Imidazolium-Based Ionic Liquid-Assisted Silver Nanoparticles and Their Antibacterial Activity: Experimental and Density Functional Theory Studies
Elham Avirdi, Hugues Kamdem Paumo, Boniface Pone Kamdem, Madhur Babu Singh, Kamlesh Kumari, Lebogang Katata‐Seru, Indra Bahadur
Abstract
High Resolution Image Download MS PowerPoint Slide 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.