Jia Wang

This study developed a novel material based on polyvinyl alcohol–ethylene glycol (PVA-EG) hydrogel and systematically evaluated its potential application in the removal of animal glue from book surfaces. The microstructure, surface properties, and mechanical characteristics of the PVA-EG hydrogel were analyzed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), contact angle measurements, a universal testing machine, and a dynamic mechanical analysis (DMA). The introduction of ethylene glycol (EG) could weaken hydrogen bonding interactions between PVA chains to enhance the molecular chain flexibility of the hydrogel. Notably, the 10% PVA-EG hydrogel shows better crystallinity, higher hydrophilicity, and optimal balance between mechanical strength and flexibility compared to pure PVA, which is conducive to improving the efficiency of the removal of animal glue. Additionally, the effectiveness of the process of removing animal glue was verified by real-time monitoring using europium nitrate at a concentration of 0.4% (w/v) as a fluorescent marker. Such hydrogels with high mechanical properties, strong surface hydrophilicity, good removal efficiency, and gentle treatment characteristics have potential applications in the restoration of cultural heritage.

The presence of harmful oxidizing gases accelerates the oxidation of cellulose fibers in paper, resulting in reduced strength and fading ink. Therefore, the development of highly sensitive NO₂ gas sensors for monitoring and protecting books holds significant practical value. In this manuscript, ZnO/MoS₂ composites were synthesized using sodium molybdate and thiourea as raw materials through a hydrothermal method. The morphology and microstructure were characterized by X-ray diffraction analysis (XRD), energy dispersive spectroscopy (EDS), field emission scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The ZnO/MoS₂ composite exhibited a flower-like structure, with ZnO nanoparticles uniformly attached to the surface of MoS₂, demonstrating advantages such as high specific surface area and good uniformity. The gas sensitivity of the ZnO/MoS₂ nanocomposites reached its peak at 260 °C, with a sensitivity value around 3.5, which represents an improvement compared to pure ZnO, while also enhancing sensitivity. The resistance of the ZnO/MoS₂ gas sensor remained relatively stable in air, exhibiting short response times during transitions between air and NO₂ environments while consistently returning to a stable state. In addition to increasing adsorption capacity and improving light utilization efficiency, the formation of hetero-junctions at the ZnO-MoS₂ interface creates an internal electric field that effectively promotes the rapid separation of photo-generated charge carriers within ZnO, thereby extending carrier lifetime.

Monitoring the gas composition in library environments is crucial for the preservation of ancient books. In this study, TiO₂ NTs/CNTs composites were synthesized via a hydrothermal method and utilized as nano-gas sensors for NO₂ detection. The surface morphology and element composition of the samples were characterized using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Additionally, the gas sensitivity of the prepared TiO₂ nanocomposites was evaluated at different temperatures, both with and without ultraviolet light irradiation. The results demonstrate that the synthesized TiO₂ NTs/CNTs samples exhibit a large specific surface area due to their titanium dioxide nanotubes (TiO₂ NTs) and carbon nanotubes (CNTs) composition. Moreover, these samples display excellent gas sensitivity under ultraviolet light irradiation at temperatures of 120 °C. Compared to uncomposited and non-ultraviolet light irradiated samples, the sensor response rate is significantly improved, enabling effective monitoring of NO₂ gas in library environments conducive to preserving ancient books. Overall, our findings highlight that the developed TiO₂ NTs/CNTs nano gas sensor holds great potential for monitoring and safeguarding ancient books.

NO₂ is a prevalent environmental pollutant, and its reaction with water produces nitric acid, which is one of the main factors contributing to the degradation of books and paper. Therefore, it is crucial to develop a real-time monitoring system for NO₂ gas content in the air and establish timely response measures to delay book aging and provide effective protection. In this study, TiO₂ nanotubes (NTs) were fabricated using the anodic oxidation method, followed by the preparation of TiO₂ NT/MoS₂ composites through hydrothermal synthesis. It was observed that flaky MoS₂ is attached to the surface of TiO₂ nanotubes, forming aggregated structures resembling flower balls. The TiO₂ NT/MoS₂ nanocomposites were found to exhibit a rapid response with a 5 s response time and an 80 s recovery time towards 367 ppm NO₂ at 260 °C. The gas response to 100 ppm NO₂ vapor was 3.3, which is higher than all the other gases under the same concentration. Our experimental results demonstrate that compared to pure TiO₂ NTs, TiO₂ NT/MoS₂ composites exhibit a larger specific surface area along with higher sensitivity and faster response times towards various concentrations of NO₂ gas.