Rational Design and Synthesis of Carboxylate Gemini Surfactants with an Excellent Aggregate Behavior for Nano-La₂O₃ Morphology-Controllable Preparation

Abstract

A series of carboxylate gemini surfactants (CGS, C-Φ-C, n = 12, 14, 16, 18) with diphenyl ketone as a spacer group were prepared using a simple and feasible synthetic method. These CGS exhibited an excellent surface activity with extremely low critical micelle concentration (CMC) value (approximately 10 mol/L), good performance in reducing surface tension (nearly 30 mN/m), and the ability of molecular self-assembly into different aggregate morphologies via adjusting the concentrations, which is attributed to the introduction of diphenyl ketone and carboxylic acid ammonium salt in the molecular structure. Moreover, the surface activity and self-assembly ability of CGS were further optimized by tuning the length of the tail chain. These excellent properties imply that CGS can be a soft template to prepare nanomaterials, especially in morphology-controllable synthesis. By adjusting the concentration of one of CGS (C-Φ-C), nano-LaO particles with diverse morphologies were obtained, including spherical shape, bead-chain shape, rod shape, velvet-antler shape, cedar shape, and bowknot shape. This work offers a vital insight into the rational design of template agents for the development of morphology-controllable nanomaterials.

A Tetraphenylethene Luminogen-Functionalized Gemini Surfactant for Simple and Controllable Fabrication of Hollow Mesoporous Silica Nanorods with Enhanced Fluorescence

“…Surfactants play a critical role in controlling the morphology, pore size, surface area, and dimension when preparing SNs by a template-directed method. − Among the various surfactants currently available, gemini surfactants, as a new class of surfactants containing one unique structure of two amphiphilic moieties connected with a spacer, have always been considered to be promising stabilizers and structure director agents for the preparation of various nanomaterials because of their better interfacial properties, miscellaneous aggregate morphologies, charged head groups, and lower critical micelle concentrations (CMCs). − In our previous work, the improved gemini surfactant C 16 –TPE–C 16 with a tetraphenylethene (TPE) luminogen-functionalized spacer, together with conventional CTAB, was successfully employed to prepare hollow AIE-MSNs . Although the obtained hollow AIE-MSNs exhibit less uniform morphologies, small mesopores of 2.8 nm, and unfavorable weakening of the fluorescent intensity after the removal of CTAB, they inspired us to pursue more suitable gemini surfactants to improve their structures and properties.…”