Kinetics and Thermodynamics of Hemicellulose Adsorption onto Nanofibril Cellulose Surfaces by QCM-D

Bioinspired pullulan-starch nanoplatelets nanocomposite films with enhanced mechanical properties

Inspired by the leaf-vein network structure, the pullulan-starch nanoplatelets (SNPs) bioinspired films with enhanced strength and toughness were successfully fabricated through a water evaporation-induced self-assembly technique. SNPs (SNP200 and SNP600) of two sizes were separated by differential centrifugation. Interactions between SNPs and pullulan during drying resulted in the vein-like network structure in both nanocomposite films when the appropriate amounts of SNP200 or SNP600 were added to pullulan, respectively. The TS and toughness values of pullulan with 1 % w/w SNP200 films reached up to 51.05 MPa and 69.65 MJ·m-3, which were 86 % and 223 % higher than those of the neat pullulan films, respectively. Moreover, the TS and toughness values of pullulan-SNP200 were significantly higher than those of pullulan-SNP600 films, when SNP content exceeded the 1 % w/w level. By applying a graph theory, the network structures were found to correlate with the mechanical properties of the pullulan-SNPs bioinspired films. The new strategy for designing starch nanoplatelets-based edible films that combine mechanical strength and toughness holds promises for the development of novel biobased composite materials for food packaging application.

Specific ion effects on lignin adsorption and transport through cellulose confinements

The presence of ions in a solution is anticipated to induce distinct effects on macromolecules. Consequently, the tuning of adsorption and mass transfer of lignin molecules can be achieved by incorporating ions with chaotropic or kosmotropic characteristics. This study examines the adsorption and mass transfer behavior of lignin molecules across model cellulose membranes in presence of ions from the Hofmeister series. Experimental investigations encompassed the use of diffusion cells to quantify lignin's mass transfer through the membranes, and quartz crystal microbalance with dissipation (QCM-D) monitoring was used for adsorption studies. Notably, at high ion concentrations, the mass transport rate of lignin was observed to be lower in the presence of highly hydrated (kosmotropic) sulfate ions, conforming to the Hofmeister series. Intriguingly, this relationship was not apparent at lower ion concentrations. Furthermore, QCM-D experiments indicated that lignin displayed higher adsorption onto the cellulose surface when exposed to less hydrated (chaotropic) nitrate anions. This behavior can be rationalized by considering the system's increased entropy gain, facilitated by the release of adsorbed ions and water molecules from the cellulose surface upon lignin adsorption. This study highlights the complexity of ion-specific effects on mass transfer and adsorption processes and their dependency on ion concentrations.

Structural changes of hemicellulose during pulping process and its interaction with nanocellulose

It is believed that hemicellulose plays a crucial role in binding cellulose and lignin in plant cells. It may provide significant implications through figuring out the interaction between hemicellulose and microfibers and gaining insights how the structure of hemicellulose affects its association with cellulose nanofibers. Herein, the hemicellulose and nanocellulose fractions from pulps obtained by controlling the H-factors of kraft pulping process were quantitatively evaluated for their adsorption behavior using QCM-D. The results showed that harsher cooking (corresponding to high H-factor) significantly affected the chemical composition of hemicellulose, leading to a decrease of its molecular weight and gradually turning it into a linear structure. Hemicellulose possesses a strong natural affinity for CNC-coated sensors. The hemicellulose from the pulp cooked by high H-factor process decreases its ability to adsorb onto nanocellulose, the adsorption rate also slows down, and the conformation of the adsorbed layer changes which makes the binding weak and reversible. In conclusion, the pulping process in high H-factor significantly changed the structure of hemicellulose, leading to a variation in the strength of its interaction with nanocellulose.

Chiral zinc oxide functionalized quartz crystal microbalance sensor for enantioselective recognition of amino acids

Chiral transition metal oxides with tunable structures and multiple physicochemical features have been increasingly applied for chiral sensing and detection. In this work, chiral zinc oxide (ZnO) was first applied as selector to construct quartz crystal microbalance (QCM) sensor for enantioselective recognition of amino acids. The chiral ZnO was prepared by a methionine-induced self-assembly strategy and its high topological chirality was confirmed by several techniques such as circular dichroism spectrum. The chiral discrimination factors were calculated by frequency shifts in response to aspartic acid, phenylalanine, lysine and arginine on L-ZnO surface, achieving 1.89 ± 0.04, 1.76 ± 0.11, 1.66 ± 0.07 and 1.54 ± 0.09, respectively. Notably, L-enantiomers preferred stronger absorptions on L-ZnO surface as compared to D-forms. It was further found that this sensor was appropriate for quantitative analysis and enantiomer excess analysis and adsorption kinetics study. Furthermore, molecular docking revealed the recognition mechanism, where chiral distinction was caused by the different steric interactions between enantiomers and chiral ZnO. This method enjoyed merits of high enantioselectivity, simple preparation and low cost, offering newly chiral sensing method for other molecules.

Hemicellulose and Nano/Microfibrils Improving the Pliability and Hydrophobic Properties of Cellulose Film by Interstitial Filling and Forming Micro/Nanostructure

In this paper, nano/microfibrils were applied to enhance the mechanical and hydrophobic properties of the sugarcane bagasse fiber films. The successful preparation of nano/microfibrils was confirmed by scanning electron microscope (SEM), X-ray diffraction (XRD), fiber length analyzer (FLA), and ion chromatography (IC). The transparency, morphology, mechanical and hydrophobic properties of the cellulose films were evaluated. The results show that the nanoparticle was formed by the hemicellulose diffusing on the surface of the cellulose and agglomerating in the film-forming process at 40 °C. The elastic modulus of the cellulose film was as high as 4140.60 MPa, and the water contact angle was increased to 113°. The micro/nanostructures were formed due to hemicellulose adsorption on nano/microfilament surfaces. The hydrophobicity of the films was improved. The directional crystallization of nano/microfibrous molecules was found. Cellulose films with a high elastic modulus and high elasticity were obtained. It provides theoretical support for the preparation of high-performance cellulose film.