Bio-inspired Janus film derived from lemon biomass with integrated optical authentication and active food preservation.

Ensuring both the nutritional integrity and authenticity of high-value fruits is a critical challenge in the modern global supply chain. Inspired by the asymmetric wettability of lotus leaves, we developed an innovative, multifunctional Janus film (ES/CNT/PC) derived from lemon biomass pectin, chitosan, and ethyl cellulose via a robust top-down assembly strategy. This asymmetric film integrates Ti-doped carbon dots (Ti-NCDs) and citral-loaded hydroxypropyl-β-cyclodextrin complexes to address the dual challenges of physiological decay and fraudulent labeling. Physically, the Janus structure imparts superior surface moisture barrier properties and a tortuous diffusion path, which significantly inhibit transpiration and respiration while providing satisfactory waterproofing and self-cleaning capabilities. Biologically, the sustained release of citral, combined with the inherent bioactivity of Ti-NCDs, constitutes a synergistic active-passive defense system. This system exhibited inhibition zones of 10.67 mm against Escherichia coli and 10.03 mm against Staphylococcus aureus, along with a 1.68-fold increase in free radical scavenging capacity relative to the control. Notably, the integrated Ti-NCDs generate fluorescence upon UV excitation, establishing a non-invasive optical authentication system that enables rapid fluorescent label verification. In preservation trials, the ES/CNT/PC film significantly delayed winter jujube senescence, reducing weight loss to 6.26% and maintaining high firmness (6.60 N) over 6 days. This study provides a sustainable strategy for the integrated preservation and quality assurance of winter jujube.