A facile method to synthesize ZnO-TiO₂-layered double-nanostructures with the average thickness of 20 μm 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 μm 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 •O₂⁻ and •OH were produced from the ZnO-TiO₂ surface under visible light irradiation (λ > 420 nm). This large quantity of •O₂⁻ compared to •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.

Preparation and Characterization of Outdoor Bamboo-Fiber-Reinforced Composites with Different Densities

Surface photostability strongly influences the usefulness of bamboo and bamboo-based polymer composites in outdoor environments. In this study, accelerated aging tests were conducted to investigate how UV irradiation affects the color, surface appearance, and chemical characteristics of outdoor bamboo-fiber-reinforced composite (OBFRC) prepared from moso bamboo (Phyllostachys pubescens Mazel) by a three-step process involving phenol-formaldehyde (PF) resin impregnation. The surface color of natural bamboo (NB) changes rapidly during irradiation, but that of OBFRC remains relatively stable: densification mitigates the negative effects of UV irradiation. More generally, OBFRC exhibits enhanced surface photostability caused by structural and chemical modifications.

Wood-fiber-mat-reinforced composites (WFMRCs) possess excellent physical and mechanical properties and provide high structural performance, making them a suitable engineering structural material. However, WFMRCs are susceptible to biological attack by fungi and insects when they are used in outdoor environments. In this study, the efficacy of copper triazole (CuAz) preservative treatment in protecting WFMRC against decay by white- and brown-rot fungi (Trametes versicolor and Gloeophyllum trabeum, respectively) was evaluated. Both fungi caused a mass loss in the untreated scrimber of more than 15%, while the CuAz preservative treatment reduced the mass loss to 5%. The measurement results show that CuAz treatment could effectively reduce the degradation rate of three major components of wood; inhibit fungal colonization and degradation; and improve the decay resistance of WFMRC. The atmospheric impregnation of CuAz preservative is more suitable for the material features of WFMRC than vacuum impregnation and can be considered for practical industrial applications. This study provides technical support for the protection and outdoor application of WFMRCs.

The process parameters significantly influence the preparation and final properties of outdoor wood mats-based engineering composite (OWMEC). During outdoor use, wood composites are susceptible to destruction by rot fungi. Herein, the role of process parameters such as density and resin content on OWMEC resistance to fungal decay was investigated. The poplar OWMEC samples were exposed to white-rot fungus Trametes versicolor and brown-rot fungus Gloeophyllum trabeum for a period of 12 weeks. The chemical composition, crystallinity, and morphology were evaluated to investigate the effect of process parameters on the chemical composition and microstructure of the decayed OWMEC. With an increase in the density and resin content, the mass loss of the decayed OWMEC decreased. The highest antifungal effect against T. versicolor (12.34% mass loss) and G. trabeum (19.43% mass loss) were observed at a density of 1.15 g/m³ and resin content of 13%. As results of the chemical composition and microstructure measurements, the resistance of OWMEC against T. versicolor and G. trabeum fungi was improved remarkably by increasing the density and resin content. The results of this study will provide a technical basis to improve the decay resistance of OWMEC in outdoor environments.

Soil nitrogen loss through NH₃ volatilization and N₂O emissions is a crucial issue in soil ecosystems. In this study, we explored the effects of biochar and the nitrification inhibitor DMPP (dimethyl-phenyl-piperazinium, a nitrification inhibitor) in vegetable soils under 60 and 200% WHC (water holding capacity). Five treatments were set: CK (control), urea (N), urea + biochar (N + C), urea + nitrification inhibitor (N + DMPP), and urea + nitrification inhibitor + biochar (N + C + DMPP). Results found that biochar promoted soil nitrification and ammonia volatilization under both moisture conditions, with higher NH₃ rate accumulation at 200% WHC. DMPP maintained high NH₄⁺-N concentration and increased soil ammonia volatilization, but effectively reduced N₂O emissions, especially at 200% WHC. The N + C + DMPP treatment further significantly decreased N₂O cumulative emissions compared to N + DMPP. QPCR results showed that N + C treatment significantly increased AOB (ammonia-oxidizing bacteria) copies compared to N treatment. Applying DMPP alone or with biochar reduced AOB copies by 50.0 and 45.7%, respectively. Soil ammonia-oxidizing archaea (AOA) responded oppositely to DMPP; AOA amounts in N + DMPP and N + C + DMPP treatments increased significantly during the culture. At 60% WHC, the greenhouse effect potential of N + DMPP and N + C + DMPP treatments were 39.0 and 43.2% lower than N, respectively. At 200% WHC, their GWP were decreased by 13.8 and 0.08% compared to N. Adding biochar alone increased the soil’s greenhouse potential at both water contents. In conclusion, using nitrification inhibitors alone or in combination with biochar is more effective in reducing the greenhouse effect potential of soil active nitrogen emissions.