Synthesis of Schiff base-based cationic Gemini surfactants and evaluation of their effect on in-situ AgNPs preparation: Structure, catalytic, and biological activity study

Carcinogenic organic pollutants pose a threat to human health and the environment; therefore, appropriate solutions are required for their removal. In this study, three hybrid systems composed of surfactants and silver nanoparticles (AgNPs) were prepared based on three cationic Gemini surfactants exhibiting different hydrophobic tail lengths. The AgNPs were synthesized by a photochemical reduction method using sunlight as a surplus source of a reducing agent. The reaction was conducted in the presence of previously synthesized cationic Gemini surfactants as capping agents. It was found that surfactants with longer hydrophobic tails induced the formation of AgNPs displaying a smaller particle size, more uniform structure, and higher stability in solution compared to those prepared using surfactants with shorter hydrophobic tails. The results were confirmed by ultraviolet-visible (UV–Vis) spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS). The surface behavior of the amphiphilic surfactants and their hybrid systems with AgNPs was investigated at 25, 45, and 65 °C by performing surface tension measurements. It was determined that increasing the hydrophobic tail length and temperature resulted in increased micellization. Moreover, grafting the synthesized cationic Gemini surfactants with AgNPs enhanced the surface parameters. The synthesized surfactant–AgNPs hybrid systems showed good catalytic activity in converting carcinogenic p-nitrophenol (p-NP) into less toxic p-aminophenol (p-AP) in the presence of NaBH₄ as the reducing agent. The effect of the chain length variation on the catalytic performance of AgNPs was studied for the first time. Overall, combination of the synthesized cationic Gemini surfactants with AgNPs led to a significant enhancement in the biological performance.