Fully Biodegradable Packaging Films for Fresh Food Storage Based on Oil-Infused Bacterial Cellulose

Fully biodegradable packaging materials are demanded to resolve the issue of plastic pollution. However, the fresh food storage performance of biodegradable materials is generally much lower than that of plastics due to their high permeability, microbial friendliness, and limited stretchability and transparency. Here a biodegradable packaging material is reported with high fresh food storage performance based on an oil-infused bacterial cellulose (OBC) porous film. The oil infusion significantly improved cellulose's food-keeping performance by reducing its gas permeability, increasing its stretchability and transparency, and enabling the active release of green vapor-phase preservative molecules, while maintaining its intrinsically high degradability. Strawberries stored in a container with the OBC lid at 23 °C after 5 days exhibited a moldy rate of 0%, in contrast to the 100% moldy rate of those stored by poly(ethylene). Enhanced storage performance is also obtained on tomatoes, pork, and shrimp. The OBC film is naturally degraded after being buried in wet soil at 30 °C for 9 days, identical to the degradation rate of bacterial cellulose. The liquid seal strategy broadly applies to different celluloses, providing a general option for developing cellulose-based biodegradable packaging materials.

Topological insulator as an efficient catalyst for oxidative carbonylation of amines

Topological materials have received much attention because of their robust topological surface states, which can be potentially applied in electronics and catalysis. Here, we show that the topological insulator bismuth selenide functions as an efficient catalyst for the oxidative carbonylation of amines with carbon monoxide and dioxygen to synthesize urea derivatives. For example, the carbonylation of butylamine can be completed over bismuth selenide nanoparticle catalyst in 4 hours at 20°C with a yield of 99%, whereas most noble metal-based catalysts do not function at such a low temperature. Density functional theory calculations further reveal that the topological surface states facilitate the activation of dioxygen through a triplet-to-singlet spin-conversion reaction, in which active oxygen species are formed with a barrier of 0.4 electron volts for the subsequent reactions with amine and carbon monoxide.