Multifunctional hollow silica carriers with spiny structure for enhanced foliar adhesion and triple-responsive pesticide delivery

Intelligent responsive pesticide formulations hold great promise for enhancing foliage retention and effective utilization. Herein, hollow silica (S-HS) nanocarriers with spiny structure were constructed for pesticide delivery. The S-HS nanocarriers presented homogeneous spiny spheres with an average size of 220 nm. This spiny structure can achieve effective retention on foliage by the "hanger-hat" topology effect. For constructing the responsive layer, the S-HS nanocarriers were further functionalized with surface vinyl groups. After loading imidacloprid (IMI), the temperature sensitive poly N-isopropylacrylamide (pNIPAm) and tannic acid–Fe complexes (TA-Fe) were introduced to encapsulate pesticides (IMI@S-HS-pNT). The TA-Fe complex layer served as a wall material and photothermal agent. The S-HS-pNT carriers achieved a loading capacity for IMI (26.6 %), high photothermal conversion effect (η = 36.1 %), and good biocompatibility. Except for excellent photostability and foliar adhesion property, the IMI@S-HS-pNT exhibited pH, temperature and near infrared (NIR) responsive release behavior. Moreover, the S-HS nanocarriers could be effectively transported to various parts of tobacco plants under the root immerse or foliar spray. The IMI@S-HS-pNT showed the high control efficacy against Plutella xylostella. Overall, this work provides insight into improving the efficiency of utilization and prolonging pesticide retention on plant leaves.