Preparation of novel all-lignin microcapsules via interfacial cross-linking of pickering emulsion

Lignin based microcapsules are highly attractive for protect easy photolysis substances. However, so far, all-lignin microcapsules prepared with water-soluble lignin are not satisfactory in terms of wall thickness and mechanical properties. Herein, we fabricated a novel all-lignin microcapsules (ALMC) by using 1,6-dibromohexane or epichlorohydrin to crosslink lignin particles adsorbed at the Pickering emulsion droplets interface. 1, 6-Dibromohexane demonstrated a stronger cross-linking activity than epichlorohydrin, and could be used in less dosage and at lower temperatures. The shell thickness of ALMC was about 300 nm. Further analysis confirmed that the shell had a double-layer structure, the outer layer was rough and shrinking and the inner layer was smooth and dense. ALMC can be used to encapsulate hydrophobic substances, and a photosensitive pesticide avermectin (AVM) was chosen to be sealed as model object. The AVM-encapsulated ALMC showed ideal sustained-release performance, namely releasing slowly in the early stage without affecting the overall release. After 70 h of UV irradiation, 93.7 % of AVM was retained, while the original AVM without encapsulation almost all of them was photodegraded, which means that the ultraviolet absorption property of lignin provides excellent protection for the core materials.