Lignin is an indispensable and essential compound present in plants. It is a renewable resource and a green alternative to traditional petroleum energy. The rational utilization of lignin can reduce the environmental damage caused by traditional industrial development. The preparation of lignin nanoparticles (LNPs) using the self-assembly method is one of the most favorable ways to achieve high value-added utilization of lignin. However, the process requires an in-depth understanding of the sphere-forming mechanism of lignin self-assembly and the interaction of self-assembly forces. We used the same raw materials and two different preparation methods to prepare LNPs. The results revealed that the variation in the order of the dropwise addition of lignin solution and deionized water produced LNPs with varying average sizes. The sphere-forming mechanisms of the two kinds of lignin nanoparticles were discussed for the preparation of UV-resistant polyvinyl alcohol (PVA) polymeric films. During lignin spherification, the faster the solution reaches the supersaturation state, the faster the spherogenesis rate is, the smaller the size is, and the narrower the particle size distribution is. The lignin micro/nanospheres are produced by exploiting the π–π bonding interactions in lignin itself. The lignin micro/nanospheres are then mixed with PVA to form a film to obtain a lignin–PVA composite film material with an anti-UV effect.

There are plant cuticle and complex cell walls on the outer surface of cotton stalk bark (CSB), which reduce the efficiency of liquid penetration of CSB. To increase the permeability of liquids, these barriers need to be broken. Cellulase can selectively hydrolyze cellulose into glucose, and its action conditions are mild. Therefore, cellulase treatment is one of the excellent ways to break the CSB liquid permeation barrier. This experiment studied the effects of different amounts of cellulase treatment on the enzymatic hydrolysis products and surface of CSB. Scanning electron microscopy (SEM) and nano-CT were used to observe the changes in the microscopic morphology of CSB. Ion chromatography and an ultraviolet–visible spectrophotometer were used to determine the dissolution of CSB. The results showed that the cuticle of CSB treated with cellulase was broken, and the cell wall of phloem fibers became thinner, which increased the accessibility of liquid. The content of monosaccharide and lignin in CSB treatment solution increased with the increase of cellulase dosage. Correspondingly, the proportion of polysaccharides on the outer surface of CSB continued to decline and eventually stabilized. These experimental results can provide a reference for improving the permeability of natural fibers and the subsequent treatment effects of biomass products. Graphical abstract The pretreatment of cotton stalk barks with cellulase destroyed the dense protective structure of cell wall, and the content of monosaccharide and lignin in the treated solution increased with the increase of cellulase dosage.