Charged nanocellulose (NC) with a high aspect ratio (larger than 100) extracted from animal or bacterial cellulose and chemical cross-linked NC aerogels have great promising applicability in material science, but facile fabrication of such NC aerogels from plant cellulose by physical cross-linking still remains a major challenge. In this work, carboxylated cellulose nanofiber (CNF) with the highest aspect ratio of 144 was extracted from wasted ginger fibers by a simple one-step acid hydrolysis. Our approach could easily make the carboxylated CNF assemble into robust bulk aerogels with tunable densities and desirable shapes on a large scale (3D macropores to mesopores) by hydrogen bonds. Excitingly, these CNF aerogels had better compression mechanical properties (99.5 kPa at 80% strain) and high shape recovery. Moreover, the CNF aerogels had strong coagulation-flocculation ability (87.1%), removal efficiency of MB dye uptake (127.73 mg/g), and moderate Cu absorption capacity (45.053 mg/g), which were due to assistance mechanisms of charge neutralization, network capture effect, and chain bridging of high aspect ratio carboxylated CNF. This provided a novel physical cross-linking method to design robust aerogels with modulated networked structures to be a general substrate material for industrial applications such as superabsorbent, flocculation, oil-water separation, and potential electrical energy storage materials.

A simple and eco-friendly Fe2+/H2O2 oxidation of microcrystalline celluloses (MCCs) to prepare cellulose nanocrystals (CNCs) with high carboxylation content is proposed. The effects of reaction times on the morphology, microstructure, and chemical and thermal properties of isolated carboxylated CNCs were investigated. The oxidative decomposition of Fe2+/H2O2 solution of MCC yielded CNCs with a size of 92–140 nm in length and 19–23 nm in width. The CNCs extracted at 6 h possessed the highest carboxyl content (2.2 mmol/g) with a zeta potential of −41 mV and a thermal decomposition temperature of greater than 325 °C. These CNCs are efficient adsorbents for dyes (methylene blue) and metal ions (copper ion) found in wastewater, with removal rates of up to 95.6 and 82.3%, respectively.

No abstract

Spherical cellulose nanocrystals (SCNs) and rod-shaped cellulose nanocrystals (RCNs) were extracted from different cellulose materials. The two shape forms of cellulose nanocrystals (CNs) were designed with a combination of isothiocyanate (FITC), and both the obtained FITC-SCNs and FITC-RCNs exhibited high fluorescence brightness. The surfaces of SCNs and RCNs were subjected to a secondary imino group by a Schiff reaction and then covalently bonded to the isothiocyanate group of FITC through a secondary imino group to obtain fluorescent cellulose nanocrystals (FITC-CNs). The absolute ζ-potential and dispersion stability of FITC-CNs (FITC-SCNs and FITC-RCNs) were improved, which also promoted the increase in the fluorescence quantum yield. FITC-RCNs had a fluorescence quantum yield of 30.7%, and FITC-SCNs had a morphological advantage (better dispersion, etc.), resulting in a higher fluorescence quantum yield of 35.9%. Cell cytotoxicity experiments demonstrated that the process of FITC-CNs entering mouse osteoblasts (MC3T3) did not destroy the cell membrane, showing good biocompatibility. On the other hand, FITC-CNs with good dispersibility can significantly enhance poly(vinyl alcohol) (PVA) and poly(lactic acid) (PLA); their mechanical properties were improved (the highest sample reached to 243%) and their fluorescent properties were imparted. This study provides a simple surface functionalization method to produce high-luminance fluorescent materials for bioimaging, multifunctional nanoenhancement/dispersion marking, and anticounterfeiting materials.

Shape-stable solid−solid phase-change material (PCM) has attracted much attention due to its excellent thermal properties and shape stability. In this study, cellulose nanocrystal (CNC) was introduced as a high thermal-conductivity nanoskeleton material, and polyethylene glycol (PEG) was used as a solid−liquid phase-change functional material. A green, simple aqueous phase radical polymerization method was used to synthesize shape-stable CNC-based solid−solid phase-change material. The effect of different reaction times on the chemical structure, crystallization ability, thermal stability, and phase transformation properties of the PCM was investigated. All PCM samples showed excellent thermal stability when the temperature was lower than 300 °C. In particular, the synthesized PCM at 12 h had a melt phase transition temperature of 47.1 °C and a phase transition enthalpy up to 82.3 J/g. In addition, the phasechange enthalpy and temperature of PCM-12h did not change significantly after 120 heating and cooling scans. The PCM-12h showed thermal reliability, shape stability, controlled phase-change behaviors, and good heat storage/release properties after thermal treatment. The PCM has potential applications in smart heat storage and temperature control textiles/clothes, building insulation materials, and other energy storage fields.