Green and sustainable nanoformulation of tebuconazole based on capsules of bionanocomposites halloysite/alginate

In this work, the synthesis of bionanocomposites based on halloysite/alginate with the fungicide tebuconazole (Tbz), as an active ingredient and its application as nanoformulation, was studied. The resultant nanoformulations were friendly to the environment and can be an alternative to increase the yiel of agricultural fields. To achieve this, the surface of the halloysite (Hal) was modified by the adsorption of five surfactants (one cationic and four nonionic) to obtain an organophilic organohalloysites (OHal). Adsorption isotherms and FTIR characterization demonstrated that OHal was obtained due to hydrogen bonding interactions between the nonionic surfactants and the Si-OH and Al-OH groups of the Hal, as well as due to cation exchange with the cationic surfactant. The Tbz was encapsulated in the OHal by adsorption. The mass of Tbz adsorbed was 6.73, 2.92, 4.41, 2.19, and 1.86 mg/g for the OHal with Span 20, Span 80, Tween 80, Tween 85, and HDTMA, respectively. This demonstrated that the surfactants with the highest uptake capacity in OHal have the lowest HLB (hydrophilic–lipophilic balance). The release kinetics of Tbz in the OHal occurred rapidly (approximately in 2 days), regardless of the surfactant type. Once encapsulated the Tbz with the alginate, the release time occurred between 5 and 15 days, decreasing the released quantity between 50 and 75%, evidencing a slow release and greater kinetics control. The confrontation of nanoformulations vs. Fusarium spp. delayed the fungus growth, like commercial tebuconazole does, corroborating the antifungal effect of the material, even though the nanopesticide synthesized in this work has 20 times less Tbz.