Multivalent Metal Ion Cross-Linked Lignocellulosic Nanopaper with Excellent Water Resistance and Optical Performance.

Cellulose nanopaper is an attractive film material exhibiting huge potential in various fields, while its terrible water stability greatly hinders practical applications. Previous efforts on addressing this issue usually sacrifice the sustainability or material performance of film. In this study, we report a high-performing lignocellulosic nanopaper with superior water resistance and excellent optical properties. The strategy involves preparing a lignin-containing cellulose nanopaper (LCNP) first, and then infiltrating metal ions into the film to build cross-linking interactions within the fiber networks. Owing to the coordination bonds formed between metal ions and lignocellulosic components, the resulting metal ions cross-linked LCNP (M+-LCNP) displays outstanding water resistance, including the highest wet mechanical strength of ∼52 MPa after immersing in water for 24 h, which retains nearly 47% of the dry mechanical strength of the film. The ultralow water uptake ratio of ∼35% also confirms it possesses a superior wet dimensional stability. Moreover, these nanopapers also showcase the desired optical performances, including both high visible transmittance (>85%) and total ultraviolet-blocking efficiency (>91%, only transmitting a little of UVA). Overall, this fully degradable film is a promising alternative to replacing conventional plastics that are applied in multiple areas.

Flexible and Highly Sensitive Humidity Sensor Based on Cellulose Nanofibers and Carbon Nanotube Composite Film.

Flexible and highly sensitive humidity sensors are crucial for humidity detection. In this study, a flexible cellulose nanofiber/carbon nanotube (NFC/CNT) humidity sensor with high sensitivity performance was developed via fast vacuum filtration. CNTs were well dispersed in water by using 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-oxidized NFC as a dispersant. More importantly, NFC also acted as a humidity sensitive material, achieving superior performance of NFC/CNT humidity sensors. The obtained NFC/CNT humidity sensor with 5 wt % CNT loading exhibits outstanding sensitive performance, and its response value reaches a maximum of 69.9% (Δ I/ I0) at 95% relative humidity (RH). It also displays good bending resistance and long-term stability. In addition, the NFC/CNT humidity sensor was employed to monitor human breath. Therefore, we believe that the flexible, highly sensitive, and simply designed NFC/CNT humidity sensor is a promising candidate for various applications in the field of humidity measurement.

Preparation and characterization of corn starch-based antimicrobial indicator films containing purple corncob anthocyanin and tangerine peel essential oil for monitoring pork freshness.

A novel antibacterial indicator film was prepared by mixing corn starch with tangerine peel essential oil (TEO) Pickering emulsion emulsified by ultrasonic and esterified modified starch (UDSt), and then incorporated with purple corncob anthocyanin (PCA), which was used to monitor the freshness of pork. The results showed that the UDSt can effectively stabilize the TEO emulsion. PCA showed obvious color changes at different pH. With the increase of pH, the color of film changed from red to yellow, and its response to volatile ammonia changed from pink to cyan, showing better response ability. The loading of TEO conferred the film excellent bacteriostatic ability against E. coli and S. aureus. The film also had good ability of light blocking and free radical scavenging. In the process of pork deterioration, the antibacterial indicator film changed from pink to yellow, which was closely related to pork quality and had a good linear indicator correlation. The addition of TEO reduced the release of PCA in the antibacterial indicator film and helped to maintain the functional properties of the film. This type of antibacterial indicator film had considerable application potential in indicating food freshness.