Imidazolium-Based Ionic Liquid-Assisted Silver Nanoparticles and Their Antibacterial Activity: Experimental and Density Functional Theory Studies

• Published in: ACS omega 2023-11, Vol.8 (45), p.42976-42986
• Main Authors: Avirdi, Elham, Paumo, Hugues Kamdem, Kamdem, Boniface Pone, Singh, Madhur Babu, Kumari, Kamlesh, Katata-Seru, Lebogang, Bahadur, Indra
• Format: Article
• Language: English
• ISSN: 2470-1343; 2470-1343
• DOI: 10.1021/acsomega.3c06171

The exclusive properties of ionic liquids (ILs) offer various opportunities to develop advanced materials with appreciable therapeutic applications. Imidazolium-based ILs have been frequently used as reaction media and stabilizers for the development and surface functionalization of noble metal nanoparticles (NPs). This study reports the citrate-mediated reduction of silver ions in three different ILs, that is, 1-ethyl-3-methylimidazolium methyl sulfate ([EMIM]­[MS]), 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM]­[OTf]), and 1-butyl-3-methylimidazolium bis­(trifluoromethylsulfonyl)­imide ([BMIM]­[TFSI]). The resulting Ag-ILs NPs were characterized using many analytical techniques, including UV–visible spectroscopy, dynamic light scattering (DLS), scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction (XRD). DLS and XRD characterization revealed the negatively charged Ag-[EMIM]­[MS] NPs, Ag-[BMIM]­[OTf] NPs, and Ag-[BMIM]­[TFSI] NPs with mean hydrodynamic sizes of 278, 316, and 279 nm, respectively, and a face-centered cubic structure. These hybrid nanomaterials were subjected to in vitro antibacterial screening against three bacterial strains. The Ag-[BMIM]­[OTf] NPs exhibited significant activities against Escherichia coli, Staphylococcus aureus, and Enterobacter cloacae. The lowest inhibition concentration of 62.5 μg/mL was recorded against E. coli using Ag-[EMIM]­[MS] and Ag-[BMIM]­[OTf] NPs. Further, the density functional theory calculations carried out on the computed Ag-ILs in the gas phase and water showed relatively stable systems. Ag-[BMIM]­[TFSI] exhibited the lowest Gibbs free energy change of −34.41 kcal/mol. The value of the global electrophilicity index (ω = 0.1865 eV) for the Ag-[BMIM]­[OTf] correlated with its good antibacterial activity.