Amino Acid Based Low-Molecular-Weight Ionogels as Efficient Dye-Adsorbing Agents and Templates for the Synthesis of TiO2 Nanoparticles

The gelation of ionic liquids is attracting significant attention because of its large spectrum of applications across different disciplines. These green solvents' have been the solution to a number of common problems due to their eco-friendly features. To expand their applications, the gelation of ionic liquids has been achieved by using amino acid-based low-molecular weight compounds. Variation of individual segments in the molecular skeleton of the gelators, which comprise the amino acid and the protecting groups at the N and C termini, led to an understanding of the structure-property correlation of the ionogelation process. An aromatic ring containing amino acid-based molecules protected with a phenyl or cyclohexyl group at the N terminus were efficient in the gelation of ionic liquids. In the case of aliphatic amino acids, gelation was more prominent with a phenyl group as the N-terminal protecting agent. The probable factors responsible for this supramolecular association of the gelators in ionic liquids have been studied with the help of field-emission SEM, H-1 NMR, FTIR, and luminescence studies. It is the hydrophilic-lipophilic balance that needs to be optimized for a molecule to induce gelation of the green solvents. Interestingly, to maximize the benefits from using these green solvents, these ionogels have been employed as templates for the synthesis of uniform-sized TiO2 nanoparticles (25-30 nm). Furthermore, as a complement to their applications, ionogels serve as efficient adsorbents of both cationic and anionic dyes and were distinctly better relative to their organogel counterparts.