Open AccessThe surface adsorption, aggregate structure and antibacterial activity of Gemini quaternary ammonium surfactants with carboxylic counterions
Author(s) -
Xiqin Zhou,
Sien Hu,
Yu Wang,
Sana Ullah,
Jun Hu,
Hongqin Liu,
Bin Xu
Publication year - 2019
Publication title -
royal society open science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 51
ISSN - 2054-5703
DOI - 10.1098/rsos.190378
Subject(s) - counterion , ammonium , adsorption , quaternary , aggregate (composite) , chemistry , environmental science , geology , materials science , ion , nanotechnology , organic chemistry , paleontology
A group of Gemini quaternary ammonium surfactants with the formula C n H 2 n +1 CONH(CH 2 ) 2 N + (CH 3 ) 2 (CH 2 ) 2 N + (CH 3 ) 2 (CH 2 ) 2 NHCOC n H 2 n +1 · 2Y ( n = 11, 13 and 15, Y = HCOO − , CH 3 COO − and CH 3 CHOHCOO − ) have been synthesized by a counterion conversion process and characterized by Fourier transform infrared spectroscopy and mass spectroscopy. Their adsorption and self-aggregation properties are investigated by surface tension, conductivity, dynamic light scattering and transmission electron microscopy (TEM) measurements. The results show that these surfactants reduce the surface tension of water to a minimum value of 26.51 mN m −1 at a concentration of 5.72 × 10 −2 mmol l −1 . Furthermore, the increased alkyl chain length of the carboxylic counterions leads to the increased critical micelle concentration, the decreased degree of counterion binding ( β ) and the decreased self-assembly tendency, but the minimum area per surfactant molecule ( A min ) adsorbed at the air–aqueous solution are similar. TEM images reveal that these surfactants self-assemble spontaneously into aggregates with vesicle or bilayer structures. It is also found that they have superior antibacterial activity at a concentration of 0.1 g l −1 . The high surface activity and high antibacterial activity of the Gemini quaternary ammonium salt surfactants containing different carboxylic counterions bring more possibilities for the application in the field of biomedicine.