Improving Biomass-Degradation Properties and Nano-Mechanics of Moso Bamboo via a Simple Nitrogen Heat Treatment

Nitrogen is generally used as a protective gas to provide an oxygen-free environment for the heat treatment of biomaterials. In order to indicate the effect of nitrogen heat treatment of bamboo, the changes in terms of the chemical composition, chemical functional groups, cellulose crystallinity index, surface color, micro-mechanics and anti-mildew properties of bamboo, and the interaction relationship among the properties, were analyzed. The mass loss ratio of treated bamboo samples increased significantly during the process of thermal modification. In detail, the hemicellulose exhibited a decreasing tendency from 23.7% to 16.6%, while the lignin content presented an increasing tendency. The decreased hemicellulose and cellulose contents are a benefit to enhancing lignin content and crystallinity degree, thus increasing the modulus of elasticity and hardness of treated bamboo cell walls. The obtained bamboo sample treated at 190 °C/3 h displayed the best micro-mechanical properties. It presented a maximum modulus of elasticity of 22.1 GPa and a hardness of 0.97 GPa. Meanwhile, the lignin and cellulose content was proven to increase in the bamboo surface in chemical composition analysis, resulting in lower free-hydroxyl groups on the bamboo surface. Thus, the contact angle value of bamboo increased. Furthermore, nitrogen thermal modification positively contributed to the mildew resistance of bamboo specimens

Contributions of Basic Chemical Components to the Mechanical Behavior of Wood Fiber Cell Walls as Evaluated by Nanoindentation

Selective chemical extraction was applied to gradually remove classes of chemical components from wood cell walls. Nanoindentation was performed on the control and treated wood cell walls to evaluate the contributions of the chemical components to the cell walls by measuring the elastic modulus, hardness, and creep compliance. Burger’s model was applied to simulate the process of nanoindentation and to gain insight into the response of visco-elastic properties to the chemical components. Wood extractives showed limited effects on the cell-wall mechanics; however, the removal of hemicelluloses and lignin resulted in reductions of 11.7% and 28.4%, respectively, in the elastic modulus and 14.8% and 30.4%, respectively, in the hardness. The extraction of hemicelluloses and lignin reduced the resistance of wood cell walls to creep. Furthermore, the extracted parameters from Burger’s modeling indicated that cellulose exhibited the greatest influence on the mechanical properties of wood cell wall, while hemicelluloses exhibited the greatest contribution to cell-wall viscosity, and lignin contributed extensively to cell-wall elasticity

Multi-Scale Evaluation of the Effect of Phenol Formaldehyde Resin Impregnation on the Dimensional Stability and Mechanical Properties of Pinus Massoniana Lamb.

The local chemistry and mechanics of the control and phenol formaldehyde (PF) resin modified wood cell walls were analyzed to illustrate the modification mechanism of wood. Masson pine (Pinus massoniana Lamb.) is most widely distributed in the subtropical regions of China. However, the dimensional instability and low strength of the wood limits its use. Thus, the wood was modified by PF resin at concentrations of 15%, 20%, 25%, and 30%, respectively. The density, surface morphology, chemical structure, cell wall mechanics, shrinking and swelling properties, and macro-mechanical properties of Masson pine wood were analyzed to evaluate the modification effectiveness. The morphology and Raman spectra changes indicated that PF resin not only filled in the cell lumens, but also penetrated into cell walls and interacted with cell wall polymers. The filling and diffusing of resin in wood resulted in improved dimensional stability, such as lower swelling and shrinking coefficients, an increase in the elastic modulus (Er) and hardness (H) of wood cell walls, the hardness of the transverse section and compressive strength of the wood. Both the dimensional stability and mechanical properties improved as the PF concentration increased to 20%; that is, a PF concentration of 20% may be preferred to modify Masson pine wood

Improving Biomass-Degradation Properties and Nano-Mechanics of Moso Bamboo via a Simple Nitrogen Heat Treatment

Nitrogen is generally used as a protective gas to provide an oxygen-free environment for the heat treatment of biomaterials. In order to indicate the effect of nitrogen heat treatment of bamboo, the changes in terms of the chemical composition, chemical functional groups, cellulose crystallinity index, surface color, micro-mechanics and anti-mildew properties of bamboo, and the interaction relationship among the properties, were analyzed. The mass loss ratio of treated bamboo samples increased significantly during the process of thermal modification. In detail, the hemicellulose exhibited a decreasing tendency from 23.7% to 16.6%, while the lignin content presented an increasing tendency. The decreased hemicellulose and cellulose contents are a benefit to enhancing lignin content and crystallinity degree, thus increasing the modulus of elasticity and hardness of treated bamboo cell walls. The obtained bamboo sample treated at 190 °C/3 h displayed the best micro-mechanical properties. It presented a maximum modulus of elasticity of 22.1 GPa and a hardness of 0.97 GPa. Meanwhile, the lignin and cellulose content was proven to increase in the bamboo surface in chemical composition analysis, resulting in lower free-hydroxyl groups on the bamboo surface. Thus, the contact angle value of bamboo increased. Furthermore, nitrogen thermal modification positively contributed to the mildew resistance of bamboo specimens

Nanomaterial-Based Fluorescent Biosensor for Food Safety Analysis

Food safety issues have become a major threat to public health and have garnered considerable attention. Rapid and effective detection methods are crucial for ensuring food safety. Recently, nanostructured fluorescent materials have shown considerable potential for monitoring the quality and safety of food because of their fascinating optical characteristics at the nanoscale. In this review, we first introduce biomaterials and nanomaterials for food safety analysis. Subsequently, we perform a comprehensive analysis of food safety using fluorescent biosensors based on nanomaterials, including mycotoxins, heavy metals, antibiotics, pesticide residues, foodborne pathogens, and illegal additives. Finally, we provide new insights and discuss future approaches for the development of food safety detection, with the aim of improving fluorescence detection methods for the practical application of nanomaterials to ensure food safety and protect human health

Nanomaterials-Based Electrochemiluminescence Biosensors for Food Analysis: Recent Developments and Future Directions

Developing robust and sensitive food safety detection methods is important for human health. Electrochemiluminescence (ECL) is a powerful analytical technique for complete separation of input source (electricity) and output signal (light), thereby significantly reducing background ECL signal. ECL biosensors have attracted considerable attention owing to their high sensitivity and wide dynamic range in food safety detection. In this review, we introduce the principles of ECL biosensors and common ECL luminophores, as well as the latest applications of ECL biosensors in food analysis. Further, novel nanomaterial assembly strategies have been progressively incorporated into the design of ECL biosensors, and by demonstrating some representative works, we summarize the development status of ECL biosensors in detection of mycotoxins, heavy metal ions, antibiotics, pesticide residues, foodborne pathogens, and other illegal additives. Finally, the current challenges faced by ECL biosensors are outlined and the future directions for advancing ECL research are presented