Enhancing nitenpyram surface performance with imidazolium ionic liquids: Adsorption behavior, wettability, and DFT analysis

The present work aims to regulate the solubility of nitenpyram (NTP) through the use of ionic liquids (ILs). Two imidazolium based ILs differing in their chain length, 1-butyl-3-methyl imidazolium chloride (C 4 mimCl) and 1-methyl-3-octyl imidazolium chloride (C 8 mimCl), were chosen and their interactions with the insecticide NTP were investigated. Through UV–vis spectroscopy and density functional theory (DFT) results, it was observed that C 8 mimCl exhibited better binding with NTP as compared to C 4 mimCl, as depicted from the higher binding constant value, Gibbs free energy of binding and electronic energy of the C 8 mimCl-NTP system. Based on this finding, further studies were carried out for C 8 mimCl and the interaction between C 8 mimCl and NTP was investigated through surface tension and viscosity measurements at 298 K. The results from surface tension measurements suggested that critical micellization concentration (cmc) for the IL decreased in the presence of NTP and the adsorption process was favored over micellization for the C 8 mimCl-NTP system. Moreover, the aggregation number ( N agg ) was determined for the C 8 mimCl-NTP system through fluorescence spectroscopy using the pyrene probe, taking the IL at its pre-cmc, cmc and post-cmc concentrations and maximum N agg was observed taking IL at its cmc value. Additionally, the wettability studies were conducted through static contact angle measurements on the adaxial and abaxial leaf surfaces of various plants of medicinal value and it was ascertained that the C 8 mimCl-NTP system manifested higher wettability as compared to NTP and C 8 mimCl alone for each of the leaves considered. Overall, the experimental and theoretical calculations support the rational design of sustainable agrochemical formulations. These findings provide insights into the potential role of ILs in modifying the physicochemical behavior of NTP.