Impact of hydrophobic tails of new phospho-zwitterionic surfactants on the structure, catalytic, and biological activities of AgNPs

Abstract

In this study, three anionic-cationic zwitterionic Gemini surfactants containing three different hydrophobic tails were prepared and their chemical structures were confirmed by Fourier transform infrared (FTIR) and 1H nuclear magnetic resonance (NMR) spectroscopy. The hydrophobic tail of the synthesized phospho-zwitterionic Gemini surfactants significantly affected the morphological structure of silver nanoparticles (AgNPs) prepared using a photochemical reduction method, which utilized sunlight as a surplus source of a reducing agent. Increasing the hydrophobic tail length of the surfactant promoted the formation of AgNPs exhibiting smaller particle sizes with a uniform structure. Moreover, as confirmed by ultraviolet-visible (UV-Vis) spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM), these AgNPs displayed higher stability in solution than those synthesized in the presence of Gemini surfactants with a shorter hydrocarbon tail. The impact of tail variation on the catalytic and antimicrobial performance of AgNPs was also examined. The synthesized surfactant/AgNP systems showed remarkable catalytic activity in the removal of certain toxic pollutants, including para-nitrophenol (p-NP) and methylene blue (MB), which were converted into less toxic compounds in the presence of NaBH4. Notably, the surfactant exhibiting the longest chain hydrocarbon, i.e., ZGH, produced AgNPs with the highest catalytic activity. This is the first study concerning the effects of the surfactant tail on the catalytic activity of NPs. The good biological performance of the synthesized Gemini surfactants against sulfate-reducing bacteria (SRB) demonstrated their potential for application in mitigating the growth of SRB during petroleum treatment processes. The combination of the synthesized surfactants with AgNPs significantly enhanced their biological performance.