Self-assembly of sodium and potassium betulinates into hydro- and organo-gels: entrapment and removal studies of fluorophores and synthesis of gel-gold nanoparticle hybrid materials

Sodium and potassium salts of a renewable nano-sized triterpenoid betulinic acid have been prepared and their self-assembly properties in water and aqueous solvent mixtures have been studied. Both the salts were excellent hydrogelators as well as gelators of aqueous solvent mixtures. The morphologies of the self-assemblies, characterized by optical and electron microscopy, revealed fibrillar networks having fibers of nano-to micrometer diameters. The thermodynamic parameters calculated for the gel to sol transition indicated the stability of the gels. Hydrogels of both sodium and potassium betulinates have been utilized for the entrapment and removal of rhodamine-B in an aqueous medium. Gel-gold nanoparticle hybrid materials have also been prepared by in situ generated gold nanoparticles at room temperature.