Highly efficient dissolution and reinforcement mechanism of robust and transparent cellulose films for smart packaging.

The packaging of fresh foods increasingly focuses on renewable and eco-friendly cellulose films, but their low dissolution efficiency and weak mechanical strength greatly limit their wide application, which also cannot be used for smart packaging. Here, a highly efficient synergistic chloride-salt dissolution method was proposed to fabricate robust, transparent, and smart cellulose films. Cellulose films with appropriate Ca2+ concentration exhibited robust mechanical strength, better thermal stability, high transparency and crystallinity. The metal chelation of Ca2+ with cellulose chains could induce cellulose chain arrangement during the cellulose regeneration process. Particularly, compared to pure cellulose films, the tensile strength and elongation at break of cellulose films with suitable Ca2+ were increased by 167 % and 200 %, respectively. Moreover, optimal cellulose films can be used to reflect the quality of the fruit by detecting changes in ethanol gas. Hence, a novel strategy is presented to fabricate robust and transparent cellulose films with great potential application for smart packaging.

Robust and versatile superhydrophobic cellulose-based composite film with superior UV shielding and heat-barrier performances for sustainable packaging.

Replacing single-use plastic delivery bags (SPDBs) with cellulose-based materials is an effective strategy to reduce environmental pollution. However, the inherent hydrophilicity and ultralow mechanical strength of cellulose materials limit its development. In this study, zinc oxide (ZnO)-cellulose composite films were successfully prepared through "two-step strategy" of lotus leaves structure simulation, including deposition of micro-nano ZnO particles and stearic acid (STA) modification. Well-dispersed micro-nano ZnO particles with stick-like structure were anchored in the ZnO-cellulose composite film prepared at 90 °C (CF-90). Due to the special structural design and strong interaction between the cellulose and micro-nano ZnO particles, the CF-90 showed higher mechanical property (a 47.8 % improvement in the tensile strength). Impressively, CF-90 also exhibited great UV shielding properties with larger UPF value of 1603.98 and superhigh heat-barrier performance. Moreover, CF-90 obtained excellent superhydrophobicity with a water contact angle of 163.6° by further modification. Consequently, the versatile cellulose-based material bringing a dawn on application of sustainable packaging materials for express delivery industry.