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High-performance and useful graphene oxide (GO) and cellulose nanocrystals (CNCs) are easily extracted from natural graphite and cellulose raw materials, and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is produced by bacterial fermentation from natural plant corn stalks, etc. In this study, novel ternary nanocomposites consisting of PHBV/ cellulose nanocrystal-graphene oxide nanohybrids were prepared via a simple solution casting method. The synergistic effect of CNC with GO nanohybrids obtained by chemical grafting (CNC-GO, covalent bonds) and physical blending (CNC/GO, noncovalent bonds) on the physicochemical properties of PHBV nanocomposites was evaluated and the results compared with a single component nanofiller (CNC or GO) in binary nanocomposites. More interestingly, ternary nanocomposites displayed the highest thermal stability and mechanical properties. Compared to neat PHBV, the tensile strength and elongation to break increased by 170.2 and 52.1%, respectively, and maximum degradation temperature (T max ) increment by 26.3 °C, were observed for the ternary nanocomposite with 1 wt % covalent bonded CNC-GO. Compared to neat PHBV, binary, and 1:0.5 wt % noncovalent CNC/GO based nanocomposites, the ternary nanocomposites with 1 wt % covalent bonded CNC-GO exhibited excellent barrier properties, good antibacterial activity (antibacterial ratio of 100.0%), reduced barrier properties, and lower migration level for both food simulants. Such a synergistic effect yielded high-performance ternary nanocomposites with great potential for bioactive food packaging materials.

Cellulose nanocrystals (CNCs) have great potentials in many applications, such as high-performance nanocomposites. However, there are many challenges in the industrial production of CNCs, such as high cost of acid recovery, acid disposal, low yield, and poor thermal stability. In this study, a simple process to extract CNCs via recyclable acid hydrolysis of microcrystalline cellulose (MCC) is presented. A high yield (up to 87.8%) of carboxylated CNCs was obtained using recyclable citric/hydrochloric acid mixtures compared to the 53.9% yield for sulfated CNCs via recyclable H2SO4 hydrolysis. The mild acid mixtures could be readily recovered and recycled three times and showed a slight effect on the size of CNCs, carboxyl content of citrate CNC surface, zeta potential value, and thermal stability. Both charged citrate CNCs and sulfate CNCs were excellent food Pickering emulsion stabilizers for soybean oil/water emulsion droplets, whose diameter decreased with increasing CNC contents. This work provides a simple and low-cost pathway to recover mineral or organic acids for the sustainable and green production of CNCs with high yield and thermal stability while addressing the environmental issue of acid disposal in large-scale production of CNCs.

The uses of inorganic metal oxide and ZnO nanohybrids as UV absorbers have potential to increase the production of UVprotective textile, which will also overcome the drawbacks of organic molecules and prevent negative impacts on human health and environment. In this work, sheet-like cellulose nanocrystal-ZnO (CNC-ZnO) nanohybrid was successfully developed by one-step hydrothermal method. The obtained CNC-ZnO nanohybrids as UV absorber and antibacterial agents were introduced into biopolyester (poly(3-hydroxybutyrate-co-3-hydroxy valerate, PHBV) by using electrospinning process. The addition of sheet-like CNC-ZnO can greatly enhance PHBV thermal stability and crystallization ability. In addition, excellent antimicrobial ratios of Escherichia coli and Staphylococcus aureus and high absorbency of solution A (9.82 g/g) were obtained for the composite nanofibers with 5 wt % CNC-ZnO. Moreover, most of the UV irradiations were blocked out for both UVA (99.72%) and UVB (99. 95%) with high UPF value of 1674.9 in the resulting composite nanofibers with 9 wt % CNC-ZnO. This study provides a novel method to produce sheet-like CNC-ZnO with multifunctional properties and its nanocomposite for potential uses as wound dressings and other functional biomaterials.