Unveiling the molecular interactions and antimicrobial activity of cetyl pyridinium bromide in ternary systems with short tetraalkylammonium bromide salts.

Physicochemical properties of a surfactant cetyl pyridinium bromide (CPB) (0.2-2 mmol kg) has been investigated by the addition of greener additives, that is, aqueous tetraalkylammonium bromide (TAAB) salts at different concentrations (0.005, 0.010 and 0.015 mol kg) by employing techniques viz: conductivity, fluorescence and UV-visible spectra. In contrast to spectroscopic analysis, which was conducted at room temperature (298.15 K), conductivity measurements were made at various temperatures (298.15, 303.15, 308, and 313.15 K). The obtained electrical conductivity data has been used to compute the critical micelle concentration (), which was also obtained from the UV-Visible and fluorescence methods. It is important to mention that the values obtained from these methods are found to be in good agreement. Various thermodynamic parameters ( and ) have been calculated using conductivity data, the interpretation of which reveals that the interactions between CPB and TAAB are found to be both electrostatic and hydrophobic, however, hydrophobic interactions are found to be dominant in the ternary system. Additionally, the impact of TAAB on the antimicrobial activities of CPB has been evaluated by measuring the zone of inhibition, which explains why the CPB-TAAB system is more effective against gram-positive bacteria () than gram-negative bacteria ( and ).Communicated by Ramaswamy H. Sarma.