Amine-β-cyclodextrin-based nanosponges. The role of cyclodextrin amphiphilicity in the imidacloprid uptake

This paper describes the synthesis, characterization and sorption performance of cyclodextrin nanosponges (NSs). Cyclodextrins are cyclic oligosaccharides with remarkable amphiphilic properties, allowing for a vast range of applications. The synthesis of nanosponges of β-cyclodextrins was carried out using two uncommon cross-linkers: hexane-1,6-diamine (am₆) and dodecane-1,12-diamine (am₁₂). It has been found that the physico-chemical properties of the nanosponges are highly influenced by the chain length of the crosslinker. Nanosponge with crosslinker with shorter chain length is characterized by a higher active surface area (21.8 m² cm⁻¹), pore size (24.3 nm) and structural disorder; on the other hand, the use of am₁₂ leads to a higher thermal stability but lower porosity (7.5 nm), suggesting the occurrence of intermolecular alkyl chain interactions. It can also be concluded that by increasing the crosslinker alkyl chain length, the CD gains additional degrees of freedom and, consequently, a higher structural organization is favored. The more compact structure of the CD-am₁₂-CD led to less available amine groups, consequently it shows a more pronounced response to pH variation. Such properties make the am₆–containing NS a better sorbent for imidacloprid – an active substance used as systemic foliar insecticide and veterinary substance. A preliminary factorial study was performed to determine the effect of several parameters (IMD concentration, amount of sorbent, volume of solution and pH) on sorption abilities of the NSs. Hence, the sorption analysis were performed at the optimal experimental conditions pH 3.8, s/l ratio 5 and 25 °C in which CD-am₆-CD shows the ability for an efficient sorption of the active substance. From the application perspective, the maximum adsorption capability is 68 ± 5 mg g⁻¹ and the removal efficiency is 95%.