Degradable ZIF-8/silica carriers with accropode-like structure for enhanced foliar affinity and responsive pesticide delivery

The development of novel intelligent pesticide formulations for enhanced foliage deposition and efficient utilization remains a challenge. Accropode stones are general employed to attenuate the impact of waves. Herein, we constructed novel accropode-like carriers based on zeolitic imidazolate framework-8 (ZIF-8) and silica (SiO2) for pesticide delivery with enhanced foliar affinity. Firstly, β-cyclodextrin-doped ZIF-8 (β-CD/ZIF-8) carrier was prepared by a one-pot method. Subsequently, a selective occupation strategy was applied to achieve facet-specific growth of mesoporous SiO2 on β-CD/ZIF-8 (β-CD/ZIF-8@S). The β-CD/ZIF-8@S nanocarriers exhibited regular structure with sixteen facets. The accropode-like structure would achieve effective foliage retention and resistance to rainwater washout by the reduction of carrier bouncing and rolling on foliage. The β-CD/ZIF-8@S presented a high loading efficacy for imidacloprid (IMI) (24.43 %) and good biocompatibility. After loading IMI, tannic acid (TA) was utilized to block the loaded pesticide (IMI@β-CD/ZIF-8@ST). The IMI@β-CD/ZIF-8@ST exhibited dual responsive release behavior and could be effectively transported in both directions in various parts of tobacco plants. The photostability of IMI@β-CD/ZIF-8@ST was 5-times that of IMI solution. Moreover, the insecticidal efficacy against Plutella xylostella of IMI@β-CD/ZIF-8@ST was 80 % after 120 h of UV irradiation, while that of IMI and IMI water dispersible granule was only 23.33 % and 26.67 %, respectively. This work provides new insights into enhancing the foliage retention and efficiency utilization of pesticide.