In temperature sensitive hydrogels, the swelling degree or light transmittance of the gel itself changes with variations in ambient temperature, prompting its wide application in controlled drug release, tissue engineering, and material separation. Considering the amphiphilic structure of β-cyclodextrin (β-CD), a cellulose-based supramolecular hydrogel with superior temperature sensitivity was synthesized based on a combination of cellulose and β-CD as well as the host–guest interaction between β-CD and polypropylene glycol (PPG). In the one-pot tandem reaction process, chemical grafting of β-CD on cellulose and the inclusion complexation of β-CD with PPG were performed simultaneously in a NaOH/urea/water system. The obtained supramolecular hydrogel had a lower critical solution temperature (LCST) of 34 °C. There existed covalent bonding between the cellulose and β-CD, host–guest complexation between the β-CD and PPG, and hydrogen bonding and hydrophobic interactions between the components in the network structure of the supramolecular hydrogel. The combination of various covalent and non-covalent bonds endowed the resulting supramolecular hydrogel with good internal network structure stability and thermal stability, as well as sensitive temperature responsiveness within a certain range—implying its potential as a smart material in the fields of medicine, biology, and textiles. This work is expected to bring new strategies for the fabrication of cellulose-based thermosensitive materials, benefitting the high-value utilization of cellulose.

The high mechanical strength, large specific surface area, favorable biocompatibility, and degradability of nanocellulose (CNC) enable it to be a potential alternative to petroleum-based materials. However, the traditional preparation of CNCs requires a large amount of strong acid, which poses a serious challenge to equipment maintenance, waste liquid recycling, and economics. In this study, a solid and easily recoverable zirconium phosphate (ZrP) was used to assist in the phosphoric acid co-catalyzed hydrolysis of lignocellulose for extracting CNCs. Due to the presence of acidic phosphate groups, ZrP has a strong active center with a high catalytic activity. With the assistance of ZrP, the amount of phosphoric acid used in the reaction is significantly reduced, improving the equipment’s durability and economic efficiency. The effects of the process conditions investigated were the phosphate acid concentration, reaction temperature, and reaction time on the yield of CNCs. The Box–Behnken design (BBD) method from the response surface methodology (RSM) was applied to investigate and optimize the preparation conditions. The optimized pre-treatment conditions were 49.27% phosphoric acid concentration, 65.38 °C reaction temperature, and 5 h reaction time with a maximal cellulose yield (48.33%). The obtained CNCs show a granular shape with a length of 40~50 nm and a diameter of 20~30 nm, while its high zeta potential (−24.5 mV) make CNCs present a stable dispersion in aqueous media. Moreover, CNCs have a high crystallinity of 78.70% within the crystal type of cellulose Ⅰ. As such, this study may pioneer the horizon for developing a green method for the efficient preparation of CNC, and it is of great significance for CNCs practical production process.

Based on the self-passivation function of chitosan, an efficient, and green synthesis strategy was applied to prepare chitosan carbon dots (CDs). The quantum yield of carbon dots reached 35% under the conditions of hydrothermal temperature of 200 °C, hydrothermal time of 5 h, and chitosan concentration of 2%. Moreover, the obtained carbon dots had high selectivity and sensitivity to Fe³⁺. Based on the Schiff base reaction between the aldehyde groups of dialdehyde cellulose nanofibrils (DNF) and the amino groups of CDs, a chemically cross-linked, novel, fluorescent composite film, with high transparency and high strength, was created using one-pot processing. Knowing that the fluorescence effect of the composite film on Fe³⁺ had a linear relationship in the concentration range of 0–100 μM, a fluorescent probe can be developed for quantitative analysis and detection of Fe³⁺. Owing to their excellent fluorescent and mechanical properties, the fluorescent nanocomposite films have potential applications in the fields of Fe³⁺ detection, fluorescent labeling, and biosensing.