Emulsion-stabilized silver nanoparticles vs. aqueous solutions: Effects on aggregation, elastic scattering, and nonlinear optical properties

Abstract

Silver nanoparticles are stabilized using the stable emulsion developed by mixing water, n-heptane, AOT surfactant, and Ag nanoparticles, and their nonlinear optical characteristics are studied. The plasmonic and nonlinear optical properties of emulsion-stabilized silver nanoparticles are unique due to their placement inside n-heptane and the accumulation of water nanodroplets around them. The optimal concentration and stability time of silver nanoparticles in the emulsion have been investigated to achieve the highest nonlinear absorption coefficient. By comparing the emulsion and aqueous solutions including NaCl, NaOH, L-alanine, and CTAB, a significant increase in nonlinear optical absorption along with elastic light scattering was observed in the emulsion sample, which is the result of increased aggregation of Ag nanoparticles along with a decrease in the dielectric constant of the medium. As a result, the emulsion has been introduced as a tool for modifying the optical properties of Ag nanoparticles. Nonlinear absorption mechanisms, including processes involving free carriers and reverse saturation absorption, are described. Emulsion-stabilized Ag nanoparticles can be used in photodynamic therapy. Since encapsulation enhances nonlinear optical quantities, it can be used as a solution for an effective strategy for the detection and removal of toxic pollutants such as metal ions.