. The cross-linked wurtzite ZnO nanostructures with an average thickness of approximately 0.14 &mu, m were uniformly distributed on the anatase TiO2 surface. The energy-dispersive X-ray spectroscopy (EDS) confirmed that the ZnO-TiO2 coating on bamboo was a layered double nanostructure. 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. Furthermore, 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 (ROS) of &bull, O2&minus, and &bull, OH were produced from the ZnO-TiO2 surface under visible light irradiation (&lambda, &gt, 420 nm). This large quantity of &bull, compared to &bull, OH is considered to be mainly responsible for the inactivation of fungi. Additionally, the limiting oxygen index 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.