Advantages of Stimuli-responsive Surfactant Gel for Removal of Nanomaterials from Water

Abstract

Amphiphilic compounds that contain both hydrophobic tails and hydrophilic heads can assemble in suitable media such as water. Recently, supramolecular gels of amphiphiles have attracted much attention in applications for manipulation of nanomaterials. These lamellar-structured gel assemblies contributes to the capture of various functional materials that exhibit strong affinity toward the gelators. This unique property can also be utilized in recovery systems of nanomaterials, such as purification of heavy metal resources or treatment of waste water. Interestingly, amphiphilic gels are often able to undergo a sol-gel transition by external stimuli, and it is also speculated that they allow reversible manipulation of the recovery of nanomaterials. In this paper, the pH-induced removal and recovery of nanomaterials was introduced, such as noble-metal nanoparticles and organic dyes, using a pH-responsive amphiphiles, CnCA. CnCA formed gel-like assemblies at around isoelectric point, due to the interactions between amino moieties and carboxyl groups. The assemblies successfully incorporate various nanomaterials throughout sol-gel transition and remove them from the aqueous suspension.