Polydopamine-Doped Porous Nano-CaCO3-Supported Green Tablets for the Humidity-Responsive Intelligent Release of Active Ingredients and Control of Grain Storage Pests

Green tablets for grain storage are urgently required, and intelligently controlled release of active ingredients based on functional nanomaterials is a promising strategy for the preparation of green and high-efficiency tablets. In this work, a polydopamine-doped nano-CaCO3 (nanoPCaCO3) with a diameter of 60–88 nm was prepared by a gas diffusion pore-opening strategy. The porous nanoPCaCO3 exhibited superior encapsulation capacity toward phenolic and ketone compounds based on pore filling, hydrogen bonding, and π–π interactions. After functional disintegrants and excipient addition, two kinds of nanoPCaCO3 tablets containing carvacrol (18.0%) and carvone (16.7%) were prepared, which had a novel humidity-controlled release mode based on the humidity-responsive reaction between nanoPCaCO3 and hygroscopic solid acids. At low relative humidity (RH), grain storage pests were hard to survive, and the release rates of active ingredients in the tablets were slow; at high RH, grain storage pests grew well, and the release rates of active ingredients were accelerated correspondingly. As a result, the 7 day cumulative release ratios of carvacrol and carvone from the tablets at 75% RH were approximately 3 times that at 40% RH. Besides, the tablets exhibited desirable fumigation activity; at 75% RH, the 19 day inhibition ratio against Aspergillus flavus attained 73.7%, and the 7 day fumigation mortality against Sitophilus zeamais reached 92.7%. The tablets can be efficiently used for grain storage pest control, and the porous nanoPCaCO3-supported humidity-controlled release mode can be extended for more high efficiency and functional medicament development.