Multifaceted insights into the molecular interactions of tetraalkylammonium-based quaternary ammonium salts with cetyltrimethylammonium bromide: unraveling structural, thermodynamic, and antibacterial effects

Abstract

Tetraalkylammonium-based quaternary ammonium ([R₄N⁺][DHP⁻]; R = Ethyl, Propyl, Butyl) salts were synthesized and subjected to in-depth analysis using NMR, FTIR and TG analysis. Subsequent investigations involved examining their impact on the aggregation patterns of the cationic surfactant Cetyltrimethylammonium bromide (CTAB) through the use of conductometry, fluorescence measurements, and UV-Visible spectroscopy. To gain a deeper understanding of the colloidal behavior of CTAB, the critical micelle concentration (cmc) of the surfactant was determined, both in the absence and presence of the quaternary ammonium salts. The observed variations in cmc values were attributed to structural changes within the surfactant-water mixture, made by the presence of these additives. In addition, the investigations include thermodynamic analysis, with a focus on studying the dependence of the cmc on temperature. The resultant thermodynamic parameters were utilized to elucidate the contributions of [R₄N⁺][DHP⁻], to the electrostatic and hydrophobic interactions involved in the formation of surfactant micellar aggregates. Furthermore, the study assessed the impact of [R₄N⁺][DHP⁻], on the surfactant’s antibacterial activity by quantifying the zone of inhibition, against both gram-positive and gram-negative bacterial species.

Graphical Abstract

Keywords:

• Tetraalkylammonium dihydrogen phosphate
• cationic surfactant
• micellar assembly
• thermodynamic parameters
• spectroscopic technique

Acknowledgements

Kiran Negi expresses gratitude to the University Grants Commission (UGC) in New Delhi for bestowing upon them the Junior Research Fellowship and Senior Research Fellowship, with reference to Ref. No. 33/(CSIR-UGC NET DEC. 2017). The generous financial assistance provided to the Department of Chemistry at HPU Shimla by UGC-SAP (DRS-I, II, and III) (No. F.540/3DRS/2010 and F.540/2/DRS-II/2018(SAP-1)) is also sincerely acknowledged. Additionally, the author extends their appreciation to the Department of Biotechnology at HPU Shimla for their invaluable assistance in conducting microbial research.

Disclosure statement

The authors state that they have no conflict of interest in this paper.

Additional information

Funding

The study was supported by university grant commission