Cellulose Iβ microfibril interaction with pristine graphene in water: Effects of amphiphilicity by molecular simulation

Advanced Molecular Dynamics Model for Investigating Biological-Origin Microfibril Structures

Understanding the atomic-scale structure of wood microfibrils is essential for establishing fundamental properties in various wood-based research aspects, including moisture impact, wood modification, and pretreatment. In this study, we employed molecular dynamics simulations to investigate the arrangement of wood polymers, including cellulose, hemicellulose, and lignin, with a primary focus on the composition of softwood, specifically Norway Spruce wood. We assessed the accuracy of our molecular dynamics model by comparing it with available experimental data, such as density, Young's modulus, and glass transition temperature, which ensures the reliability of our approach. A key aspect of our study involved modeling the active sorption site for water interaction with wood polymers. Our findings revealed that the interaction between water and hemicellulose, particularly within the hemicellulose-cellulose interphase, was the most prominent binding site. This observation aligns with prior research in this field, further strengthening the validity of our results.

Elucidation of temperature-induced water structuring on cellulose surfaces for environmental and energy sustainability

Optimizing drying energy in the forest products industry is critical for integrating lignocellulosic feedstocks across all manufacturing sectors. Despite substantial efforts to reduce thermal energy consumption during drying, further enhancements are possible. Cellulose, the main component of forest products, is Earth's most abundant biopolymer and a promising renewable feedstock. This study employs all-atom molecular dynamics (MD) simulations to explore the structural dynamics of a small Iβ-cellulose microcrystallite and surrounding water layers during drying. Molecular and atomistic profiles revealed localized water near the cellulose surface, with water structuring extending beyond 8 Å into the water bulk, influencing solvent-accessible surface area and solvation energy. With increasing temperature, there was a ∼20 % reduction in the cellulose surface available for interaction with water molecules, and a ∼22 % reduction in solvation energy. The number of hydrogen bonds increased with thicker water layers, facilitated by a "bridging" effect. Electrostatic interactions dominated the intermolecular interactions at all temperatures, creating an energetic barrier that hinders water removal, slowing the drying processes. Understanding temperature-dependent cellulose-water interactions at the molecular level will help in designing novel strategies to address drying energy consumption, advancing the adoption of lignocellulosics as viable manufacturing feedstocks.

Durable Nanocellulose-Stabilized Emulsions of Dithizone/Chloroform in Water for Hg2+ Detection: A Novel Approach for a Classical Problem

The use of dithizone (DTZ) for colorimetric heavy-metal detection is approximately one century old. However, its pending stability issues and the need for simple indicators justify further research. Using cellulose nanofibers, we attained DTZ-containing emulsions with high stability. These emulsions had water (at least 95 wt %) and acetic acid (1-8 mL/L) conforming the continuous phase, while dispersed droplets of diameter <1 μm contained chloroform-solvated DTZ (3 wt %). The solvation cluster was computed by molecular dynamics simulations, suggesting that chloroform slightly reduces the dihedral angle between the two sides of the thiocarbazone chain. Nanocellulose concentrations over 0.2 wt % sufficed to obtain macroscopically homogeneous mixtures with no phase separation. Furthermore, the rate of degradation of DTZ in the nanocellulose-stabilized emulsion did not differ significantly from a DTZ/chloroform solution, outperforming DTZ/toluene and DTZ/acetonitrile. Not only is the emulsion readily and immediately responsive to mercury(II), but it also decreases interferences from other ions and from natural samples. Unexpectedly, neither lead(II) nor cadmium(II) triggered a visual response at trace concentrations. The limit of detection of these emulsions is 15 μM or 3 mg/L, exceeding WHO limits for mercury(II) in drinking water, but they could be effective at raising alarms.