Reverse micelle-mediated synthesis of precision-controlled FeS nanospheres and their role in tailored FeS@PANI nanocomposites

Abstract

In this study, we introduce a novel approach that combines reverse micelle-mediated synthesis of FeS nanospheres with Pickering emulsion-templated polymerization, offering the unveiling of an unexplored strategy for precise control over the size and morphology of FeS@PANI nanocomposites. Unlike prior studies, which did not focus the role of Pickering emulsions in directing polymer growth, this present approach leverages emulsion interface stabilization and micellar confinement to regulate polymerization dynamics and composite architecture. Using reverse micelles composed of SPAN 80, 1-butanol, toluene, and FeS, five distinct water-to-surfactant (W₀) mole ratios (5, 10, 15, 20, and 30) were explored to precisely control the size and morphology of FeS nanospheres. TEM and FESEM analyses, along with PDI evaluations, demonstrate that increasing the water content (W₀ = 5 to 30) leads to a progressive increase in nanosphere size. At lower W₀ values, strong interactions between surfactants and water molecules slow down intermicellar exchange, resulting in the formation of small, monodisperse nanospheres with enhanced stability. These nanospheres readily accumulate at the toluene–water interface, effectively encapsulating the non-aqueous phase. Nanospheres synthesized at W₀ = 5 were then employed in Pickering emulsion formation, achieving maximum stability at 0.075 wt% FeS. In an exciting breakthrough, these stable Pickering emulsions facilitated the polymerization of aniline, leading to the successful formation of FeS@PANI nanocomposites, as confirmed by PXRD, UV, IR, and ¹H-NMR analyses. TEM and FESEM images reveal that FeS-stabilized emulsions control the size and morphology of polyaniline with precision. At 0.075 wt% FeS, spherical FeS@PANI nanocomposites of 40 nm were achieved, while the absence of FeS led to aggregated, distorted structures. This work highlights the transformative potential of FeS nanospheres, not only as emulsion stabilizers but also as key regulators of polymeric nanocomposite morphology, paving the way for advanced materials in diverse applications.